the heart Flashcards
what is single circulation
blood pressure reduced as blood passes through the gill capillaries. slows down flow to the rest of the body. limits the rate of delivery of O2 and nutrients to cells and removal of waste
efficient for level of activity of fish and don’t need to maintain body temp - respire relatively less than mammals
only goes to the heart once
what is double circulation
heart is composed of two separate pumps
right side pumps blood to the lungs to pick up oxygen left side pumps blood at high pressure to body
necessary because of higher level of activity to maintain body temp
need to deliver and remove materials to and from cells
what is a mammals heart made almost entirely of
cardiac muscle which contracts without resting and doesnt need nerve muscles
what are the four chambers of the heart
right ventricle and right atrium
left ventricle and left atrium
do atria have thin or thick walls and why
thin
don’t need to generate huge force
do ventricles have thin or think walls and why
thick
need a huge force to pump blood around the whole body
what separates the left and right side of the heart
septum
what are the purpose of valves
to prevent backflow
what valve is in-between the left atrium and ventricle
left atrioventricular valve
bicuspid valve
what valve is in between the right atrium and ventricle
right atrioventricular valve
tricuspid valve
what is the valve between the aorta and pulmonary arteries
semi lunar valves
how are valves attached to the cardiac muscle
via tendons
tendinous chordae
what are the major vessels of the heart
coronary vessels pulmonary veins pulmonary arteries aorta artery vena cava
what is the coronary vessel for
responsive for gas/nutrients/waste exchange in the cardiac muscle
what is the pulmonary vein for
one from each lung (oxygenated) converging into left atrium
what is the pulmonary artery for
from the right ventricle to the lungs (deoxygenated)
what is the aorta artery for
left ventricle to body (high pressure)
what is the vena cava for
one from upper body one from lower body to right atrium
in what direction does blood flow in veins
to the heart
in what direction does blood flow in arteries
away from the heart
what is an artery
large vessels which carry blood from the heart
what is an arterioles
small arteries which deliver blood to capillaries
what is a capillary
tiny tubes which deliver/collect blood as close as possible to cells. they link arterioles and venues
what are venules
small veins which collect blood from capillaries
what are veins
carry blood towards the heart
what is structure of blood vessels
- tough outer layer (collagen) to resist pressure
- muscle layer can contract and control the flow of blood
- elastic layer can stretch and recoil to maintain blood pressure
- endothelium smooth layer to prevent friction
- lumen not a layer but a cavity
describe the structure of veins
- wide lumen due to a low pressure in veins
- thins walls, less elastic and less muscular
- valves (semi lunar) to prevent back flow
- deoxygenated blood to heart from tissues
except pulmonary veins from lungs - non pulsatile - smooth flow of blood
describe the structure of arteries
- narrow lumen so high pressure
- highly elastic to expand and recoil
- thick muscular wall to withstand force
- more elastic fibres (recoil)
- no valves (except aortic and pulmonary artery semi lunar at start)
- oxygenated blood from heart
except pulmonary artery to lungs - pulsatile blood flow (expansion and recoil)
- pulse can be felt
describe the structure of capillaries
- no muscle
- no elasticity
- no valves
- only one cell thick
what does endothelium mean
thin layer of cells that lines the interior surface of blood vessels
how does the structure of capillaries help the function
- thin layer of cells for short diffusion pathway
- numerous and highly branched so larger surface area
- narrow diameter to keep all cells close by and slow blood speed
- narrow lumen to bring red blood cells close to the cells so short diffusion distance
- spaces between cells allow white blood cells to escape
describe the structure of arterioles
- smaller than arteries
- thicker muscle layer than arteries to adjust their diameter
- thinner elastic layer than arteries
- no valves
what is systole
period of contraction
what is diastole
period of relaxation
what are the general principles of the cardiac cycle
- contraction of the myocardium generates pressure changes which result in the orderly movement of blood
- blood flows from an area of high to an area of low pressure unless flow is blocked by a valve
- events on the right and left of the heart are the same but pressure on the right is lower
what is atrial systole
the heart is full of blood and the ventricles are relaxed
both the atria contract and blood passes down to the ventricles
the atrio-ventricular valves open due to blood pressure
70% of the blood flows passively down to the ventricles so the atria do not have to contract a great amount
what is ventricular systole
the atria relax. the ventricle walls contract, forcing the blood out. the pressure of the blood forces the atria ventricular valves to shut (producing the heart sound ‘lub’)
the pressure of blood opens the semi lunar valves
blood passes into the aorta and pulmonary arteries
what is diastole
the ventricles relax. pressure in the ventricles falls below that in the arteries. blood under high pressure in the arteries causes the semi lunar valves to shut (this produces the second heart sounds ‘dub’)
during diastole all the muscle in the heart relaxes
blood from the vena cava and pulmonary veins enters the atria and the cycle starts again
what is meant by myogenic stimulation
the heart produces its own electrical impulses for muscle contraction
these originate at the sino atrial node (SA) or pacemaker
what does the SA node do
generates impulses that initiate contraction of the heart muscle
why does there need to be an AV node
it is the only point in which the impulse can pass through the non conducting layer between atria and ventricle
what is the purpose of the branches of His
conducts the impulse to the apex of the heart
what do the Pikenji fibres do
cause the muscle to contract from the base upwards
how does an ECG work
detected by electrodes placed on the body and the reading is known as the electrocardiogram
on an ECG what does p represent
atrial systole
on an ECG what does qrs represent
ventricular systole
on an ECG what does t represent
ventricular diastole
what is bradycardia
resting heart rate is less than 60bpm (e.g. fit athletes, but also due to heart diseases, drugs or hypothermia)
what is tachycardia
heart rate greater than 100bpm (e.g. during exercise but also due to stress, CHD, anaemia)
what is arrhythmia
irregular heart beat
what is ventricular fibrillation
uncoordinated contraction of the heart muscles
the heart ‘quivers’
purpose of red blood cells
contains haemoglobin (formation requires Fe) Hb transports o2 from the lungs to cells
what are erythrocytes
red blood cells
what are phagocytes
white blood cells
function of white blood cells
defence - phagocytosis
contains enzymes which engulf microbes and digests them
what is the purpose of lymphocytes
defence - immune response
produces antibodies and antitoxins
killer cells - destroy cells infected with viruses
what is the purpose of platelets
rupture and release enzymes at site of cut
initiates a cascade of reactions
converts insoluble blood protein FIBRINOGEN into insoluble FIBRIN THREADS which trap blood cells and platelets to form a blood clot
what is blood plasma
the straw coloured liquid (90% water) containing solutes, glucose, amino acids, vitamins, waste (urea), plasma proteins, antibodies. it also distributes heat
adaptations of red blood cells
- biconcave shape maximises surface area for gas exchange
- small and flexible to pass through narrow capillaries
- no nucleus - more room to carry respiratory gases
- packed with haemoglobin
what is haemoglobin made up of
4 globular polypeptides
4 iron ions (prosthetic groups)
haemoglobin is the molecule that allows erythrocytes to carry respiratory gases (especially oxygen)
it has an affinity for oxygen (can carry 4O2molecules)
when haemoglobin becomes oxygenated it is known as oxyhemoglobin
how does oxygen get into haemoglobin
diffuses into blood plasma, it then passes down a concentration gradient and into red blood cells
oxygen binds to haemoglobin to maintain this gradient
oxygen binds to the haem Fe2+ group of haemoglobin
what is cooperative binding
used to describe the fact that as each O2 binds the shape of Hb is changed is changed and it is easier for more O2 to bind
what happens in respiring tissues
oxygen dissociated from oxyhemoglobin
oxygen can then diffuses out of the erythrocytes and to respiring cells
what is the reversible reaction for the bonding of oxygen and haemoglobin
Hb + 4O2 ——> Hb(02)4
why is it hard for the first and last oxygen molecule to bond
- when first oxygen molecules associates the conformation of the haemoglobin changes
- so it is easier for the 2nd and 3rd oxygen molecules to associate
- difficult to associate the 4th oxygen molecule. this is because the haemoglobin molecule becomes full
- this is why the curve plateaus below 100%
why can foetal haemoglobin take in more oxygen
in pregnancy, foetal and maternal blood is kept separate
foetal Hb was a higher oxygen affinity means they can become saturated at a low pO2 (partial pressure)
