Lecture 13: The role of the CNS in normal CV control

Question 1

Describe the SNS innervation;

Answer 1

1) Premotor neurons originate from primary cirtices
2) Preganglion axon
Prevertabral ganglion (intersynapses)
3) Post ganglion axon
SM or target cell

Question 2

Describe the PNS innervation

Answer 2

Brain region origin
Nerves go to intraneural ganglion
2) Post ganglionic axon

Question 3

Describe the ANS neurotransmitters

Answer 3

SNS; PGA (Ach) Post GA (NE)

PNS; PGA (Ach) Post GA (Ach)

Question 4

Whats special about the preganglion axons?

Answer 4

Always myelinated

Question 5

What does sympathetic activity to the kidney do?

Answer 5

Increases Renin, Vasoconstricts, so decreases BF, Increase salt retention

Increased Renin = increased ANG 2 etc

Question 6

Sympathetic bursts to the heart are in sync with what?

Answer 6

The cardiac cycle

Question 7

How do sympathetic bursts vary?

Answer 7

Sympathetic bursts vary in size depending on how many neurons are firing

Question 8

What is neurogenic shock?

Answer 8

• Sudden loss in SNA
• Usually after spinal cord injury
• Results in loss of vasoconstriction tone, venous pooling, low CO, hypotension, bradycardia

Question 9

How is neurogenic shock treated?

Answer 9

• Inhibit Parasymp?

- Inotropes etc

Question 10

Where does sympathetic activity originate from in the brain stem?

Answer 10

1) paraventriuclar nucleus
2) A5 cell group
3) Nostral Venterolateral Medulla
4) Venteromedial medulla
5) Caudal raphe nuclei

All go through the sympathetic ganglion pre-nuclei

Question 11

In theory how can symp drive be target?

Answer 11

These brain stem regions can be tareted in theory to decrease SNA

Question 12

Does an increase in excitement etc, (stress) cause increased sympathetic drive to heart and increase CV response and possible cause of heart arrhythmias?

Study 1/7 for SNA

Answer 12

Studies found that increased emotional stress, increased sympathetic drive to heart and increased CV events i.e heart attacks

Incidence of heart attacks correlates with warm baths

Question 13

What is differential control of SNA?

Differential control

Answer 13

There are differeing baseline levels of SNA to different organs (differential control)

i.e SNA to heart can increase a lot but SNA to kidney can only increase slightly as its baseline is so high

Question 14

What did simon malpas differential control theory suggest?

Study 2/7 for SNA

Answer 14

• Areas of the brain generate different baseline activity for different SNA targets
• These are modulated by afferent inputs i.e chemoreflex, baroreflex

Question 15

Whats the implications of malpas theroy?

Answer 15

Therefore in response to different stimuli the SNA is going to change variable to different things.

i.e increased BV = decreased SNA to kidney = increased diuresis b/c increased renal blood flow
but no change in SNA to lumbar muscles

Question 16

What happens if you lesion the afferent input brain regions of SNA?

Study 3/7 for SNA

Answer 16

If you lesion the brain regions (regulatory regions) you lose SNA response i.e SNA doesnt change

Question 17

How does ANG 2 influence SNA?

Answer 17

ANG 2 changes SNA to heart and kidney

i.e regulatory factors influence SNA