Autonomic Nervous System (A&P, exam 4)

Is the autonomic nervous system efferent or afferent?

efferent

What does the ANS control?

involuntary functions of the smooth muscle, cardiac muscle, and glands

What controls the ANS?

the hypothalamus (with limbic system, thalamus, and cortex input)

Is the ANS conscious or unconscious?

unconscious

What’s the main function of the ANS?

maintain homeostasis

What systems does the ANS regulate?

cardiovascular, respiratory, digestive, urinary, reproductive, etc.

Divisions of the ANS

Sympathetic and parasympathetic

Main role of sympathetic division

expenditure of energy

When is sympathetic division activated?

physical or emotional stress, fight or flight situations

Main role of parasympathetic division

conserve and restore body energy

Parasympathetic activates under

rest and recovery

dual innervation

opposing sympathetic and parasympathetic effects

During dual innervation of the heart, the sympathetic division

increases heart rate

During dual innervation of the heart, the parasympathetic division

decreases heart rate

During dual innervation of the pupils, the sympathetic nervous system

dilates (widens) the pupils

During dual innervation of the pupils, the parasympathetic division

constricts the pupils

During dual innervation of the digestive tract, the sympathetic division

decreases motility and secretions

During dual innervation of the digestive tract, the parasympathetic division

increases motility and secretions

During dual innervation of the bronchioles (airways), the sympathetic division

dilates the airways

During dual innervation of the bronchioles (airways), the parasympathetic division

constricts the airways

Organs with only sympathetic input (single innervation)

• sweat glands,

• arrector pili muscles,

• blood vessels of skeletal muscle, heart, and lungs

• blood vessels of digestive viscera and kidney

under sympathetic input the sweat glands

increase secretion

under sympathetic input the arrector pili muscles

contract

under sympathetic input the blood vessels of the skeletal muscle, heart, lungs, and brain

dilate

under sympathetic input the blood vessels of the digestive viscera and kidney

constrict

organs with only parasympathetic input

lacrimal glands (tears)— increased secretion

how many neurons are there in the ANS efferent pathway

two

first neuron of the ANS efferent pathway

preganglionic axon

The preganglionic axon

sends CNS motor neurons → autonomic ganglionic motor cells in the PNS

second neuron in the ANS efferent pathway

postganglionic axons

The postganglionic axon sends

motor neurons in the autonomic ganglia → effectors

Another name for the sympathetic division

thoraco-lumbar division

origin of the sympathetic preganglionic cell body

spinal cord segments T1-L2 of the lateral horn

length of the sympathetic preganglion

short

length of the sympathetic postganglion

long

sympathetic ganglions are typically ____ to the CNS

closer

another name for the parasympathetic division

cranio-sacral division

parasympathic origin

CN III, VII, IX, X + S2-S4

the parasympathetic preganglionic axon is

long

parasympathetic postganglion axon length

short

the parasympathetic ganglion location

near or in effector organ

sympathetic preganglion axon pathways

• some synapse onto chain ganglia cells

• some bypass the chain ganglia to the collateral ganglia and adrenal medulla

where are sympathetic chain ganglia

on each side of the vertebral column

how many sympathetic chain ganglia

two

function of the sympathetic chain ganglia

innervate head, body wall, limbs, and thoracic cavity (heart, lungs)

sympathetic collateral ganglia location

close to large abdominal arteries

types of collateral ganglia

celiac, superior mesenteric, and inferior mesenteric ganglia

collateral ganglia pathway

preganglion passes through chain ganglia and forms splanchnic nerves to reach collateral ganglia

collateral ganglia function

innervate abdominal and pelvic viscera

pathway of sympathetic adrenal medulla

preganglionic fibers pass through chain ganglia and splanchnic nerves to celiac ganglia which passes through to reach adrenal gland

adrenal gland function

secrete hormones into the blood

where are parasympathetic preganglionic neurons?

the brainstem and sacral segments of the spinal cords

where are parasympathetic ganglionic neurons located

peripheral neurons in peripheral ganglia near or within target organs

what nerves carry parasympathetic preganglionic axons from S2-S4?

pelvic nerves

Where do parasympathetic preganglionic neurons synapse in the sacral region?

Intramural ganglia

What are intramural ganglia?

Ganglia located within the walls of target organs

Cranial nerve III (oculomotor) function

parasympathetic control of the pupil and lens

cranial nerve VII (facial)

lacrimal and salivary glands

cranial nerve IX (glossopharyngeal)

salivary glands

cranial nerve X (vagus)

parasympathetic control of the heart, lungs, digestive tract, and all other thoracic and abdominal viscera except most inferior portions

most important parasympathetic nerve

cranial nerve X (vagus)— 75% of all parasympathetic output

Sympathetic and parasympathetic divisions are activated by (the) ______ stimuli

different

sympathetic activation has a _____ effect on the body

widespread/systemic

How many ganglionic cells does a single sympathetic preganglionic axon synapse onto?

24 or more

What hormones does the adrenal medulla release?

mostly epinephrine (80%), but some norepinephrine (20%)

Where does the adrenal medulla send hormones?

into the bloodstream

Can the adrenal medulla have effects on tissues not innervated by the ANS?

yes, because of its ability to send hormones throughout the bloodstream

Parasympathetic activation has a _____ effect on the body

localized

parasympathetic activation innervation locations

head and viscera

How many ganglionic cells can a parasympathetic preganglionic axon synapse on to?

6-8

How many effectors can parasympathetic postganglionic axon target?

usually just a single effector.

What is the neurotransmitter of the sympathetic and the parasympathetic preganglionic axon?

AcH for both the sympathetic and parasympathetic ganglia

What is the neurotransmitter of the sympathetic and the parasympathetic postganglionic axon (onto the effectors)?

parasympathetic: ACh

sympathetic: NE (if dual innervated)

What determines the effect a neurotransmitter has on the postsynaptic cell?

the postsynaptic receptor

How many postsynaptic receptors does a neurotransmitter have?

many have more than one

Nicotinic cholinergic receptors location

skeletal muscles, autonomic ganglia

are nicotinic cholinergic receptors excitatory or inhibitory?

excitatory

muscarinic cholinergic receptors location

visceral muscles, cardiac muscles, CNS

are muscarinic cholinergic receptors excitatory or inhibitory?

both

are muscarinic cholinergic receptors parasympathetic or sympathetic?

parasympathetic (affect visceral muscles and cardiac muscle)

are nicotinic cholinergic receptors parasympathetic or sympathetic?

both (target all autonomic ganglia)

what neurotransmitter do cholinergic receptors use?

AcH

What neurotransmitters do adrenergic receptors use?

epinephrine and norepinephrine

Alpha-1 adrenergic receptors

excitation (vasoconstriction) of blood vessels in skin and visceral smooth muscles

Alpha-2 adrenergic receptors

inhibits digestion

beta-1 adrenergic receptors

excites cardiac muscle (inc. HR)

beta-2 adrenergic receptors

inhibits smooth muscles of respiratory tract, causing relaxation (airway diameter increases)

beta-3 adrenergic receptors

excitatory effects on adipocytes which releases lipids into the blood

• increases ATP synthesis

sympathetic postganglionic axons release what neurotransmitter onto effectors?

ACh or nitric oxide (NO)

What are varicosities?

enlargements within the sympathetic postganglionic NE axons filled with NE

what do sympathetic varicosities do?

strengthen effect of activation to certain areas more than others when released

speed of NE removal after varicosity release

slow

how is NE removed after being released

• reup taken or reused

• broken down by MAO and COMT in surrounding tissue and liver

NE stimulates more _____ receptors

alpha

epinephrine stimulates ____ receptors

both alpha and beta receptors

localized sympathetic activity from NE release at varicosities affects primarily

alpha receptors near the active varicosities

Generalized sympathetic activity and release of E by adrenal medulla affect

alpha and beta receptors throughout the body

alpha adrenergic receptors are activated by what neurotransmitter(s)?

NE and E

Alpha 1 receptors are found

throughout the body

examples of alpha 1 receptor effects

vasoconstriction (which increases HR) and sphincture closer along digestive tract (shuts down movement chamber → chamber)