Physiology Quiz 5 (1/2) (Autonomic Nervous System) Flashcards
What is the Autonomic nervous system?
Efferent outflow controlled by higher centers in the CNS as well as by spinal reflexes
The autonomic nervous system is a subsection of what system?
CNS
Every one of the efferent pathways of the ANS is comprised of what two neurons?
Preganglionic
Postganglionic
Thoracolumbar outflow
Sympathetic division of of efferent outflow from spinal cord
Sympathetic preganglionic fibers are (long/short)
Short
Sympathetic postganglionic fibers are (long/short)
Long
Craniosacral outflow
Parasympathetic division of efferent pathways from spinal cord
Where do preganglionic fibers originate in parasympathetic nervous system?
Brain
The preganglionic fibers in the parasympathetic nervous system are (short/long)
Long
The postganglionic fibers in the parasympathetic nervous system are (short/long)
Short
In the sympathetic system, how many postganglionic fibers are innervated by a single preganglionic fiber?
11-15
In the parasympathetic system, how many postganglionics are innervated by a single preganglionic?
1-3
Divergence
The way a single sympathetic preganglionic fiber innervates 11-15 postganglionic fibers
Point to point control
The way a single parasympathetic preganglionic fiber innervates 1-3 postganglionics; lack of divergence
What is the neurotransmitter at the preganglionic to post ganglionic synapse in both divisions of the ANS
Acetylcholine
What is the receptor type at the preganglionic to postganglionic post synaptic membrane in both divisions of the ANS
Nicotinic cholinergic
Neurotransmitter at the postganglionic to end organ synapse in the parasympathetic nervous system
Acetylcholine
Receptor on the postganglionic post synaptic membrane to end organ in parasympathetic
Muscarinic cholinergic
Neurotransmitter at the postganglionic to end organ synapse in the sympathetic nervous system
Norepinephrine
Catecholamines
Class of compounds produced from tyrosine Eg: Norepinephrine Epinephrine dopamine
Adrenergic receptors
Type of post synaptic receptors for sympathetic system
General classes of adrenergic receptors
Beta (beta 1and beta 2)
Alpha (alpha 1 and alpha 2)
Where are beta 1 receptors found
Surface of cardiac cells and JGA in kidney
Beta 1 receptors are (excitatory/inhibitory)
Excitatory
What happens when beta 1 receptors are stimulated?
Increase heart rate
Increase inotropic state
…therefore increases demand for oxygen
Inotropic state
Contractile force of muscle
Are beta 1 receptors innervated?
Yes
Where are beta 2 receptors found?
Everywhere beta 1 receptors are not found
Beta 2 receptors are (excitatory/inhibitory)
Usually inhibitory
Are beta 2 receptors innervated?
They may or may not be innervated
Myocardial infarction
Inability of system to supply enough oxygen to cardiac tissue
Effects of cocaine
Increases heart rate
Increases inotropic state
Increases catecholamines
Therefore: increases oxygen demand, can cause myocardial infarction
Where are alpha 1 receptors found?
Everywhere
Alpha 1 receptors are (excitatory/inhibitory)
Usually excitatory
Where are alpha 2 receptors found?
Only on the presynaptic membrane of the sympathetic postganglionic fibers
Alpha 2 receptors are (excitatory/inhibitory)
Inhibitory
At all synapses in the parasympathetic system, what is activity terminated by?
Activity of cholinesterases and acetylcholinesterases
JGA
Stands for juxtaglomerular apparatus
Found in kidney
Chain of reactions with this results in increased blood pressure
What do alpha 2 receptors do?
Inhibits release of norepinephrine (does not completely shut down) at presynaptic membrane to prevent overstimulation of synapse
COMT
Enzyme that breaks down catecholamines
Where is COMT found?
Postsynaptic sympathetic membrane and in extracellular fluid
Two things that can happen to norepinephrine as it diffuses across the sympathetic synapse
COMT
or
Attach to receptor on postsynaptic membrane
Three things that can happen to norepinephrine after it releases from receptor
Attach to another receptor
Encounter COMT
undergo active transport into nerve terminal
What can happen to norepinephrine that is actively transported back into the cell?
- Can be repackaged and used again
2. Encounter MAO
MAO
Monoamine oxidase
Chemically alters catecholamines so they are no longer active (breaks down)
What does cocaine do at the synapse
Inhibits active reuptake of norepinephrine at synaptic nerve terminals; increases stimulation at synapse
Clinical use of cocaine
In ophthalmology to dilate pupils
Norepinephrine effect on CNS
Elevates mood
MAO inhibitors
Drug class of depression meds Increases norepinephrine in brain
How pain activates sympathetic response
Pain fibers converge with sympathetic fibers in spinal cord
Spastic bladder
The stretch receptors in bladder wall advise higher centers of need to urinate. When there is damage to spinal cord, you lose this ability and you lose the ability to relax urinary sphincter. “Holding it” can cause increased heart rate, blood pressure, nausea, sweating, headache due to this pathway stimulating sympathetic nervous system. This is an emergency situation
Intermediolateral column
Little bulge off of dorsal horn where nerve cell bodies for sympathetic preganglionic are found (T1-L3)
Where pain fibers stimulate sympathetic system
