Cardiovascular system Flashcards
Name the valve between right atrium and right ventricle
Tricuspid valve (AV)
Name the valve between the left atrium and left ventricle
Mitral / bicuspid
Name the two valves between right and left ventricles and the respective veins/arteries
Pulmonary semilunar valve RHS
Aortic semilunar valve LHS
Two types of cardiac myocytes
Contractile (majority)
Autorhythmic (pacemaker)
Describe action potentia in myocardic cells
- Relaxed cells
- Depolarization due to entering of Na ions arrives at threshold
- Na channels close and instead Potassium voltage gated channels open up causing a brief repolarization
- Voltage gated calcium channels open up . They tend to depolarize the cell but the potassium ones are still open so the two ions balance out to give a stable line called plateau.
- Calcium channels close and just potassium channels are open. This results in a depolarization of the cell back to the normal relaxed state in stage 4.
Explain why refractory period in cardiac myocytes is longer than muscles
Because the myocytes need to be fully relaxed before undergoing another contraction otherwise we would have muscle twitches which are a result of summation of contractions
Explain process of propagation of electrical conduction in the heart
- Sinoatrial node depolarizes
- Electrical activity spreads rapidly to Atrioventricular node via the internodal pathways
- Depolarization spreads across the atria leading to their contraction
- Depolarization spreads rapidly through the Bundle of His which branches in two
- Electrical signal finally arrives at Purkinje Fibres which go upwards and surround the ventricles
ECG Waves
- P wave ( depol. of atria)
- QRS comples (depol. of ventricles)
- T wave ( repo. of ventricles)
What is Diastole?
Time during when cardiac muscle relaxes and the chamber fills with blood
What is systole ?
Time during when cardiac muscle contracts and blood is pushed out of the chamber
What is the End Diastolic Volume? (EDV)
Maximum volume of blood left in a ventricle at the end of contraction
What is the End Systolic Volume?
Amount of blood left in the ventricle after contraction
What is the Stroke volume?
Amount of blood pumped by one ventricle during one contraction
What are perycites?
Contractile cells around capillaries
What are capillaries made of?
Endothelium layer one cell thick supported on basal lamina (ECM)
Do capillaries contain muscle?
No
What are precapillary sphincters?
Muscles with a ring-like structure that surround metaarterioles and control if blood has to go into capillary bed (open) or go straight to venous circulation(closed)
What are metarterioles?
Branches of arterioles
What 3 forces help venous return?
- Muscoloskeletal pump
- Respiratory pump (inspiration)
- Constriction of veins by sympathetic activity
Formula for Mean Arterial Pressure
diastolic pressure + 1/3 (systolic- diastolic)
What part of the brain controls blood pressure?
The CardioVascular Control Centre (CVCC) in Medulla oblongata
What are baroreceptors and where are they located
Baroreceptors are stretch receptors located in the walls of carotid arteries and aorta. They continously trigger action potentials and when pressure changes, they increase or decrease the frequency. Response within two heartbeats.
What does atherosclerosis lead to ?
- Ischaemic heart disease
- Angina pectoris
- Myocardial infarction
- Stroke
What type of cholesterol causes atherosclerosis?
LDL (low density lipoprotein) because cells in the endothelium of arteries have receptors for it so they can intake it. Whereas they don’t have receptors for HDL so it doesn’t accumulate in arteries.
Phases of atherosclerosis
- NORMAL ARTERIAL WALL
- FATTY STREAK ( LDL accumulates in ecs between endothelium and connective tissue. Eaten up by macrophages which become lipid filled foam cells. Cytokines from macrophages make smooth muscle cells migrate to lipid deposit.
- STABLE FIBROUS PLAQUE : Fibrous scar tissue forms to wall the lipid core. Muscle cells thicken the arterial wall. Dying muscle cells become calcified
- VULNERABLE PLAQUE: enzymes released by macrophages make the fibrous wall more thin till it eventually ruptures exposing collagen to platelets and giving rise to blood clot.
What is Angina Pectoris?
Blood clot that block blood flow in the arteries. Cells switch to anaerobic metabolism which creates lactic acid that leads to chest pain.
Congestive heart failure
When one half of the heart works more than the other so the other tries to compensate. Congestive because of accumulation of liquid in the lungs (pulmonary edema) because capillary filtration exceeds the capacity of the lymph system to drain liquids out of the lungs.
What causes Mitral stenosis and what is it?
- Rheumatic fever
- Mitral valve becomes calcified and thickened: blood leaks from left atrium to left ventricle. Left ventricle pressure increases and so hypertension in lungs: left ventricle increases to compensate for lungs hypertension
