Chapter 6- The Blood System Flashcards Preview

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Flashcards in Chapter 6- The Blood System Deck (42):
1

What did arteries do? Overview

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

2

What do arteries do? In depth?

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

3

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

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

4

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

By the arteries
Kidney- renal artery
Liver- hepatic artery

5

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

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

6

What do the muscle and elastic fibres assist in?

Maintaining blood pressure between pump cycles

7

What is systolic pressure?

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

8

What happens at the end of each heartbeat?

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)

9

What is vasoconstriction?

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

10

What does vasoconstriction do?

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

11

What do capillaries do?

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

12

What are capillaries?

Capillaries are the narrowest blood vessels

13

What is the main role of capillaries?

To transport blood through almost all tissues in the body

14

The walls of capillaries are very permeable what does allow?

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

15

What does veins do?

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

16

Where do veins transport blood from?

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

17

What is blood flow in veins assisted by?

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

18

What is the one anomaly in veins?

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

19

What do valves in veins do?

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

20

How do valves stop back flow?

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

21

What do valves ensure?

Blood flows in one direction

22

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

A separate circulation

23

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

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

24

What are the two types of circulations in humans?

1) pulmonary circulation - to and from lungs
2) the systemic circulation- to all other organs, including heart muscle

25

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

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

26

What are the causes of occlusion of coronary arteries

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

27

Consequences of occlusion of coronary arteries

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

28

Long term Consequences of occlusion of coronary arteries

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

29

What is the heart beat initiated by?

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

30

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

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

31

Why do the sinoatrial nodes initiate each heart beat?

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

32

What does the sinoatrial node act as?

A pacemaker- it sets the pace for the beating of the heart
If becomes defective it can be replaced by an artificial pacemaker

33

How does the sinoatrial node initiate a heart beat?

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

34

Explain a cardiac cycle:
0-0.1

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

35

Explain a cardiac cycle:
0.1- 0.15

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

36

Explain a cardiac cycle:
0.15-0.4

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

37

Explain a cardiac cycle:

0.4-0.0.45

1) semilunar valve closes due to drop in pressure
2) atrioventricular valves remain closed

38

Explain a cardiac cycle:
0.45-0.8

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

39

How can heart rate be increased or decreased?

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

40

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

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

41

What does epinephrine do?

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

42

What did William Harvey prove?

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

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