Ch. 15 - ANS Flashcards
What is autonomic tone?
regulation of balance bt sympathetic and parasympathetic activity by the hypothalamus
What are some examples of sympathetic responses?
- dilation (enlarging) of pupils
- increased HR, BP, contraction force
- decreased blood flow to non-essential organs
- increased blood flow to sk/card muscle
- airways dilate and resp rate increases
- blood glucose level increases
Why do blood glucose levels increase during a fight-or-flight response?
requires increased ATP production to deliver energy to skeletal muscles
What are some examples of parasympathetic responses?
- salivation, lacrimation, urination, digestion, defecation
- decreased HR, pupil diameter & airway diameter
Where are the cell bodies of sympathetic preganglionic neurons located?
lateral grey horns of the spinal cord (T1-L2)
What is another name for the sympathetic nervous system?
thoracolumbar division
Where is the site of synapse of preganglionic and postganglionic neurons in the symp NS?
ganglia in PNS
What is the difference between trunk ganglia and prevertebral ganglia?
TRUNK - lie on either side of spinal cord
PREVERTEBRAL - lie anterior to spinal cord
What are the 4 different options for sympathetic postganglionic cells? (what can the pre axon synapse wit?)
- postganglionic neuron in chain ganglion at same level
- postgangionic neuron in chain ganglion at higher/lower level
- postganglionic neuron in prevertebral ganglion
- chromaffin cells in adrenal medulla
Describe the structure of (myelinated) preganglionic cells in the sympathetic nervous system
- axons of preganglionic cells leave SC through anterior root of spinal nerve
- axons enter white ramus (short pathway)
- connext to ganglia of sympathetic chain via white rami communicantes
Describe the structure of (unmyelinated) postganglionic cells in the sympathetic nervous system
- unmyelinated postg axons enter grey ramus that merges with spinal nerve
- connect ganglia to spinal nerves via grey rami communicantes
- then supply peripheral viseral effector organs!
Why are postganglionic axons long in the sympathetic nervous system?
to travel far to the effectors; preG are short because they are closer to the spinal cord
How are splanchnic nerves formed?
from preganglionic cells that extend to prevertebral ganglia without synapsing in the sympathetic trunk
How do chromaffin cells secrete hormones from preganglionic neurons?
sphalnchnic nerves synapse with chromaffin cells of adrenal medulla and secrete 80% E/20% NE in bloodstream
What are chromaffin cells?
modified postganglioni neurons in the adrenal medulla that lack dendrites and axons
Where are parasympathetic preganglionic cell bodies found?
- CN III, VII, IX, X
- lateral grey matter of S2-S4 of spinal cord (sacral region)
What is another name for the parasympathetic nervous system?
craniosacral division
Describe the structure of an emerging parasympathetic ganglia
- preG axons emerge as part of cranial nerve OR
- part of a sacral spinal nerve that forms a pelvic splanchic nerve
Where do preganglionic neurons synapse with postganglionic neurons?
terminal ganglia near (or in wall of) effector organ
Why postganglionic axons short in the parasympathetic nervous system?
to be closer to their effectors; preG are long as they start from cranial nerves or sacral region
What do parasympathetic neurons have in place of plexuses to allow for localized responses?
preG neurons synapse with only 4-5 postG axons in terminal ganglia that supply the same effector
Which neurons are cholinergic?
- all preganglionic S/PS neurons
- all postganglionic PS neurons
- S postganglionic cells to sweat glands
Is ACh excitatory or inhibitory to postsynaptic cells?
can be either depending on receptor type and cell involved
What are the 2 types of cholinergic receptors?
nicotonic and muscarinic
What does the activation of nicotinic receptors lead to?
excitation of postsynaptic cell
Where are nicotinic receptors found?
dendrites and cell bodies of ANS postG neurons, chromaffin cells, and sarcolemma of skeletal muscles (NMJ)
What does the activation of muscarinic receptors lead to?
either excitation or inhibition, depending on the cell
Where are muscarinic receptors found?
parasympathetic effectors, sweat glands
Which neurons are adrenergic?
most postganglionic S neurons
What does the activation of adrenergic neurons lead to?
excitation or inhibition of postsynaptic cell depending on receptor type and cell involved
Compare the length of effects triggered by adrenergic neurons to cholinergic neurons
adrenergic - typically longer lasting, takes longer for response to go away bc NE lingers at synapse
What are the 2 main types of adrenergic receptors?
alpha and beta receptors
Examples of clinical use for muscarinic ACh receptor agonists
stimulate parasympathetic NS
- treat dry mouth
- stimulate gut motility after surgery
Examples of clinical use for muscarinic ACh receptor antagonists
block receptors; prevent responses from parasympathetic NS
- dilate pupils during ophthalmologic exams
Examples of clinical use for adrenergic receptor agonists
- treat anaphylactic shock (E stimulates sympathetic NS, cause BV to dilate)
- promote bronchodilation in patients with asthma
Examples of clinical use for adrenergic receptor antagonists
- treat hypertension (lower BP)
- protective following myocardial infarction (helps relax heart to not pump as hard)
What are the input and output to the hypothalamus?
input - emotions, visceral sensory info
output - to nuclei in brainstem and SC (preG neurons)
