lec 22- gas exchange and circulation part 2 Flashcards
what are the two types of circulatory systems?
open and closed
what happens in the open circulatory system?
hemolymph (similar to blood, in insects and invertebrates) is pumped throughout the body in open vessels, can also come in direct contact with tissues resulting in no need for diffusion
what happens in the closed circulatory system
blood flows in a continuous circuit of closed vessels, pumping action is provided by the heart, blood flow can be directed in a precise way to respond to a tissues needs
-(example: blood going to muscles during exercise)
what are the three types of blood vessels and what do they do?
-Arteries: tough, thick vessels that take blood away from the heart under high pressure (small arteries are called arterioles)
-Capillaries: are vessels whose walls are just one cell thick, allowing exchange of gases and other molecules between blood and tissues in networks called capillary beds
-Veins: are thin walled vessels that return blood to the heart (small veins are called venules/ veins dont have much muscle)
what is the aorta and how does it propel blood?
-a large artery that receives blood from the heart, has smooth muscle fibres and elastic muscle fibres
-the elastic fibres in its wall allows it to expand when blood enters at high pressure then propels it forward through elastic recoil
what do the muscle fibres in arterioles do?
-they relax to allow the diameter to increase, reducing resistance and increasing blood flow
-when they contract, they decrease the diameter, increase resistance and slow blood flow down
-This lets blood flow to specific tissues be done with the help of signals from the nervous system
does blood pressure drop as blood passes through arterioles into the capillary beds?
yes
why do veins have thinner walls and larger interior diameters compared to arteries?
because the blood is under relatively low pressure as it exits tissues
what can speed up blood flow in veins?
skeletal activity which compress large veins
what do the one way valves in large veins do?
-prevents backflow of blood
-skeletal muscle contraction and thoracic pressure assist in venous return (contraction closes valves to prevent backflow)
what 2 things cause interstitial fluid build up?
- an outward-directed hydrostatic force in capillaries, created by the pressure on blood created by the heart
- an inward-directed osmotic force in capillaries, created by the higher concentration of solutes in the blood plasma than in the interstitial space
what systems drains out excess fluid from tissues?
lymphatic system, thin wall branching tubules called lymphatic ducts drain the fluid
what is lymph?
interstitial fluid that enters the lymphatic ducts is called lymph
what does the lymphatic system do and what happens if blocked?
-large vessels return excess fluid to the veins entering the heart
-if the vessels are blocked, buildup of fluid and swelling will occur in the tissues
what are the atria of the heart?
they recieve blood returning from circulation (atriums)
what are the ventricles?
they generate force to propel blood out of heart through the circulatory system
what separates the atria from the ventricles?
the atrioventricular valves
what does the pulmonary artery and veins do?
-pulmonary arteries carry blood from the heart to the lungs
-pulmonary veins return freshly oxygenated blood to the heart
what are the two circuits of the circulatory system?
- pulmonary circuit- takes blood to lungs and gills
- systemic circuit- takes blood to the body
how does blood overcome gravity and at what pressures are the two circuits?
-blood overcomes gravity by being pumped at high pressure
-systemic circuit is high pressure and pulmonary circuit is low pressure
how does blood flow through the heart?
-into the heart to body: after blood has circulated through alveoli and becomes oxygenated, it returns to the heart through the pulmonary veins, the oxygenated blood then goes through the left atrium and the atrium contracts, pushing blood into the left ventricle, then the ventricle contracts sending blood at high pressure through the aorta and into the arteries of the systemic circulation
-from body to heart: deoxygenated blood flows from the superior and inferior vena cava, then into the right atrium to the right ventricles, then to the pulmonary arteries in one way due to recoil of blood closing valves
what causes heart murmur?
damaged heart valves
why does blood pressure drop in the capillaries?
the rate of blood flow decreases to allow sufficient time for gases, nutrients and wastes to diffuse between tissues and blood in capillaries
what two pumps help blood in veins to go back to the heart?
skeletal muscle contractions and respiratory pumps (pressure changes in the thoracic cavity during ventilation draw blood back to the heart)
what pressure does the heart have?
negative pressure to help suck blood back in
what conducts the electrical signals in the cardiac muscles of the heart?
cardiomyocytes
how are the electrical signals transmitted between cardiomyocytes?
through gap junctions
what causes the extended plateau phase during action potential generation of cardimyocytes?
slow calcium influx causes complete coordinated contraction of cardiac muscle
can the heart still beat even when the nerves are severed?
yes
what cells in the heart initiate contraction?
pacemaker cells
where are pacemaker cells located?
in the sinoatrial (SA) node
what type of action potentials do the pacemaker cells have?
unsteady action potentials
what are the characteristics of cardiomyocyte unsteady action potentials?
drifting membrane potential due to slow influx of Na+ and quick influx of Ca2+ during depolarization and outflux of K+ during repolarization
what do modified cardiomyocytes do?
direct electrical impulses through the heart on pathways made of them, send impulse down bundle of his then into the purkinje fibers
what are the 5 steps in electrical activation of the heart?
- SA node generates electrical signal
- signal propagates to the atrial muscle cells causing them to contract simultaneously and eject blood into ventricles
- signal is conducted to atrioventricular (AV) node, where there is a delay before passing through ventricles so the atria can completely fill the ventricles before they contract
- After delay, the electrical impulse is rapidly transmitted through specialized fibres in the wall that separate ventricles
-spreads through both ventricles causing contraction as the atria relax
-signal goes from bottom to top of the ventricles causing blood to be ejected into arteries - The final electrical event causes ventricles to relax and cells are restored to initial state
what is systole?
contraction phase of atrium and ventricles
what is diastole?
relaxation phase of atrium and ventricles
what is systolic blood pressure?
blood pressure measured when at the peak of ventricular ejection into the aorta
what is diastolic blood pressure?
blood pressure measured just before ventricular ejection
what makes up the numerator and denominator of blood pressure measurements?
systolic pressure is numerator, diastolic pressure is the denominator
what is hypertension?
when blood pressure is higher than 140/90, leads to circulatory defects like heart attack, kidney failure etc. due to stress on artery walls
what causes lub dub sound in heart?
valves closing and opening
what senses blood pressure in arteries?
baroreceptors
what do baroreceptors do?
when they detect a change in blood pressure, they trigger electrical signals that change the hearts output (output change by changing heart rate and contraction)
can arteries be constricted to serve blood to more vital organs?
yes
can veins shift blood volume towards the heart and arteries to maintain blood pressure and flow to vital organs?
yes
what causes cardiovascular disease and heart attacks?
high fat diets and lack of physical activity leads to buildup of fatty plaques on the walls of arteries increasing pressure and reducing diameter, complete blockage causes myocardial infarction/ heart attacks (portion of the heart tissue dies)
