circulation + the heart

Question 1

what does an open circulatory system do?

Answer 1

heart pumps blood into space in body cavity
tissues bathe in blood directly
blood flows slow back to heart (assistance from muscles and valves)

Question 2

what does a closed circulatory system do?

Answer 2

blood is transported in blood vessels
blood is pumped by muscular heart at high pressure
tissues are not in direct contact with blood
blood contains haemoglobin

Question 3

what are the advantages of closed circulatory system?

Answer 3

blood flow is more rapid and efficient
blood can be directed to where it is needed
more efficient delivery of oxygen and nutrients

Question 4

what is single circulation?

Answer 4

blood from anywhere in the body may pass only once through the heart

Question 5

what is double circulation?

Answer 5

blood must pass at least twice through the heart before returning to the same location in the body

Question 6

why do mammals need a double circulatory system?

Answer 6

high metabolic rate so cells require large amounts of oxygen and glucose

Question 7

what are the advantages of a double circulatory system?

Answer 7

blood flows more quickly to tissues as heart
increases pressure after it has passed through lungs
more efficient delivery of oxygen and nutrients
higher blood pressure

Question 8

what are the disadvantages of a single circulatory system?

Answer 8

blood pressure is reduced as blood passes through the capillaries of the gills
blood flow to the body is not very quick

Question 9

what does the heart do?

Answer 9

double pump helps keep oxygenated and deoxygenated blood separate
myogenic contractions

Question 10

what are myogenic contractions?

Answer 10

heart beat is initiated by muscle cells and not dependant on nervous or hormonal stimulations

Question 11

when do valves open?

Answer 11

when pressure above valve is greater than below

Question 12

when do semilunar valves open?

Answer 12

when the pressure in the ventricle is greater than the artery

Question 13

why do valves close?

Answer 13

to prevent back-flow of blood
lub-dub sound due to closing of valves

Question 14

what is the cardiac cycle (simple)?

Answer 14

atria contract (atrial systole)
ventricles contract (ventricular systole)
heart relaxes and fills (diastole)

Question 15

what is the cardiac cycle (complex)?

Answer 15

blood enters atria from vena cava and pulmonary vein
atria contract
volume decreases
pressure increases
blood enters ventricles down pressure gradient through atrioventricular valves
ventricles contract
volume decreases
pressure increases
blood is forced through semilunar valves into the aorta and pulmonary artery

Question 16

what is the blood pressure like in the atria?

Answer 16

thin muscle wall exert small pressure to push blood to ventricles (gradient)

Question 17

what is the blood pressure like in the right ventricle?

Answer 17

higher pressure than atria
has to push blood to lungs so thicker muscle wall than atria

Question 18

what is the blood pressure like in the left ventricle?

Answer 18

highest pressure as has to pump blood through the aorta to the rest of the body

Question 19

what is the septum?

Answer 19

separates two sides of the heart
stops deoxygenated and oxygenated blood from mixing
allows different pressures to be maintained each side

Question 20

what are the stages of a heart beat (simple)?

Answer 20

SAN initiates wave of excitation
atria walls contract
excitation delayed at AVN
passes excitation to bundle of His
base of ventricles contract
excitation transmitted to purkyne fibres in ventricle walls
blood pushed up arteries
heart goes into period of relaxation

Question 21

what are the stage of a heart beat (complex)?

Answer 21

sinoatrial node initiates wave of excitation
causes atria walls to contract
wave of excitation reaches atrioventricular node where it is delayed to allow full contraction of atria
excitation passes down highly conductive nerve tissue (bundle of His)
excitation transmitted to purkyne fibres causing ventricle to contract from apex upwards
pushes blood up arteries and empties ventricles
heart goes into period of relaxation as electrical impulse is terminated

Question 22

what does ECG stand for?

Answer 22

electrocardiogram

Question 23

what does the P wave show?

Answer 23

wave of excitation/signals from SAN spread through atria

Question 24

what does the QRS complex wave show?

Answer 24

depolarisation and excitation (contraction) of ventricles

Question 25

what does the T wave show?

Answer 25

diastole/repolarisation of ventricles