CVS 21: Integration of CVS response- Haemorrhage

Question 1

What is the noradrenaline contraction mechanism in the heart?

Answer 1

1. NA binds to a B1 adrenoreceptor
2. increases cAMP
3. activates PKA
   
   • phosphorylation of CALCIUM CHANNEL on membrane–> open for longer and also RyR channel remains open for longer
   • Affects the Ca2+ ATPase & phospholamban. They pump Ca2+ back into the SR so SR is more full of Ca. Force of contraction increases as SR is more full –> greater stroke volume

Question 2

What is the effect of noradrenaline on smooth muscle?

Answer 2

• binds to a-adrenoreceptor
• PLC activated
• increases production of IP3
• binds to RyR –> depolarisation of Ca
• Ca2+ binds to Calmodulin–> increases activity MLCK = contraction
• increases TPR

Question 3

What causes the increase in urea production and thirst?

Answer 3

• Low renal artery pressure= increased renin
• renin catalyses angiotensinogen in the liver to angiotensin I
• angiotensin I –> angiotensin II via ACE
  = increase in angiotensin II
  = vasoconstriction + thirst
• increase in aldosterone

Question 4

What are the signs and symptoms of haemorrhage?

Answer 4

Pale skin
Cold extremities
Agitated
Thirsty
- increase in urea conc
- decrease in BP
- Increase in HR
- fall in haemoglobin conc