Autonomic Nervous System Flashcards

1
Q

Which neurotransmitters does the adrenal medulla release?

A

It releases adrenaline, noradrenaline, and dopamine

Are all catecholamines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does the parasympathetic & symapthetic NS target?

A

smooth muscle, cardiac muscle, and glands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Outline the innervation of blood vessels in the sympathetic nervous system

A
  • Sympathetic neurons are tonically active & will release norepinephrine onto the a-adrenergic receptor
  • This causes a change in signal rate
  • Increase in norepinephrine = blood vessel constriction
  • Decrease in norepinephrine = blood vessel dilation

Blood vessel constriction –> so we increase the blood pressure and get more venous return

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Outline the neural supply of pupillary constrictor and pupillary dilator muscles

A

Pupillary constrictor (parasympathetic supply): Edinger-Westphal nucleus –> III cranial nerve –> ciliary ganglia –> pupilloconstrictor muscle in iris

Pupillary dilator (sympathetic supply): Preganglionic neurons found in spinal cord –> synapse onto superior cervical sympathetic ganglion –> post-ganglion neuron goes to supply the pupillodilater muscle in iris

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Outline the sympathetic innervation of the heart

A
  1. In the spinal cord in the intermediolateral cell column, there are preganglionic neurons taht synapse with a postganglionic neuron
  2. Synapses onto ganglia near the heart
  3. Noradrenaline released onto a B1-receptor
  4. Activates Ga protein
  5. Activates cAMP
  6. Na+ and Ca2+ enter
  7. Causes depolarization of the** SA node**
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Outline the parasympathetic innervation of the heart

A
  1. The preganglionic neuron in brainstem exits via 10th cranial nerve
  2. ACh released onto a muscarinic receptor
  3. Ga (inhibitory) activated that decreases cAMP
  4. Na+ and Ca2+ entry decreases
  5. The beta & gamma subunits increase activity of K+ channel
  6. Reduced depolarization and cell takes longer to reach threshold
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens to cardiac activity in response to a decrease of blood flow to the brain?

A
  • Sympathetic nerve activity increases
  • TPR increases
  • Stroke volume, heart rate, and cardiac ouput increase
  • Arterial pressure increases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

An increase in exercise results in a rise in cardiac output. How does this affect blood supply to different organs?

A
  • Blood supply to liver, kidneys, bone, and other tissues decreases
  • Blood supply to heart, skeletal muscle, and skin increases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does addition of glycine to system affect arterial pressure?

A
  • Drops
  • Integrated renal sympathetic activity drops too

Glycine has been shown to increase the production of nitric oxide (NO) in endothelial cells. Nitric oxide is a vasodilator, meaning it relaxes the smooth muscles of blood vessels, leading to increased blood flow and potentially reduced arterial pressure.

Glycine may also impact renal function, potentially influencing fluid and electrolyte balance, which are key determinants of arterial pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

In order to determine whether the spinal cord is involved in autonomic functions, scientists injected a dye into the dorsal root ganglion which filled up the spinal root afferents. They then took a piece of distal colon and cut it. Using a microscope, what did they observe?

A
  • They observed the ends of the afferents in the mucosa
  • These afferents contained an ion channel that opens when it is deformed (Piezo-2 channel) in response to mechanical distension of the lumen of the colon
  • These afferents were spread out over a large region and were sparesly innervating the colon

Spinal visceral afferents send info that you perceive about organs, whereas cranial visceral afferent send info about the functions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is referred pain?

A
  • when you have an injury in one area of your body but feel pain somewhere else
  • you may receive nerve from heart AND skin - overlapping of neurons can cause pain to be more dispersed

Random note: sensory visceral afferents sense MECHANICAL and CHEMICAL and TEMP stimuli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where are the cell bodies for cranial visceral afferent found?

A
  • the odose / inferior ganglion of the vagus
  • the jugular / superior ganglion of the vagus
  • petrosal ganglion

The primary central termination site for cranial visceral afferents is the NTS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are 2 sites that contain baroreceptors?

A

aortic arch
carotid sinus

sensory nerves like the VAGUS nerve and the CAROTID SINUS nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Distinguish b/w A-fibers and C-fibers

These are the 2 classes of baroreceptor afferents that will respond to stretch / heart pressure

A
  • A fibers are myelinated whereas C fibers are not
  • A fibers about 10% whereas C fibers around 90%
  • A fibers active at rest whereas C fibers have a very high threshold (activated at HIGHER blood pressure)
  • A fibers have synchronous glutamate release whereas C fibers have asynchronous glutamate release

C fibers express TRPV1

The activation thresholds for myelinated fibers are much broader (spread over a larger range, although lower) compared to unmyelinated fibers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do baroreceptors respond to low blood pressure in the aortic arch receptor vs the carotid sinus receptor

A

1) signal passes along vagus nerve for the aortic arch receptor
2) signal passes along Nerve IX (glossopharyngeal) nerve for carotis sinus receptor
3) Both synapse onto NTS
4) Release of glutamate at NTS
5)** Pathway 1 = nucleus ambiguous (AMB); cells of AMB exit via VAGUS nerve and SLOW the heart**
6) Pathway 2 = caudal ventral lateral medulla (CVLM)

In pathway 2, CVLM sends projections to RVLM (rostral ventral lateral medulla) –> this drives sympathetic nerve activity –> increases HR and constricts vessels to pressure rises

If blood pressure is high, GABA is released to inhibit SANS

Also inhibits the intermediolateral column

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Explain the pathway of the cranial viscerosensory afferent neurons

A

Periphery –> vagus nerve –> Xth cranial nerve –> solitary tract –> NTS

Periphery = cardiovascular, respiratory, hepatic, gastrointestinal system (all SENSORS)

The vagus nerve becomes the Xth cranial nerve, then it forms the solitary tract along with the IXth and VII cranial nerves

Integration happens at the NTS

17
Q

Injection of tracing dyes into ganglia known to contain the cell bodies of these neurons (such as the nodose) reveals that their terminal fields are in the NTS. The presence of which protein suggests that they are forming synapses with NTS neurons?

A

Synaptophysin

Synaptic input occurs very close to the axon initial segment where action potentials are being generated - for the anterograde aortic depressor nerve / nodose ganglion labelling

18
Q

Action potentials in the visceral neurons eventually result in . . . . . at the ST-NTS synapse.

A

glutamate release

acts as both AMPA and NMDA neurons

19
Q

What is frequency dependent depression?

A

when subsequent action potentials cannot release enough glutamate to match the first - it is a feature of sensory neurons

20
Q

What are some features of the solitary tract (cranial visceral) input to the NTS?

A
  • A relatively sparse excitatory network where one primary afferent dominates the info pathway
  • Dedicated lines of info (usually involved in homeostasis)
  • Convergent primary afferent input (usually connect to hypothalamus & involved in complex brain processing)
21
Q

Why is capsaicin added to cells?

A

Capsaicin activates the TRPV1 receptor

TRPV1 receptors can also be activated by acid and heat

This channel allows the passage of Na+ and Ca2+; it is involved in nerve cell stimulation

By causing TRPV1 to open, we can inhibit neurons, allowing a lot of Ca2+ to rush in

The cell will become depolarized, but due to the high internal positive charge, it will be very difficult for it to become hyperpolarized to allow another action potential to be fired

22
Q

Cells that can be blocked by capsaicin have. . .

A

asynchronous release

cells that had no capsaicin never had asynchronous glutamate release

23
Q

How does asynchronous release affect excitation?

A

Asynchronous release extends the post-synaptic excitatory period

24
Q

Capsaicin inhibits the activation of 2nd order NTS neurons as evoked by electrical activation of the solitary tract. By what mechanism does this occur?

A

Depolarization block in the presynaptic terminal

25
Q

If capsaicin is added at a very low concentration, how does this help the researchers understand transmission?

A

They can activate the TRPV1 receptor specifically and identify those NTS neurons that they are recording from - what type of sensory neuron is talking to it