Practical 2

Question 1

explain the immediate effect of moving from a supine to standing position

Answer 1

1. gravity causes blood to pool in legs
2. reduced venous return
3. reduced stroke volume (starling law)
4. reduced MABP

Question 2

explain the overall effect of moving from supine to standing position

Answer 2

1. reduced MABP leads to reduced firing of baroreceptors
2. baroreceptors increase SNS and decrease PSNS output
3. causes vasoconstriction , increased TPR, increased HR , increased venous return
4. increased venous return and HR partially restore CO
5. TPR and partially restored CO restore MABP

Question 3

what factors contribute to the restoration of MABP and to what extent

Answer 3

1. increased HR and venous return partially restore CO

2. increased TPR & partially restored CO lead to MABP restoration

Question 4

is partial increase in CO enough to restore MABP?

Answer 4

no it is not sufficient, only partially restores MABP

Question 5

what would happen without this standing up baroreceptor reflex

Answer 5

reduced MABP
not enough blood to brain
orthostatic hypotension
dizziness and fainting

Question 6

describe how baroreceptor reflex is triggered during exercise

Answer 6

1. increase in blood flow needed to muscles
2. increase in skin blood flow (thermoregulation)
   this deceases TPR

Question 7

how do baroreceptors respond to exercise?

Answer 7

increasing CO

Question 8

what stimulates the response for increasing CO during exercise?

Answer 8

1. feed forward mechanism of brain anticipating exercise

2. muscle stimulation (metabolite &mechanical)

Question 9

how is CO increased during exercise

Answer 9

1. medullary CV centre detects stimuli (from brain and muscles)
2. reduces PSNS and increases SNS
3. increases HR, SV and VR
4. vasoconstriction in kidneys, gut partially increases TPR
5. restoration of CO and TPR maintains MABP

Question 10

describe diving reflex

Answer 10

1. facial immersion in cold water detected by receptors
2. reduced HR — reduced CO
3. vasoconstriction in muscle, skin, kidneys , gut etc
4. vasoconstriction greatly increases TPR
5. TPR compensates for lower CO maintaining MABP

Question 11

what does P wave of an ECG represent

Answer 11

atrial depolarisation

Question 12

what does QRS wave of an ECG represent

Answer 12

ventricular depolarisation

Question 13

what does T wave of an ECG represent

Answer 13

ventricular repolarisation

Question 14

how can heart rate (BPM) be calculated from ECG

Answer 14

60 / R-R interval(s)