Cardiovascular System

Question 1

What percentage of blood is plasma?

Answer 1

55%

Question 2

What is plasma composed of?

Answer 2

Water, electrolytes, plasma proteins

Question 3

Name 3 plasma proteins.

Answer 3

Albumin - important in maintaining blood pressure
Fibrinogen - inactive form of fibrin, blood clotting
globulins - fat transport and immune function

Question 4

why are red blood cells biconcave shape?

Answer 4

Allows cells to fold over in narrow capillaries, allows the cells to expand and accommodate fluid in hypotonic solution

Question 5

where are red blood cells produced?

Answer 5

Red bone marrow, in skull, sternum and hip bones

Question 6

describe red blood cell production.

Answer 6

Low oxygen delivery to kidneys is detected, erythropoietin is released, stimulates the red bone marrow, uses amino acids to produce proteins and iron in the haemoglobin. These cells are then matured, shrink in size and lose nucleus

Question 7

What vitamins are required for red blood cell production

Answer 7

vitamin b12 and vitamin k

Question 8

Describe how the mixing of blood can be dangerous at birth between a rheus’ negative mother and rheus’ positive baby.

Answer 8

if mother gets rheus’ positive blood, exposed to antibody so the mother produces an antigen against this. If the mother then goes on to have another rheus’ positve child, the antigens in the mothers blood will be passed to the baby. These will attack the blood in the baby resulting in haemolysis

Question 9

What is the role of the chordinae tendinae and pupillary muscles in the heart?

Answer 9

These hold the flaps and orientate their shape. They have no role in the opening and closing of the flaps, completely done by pressure changes

Question 10

What are the noises of the heart and how are these sounds produced?

Answer 10

The LUB noises is produced from the AV valve closing. This closes as the ventricle contracts, increasing the pressure. The DUB noise is produced from the SL valves closing, this is as the pressure in the ventricle is reduced due to the blood leaving, closes to prevent back flow

Question 11

Describe starling’s law

Answer 11

If more blood is returned to the heart, the end diastolic volume is increased. This is detected by stretch receptors on the heart. The contraction is then increased to increase the volume of blood pushed out of the heart.

Question 12

Describe the SA node action potential.

Answer 12

There is a gradual rise to the threshold level, as there is a constant leakage of calcium into the cell. Once it reaches threshold, there is a much more rapid increase of calcium. As it reaches +30mV, calcium channels are closed and potassium channels are opened, the cell is repolarised

Question 13

Desribe purkinje cell action potential

Answer 13

voltage gated Na channels are opened, causing depolarisation. At +30mV, calcium channels are opened. As calcium enters the cell, there is a plateau phase in the AP, preventing repolarisation. After this, potassium channels are opened, allowing for repolarisation

Question 14

How does the autonomic system act to lower the heart rate?

Answer 14

The parasympathetic system releases acetylcholine, this increases potassium permeability at the SA node. Takes longer to reach theshold

Question 15

How does the autonomic system act to increase the heart rate?

Answer 15

Sympathetic nervous system releases noradrenaline which increase Ca permeability at the SA node. Reaches threshold faster.

Question 16

What is calcium induced calcium release?

Answer 16

Calcium moves into the cell, this binds to the sacroplasmic reticulum which amplifies this response and releases more calcium

Question 17

Describe what happens at each point on the ECG wave.

Answer 17

P - atrial depolarisation, QRS - ventricular depolarisation, T - ventricular repolarisation. P-R interval - time taken for impulse to go through AV node. S-T interval - plateau phase in AP, calcium entry

Question 18

What is the role of the endothelial cells in blood vessels?

Answer 18

permeable for nutrients and gases, can control underlying muscles for vasoconstriction

Question 19

What do smooth muscle cells do in blood vessels?

Answer 19

Control the diameter of the lumen of the vessel

Question 20

How does the structure of the arteries give the function?

Answer 20

A lot of elasticity giving the vessels compliance to maintain the pressure

Question 21

What is the pulse pressure?

Answer 21

Systolic pressure - diastolic pressure

Question 22

how can the mean arterial pressure be calculated?

Answer 22

diastolic + 1/3rd pulse

map = cardiac output x total peripheral resistance

Question 23

how can the tpr be reduced by drug therapy?

Answer 23

blocking alpha 1 adrenoreceptors on the smooth muscle in blood vessels, prevents vasoconstriction increases dilation - prazosin

Question 24

Describe the pressures influencing the movement of fluid through the capillaries.

Answer 24

As blood enters capillaries, hydrostatic pressure is high pushing fluid out of capillaries. As fluid is pushed out, the hydrostatic pressure is reduced along the capillaries. The oncotic pressure (from plasma proteins) remains the same along the capillary. At the venous end, the oncotic pressure exceeds the hydrostatic pressure, pulling fluid back into the capillary.

Question 25

Name the factors that influence blood flow.

Answer 25

Pressure gradient, viscosity, length of tube and radius of tube

Question 26

what is the relationship between the radius of the vessel and the flow rate?

Answer 26

As the radius increases, the flow increases. In the equation, radius is to the power of 4 so a small change in radius results in a large change in flow

Question 27

How can viscosity alter the blood flow and why is this important on flights?

Answer 27

A fluid with a high viscosity has a lower flow rate. In flights, people often drink alcohol, making them dehydrated and increasing the viscosity of the fluid. This is accompanied with inactivity, making the venous return poor and can increase oedema in the legs.

Question 28

How can the blood flow in veins be altered?

Answer 28

Decreasing the diameter of the vessel, increases the pressure, thus improves flow. Can be done using sympathetic nervous system for vasoconstriction, in exercise improves venous return to increase CO

Question 29

Why is the venous blood flow important in angina patients and how can this be altered to relieve symptoms?

Answer 29

an increased venous return increases the pre-load on the heart, giving it more work to do thus it requires more oxygen and symptoms are more intense. Giving alpha 1 antagonists, blocks sympathetic vasoconstriction on veins meaning the vessel diameter will be wide, the pressure will be low and venous blood flow will be reduced. Nitrates are used for this

Question 30

what nerves do the baroreceptors in the carotid sinus and aortic arch activate?

Answer 30

carotid sinus - glossopharyngeal

aortic arch - vagal

Question 31

describe the sequence of events that occur in response to a high blood pressure.

Answer 31

baroreceptors send nerve signal to nucleus tractus solitarius in medulla oblongata. parasympathetic NS stimulated, activates alpha 2 receptors. This activates then vagal nucleus. this sends acetylcholine to the muscarinic receptors on the heart, slow heart rate down, Alpha 2 receptors also inhibit the sympathetic ns and bulbar circulatory centre - reduce HR and vasoconstriction

Question 32

Describe the sequence of events that occur in response to low blood pressure.

Answer 32

baroreceptors send signal to the nucleus tractus solitarius in medulla oblongata, activates beta receptors to stimulate the bulbar circulatory centre. This uses noradrenaline to increase the heart rate on beta 1 receptors and increase vasoconstriction on alpha 1 receptors. Also inhibits the vagal nucleus to remove the reduce on heart rate

Question 33

how can blood pressure be controlled locally?

Answer 33

Metabolites are released which cause local vasodilation to increase the blood flow

Question 34

Describe how blood pressure can be measured.

Answer 34

Use a cuff around the arm - increases pressure to reduce blood flow through radial artery. Use sphyg. to listen for flow, once flow stopped, start reducing pressure slowly. Pressure at which flow is first heard - systolic pressure. Keep reducing pressure slowly, when no flow is heard again - diastolic pressure

Question 35

what occurs as a patient is moved from lying down to standing up?

Answer 35

Blood is pulled by gravity to the lower limb, it can then pull in the veins reducing venous return. Then, less blood is pumped out by heart, less blood to brain, baroreceptors detect decrease in blood pressure - reduced firing to brain

Question 36

In an ECG, what does the T-Q interval represent?

Answer 36

Ventricular diastole

Question 37

What is the haematocrit?

Answer 37

The percentage red blood cells in a volume of blood

Question 38

Describe 2 ways in which haemolysis can occur?

Answer 38

Cells in a hypotonic solution, water moves into cells from surrounding solution, causing cell to burst
Detergents can breakdown lipids in cell membrane, causing the cell to burst

Question 39

What is the difference between an isotonic solution and an iso-osmotic solution?

Answer 39

isotonic - equal osmolarity and impermeant solutes

iso-osmotic - equal osmolarity but solutes are permeant

Question 40

Why is stored blood more fragile than fresh blood?

Answer 40

stored blood has less ATP so cannot prevent haemolysis as efficiently, haemolysis occurs at lower % of saline