module three

Question 1

countercurrent flow

Answer 1

water flows opposite to blood over gill lamellae

Question 2

what is countercurrent flow needed to do?

Answer 2

maintain concentration gradient for diffusion

Question 3

open circulatory systems

Answer 3

few transport vessels, pumped at low pressure and doesnt transport gases

Question 4

single circulatory system

Answer 4

one per cycle, one circuit and 2 sets of capillaries.

works for fish due to countercurrent mechanism

Question 5

capillaries

Answer 5

lumen just slightly bigger than red blood cell, red blood cell squashed against walls and walls one cell thick in order to create a short diffusion distance and maximise diffusion

Question 6

smooth muscle

Answer 6

thicker in arteries than veins, but thickest in arterioles. none in capillaries. helps constrict the arteries so blood can flow through at high pressure.

Question 7

elastic layer

Answer 7

thicker in arteries and veins to maintain high blood pressure. none in capillaries, thickest in arteries.

Question 8

collagen layer

Answer 8

lots of collagen in walls of veins for strength.

Question 9

hydrostatic pressure

Answer 9

pressure exerted by liquid

Question 10

oncotic pressure

Answer 10

tendancy of water to move into the blood by osmosis

Question 11

where abouts in the capillaries has high hydrostatic pressure?

Answer 11

arteriole end due to small diameter.

this pressure forces water, glucose, fatty acids, amino acids, ions and oxygen out of the capillaries at the arterial end.

Question 12

tissue fluid reabsorption

Answer 12

large molecules e.g. plasma proteins remain in the capillaries and therefore lower the water potential of the blood remaining in the capillary.

this lower water potential results in a higher oncotic pressure towards the venule end of the capillaires

hydrostatic pressure low due to loss of liquid , water potential very low

Question 13

what happens to the remaining liquid in the capillaries?

Answer 13

absorbed into lymphatic system, eventually drained back into the bloodstream near the heart.

Question 14

spiracles

Answer 14

open and close for gas exchange and to prevent water loss

Question 15

why do insect abdominal muscles contract and relax?

Answer 15

for pumping mechanism to moce gases in and out of spiracles and trachea

Question 16

what does many tracheoles allow the insect to have?

Answer 16

large surface area

Question 17

what do the tracheoles being thin-walled and close to the muscle mean?

Answer 17

short diffusion distance

Question 18

what happens when an insect is in flight?

Answer 18

anaerobic respiration to produce lactate.
this lowers the water potential of the cells so water moves from tracheoles to the cells by osmosis
this decreases volume of liquid in the tracheoles, so more air from the atmosphere moves in

Question 19

what do the coronary arteries supply the cardiac muscle with?

Answer 19

oxygenated blood for aerobic respiration, provides ATP so the cardiac muscle can continually contract and relax

Question 20

preicardial membranes

Answer 20

surrounds the heart and are inelastic which prevents the heart from filling and swelling with blood

Question 21

why is the left ventricle thicker than the right one?

Answer 21

so it can contract with more force and pump blood at a higher pressure as it needs to reach all around the body.

Question 22

why do the atria have thin walls

Answer 22

blood only needs to be pumped to the ventricles

Question 23

atrial systole

Answer 23

atrial muscles contract, increasing pressure further. AV valves open and blood flows to the ventricles

Question 24

ventricular systole

Answer 24

ventricular muscles contract, increasing pressure. AV valves close and SL valves open. blood is pushed out of the ventricles and into the arteries

Question 25

diastole

Answer 25

blood enters the atria via the vena cava and pulmonary vein
blood flowing into the atria increases pressure into the atria

Question 26

cardiac output

Answer 26

heart rate x =stroke volume

Question 27

where is the SAN located

Answer 27

right atrium
known as the pacemaker

Question 28

where is the AVN located

Answer 28

near the border of the right and left ventricle within the atria still

Question 29

where is the bundle of HIS located

Answer 29

runs through the septum

Question 30

where are the purkyne fibres located

Answer 30

walls of the atrium

Question 31

what does the SAN do? (first step in the control of the cardiac cycle)

Answer 31

releases a wave of depolarisation across the atria

Question 32

what does the AVN do? (second step in the control of the cardiac cycle)

Answer 32

releases another wave of depolarisation when the first wave reaches it.

A conductive layer between the atria and ventricles prevents the wave of depolarisation travelling down the ventricles