chapter 14: autonomic nervous system

meltzer

central nervous system (CNS)

brain and spinal cord

peripheral nervous system (PNS)

nerves and ganglia located outside of the brain and spinal cord

autonomic nervous system (ANS)

involuntarily controls smooth muscle, cardiac muscle, and glands to maintain homeostasis (part of PNS)

• 2 divisions

somatic nervous system

cell body of motor neurons that enter CNS to ventral horn and exits through ventral root will NOT synapse and go straight to target organ

acetylcholine (ACh)

transmitter released by neurons

autonomic nervous system: sympathetic division

two-neuron system

pre-ganglionic sympathetic neuron exciting CNS is SHORT

• makes ACh and goes onto post-ganglionic sympathetic neuron

post-ganglionic sympathetic neuron is very LONG & goes all the way to target organ

• makes NE and goes onto target organ

NE (norepinephrine)

also known as adrenaline, neurotransmitter released by neurons

autonomic nervous system: sympathetic exception

only one neuron

pre-ganglionic sympathetic neuron that goes to adrenal gland

• releases ACh on specialized cells in middle of gland (adrenal medulla)

• modified cells then release epinephrine & norepinephrine (neurohormones) into blood

very fast and widespread response is based on..

1. going to the blood or

2. the type of receptor on organ for the neurotransmitter

receptor type

determines weather the muscles of cardiac and smooth will be excitatory or inhibitory

skeletal muscle

is excitatory only

autonomic nervous system; parasympathetic division

two-neuron system

pre-ganglionic parasympathetic neuron that exits spinal cord is very very LONG

• releases ACh onto post-ganglionic neuron

ganglion oftentimes on surface of target organ

post-ganglionic parasympathetic neuron is very SHORT

• releases ACh onto target organ

three D’s of parasympathetic division

body processes that happen at rest:

Digestion

Defecation

Diuresis (urine)

sympathetic

flight vs. flight

mobilizes energy stores

parasympathetic anatomy: craniosacaral division

goes to target organs by the cranial region/lower brain stem or sacral region/sacral nerves

parasympathetic anatomy of cranial region

ACh released onto…

eyes → pupillary constriction

salivary glands → boosts saliva production

vagus nerve → decreases (heart) rate

→ slight bronchial constriction (lungs)

→ increases contraction, mobility, production of digestive juices (stomach)

→ boosts digestive enzyme production and releases (pancreas)

→ boosts production of bile (liver)

→ contracts & expels bile into GI tract & relaxation if sphincters (gall bladder)

→ inhibit blood flow to labia, penis, clit and addition mucous and lube (genitalia)

parasympathetic anatomy of sacral region

Ach released onto…

bladder → increase contractile activity

genitalia → sexual arousal: increases production of mucus/lubricants, vasodilation of blood vessels to engorge penis, clit, labia, etc

sympathetic anatomy (thoracolumbar division)

travel to organs by blood vessels, exits spinal cord through thoracic regions or upper lumbar regions

sympathetic anatomy of neurons

all pre-ganglion neurons are SHORT, then immediately synapse in sympathetic ganglion chain

sympathetic ganglion chain

sense of ganglion that are adjacent on either side of spinal cord that allow for communications up & down

sympathetic anatomy thoracic region

T1 pre-ganglionic neuron exits, then synapses

• post-ganglionic neuron could go to lungs or ride sympathetic ganglion chain with blood vessels to the eyes or skin

long post-ganglionic sympathetic neuron to salivary glands

sympathetic anatomy lumbar region

NE released onto…

eyes → pupillary dialation

skin → sweating & hair rising (ACh released by SNS onto sweat glands)

heart → increase heart rate

lungs → bronchodilation

stomach →inhibits digestion

blood → to everything!

liver → inhibits

bladder → bladder contraction & keep sphincter closed

genitalia → inhibit blood flow

adrenal glands → causes release of more catecholamines

salivary glands → inhibit (dry mouth)

kidney → stop making urine

catecholamines

norepinephrine and epinephrine

arrector pilae

muscles on base on each hair of skin (caused goosebumps)

parasympathetic cranial nerves

CN III. 3. oculomotor: pupillary construction

CN VII. 7. facial: PS info to lining of nasal cavity to keep moist of mucous, maintence of eye protection by lacrimal gland, and salivary glands

CN IX. 9. glossopharyngeal: goes to parotid gland for saliva in mouth while chewing

CN X. 10. vagus: stomach, pancreas, GI tract turns on, intestines get increased mobility, physical contractions, peristalsis, moving things along + mixing things up, boosts production of digestive juices

vertebral level of L1 and L2

PS info exits spinal cord into sacral region of nerves: S2, S3, S4 nerves

pelvic splanchnic nerves

• goes to rest of the organs of pelvis

• S2, S3, S4

menstruation

parasympathetic nervous system

defecation

parasympathetic

adrenic receptors

• recognize catecholamines (Ne and epinephrine)

• on surface of all organs controlled by sympathetic NS

sympathetic nervous system anatomy

• spinal cord located behind thoracic vertebrae

• two new rami

• white ramus communicates

• gray ramus communicants

two new rami in sympathetic nervous system that only carry sympathetic axons to sympathetic chain/trunk

3 different pathways

1. Spinal nerve pathway

1. Sympathetic nerve pathway

2. Splanchnic nerve pathway

1. Spinal nerve pathway

Synapse at the same level

• Preganglionic fiber enters the sympathetic chain

• Synapses in a ganglion at the same spinal level

• Postganglionic fiber exits via gray ramus communicans

• Goes to body wall structures (sweat glands, arrector pili muscles, blood vessels)

ex. arrector pili muscles & sweat glands of skin

2. Sympathetic nerve pathway

Ascend or descend, then synapse

• Preganglionic fiber enters the sympathetic chain

• Travels up or down the chain

• Synapses at a different level

• Postganglionic fiber exits to target

ex. smooth muscle of blood vessels

3. Splanchnic nerve pathway

Pass through without synapsing (splanchnic pathway)

• Preganglionic fiber passes through sympathetic chain

• Forms splanchnic nerves

• Synapses in prevertebral (collateral) ganglia

• Targets abdominal and pelvic organs

ex. gi tract

medullary chromosphere cells

• postganglionic neurons modified by ACh

• make norepinephrine & epinephrine

pheochromocytoma

tumor of medullary chromophere cells

visceral reflexes

1. receptor in viscera

2. visceral sensory neuron

3. integration center: preganglionic neuron, dorsal horn

4. motor neuron: both post & pre

5. visceral effector

cholinergic & adrenergic receptors

receptors that recognize chemicals

cholinergic receptors

receptors that recognize acetylcholine (ACh)

• nicotinic

• muscarinies

nicotinic receptors

type of cholinergic receptors that are located in skeletal muscles and cell bodies of postganglionic neurons on ANS

muscarinies receptors

everywhere else in ANS, all PS organs, some sympathetic organs

adrenergic receptors

receptors that recognize norepinephrine and epinephrine released by adrenal medulla

Beta 1 (B1)

heart → increases heart rate

Beta 2 (B2)

lungs

Beta 3 (B3)

fat → breakdown of adipose/fat cells

Alpha 1 (a1)

blood vessels → constricts except skeletal muscles, heart, & brain

Alpha 2 (a2)

moderates how much NE release there is (moderator of sympathetic activity)

how ANS is controlled

brain:

• hypothalamus: communicates up and down w limbic system and cerebral cortex involved, and communicates down and controls ANS and endocrine system

• brain stem: hypothalamus controls primatial functions like pupil size, heart, blood pressure etc by nuclei and neurons

• spinal cord: reflexes for urinarion, defecation, erection, and ejaculation