8. Transport in Mammals

Question 1

What is the circulatory system in mammals called?

Answer 1

a closed blood system, made up of vessels containing blood

Question 2

What type of circulatory system do mammals have?

Answer 2

double circulation, passes through the heart twice

Question 3

Explain what 2 systems make up a double circulatory system?

Answer 3

systemic circulation: oxygenated blood goes from the heart to all of the body except the lungs, and back to the heart

pulmonary circulation: deoxygenated blood goes from the heart to the lungs, and back to the heart as oxygenated blood

Question 4

Describe the structure and function of arteries

Answer 4

tunica intima: a layer lining tissue called endothelium, a layer of flat cells called squamous epithelium, a layer of elastic fibres, smooth and minimises friction

tunica media: smooth muscle, collagen and elastic fibres

tunica externa: elastic fibres and collagen fibres

• responsible for vasoconstriction and vasodilation
• 2 types, muscular arteries and elastic arteries, depending on the amount of elastic fibres in the tunica media
• high pressure
• carries blood AWAY FROM the heart

Question 5

Describe the structure and function of capillaries

Answer 5

• arteries branch out to form capillaries
• takes blood as close as possible to all cells for rapid transfer of substances between cells and blood
• extremely thin walls made of a single layer of endothelial cells
• low pressure
• partially permeable due to tiny gaps in between endothelial cells

Question 6

Describe the structure and function of veins

Answer 6

• capillaries join to form veins
• very low pressure
• compared to arteries, thinner tunica media and fewer elastic fibres and muscle fibres
• has semilunar valves to help move blood towards the heart
• carries blood BACK TO the heart

Question 7

What is tissue fluid?

Answer 7

• leaked plasma from the gaps between the cells in the walls of the capillaries
• on the arterial end, there is more protein in blood plasma than in tissue fluid, so water moves from capillaries into tissue fluid by osmosis (net movement of water out of the capillary)
• on the venule end, there is a net movement of water into the capillary

Question 8

What does excessive tissue fluid cause?

Answer 8

oedema, when blood pressure is too high and too much fluid is forced out of the capillaries, accumulating in the tissues

Question 9

What is the function of tissue fluid?

Answer 9

exchanges of materials between cells and blood occur through tissue fluid

Question 10

Draw and label the heart (21)

Answer 10

right side: deoxygenated
vena cava (2, one from body, one from head)
valve in vena cava
pulmonary artery
pulmonary semilunar valve
right atrium
tricuspid valve
right ventricle
tendon

left side: oxygenated
aorta
pulmonary vein
valve in pulmonary vein
left atrium
aortic semilunar valve
bicuspid valve
papillary muscle
left ventricle
thick muscular wall of left ventricle
septum

Question 11

What is the cardiac cycle and how many times does it occur in 1 minute for humans?

Answer 11

the sequence of events that take place during one heartbeat, average 70 bpm

Question 12

Explain the 3 stages of the cardiac cycle

Answer 12

1) atrial systole: both atria contract, blood flows into ventricles, valves close to prevent backflow

2) ventricular systole: both ventricles contract, atrioventricular (_cuspid) valves pushed shut by the pressure in the ventricles, semilunar valves pushed open, flood flows into the arteries

3) ventricular diastole: atria and ventricles relax, semilunar valves pushed shut, blood flows from veins through the atria and into the ventricles

Question 13

What is the pressure in atrial systole?

Answer 13

higher in the atrium, opens atrioventricular valve

Question 14

What is the pressure in ventricular systole?

Answer 14

higher in the ventricle, closes atrioventricular valves

Question 15

What is the pressure in ventricular diastole?

Answer 15

higher in the arteries, closes semilunar valves

Question 16

How long does atrial systole last?

Answer 16

0.1 seconds

Question 17

How long does ventricular systole last?

Answer 17

0.3 seconds

Question 18

How long does ventricular diastole last?

Answer 18

0.5 seconds

Question 19

What is myogenic?

Answer 19

cardiac muscle is myogenic because it contracts and relaxes even without nerve impulses stimulate movement

Question 20

What is the sinoatrial node?

Answer 20

SAN, or the pacemaker, is a patch of cardiac muscles in the right atrium of the heart that sets a rhythmic pattern for all the other cardiac muscle cells in the heart.

Question 21

Explain a heartbeat

Answer 21

1) SAN contracts, produces an electrical excitation wave across muscles in the atria, atrial walls contact

2) excitation wave travels to the atrioventricular node (AVN) which delays the impulse, ventricular walls contract a fraction of a second after atrial walls

3) excitation wave moves down the septum, along the fibres known as Purkyne tissue, reaches the base and moves upwards, causing ventricles to contract

Question 22

Where is the atrioventricular node?

Answer 22

the AVN is another patch of cardiac muscle, located in the septum