CVS case study questions

Question 1

What causes the peak of depolarisation at the start?

Answer 1

Influx of Na+

- T tubule membrane depolarised

Question 2

What ion is most important for standing membrane potential?

Answer 2

K+

Question 3

What happens to force of contraction when there is sympathetic stimulation of the heart? and why?

Answer 3

INCREASEs

• due to increases in CO and HR.
• The activity causes faster depolarisation of the SAN causing a faster HR.
• This is caused by the noradrenaline binding to beta 1 adrenergic receptors causing cAMP increase, activating PKA.
• This then phosphorylates the L-type channels and the SR releases channels.
• Ergo, this leads to an increased (ca) binding to troponin C, and therefore more cross bridges form.

Question 4

What occurs in exercise to lead to an increase in CO?

Answer 4

Activity of skeletal muscles, leading to increased venous tone, pressure and return.

• This increases the EDV, preload and the SV.
• This increases CO, causing increased sympathetic activity and adrenaline, and increased venoconstriction and HR.

Question 5

Why does venous return lead to increased CO?

Answer 5

Increased venous return, more blood to atria, increased EDV, increase preload, increased SV (due to Starling’s law) causing increased CO.

Question 6

State 2 “western” lifestyle factors that contribute to atherosclerosis

Answer 6

Smoking and Obesity

Question 7

Name 2 of the 3 cells involved in atherosclerosis

Answer 7

• Vascular smooth muscle cells
• Macrophages
• Vascular endothelial cells

Question 8

Name 2 non-modifiable risk factors for atherosclerosis

Answer 8

• Age
• Race
• Gender

Question 9

Describe 3 ways in which changes in arterial wall in atherosclerosis can lead to clinical problems

Answer 9

• Embolism: occlusion of a small vessel at a distant site
• Thrombosis
• Stenosis

Question 10

Name 2 ways in which vascular smooth muscle cells contribute to the stability of the plaque

Answer 10

• Increases collagen synthesis, forming a fibrous cap, increased matrix deposition.
• Increased thickness of the smooth muscle around the plaque to prevent rupture.

Question 11

Aside from skeletal muscle, name 2 other vascular beds to which vasodilation occurs in exercise

Answer 11

• Coronary vessels

- Bronchial mucosa etc