6.2 The Blood System Flashcards
who was william Harvey and what did he discover and how
the circulation of blood with the heart acting as a pump
- blood flow through the larger vessels is unidirectional with valves to prevent backflow
- rate of blood flow through major vessels is far too high for blood to be consumed by the body so must be returned to heart and recyceled
- showed that heart pumps blood to the arteries and it returns in veins
- predicted presence of capillaries but couldnot see them
what are arteries
convey blood at high pressure from the ventricles to thje tissues of the body - larger than 10micrometers
pumped from left venticle which is strong muscle and reaches max pressure right after pump at peak of pumping cycle
artery walls control and facillitate blood flow
- elastic tissues contain elastin fibres which store energy from the stretch at the peak of each pumping cycle. recoil helps propel blood down arteries
- contraction of smooth muscle on artery walls determines diameter of lumen and rigdity of artery so blood flow
have to strong so as not tp buldge outwards (aneurysm) or bursting
teh blood progress is pulsatile not continuous
layers of artery walls
TE- tough layer of connective tissue
TM thick layer that has smooth muslce and elastic fibres
TI smooth endotehlium forming
pressure in arteries
the peak pressure in arteries is called the systolic pressure (90-119mmHg)
lowest pressure is called distolic pressure (60-79mmHg)
vasoconstriction and vasodilation is used to increase or decrease blood pressure
arterioles have a particularly high conc of muscle tissue that respond to hormones and neural signals to control blood flow
what are capillaries
have permeable walls that allow exchange of materials between cells in the tissue and the blood in the capilaries
diameter - 10micrometers (phospholipid bilayer is about 8nm long)
NOT to teh tissue in the lens and teh cornea as these must be transparent so cannot contain blood vessels
made of one layer of very thin endothelium cell which have a filter-like protein gell coating with pores between the cells
wall allows parts of the plasma to leak out adn form tissue fluid
tissue fluid has oxygen, glucose adn other substances but not large protein molecules
the fluid flows betweeen cells in the tissue and allws cells to absorb useful substances and exrete waste products
permeability of capillaries various according to location allowing some particular proteins and larger particules to reach certain tissues. Permeabilities can change over time and capillaries repair and remodel themselves in response to the needs of the tissue
what are veins
veins collect blood at low pressure from the tissue of the body and return it to the heart atria - much larger than 10 micrometers
lower pressure blood so no thick walls needed so can dilate and become wider adn hold more blood than arteries around 80% of a sedetary person’s blood is in their veins
blood flow is assisted by gravity and by pressures exerted by skeletal muscles (striated) - squeeze adjacent veins like pumps
vein from arms is subclavian vein
from head is jugular vein
valves prevent backflow - three cup shaped flaps of tissue
- if blood flows back it gets caught in flaps of pocket valve
- when blood flows to heart it pushes the flaps to the side of the vein
makes efficient use of the intermittent and transient pressures provided by muscular and postural changes
what is double circulation and single circulation
fish have single circulation - blood goes from the gills straight to the body
in humans blood capillaries in the lungs cannot withstand high pressures so blood is pumped at low pressure. tehn needs to be at hgih pressure to travel around teh whole body
heart is a double pump - deliveries blood at at different pressures to two seperate circulation systems
draw a digram of the heart
mitral valve - atrioventricualr valves
septum - muscles between ventricles
aortic valve/pulmonary valve - semilunar valve
two entrance points for vena cava
what is atherosclerosis
teh development of fatty tissue called atheroma in the artery wall adjacent to teh endothelium
ldl (low density lipoproteins) containing fats and cholesterol accumulate adn phagocytes are attracted by the signals from tej endothelium cells and smooth muscle
phagocytes engulf the fats and cholesterol by endocytosis and grow very large
smooth muscle cells migrate to form a tough cap pver teh atheroma.
artery wall bludges into lumen and narrows it
can often go unnoticed until a major artery becomes blocked
Coronary occulsion is when this happens to the coronary arteries -
- lack of oxygen (anoxia) causwa pain known as angina and impairs the muscle’s ability to contract so the heart beats faster as it tries to maintain blood circulation with some muscles out of action
- fibrous cap covering atheromas sometimes rupture which stimualtes blood clots which can block arteries and cause acute heart problems
factors which affect atherosclerosis
- high conc of LDL in blood
- chronic high blood glucose conc due to overeating, obesity or diabetes
- chronci high blood pressure due to smoking, stress or other
- consumption of transfats which damage endothelium of arteries
- infection of the artery wals with chlamydia pneumoniae
- production of trymethylamine N oxide (TMAO) by microbes in the intestine
what is epinephrine
increases heart rate to prepare for vigorous physical activity
- sinoartial node responds to epionephrine by increasing heart rate
nickname fight or flight hormone
in past secreted when human were hunting for prey or threatened by predator - now athletes use this in prerace routine to stimualte increased heart rate
what does the sinoatrial node do?
it initiates the heart beat
heart can contract without stimualtion from motor neurones - myogenic it is stimulated from the muscle itself - the membrnae of the heart muscle cells depolarize when the cell contracts and this activates adjacent cells so they also contract
- this occurs almost simultaneously at the fastest rate
the region of cells with the fastest spontaneous beating is the sinoatrial node - cells have few proteins that cause contraction in other muscle but extensive membrane - these membranes are the first to depolarise in each cardiac cycle
- pacemaker can be put in if the node stops working, electronic device that sits under teh skin with electrodced implanted in teh wlal of the heart
how does the sinoatrial node cause contractions
sends out en electrical signal that spreads throughout walls of artia - due to interconnections between adjacent fibres across which the eletrical signal can propagate
fibres are branched so each fibres passes the signal on to several others - less than 1/10 of a second for all cells in the atria to receive the signal - cause the whole of the atria to contract
after a time delay of 0.1 seconds signal is conveyd to ventricles - delay lets blood go to ventricles, signal then propagated through walls of ventricles and causes contraction
how to change the heart rate
impulses are brought to the heart via the medulla (the caridovascular centre) sends out two nerves the accelerator and deccelorator
medulla receives input from receptors that monitor
- low blood pressure low oxygen conc and low pH - more heart rate to deliver more oxygen and remove more co2
- high - heart rate needs to slow down
negative feedback loop
show the changes in pressure in teh LA, LV adn aorta during the cardiac cycle (atrial sytole, ventricular sytole, diastole)
atrial sytole, ventricular sytole, diastole is the order of phases
what are teh phases of diastole and systole
atrial systole -0.15 seconds
- AV valves open
- semilunar closed
- ventricular disatole so no pressure
- atria walls contract
ventricular systole - 0.3 seconds
- atria walls relax - disastole
- semilunar valve opens
- av valve closed
- ventricular walls contract and this pressure caused the valve to open
- heart contracts from apex upwards
diastole - 0.4 seconds
- aorta has greatest pressure
- atria and ventricle relax
- atria slightly more pressure as start to fill
