Cardiorespiratory system

Question 1

What is homeostasis?

Answer 1

Homeostasis is the property of a system in which a variable is actively regulated to remain nearly constant. In the body it is the maintenance of the internal environment, faced with variation in the external environment, activity, and intake of nutrients

Question 2

How is homeostasis maintained in the body?

Answer 2

The core mechanism is a negative feedback loop

Question 3

What are the functions of the cardiovascular system?

Answer 3

Rapid transport & distribution of nutrients and waste products
Distribution of water, electrolytes & hormones
Exchange between blood vessels and interstitial fluid
Infrastructure of immune system
Temperature regulation

Question 4

What is pulmonary circulation?

Answer 4

Blood going to the lungs under low resistance and pressure

Question 5

What is systemic circulation?

Answer 5

Blood going to the rest of the body under high resistance and pressure

Question 6

What is the arterial system?

Answer 6

Blood flowing away from the heat in arteries under high pressure

Question 7

Why is venous return important?

Answer 7

The heart can only pump out blood that comes back

Question 8

Define systolic blood pressure

Answer 8

Blood pressure when the heart contracts

Question 9

Define diastolic blood pressure

Answer 9

Resting blood pressure when the heart isn’t contracting

Question 10

Describe the atria

Answer 10

Thin-walled (compare with ventricles)
Receive venous blood (reservoir function)
Right atrium receives systemic venous blood, left atrium receives oxygenated venous blood
Act as pumps to fill ventricles at low pressures
Produce the hormone atrial natriuretic peptide (ANP)

Question 11

Describe the ventricles

Answer 11

Eject blood into the arterial systems including to lungs
Left ventricle has a thicker wall than the right ventricle and generates higher pressures – blood to systemic circulation

Question 12

What structure within the heart initiates the beat?

Answer 12

The sinoatrial node. It’s the physiological pacemaker, maintaining the heart’s rhythmicity.

Question 13

What does the P wave of an ECG correspond to?

Answer 13

Atrial depolarisation

Question 14

What does the QRS complex of an ECG correspond to?

Answer 14

Ventricular depolarisation

Question 15

What does the T wave of an ECG correspond to?

Answer 15

Ventricular repolarisation

Question 16

What does the PR interval of an ECG correspond to?

Answer 16

Atrioventricular conduction

Question 17

What does the QT interval of an ECG correspond to?

Answer 17

Duration of ventricular activation

Question 18

Define tachycardia

Answer 18

A fast resting heart rate (>100 bpm)

Question 19

Define bradycardia

Answer 19

A slow resting heart rate (<60 bpm)

Question 20

Cardiac output =

Answer 20

heart rate X stroke volume

Question 21

What does cardiac output measure?

Answer 21

The volume of blood ejected from the heart per minute (litres per minute)

Question 22

What is stroke volume?

Answer 22

The volume of blood pumped from the left ventricle per beat.

Question 23

What factors influence stroke volume?

Answer 23

Intrinsic factors: preload (the initial stretching of the cardiomyocytes prior to contraction), afterload (the pressure against which the heart must work to eject blood during systole)
Extrinsic factor: contractility (via nerve input)

Question 24

Starling’s law of the heart

Answer 24

The energy of contraction of a cardiac muscle fibre, like that of a skeletal muscle fibre, is proportional to the fibre length at rest.

Question 25

Define the term 'mean arterial pressure'

Answer 25

Average blood pressure at the tissues

Question 26

Mean arterial pressure=

Answer 26

(Cardiac output x total peripheral resistance) + central venous pressure

Question 27

Why is controlling blood pressure important?

Answer 27

BP too low: poor perfusion e.g. lack of blood to brain on standing up BP too high: excessive pressure at the small vessels in tissues, loss of fluid to tissue; excessive afterload on heart

Question 28

What are the functions of the respiratory system?

Answer 28

Inhalation and exhalation | Exchange of gases between the lungs and the blood, and between the blood and body tissues

Question 29

What does respiration refer to?

Answer 29

All the processes involved in the exchange of O2 and CO2 between the cells and the external environment

Question 30

Regulatory mechanisms for the respiratory system ensure that...

Answer 30

Ventilation of the lungs is matched with its blood supply (perfusion) The O2 supply and CO2 removal vary appropriately with activity eg. in exercise The regulation of respiration another example of homeostasis

Question 31

Why do mammalian lungs have a large surface area?

Answer 31

Increased area for diffusion, making gas exchange efficient

Question 32

Describe the process of respiration

Answer 32

Ventilation --> gas exchange in the lungs --> gas exchange between capillaries and tissues --> metabolism --> bulk transport via circulation

Question 33

Pressure of a system=

Answer 33

The sum of the separate (partial) pressures that each gas would exert if it alone occupied the entire volume

Question 34

Define the term 'physiological dead space'

Answer 34

The volume of air which is inhaled that does not take part in the gas exchange

Question 35

Why does some of the air inhaled not take part in gaseous exchange?

Answer 35

It remains in the conducting airways, or reaches alveoli that are not perfused or poorly perfused.

Question 36

What is anatomical dead space?

Answer 36

The portion of the airways (such as the mouth and trachea to the bronchioles) which conducts gas to the alveoli. No gas exchange is possible in these spaces.

Question 37

What is alveolar dead space?

Answer 37

Alveoli which have little or no blood flowing through their adjacent pulmonary capillaries, i.e., alveoli that are ventilated but not perfused, and where, as a result, no gas exchange can occur

Question 38

Which substances is blood specialised to transport?

Answer 38

Oxygen and carbon dioxide

Question 39

Give the equilibrium of carbon dioxide and bicarbonate in the blood

Answer 39

CO2 + H2O ⇌ H2CO3 ⇌ H+ + (HCO3)-

Question 40

Why does the formation of bicarbonate never get to equilibrium?

Answer 40

It never goes to equilibrium because the products are removed by two mechanisms: 1) chloride/ bicarbonate exchange (‘chloride shift’) 2) H+ buffering by haemoglobin

Question 41

Why is it important to regulate [CO2] in the blood?

Answer 41

If [CO2] gets too high, it could lead to the blood becoming too acidic. If the blood pH drops below 7.2, then very soon the brain won't be able to function normally

Question 42

What is hyperventilation?

Answer 42

An increased ventilation rate

Question 43

What is hypoventilation?

Answer 43

A decreased ventilation rate

Question 44

What are chemoreceptors?

Answer 44

A chemoreceptor is a specialised sensory receptor cell which responds to a chemical substance and generates a biological signal

Question 45

What do the carotid and aortic bodies detect?

Answer 45

They detect changes primarily in oxygen. They also sense increases in CO2 partial pressure and decreases in arterial pH.

Question 46

What is the pulmonary circulation loop?

Answer 46

The pulmonary circulation loop is the part of the circulatory system which carries deoxygenated blood away from the right ventricle of the heart, to the lungs, and returns oxygenated blood to the left atrium

Question 47

What is the systemic loop?

Answer 47

A loop through the rest of the body to provide oxygenated blood, from the left ventricle to the right atrium.

Question 48

What is the main function of the heart?

Answer 48

The heart produces the force that causes blood to circulate

Question 49

What are baroreceptors?

Answer 49

They monitor blood pressure

Question 50

What do baroreceptors do in response to low blood pressure?

Answer 50

They increase sympathetic stimulation and decrease parasympathetic stimulation of the heart, resulting in an increase in heart rate and force of contraction