Lecture 4 - Cardiovascular System

Question 1

Explain the 4 functions of the heart

Answer 1

Ensuring a one way blood flow
Generating blood pressure - Contractions of the heart generates blood pressure which ensures blood flow
Routing of blood in pulmonary and systemic ways - separation ensures better oxygenation of the blood
Regulating blood supply - changing rate force of each contraction to match the demands set by the muscles

Question 2

Describe the conduction function of the heart

Answer 2

APs are created by the SA node which travels through to the Av node and through the bundle of Hiss through to the purkinje fibres to the apex (ventricle wall) which generates contraction

Question 3

What is auto-rhythmicity and how are APs made

Answer 3

Auto rhythmicity is the ability of cardiac muscle to generate its own APs, APs travel to other cardiac cells which open voltage gated Na+ channels

Question 4

5 stages of sympathetic control

4 stages of parasympathetic control

Answer 4

Dilate bronchioles 
Increase Heart rate 
Secrete adrenaline
Decrease digestive secretion 
Decreases motility 

Para:
Constricts bronchioles 
Decreases heart rate 
Increases secretion 
Increases motility

Question 5

What are the 2 nerves involved in parasympathetic control and describe it

Answer 5

Preganglionic - brain stem to terminal ganglia within the myocardial wall
Postganglionic - SA node av node coronary blood vessels & atrial myocardium

Has tonic control of heart rate and inhibitory influence at rest with a removal at exercise onset
Little effect on SV acetylcholine causes plasma membrane to become more permeable to k+

Question 6

What happens during sympathetic control

Answer 6

Increases Hr and contractility with a greater force of contraction whilst decreasing ESV

However it has a limited ability to increase HR
Norepinephrine increases rate and degree of cardiac depolarisation, so frequency and amplitude of APs increase

Question 7

Define heart rate variability and what it is sensitive to

Answer 7

The analysis of the variety of subsequent RR intervals
High variability is healthy
Gives us an insight into ANS control

Question 8

What are the typical values for each of the cardiac hemodynamic factors

Answer 8

Q = 5L per min
SV = 70ml per stroke
Heart rate = 70-75bpm
Innate heart rate 90-100bpm

Question 9

What does increasing HR do to EDV SV Q and VR

Answer 9

Decreases them all

Question 10

What are the 2 types of chemoreceptors and what do they measure

Answer 10

Peripheral CO2 pH and O2 concentrations

Central CO2

Question 11

Why does pH decrease when CO2 increases
How do we remove CO2
In what instance is this increased

Answer 11

Decreases because CO2 is transported mainly as carbonic acid

This leads to parasympathetic withdrawal and sympathetic instance therefore increased HR Q
So there is greater blood flow through the lungs and therefore more CO2 is expired

Exercise increases this

Question 12

Define the Fick equation
How do we calculate SV
What is Starling’s law

Answer 12

Q * arterial and venous 02 difference
EDV- ESV
Starlings law is when EDV increases with VR and ESV decreases with stretch

Question 13

What exercise intensity does SV increase to

Answer 13

40% of VO2

Question 14

What is the relationship between heart rate and sub max work and what is the conconi deflection

Answer 14

Heart rate linearly increases proportionally to oxygen consumption

Conconi deflection is when heart rate increases at a decreased rate once past the anaerobic threshold

Question 15

What happens to systolic and diastolic blood during exercise

Answer 15

Systolic = linearly decreases with dynamic exercise intensity and increases with force of contraction

Diastolic smaller increases with intensity and increases with isometric contraction

Question 16

What happens to blood pH plasma volume and oxygen content during exercise

Answer 16

Blood pH: lowered due to affect of dissociation of lactic acid and transport of O2

Plasma volume: decreases hemocrit increases from 45to 50, caused by change in blood pressure then later due to sweating

Oxygen content : increased AVO2 difference decreased o2 venous content oxyhemoglobin curve shifts to the right

Question 17

What is the influence of endurance training on Sv hr and Q

Peak VO2 equation

What is the influence of endurance on morphological aspects

Answer 17

Increased SV at rest and exercise decreased resting HR

Q * AV VO2

Increased left ventricle mass and wall thickness

Question 18

How do we characterise an athletes heart

Answer 18

Bradycardia
Hypertrophy
Cardiomegaly

If found in non athlete there are issues

Question 19

Define cardiovascular drift and where it occurs

Answer 19

The upwards drift in heart rate with a progressive decline in SV whilst maintaining the same exercise intensity

Occurs after 10mins of exercise and around 50-75% of VO2 max

Question 20

What are the effects of hyperthermia

Answer 20

Hyperthermia leads to decreased Sv and therefore Q therefore increased systemic vascular resistance
And vasoconstriction of the CBF
Decreased heat dissipation

Question 21

What are the % changes in Sv and q due to dehydration

Answer 21

28% in Sv and therefore 18% In Q and and increase in core temperature

Question 22

What is hypoyvelemia

Answer 22

Dehydration of 3-5% equates to a 3-5% decrease in blood plasma volume

Reduces VR EDV SV
Accounts for 100% decrease in SV when dehydration but not hyperthermic

Accounts for 50% when both d and H
Dehydration alone = 7% decrease in SV