6. Human Physiology : 6.2 Blood system

Question 1

What is systolic pressure?

Answer 1

The pressure exerted when the heart pumps blood into aorta

Pressure between 120-200 mm Hg.

Question 2

What are the three layers of arterial walls?

Answer 2

Tunica Intima - tunica intima facing the lumen is lined with endothelium

Tunica media

Tunica adventitia (tunica externa)

Question 3

What are the three layers of arterial walls composed of?

Answer 3

Tunica Intima :
- endothelium that lines the lumen of all vessels and form a smooth, friction reducing lining

Tunica media :
- mainly made of smooth muscle cells and elastic fibres arranged in roughly spiral layers

Tunica adventitia (tunica externa) : 
- consists of loosely woven collagen fibres that protect the blood vessel and anchor it to surrounding structures

Question 4

What is vasoconstriction?

Answer 4

The process where:
When heart contracts, it exerts a high pressure called systolic pressures.
The circular muscles surrounding the arteries resist the outward pressure and constrict.

Question 5

What is vasodilation?

Answer 5

When heart relax, it exerts a low pressure called diastolic pressures.
The smooth muscles surrounding the arteries relax.

Question 6

What do vasodilation and vasoconstriction do for the blood flow of the body?

Answer 6

• regulates body temperature and slowing blood when a person is wounded

Question 7

What occurs in veins?

Answer 7

• transports blood from tissues and return it to the atria
• atria: upper chambers of the heart
• pressure is lower so no thick walls
• blood flow in veins is supported by skeletal muscles, they squeeze the veins like a pump

Question 8

Why do patients who are in coma need to stay immobilised for long periods of time?

Answer 8

To prevent blood boils and bed sores.

Question 9

How are capillary network formed?

Answer 9

The size and wall structure of arteries are too big for the nutrients and oxygen in blood to reach every cell in body so they form into smaller arterioles that forms very fine blood vessels called capillaries
These capillaries fuse to form venules, venules fuse to form veins
Together they form the capillary networks

Question 10

What happens through the capillary network?

Answer 10

They allow exchange of materials, oxygen and nutrients with cells in tissues and waste products
Blood flow is slowest in here to allow time for exchange with tissues

Question 11

What is the liquid part of blood that passes through capillaries composed of?

Answer 11

Composed of sugars, water, salts, fatty acids, amino acids, coenzymes and hormones, waste product from cells

Question 12

Differentiate the layers of arteries, veins and capillaries.

Answer 12

Arteries:

• tunica media
• tunica externa
• tunica intima

Veins:

• tunica media
• tunica externa
• tunica intima

Capillaries:
One layer of endothelial cells

Question 13

What happens in the right side of the heart?

Answer 13

1. Blood flow into right atrium
2. Atrium contracts - blood flows into right ventricle through tricuspid valve
3. Ventricle is full - tricuspid valve shuts
4. Ventricle contracts - blood leaves heart and to lungs `

Question 14

What happens in the left side of the heart?

Answer 14

1. Blood from lungs to left atrium
2. Atrium contracts, blood flows from left atrium into left ventricle through bicuspid valve
3. Ventricle is full - mitral valves close and prevents backflow
4. Ventricle contracts - blood leaves through aortic valve to aorta and to body

Question 15

What are the nerves that control the rate of the heart?

Answer 15

Nerve that makes the heart beat faster: cardiac accelerator nerve

Nerve that makes the heart beat slower: vagus nerve

Question 16

How does the cardiac accelerator nerve works?

Answer 16

Signalling the heart to beat faster:

• Increased heart rate = more respiration
• More respiration = need more oxygen and produce more CO2
• Increased CO2 in blood will decrease pH
• Cardiovascular centre will sense the increase in pH and send impulses along the cardiac accelerator nerve to SA to increase heart rate

Question 17

How does the vagus nerve work?

Answer 17

• As impulses are sent to SA to increase heart rate, the heart pumps faster
• More oxygen is sent to body tissues and more CO2 is removed
• Once activity is stopped, heart rate slows down

Question 18

What do the epinphrine or adrenaline do for the body?

Answer 18

• strong emotions cause the hormones to be released into blood stream
• blood carries it all over the heart
• hormone increases heart rate by stimulating SA node to emit electrical signals at a faster rate

Question 19

What are atheromas?

Answer 19

Fatty deposits caused by high blood concentrations of low density lipoprotein in the arterial walls next to the endothelial cells

Question 20

What happens if the coronary artery is blocked?

Answer 20

the cells in that part of the heart will die and cause myocardial infarction (heart attack)

Question 21

What is angina and what causes it?

Answer 21

The buildup of plaque takes time

The restricted flow will cause pain due to the cells not having oxygen and nutrients

Question 22

What are the causes of plaque formation?

Answer 22

Leads to atherosclerosis and the increase in cardiovascular disease.

High blood concentrations 
Diabetes causing high blood concentration 
Smoking And stress 
Diets containing high levels of fats 
Certain infections with bacteria