L7&8 - Cardiovascular

Question 1

what are the three blood vessel types?

Answer 1

• arteries (branch into arterioles)
• veins
• capillaries

Question 2

what is the vascular system?

Answer 2

a closed system of arteries, veins and capillaries ‘plugged into’ the right and left side of the heart

Question 3

how does Ohm’s law apply to the vascular system?

Answer 3

major variables in blood flow (Q) = pressure and resistance
Q= ΔP/R

Question 4

where is the greatest pressure?

Answer 4

arteries

Question 5

where is the greatest pressure drop?

Answer 5

arterioles

Question 6

describe blood vessel diameter

Answer 6

blood vessels are cylindrical non-rigid tubes that can therefore change their radius

Question 7

how does the sympathetic nervous system innervate blood vessels?

Answer 7

increased SNS activity causes vasoconstriction - which increases resistance

Question 8

how do arterioles act as exchange vessels?

Answer 8

arterioles are located immediately before the capillaries, so the level of resistance in the arterioles determines the blood flow into the capillaries

Question 9

what are arteries made of?

Answer 9

smooth muscle

Question 10

what are capillaries made of?

Answer 10

one cell thick - endothelial cells - no smooth muscle

Question 11

what happens in the capillaries that happens nowhere else in the circulatory system?

Answer 11

exchange between the circulatory system and body cells of nutrients, gases, water and waste products of metabolism

Question 12

what is osmotic pressure?

Answer 12

the pressure in the blood due to its solute concentration, the more solute - the higher the osmotic pressure

Question 13

what is the 1/3 step of capillary exchange?

Answer 13

1. filtration: capillary blood/hydrostatic pressure forces fluid out of capillaries into interstitial fluid at arterial end of capillary

Question 14

what is the 2/3 step of capillary exchange?

Answer 14

2. reabsorption: at the venous end, fluid is reabsorbed back into the capillary

Question 15

what is the 3/3 step of capillary exchange?

Answer 15

3. blood colloid osmotic pressure: pressure due to plasma proteins draws fluid up into capillaries from interstitial fluid all along the capillary

Question 16

what is the baroreceptor reflex response to an increase in blood pressure?

Answer 16

• when BP increases there is greater stretch on baroreceptors
• increased nerve impulses to the cardiovascular control centre (medulla oblongata)
• the output from the control centre decreases sympathetic nerve activity, leading to a decreases in cardiac output and decreased peripheral resistance

Question 17

how does the baroreceptor reflex respond to a decrease in blood pressure?

Answer 17

• as BP drops there is LESS stretch on the receptors so decreased rate of nerve impulses to the CV centre
• increased sympathetic and decreased parasympathetic stimulation
• increased stroke volume and HR lead to increased cardiac output and constriction of blood vessels increases systemic vascular resistance

Question 18

what is RAAS and where is it released?

Answer 18

renin-angiotensin aldosterone system
released by kidney

Question 19

how does RAAS affect blood pressure?

Answer 19

RAAS comprises renin, angiotensin II and aldosterone
these elevate arterial blood pressure in response to decreased renal blood pressure

Question 20

how does antidiuretic hormone affect BP?

Answer 20

if BP falls, ADH is released from the posterior pituitary and causes water retention by the kidneys, which helps to expand blood volume and increase BP

Question 21

how does atrial natriuretic peptide affect BP?

Answer 21

ANP is a salt losing hormone so it counteracts the effect of aldosterone
if BP is too high it can be released
in health, there is a balance of ANP and aldosterone

Question 22

list the percentage of total cardiac output that flows to each organ at rest and exercise

Answer 22

Rest | Heavy Exercise |
| GIT | 20-25% | 3-5% |
| Heart | 4-5% | 4-5% |
| Kidneys | 20% | 2-4% |
| Bone | 3-5% | 0.5-1% |
| Brain | 15% | 3-4% |
| Skin | 4-5% |
| Muscles | 15-20% | 80-85% |

Question 23

what are the focus organs for blood flow during rest?

Answer 23

GIT, kidneys and brain

Question 24

what are the focus organs for blood flow during exercise?

Answer 24

muscle metabolism increases so blood is shunted from other regions to focus on:
skin (temperature regulation)
muscles (movement)

Question 25

what is active hyperemia?

Answer 25

vasodilation of the arterioles that feed the muscle with vasoconstriction of the arterioles supplying other organs

Question 26

what induces reactive hyperemia?

Answer 26

lack of blood flow to an organ leads to ischemia - induced to prevent skin ulceration

Question 27

what are the key differences between fetal circulation and adolescent circulation system?

Answer 27

1. umbilical vein and ductus venosus carries oxygenated blood from the placenta which empties into the inferior vena cava
2. ductus arteriosus allows blood to pass from the pulmonary trunk directly into the aorta (bypassing the lungs) and onwards to the systemic circulation
3. umbilical arteries transport fetal deoxygenated blood to the placenta - foramen ovale allows blood flow to bypass the lungs