学霸笔记

  Tigers | Nonfiction Reading Test 2   Who would win in a fight, a lion or a tiger? Well, if size has anything to do with the matter, the tiger would win. That’s because tigers are the largest of all cat species. They grow up to eleven feet long and weigh as much as 670 lbs. This makes tigers the third largest land carnivore. The only larger land carnivores are polar bears and brown bears. Tigers are not only large, they are also fast. They can sprint as fast as 40 miles per hour for short distances and leap as far as 30 feet horizontally.   This makes for an extremely dangerous pounce. You might not think that such large, fast, and ferocious creatures need help to survive, but they do. The tiger is an endangered species. Despite all of the tiger’s strengths, the future of the species is uncertain. Tigers face a very high risk of extinction. It is estimated that at the start of the 20 th century, there were over 100,000 tige...

Lect 15 The Autonomic Nervous System 1. Describe about autonomic nervous system • The autonomic nervous system (ANS) operates via reflex arcs. • Regulate activity of smooth muscle, cardiac muscle & certain glands • Receives input from limbic system and other regions of the cerebrum • Operation of the ANS to maintain homeostasis, however, depends on a continual flow of sensory afferent input, from receptors in organs,  and efferent motor output to the same effector organs.  • Structurally, the ANS includes autonomic sensory neurons, integrating centers in the CNS, and autonomic motor neurons.  • Functionally, the ANS usually operates without conscious control. • The ANS is regulated by the hypothalamus and brain stem. ANS: • The output (efferent) part of the ANS is divided into two principal parts:   – the sympathetic division – the parasympathetic division – Organs that receive impulses from both sympathetic and parasympathetic fibers are said to have du...

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 – 8...