Physiology of ANS (Karius) Flashcards
What is a reflex arc?
Relays sensory (Afferent) info from the skin to the CNS, specifically the spinal cord.
In the spinal cord, the afferent fiber synapses with a motor neuron that innervates the muscle that is being stimulated (by fire, AH!)
How does an autonomic visceral reflex arc happen?
stimuli from:
visual/auditory cues
baroreceptors
stretch receptors
chemoreceptors
etc.
Key: processed in the hypothalamus instead of the spinal cord
goes in by afferent neuron, comes out via ANS
Describe the pre-synaptic and post-synaptic neurons in the autonomic reflex arc
presynaptic neuron: cell body is in the CNS, terminates as ganglion in periphery
postsynaptic neuron: cell body is in the ganglion, terminates in the organ
Thus: Two synapses, one in the ganglion, and one in the organ
The first synapse between the presynaptic and postsynaptic neurons is where?
in the ganglion!
essentially, the same between sympathetic and parasymapthetic systems
The presynaptic axon releases Ach at its synapses between the pre and post synaptic neurons
What is the postsynaptic neuron expressing at the postsynaptic membrane?
nicotinic cholinergic receptors!
The second synapse between the presynaptic and postsynaptic neurons is located where?
At the end organ!
it is different depending on if you are talking about sympathetic or parasympathetic
What is significant about vericosities?
They contain all of the components of the presynaptic terminal (vesicles with NTMs, mitochondria, etc) and work the same way as the presynaptic terminal of the NMJ, but they are in the second synapse of the autonomic NS.
The postsynaptic side has ligand gated receptors that are more spread out, not clustered in teh presynaptic terminal.
What NTM is released from postsynaptic axon at the end organ?
What does it bind to?
ACh
muscarinic cholinergic receptor on the target cells
What is significant about muscarinic receptors?
- Ach binds and activates these receptors
- Exogenous muscarine binds to them, but does not activate nicotinic receptors, and nicotine does not activate muscarinic receptors
- part of the metabotropic (serpentine) family of receptors with second messenger systems
Describe M1R
Found in the CNS, not autonomic, plays a role in memory
increases salivary secretion
aids stomach secretion
Gq/11, increases IC Ca
Describe M3R
Smooth muscle cell contraction
Exocrine gland secretion
Gq/11, increases IC Ca
Describe M5R
Describe M4R
Found in CNS
role unclear
Role unclear
Describe M2R
Cardiac-slows heart rate works on SA node
Gi/o, K+ leaves cell, repolarizes/hyperpolarizes cell, that’s how it slows HR.
What effect must M2R have on K channels in order to slow the heart rate
sympathetic NTM released from the postsynaptic neuron on the end organ is?
What does it bind to?
Norepinephrine
Adrenergic receptors
What is special about adrenergic receptors?
member of serpentine family of receptors
has second messenger systems that are activated upon norepi. or epi. binding to them
two classes: alpha-adrenergic and beta-adrenergic
Describe alpha1 adrenergic receptors
Gq/11 coupled
lead to increase in IC Ca+
located on: smooth muscles of BV (contraction), GI/GU
liver (glycogenolysis, gluconeogenesis)
adipose tissue (lipolysis)
lacrimal gland (reduce tears)
radial muscle of iris (pupil dilation)
Describe alpha2-adrenergic receptors (fight or flight)
alpha-2 receptors
Gi/o coupled
lead to decrease in adenylate cyclase/cAMP
located on:
constrict GI sphincters
pancreas (increase glucagon, decrease insulin)
smooth muscle of BV (dilate)
platelets (increase clotting)
Describe beta1 adrenergic receptors
Gs coupled
increases adenylate cylcase/cAMP
found in:
SA node, increases HR
ventricular muscle, increases contraction strength
salivary gland, increases viscosity
adipose tissue, lipolysis
Describe beta2 adrenergic receptors
Gs coupled
increase adenylate cyclase and cAMP
found on:
bronchiole smooth muscle (relax)
GI smooth muscle (relax)
GI/GU (relax)
vascular smooth muscle (relax)
liver (glycogenolysis)
eye (relaxes/flattens lens)
Describe beta3 adrenergic receptors
Gs coupled
increases adenylate cyclase and cAMP
found on:
white and brown adipose
lipolysis and thermogenesis
What role does the adrenal medulla play in the sympathetic system?
contain chromaffin cells that make and release epinephrine as part of the sympathetic response
some sympathetic axons go through the ganglion and synapse on the adrenal medulla instead of the paravertebral gangion.
What does the presynaptic axon do at the adrenal medulla?
the presynaptic axon releases Ach which binds to nicotinic receptors on the chromaffin cells
this acticates the receptors which leads to a release of epinephrine into the blood
Describe the general effects of the parasympathetic response
Rest and Digest
- plenty of O2
- slow HR
- BP low
- intestines getting blood
- getting fuel from GI tract
Describe the general effects of the sympathetic response
Fight or Flight
- need lots of O2
- need O2 in muscles
- don’t need to digest (because dead people don’t need food)
- need enough fuel for the moment, not for later
Parasympathetic Characteristics
Exit CNS:
Location of Ganglion:
Length of pre-synaptic axon:
Length of post-synaptic axon:
cranial and sacral nerves
on/near the target organ
long
short
Sympathetic Characteristics
Exit from CNS:
Location of ganglion:
Length of presynaptic axon:
Length of post-synaptic axon:
thoracic and lumbar
sympathetic chain
short
long
Synapse 1 Parasympathetic and Sympathetic
NTM released: Ach
receptor: Nicotinic cholinergic
Synapse 2: Parasympathetic
NTM: Ach
Receptor: muscarinic cholinergic
Norepinephrine is released by
NERVES
Second Synapse: Symphathetic
NTM: Norepi
Receptor: alpha and beta adrenergic
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