CVS Adaptations

Question 1

What is the skeletal muscle pump

Answer 1

During muscle contraction blood is squeezed towards the heart, valves prevent back flow.

Question 2

What happens to your cardiovascular system when you stand up

Answer 2

• Orthostatic/Postural Hypotension

- Gravity induced blood pooling

Question 3

What is a baroreceptor, what does it detect and where is it found

Answer 3

A stretch sensitive mechanoreceptor that responds to changes in pressure, located in the carotid and aortic arteries.

Question 4

When baroreceptors sense a decrease in blood pressure what response do they trigger

Answer 4

They trigger a response via a homeostatic mechanism that increases heart rate and force of contraction, causes vasconstriction, which increases peripheral resistance and cardiac output, returning BP to normal

Question 5

What neurotransmitter do sympathetic vasoconstrictor nerve fibres secrete

Answer 5

Noradrenaline

Question 6

What effect does the noradrenaline from sympathetic vasoconstrictor nerve fibres have the blood flow

Answer 6

Decreases it through resting muscles to as little as half or a third.

Question 7

When is the action of sympathetic vasoconstrictor nerve fibres physiologically important

Answer 7

Circulatory shock

Hypotensive crisis

Question 8

During exercise how do muscles react to Noradrenaline

Answer 8

They become unresponsive to the vasoconstriction effect from NA

Question 9

During exercise what do the two adrenal medullae do

Answer 9

They secrete large amounts of NA and adrenaline

Question 10

During exercise what effect does adrenaline have

Answer 10

It mainly acts on Beta2 adrenergic receptors and result in vasodilation

Question 11

During exercise what effect does the capillaries opening have

Answer 11

All the capillaries open
Increases blood flow
Increased surface area for exchange
Increase nutrient and oxygen supply to muscle

Question 12

How does decreased oxygen in the muscle affect the control of blood flow

Answer 12

Greatly enhances flow and also causes the release of local vasodilator substances

Question 13

Name a few vasodilator substances and which is the most important

Answer 13

Adenosine - most important
K+
ATP
Lactic Acid
Carbon Dioxide

Question 14

What 3 main receptors provide feedback to the higher brain centres to drive the CVS

Answer 14

Chemoreceptors
Mechanoreceptors
Baroreceptors

Question 15

What effect does shock have on he blood flow/supply

Answer 15

Generalised severe reduction in blood supply to the body tissues. Inadequate tissue perfusion leads to cellular hypoxia and tissue damage

Question 16

What is Hypovolemic shock

Answer 16

Refers to a medical or surgical condition in which rapid fluid loss results in multiple organ failure due to inadequate perfusion

Question 17

What can cause hypovolemic shock

Answer 17

• Trauma
• Haemorrhage
• Vomiting/diarrhoea
• Burns

Question 18

What 4 major physiological systems does the human body activate to respond to acute haemorrhage

Answer 18

The Haematological system
The Cardiovascular system
The Renal system
The Neuroendocrine system

Question 19

What effect does hypovolemic shock have on the CVS

Answer 19

Increases heart rate
Increases myocardial contractility
Contrstricts peripheral vessels

Question 20

How does the CVS re-distribute blood due to hypovolemic shock

Answer 20

Redistributes blood to the brain, heart and kidneys and away from the skin, muscles and GI tract.

Question 21

How does the renal system respond to hypovolemic shock

Answer 21

The kidneys respond by stimulating an increase in renin secretion from the juxtaglomerular apparatus

Question 22

What does renin do

Answer 22

Cleaves angiotensinogen into Angiotensin 1 and ACE converts AT1 into AT2

Question 23

What effects does AT2 have in response to hypovolemic shock

Answer 23

AT2 has 2 main effects to reverse hypovolemic shock.

Vasoconstriction of arteriolar smooth muscle and stimulation of aldosterone secretion by the adrenal cortex

Question 24

How does the neuroendocrine system react to hypovolemic shock

Answer 24

Cause an increase in circulating ADH

Question 25

What do baroreceptors detect to cause ADH release

Answer 25

Decreased BP

Decreased [Na+]

Question 26

How does the haematological system respond to hypovolemic shock

Answer 26

Activating the coagulation cascade and contracting the bleeding vessels, via local Thromboxane A2 release

• Platelets are activated to form an immature clot on the bleeding source, the damaged vessel exposes collagen that causes fibrin deposition and stabilisation of the clot

Question 27

What is the response to <15% blood loss haemorrhage (class 1)

Answer 27

minimal fast heart rate, normal blood pressure

Question 28

What is the response to 15-30% blood loss haemorrhage (class 2)

Answer 28

Fast heart rate, minimal low blood pressure

Question 29

What is the treatment for class 2 haemorrhage

Answer 29

Intravenous fluids

Question 30

What is the response to 30-40% blood loss haemorrhage (class 3)

Answer 30

Very fast heart rate, low blood pressure, confusion, almost no blood flow to the kidney and liver, reduced blood flow to brain and heart

Question 31

What is the treatment for class 3 haemorrhage

Answer 31

Fluids and packed RBCs

Question 32

What is the response to >40% blood loss haemorrhage (class 4)

Answer 32

Severe hypotension and tachycardia