notes-nerv-endo - BIOL 326 - General Physiology Animal...

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1 BIOL 326 - General Physiology Animal Physiology Lecture Notes : Nervous and endocrine systems . February 3 -12 , 2010 Dr M. Sweeney-Nixon rd th Objectives: At the end of this section, you will be able to describe how organismal homeostasis is maintained in animals. 1. organization of endocrine and nervous systems in animals. 2. names of endocrine glands and the hormones they release. 3. names & functions of hormones & some neurotransmitters (ACH, NA). 4. Basic homeostatic nervous and endocrine reflexes (including neuro-endocrine reflexes). Animals must maintain homeostasis in the face of ‘stress’. For an animal, stress is not necessarily what humans define as stress. It is anything that threatens its survival. 9 or 8 blood glucose : threatens the ability to produce ATP and do biological work; changes osmolarity (consistency of blood). 9 or 8 blood Ca 2+ : threatens muscle contraction, including the heart (which beats/contracts constantly) and the diaphragm, which is essential for ventilation (breathing). 9 blood pressure : threatens blood circulation to the brain & other organs 8 or 9 blood osmolarity : threatens tissue water/volume/shape etc 8 22 blood CO / 9 blood pH or O : threatens proteins and the ability to make ATP Other: predation, drought, fasting, weight loss, illness etc. Biological control systems : An animal’s survival depends on receiving and correctly interpreting information from its external environment (e.g. light, infrared radiation, sound waves, temperature, pressure, chemicals [taste and smell, pheromones], electric &magnetic fields) and internal environment (chemicals e.g. glucose, pH, body temperature, pressure). All animals have biological control systems (see intro notes): sensors that monitor physiological variables, afferent and efferent paths, and an integration center. In a simple endocrine control system, the endocrine system detects and responds, whereas in the majority of cases, the nervous system detects and responds using neuronal circuits (see below) or neuroendocrine circuits. Thus, “animals have 2 systems of internal communication and regulation, the nervous system and the endocrine system” (Campbell, 5th ed., p. 894 [from Chapter 45])”. The nervous system is faster , as it consists of neurons firing electrical signals (action potentials) that take only milliseconds. The released chemical signal has a local effect , which contributes to the speed. In contrast, the endocrine system is slower - responses require release of hormones from secretory cells or glands into the circulation (blood or hemolymph); some effects are on transcription and so responses takes minutes, hours, days and sometimes weeks. There is a signaling cell ( neuron ; endocrine gland or tissue ) that releases molecules ( neurotransmitters , hormones and neurohormones ) that affect target
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2 cells by binding to receptors, leading to many diverse effects. Neurotransmitter effects are mediated by receptors in the plasma membrane of the target cell; water soluble hormones (adrenaline, peptides) also act at the membrane of the target cell following release by exocytosis.
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notes-nerv-endo - BIOL 326 - General Physiology Animal...

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