Cardiovascular System Flashcards
Where is the heart located
On the 5th intercostal space along the mid calcuviar line
Describe the heart
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
Describe the ascending aorta
Carry O2 blood to the rest of the body
Comes out of the left ventricle
Describe the pulmonary trunk
Is an aorta
Going to the lungs coming out of the right side of the heart
Takes deoxygenated blood to the lungs
Describe the superior and inferior vena cava
Bring deoxygenated blood from the body to the right atrium
Describe the pulmonary veins
Bring oxygenated blood back to the left atrium
Describe the aorta
Takes oxygenated blood to the body
Describe the 3 layers
Intima
Media
Adventitia
What is the pericardium
Is the outermost layer and is made up of two sacs
Describe the fibrous pericardium
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
Describe the serous pericardium
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
Describe the myocardium
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
Further describe the myocardium
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
Describe the endocardium
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
Describe the chordae tendineae
Attached valves to muscle to prevent valves turning inside out
Fibrous tendon
Describe the papillary muscles
Contracts to hold onto valves to keep them closed
Describe cardiac myocytes
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
Describe the cardiac cycle
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
Describe the electrical system
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
What is shown at different stages of a ECG deflections
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
Describe the autonomic innervation of the heart
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
What is in circulation
Large arteries, smaller arteries, arterioles, capillaries, venues, smaller veins and large veins
Describe the 3 vessel wall layers
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
Describe gases exchange
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
Describe hydrostatic pressure
Higher the hydrostatic pressure the more the fluid moves out of the capillaries and into the surrounding tissues
Describe osmotic pressure
Osmotic pressure concentration of ions dissolved in the fluid
Across a semipermeable membrane the water will flow from high concentration to low concentration
Describe cardiac output
Is the volume of blood pumped out of the heart in one minute
CO = stroke volume x heart rate
What are factors affecting cardiac output
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
Describe arterial pulse and pulse points
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
Describe arterial blood pressure
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
What are factors determining arterial BP
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
Describe peripheral resistance
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
Describe the control of blood pressure
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
Describe change in blood pressure during exercise
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
Describe controlling cardiac output to meet demand
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
