L18 Cardiovascular Response to Exercise and Blood Loss

Question 1

What is the average cardiac output at rest?

Answer 1

5.8 L/min

Question 2

True or false: When necessary, heart rate can increase by 250% and stroke volume can almost double

Answer 2

True

Question 3

Which of the following receive the same amount of blood flow, regardless of how much exercise is done?

A) Skeletal Muscles
B) Brain
C) Abdominal viscera
D) Kidney
E) B and D
F) A and D
G) B and C
H) All of the above

Answer 3

B) Brain

All other tissues will either receive more blood, or less.

More: skeletal muscles, heart, skin

Less: kidneys, abdominal viscera

Question 4

Anticipatory responses can activate the sympathetic nervous system and result in what cardiac changes?

Answer 4

Increased heart rate

Vasoconstriction of the splanchnic arterioles (splanchnic refers to major viscera)

Question 5

Which of the following occurs as a result of light exercise?

A) Increase vasodilation
B) Increased venous return
C) Increased cardiac output
D) All of the above

Answer 5

D) All of the above

1) ↑ Vasodilation occurs as skeletal muscle consume O2 quicker.
2) ↑ Venus Return (↑VR) – Skeletal muscles aid return

3) ↑ CO due to a) ↑VR, and b) Atrial reflex. Although sympathetic
activity is not greatly increased, it is enough to ↑HR and ↑contractility

Question 6

What are the short-term cardiovascular responses to haemorrhaging?

Answer 6

Short-term goal: maintain blood pressure

Peripheral vasoconstriction due to ADH release (↑AngII) and sympathetic NS releasing NA and A. and

Increased cardiac output due to NA and A from adrenals

Question 7

What are the long-term cardiovascular responses to haemorrhaging?

Answer 7

Long-term goal: restore normal blood volume

Activation of RAAS (retain water, increase BP), ADH (retain water), EPO (replace lost RBCs).

Question 8

When is a person at risk of circulatory shock?

Answer 8

Loss of >20% of their blood volume

Cardiac damage

External pressure on the heart

Extensive peripheral vasodilation

Question 9

What are the symptoms of circulatory shock?

Answer 9

Hypotension (BP <90 systolic)

Cold, pale, clammy skin

Confusion

↑HR; weak pulse

Cessation of urination (leads to acidosis due to lactic acid)

Question 10

How much does blood volume need to drop for cardiac ischaemia to occur?

Answer 10

35%

Low blood pressure decreases supply of blood to the heart. Therefore, cardiac muscles suffer from ischaemia

Question 11

The central ischaemic response is triggered at BP of around 50mmHg. What is this response?

Answer 11

A sustained and maximal stimulation of the sympathetic stimulation of vasoconstriction occurs.

If untreated, BP will continue to fall until irreversible shock occurs.