Chapter 16 Autonomic Nervous System

•ANS consists of motor neurons that –Innervate smooth and cardiac muscle, and glands –Make adjustments to ensure optimal support for body activities –Operate via subconscious control •Also called involuntary nervous system or general visceral motor system •Motor portion of PNS that controls homeostasis

The hypothalmus

•“Fight-or-Flight" •Mobilizes body during activity •Exercise, excitement, emergency, embarrassment –Increased heart rate; dry mouth; cold, sweaty skin; dilated pupils •During vigorous physical activity –Shunts blood to skeletal muscles and heart –Dilates bronchioles –Causes liver to release glucose

•“Resting and Digesting” •Promotes maintenance activities and conserves body energy –Directs digestion, diuresis, defecation, etc. •As in person relaxing and reading after a meal –Blood pressure, heart rate, and respiratory rates are low –Gastrointestinal tract activity high –Pupils constricted; lenses accommodated for close vision

–Cell body in CNS; thick, myelinated, group A fiber extends in spinal or cranial nerve to skeletal muscle

–All somatic motor neurons release acetylcholine (ACh) –Effects always excitatory – stimulates muscle contraction

1. Preganglionic neuron (in CNS) has a thin,
lightly myelinated preganglionic axon.
2. Postganglionic (ganglionic) neuron in
autonomic ganglion outside CNS has
nonmyelinated postganglionic axon that
extends to effector organ

–All preganglionic fibers release ACh –Postganglionic fibers release norepinephrine or ACh at effectors –Effect is either excitatory or inhibitory, depending on type of receptors

1. Preganglionic neuron (in CNS) has a thin,
lightly myelinated preganglionic axon.
2. Postganglionic (ganglionic) neuron in
autonomic ganglion outside CNS has
nonmyelinated postganglionic axon that
extends to effector organ

–All preganglionic fibers release ACh –Postganglionic fibers release norepinephrine or ACh at effectors –Effect is either excitatory or inhibitory, depending on type of receptors

(paired)- viseceral effectors in thoracic cavity, head, body wall, and limbs

lie on both sides of the vertebrae column

Anterior to vertebral bodies. collateral ganglia contain ganglion nuerons that innervate tissues and oragns in the abdominalpelvic cavity.

pstgsnglionic fibers

The ganglionic neurins of the adrenal medullae have short axons. when stimulated, they release their nuerotransmitters into the bloodstreem, not at a synapse. this mode of release allows the nuerotrnasmitters to function as hormones, affecting target cells throughout the body

(1)heightened mental alertness, (2) increased metabolic rate, (3) reduced digestive and urinary functions, (4) activation of energy reserves, (5) increased respiratory rate and dilation of respiratory passageways, (6) increased heart rate and blood pressue, and (7) acitvation of sweat glands

catabolic breaks down molecules and releases energy. sympatheric releases energy.

(1) decreased metabolic rate, (2) decreased heart rate and blood pressure, (3) increased secreation by salivary and digestive glands, (4) increased motility blood flow in the digestive tract, and (5) stimulation of urination and defecation.

anabolic pieces molecules together which is making energy. parasympathetic is conserving energy.

(1) decreased metabolic rate, (2) decreased heart rate and blood pressure, (3) increased secreation by salivary and digestive glands, (4) increased motility blood flow in the digestive tract, and (5) stimulation of urination and defecation.

anabolic pieces molecules together which is making energy. parasympathetic is conserving energy.

•Cholinergic fibers release neurotransmitter ACh –All ANS preganglionic axons –All parasympathetic postganglionic axons at effector synapse •Adrenergic fibers release neurotransmitter NE –Most sympathetic postganglionic axons –Exception: sympathetic postganglionic fibers secrete ACh at sweat glands

•Parasympathetic division: short-lived, highly localized control over effectors –ACh quickly destroyed by acetylcholinesterase •Sympathetic division: longer-lasting, bodywide effects –NE inactivated more slowly than ACh –NE and epinephrine hormones from adrenal medulla prolong effects