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Chapter 15 - Autonomic Nervous System
Autonomic nervous system Somatic nervous system
-Involuntary -Voluntary -Target organs - cardiac muscle, smooth muscle, and glands -Target organs - skeletal muscles -Utilizes neurotransmitters – Acetylcholine, Norepinephrine & epinephrine’s ( both are adrenalin) -Utilizes neurotransmitters –Acetylcholine -Two-neuron chain (slow) – Preganglionic (myelinated) – use only Acetylcholine Postganglionic (unmyelinated) - use Acetylcholine or Adrenalin The adrenalin effect will vary according to the target tissue (stimulatory or inhibitory) -Single Neurons (fast) - myelinated - use Acetylcholine
Autonomic nervous system
Sympathetic Parasympathetic
-Fight-or-flight -Rest and digest -Originate in the thoracic and lumbar regions of the spinal cord ( Thoracolumbar ) -Originate in the cranial and sacral regions of the spinal cord ( Craniosacral ) -Has short preganglionic fibers and long postganglionic fibers -Has long preganglionic and short postganglionic fibers
- located near the spinal cord - located in the visceral effector organ or near it Generally INCREASE internal activities Generally DECREASE internal activities Effects: Effects: Increases heart rate/ BP (^) Decrease heart rate/ BP Dilates pupils (^) Constrict pupils Inhibits secretion of digestive glands (^) Stimulates salivary, lacrimal, and pancreas glands Stimulates sweating (^) Causes contraction and emptying of hollow organs: Bladder, gallbladder, stomach, intestines ( peristalsis ) Dilates bronchioles (^) Minimal on blood vessels and bronchioles Causes ejaculation (^) Vasodilation of penis (erection) Stimulates arrector pili *Increases digestive processes Stimulates adrenal medulla to secrete epi- and norepinephrine * Increases urine output Stimulates glycogenolysis in liver (glucose release) Blood vessel constriction/dilation and blood coagulation Release of renin from kidneys that in turn activates a system that increases blood pressure *Decreases digestive processes *Decreases urine output The actions in autonomic nervous system are by dual innervation meaning the two divisions counterbalance each other's activities in an attempt to maintain homeostasis.
Neurotransmitter Synapses:
- Cholinergic fiber release Acetylcholine (Ach) @ - All ANS preganglionic axons and - All parasympathetic postganglionic axons Two receptors: 1. Nicotinic receptors - acting like nicotine 2. Muscarinic receptors - acting like toxin from mushrooms
- Adrenergic release Norepinephrine (NE) or Epinephrine
Centers of hypothalamus controls:
Heart activity, blood pressure, temperature of body, water balance, and endocrine activity, Emotional responses (rage, fear, pleasure) activated through limbic system signal hypothalamus to activate fight-or-flight system.
Autonomic nervous system (ANS) disorders involve deficient control of smooth muscle activity
Hypertension (high blood pressure) Overactive sympathetic vasoconstrictor response to stress Can be treated with adrenergic receptor-blocking drugs Raynaud’s disease Painful, exaggerated vasoconstriction in fingers and toes (some areas of the body feel numb) Treated with vasodilators Autonomic dysreflexia Life-threatening, uncontrolled activation of autonomic neurons in quadriplegics and people with spinal cord injuries above T Blood pressure skyrockets, posing increased risk for stroke
Effects of age on ANS
- Constipation
- Dry eyes and frequent eye infections
- Orthostatic hypotension
- Low blood pressure after position change
- Pressure receptors are less responsive to blood pressure changes
- Cardiovascular centers fail to maintain healthy blood pressure
Pain Chart - Conscious perception of visceral sensations map to specific regions of the body, as shown in this chart. Some sensations are felt
locally, whereas others are perceived as affecting areas that are quite distant from the involved organ
