MAMMALIAN CIRCULATION Flashcards
What is atrial and ventricular diastole? (4)
-ventricles relax and are ready to receive blood from the atria. as the pressure drops blood flows back from the aorta and pulmonary artery this drop in pressure forces the semi-lunar valves shut.
-as the ventricular pressure drops below that of the atria the atrio-ventricular valves open
-the atria relax elastic recoil of atria walls causes a drop in pressure ‘pulling’ blood into the atria. they fill with blood from the body (via the vena cava and pulmonary vein)
what is the role of myogenic stimulation? (1)
provides a perfectly coordinated rhythm and sequence of activity to ensure maximum efficiency from the cardiac cycle.
what is the role of the SAN? (1)
the cells of SAN depolarise to a point where a wave of excitation similar to a nerve impulse spreads rapidly across the atria causing them to contract simultaneously.
what is atrial fibrillation? (2)
the chaotic rhythm pattern and absence of P waves. 1) atrial kick is lost here, 2)the risk of thrombus formation after 48hr
what is the refractory period? (1)
after every contraction, in the heart this is longer than most other muscles and means that the heart muscles relax to allow refilling and are less likely to suffer fatigue.
what is connected to the AVN? (2)
-bundle of His
-through a weak network of finer branching Burkyne fibres
what does myogenic mean? (1)
myogenic activity originates within muscles rather than through the nervous system.
what is used to measure electric activity in the heart? (2)
by attaching electrodes to the thorax and recording the changing patterns of potential difference. these are displayed as a electrocardiogram (ECG)
where is the SAN located? (1)
in the wall of the right atrium.
what does SAN stand for? (1)
sino-atrial node
what does AVN stand for? (1)
atrio-ventricular node
what does SVT stand for? (1)
supraventricular tachycardia
what does PAC stand for? (1)
pre mature atrial complex
what is sinus exit block? (2)
results from blocked sinus impulses - impulses not getting through to depolarise the atria. tissue around the SA node is not carrying the impulse. Heart rate=48/minute. long pause intervals.
what is NSR with PAC? (3)
results from irritability to the atria resulting in increased automaticity of atrial tissue - since the atria initiate an impulse earlier than expected from the SA node. narrow QRS and flattened, notched or pecked P waves.
what is atria flutter? (2)
results from development of a re-entry circuit within the atria generating a loop that discharges impulses at a flutter rate of 250-350/minute
what is a regular sinus rhythm? (1)
has a rate of 60-100/minute and is the normal adult rhythm
what is SVT? (1)
rates between 170-230/minute, narrow QRS is a regular rapid pattern. not ST is faster.
what is sinus arrythmia? (2)
most often a benign rhythm, irregular pattern fluctuates with inspiration (HR increases) and expiration (HR decreases)
what is sinus tachycardia? (2)
often results from increased sympathetic stimulation (pain, fever etc) heart rate=150/minute
what is sinus arrest? (2)
occurs when the SA node fails to fire. often an escape pacemaker such as the AV junction will assume control of the heart. Heart rate=50/minute
briefly describe the floor of blood in the heart (2)
blood flows from the right side of the heart to the lungs where it is oxygenated and then back to the left side of the heart. from there it is pumped to the rest of the body.
what is an example of mass flow? (1)
internal transport systems.
what is meant by mass flow? (1)
a system of transport that uses a fluid, which is moved by a pressure gradient. substances to be transported are suspended or dissolved in the fluid and all move in one direction.
what is sinus bradycardia? (2)
has rate of around 50/minute regular for athletes but can also be produced by vagal stimulation or due to sick sinus syndrome.
what is double circulation? (1)
blood that passes twice through the heart every single circulation of the body.
what is single circulation? (1)
blood that passes once through the heart every single circulation of the body.
what is the typical cardiac output for a resting adult? (1)
4-4 litres per minute
what is a closed circulation system? (1)
in which blood in enclosed in veins, arteries and capillaries at all times.
what organisms have double circulation? (1)
mammals
what are the chambers of the heart? (4)
-the right atrium
-the right ventricle
-the left atrium
-the left ventricle
what is the function of the coronary arteries? (1)
supply the heart tissue with blood.
what organisms have single circulation? (1)
fish
what are the veins of the heart? (1)
left pulmonary veins
why can fish have a single circulation system? (1)
blood emerging from the gills has only a low pressure and therefore flows around the body much more slowly.
what is ventricular systole? (2)
after a delay both ventricles contract, the pressure increases forcing the atrio-ventricular valves shut and the semi-lunar valves open. blood is forced out to the lungs (via the pulmonary artery) and the body (via the aorta)
what are the arteries of the heart? (2)
-left pulmonary artery
-right pulmonary artery
what are the valves of the heart? (4)
-semi-lunar valves (aortic and pulmonary)
-tricupsid valve
-bucupsid valve
what is the 4th stage of myogenic stimulation? (1)
short relaxation time before SAN node send out a new signal this happens ever 0.8 seconds
what is the 3rd stage of myogenic stimulation? (1)
the impulse will pass up the purkyne fibres causing the ventricle walls to contract from the bottom up, pushinhg blood upwards and out of the ventricles (ventricular systole)
what is the 2nd stage of myogenic stimulation? (2)
the AV node holds the signal and delays it by a fraction of a second to allow ventricles to completely fill with blood. it then passes the signal down the bundle of His to the apex of the heart.
what are the advantages of mammalian blood circulation? (2)
-oxygenated blood is delivered at high pressure to all body tissues
-oxygenated blood reaches the respiring tissues undiluted by deoxygenated blood.
what does the T wave relate to? (1)
diastole
what is atrial systole? (1)
as the atria contract, the blood is pumped through the already open atrio-ventricular valves. blood pours into the relaxing ventricles.
what does the P wave relate to? (1)
relates to atrial systole
what is the heart rate? (1)
the number of times the heart beats per minute
what is the typical stroke volume for a resting adult? (1)
75ml
what does the QRS complex relate to? (1)
relates to ventricular systole
what is the typical heart rate for the resting adult? (1)
70 bpm
what is the 1st stage of myogenic stimulation? (2)
the SA node sends out a wave of depolarisation/electrical impulse which spreads to walls of both atria causing them to contract. this causes atrial systole and blood is pushed down to the ventricles. the impulse does not travel into the ventricle walls at this time due to an insulating layer of fibrous tissue.
what is stroke volume? (1)
the volume of blood pumped up by the left ventricle in each beat
what is cardiac output? (1)
the amount of blood pumped around the body.
how do you calculate cardiac output? (1)
cardiac output = stroke volume x heart rate
what does cardiac output depend on? (2)
stroke volume and heart rate
what are lymph nodes? (1)
Sac like organs that trap pathogens and foreign substances and which contain a large number of white blood cells.
What is lymphatic tissue? (1)
In the spleen, thymus and tonsils, these also contain a large number of white blood cells and are involved in their development.
What is the lymphatic system? (1)
A secondary circulation system and major part of the immune system.
What happens to the excess tissue fluid from tissues? (1)
It drains into the lymphatic system where it forms lymph, the lymphatic system drains into the circulatory system near the vena cava via the thoracic duct.
How is tissue fluid formed? (1)
At the arterial end of a capillary, hydrostatic pressure forces fluid out more than oncotic pressure pulls it back in. At the venous end the forces are reversed.
