5 Blood Pressure And The Cardiac Cycle.

Question 1

What are the three main stages of the cardiac cycle?

Answer 1

Cardiac diastole
Atrial systole
Ventricular systole

Question 2

What is cardiac diastole?

Answer 2

When the whole heart is relaxed

Question 3

What is ventricular dispensability?

Answer 3

How much the heart can fill

Question 4

What is the name for inherent ability for ventricles to contract forcefully?

Answer 4

Ventricular contractility

Question 5

What is the Frank-Starling mechanism

Answer 5

The stroke volume increases in response to an increase in the volume of blood filling the heart when all other factors remain constant

Question 6

How does an increased amount of blood in the ventricles affect contraction to forcibly remove blood?

Answer 6

More blood in ventricles means increased stretch so increased contraction to forcibly remove blood

Question 7

How can the contraction of the ventricles be further increased?

Answer 7

By sympathetic activity - adrenaline and noradrenaline
- increased actin adn myosin cross bridges = increase in force

Question 8

How does and increased mean arterial pressure affect stroke volume and why?

Answer 8

Increased pressure means the heart has more ‘work to do’ to push against the blood thats already there
Decreased stroke volume

Answer 9

SNS
Noradrenaline
Adrenaline

Question 10

True/ false
The left ventricle completely empties during systole

Answer 10

False

Question 11

What is the normal percentage of ejection fraction?

Answer 11

55-75%

Question 12

What is ejection fraction an important measurement of?

Answer 12

Cardiac efficiency

Question 13

What are the effects of sympathetic stimulation on ionotropic action, action potential, cytoplasmic Ca2+ and contraction on ventricles?

Answer 13

Has a positive ionotropic action

action potential, cytoplasmic Ca2+ and contraction
- amplitude increased, and duration shortened

Question 14

What effect dows sympathetic stimulation have on chronotropic action on the SA node firing rate?

Answer 14

Positive chronotropic action

Question 15

What do cardiac pacemaker cells have that cause a slow inward leak of Na+ ions?

Answer 15

A specialised ionic current [IF]
f stands for funny

Question 16

How does sympathetic stimulation increase heart rate?

Answer 16

Sympathetic stimulation
Activates If [funny current]
Increases rate of depolarisation
Increases heart rate

Question 17

How does parasympathetic stimulation decrease heart rate?

Answer 17

Parasympathetic stimulation
Inhibits If
Slows rate of depolarisation
Lowers heart rate

Question 18

What structures do sympathetic nerves innervate in the heart?

Answer 18

Atria
Ventricles
Nodal and conducting tissue

Question 19

What tissues do parasympathetic nerves NOT innervate?

Answer 19

Ventricles

Question 20

What is the difference between positive and negative chronotropic effects?

Answer 20

Positive - increases heart rate
Negative - decreases heart rate

Question 21

What is the positive ionotropic effect?

Answer 21

Increases contractility of the heart

Question 22

With no other input, what is the SA node’s intrinsic rate?

Answer 22

~100 bpm

Question 23

What are the GI and the GS pathways?

Answer 23

GI - inhibitory pathway
GS - stimulatory pathway

Question 24

What two things determine the input pressure of the cardiovascular system?

Answer 24

Force of contraction and stroke volume

Question 25

What structures regulate the mean system pressure of the CVS?

Answer 25

Blood vessels regulate total resistance of system so control the mean system pressure

Question 26

What does blood pressure a measurement of?

Answer 26

The force against the walls of the arteries as blood is pumped through the body

Question 27

What does relaxation of the aorta do to movement of blood? And when does this occur?

Answer 27

Relaxation pushes blood towards systemic vasulature
This occurs in diastole

Question 28

What changes happen to the aorta in systole?

Answer 28

Aorta stretches to accommodate the blood being pushed in

Question 29

What is the difference between systolic and diastolic pressure?

Answer 29

Systolic - peak pressure in vasculature during each cardiac cycle
Diastolic - lowest pressure between each cardiac cycle

Question 30

Mean arterial pressure = 2/3 DBP + 1/3 SBP
Why is there fractions in this equation?
What would be the mean arterial pressure for someone with a BP of 120/80?

Answer 30

Fractions because at 60bpm the heart spends ~34% of each cardiac cycle in systole and ~66% in diastole
2/3[80] + 1/3[120] = 93mmHg

Question 31

How can mean arterial pressure be analogous to Ohms law?

Answer 31

Ohms law = V=IR and it describes the relationship betweeen flow, pressure and resistance
Mean arterial pressure = CO x SVR(systemic vascular resistance) [SVR can also be termed peripheral resistance]

Question 32

Why does blood pressure increase with age?

Answer 32

Aging = blood vessels become less compliant [stretchy] because of a loss of elastin from media layer
Accommodation for blood of systole is not as effective [loss of elasticity] and relaxation in diastole is more rapid [stiffer arteries]
This is called arteriosclerosis

Question 33

How is blood pressure over the venous system measured?

Answer 33

Using jugular venous pressure [JVP]
Gives an indirect measure of central venous pressure [CVP]
Patient at 45 degree angle
By ultrasound, neck contact photoplesmography, central line pressure measurements

Question 34

What receptors are usually responsible for the short term regulation of arterial blood pressure?

Answer 34

Baroreceptors

Question 35

Where is the cardioregulatory centre?

Answer 35

Medulla oblongata

Question 36

What effect does activation of a1 adrenoreceptors have on smooth muscle?

Answer 36

Causes contraction

Question 37

What effect does stimulation of B13adrenoreceptors have on smooth muscle?
And what receptors oppose this effect when stimulated?

Answer 37

Relaxation of smooth muscle
A2adrenoreceptors