15CHAPTER 15: AUTONOMIC NERVOUS SYSTEM Flashcards
What is the general function of the sympathetic and parasympathetic ANS?
S= fight or flight
P= Rest and digest
Whats the difference in heart activity between the sympathetic and parasympathetic ANS?
S= increases HR, increases strength of contraction P= decrease HR, and strength of contraction
What is the difference in the digestive system between the sympathetic and parasympathetic ANS?
S= decreases blood flow, P= increases motility and secretion
What is the difference in the urinary system between the sympathetic and parasympathetic ANS?
S= decreases blood flow P= micturition reflex
What are the actions of blood vessels in the sympathetic and parasympathetic ANS?
S= stimulation = vasoconstriction = decrease in blood flow P= none
Where is the sympathetic and parasympathetic ANS located?
S= thoracolumbar P= craniosacral
Which ANS is responsible for maintaining homeostasis?
Both, sympathetic and parasympathetic ANS
Which ANS has background rate of activity causing autonomic tone?
Both, sympathetic and parasympathetic ANS
Neural pathways have what 2 neurons that come from the spinal cord and arrive at the target?
Preganglionic and postganglionic neurons
What are preganglionic neurons?
Cell body in spinal cord or brainstem
What are postganglionic neurons?
Cell body in autonomic ganglion or near the target
Where does the Sympathetic NS arise from?
the thoracolumbar location of the spinal cord.
In the SNS, short preganglionic myelinated neurons are with cell bodies located where?
in the lateral horn of gray matter in spinal cord
In the SNS, where does the axons travel?
Axon travels in spinal nerve and then communicating ramus (white) to the sympathetic chain ganglion
What is the ratio of preganglionic and postganglionic neurons in the SNS?
1:17
From the sympathetic chain ganglion, what are the 3 pathways are possible for the ganglionic/postganglionic fibers?
- Spinal nerve route
- Sympathetic nerve route
- Splanchnic nerve route
What occurs in the spinal nerve route?
Preganglionic fibers synapse on postganglionic neurons in sympathetic chain ganglia = postganglionic fibers go back into spinal nerve via gray communicating ramus = take signal to skin, blood vessels, sweat glands etc.
What occurs in the sympathetic nerve route?
Preganglionic fibers travel up (or down) the sympathetic trunk, synapse on postganglionic neurons in ganglia at other levels = postganglionic fibers take signal to heart, lungs, pupils, glands
What occurs in the splanchnic nerve route?
Preganglionic fibers go through the chain without synapsing and continue as splanchnic nerves to synapse with postganglionic neurons in collateral ganglia (2nd set of ganglia) = postganglionic fibers take signal to digestive, reproductive, urinary organs
Where can you find the adrenal glands?
Sits on top of kidneys
What does the adrenal cortex secrete?
Steroid hormones
What does the adrenal medulla contain?
Contains modified sympathetic ganglion (postganglionic neurons without dendrites or axons)
The preganglionic neuron stimulates modified postganglionic neurons to release what?
Hormones into blood
Where does the parasympathetic NS arise from?
The craniosacral location
In the PNS, long preganglionic neurons, with cell bodies in brainstem (midbrain, pons, and medulla) or sacral spinal cord (S2 – S4) synapse with what and where?
Short postganglionic neurons in terminal ganglia near target organ
In the PNS there are short postganglionic neurons with cell bodies located where?
Near the target
What is the ratio of preganglionic and postganglion neurons in the PNS?
1:2
What are the 4 cranial nerves that are controlled by the PNS?
Oculomotor (III), facial (VII), Glossopharyngeal (IX), vagus (X)
What is the enteric nervous system specific to?
The digestive tract
Does the enteric nervous system arise from the brain or spinal cord?
Neither
What does the enteric nervous system regulate?
Regulated motility
What is the enteric nervous system regulated by?
ANS
What are the 2 types of fibres in the ANS?
Cholinergic fibers and adrenergic fibers
What does adrenergic fibers secrete?
Secrete (NE), excitatory/inhibitory
What do cholinergic fibers secrete?
Secrete (ACh), excitatory/inhibitory
What are the types of receptor found in sympathetic and parasympathetic divisions?
Cholinergic receptors, Adrenergic Receptors (Sympathetic NS only)
What are the 2 types of Ach receptors?
Nicotinic and muscarinic receptors
What do nicotinic receptors do?
Opens ligand-gated ion channel
Where are nicotinic receptors located?
At neuromuscular junctions and on postganglionic neurons of ANS
What is the action of nicotinic receptors?
Excitatory Curare (poison) blocks nicotinic receptors = flaccid paralysis (decreases thoracic muscle contraction = suffocation)
What is a muscarinic receptor?
G protein coupled receptors – second-messenger systems
Where are muscarinic receptors located?
Neuromuscular junctions and on postganglionic neurons of ANS
What is the action of muscarinic receptors?
Excitatory Curare (poison) blocks nicotinic receptors = flaccid paralysis (decreases thoracic muscle contraction = suffocation)
What are the 2 classes of Adrenergic Receptors?
Alpha (α and Beta (β
What action does alpha and beta classes of the adrenergic receptors do?
Alpha= usually excitatory Beta= usually inhibitory
What happens when B1 (beta 1) receptors are blocked?
Decreases strength of heart contraction and decreases HR
What happens when B2 (beta 2) receptors are blocked?
Vasoconstriction of heart vessels = decrease in blood flow
What is propranolol and why is it prescribed?
A beta-blocker, prescribed to reduce hypertension (high BP)
What is dual innervation?
One target receives both sympathetic and parasympathetic input
What can dual innervation can be?
Antagonistic (pupil diameter)
Cooperative (salivation)
What is it called when blood vessels increase firing?
Vasoconstriction
What is it called when blood vessels decrease firing?
Vasodilatation
What does the limbic system provide?
pathway connecting mental experience with ANS
Hypothalamus (major control of ANS) acts as a bridge between what?
the brain and ANS
The Midbrain, Pons, and Medulla have nuclei for what cranial nerves in what division?
Cranial nerves III, VII, IX, X of the parasympathetic division
What does the hypothalamus coordinate?
Coordinates many ANS activities-BP, HR, vasomotion, GI tract motility and secretion
What autonomic reflexes does the spinal cord integrate?
micturition and defecation
