Physiology And Health - Heart Flashcards
What is atherosclerosis?
The accumulation of fatty material consisting mainly of cholesterol, fibrous material and calcium, forming an atheroma or plaque. It is the root cause of various cardiovascular diseases including angina, heart attack, stroke and peripheral vascular disorders.
Where does an atheroma form?
Beneath the endothelium (inner lining) of the artery wall.
What does an atheroma do?
As an atheroma grows, the artery thickens and loses its elasticity. It also reduces the diameter of the lumen of the artery which restricts blood flow, resulting in increase blood pressure.
What happens if an atheroma ruptures?
The damage to the endothelium causes the release of clotting factors. Clotting factors cause the enzyme prothrombin to be converted into its active form, thrombin.
What is thrombin?
Thrombin causes molecules of the soluble plasma protein fibrinogen to form threads if insoluble fibrin protein.
What do fibrin threads do?
Form a mesh work that platelets adhere to, forming a blood clot which seals a wound and provides a scaffold for the formation of scar tissue.
What is thrombosis?
The formation of a blood clot (thrombus) in a vessel.
What happens if a thrombus breaks loose?
It forms an embolus that travels through the bloodstream until it blocks a blood vessel.
What can thrombosis in a coronary artery cause?
A myocardial infarction (MI)
What can thrombosis in an artery in the brain cause?
A stroke
What does thrombosis result in?
The death of some tissue served by the blocked artery as the cells are deprived of oxygen.
What do peripheral vascular disorders cause?
Narrowing of the arteries due to atherosclerosis of arteries other than those of the heart or brain
What can blood clots result in?
Deep vein thrombosis (DVT) and pulmonary embolism.
What is DVT?
The formation of a blood clot in a deep vein most commonly in the lower part of the leg. In DVT pain is experienced in the leg muscles due to a limited supply of oxygen.
How is a pulmonary embolism caused?
By a part of a thrombus breaking free and travelling through the bloodstream to the pulmonary artery where it can cause blockage resulting in chest pain and breathing difficulties.
What is cholesterol?
A component of cell membranes and a precursor for steroid synthesis. Most cholesterol is synthesised by the liver from saturated fats in the diet.
What are lipoproteins?
They contain lipid and protein.
What does High-density lipoprotein (HDL) do?
Transports excess cholesterol from the body cells to the liver for elimination and so prevents the accumulation of cholesterol in the blood.
What does low- density lipoprotein (LDL) do?
Transports cholesterol to body cells.
What are LDL receptors?
Most cells have these and they take LDL into the cell where it releases cholesterol.
Describe how blood circulates?
Blood circulates from the heart through the arteries to the capillaries to the veins and back to the heart.
What happens when blood moves away from the heart?
There is a drop in blood pressure.
What is the central lumen lined by?
The endothelium which is surrounded by layers of tissue.
What do arteries do?
Carry blood away from the heart.
What do arteries consist of?
An outer layer of connective tissue containing elastic fibres and a middle layer containing smooth muscle with more elastic fibres.
What do the arteries do to accommodate the blood surging out the heart?
Stretch and recoil to accommodate the sure of blood after each heart contraction.
What are arterioles?
Small arteries
What can the arterioles do and what does this process allow?
Contract or relax causing vasoconstriction or vasodilation to control blood flow. This process allows changing demands of the body’s tissues to be met.
What happens to the arterioles during strenuous exercise?
The arterioles leading to working muscles vasodilate increasing blood flow and the arterioles leading to abdominal organs vasocontract reducing blood flow.
What are venules?
Small veins
How is blood transported from arterioles to venules?
By passing through a dense network of capillaries.
What do capillaries allow?
The exchange of substances with tissues.
How thick are capillaries?
One cell thick so they allow quick and efficient exchange of materials.
What do veins do?
Carry blood towards the heart
What do veins have?
An outer layer of connective tissue containing elastic fibres. They have a much thinner muscular wall than arteries.
What can we say about the blood pressure in veins?
Blood flows along veins at lower pressure than arteries.
What can we say about the lumen of the vein?
It is wider than that if an artery
What are the function of valves?
They prevent the back flow of blood.
What do coronary arteries do?
Supply oxygenated blood to the heart muscle.
What does the carotid artery do?
Supplies oxygenated blood to the brain
What does the renal artery do?
Supplies oxygenated blood to the kidneys
What does the hepatic artery do?
Supplies oxygenated blood to the liver
What does the jugular vein do?
Carries deoxygenated blood from the brain to the heart.
What does the hepatic vein do?
Carries deoxygenated blood from the liver to the heart.
What does the hepatic portal vein do?
Carries blood from the gut to the liver
What does the renal vein do?
Carries deoxygenated blood from the kidney to the heart.
Where do capillaries occur?
In networks called capillary beds
Why do the capillaries exude plasma?
The high pressure of the arteriole blood causing excess filtration, leading to capillaries exuding plasma
What is plasma?
Liquid component of the blood
What is tissue fluid?
Fluid which bathes cells in tissues, derived from blood
How is blood carried to tissues?
In thick-walled arteries which, once they enter an organ divide into many arterioles which, again divide into capillaries
Explain how food and oxygen diffuse into cells.
- Blood pressure forces the plasma, with smmall soluble molecules, out of the capillaries and intot he tissue fluid leaving behind the blood cells and large plasma protein particles
- The cells exchange molecules with the tissue fluid by diffusion down concentration gradients.
- Useful molecules such as food and oxygen diffuse into cells and carbon dioxide and waste diffuse out.
What is cardiac output?
Volume of blood pumped through ech vetricle (out of the heart) per minute. Measured in litres per minute
What can we say about the volume of blood pumped through the left and right ventricles?
They pump the same amount of blood through the aorta and pulmonary artery
What is the stroke volume?
The volume of blood pumped out of the heart with each heart beat.
What can we say about the pulse rate?
It corresponds with the heart rate
How is cardiac output determined?
Heart rate and stroke volume
How can we work out a persons cardiac output?
CO= HR X SV
How many chambers does the heart have?
4
What does the right side of the heart do?
Collects blood from the body and pumps it to the lungs to collect oxygen
What does the left side of the heart do?
Collects oxygenated blood from the lungs and pumps it to the body
What are the walls of the heart made of ?
Cardiac muscle which can contract rapidly without fatigue for a lifetime
What does the vena cava do?
Returns deoxygenated blood from the body to the heart, filling up the right atruim during atrial diastole.
What is atrial systole? (1st)
When the build up of pressure forces open the AV valve (tricuspid) and blood flows into the right ventricle at which point the atrium contracts forcing all the blood into the ventricles.
What is ventricle systole? (1st)
When the right ventricles muscular walls contract closing the tricuspid and forcing the blood up through the semi-lunar valves and on to the pulmonary artery to the lungs.
What happens during atrial systole?
Oxygenated blood returning from the lungs via the pulmonary vein fills the left atrium
What happened after the AV valve is opened?
Blood flows into the left ventricle at this point the atrium contracts (atrial systole) forcing all the blood into the ventricle.
What happens after the the left ventricles muscular walls contract? (VS)
The bicuspid valve is closed and it forces the blood up through the semi-lunar valves and on through the aorta to the body’s organs.
What causes the heart to make a sound?
The opening and closing of the AV and SL valves.
How is heart beat altered and regulated?
By both nervous and hormonal control.
What are the muscle cells of the heart known as?
Myogenic as they can contract spontaneously.
What is the SAN and what does it do?
The sinoatrial node and is known as the natural pacemaker and is situated in the wall of the right atrium and ensures that both atria contract simultaneous by sending out a wave of excitation (electrical impulses) which are carried through the muscular walls.
What is the AVN and what does it do?
The atrioventricular node receives impulses from the SAN. It is located near the base of the atria, which in turn sends out impulses into a bundle of conducting fibres whoch cause the ventricles to contract simultaneously after the atria .
How does the medulla control heartbeat?
The SAN responds to situations as it is connected to the medulla. The medulla regulates the rate of the SAN through the antagonist action of the ANS.
How can heart rate be increased?
Sympathetic accelerator nerves release noradrenaline (norepinephrine) causing an increase in heart rate. Under certain circumstances such as stress or exercise the SNS causes the adrenal glands to realise adrenaline (epinephrine) causing an increase in heart rate.
How can heart rate be decreased?
Parasympathetic nerves release acetylcholine causing a decrease in heart rate.
What is an ECG?
An electrocardiogram which detect impulses generated by the SAN and the AVN.
Where is blood pressure highest and lowest?
Highest in the aorta and lowest in the vena cava
How is blood pressure generated?
By the contraction of the ventricles and is highest in the large elastic arteries (aorta and pulmonary)
Why does the arterial pressure rise and fall?
As the heart goes through systole and diastole during each cardiac cycle the arterial pressure rises and falls.
What is the blood pressure like during ventricular systole?
At its maximum (120mmHg)
What is the blood pressure like during ventricular systole?
At its minimum (80mmHg)
What is the typical blood pressure reading for a young adult?
120/70mmHg
How is blood pressure measured?
Using a sphygmomanometer.
How does a sphygmomanometer work?
The inflatable cuff stops blood flow and deflates gradually. The blood starts to flow (detected by a pulse) at systolic pressure. The blood flows freely through the artery and a pulse is not detected at diastolic pressure.
What is hypertension?
The prolonged elevation of blood pressure when st rest and is a major risk factor for many diseases later in life such as coronary heart disease s f strokes.
How does negative feedback inhibit the synthesis office new LDL receptors?
Once a cell has has sufficient cholesterol a negative feedback system inhibits the synthesis of nfs LDL receptors and LDL circulates in blood where it may deposit cholesterol in the arteries forming atheromas.
What can a higher ratio of HDL to LDL result in?
Lower blood cholesterol and a reduced chance of atherosclerosis.
What is familial hypercholesterolaemia caused by?
An autosomal dominant gene which results in individuals developing high levels of cholesterol. This results in a decreased number or altered structure of LDL receptors on cell membranes which stops the LDL from unloading its cholesterol into the cell.
How can we tell if an FH gene has been inherited?
Genetic testing
How can FH be treated?
Lifestyle modification and drugs such at statins.
What are peripheral arteries?
Those other than the aorta, coronary and carotid arteries.
What is peripheral vascular disease?
Narrowing of the arteries due to atherosclerosis of arteries other than those of the heart or brain.
What arteries are most commonly affected by peripheral vascular disease and why is pain felt?
Arteries in the legs. Pain is experienced due to limited supply of oxygen.
What is DVT?
Deep vein thrombosis- the formation of s blood clot in the lower path of the leg resulting in swelling and severe pain.
What is a pulmonary embolism?
Caused by part of a thrombus breaking free and travelling via the vena cava and the heart chambers to the pulmonary artery where it can cause a blockage resulting in chest pain and breathing difficulties. If left untreated it can lead to death.
What is cholesterol?
A component of cell membranes and a precursor for steroid (such as sex hormones) synthesis.
What happens to most cholesterol?
It is synthesised by the liver from saturated fats in the diet.
What is glucose?
The substrate for respiration.
What is the rhyme used to remember the roles of glucose and glycogen?
Low blood sugar - glucose gone
What you need is glucagon
To turn glucose into glycogen
What you need is insulin
What are the symptoms of someone with type one diabetes?
- unable to produce insulin
* occurs in childhood
What are the symptoms of someone with type two diabetes?
- occurs mainly in overweight individuals
- develops later in life
- individuals produce insulin but their liver cells are less sensitive to it. Linked to a decrease in the number of insulin receptors in the liver leading to a failure to convert glucose into glycogen.
- can be treated with adjustments to diet and exercise.
What will happen in both cases of diabetes?
Blood glucose levels will rise rapidly after a meal and the kidneys are unable to cope resulting in glucose being lost in the urine.
What is one indicator of diabetes?
Testing urine for glucose.
