Lecture 19: Autonomic Nervous System Flashcards
(60 cards)
What can the ANS control in general?
Visceral function rapidly and intensely
The ANS pathways typically consists of what two neurons in sequence?
Preganglionic neuron and postganglionic neuron
Describe preganglionic neurons
Cell bodies are located within CNS
Axons are myelinated
Neurotransmitter is ACH
Describe postganglionic neuron
Cell bodies are located in peripheral ganglia
Axons unmyelinated
Neurotransmitter is ACH (parasym) or norepinephrine (symp)
How does the ANS generally transmit its effector functions to the organs they innervate?
Its like a cloud of neurotransmitters released to the general area. Dont form complex releationships with effector structures.
Most parasympathetic and almost all sympathetic postganglionic fibers merely touch or pass near to the effector cells. Terminal ends of these fibers usually have enlarged varicosities where neurotransmitter and large numbers of mitochondria are stored.
Where does the cell body of each sympathetic preganglionic neuron lie?
In the intermediolateral horn of the spinal cord
Thoracolumbar (T1-L2)
(sympathetics) Preganglionic fibers can synapse with postganglionic neurons upward or downward in what?
The paravertebral chain
Preganglionic fibers can pass for variable distances through the paravertebral chain and then through one of the sympathetic nerves to synapse where?
in the peripheral sympathetic ganglion
Describe postganglionic sympathetic fibers
Pass through the gray rami
Type C fibers
Make up about 8% of the fibers in the average nerve
Control blood vessels, sweat glands, piloerector muscles
Describe secretory cells of the adrenal medulla
They are modified postganglionic neurons that have rudimentary fibers that secrete epinephrine and norepinephrine
What stimulates the adrenal medullae?
sympathetic system
How much epinephrine and norepinephrine do the adrenal medullae secrete?
80% epinephrine
20% norepinephrine
Do hormones or neurotransmitters last longer?
Hormones last 5-10 times longer
What does circulating norepinephrine do?
Constricts most of the blood vessels of the body
Greater effect on raising arterial pressure
Increases heart activity
Inhibits GI tract
Dilates pupil
What effect does circulating epinephrine have on the body?
Raises arterial pressure to a lesser extent than norepinephrine
Increases cardiac output MORE than norepinephrine
has a 5-10 times as great effect on metabolism as norepinephrine
Can increase metabolic rate of whole body by as much as 100% above normal
What occurs during a fright or flight response?
Increased arterial pressure Rerouting of blood flow to active muscles Increased rates in cellular metabolism Increased blood glucose concentration Increased glycolysis in liver and muscle Increased muscle strength Increased mental activity Increased blood coagulation rate
About 75% of all parasympathetic fibers are in what?
The vagus nerve
Most parasympathetic preganglionic fibers pass all the way to what?
To the organ that is to be innervated
Describe postganglionic parasympathetic fibers
Located in the wall of the organ
Use Ach as their neurotransmitter
How is acetylcholine made?
Acetyl-CoA + Choline -> acetylcholine
choline acetyl-transferase
How is acetylcholine broken down?
By acetylcholinesterase
Breaks down into choline + acetate ion
How is norepinephrine synthesized?
Hydroxylation of tyrosine to dopa
Decarboxylation of dopa to dopamine
Transport of dopamine into vesicles
Hydroxylation of dopamine to norepinephrine
How does 80% of norepinephrine in the adrenal medulla form epinephrine?
It is methylated to form epinephrine
How is norepinephrine removed?
Reuptake
Diffusion
Destruction by monamine oxidase (found in nerve endings)
Destruction by catechol-O-methyl transferase (present in all tissues) COMT
