Cardiovascular System

Question 1

Is the blood in the aorta, left ventricle, and pulmonary artery oxygenated or deoxygenated ?

Answer 1

Aorta: oxygenated
Left ventricle: oxygenated
Pulmonary artery: deoxygenated

Question 2

What occurs between the alveoli and capillaries?

Answer 2

Gas exchange

Question 3

Which part of the brain has a role in the control of the heartbeat and how are message passed from this part of the brain to the heart?

Answer 3

Part of the brain: medulla oblongata

Type of message: nerve

Question 4

What normally prevents the membranes of the alveoli form sticking together during expiration?

Answer 4

The secretion of fluids in the inner surface of the alveoli

Question 5

Which chamber of the heart has the thickest walls?

Answer 5

Left ventricle

Question 6

When intense physical activity is anticipated, which factor in the blood will increase the frequency of sinoatrial signals to heart muscle?

Answer 6

Epinephrine

Question 7

What is the role of type 2 pneumocytes

Answer 7

To increase surface tension

Question 8

Which feature maintains a high concentration gradient of gases in the ventilation system

Answer 8

Thin-walled alveoli

Question 9

Which of the following describes arteries?

Answer 9

They have thick muscular walls

Question 10

Which muscles contract to cause air to pass into the lungs though the trachea

Answer 10

External intercostal muscles and diaphragm

Question 11

What is a role of the pacemaker or SA node?

Answer 11

To originate excitation in myogenic muscles

Question 12

What feature of alveoli adapts them to efficient gas exchange?

Answer 12

A dense network of capillaries surrounds them

Question 13

Capillaries surround the alveoli in the lungs. Which pair of statement correctly describes the concentrations of oxygen and carbon dioxide in the lungs

Answer 13

Oxygen: higher in the alveoli

Carbon dioxide: higher in the capillaries

Question 14

How are the insides of alveoli prevented from sticking together?

Answer 14

Method of prevention: surfactant

Produced by: type 2 pneumocytes

Question 15

List the the locations of chemosensors that detect changes in CO2 concentration in the blood

Answer 15

carotid artery aorta

Question 16

Explain how the brain is involved with increases in respiratory rates

Answer 16

The respiratory control centre in the medulla oblongata responds to stimuli from chemoreceptors in order to control ventilation
- Central chemoreceptors in the medulla oblongata detect changes in CO2 levels (as changes in pH of cerebrospinal fluid)
- Peripheral chemoreceptors in the carotid and aortic bodies also detect CO2 levels, as well as O2 levels and blood pH
During exercise metabolism is increased, which results in a build up of carbon dioxide and a reduction in the supply of oxygen
- These changes are detected by chemoreceptors and impulses are sent to the respiratory control centre in the brainstem
- Signals are sent to the diaphragm and intercostal muscles to increase the rate of ventilation (this process is involuntary)
- As the ventilation rate increases, CO2 levels in the blood will drop, restoring blood pH (also O2 levels will rise)
- Long term effects of continual exercise may include an improved vital capacity

Question 17

State the name of the enzyme in red blood cells that convert CO2 to a more soluable form

Answer 17

carbonic anhydrase

Question 18

Explain the events of the cardiac cycle including systole, diastole, and heart sounds

Answer 18

The cardiac cycle describes the series of events that take place in the heart over the duration of one heart beat
- It is comprised of a period of contraction (systole) and relaxation (diastole)

Systole

• Blood returning to the heart will freely flow from the atria to the ventricles as the AV valves kept open by the pressure in the atria
• The sinoatrial node (pacemaker) receives signals to fire when the ventricles are almost full (~70%)
• The contraction of the atria (atrial systole) causes blood to fill the ventricles to the maximum
• The signal from the SA node is transferred to the AV node and then via Purkinje fibres to cause the delayed contraction of the ventricles
• As the ventricles contract, the increase of pressure in the ventricles closes the AV valves, causing the first heart sound (‘lub’)

Diastole

• The increased pressure causes the semilunar valves to open and blood to flow away from the heart
• As the blood flows into the arteries, the pressure falls in the ventricles
• This causes some arterial back flow, which closes the semilunar valves and causes the second heart sound (‘dub’)
• When the pressure in the ventricle drops below the pressure in the atria the AV valves open and the cardiac cycle can repeat

Question 19

Explain how the structure of the artery allows it to carry out its function efficiently

Answer 19

• Thick wall to withstand high blood pressure
• Many muscle fibers to help pump blood
• Narrow lumen to maintain high pressure
• No valves as pressure is high enough to prevent back flow
• Thick outer layer of collagen to give strength

Question 20

An adaptation of people who live permanently in high altitude areas

Answer 20

They have more red blood cells/hemoglobin/higher lung capacity

Question 21

State possible cause of the curve shifting from myoglobin to hemoglobin

Answer 21

Decrease in pH levels

Question 22

Outline the events that occur within the heart that correspond to the QRS complex

Answer 22

• The QRS complex represents depolarization of the ventricles (i.e. ventricular contraction), triggered by signals from the AV node

Question 23

Describe the medical response to ventricle fibrillation

Answer 23

Using a defibrillator, which can be used to electrically restart the heat to a normal cardiac cycle and offset ventricle fibrillation

Question 24

List two factors that are possible causes of CHD and explain what is occurring in the blood vessels

Answer 24

1. ) sedentary lifestyle
2. ) smoking
   - Due to the sedentary lifestyle, fat deposits block the arteries and diminishes the diameter of the artery walls from pumping blood across the heart.

Question 25

Explain the oxygen dissociation curve of myoglobin

Answer 25

Myoglobin is an oxygen-binding molecule that is found in skeletal muscle tissue

• It is made of a single polypeptide with only one heme group and hence is not capable of cooperative binding
• Consequently, the oxygen dissociation curve for myoglobin is not sigmoidal (it is logarithmic)
• Myoglobin has a higher affinity for oxygen than adult hemoglobin and becomes saturated at lower oxygen levels
• Myoglobin will hold onto its oxygen supply until levels in the muscles are very low (e.g. during intense physical activity)
• The delayed release of oxygen helps to slow the onset of anaerobic respiration and lactic acid formation during exercise

Question 26

Outline how coronary thrombosis can be caused

Answer 26

Atherosclerosis is the hardening and narrowing of the arteries, due to the deposition of material commonly known as plaque

• Damage to the artery walls (e.g. due to high blood pressure) causes chronic inflammation, leading to the accumulation of lipids, cholesterol, cell debris and calcium
• fatty deposits develop in the arteries and significantly reduce the diameter of the lumen (stenosis) and reduces the elasticity of the artery wall needed for pulse flow
• This may lead to the formation of clots and blockages in the artery, and if this occurs in the coronary arteries (coronary thrombosis), it may lead to a heart attack