Chapter 6- The Blood System

Question 1

What did arteries do? Overview

Answer 1

Arteries are vessels that convey blood from the heart the tissues of the body

Question 2

What do arteries do? In depth?

Answer 2

1) the main pumping chamber of the heart are the ventricles - they have thick strong muscles in their walls that pump blood into the arteries
2) artery walls work with the heart to facilitate and control blood flow

Question 3

What are the two tissues in the walls of arteries that help control blood flow?

Answer 3

Elastic and muscle tissue- contribute to toughness of wall and withstand constantly changing blood pressure

Question 4

What is each organ supplied with blood by? 2 major examples be

Answer 4

By the arteries
Kidney- renal artery
Liver- hepatic artery

Question 5

What are the 3 layers that the artery is composed of?

Answer 5

1) tunica external- a tough outer layer of connective tissues
2) tunica media- a thick layer containing smooth muscle and elastic fibres
3) tunica intimidate - a smooth endothelium forming the lining of the artery

Question 6

What do the muscle and elastic fibres assist in?

Answer 6

Maintaining blood pressure between pump cycles

Question 7

What is systolic pressure?

Answer 7

Blood entering arteries is at high pressure- peak pressure reached is called systolic pressure- pushes wall of artery outwards, widening lumen and stretching elastic fibres in wall; thus storing potential energy

Question 8

What happens at the end of each heartbeat?

Answer 8

The pressure in the arteries falls sufficiently for the stretch elastic fibres to squeeze the blood in the lumen - saves energy and prevents mim. Pressure in artery (diastolic pressure)

Question 9

What is vasoconstriction?

Answer 9

Circular muscles in the wall the artery form a ring so when they contract, the circumference is reduced and the lumen narrowed- increases blood pressure in arteries

Question 10

What does vasoconstriction do?

Answer 10

Or arterioles Restricts blood flow to part of the that they supply (opposite is vasodilation)

Question 11

What do capillaries do?

Answer 11

Blood flows through tissues in capillaries with permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary

Question 12

What are capillaries?

Answer 12

Capillaries are the narrowest blood vessels

Question 13

What is the main role of capillaries?

Answer 13

To transport blood through almost all tissues in the body

Question 14

The walls of capillaries are very permeable what does allow?

Answer 14

Allows part of plasma to leak our and form tissue fluid- contains oxygen, glucose etc - fluid flows btween the cells and tissue allowing the cell to absorb useful substances and excrete waste products- then re-enters capillary network

Question 15

What does veins do?

Answer 15

Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart

Question 16

Where do veins transport blood from?

Answer 16

From capillary networks - blood is at much lower pressure than it was in arteries so walls are not as thick as arteries - can therefore dilate to become much wider and hold more blood than arteries

Question 17

What is blood flow in veins assisted by?

Answer 17

Gravity and by pressures exerted on them by other tissues, especially skeletal muscles

Question 18

What is the one anomaly in veins?

Answer 18

The hepatic portal vein - it does not carry blood back to heart instead it carries blood from the stomach to the intestines to the liver

Question 19

What do valves in veins do?

Answer 19

Valves in veins and the heart ensure circulation of blood by preventing back-flow

Question 20

How do valves stop back flow?

Answer 20

1) if blood starts to flow backwards, it gets caught in the flaps of the pocket valve, which fills with blood, blocking the lumen of the vein
2) when blood flows towards the heart, it pushes the flaps to the sides of the vein. The pocket valve therefore opens and blood can flow freely

Question 21

What do valves ensure?

Answer 21

Blood flows in one direction

Question 22

What are the lungs used by mammals for gas exchange supplied with blood by?

Answer 22

A separate circulation

Question 23

Why is there a need for a separate circulation for lungs circulation in animals?

Answer 23

Blood capillaries in lungs cannot withstand high pressures so blood is pumped to them at relatively low pressure- so after passing through lungs blood pressure is low so much return to heart before going to other organs

Question 24

What are the two types of circulations in humans?

Answer 24

1) pulmonary circulation - to and from lungs

2) the systemic circulation- to all other organs, including heart muscle

Question 25

Why is it essential that the blood from both separate circulations do not mix?

Answer 25

As pulmonary circulation recjves deoxygenate blood that had returned from the systemic circulation and the systemic circulation recurve so blood that had been oxygenated by the pulmonary circulation

Question 26

What are the causes of occlusion of coronary arteries

Answer 26

Lipoproteins (LDL) containing fats etc accumulate and phagocytes are attracted by signals from endothelium cells- smooth muscles cells migrate to form a tough cap over the at herons and artery walls budge- narrowing the lumen and impeding blood flow

Question 27

Consequences of occlusion of coronary arteries

Answer 27

Leads to a lack of oxygen - causes pain, impairs the muscles ability to contract, heart beats faster as it tries to maintain blood circulation which can cause ruptures and then blood clots block arteries

Question 28

Long term Consequences of occlusion of coronary arteries

Answer 28

1) high blood pressure
2) chronic high blood glucose conc.
3)

Question 29

What is the heart beat initiated by?

Answer 29

A group of specialised muscle cells in the right atrium called the sinoatrial node

Question 30

The heart beat is called myogenic- what does that mean?

Answer 30

It can contract without stimulation from motor neurone- generate in the muscle itself

Question 31

Why do the sinoatrial nodes initiate each heart beat?

Answer 31

Because they are the fastest to depolarise in each cardiac cycle which causes adjacent cells to also contract

Question 32

What does the sinoatrial node act as?

Answer 32

A pacemaker- it sets the pace for the beating of the heart

If becomes defective it can be replaced by an artificial pacemaker

Question 33

How does the sinoatrial node initiate a heart beat?

Answer 33

By contracting and simultaneously sending out a electoral signal that spreads through the walls of the atria - this can happen because there are interconnections between adjacent fibres

Question 34

Explain a cardiac cycle:

0-0.1

Answer 34

0-0.1

1) Atria contracts - pumps blood from atria to ventricles through open atrioventricular valves
2) semilunar valves are closed and no more blood is pumped in

Question 35

Explain a cardiac cycle:

0.1- 0.15

Answer 35

1) ventricles contract that causes atrioventricular valves to close
2) semilunar valve remains closed

Question 36

Explain a cardiac cycle:

0.15-0.4

Answer 36

1) pressure in the ventricle rises above pressure in arteries so the semilunar valve opens and blood is pumped from the ventricles into the arteries
2) pressure rises in atria as blood drains into them from the veins and they fill

Question 37

Explain a cardiac cycle:

0.4-0.0.45

Answer 37

1) semilunar valve closes due to drop in pressure

2) atrioventricular valves remain closed

Question 38

Explain a cardiac cycle:

0.45-0.8

Answer 38

1) atrioventricular valves open as pressure drops in ventricles
2) blood from veins drain into the atria and there into ventricles

Question 39

How can heart rate be increased or decreased?

Answer 39

By impulses brought to the heart through two nerves from the medulla of the brain

Question 40

The cardiovascular centre (region of medulla) receives inputs from receptors that monitor blood pressure, pH and oxygen- what are the 2 outcomes?

Answer 40

1) of low blood pressure, low oxygen and low pH - heart rate needs to be sped up
2) high blood pressure, high oxygen, high pH - heart rate slow down

Question 41

What does epinephrine do?

Answer 41

Increases the heart rate to prepare for vigorous physical activity - hormone which is sometimes called adrenalin

Question 42

What did William Harvey prove?

Answer 42

1) Demonstrated that blood flow through larger vessels in unidirectional, with valves to prevent back flow
2) showed that rate of blood flow was far to high for blood to be consumed by the body- proved it must be recycled