Handout4 - Handout 4 AUTONOMIC NERVOUS SYSTEM Peripheral...

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Handout 4 AUTONOMIC NERVOUS SYSTEM Peripheral Nervous System: has afferent division (sensory) and efferent division. Efferent division is divided into somatic motor neurons (voluntary ), which control movement of skeletal muscles, and autonomic neurons (involuntary) , which control smooth muscle (think about layer of arteries and veins, gastrointestinal tract, respiratory tract, etc), cardiac muscle (heart), glands, and adipose tissues. A. TWO BRANCHES OF AUTONOMIC NERVOUS SYSTEM (ANS): Parasympathetic system: known for “rest and digest” controls Sympathetic system: known for “fight or flight” controls. However, must keep in mind that in daily mundane activities, sympathetic system also has an important contribution, for example: its regulation of blood flow to tissues. Most of the time, para- and sympa alternate to control and fine-tune body functions( for homeostasis). Only on occasions, such as see a snake, then the control of one system, in this case sympa-, dominates. B. ANS AND HOMEOSTASIS: 1 -After receiving sensory inputs from the somatosensory and visceral receptors, many brain structures including limbic system, hypothalamus, pons, medulla, and cerebral cortex send signals to autonomic system, endocrine system, and behavioral state system to regulate body homeostasis. Example: Hypothalamus regulates body temperature, water balance, eating behavior,etc. Medulla for respiration, heart rate, etc Cerebral cortex and/or limbic system: emotion, etc. -however, some autonomic reflexes can take place without signal from the brain, yet these processes can still be influenced by the CNS. These are called spinal reflexes, including urination, defecation, and penile erection. 2. Types of control : - One character of autonomic division is its antagonistic control, mostly for internal organs. If para- signal is excitatory, then sympa- is inhibitory, and vice versa. Example: heart rate: since sympa- is fight-or flight response, so of-course it increases the heart rate, while para- decreases it. Exception to this antagonistic control is the sweet glands and the smooth muscle in blood vessels. Only sympathetic branch controls these tissues by adjusting its level (tonic control). - Another type of control is co-operations of the two branches. Each will work on a different tissue to aim for a common goal. Example: para-: controls blood flow for erection, while sympa-controls muscle contraction for ejaculation - Para- or sympa- both rely of neurotransmitters to affect the target tissues. Sometimes the types of neurotransmitters receptors on the target determine the control. Example: sympa- release catecholamines to bind to the adrenergic receptors on the
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This note was uploaded on 10/28/2010 for the course BIPN 100 taught by Professor French during the Winter '07 term at UCSD.

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Handout4 - Handout 4 AUTONOMIC NERVOUS SYSTEM Peripheral...

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