1 Michael Chilmaid From: Michael Chilmaid [firstname.lastname@example.org] Sent: Friday, April 30, 2010 12:50 PM To: email@example.com Subject: BIO 202 NOTES 4/30 Signed By: mjc4rx@Virginia.EDU Importance: High MUSCLE AND MOVEMENT Muscle fibers are made up of myofibril of which the function unit is the sarcomere. Sarcomere appears as dark colored sections Contraction? Thick filaments = myosin. Thin filaments = actin. Thick and thin filaments slide by each other. Action of the myosin heads ? Force generated from use of ATP. Results in contraction. Changes in the conformation of the myosin head produces movement = DIAGRAM ATP binding site, actin binding site. Cycle 1. Myosin head is bound to myosin subunit. ATP binds to head ? head releases 2. ATP is hydrolyzed ? head pivots and binds new actin subunit. Energy used to extend head. 3. P1 is released. Head pivots and thus moves filament (=power stroke). 4. ADP is released and cycle is ready to repeat. Actin subunits inched towards each other Toponin and Tropomyosin Fibrous strand of tropomyosin blocks binding sight until stimulation. Depolarization takes place as a result of the action potential. Troponin undergoes a conformational change . How do action potential trigger muscle contraction? Highly organized series of tubules are the sarcoplasmic reticulum. Run parallel to cell. T-tubule runs perpendicular to cell. Transverse tubules are in close association with Motor unit = single motor neuron and the fivers it innervates. CHEMICAL SIGNALING Chemical signaling involves non-electical signaling and occurs at much slower rate. The hormonal system is the system of focus and works closely with the nervous system. Work with hypothalamus and pituitary axis. 6 types if signaling: Autocrine signaling ? single cell releases chemical signal that has effect on that same cell Paracrine signaling ? single cell releases chemical signal that has effect of neighboring cells. Endocrine signals ? hormones carries between cells by blood or other body fluids. Neural signals ? diffuse at short difference between neurons (NERVOUS SYSTEM) Neuroendocrine signals ? signals are released from neurons but are carries by blood or other body fluids and act on distant cells. Pheromones ? released from one organism and act on a different individual 2 Hormone ? those chemical signals that are present in tiny concentrations and travel throughout the body to affect target cells. Function of hormonal signals : Animals respond to environmental change, develop as embryos, sexual maturation, and achieve homeostasis Hormones bind to receptors inside target cells and change gene expression. Others bind to receptors at the cell surface and lead to changes in protein activation. Single endocrine organ may produce multiple hormones. Single hormone may be secreted by more than one gland. Single hormone may have more than one target cell and thus induce more than one effect. Some hormones have cyclic rates of secretion. mjc4rx
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