UNIT 4 AUTONOMIC NERVOUS SYSTEM

autonomic nervous system (ANS)

routine homeostatic adjustments made from subconscious mind

preganglionic neurons

visceral motor neurons in brain stem & spinal cord

preganglionic fibers

axons of preganglionic neurons

ganglionic neurons

visceral motor neurons in peripheral ganglion

autonomic ganglia

made of ganglionic neurons → innervate visceral effectors

postganglionic fibers

axons of ganglionic neurons, go from autonomic ganglia to peripheral target organ

sympathetic division

readies body for a crisis, presynaptic fibers (thoracic & upper lumbar) synapse in ganglia near spinal cord

parasympathetic division

conserves energy & promotes sedentary activities, preganglionic fibers originate in brain stem and sacral segments of spinal cord

7 responses to increased sympathetic activity

• heightened mental alertness

• increased metabolic rate

• reduced digestive and urinary functions

• energy reserves activated

• increased respiratory rate and respiratory passageways dilate

• increased heart rate and blood pressure

• sweat gland activated

sympathetic chain ganglia

lateral to vertebral column, innervates body wall, head, limbs, and thoracic

sympathetic nerves

postganglionic fibers from chain that innervates thoracic activity

collateral ganglia

anterior to vertebral bodies, tissues, and organs of abdominal cavity

celiac ganglion

innervates stomach, liver, gallbladder, pancreas, and spleen

superior mesenteric ganglion

innervates small intestine and most of large intestine

inferior mesenteric ganglion

innervates distal large intestine, urinary, and reproductive system

adrenal medulla

center of adrenal glands, release neurotransmitters into blood, acts as hormones

neurotransmitter release

released by depolarized postganglionic fiber

sympathetic stimulation and the release of NE & E

general excitatory effect

alpha receptors

stimulated by norepinephrine (NE) & epinephrine (E)

beta receptors

stimulated by epinephrine (E)

sympathetic stimulation & release of Ach and NO

ach - activates sweat glands

NO - dilated blood vessels to skeletal muscles

parasympathetic division

• decreases metabolic rate

• reduction in heart rate and blood pressure sweat

• digestive glands increase secretion

• increase in digestive motility and blood flow

• defecation & urination

• sexual arousal - stimulation of sexual glands

terminal ganglion

located near the target organ

intramural ganglion

embedded in the tissues of the target organ

pelvic nerves

preganglionic fibers from sacral segments that innervates body wall distal large intestine, urinary, and reproductive systems

parasympathetic activation

relaxation, food and energy absorption, cell growth

neurotransmitter release

always ACh → has a localized effect at neuromuscular & neuroglandular sites

dual innervation

receiving sympathetic & parasympathetic

autonomic plexuses

• cardiac plexus - heart

• pulmonary plexus - lungs

• esophageal plexus - esophagus

• celiac plexus - digestive, urinary, & reproductive systems

• inferior mesenteric plexus - digestive, urinary, & reproductive systems

• hypogastric plexus - digestive, urinary, and reproductive systems

autonomic tone

maintains background level of activity

ex. heart rate & blood vessel diameter

visceral reflexes

lowest level of ANS reflexes

visceral reflex arc

receptor → sensory neuron → interneuron → visceral motor neurons

long reflexes

involves CNS

short reflexes

bypasses CNS

higher-order functions

1. cerebral cortex is required

2. involves conscious and unconscious information

3. subject to adjustment and modification (not a pre-wired reflex)

fact memories

bits of information

skill memories

learned motor behaviors

short-term memories

do not last long

long-term memories

can last a life time

secondary long-term memories

need to be reviewed

tertiary long-term memories

lasts a life time

memory consolidation

converting short term to long term, amygdaloid body & hippocampus

basal nuclei

memory consolidation, storage & retrieval

serotonin

compounds that enhance effects also produce hallucinations, compounds that inhibit or block action cause severe depression and anxiety

dopamine

important in nuclei that control intentional movements

parkinsons disease

inadequate dopamine production causes motor problems

huntingtons disease

destruction of ACh-secreting and GABA- secreting neurons, difficulty controlling movements, intellectual abilities gradually decline

aging and the nervous system

• reduction in brain side, weight, and number of neurons

• decrease in blood flow to brain

• changes in the synaptic organization of the brain

• intercellular and extracellular changes in CNS neurons

infections

rabies, polio

congenital disorders

spina bifida, hydrocephalus

degenerative disorders

ALS (lou gehrigs), alzheimers disease, parkinsons disease

secondary disorders

strokes, demyelination disorders

tumors

neural origin

trauma

spinal cord injuries, concussions

toxins

heavy metals, neurotoxins

senility

(dementia) memory loss, amnesia