Lecture - CVS (Rajesh - Physiology 10 Integration)

Question 1

Arterial baroreceptor reflex

1. What are the sensors and where are they located?
2. Their afferent fibres travel in what nerves?
   - What cranial nerves are they?
   - Where do they go to?
   - What is the name of the thing it travels to?
3. There is _____ ______ in both the ______ nerves from the baroreceptors and in the ______ _______ and ________ nerves.
   - What does this mean?
4. So what happens to the activity in the baroreceptor afferent fibres when the pressure (a) rises and (b) falls
5. When the pressure rises, you will increase the activity in the afferent fibres. What will happen to the parasympathetic/sym activity to the heart and BV?
   - So what’s the consequence of this? There are three different objects that will be affected to change something overall
6. Why are the baroreceptors known as ‘pressure buffer’ system?

Answer 1

5. Three things: vasodilation, venocontriction and decrease HR + contractiltiy to all reduce CO and TPR so you decrease MABP
6. Because they play a key role in controlling minute-minute pressure changes

Question 2

Arterial baroreceptor reflex maintaining: Posture

1. So BV aren’t rigid and _______ will be a determinant of the pressure blood exerts on the walls of BV. What veins (that tend to be distended) are in the ‘dependent’ regions of the body?
2. In supine position, what is the relationship between the vessels and the heart?
   - What about standing?
   - So what happens to the blood in the veins and the central venous pressure?
3. Can you go through the orthostatic hypotension sequence, pls and ty - like what happens when you stand up after sitting or lying down?
4. Now explain what happens in terms of the baroreceptor reflex response when you stand up (to preserve the cerebral perfusion) - there are 4 different things affected

Answer 2

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Question 3

Arterial baroreceptors maintaining: Exercise

1. There are 4 different demands that the CVS must achieve in exercise - what are they and how are they met?
   - very logical, what do you need in exercise? How will you get it around? Where do you need to get it to? What should you keep stable despite these changes?
2. If you increase pulmonary blood flow, what happens to the CO? (this is so logical, it’s like one route from RV to lungs to LV…)
3. In exercise, what three things increase the HR?
   - What will happen to the SV? How does that happen (also 3 things)
   - What is ejection fraction and how does it change during exercise (so three things chanege during exercise: HR, SV and EF)
4. What four things will increase venous return during exercise?
   - WHat happens if the venous return doesn’t increase during exercise?
5. So most of the increased CO goes to te exercising muscles. The vasodilation of the resistance vessels to the exercising vessels is due to what 3 things? (slide 27)
6. On slide 25 is a flow diagram explaining the symapthethic tone being activated by exercising skeletal muscles - talk through it
   - what happens to the capilliaries during exercise and how does it relate to diffusion?
7. Explain the blood flow to skin during the course of the exercise (or fever)
   - now explain this vasodilation and sweating in terms of the sympathetic stuff
8. Haemodynamically, tell me about the changes to these:
   - skeletal muscle BF
   - MABP
   - systolic arterial pressure
   - diastolic arterial pressure
   - TPR
   - CO
   - HR
   - SV
   - EDV

Answer 3

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Question 4

Baroceptors trying to maintain MABP during blood loss/haemorrhage

1. As a brief idea of percentages, how much blood is lost during donation? What about when you go into clinical shock? How much loss may cause severe and sometimes irreversible shock?
2. SO how do you go from haemorrahge to haemorrhage shock? How does haemorrhage lead to drop in arterial BP?
3. Now, the CVS responds to the blood loss in three ways - what are the three and how long do they work for?
4. So the immediate response is on slide 41 - try to draw it out
5. So the intermediate response is to restore the circulating volume:
   - where does this fluid come from
   - what’s more important: ideal blood compositon or fullness of the vessels
   - from slide 43, recite to me what’s going on
6. The long term response to the haemorrahge is to replace what?
   - what does decreased renal prefusio trigger?
   - what does this substance that’s released do?
   - so over how long oes the total body lost water and salt be replaced?
   - Long term you also need to replace two other things which take around ____ weeeks - what are they?

Answer 4

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