Week 9 - Cardiovascular system (blood vessels)

Question 1

Distinguish between he structure and function of arteries, veins and capillaries

Answer 1

• Arteries: Carry blood away from the heart
• Thick muscular walls to withstand high blood
pressure
• Veins: Carry blood towards the heart
• Thin muscular walls and large diameter of lumen
to decrease resistance and enhance the
drainage of blood back to the heart.
• Valves to prevent back flow of blood
• Capillaries: Involved in nutrient, gas and waste exchange
• Single layer of endothelial cells to allow for rapid
diffusion

Question 2

Define blood pressure

Answer 2

Is the force of blood pressing against the walls of the arteries in each cardiac cycle.

Question 3

Normal blood pressure is 120/80, what do these valuesre present?

Answer 3

• Systolic pressure - The maximum blood pressure placed on the arterial walls when the heart is contracting
• Diastolic pressure - The maximum blood pressure placed on the arterial walls when the heart is relaxing.

Question 4

What is mean arterial pressure (MAP)?

Answer 4

Is the average arterial pressure during a single cardiac cycle.

Question 5

Why is MAP considered the best indicator of blood perfusion?

Answer 5

It is considered the best indicator of blood perfusion as the heart spends more time relaxing than contracting

Question 6

What is the calculation for MAP?

Answer 6

Mean arterial pressure (MAP) = diastolic + 1/3 (systolic - diastolic )

Question 7

What is pulse pressure?

Answer 7

Systolic pressure - diastolic pressure

Question 8

Don’t have to know# What are the 3 factors that influence MAP?

Answer 8

• Cardiac output - increases cardiac output increases MAP as there is more blood being pumped into the arterial system.
• Total peripheral resistance - vasoconstriction of blood vessels increases resistance and pressure
• Blood volume - as the cardiovascular system is a closed system increased blood volume increases pressure.

Question 9

What is autoregulation?

Answer 9

Is the local ability for an organ or tissue to maintain constant blood flow despite changes in blood pressure.

Question 10

Describe the two mechanisms that can alter blood flow

Answer 10

1) Diameter of blood vessels - vasoconstriction and vasodilation.
2) Precapillary sphincters - Can relax or contract to control the flow of blood into capillaries.

Question 11

What organs is auto regulation particularly useful for?

Answer 11

Brain, kidneys and heart and constant blood flow to these areas is necessary to sustain life.

Question 12

Distinguish between metabolic and myogenic regulation

Answer 12

Metabolic regulation occurs in response to metabolic processes, whereas myogenic regulation occurs in response to blood pressure changes.

Question 13

What is the stimulus and response of metabolic regulation?

Answer 13

• Stimulus: Increase in metabolic wastes such as CO2 and H+ ions, and decrease in oxygen
• Response: Vasodilation of blood vessels

Question 14

What is the stimulus and response of myogenic regulation?

Answer 14

• Stimulus: Blood pressure (blood vessel stretch)
• Response:
  * Increase in blood pressure - Vasocontriction
  * Decrease in blood pressure - Vasodilation

Question 15

What is the purpose of the baroreceptor reflex?

Answer 15

It is a negative feedback mechanism that maintains stable blood pressure

Question 16

What are baroreceptors and where are they found in the body?

Answer 16

They are stretch receptors located in the walls of the aortic arch and carotid bodies.

Question 17

What nerves carry the baroreceptor signals to the brain?

Answer 17

• Vagus

* Glosopharyngeal

Question 18

What area of the brain controls cardiac function?

Answer 18

Medulla oblongata

Question 19

Describe the baroreceptor reflex in response to an increase in blood pressure

Answer 19

1) Baroreceptors detect increase stretch
2) Signals sent along cranial nerves to cardiovascular and vasomotor regulatory centres in the medulla
3) Parasympathetic activation and sympathetic inhibition decreases heart rate and stroke volume (cardiac output).
4) Vasomotor centre decreases sympathetic stimulation causing vasodilation of blood vessels
5) This results in the lowering of blood pressure

Question 20

Describe the baroreceptor reflex in response to a decrease in blood pressure

Answer 20

1) Baroreceptors detect decrease stretch
2) Signals are transmitted to the vasomotor and cardiovascular regulatory centres in the medulla
3) Parasympathetic inhibition and sympathetic stimulation increases heart rate and stroke volume (cardiac output).
4) Vasomotor centre increases sympathetic stimulation to cause vasoconstriction of blood vessels.
5) This results in an increase in blood pressure.

Question 21

What are the short and long term ways to regulate blood pressure?

Answer 21

• Baroreceptor reflex

* Renal blood pressure regulation

Question 22

What do the kidneys regulate to provide the long term regulation of blood pressure?

Answer 22

Regulates blood pressure by regulating blood volume

Question 23

What is the name of the long term regulation of blood pressure by the kidneys?

Answer 23

• Renin-angiotensin-aldosterone mechanism

Question 24

What cells produce renin?

Answer 24

juxtaglomerular cells of the Kidneys

Question 25

What organs produce angiotensinogen?

Answer 25

Liver

Question 26

What is the function of renin?

Answer 26

Converts angiotensinogen to angiotensis I

Question 27

What is the function of angiotensin-converting hormone?

Answer 27

Converts angiotensin I to angiotensin II

Question 28

What is the function of angiotensin II

Answer 28

• It is a vasoconstrictor that decreases the diameter of blood vessels and thus increases blood pressure
• Also stimulates the release of aldosterone from the kidneys

Question 29

What triggers the release of renin from the cells of the nephron?

Answer 29

Stimulation from the sympathetic NS in response to low BP

Question 30

What organ releases angiotensin converting hormone?

Answer 30

Lungs

Question 31

What is the function of aldosterone?

Answer 31

Aldosterone increases sodium re absorption in the kidney tubules and thus increases water absorption, blood volume and thus blood pressure

Question 32

What cells doe the SA and AV nodes consist of?

Answer 32

pacemaker cells