Coordinated Cardiovascular Responses- Gravity And Exercise

Question 1

What is orthostasis?

Answer 1

Fancy word for standing up

Question 2

What happens when you first stand up?

Answer 2

Blood pressure falls at first

Postural hypotension, lack of blood flow to the brain- might feel faint

Question 3

What are the three smaller changes that take place to recover your blood pressure?

Answer 3

Increased heart rate, contractility and total peripheral resistance

Question 4

What is Bernoulli’s law?

Answer 4

Blood flow = pressure + potential energy + kinetic energy

Question 5

What does Bernoulli’s law mean?

Answer 5

Increased potential energy at heart vs feet + increased kinetic energy of ejected blood

Question 6

What is the high pressure in the venous system at the feet due to?

Answer 6

Hydrostatic pressure

Question 7

What happens to the blood in the veins when lying down?

Answer 7

Blood is evenly distributed in veins -> increased central venous pressure -> increased end diastolic volume -> increased stroke volume -> increased cardiac output

Question 8

What happens to the pressure in the veins when standing up?

Answer 8

Blood pooling in legs means less blood returning to the heart-> fall in central venous pressure -> decreased end diastolic volume -> decreased stroke volume-> decreased cardiac output-> poor perfusion of the brain

Question 9

What 5 things make postural hypotension worse?

Answer 9

Alpha adrenergic blockade
Varicose veins
Lack of skeletal muscle activity
Reduced circulating blood volume 
Increased core temperature

Question 10

How do varicose veins make postural hypotension worse?

Answer 10

Impairs venous return

Question 11

What are the short term effects of microgravity on the cardiovascular system?

Answer 11

Increased atrial/ventricular volume, preload and cardiac output

Question 12

What is reduced short term in microgravity?

Answer 12

Sympathetic activity
ADH
RAAS

Question 13

How much does blood volume reduce in microgravity?

Answer 13

20%

Question 14

What are long term effects of space on the cardiovascular system?

Answer 14

Less blood volume
Less stress on heart
Heart reduces in muscle mass
General drop in BP

Question 15

What happens to space people on return to gravity?

Answer 15

Severe postural hypotension due to too much lower blood volume and a small heart. Baroreceptors reflex cannot compensate

Question 16

What is dynamic movement?

Answer 16

Constant shortening and relaxing with lots of different muscle groups involved

Question 17

What is static exercise?

Answer 17

One specific muscle group is being worked without constant movement

Question 18

What happens once exercise starts (in the CV system)?

Answer 18

• Increased lung oxygen uptake, transport around the body and supply to exercising muscle
• control BP
• coordinate dilator/ constriction of vascular beds to target areas where oxygen is delivered

Question 19

How much can oxygen uptake by pulmonary circulation increase by during strenuous exercise?

Answer 19

10-15 times

Question 20

Will stroke volume increase exponentially?

Answer 20

No- it reaches a plateau

Question 21

What happens in exercise induced tachycardia?

Answer 21

Brain central command is alerted by muscle mechanoreceptors
The vessels in the muscle dilate
Sympathetic activity in the heart increases
Vagal tone decreases

Question 22

What happens in exercise induced increased end diastolic volume?

Answer 22

Increased venous return/ CVP through venoconstriction
Increased sympathetic activity and calf muscle pump
Activates starlings law and increases preload

Question 23

How does faster ejection help in exercise?

Answer 23

Increased contractility by sympathetic activation of beta 1 receptors

Question 24

What is the central control of the CV system during exercise?

Answer 24

RVLM controls specific pre-ganglionic sympathetic nerves in the spinal cord which sends out post-ganglionic nerves to specific tissues

Question 25

How is hypotension prevented during exercise?

Answer 25

Compensatory vasoconstriction of non-essential circulations prevent hypotension due to exercise, which induces decreased TPR

Question 26

What happens in static exercise?

Answer 26

Small increase in heart rate and large increase in blood pressure

Question 27

What are the changes due to in static exercise?

Answer 27

The constant contraction of small number of muscles leads to a high load.
The contracted muscle stops the vessels dilating so the rest of the body’s BP increases to push the blood through

Question 28

How does the blood pressure stay relatively constant in dynamic exercise?

Answer 28

Due to the shortening/ lengthening of many muscles = low load

Question 29

What does chemosensitive mean?

Answer 29

Stimulated by potassium, hydrogen and lactate, which increase in exercising muscle

Question 30

What are the reflex effects of metaboreceptors?

Answer 30

Tachycardia, increased blood pressure, pressor response, raised BP and dilated vessels

Question 31

When is the pressor response especially important?

Answer 31

During isometric exercise. Static exercise raises BP more than dynamic exercise