Cardiovascular System

Question 1

Where is the heart located

Answer 1

On the 5th intercostal space along the mid calcuviar line

Question 2

Describe the heart

Answer 2

Right atrium forms the right border
Right ventricle forms the inferior border and most of the anterior surface
Left ventricle form the left border and apex
Most of left ventricle is hidden in this view

Question 3

Describe the ascending aorta

Answer 3

Carry O2 blood to the rest of the body
Comes out of the left ventricle

Question 4

Describe the pulmonary trunk

Answer 4

Is an aorta
Going to the lungs coming out of the right side of the heart
Takes deoxygenated blood to the lungs

Question 5

Describe the superior and inferior vena cava

Answer 5

Bring deoxygenated blood from the body to the right atrium

Question 6

Describe the pulmonary veins

Answer 6

Bring oxygenated blood back to the left atrium

Question 7

Describe the aorta

Answer 7

Takes oxygenated blood to the body

Question 8

Describe the 3 layers

Answer 8

Intima
Media
Adventitia

Question 9

What is the pericardium

Answer 9

Is the outermost layer and is made up of two sacs

Question 10

Describe the fibrous pericardium

Answer 10

Outer sac consisting of fibrous tissue
It is continuous with the tunica adventitia of the great blood vessels above
It is fibrous, in elastic and protects and prevents over - distension of the heart

Question 11

Describe the serous pericardium

Answer 11

Is the inner layer
It is a continuous double layer of serous membrane
It is a single layer of endothelial cells, folded over itself, forming a double membrane around the heart with an enclosed space in between the layers
Parietal pericardium - outer layer of the serous pericardium, it lines the fibrous pericardium
Visceral pericardium- is the inner layer of the pericardium, firmly attached to the myocardium

Question 12

Describe the myocardium

Answer 12

Specialised cardiac muscle found only in the heart
It is striated but is not under voluntary control
Each fibre has a nucleus and one or more branches and is rich in mitochondria to supply its high energy needs
The ends of the cells and their branches are in very close contact with the ends and branches of adjacent cells

Question 13

Further describe the myocardium

Answer 13

Arrangement gives cardiac muscle the functionality of a sheet of muscle rather than a number of individual cells
Because of the end to end continuity of the fibres each one doesn’t need a separate nerve supply
When an impulse is initiated, it spreads from cell to cell via the branches and intercalated discs over the whole sheet of muscle
The sheet arrangement of the myocardium enables the whole heart to contract in a coordinated and efficient manner

Question 14

Describe the endocardium

Answer 14

This thin membrane lines the chambers and valves of the heart
It consists of a single layer of flattened epithelial cells and is continuous with the endothelium lining the blood vessels
It is very smooth to minimise friction as the blood flows over it

Question 15

Describe the chordae tendineae

Answer 15

Attached valves to muscle to prevent valves turning inside out
Fibrous tendon

Question 16

Describe the papillary muscles

Answer 16

Contracts to hold onto valves to keep them closed

Question 17

Describe cardiac myocytes

Answer 17

Are striated muscle cells
Similar to skeletal muscle
Don’t need nervous input to contract
Spontaneously depolarise
They are electrically coupled
Depolarisation readily spreads via intercalated discs
Depolarisation of myocytes allows Ca2+ ions to enter and causes contraction
Rapid spread of depolarisation via the conduction system allows the heart to depolarise in a co-ordinated fashion

Question 18

Describe the cardiac cycle

Answer 18

The heart goes through a rhythmic cycle of contraction and relaxation
Ventricular contraction = systole
Ventricular relaxation = diastole
Systole refers to ventricular systole
Atrial,systole is not included as part of systole as it occurs when the ventricles are relaxed

Question 19

Describe the electrical system

Answer 19

The SA node cells depolarise fastest and set the rate of contraction
Depolarisation spreads through the atria to the atrioventricular node ( slows down the message from the atria to the ventricle )
Bundle of His
Left & right bundle branches
Purkinje fibres carry the electrical activity throughout the ventricular myocardium

Question 20

What is shown at different stages of a ECG deflections

Answer 20

P wave = atrial depolarisation
P-R interval = time from start of atrial depolarisation to start of ventricular depolarisation
QRS complex = ventricular depolarisation
S-T segment = period between ventricular depolarisation and re polarisation
T way = repolarisation of the ventricles
U wave = depolarisation of purkinje fibres

Question 21

Describe the autonomic innervation of the heart

Answer 21

Cells in the SA node and AV node have sympathetic and parasympathetic innervation
Parasympathetic activity decreases heart rate through release of acetylcholine
Sympathetic activity increases heart rate through release of noradrenaline
Cells in the ventricular myocardium only have sympathetic innervation
Sympathetic activity increases the force of contraction through the release of noradrenaline

Question 22

What is in circulation

Answer 22

Large arteries, smaller arteries, arterioles, capillaries, venues, smaller veins and large veins

Question 23

Describe the 3 vessel wall layers

Answer 23

Tunica adventitia = thin layer of collagen with nerve and blood supply
Tunica media = smooth muscle layer with an elastic layer
Tunica intima = elastic tissue with an inner layer endothelium

Question 24

Describe gases exchange

Answer 24

Capillaries have a single layer of endothelial cells that allow :
- gases and nutrients to diffuse
- water to move through depending on hydrostatic and osmotic pressure

Question 25

Describe hydrostatic pressure

Answer 25

Higher the hydrostatic pressure the more the fluid moves out of the capillaries and into the surrounding tissues

Question 26

Describe osmotic pressure

Answer 26

Osmotic pressure concentration of ions dissolved in the fluid
Across a semipermeable membrane the water will flow from high concentration to low concentration

Question 27

Describe cardiac output

Answer 27

Is the volume of blood pumped out of the heart in one minute
CO = stroke volume x heart rate

Question 28

What are factors affecting cardiac output

Answer 28

Change in stroke volume:
- reduced strength of contraction of the cardiac muscles ( decreases SV )
- reduction in filling of the left ventricle ( decreases SV )
Change in heart rate:
- reduced heart rate , amount of blood expelled in one minute

Question 29

Describe arterial pulse and pulse points

Answer 29

Blood pumped into aorta stretches the wall and creates a pressure wave or shock wave which is very quickly transmitted through the walls of the arterial system
Pulse can be felt where arteries are close to the surface or pass over a bony part against which a finger can be pressed

Question 30

Describe arterial blood pressure

Answer 30

Measured in mmHg
In ventricular systole the left ventricle pumps blood to the aorta
Pressure increases to approximately 120 mmHg
During relaxation ( diastole ) the pressure doesn’t drop to zero because of the elastic recoil of the arteries
Diastolic pressure approximately 70 mmHg
Expressed as systolic/ diastolic pressure e.g. 120/70 mmHg

Question 31

What are factors determining arterial BP

Answer 31

Depends on amount of blood being pumped out and the resistance to the flow
Mean arterial BP = cardiac output x total peripheral resistance
TPR is resistance of arterioles

Question 32

Describe peripheral resistance

Answer 32

Arterioles can alter their diameter
Contraction of smooth muscle cells in the walls of arterioles causes them to constrict
This increases the resistance to the flow of blood
Makes the pressure on the arterial side higher

Question 33

Describe the control of blood pressure

Answer 33

Short term control of blood pressure via the baroreceptor reflex ( changing HR and SV )
Long term control by hormonal control ( RAAS )
- control blood volume via the kidneys
- peripheral resistance via vasoconstriction

Question 34

Describe change in blood pressure during exercise

Answer 34

Increases demand of O2 and nutrients and produces more CO2 and waste products
This is detected locally and blood vessels dilate locally in muscles to increase blood flow locally
This change which will be picked up by baroreceptors and triggers increased HR and SV to increase CO to fulfil increased demand
Results in increased HR, CO and systolic blood pressure

Question 35

Describe controlling cardiac output to meet demand

Answer 35

The ANS controls cardiac output
At rest output of 70kg is 5 litres per minute
Can increase to around 25 litres per min during intense exercise
Increased activity of the sympathetic nervous system increases release of noradrenaline
Noradrenaline acts on SA node and AV node cells to speed up depolarisation and increases HR
Also increases force of contraction by acting on ventricular myocytes increasing systolic blood pressure