TOPIC 3 - mass transport - mammalian circulatory system + the heart structure + cardiac cycle

Question 1

what is the function of coronary arteries?

Answer 1

to carry oxygen to heart tissues

Question 2

relate the structure of the chambers to their function?

Answer 2

ATRIA - thin walled, elastic so they can stretch when filled up with blood

VENTRICLES - thick muscular walls = pump blood under high pressure
Left ventricle = thicker = has to pump blood all the way around the body

Question 3

relate the structure of the vessels to their function?

Answer 3

ARTERIES -
elastic tissue to maintain high blood pressure
muscular tissue to maintain high blood pressure
narrow lumen to maintain high blood pressure
smooth endothelium so blood flows past easily

VEINS - thin walls due to low pressure. Have valves to prevent back flow. Less muscular + elastic tissue as they don’t control blood flow

Question 4

why are there two pumps needed in the LHS and RHS of heart instead of one?

Answer 4

• to maintain BP around the body
• BP drops sharply when blood flows around the capillaries in the lungs and therefore wont be flowing around strongly to continue around the body.
• it flows through the heart to increase blood pressure

Question 5

what direction does blood flow in the double circulatory system?

Answer 5

de oxygenated blood from the body pumpeto vena cava —> right atrium —> right ventricle —-> pulmonary artery carries de O2—> lungs —-> pulmonary veins carry oxygenated blood —> left atrium —> left ventricles —> aorta —-> body

Question 6

where are the semi lunar valves found?

Answer 6

aorta and pulmonary artery

Question 7

where are the atrioventricular valves?

Answer 7

between atria and ventricles

Question 8

what are the types of atrioventricular valves and where are they found?

Answer 8

1. Bicuspid found on left
2. tricuspid found on right

Question 9

what is the role of the septum?

Answer 9

-separates the left and right side of the heart
-separates oxygenated blood from deoxygenated blood
-maintains high conc of oxygen in oxygenated blood to maintain conc gradient to enable diffusion of respiring cells

Question 10

describe what happens during cardiac diastole?

Answer 10

• atria and ventricles relax
• blood will enter atria via vena cava + pulmonary vein
• increased pressure within atria

Question 11

what happens during atrial systole?

Answer 11

• atria contracts
• ventricles relax
• increased pressure in atria
• AV valves open = blood flows into ventricles

Question 12

what happens during ventricular systole?

Answer 12

• ventricles contract
• vol of ventricles decrease = BP in ventricles increase
• AV valves close to prevent back flow
• Semi lunar valves open
• blood flows into arteries

Question 13

what does myogenic mean?

Answer 13

the hearts contraction is initiated from within the muscle itself, rather than by nerve impulses.

Question 14

what are the nodes involved in heart contraction? where are they found?

Answer 14

(SAN) Sinoatrial node = wall of the right atrium
(AVN) Atrioventricular node = in between the two atria

Question 15

explain how the heart contracts?

Answer 15

-SAN initiates and spreads the impulse across the atria so they contract.
- AVN receives, delays then conveys the impulse down the bundle of his
- impulse travels into the purkinje fibres which branch across the ventricles, so they contract from bottom up.

Question 16

why does the impulse need to be delayed?

Answer 16

if the impulse is spread straight from the atria to ventricles, there would not be enough time for the blood to pass through and for the valves to close.

Question 17

how is the structure of the capillaries suited to their function?

Answer 17

• one cell thick= short diffusion pathway
  -narrow so rbc can lie flat against the cell, effectively delivering O2 to the tissues
• large number of capillaries = increase SA for exchange

Question 18

how is the structure of the arteries suited to their function?

Answer 18

• carries blood from heart to body
• thick muscular, elastic tissues to stretch and recoil as heart beats = helps maintain pressure
• inner lining= endothelium = helps artery stretch
• carries O2 blood except PULMONARY ARTERY

Question 19

what are arterioles?

Answer 19

• arteries divided into smaller vessels
• form a network throughout the body
  -blood directed different areas of demand by muscles inside arterioles
  = contract/restrict/relax or allow full blood flow

Question 20

how is the structure of the veins related to its function?

Answer 20

• take blood back to the heart
  -carries de O2 blood except for PULMONARY VEINS( to heart from lungs)
• little elastic + muscle tissue
• valves to stop back flow of blood

Question 21

what is tissue fluid?

Answer 21

• fluid that surrounds cells in tissues
• substance containing glucose, amino acids, oxygen, and other nutrients.
• these are supplied to cells whilst removing waste materials

Question 22

how is tissue fluid formed?

Answer 22

As blood is pumped through increasingly small vessels, hydrostatic pressure is created which forces the fluid out of the capillaries. It bathes the cells, and returns to capillaries when hydrostatic pressure is low enough.