6a: Heart & Blood Vessels Flashcards
What is the Heart Walls made of?
- cardiac muscles
Explain the mammal “Double Circulation”:
There are 2 types of Circulation:
1. pulmonary circulation: right side of the heart sends deoxygenated blood from the body along the pulmonary artery to the lungs
2. systemic circulation: pump on the left side, sends oxygenated blood from the lungs along the aorta to the rest of body
Why is it an Advantage for the Human Heart to have 2 separate pumps, rather than 1?
- the right hand side generates pressure to send blood to the lungs, and pressure drops (e.g for gas exchange in capillaries)
- however, the left side of the heart needs the left ventricle to generate more pressure for the blood to travel around the whole body at a fast enough rate for a high metabolic rate to be generated
What are the “Coronary Arteries”?
- set of arteries that deliver oxygenated blood to the cardiac muscle that makes up the walls of the heart
Why does the Cardiac Muscle need a rich supply of blood?
- for a good supply of O2 + glucose, for high rates of aerobic respiration, to produce lots of ATP for muscle contraction
What does the Septum do?
- separates the left and right chambers of the heart
Where does the Atria receive blood from?
What type of blood passes through the Vena Cava + pulmonary vein?
-veins (right atrium receives from vena cava, and left atrium receives from pulmonary vein)
- deoxygenated for Vena Cava, Oxygenated for Pulmonary Vein
What is the difference in size of Atrium + Ventricles?
What is the difference in size of the left + right ventricles?
- ventricles have much thicker muscular walls
- left ventricle has much thicker muscular walls than the right
Why are the walls of the Left Ventricle thicker than those of the right?
- left ventricle needs to contract with more force and generate a higher pressure, so that it can pump the blood all around the body, rather than just the lungs
What is the function of the Atrioventricular and Semilunar valves?
- prevent backflow of blood
.AV: prevent backflow of blood from ventricles to atrium
.Semilunar: prevent backflow of blood from artery to ventricle
one complete sequence of contraction and relaxation is called a _____ _____
cardiac cycle
Where does blood flow from?
- down a pressure gradient (high pressure to low)
How many times does the heart roughly contract + relax a minute?
70
Explain Diastole:
- heart relaxes during which time the atria again fills up with blood from Vena Cava and Pulmonary Vein
- the atrioventricular valves will be closed at the start of
diastole however, as the blood enters the atria pressure
builds up and forces the valve open to allow blood to start
filling into the ventricles. This is called passive filling.
Explain Atrial Systole:
- blood fills the atria from vena cava and pulmonary vein
- as the atrial muscle contracts, there is an increase in pressure of atria above that of the ventricles
- this forces the atrioventricular valves to open further and more blood flows into the ventricles
Explain Ventricular Systole:
- ventricle muscles contract
- volume of ventricles decrease, pressure therefore increases
- this causes the atrioventricular valves to close, preventing back-flow of blood into the Atria
- blood is pushed upwards towards the arteries at the top of heart
- this forces semilunar valves open, so blood flows into aorta + pulmonary artery
Why are semi-lunar valves closed during diastole?
- pressure is higher in arteries than ventricles, causing valves to close to prevent backflow of blood into ventricles
Why do Atrioventricular Valves close during Ventricular Systole?
- greater pressure in ventricles than atria, so backflow of blood is prevented
Why do semilunar valves open during Ventricular Systole?
- greater pressure in the ventricles than arteries, so blood is pushed upwards forcing the semilunar valves open
Why is the pressure difference much higher for Ventricles, rather than Atrium? (left side of heart)
- left atrium only travels to the left ventricle, so only requires much thinner muscular walls, so weaker contraction occurs, so lower pressure difference
- left ventricle has thicker muscle tissues and stronger muscle contraction, so pressure difference is higher
What would a Cardiac Cycle graph look like if it was the right-side of the heart rather than the left?
- similar shape/profile however much lower pressure changes due to less muscle tissue
The Cardiac Muscle is ______
Myogenic
What does Myogenic mean?
- can contract and relax from itself without the need of nerves
Explain the the Events that Control the Cardiac Cycle:
- A wave of electrical impulse/activity is sent to the Sinoatrial Node (SAN)
- This spreads across both atria, causing atrial contraction
- A band of non-conducting tissue prevents the impulse from passing into the ventricles directly
- The electrical activity/impulse reaches the AV node, where it is delayed
- This delay allows the atria to fully empty, and the ventricles to fill with blood BEFORE they contract
- After this delay, the impulses spread down the ventricles into the Bundle Of His
- The impulse is then transmitted to the base (apex) of ventricles, where it is passed up the Purkyne Fibres
- This causes the ventricles to contact from the base upwards
- Blood is forced up arteries
Cardiac Output Definition:
Stroke Volume Definition:
Cardiac Output Formula:
- total volume pumped out of one ventricle per minute (dm^3 min^-1)
- volume of blood pumped out of one ventricle each contraction
CO = Stroke Volume x Heart Rate
(dm^3 min^-1)
What would happen to the resting heart rate of an athletic person?
How would an athletic person have the same cardiac output as a non-athletic person?
- decreases
- Since the heart rate decreases, the stroke volume increases to provide the same CO:
- this is because the heart gets used to regular exercise, so the larger ventricles can fill with a greater volume of blood as the muscle gets bigger with stronger contraction, so can push more blood out of the heart
Which vessels carries oxygenated + deoxygenated blood to and from the kidney?
- ox: renal artery
- deox: renal vein
What do Arteries branch off to from?
What are small Veins called?
- arterioles
- venules
What speed/pressure do arteries carry blood?
Describe Properties of Arteries:
- high pressure, fast pace
2.
- very thick walls
- inner coat of a single, smooth layer of endothelium
- some muscle tissue, lots of elastic tissue in middle coat
- small lumen
Explain the properties of Arteries:
How do they help Arteries be suited to function?
- thick walls - withstand the extremely high pressure, and fast pace
- smooth layer of endothelium - reduces friction between blood + blood vessel wall
- Elastic Fibres in middle coat:
- elasticity allows them to stretch as the high pressure blood is pumped from the heart, widening arteries reducing pressure a little
- during diastole pressure falls, so elastic recoils keeping the blood under pressure and pushing it along.
this reduces fluctuations in pressure and smoothens blood flow
Why do Arteries closer to the heart have more elastic fibres in their walls than Arteries further from the heart?
- there is greater b.p closer to the heart, so the elastic fibres allow the artery walls to stretch and widen to accommodate surges in pressure
- during diastole pressure drops, so elastic near heart recoils to keep the blood in arteries under some pressure and moving
What are Arterioles?
What is their function?
- arteries reach tissues and branch into smaller vessels called arterioles
- control blood flow the capillaries of different organs
Describe Arteriole properties:
- lots of muscle tissue, some elastic
- single layer of smooth endothelium
- much thinner than arteries
Explain the role of muscle tissue in Arterioles:
- the muscle can contract, narrowing the diameter of the lumen (vasoconstriction)
- this reduces blood flow to the capillaries they serve - the muscle can relax, widening the diameter of the lumen (vasodilation)
- this increases blood flow to the capillaries they serve
During exercise, which arterioles supplying which organs and muscle tissues would be vasoconstricting or vasodilating?
- muscle tissues: these arterioles would vasodilate
- digestive gut: these arterioles would vasoconstrict
What is the advantage of arterioles in the skin dilating when too hot?
- allows lumen to widen, so more blood flowing closer to the surface of skin for heat loss via radiation
Describe Veins properties:
- thin walls
- large lumen
- middle coat contains fewer elastic + muscle fibre
- contains valves
Explain Veins properties:
- thin walls: blood is at a low pressure
- valves: semilunar valves to keep blood flowing in the right direction, open to allow blood to flow to the heart and close to stop it falling back down
How do Veins overcome the problem of low pressure when returning to the heart?
- To keep blood flowing in the right direction, veins contain semi lunar valves. Open to allow blood to flow to the heart and close to stop it falling back down
- many veins run close to several leg muscles, when these contract, they squeeze on veins in legs, which temporarily raises the pressure in them
- Respiratory Pump: when inspiration occurs, pressure in thorax < pressure in atmosphere, so blood travels towards the heart in the thorax
Why are Veins + Arteries organs?
- they contain a number of different tissues working to form a whole and providing a function e.g elastic + muscle tissues
Describe Capillary properties:
- low blood pressure
- thin, consisting of a single layer squamous endothelial cells
- tiny pores
- no elastic/muscle tissure
Explain Capillary properties:
- rate of blood flow reduced to allow more time for gas exchange/diffusion
- red blood cells close to walls reducing diffusion pathway of O2
- single layer of thin endothelial cells reduces diffusion pathway
- tiny pores allow capillaries to be highly permeable - so water and many dissolved substances can be forced out forming tissue fluid
- small size, and the huge network increases SA:Vol
What do capillaries exchange?
- nutrients + dissolved gases with tissue fluid which bathes all the body cells
Explain CHD:
- fatty material (atheroma) builds up in the walls of coronary arteries, which supply the heart muscle with blood.
- this narrows them and reduces the flow of blood through them, resulting in a lack of O2 and glucose for heart muscle cells.
- this atheroma builds up over time, further restricting blood flow, which could lead to blood clots (thrombosis)
- these blocks can build up and eventually completely block the the coronary artery, leading to a heart attack (myocardial infarction), where some heart tissue is damaged and dies
What is a Risk Factor?
- any factor that increases the probability of developing a disease
Which are the unavoidable risk factors?
Inheritance/Genetics: family history of heart disease/high blood cholesterol may lead to early atheroma/CHD
Gender: males are more likely to suffer. Particularly the case in pre-menopausal women as oestrogen protects females from developing atheroma
Increasing Age: the more older, the less elastic and more narrow arteries become
What are 3 lifestyle based risk factors of CHD?
- smoking
- diet
- high blood pressure
Explain how smoking affects CHD?
- contains nicotine: increases heart rate and acts as a vasoconstrictor narrowing artery lumen and increasing b.p
- therefore, increases chance of atheroma and thrombosis
Explain how Diet affects CHD?
High blood Cholesterol: more saturated fat/cholesterol can lead to more LDL cholesterol (deposits in arteries), which increases chance of Atheroma
High levels of Salt: increases blood pressure
How can CHD affects from diet be reduced?
- eat less saturated fats, increase HDL cholesterol as these are taken to liver to be broken down, not taken to arteries
- use statins which reduce blood cholesterol
- stents used to keep arteries open
Explain how high blood pressure causes CHD?
- this can be both genetic or lifestyle
- factors such as prolonged stress, certain diets and lack of exercise increase risk of high blood pressure
- higher the blood pressure more damage to endothelium, which means more atheroma + thrombosis
