Lect 7 & Lect 8
The Skeletal System: The Axial Skeleton & Appendicular Skeleton
1. Calcium Homeostasis & Bone Tissue
• Skeleton is a reservoir of Calcium & Phosphate
• Calcium ions involved with many body systems
– nerve & muscle cell function
– blood clotting
– enzyme function in many biochemical reactions
• Small changes in blood levels of Ca+2 can be deadly (plasma level maintained 9-11mg/100mL)
– cardiac arrest if too high
– respiratory arrest if too low
2. Hormonal Influences
• Parathyroid hormone (PTH) is secreted if Ca+2 levels falls
– PTH gene is turned on & more PTH is secreted from gland
– osteoclast activity increased, kidney retains Ca+2 and produces calcitriol
• Calcitonin hormone is secreted from parafollicular cells in thyroid if Ca+2 blood levels get too high
– inhibits osteoclast(+vitamin D) activity
– increases bone formation by osteoblasts
3. Describe about the skeletal system.
• Axial Skeleton头至胸部
– 80 bones
– lie along longitudinal axis
– skull, hyoid脖子, vertebrae, ribs排骨(12 pairs, 7 true ribs(link sternum), 3 false ribs(link 7th ribs), floating ribs not attach to sternum), sternum胸骨, ear ossicles , thorax
• Appendicular Skeleton四肢腰部下身
– 126 bones
– upper & lower limbs and pelvic & pectoral girdles
4. Describe about the skull.
• General Features
– The skull forms the large cranial cavity and smaller cavities, including the nasal cavity and orbits (eye sockets).
– Certain skull bones contain mucous membrane lined cavities called paranasal sinuses.
– The only moveable bone of the skull, other than the ear ossicles within the temporal bones, is the mandible.
– Immovable joints called sutures hold the skull bones together.
– Function:
• protect brain & house ear ossicles
• muscle attachment for jaw, neck & facial muscles
• protect delicate sense organs -- smell, taste, vision(eyes, ears, tongue)
• support entrances to digestive and respiratory systems
• 8 cranial bones & 14 facial bones
5. Parietal bone
6. Temporal bone
7. Occipital bone
8. Sphenoid bone
• Base of skull
• Pterygoid processes are attachment sites for jaw muscles
• Body is a cubelike portion holding sphenoid sinuses
Ethmoid bone
9. 14 facial bones
10. Vertebral Column
• The vertebral column, along with the sternum and ribs, makes up the trunk of the skeleton.
• Backbone or spine built of 26 vertebrae
• Five vertebral regions
– cervical vertebrae (7) in the neck
– thoracic vertebrae ( 12 ) in the thorax
– lumbar vertebrae ( 5 ) in the low back region
– sacrum/sacral vertebrae (5, fused as single)
– coccyx/coccygeal vertebrae (4, fused as single)
11. Intervertebral Discs
• Between adjacent vertebrae absorbs vertical shock
• Permit various movements of the vertebral column
• Fibrocartilagenous ring with a pulpy center
12. Thoracic Vertebrae
(T1-T12)
• Larger and stronger bodies
• Longer transverse & spinous processes
13. Lumbar Vertebrae
• There are 5 lumbar vertebrae
• Strongest & largest
• Short thick spinous & transverse processes
– back musculature
14. Sacrum
• Union of 5 vertebrae (S1 - S5) by age 30
• Sacral canal ends at sacral hiatus
• Auricular surface & sacral tuberosity of SI joint
15. Coccyx
• Union of 4 vertebrae (Co1 - Co4) by age 30
16. Thorax
•The term thorax refers to the entire chest.
•The skeletal part of the thorax (a bony cage) consists of the sternum, costal cartilages, ribs, and the bodies of the thoracic vertebrae
•The thoracic cage encloses and protects the organs in the thoracic and superior abdominal cavities. It also provides support for the bones of the shoulder girdle and upper limbs.
– Bony cage flattened from front to back
– Sternum (breastbone)
– Ribs
– Costal cartilages
– Bodies of the thoracic vertebrae.
17. Sternum
• The sternum is located on the anterior midline of the thoracic wall.
• It consists of three parts: manubrium, body, and xiphoid process
______
18. Describe about the Appendicular skeleton.
• The appendicular skeleton includes the bones of the upper and lower extremities and the shoulder and hip girdles.
• The appendicular skeleton functions primarily to facilitate movement.
• Pectoral girdle 臂膀
• Pelvic girdle 腰
• Upper limbs
• Lower limbs
19. Upper Extremity
• Joints
– shoulder (glenohumeral), elbow, wrist, metacarpophalangeal, interphalangeal
• Clavicle肩
• Scapula/shoulder bone
• Humerus
– Proximal End Part of shoulder joint
– Distal End Forms elbow joint with ulna and radius
• The ulna is located on the medial aspect of the forearm.
• The radius is located on the lateral aspect (thumb side) of the forearm
20. 8 Carpal Bones (wrist)
• The eight carpal bones, bound together by ligaments, comprise the wrist
• Proximal row - lat to med
– scaphoid - boat shaped
– lunate - moon shaped
– triquetrum - 3 corners
– pisiform - pea shaped
• Distal row - lateral to medial
– trapezium - four sided
– trapezoid - four sided
– capitate - large head
– hamate - hooked process
21. Metacarpals(palm) and Phalanges(finger)
• Five metacarpal bones are contained in the palm of each hand
• Each hand contains 14 phalanges, three in each finger and two in each thumb
• Metacarpals
– base, shaft, head
– knuckles (metacarpophalangeal joints)
• Phalanges
– 14 total: each is called phalanx
– proximal, middle, distal on each finger, except thumb
– base, shaft, head
22. Pelvic Girdle and Coxal/Hip Bones
• Pelvic girdle = two hipbones united at pubic symphysis
• Each hip bone = ilium上, pubis下, and ischium中
• Bony pelvis = 2 hip bones, sacrum and coccyx
23. Ilium
• The larger of the three components of the hip bone and articulates (fuses) with the ischium and pubis
• The ischium is the inferior, posterior portion of the hip bone
• The pubis is the anterior and inferior part of the hip bone
24. Pelvis
• Pelvis = sacrum, coccyx & 2 hip bones
• Pelvic axis = path of babies head
Female pelvis is larger, facilitate pregnancy and childbbirth
25. Lower Extremity
• Each lower extremity is composed of 30 bones, including the femur, tibia, fibula, tarsals, metatarsals, and phalanges
• Each lower limb = 30 bones
– femur and patella/knee cap within the thigh
– tibia厚 & fibula within the leg, distal end of femur
– 7 tarsal bones in the foot
– metatarsals within the forefoot
– phalanges in the toes
• Joints
– hip, knee, ankle
– proximal & distal tibiofibular
– metatarsophalangeal
26. Femur
The femur or thighbone is the largest, heaviest, and strongest bone of the body
27. Patella
• The patella or kneecap is a sesamoid bone located anterior to the knee joint
• It functions to increase the leverage of the tendon of the quadriceps femoris muscle, to maintain the position of the tendon when the knee is bent, and to protect the knee joint
28. Tibia
• medial & larger bone of leg
• weight-bearing bone
• lateral & medial condyles
• medial malleolus at ankle
29. Fibula
• not part of knee joint
• muscle attachment only
• lateral malleolus at ankle
30. Tarsals, Metatarsals, and Phalanges
• Seven tarsal bones constitute the ankle and share the weight associated with walking
• Five metatarsal bones are contained in the foot
• The arrangement of phalanges in the toes is the same as that described for the fingers and thumb above - fourteen bones in each foot
31. Tarsus
• Proximal region of foot (contains 7 tarsal bones)
• Talus = ankle bone (articulates with tibia & fibula)
• Calcaneus - heel bone
32. Metatarsus and Phalanges
• Metatarsus
– midregion of the foot
– each with base, shaft and head
• Phalanges
– distal portion of the foot
– similar in number and arrangement to the hand
– big toe is hallux
33. Arches of the Foot
• The bones of the foot are arranged in two non-rigid arches that enable the foot to support the weight of the body; provide an ideal distribution of body weight over the hard and soft tissues, and provide leverage while walking
• Flatfoot, clawfoot, and clubfoot are caused by decline, elevation, or rotation of the medial longitudinal arches.
• Function
– distribute body weight over foot
– yield & spring back when weight is lifted
• Longitudinal arches along each side of foot
• Transverse arch across midfoot region
– navicular, cuneiforms & bases of metatarsals
Lect 9
Joints
1. Describe about joints.
• A joint (articulation or arthrosis) is a point of contact between two or more bones, between cartilage and bones, or between teeth and bones.
• Joints hold bones together but permit movement
• Arthrology = study of joints
• Kinesiology = study of motion
Joints 360
2. Describe about classification of Joints
• Structural classification is based on the presence or absence of a synovial (joint) cavity and type of connecting tissue. Structurally, joints are classified as
– fibrous, cartilaginous, or synovial.
• Functional classification based upon movement:
– immovable = synarthrosis
– slightly movable = amphiarthrosis
– freely movable = diarthrosis
3. Fibrous Joints
• Lack a synovial cavity
• Bones held closely together by fibrous connective tissue
• Little or no movement (synarthroses or amphiarthroses)
• 3 structural types
– sutures
– syndesmoses
– gomphoses
4. Sutures
• Thin layer of dense fibrous connective tissue unites bones of the skull
• Immovable (synarthrosis)
5. Syndesmosis
• Fibrous joint
– bones united by ligament
• Slightly movable (amphiarthrosis)
• Anterior tibiofibular joint and Interosseous membrane
6. Gomphosis
• Ligament holds cone-shaped peg in bony socket
• Immovable ((synarthrosis)
• Teeth in alveolar processes
7. Cartilaginous Joints
• Lacks a synovial cavity
• Allows little or no movement
• Bones tightly connected by fibrocartilage or hyaline cartilage
• 2 types
– synchondroses
– symphyses
8. Synchondrosis
• Connecting material is hyaline cartilage
• Immovable (synarthrosis)
• Epiphyseal plate or joints between ribs and sternum
9. Symphysis
• Fibrocartilage is connecting material
• Slightly movable (amphiarthroses)
• Intervertebral discs and pubic symphysis
10. Synovial Joints
• Synovial cavity separates articulating bones
• Freely moveable (diarthroses)
• Articular cartilage
– reduces friction
– absorbs shock
• Articular capsule
– surrounds joint
– thickenings in fibrous capsule called ligaments
• Synovial membrane
– inner lining of capsule
Example of Synovial Joint
• Joint space is synovial joint cavity
• Articular cartilage covering ends of bones
• Articular capsule
11. Types of synovial joints
Plantar Joint
• Plantar joints permit mainly side-to-side and back-and- forth gliding movements.
• Rotation prevented by ligaments
• Examples
– intercarpal or intertarsal joints
– vertebrocostal joints
Hinge Joint
• A hinge joint contains the convex surface of one bone fitting into a concave surface of another bone
• Movement is primarily flexion or extension in a single plane.
• Examples
– Knee, elbow, ankle, interphalangeal joints
Pivot Joint
• In a pivot joint, a round or pointed surface of one bone fits into a ring formed by another bone and a ligament
• Movement is rotational and monaxial.
• Examples
– Proximal radioulnar joint
• supination
• pronation
– Atlanto-axial joint
• turning head side to side “no”
Condyloid or Ellipsoidal Joint
• In an condyloid joint, an oval-shaped condyle of one bone fits into an elliptical cavity of another bone.
• Movements are flexion-extension, abduction-adduction, and circumduction.
• Examples
– wrist and metacarpophalangeal joints for digits 2 to 5
Saddle Joint
• A saddle joint contains one bone whose articular surface is saddle- shaped and another bone whose articular surface is shaped like a rider sitting in the saddle.
• Movements are flexion-extension, abduction-adduction, and circumduction
• Example
– trapezium of carpus and metacarpal of the thumb
Ball and Socket Joint
• In a ball-and-socket joint, the ball-shaped surface of one bone fits into the cuplike depression of another.
• Movements are flexion- extension, abduction- adduction, rotation, and circumduction.
• Examples (only two!)
– shoulder joint
– hip joint
Fixed joint
• skull
Sliding joint
12. Types of movement at synovial joints
Gliding Movements
• Gliding movements occur when relatively flat bone surfaces move back and forth and from side to side with respect to one another (Figure 9.4).
• In gliding joints there is no significant alteration of the angle between the bones.
• Gliding movements occur at plantar joints.
Angular Movements
• In angular movements there is an increase or a decrease in the angle between articulating bones.
– Flexion results in a decrease in the angle between articulating bones (Figure 9.5).
– Extension results in an increase in the angle between articulating bones (Figure 9.5).
– Hyperextension is a continuation of extension beyond the anatomical position and is usually prevented by the arrangement of ligaments and the anatomical alignment of bones (Figures 9.5a, b, d, e).
Flexion上提(decrease angle), Extension下伸垂直(increase angle) & Hyperextension往下后方
Flex(contract)≠Flexion
Abduction, Adduction, and Circumduction
• Abduction refers to the movement of a bone away from the midline (Figure 9.6a-c). 上提，展开，往中外
Radial deviation=wrist abduction
Ulnar deviation=wrist adduction
• Adduction refers to the movement of a bone toward the midline (Figure 9.6d). 下伸，合上，往中近
• Circumduction refers to movement of the distal end of a part of the body in a circle (Figure 9.7). 转圈
• In rotation, a bone revolves around its own longitudinal axis
Circumduction
• Movement of a distal end of a body part in a circle
• Combination of flexion, extension, adduction and abduction
• Occurs at ball and socket, saddle and condyloid joints
Rotation
• Bone revolves around its own longitudinal axis
– medial/internal rotation is turning of anterior surface in towards the midline 往外
– lateral/external rotation is turning of anterior surface away from the midline 往內
• At ball & socket and pivot type joints.
Pivot and ball-and-socket joints permit rotation.
• If the anterior surface of a bone of the limb is turned toward the midline, medial rotation occurs. If the anterior surface of a bone of the limb is turned away from the midline, lateral rotation occurs (Figure 9.8 b&c).
13. Special Movements of Mandible
• Elevation = upward movement of a part of the body/raise jaw 下巴向上
• Depression = downward movement/lower jaw下巴向下
• Protraction = a movement of a part of the body anteriorly in the transverse plane 下巴向前
• Retraction = a movement of a protracted part back to the anatomical position 下巴向内
14. Special Hand & Foot Movements
• Inversion
• Eversion
• Dorsiflexion
• Plantarflexion
• Pronation
• Supination
Special Movements
• Inversion is movement of the soles medially at the intertarsal joints so that they face away from each other 脚掌往内大腿侧
• Eversion is a movement of the soles laterally at the intertarsal joints so that they face away from each other 脚掌往外
• Dorsiflexion refers to bending of the foot at the ankle in the direction of the superior surface 脚掌向上
• Plantar flexion involves bending of the foot at the ankle joint in the direction of the plantar surface 脚掌向下
• Supination is a movement of the forearm at the proximal and distal radioulnar joints in which the palm is turned anteriorly or superiorly (Figure 9.9h). 手掌向外
• Pronation is a movement of the forearm at the proximal and distal radioulnar joints in which the distal end of the radius crosses over the distal end of the ulna and the palm is turned posteriorly or inferiorly (Figure 9.9h). 手掌向内
• Opposition is the movement of the thumb at the carpometacarpal joint in which the thumb moves across the palm to touch the tips of the finger on the same hand. 拇指和其他指合上
15. Types of injuries of joints
Dislocation
Arthritis
Osteoporosis
Strain, sprain, fracture
Lect 10 & 11
Muscle tissue
1. Muscle Tissue
• Motion results from alternating contraction (shortening) and relaxation of muscles; the skeletal system provides leverage and a supportive framework for this movement.
• The scientific study of muscles is known as myology.
• Alternating contraction and relaxation of cells.
• Chemical energy changed into mechanical energy.
2. 3 Types of Muscle Tissue
• Skeletal muscle
– attaches to bone, skin or fascia
– striated with light & dark bands visible with scope
– voluntary control of contraction & relaxation
• Cardiac muscle
– tissue forms the wall of the heart.
– striated in appearance
– involuntary control
– autorhythmic because of built in pacemaker
resistant to fatigue
• Smooth muscle
– tissue is located in viscera.
– attached to hair follicles in skin
– in walls of hollow organs -- blood vessels & GI
– nonstriated in appearance
– involuntary
#involuntary muscle-blood vessel
3. Functions of muscle tissue
• Producing body movements
• Stabilizing body positions
• Regulating organ volumes
– bands of smooth muscle called sphincters
• Movement of substances within the body (storing&moving)
– blood, lymph, urine, air, food and fluids, sperm
particularly true for cardiac & smooth muscle
• Producing heat
– involuntary contractions of skeletal muscle (shivering)
thermogenesis
4. Properties of muscle tissue
• Excitability
– respond to chemicals released from nerve cells
ability to respond to certain stimuli by producing electrical signals (action potentials-AP)
property of nerve cells as well
electrical & chemical
• Conductivity
– ability to propagate electrical signals over membrane
• Contractility
– ability to shorten and generate force
contracts when stimulated by an AP
generates tension while pulling on attachment points
• Extensibility
– ability to be stretched without damaging the tissue
• Elasticity
– ability to return to original shape after being stretched
5. SKELETAL MUSCLE TISSUE
Connective Tissue Components
• Each skeletal muscle is a separate organ composed of cells called fibers. Connective tissue components of the muscle include
- epimysium = surrounds the whole muscle/ outer layer
- perimysium = surrounds bundles (fascicles)
- endomysium = separates individual muscle cells/ deepest
• All these connective tissue layers extend beyond the muscle belly to form the tendon
skeletal muscle=striated muscle
Nerve and Blood Supply
• Each skeletal muscle is supplied by a nerve, artery and two veins.
• Each motor neuron supplies multiple muscle cells (neuromuscular junction)
• Each muscle cell is supplied by one motor neuron terminal branch and is in contact with one or two capillaries.
– nerve fibers & capillaries are found in the endomysium between individual cells
Muscle Fiber or Myofibers
• Muscle cells are long, cylindrical & multinucleated
• Sarcolemma = muscle cell membrane
• Sarcoplasm filled with tiny threads called myofibrils & myoglobin (red-colored, oxygen-binding protein) O2 for ATP production.
Sarcolemma, T Tubules, and Sarcoplasm
• Skeletal muscle consists of fibers (cells) covered by a sarcolemma.
– The fibers contain T tubules and sarcoplasm
– T tubules are tiny invaginations of the sarcolemma that quickly spread the muscle action potential to all parts of the muscle fiber.
• Sarcoplasm is the muscle cell cytoplasm and contains a large amount of glycogen for energy production and myoglobin for oxygen storage.
Transverse Tubules
• T (transverse) tubules are invaginations of the sarcolemma into the center of the cell
– filled with extracellular fluid
– carry muscle action potentials down into cell
• Mitochondria lie in rows throughout the cell
– near the muscle proteins that use ATP during contraction
Myofibrils & Myofilaments
• Each fiber contains myofibrils that consist of thin and thick filaments (myofilaments)
• Muscle fibers are filled with threads called myofibrils separated by SR (sarcoplasmic reticulum)
• The sarcoplasmic reticulum encircles each myofibril. It is similar to smooth endoplasmic reticulum in nonmuscle cells and in the relaxed muscle stores calcium ions.
• Myofilaments (thick & thin filaments) are the contractile proteins of muscle
Sarcoplasmic Reticulum (SR)
• System of tubular sacs similar to smooth ER in nonmuscle cells
• Stores Ca+2 in a relaxed muscle
• Release of Ca+2 triggers muscle contraction
Filaments and the Sarcomere
• Thick and thin filaments overlap each other in a pattern that creates striations (light I bands and dark A bands)
• The I band region contains only thin filaments.
• They are arranged in compartments called sarcomeres, separated by Z discs.
• In the overlap region, six thin filaments surround each thick filament
Thick & Thin Myofilaments
• shows the relationships of the zones, bands, and lines as seen in a transmission electron micrograph.
• Supporting proteins (M line, titin and Z disc help anchor the thick and thin filaments in place)
6. Protein of muscle
• Myofibrils are built of 3 kinds of protein
– contractile proteins
• myosin and actin (@troponin)
– regulatory proteins which turn contraction on & off
• troponin and tropomyosin (wire/double stranded like)
– structural proteins which provide proper alignment, elasticity and extensibility
• titin, myomesin, nebulin and dystrophin
A. Myosin
• Thick filaments are composed of myosin
– each molecule resembles two golf clubs twisted together
– myosin heads (cross bridges) extend toward the thin filaments
• Held in place by the M line proteins.
B. Actin
• Thin filaments are made of actin, troponin, & tropomyosin
• The myosin-binding site on each actin molecule is covered by tropomyosin in relaxed muscle
• The thin filaments are held in place by Z lines. From one Z line to the next is a sarcomere.
Structural Proteins
• Structural proteins keep the thick and thin filaments in the proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix.
– Titin helps a sarcomere return to its resting length after a muscle has contracted or been stretched.
– Myomesin forms the M line.
– Nebulin helps maintain alignment of the thin filaments in the sarcomere.
– Dystrophin reinforces the sarcolemma and helps transmit the tension
generated by the sarcomeres to the tendons.
C. Titin
• Titan anchors thick filament to the M line and the Z disc.
• The portion of the molecule between the Z disc and the end of the thick filament can stretch to 4 times its resting length and spring back unharmed.
• Role in recovery of the muscle from being stretched.
Structural Proteins
• The M line (myomesin) connects to titin and adjacent thick filaments.
• Nebulin, an inelastic protein helps align the thin filaments.
• Dystrophin links thin filaments to sarcolemma and transmits the tension generated to the tendon.
7. Sliding Filament Mechanism Of Contraction
• Myosin cross bridges pull on thin filaments
• Thin filaments slide inward
• Z Discs come toward each other
• Sarcomeres shorten.The muscle fiber shortens. The muscle shortens
• Notice :Thick & thin filaments do not change in length
When a muscle contracts, the actin is pulled along myosin toward the center of the sarcomere until the actin and myosin filaments are completely overlapped. In other words, for a muscle cell to contract, the sarcomere must shorten. However, thick and thin filaments—the components of sarcomeres—do not shorten. Instead, they slide by one another, causing the sarcomere to shorten while the filaments remain the same length. The sliding filament theory of muscle contraction was developed to fit the differences observed in the named bands on the sarcomere at different degrees of muscle contraction and relaxation. The mechanism of contraction is the binding of myosin to actin, forming cross-bridges that generate filament movement.
When a sarcomere shortens, some regions shorten whereas others stay the same length. A sarcomere is defined as the distance between two consecutive Z discs or Z lines; when a muscle contracts, the distance between the Z discs is reduced. The H zone—the central region of the A zone—contains only thick filaments (myosin) and is shortened during contraction. The H zone becomes smaller and smaller due to the increasing overlap of actin and myosin filaments, and the muscle shortens. Thus when the muscle is fully contracted, the H zone is no longer visible. The I band contains only thin filaments and also shortens. The A band does not shorten—it remains the same length—but A bands of different sarcomeres move closer together during contraction, eventually disappearing. Thin filaments are pulled by the thick filaments toward the center of the sarcomere until the Z discs approach the thick filaments. The zone of overlap, in which thin filaments and thick filaments occupy the same area, increases as the thin filaments move inward.
_______
1. Contraction
• 1. Nerve impulse reaches an axon terminal
• 2.synaptic vesicles release acetylcholine (ACh)
• 3. ACh diffuses to receptors on the sarcolemma
• 4. stimulus provided by binding of ACh to the sarcolemma;
• 5. Na+ channels open and Na+ rushes into the cell
• 6. resulting action potential travels along sarcolemma and into T tubules, triggering release of calcium ions from SR;
• 7. calcium ions bind to troponin; resulting shape change causes myosin binding site to be exposed;
• 8. myosin (ADP and phosphate molecule) heads bind to actin, and swivel (power stroke), pulling Z discs closer together, shortening myofiber.-the contraction cycle begins
Contraction Cycle
• Repeating sequence of events that cause the thick & thin filaments to move past each other.
• 4 steps to contraction cycle
– ATP hydrolysis
– attachment of myosin to actin to form crossbridges
– power stroke
– detachment of myosin from actin
• Cycle keeps repeating as long as there is ATP available & there is a high Ca+2 level near the filaments.
https://www.youtube.com/watch?v=S5uFaqpEPMI
2. ATP and Myosin
• Myosin heads are activated by ATP
• Activated heads attach to actin & pull (power stroke)
• ADP is released. (ATP released P & ADP & energy)
• Thin filaments slide past the thick filaments
• ATP binds to myosin head & detaches it from actin
• All of these steps repeat over and over
– if ATP is available &
– Ca+ level near the troponin-tropomyosin complex is high
3. Excitation - Contraction Coupling
• All the steps that occur from the muscle action potential reaching the T tubule to contraction of the muscle fiber.
4. Relaxation
• Acetylcholinesterase (AChE) breaks down ACh within the synaptic cleft
• Muscle action potential ceases
• Ca+2 release channels close
• Active transport pumps Ca2+ back into storage in the sarcoplasmic reticulum
• Calcium-binding protein (calsequestrin) helps hold Ca+2 in SR (Ca+2 concentration 10,000 times higher than in cytosol)
• Tropomyosin-troponin complex recovers binding site on the actin
5. SUMMARY
• Nerve ending
• Neurotransmittor
• Muscle membrane
• Stored Ca+2
• ATP
• Muscle proteins
https://www.youtube.com/results?search_query=How+Does+relaxation+muscle+Begin+animation
A. Nerve impulse arrives at axon terminal of motor neuron and triggers release of acetylcholine (ACh).
B. ACh diffuses across synaptic cleft, binds to it's receptors in the motor end plate, and triggers a muscle action potential.
C. Acetylcholinesterase in synaptic cleft destroy ACh so the other muscle action potential does not arise unless more ACh is released from motor neuron.
D. Muscle AP travelling along transverse tubule open Ca2+ release channels in the sarcoplasmic reticulum (SR) membrane, which allows Ca2+ to flood into the sarcoplasm.
E. Ca2+ binds to troponin on the thin filament, exposing the binding sites of myosin.
F. Contraction: power strokes use ATP, myosin heads bind to actin, swivel and release, thin filaments are pulled toward the center of sacromere.
G. Ca2+ release channels in SR close and Ca2+ active transport pumps use ATP to restore low level of Ca2+ in sacroplasm.
H. Tropinin-tropomyosin complex slides back into position where it blocks the myosin binding sites on actin.
I. Muscle relaxes.
6. Neuromuscular Junction (NMJ) or Synapse
• NMJ = myoneural junction
– end of axon nears the surface of a muscle fiber at its motor end plate region (remain separated by synaptic cleft or gap)
7. Anatomy of Cardiac Muscle
https://www.youtube.com/watch?v=IMkHo11reWg
• Striated , short, quadrangular-shaped, branching fibers
• Single centrally located nucleus/unicellular
• Cells connected by intercalated discs with gap junctions
• Same arrangement of thick & thin filaments as skeletal
8. CARDIAC MUSCLE TISSUE - Overview
• Cardiac muscle tissue is found only in the heart wall Its fibers are arranged similarly to skeletal muscle fibers.
– Cardiac muscle fibers connect to adjacent fibers by intercalated discs which contain desmosomes and gap junctions
– Cardiac muscle contractions last longer than the skeletal muscle twitch due to the prolonged delivery of calcium ions from the sarcoplasmic reticulum and the extracellular fluid.
– Cardiac muscle fibers contract when stimulated by their own autorhythmic fibers.
• This continuous, rhythmic activity is a major physiological difference between cardiac and skeletal muscle tissue
9. Appearance of Cardiac Muscle
• Striated muscle containing thick & thin filaments
• T tubules located at Z discs & less SR
10. Physiology of Cardiac Muscle
• Autorhythmic cells
– contract without stimulation
• Contracts 75 times per min & needs lots of O2
• Larger mitochondria generate ATP aerobically
• Extended contraction is possible due to slow Ca+2 delivery
– Ca+2 channels to the extracellular fluid stay open
• involuntary
11. SMOOTH MUSCLE
• Smooth muscle tissue is nonstriated and involuntary and is classified into two types: visceral (single unit) smooth muscle and multiunit smooth muscle
– Visceral (single unit) smooth muscle is found in the walls of hollow viscera and small blood vessels; the fibers are arranged in a network and function as a “single unit.”
– Multiunit smooth muscle is found in large blood vessels, large airways, arrector pili muscles, and the iris of the eye. The fibers operate singly rather than as a unit.
12. Two Types of Smooth Muscle
• Visceral (single-unit)
– in the walls of hollow viscera & small BV
– autorhythmic
• Multiunit
– individual fibers with own motor neuron ending
– found in large arteries, large airways, arrector pili muscles,iris & ciliary body
13. Microscopic Anatomy of Smooth Muscle
• Sarcoplasm of smooth muscle fibers contains both thick and thin filaments which are not organized into sarcomeres.
• Smooth muscle fibers contain intermediate filaments which are attached to dense bodies.
• Small, involuntary muscle cell -- tapering at ends
• Single, oval, centrally located nucleus
• Lack T tubules & have little SR for Ca+2 storage
• Thick & thin myofilaments not orderly arranged so lacks sarcomeres
• Sliding of thick & thin filaments generates tension
• Transferred to intermediate filaments & dense bodies attached to sarcolemma
• Muscle fiber contracts and twists into a helix as it shortens -- relaxes by untwisting
14. Physiology of Smooth Muscle
• Contraction starts slowly & lasts longer
– no transverse tubules & very little SR
– Ca+2 must flows in from outside
• In smooth muscle, the regulator protein that binds calcium ions in the cytosol is calmodulin (in place of the role of troponin in striated muscle);
– calmodulin activates the enzyme myosin light chain kinase, which facilitates myosin-actin binding and allows contraction to occur at a relatively slow rate.
13. Differentiate between skeletal muscle tissue and smooth muscle tissue.
https://www.youtube.com/watch?v=UNyKlwO23w4
Lect 12
Nervous tissue
1. Nervous system
The nervous system, along with the endocrine system, helps to keep controlled conditions within limits that maintain health and helps to maintain homeostasis.
The nervous system is responsible for all our behaviors, memories, and movements.
The branch of medical science that deals with the normal functioning and disorders of the nervous system is called neurology.
2. Structures of the Nervous System
CNS: Brain, spinal cord
PNS: Cranial nerves, spinal nerves, ganglia, enteric plexuses and sensory receptors
12 pairs of cranial nerves emerge from the base of the brain through foramina of the skull. Some sensory most mixed.
31 pairs of spinal nerves. All mixed.
The spinal cord connects to the brain through the foramen magnum of the skull and is encircled by the bones of the vertebral column.
Ganglia, located outside the brain and spinal cord, are small masses of nervous tissue, containing primarily cell bodies of neurons.
Enteric plexuses help regulate the digestive system.
Sensory receptors are either parts of neurons or external environment.
3. Functions of Nervous System
• The sensory function of the nervous system is to sense changes in the internal and external environment through sensory receptors.
– sensing changes with sensory receptors
~ fullness of stomach or sun on your face
• The integrative function is to analyze the sensory information, store some aspects, and make decisions regarding appropriate behaviors.
– interpreting and remembering those changes
• The motor function is to respond to stimuli by initiating action.
– reacting to those changes with effectors
~ muscular contractions
~ glandular secretions
• Nervous systems works with the endocrine system to maintain homeostasis.
• communicates with the body via action potentials.
• is responsible for thoughts and behaviors.
• initiates voluntary movements.
• helps to keep controlled conditions within limits that maintain health
4. Nervous System Divisions
• Central nervous system (CNS)
– consists of the brain and spinal cord
• Peripheral nervous system (PNS)
– consists of cranial and spinal nerves that contain both sensory and motor fibers receptors, enteric plexuses receptors
– connects CNS to muscles, glands & all sensory receptors
5. Subdivisions of the PNS
• Somatic (voluntary) nervous system (SNS)
– neurons from cutaneous and special sensory receptors to the CNS
– motor neurons to skeletal muscle tissue
• Autonomic (involuntary) nervous systems
– sensory neurons from visceral organs to CNS
– motor neurons to smooth & cardiac muscle and glands
• sympathetic division (speeds up heart rate)
• parasympathetic division (slow down heart rate)
• Enteric nervous system (ENS)
– involuntary sensory & motor neurons control GI tract
– neurons function independently of ANS & CNS
6. Neurons
• Functional unit of nervous system
• Have capacity to produce action potentials
– electrical excitability
7. Dendrites
• The dendrites are the receiving or input portions of a neuron.
• The axon conducts nerve impulses from the neuron to the dendrites or cell body of another neuron or to an effector organ of the body (muscle or gland).
• Typically short, highly branched & unmyelinated
8. Axons
• Conduct impulses away from cell body
• Long, thin cylindrical process of cell
• Arises at axon hillock
• Axonal transport system moves substances
– slow axonal flow
~ movement in one direction only -- away from cell body
– fast axonal flow
~ moves organelles & materials along surface of microtubules
9. Functional Classification of Neurons
• Sensory (afferent) neurons
– transport sensory information from skin, muscles,
joints, sense organs & viscera to CNS
• Motor (efferent) neurons
– send motor nerve impulses to muscles & glands
• Interneurons (association) neurons
– connect sensory to motor neurons
10. Neuroglial Cells
• Half of the volume of the CNS
• Smaller cells than neurons
• Cells can divide
– rapid mitosis in tumor formation (gliomas)
• 4 cell types in CNS
– astrocytes, oligodendrocytes, microglia & ependymal
• 2 cell types in PNS
– schwann and satellite cells
11. Astrocytes
• Star-shaped cells
• Form blood-brain barrier by covering blood capillaries
• Metabolize neurotransmitters
• Regulate K+ balance
12. Microglia
• Small cells found near blood vessels
• Phagocytic role -- clear away dead cells
13. Ependymal cells
• Form epithelial membrane lining cerebral cavities & central canal
• Produce cerebrospinal fluid (CSF)
14. Satellite Cells
• Flat cells surrounding neuronal cell bodies in peripheral ganglia
• Support neurons in the PNS ganglia
15. Oligodendrocytes
• Most common glial cell type
• Each forms myelin sheath around more than one axons in CNS
• Analogous to Schwann cells of PNS
16. Myelination
• A multilayered lipid and protein covering called the myelin sheath and produced by Schwann cells and oligodendrocytes surrounds the axons of most neurons
• The sheath electrically insulates the axon and increases the speed of nerve impulse conduction.
17. Schwann Cell
• Cells encircling PNS axons
• Each cell produces part of the myelin sheath surrounding an axon in the PNS
18. Gray and White Matter
• White matter = myelinated processes (white in color)
• Gray matter = nerve cell bodies, dendrites, axon terminals, bundles of unmyelinated axons and neuroglia (gray color)
– In the spinal cord = gray matter forms an H-shaped inner core surrounded by white matter
– In the brain = a thin outer shell of gray matter covers the surface & is found in clusters called nuclei inside the CNS
• A nucleus is a mass of nerve cell bodies and dendrites inside
19. Graded Potentials
• Small deviations from resting potential of -70mV
– hyperpolarization = membrane has become more negative
– depolarization = membrane has become more positive
• The signals are graded, meaning they vary in amplitude (size), depending on the strength of the stimulus and localized.
• Graded potentials occur most often in the dendrites and cell body of a neuron.
20. How do Graded Potentials Arise?
• Source of stimuli
– mechanical stimulation of membranes with mechanical gated ion channels (pressure)
– chemical stimulation of membranes with ligand gated ion channels (neurotransmitter)
• Graded/postsynaptic/receptor or generator potential
– ions flow through ion channels and change membrane potential locally
– amount of change varies with strength of stimuli
• Flow of current (ions) is local change only
21. Generation of an Action Potential
• An action potential (AP) or impulse is a sequence of rapidly occurring events that decrease and eventually reverse the membrane potential (depolarization) and then restore it to the resting state (repolarization).
– During an action potential, voltage-gated Na + and K+ channels open in sequence.
• According to the all-or-none principle, if a stimulus reaches threshold, the action potential is always the same.
– A stronger stimulus will not cause a larger impulse.
22. Action Potential
• Series of rapidly occurring events that change and then restore the membrane potential of a cell to its resting state
• Ion channels open, Na+ rushes in (depolarization), K+ rushes out (repolarization)
• All-or-none principal = with stimulation, either happens one specific way or not at all (lasts 1/1000 of a second)
• Travels (spreads) over surface of cell without dying out
https://courses.lumenlearning.com/boundless-ap/chapter/neurophysiology/
23. Depolarizing Phase of Action Potential
• Chemical or mechanical stimulus caused a graded potential to reach at least (-55mV or threshold)
• Voltage-gated Na+ channels open & Na+ rushes into cell
– in resting membrane, inactivation gate of sodium channel is open & activation gate is closed (Na+ can not get in)
– when threshold (-55mV) is reached, both open & Na+ enters
– inactivation gate closes again in few ten-thousandths of second
– only a total of 20,000 Na+ actually enter the cell, but they change the membrane potential considerably(up to +30mV)
• Positive feedback process
24. Repolarizing Phase of Action Potential
#undershoot phase (Na+&K+ pump)
• When threshold potential of -55mV is reached, voltage-gated K+ channels open
• K+ channel opening is much slower than Na+ channel opening which caused depolarization
• When K+ channels finally do open, the Na+ channels have already closed (Na+ inflow stops)
• K+ outflow returns membrane potential to -70mV
• If enough K+ leaves the cell, it will reach a -90mV membrane potential and enter the after-hyperpolarizing
• K+ channels close and the membrane potential returns to the resting potential of -70mV
25. Refractory Period of Action Potential
• Period of time during which neuron can not generate another action potential
• Absolute refractory period
– even very strong stimulus will not begin another AP
– inactivated Na+ channels must return to the resting state before they can be reopened
– large fibers have absolute refractory period of 0.4 msec and up to 1000 impulses per second are possible
• Relative refractory period
– a suprathreshold stimulus will be able to start an AP
– K+ channels are still open, but Na+ channels have closed
26. Propagation of Action Potential
• An action potential spreads (propagates) over the surface of the axon membrane
– as Na+ flows into the cell during depolarization, the
voltage of adjacent areas is effected and their voltage- gated Na+ channels open
– self-propagating along the membrane
• The traveling action potential is called a nerve impulse
27. Action Potentials in Nerve and Muscle
• Entire muscle cell membrane versus only the axon of the neuron is involved
• Resting membrane potential
– nerve is -70mV
– skeletal & cardiac muscle is closer to -90mV
• Duration
– nerve impulse is 1/2 to 2 msec
– muscle action potential lasts 1-5 msec for skeletal & 10-300msec for cardiac & smooth
• Fastest nerve conduction velocity is 18 times faster than velocity over skeletal muscle fiber
28. Signal Transmission at Synapses
https://www.youtube.com/watch?v=RcU9W9AOfic
• A synapse is the functional junction between one neuron and another or between a neuron and an effector such as a muscle or gland
• 2 Types of synapses
– electrical
• ionic current spreads to next cell through gap junctions
• faster, two-way transmission & capable of synchronizing groups of neurons
– chemical
• one-way information transfer from a presynaptic neuron to a postsynaptic neuron
– axodendritic -- from axon to dendrite
– axosomatic -- from axon to cell body
– axoaxonic -- from axon to axon
29. Chemical Synapses
• Action potential reaches end bulb and voltage-gated Ca+ 2 channels open
• Ca+2 flows inward triggering release of neurotransmitter
• Neurotransmitter crosses synaptic cleft & binding to ligand-gated receptors
– the more neurotransmitter released (exocytosis) the greater the change in potential of the postsynaptic cell
• Synaptic delay is 0.5 msec
• One-way information transfer
https://www.youtube.com/watch?v=mItV4rC57kM
30. Removal of Neurotransmitter
• Diffusion
– move down concentration gradient
• Enzymatic degradation
– acetylcholinesterase-acetyl grp+choline
• Uptake by neurons or glia cells
– neurotransmitter transporters
– Prozac = serotonin reuptake inhibitor
#neurotransmitter--neonicotinoid--nicotine
31. SUMMARY
action potential
the phases of an action potential, appropriate ion movements the mechanisms by which such movements occur.
i. Depolarization:
-graded potential brings the membrane to threshold
-voltage-gated sodium ion channels open;
-sodium rushes in by diffusion
-creates positive feedback situation;
-sodium inactivation gates close just after activation gates open
ii. Repolarization:
-voltage-gated potassium ion channels open as soon as sodium ions channels are closing;
-potassium diffuses out to restore resting potential;
-voltage-gated sodium ion channels revert to resting state
iii. After-hyperpolarization:
- may occur as large outflow of potassium passes normal resting potential
Lect 13 & 14
The Brain and Cranial Nerves
1. INTRODUCTION CRANIAL NERVES
•The spinal cord and spinal nerves mediate reactions to environmental changes.
•The spinal cord is protected by two connective tissue coverings, the meninges and vertebra, and a cushion of cerebrospinal fluid.
•The spinal cord has several functions.
–It processes reflexes.
–It is a conduction pathway for sensory and motor nerve impulses.
–The size of the vertebral canal varies in different regions of the vertebral column and affects spinal cord injuries.
–Together with brain forms the CNS
–integration (summation of inhibitory and excitatory) nerve impulses
–highway for upward and downward travel of sensory and motor information
2. Spinal Nerves
•31 Pairs of spinal nerves
•Named & numbered by the cord
•level of their origin
–8 pairs of cervical nerves (C1 to C8)
–12 pairs of thoracic nerves (T1 to T12) –5 pairs of lumbar nerves (L1 to L5)
–5 pairs of sacral nerves (S1 to S5)
–1 pair of coccygeal nerves
•Mixed sensory & motor nerves
3. White Matter and Gray Matter of the Spinal Cord
•The spinal cord has two principal functions.
•The white matter tracts are highways for nerve impulse conduction to and from the brain.
–The white matter is divided into columns.
–Each column contains distinct bundles of nerve axons that have a common origin or destination and carry similar information.
•The gray matter (butterfly form) receives and integrates incoming and outgoing information.
–The gray matter is divided into horns, which contain cell bodies of neurons.
4. SUMMARY
https://www.youtube.com/watch?v=K-P_BKOUFXs
https://www.youtube.com/watch?v=zxpb1-okVig
______
1. Brain
• Largest organ in the body at almost 3 lb.
• Brain functions in sensations, memory, emotions, decision making, behavior
The major parts of the brain are
• Cerebrum
• Diencephalon
– thalamus & hypothalamus
• Cerebellum
• Brainstem
– Medulla oblongata, pons & midbrain
2.Blood Supply to Brain
• Arterial blood supply is branches from circle of Willis on base of brain
• Vessels on surface of brain----penetrate tissue
• Uses 20% of our bodies oxygen & glucose needs
– blood flow to an area increases with activity in that area
– deprivation of O2 for 4 min does permanent injury
• at that time, lysosome release enzymes
• Blood-brain barrier (BBB)
– protects cells from some toxins and pathogens
• proteins & antibiotics can not pass but alcohol & anesthetics do
– tight junctions seal together epithelial cells, continuous basement membrane, astrocyte processes covering capillaries
endothelial cells, pericytes, astrocytes
3. Blood Flow and the Blood-Brain Barrier
• An interruption of blood flow for 1 or 2 minutes impairs neuronal function.
– A total deprivation of oxygen for 4 minutes causes permanent injury.
• Because carbohydrate storage in the brain is limited, the supply of glucose to the brain must be continuous.
– Glucose deficiency may produce mental confusion, dizziness, convulsions, and unconsciousness.
4. BBB
• A blood-brain barrier (BBB) protects brain cells from harmful substances and pathogens by serving as a selective barrier to prevent passage of many substances from the blood to the brain.
• An injury to the brain due to trauma, inflammation, or toxins causes a breakdown of the BBB, permitting the passage of normally restricted substances into brain tissue.
• The BBB may also prevent entry of drugs that could be used as therapy for brain cancer or other CNS disorders, so research is exploring ways to transport drugs past the BBB.
5.Protective Coverings of the Brain
• Bone, meninges & fluid
• Meninges same as around the spinal cord
– dura mater
– arachnoid mater
– pia mater
• Dura mater extensions
– falx cerebri
– tentorium cerebelli
– falx cerebelli
6. Cerebrospinal Fluid (CSF)
• Cerebrospinal fluid (CSF) is a clear, colorless liquid that protects the brain and spinal cord against chemical and physical injuries.
• Clear liquid containing glucose, proteins, & ions
• Functions
– mechanical protection
• floats brain & softens impact with bony walls
– chemical protection
• optimal ionic concentrations for action potentials
– circulation
• nutrients and waste products to and from bloodstream
Origin of CSF
• Choroid plexus = capillaries covered by ependymal cells
– 2 lateral ventricles, one within each cerebral hemisphere
– roof of 3rd ventricle
– fourth ventricle
THE BRAIN STEM
7. Medulla Oblongata
• Continuation of spinal cord
• Ascending sensory tracts
• Descending motor tracts
• Nuclei of 5 cranial nerves
• Cardiovascular center
– force & rate of heart beat
– diameter of blood vessels
• Respiratory center
– medullary rhythmicity area sets basic rhythm of breathing
• Information in & out of cerebellum
• Reflex centers for coughing, sneezing, swallowing etc.
8. XII = Hypoglossal Nerve
• Controls muscles of tongue during speech and swallowing
• Mixed, primarily motor
9. XI = Spinal Accessory Nerve
• Cranial portion
– arises medulla
• Spinal portion
– arises cervical spinal cord
10. X = Vagus Nerve
• Receives sensations from viscera
• Controls cardiac muscle and smooth muscle of the viscera
• Controls secretion of digestive fluids
11. IX = Glossopharyngeal Nerve
• Stylopharyngeus m. (lifts throat during swallowing)
• Secretions of parotid gland
• Somatic sensations & taste on posterior 1/3 of tongue
12. VIII = Vestibulocochlear Nerve
• Cochlear branch begins in medulla
– receptors in cochlea
– hearing
• Vestibular branch begins in pons
– receptors in vestibular
apparatus
– sense of balance
– vertigo (feeling of rotation)
– ataxia (lack of coordination)
13. Pons
• The pons is located superior to the medulla. It connects the spinal cord with the brain and links parts of the brain with one another by way of tracts.
– relays nerve impulses related to voluntary skeletal movements from the cerebral cortex to the cerebellum.
– contains the pneumotaxic and apneustic areas, which help control respiration along with the respiratory center in the medulla.
• One inch long
• White fiber tracts ascend and descend
• Pneumotaxic & apneustic areas help control breathing
• Middle cerebellar peduncles carry sensory info to the cerebellum
• Cranial nerves 5 through 7
14.VII = Facial Nerve
• Motor portion
– facial muscles
– salivary & nasal and oral mucous glands & tears
• Sensory portion
– taste buds on anterior 2/3’s of tongue
15. VI = Abducens Nerve
• Lateral rectus eye muscle
16.V = Trigeminal Nerve
• Motor portion
– muscles of mastication
• Sensory portion
– touch, pain, & temperature receptors of the face
• ophthalmic branch
• maxillary branch
• mandibular branch
17. Midbrain
• One inch in length
• Extends from pons to diencephalon
• Cerebral aqueduct connects 3rd ventricle above to 4th ventricle below
• Cerebral peduncles---clusters of motor & sensory fibers
• Substantia nigra---helps controls subconscious muscle activity
• Red nucleus-- rich blood supply & iron-containing pigment
– cortex & cerebellum coordinate muscular movements by sending information here from the cortex and cerebellum
18. IV = Trochlear Nerve
• Superior oblique eye muscle
19.III = Oculomotor Nerve
• Levator palpebrae raises eyelid (ptosis)
• 4 extrinsic eye muscles
• 2 intrinsic eye muscles
– accomodation for near vision (changing shape of lens during reading)
– constriction of pupil
20. Cerebellum
• 2 cerebellar hemispheres and vermis (central area)
• Function
– correct voluntary muscle contraction and posture based on sensory data from body about actual movements
– sense of equilibrium(helps maintain posture and balance)
– appears to be involved in cognition
• Transverse fissure between cerebellum & cerebrum
• Cerebellar cortex (folia) & central nuclei are grey matter
• Arbor vitae = tree of life = white matter
THE DIENCEPHALON
21. Diencephalon Surrounds 3rd Ventricle
• Surrounds 3rd ventricle
• Superior part of walls is thalamus
• Inferior part of walls & floor is hypothalamus
22. Thalamus
• The thalamus is located superior to the midbrain and contains nuclei that serve as relay stations for all sensory impulses, except smell, to the cerebral cortex.
• It also registers conscious recognition of pain and temperature and some awareness of light touch and pressure.
• It plays an essential role in awareness and the acquisition of knowledge (cognition.)
• 1 inch long mass of gray mater in each half of brain (connected across the 3rd ventricle by intermediate mass)
• Relay station for sensory information on way to cortex
• Crude perception of some sensations
23. Hypothalamus
• The hypothalamus
– inferior to the thalamus, has four major regions (mammillary, tuberal, supraoptic, and preoptic)
– controls many body activities, and is one of the major regulators of homeostasis.
• The hypothalamus has a great number of functions.
– It controls the ANS.
– It produces hormones.
– It functions in regulation of emotional and behavioral patterns.
– It regulates eating and drinking through the feeding center, satiety center, and thirst center.
– It aids in controlling body temperature.
– It regulates circadian rhythms and states of consciousness.
24. Epithalamus
• Pineal gland
– endocrine gland the size of small pea
– secretes melatonin during darkness
– promotes sleepiness & sets biological clock
• Habenular nuclei
– emotional responses to odors
25. Cerebrum
• The cerebrum is the largest part of the brain.
– The surface layer, the cerebral cortex, is 2-4 mm thick and is composed of gray matter. The cortex contains billions of neurons.
• Beneath the cortex lies the cerebral white matter, tracts that connect parts of the brain with itself and other parts of the nervous system.
26. SUMMARY
https://www.youtube.com/watch?v=owFnH01SD-s
https://www.youtube.com/watch?v=noWwbvmdhL0
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