DSA & CIS: Autonomics Flashcards
Somatic reflex
sensory information goes back to the spinal cord via a fiber, which will enter the SC via a DRG and synapse directly onto an alpha motorneuron
Goals of the sympathetic nervous system
(fight or flight)
need to get oxygen to the right parts of the body, direct the blood to the right tissues, need more fuel into the muscles, eyes need to see clearly to visualize threats, decrease ability of the liver to store glucose (glucogenolysis), increase lypolysis by adipose tissue
parasympathetic nervous system
(rest and digest)
do not need as much oxygen as the tissues (slow HR down), storage of stuff being ingested, need food to be directed to the digestive tract
What is the NT released by pre-ganglionic fibers in PARASYMPATHETIC NS?
Acetylcholine (Ach)
What is the mechanism of Ach?
Ach binds to nicotinic AchR (nAchR) in the post ganglionic dendrites, this allows sodium into the post ganglionic cell which causes it to depolarize
Post-ganglionic synapse in parasympathetic NS?
synapse between the parasympathetic post-ganglionic neuron and the target
similar to first synapse where Ach is released from the post ganglionic neurons, difference is that the receptor that binds Ach is a MUSCARINIC CHOLINERGIC receptor which activates 2nd messenger system
Post-ganglionic synapse in sympathetic NS?
NT released by post-ganglionic axon is norepinephrine (NE)
What are the 2 receptors NE can bind to?
- alpha adrenergic and beta adrenergic receptors
- these are metabotropic receptors that activate second messenger systems
Different effects of NE binding to receptors?
- alpha adrenergic: cause vasoconstriction of smooth muscle
- beta adrenergic: cause vasodilation of the blood vessels
what happens when there is an increase need for oxygen in the tissues?
- bronchodilation occurs via B2 adrenergic receptors
- increase oxygen to the lungs
- decrease secretion from glands
How do you increase cardiac output?
increase oxygen to tissue lead to an increase in activity in ventricular myocytes, which will activate beta adrenergic receptors, which increases calcium in myocytes which increases cardiac output
How do you increase the heart rate?
with increase oxygen need int he tissues, there is an increase in the activity of the SA/AV node, which increases the activity of B-1 receptors, this influences phase 4 of the AP - funny sodium channels open and increase depolarization which increases heart rate
What are the effects of needing to direct blood to the right tissues during sympathetic response?
increase blood in skeletal muscle, redirect blood where it needs to be and away from gut, kidneys and salivary glands, brain/heart/lungs blood flow is activity dependent
How does blood flow increase?
increase blood to skeletal muscle leads to an increase in sympathetic activitation, which increases B2 receptors to dilate in smooth muscle which increases blood flow
alpha receptor activity in muscle
constriction
B2 activity in SM
relaxation
What leads to pupil dilation?
alpha 1 adrenergic fibers activate, constriction happens in the eye muscles
How does one increase ability to see from afar?
Relax the ciliary muscle to increase far vision, B2 receptors are activated, flattening of the lens which leads to an increase in ability to see from a distance
Effects of sympathetic NS on glucose in liver/skeletal muscle
increase glycogenolysis from the liver, increase glucose into the skeletal muscle, alpha and beta receptors are activated
Effects of sympathetic NS on glucose in adipose tissue
beta receptors are activated, liploysis occurs, increase of free fatty acids int the blood which allows the rest of the body to function
Effects of sympathetic NS on glucose in the pancreas
decrease insulin via alpha receptors
if it has receptors what does that usually mean
sympathetic NS is acting
What happens to motility in the GI during sympathetic NS?
decrease motility via B2 receptors, relaxation fo smooth muscle
Sphincters in the GI during sympathetic response?
increase contraction of the smooth muscle via alpha 1 receptors, decrease movement of contents in the GI, decrease digestion
secretion in the GI during sympathetic response?
in many cases there is a decrease in blood flow to the glands thus a decrease in secretion which is reinforced by the alpha receptors
