Heart

Question 1

Lumen

Answer 1

Central cavity

Question 2

Endothelium

Answer 2

Smooth preventing friction

Question 3

Elastic layer

Answer 3

Maintains blood pressure by recoiling

Question 4

Muscle layer

Answer 4

Contracts to control flow of blood

Question 5

Tough outer layer

Answer 5

Resists pressure within and outside

Question 6

Thin endothelium

Answer 6

Short diffusion pathway for exchange

Question 7

Plasma rbc wbc and platelets percents

Answer 7

55% plas
45% rbc
1% plat and wbc

Question 8

What kind of system is the heart

Answer 8

Myogenic

Question 9

Cardiac cycle

Answer 9

Controlled by the hearts electrical system, capable of working without input from ns

Question 10

Describe how a heartbeat is initiated and coordinated

Answer 10

-SA node sends impulses to atrium stimulating contraction
-non conductive tissue prevents immediate contraction of ventricles/prevents impulses reaching ventricles
-AVN delays impulse when blood leaves atria filling ventricle
-AVN sends impulses down the bundle of his
-v contract from base up

Question 11

Factors affecting O2 dissociation

Answer 11

Location ^ altitudes = lower pp 02 shifts left

Activity. ^ co2 = shifts right

Size lower size= ^ metabolism = shifts right

Question 12

Systole

Answer 12

Contracts
Vol decrease
Press increase

Question 13

Diastole

Answer 13

Relaxed

Question 14

Co operative binding

Answer 14

As o2 loads to oxygen
The binding causes the hb to change shape
This makes loading more oxygen easier
Until all haem groups are occupied and hb is saturated

Question 15

Dissociation and po2
Lungs vs respiring tissues

Answer 15

Hb has a higher affinity for o2 so it loads easier in the lungs/close to 100% saturated

In respiring tissues the saturation is low so o2 dissociâtes easily as o2 has a lower affinity for O2

Question 16

Bohr shift

Answer 16

Excersizing/ high metabolism organisms (small)
CO2 is acidic denaturing hb reducing affinity of o2 to hb
Tissues with lots of respiration o2 = easily unloaded so curve moves right as it’s easier to replace o2

Question 17

Explain how tissue fluid is formed and how it may be returned to the circulatory system [6]

Answer 17

• High Pressure caused by the ventricles contracting
• High hydrostatic pressure at the arteriole end of the capillary
• Water (and dissolved substances) are forced out (into the tissue) reject plasma/blood
• Large proteins remain in the blood
• Water potential increases in the tissue/decreases in the capillary
• Water enters at the venule end by osmosis
• Excess fluid is drained/absorbed into the lymph
• Lymph returns the fluid to the circulatory system

Question 18

Artery structure

Answer 18

Thick muscle layer – can control blood flow through constriction/dilation (only in smaller arteries/arterioles)
• Thick elastic layer – for elastic recoil/smooths blood flow
• Overall thick wall – to withstand high pressure form the
heart
• No valves – not needed as pressure is high

Question 19

Arterioles

Answer 19

• Similar to arteries but:
• Muscle layer is proportionally thick so blood flow
can be controlled.
• Elastic layer is thinner than arteries as blood is lower pressure

Question 20

Veins

Answer 20

• Thin muscle layer – blood flows away from tissues, doesn’t need to constrict
• Thin elastic layer – low pressure so no recoil
• Overall thin wall – blood is at low pressure
• Valves – to ensure no back flow of blood as pressure is low. Muscle contraction pushes blood through the valves

Question 21

Capillaries

Answer 21

• Thin/Endothelium only – short diffusion distance
• Very branched – large surface area
• Narrow lumen – red blood cells squeezed against endothelium short diffusion pathway
• Narrow diameter – permeate tissues
• Gaps between endothelium – substances can move in and out

Question 22

Relaxation of the heart (diastole)

Answer 22

• Blood returns to the atria of the heart through the pulmonary vein (lungs) and vena cava (body).
• The filling of blood in the atria increase the pressure and forces the AV valves open.
• Pressure is higher in the aorta and the pulmonary artery than in the ventricles so SL valves close

Question 23

Contraction of the atria (atrial systole)

Answer 23

• Atria (atrial walls) contract
• Pushing the remaining blood into the ventricles
• Ventricles remain relaxed and recoil

Question 24

Contraction of the ventricles (ventricular systole)

Answer 24

• The atria relax and after a short delay the ventricles fill with blood.
• The walls of the ventricles contract and the pressure increases forcing the AV valves to shut. Preventing backflow.
• The pressure increases in the ventricles and becomes higher than in the aorta and pulmonary artery – so SL valves open
• Blood is pushed away from the heart through pulmonary arteries and aort

Question 25

pLV > pLA

Answer 25

ATRIOVENTRICULAR VALVE CLOSES

Question 26

pLV > pAorta

Answer 26

SEMILUNAR VALVE OPENS

Question 27

pAorta > pLV

Answer 27

SEMILUNAR VALVE CLOSES

Question 28

pLA >pLV

Answer 28

ATRIOVENTRICULAR VALVE OPENS