Lecture 24: Autonomic Nervous System Flashcards
True or False:
The autonomic nervous system can change visceral function rapidly and intensely.
True
How many seconds does it take for the ANS to increase heart rate to twice as normal?
3-5 seconds
How long does it take the ANS to double arterial pressure?
10-15 seconds
What are the two neurons in sequence in the ANS pathways?
- Preganglionic neuron
- Postganglionic neuron
Where are the cell bodies of preganglionic neurons located?
within CNS
Do preganglionic neurons or postganglionic neurons have myelinated axons?
Preganglionic neurons - axons are myelinated.
Do preganglionic neurons or postganglionic neurons not have myelinated axons?
Postganglionic neurons - axons are NOT myelinated.
What is the neurotransmitter used by preganglionic neurons?
Acetylcholine
What is the neurotransmitter used by postganglionic neurons?
- Acetylcholine in parasympathetic system.
- Norepinephrine (usually) is sympathetic system.
What do postganglionic neurons in the parasympathetic system use as a neurotransmitter?
Acetylcholine
What do postganglionic neurons in the sympathetic system use as a neurotransmitter?
Norepinephrine (usually)
Where are cell bodies of postganglionic neurons located?
Peripheral Ganglia
True or False:
Most parasympathetic and almost all sympathetic postganglionic fibers merely touch or pass near to the effector cells of the organs they innervate.
True
True or False:
Terminal ends of postganglionic fibers usually have enlarged varicosities where neurotransmitter and large numbers of mitochondria are stored.
True
Where does the cell body of each sympathetic preganglionic neuron lie?
In the intermediolateral horn of the spinal cord (T1-L2).
In the paravertebral chain, where can preganglionic fibers synapse?
- Can synapse with postganglionic neurons upward or downward in the paravertebral chain.
- Preganglionic fibers can pass for variable distances through the chain and then through one of the sympathetic nerves to synapse in a peripheral sympathetic ganglion.
Which communicating rami do postganglionic sympathetic fibers pass through?
Gray Rami
What type of fibers are postganglionic sympathetic fibers classified as?
Type C Fibers
What percentage of fibers make up the fibers in the average nerve?
8%
What do postganglionic sympathetic fibers control?
- blood vessels
- sweat glands
- piloerector muscles
Where does the thoracic sympathetic chain lie?
Against neck of ribs and constovertebral junctions.
How many thoracic ganglia pairs make up the sympathetic chain?
> 12 thoracic ganglia pairs:
- first one often fused with inferior cervical ganglion
- referred to as stellate ganglion collectively
What are the 3 cervical ganglia?
- superior
- middle
- inferior
The preganglionic sympathetic supply to the thoracic viscera is from which vertebrae?
T1-5
Where are the postganglionic fibers from that supply the thoracic viscera?
- superior, middle, and inferior cervical ganglia
- T1-T5 paravertebral ganglia
What do preganglionic sympathetic fibers exit the thoracic sympathetic chain as?
Exit the chain as direct fibers and travel downwards to enter the thorax as CARDIOPULMONARY SPLNACHNIC NERVES.
True or False:
The cardiopulmonary splanchnic nerves travel on their own and do not accompany other nerves or vessels.
True
What are the functions of the cardiopulmonary splanchnic nerves?
- coronary artery dilation
- increase heart rate
- bronchodilation
What are splanchnic nerves composed of?
- preganglionic fibers
- visceral sensory fibers
What do splanchnic nerves supply?
Abdominal Viscera
Where do splanchnic nerves synapse?
Prevertebral Ganglia
What are the 3 splanchnic nerves?
- greater
- lesser
- least
Where does the greater splanchnic nerve synapse?
celiac ganglion
Where does the lesser splanchnic nerve synapse?
superior mesenteric ganglion
Where does the least splanchnic nerve synapse?
aorticorenal ganglion
From what vertebral level does the least splanchnic nerve preganglionic fiber arise?
T12
From what vertebral levels does the lesser splanchnic nerve preganglionic fiber arise?
T10-T11
From what vertebral levels does the greater splanchnic nerve preganglionic fiber arise from?
T5-T9
Which nervous system stimulates the adrenal medullae to secrete epinephrine and norepinephrine?
Sympathetic System
What is secreted from the adrenal medulla upon stimulation by the sympathetic nervous system?
- 80% epinephrine
- 20% norepinephrine
How much longer do hormones last than neurotransmitter versions?
5-10 times longer
What effect does circulating norepinephrine have on most blood vessels of the body?
Constricts most of blood vessels of body.
has greater effect on blood vessels in skeletal muscles so has greater effect on raising arterial pressure
What effect does circulating norepinephrine have on heart activity?
Increases Heart Activity
What effect does circulating norepinephrine have on the GI tract?
Inhibits GI Tract
Does circulating norepinephrine constrict or dilate the pupil?
Dilates the Pupil
What effects do circulating norepinephrine have on the body?
- Constricts most of blood vessels of body.
> has greater effect on blood vessels in skeletal muscles so has greater effect on raising arterial pressure - Increases heart activity.
- Inhibits GI tract.
- Dilates pupil.
Are secretory cells of the adrenal medulla preganglionic or postganglionic neurons?
Postganglionic Neurons
What do secretory cells of the adrenal medulla, which are postganglionic neurons, have that secretes epinephrine and norepinephrine?
Have rudimentary fibers that secrete epinephrine and norepinephrine.
Does circulating epinephrine or norepinephrine have a greater effect on raising arterial pressure?
Norepinephrine raises arterial pressure more than epinephrine.
Does circulating epinephrine or norepinephrine increase cardiac output more?
Circulating epinephrine increases cardiac output more than norepinephrine.
Does circulating epinephrine or norepinephrine have a greater effect on metabolism?
Circulating epinephrine has a 5-10 times as great effect on metabolism as norepinephrine.
What percentage above normal can circulating epinephrine increase metabolic rate of the whole body?
As much as 100% above normal.
What is the effect of circulating epinephrine?
- 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.
When does an alarm or stress response occur?
Occurs when there is a mass discharge of the entire sympathetic system (fright, fear, severe pain).
What happens when there is a mass discharge of the entire sympathetic system during an alarm or stress response to fright, fear, or severe pain?
- 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.
What percent of all parasympathetic fibers are in the vagus nerve (CN X)?
75%
True or False:
Most preganglionic fibers pass all the way to the organ that is to be innervated.
True
In the parasympathetic system, where are post ganglionic parasympathetic fibers located?
In the wall of the organ.
What neurotransmitter is used by postganglionic parasympathetic fibers?
Acetylcholine (Ach)