cardiac system 6.2 Flashcards
Outline the role of elastic and muscle tissue in arteries
Describe the mechanism used to maintain blood flow in arteries between heartbeats
muscle fibres help to form a rigid arterial wall that is capable of withstanding the high blood pressure without rupturing between pumps. can also contract to narrow the lumen.
-> helps to maintain blood pressure throughout the cardiac cycle
The elastic fibres allow the arterial wall to stretch and expand upon the flow of a pulse through the lumen
pressure exerted on the arterial wall is returned to the blood when the artery returns to its normal size (elastic recoil)
elastic recoil helps to push the blood forward through the artery as well as maintain arterial pressure between pump cycles
vasoconstriction (contraction of circular muscles) and vasodilation (relaxation of circular muscles), directly control the flow of blood through the body.
Describe the structure and functions of the three layers of artery wall tissue
Tunica intima
innermost layer, direct contact with blood in the lumen. includes the endothelium that lines the lumen of all vessels; forming a smooth, friction-reducing lining.
Tunica media
middle coat, mainly made up of smooth (involuntary) muscle cells + elastic fibres arranged in roughly spiral layers. layer is usually the thickest of the three layers.
Tunica adventitia
outermost coat, tough layer consisting largely of loosely woven collagen fibres that protect the blood vessel and anchor it to surrounding structures.
Define systolic and diastolic blood pressure
Systolic refers to the part of the heartbeat when the muscle is contracting. 120 and 200 mm Hg.
Diastolic pressure When cardiac muscle is relaxing. Lower pressure than systolic.
Describe the structure and function of capillaries
arteries divide to form smaller arterioles that in turn divide successively to form very fine blood vessels called capillaries. These vessels then fuse together to form venules, and many venules fuse together to form veins.
Capillaries have walls that are only one-cell thick with a diameter of around 3–4 µm; they have no muscle fibres or other layers, are rather leaky.
allows the exchange of materials; oxygen and nutrients with cells in tissues, and waste products, such as carbon dioxide and urea, back into the capillaries to be transported by blood. White blood cells can also exit capillaries through gaps between the endothelial cells.
Describe the cause and effect of diffusion of blood plasma into and out of capillary network
effect: Blood flows slowly at a low pressure through the capillaries to allow for material exchange, which occurs by diffusion or active transport, is greatly enhanced. .
cause:
High hydrostatic pressure at the artery end of the capillary forces material from the blood stream into the tissue fluid.
Lower hydrostatic pressure at the vein end of the capillary allows materials from the tissues to enter the bloodstream.
State the function of veins
Veins transport blood back from the tissues of the body and return it to the atria (upper chambers) of the heart.
Outline the roles of gravity and skeletal muscle pressure in maintaining flow of blood through a vein
Gravity
Veins have very low pressure, which can make it difficult for blood to move against the downward force of gravity.
So, they contain numerous valves to prevent the backflow of blood and maintain circulation.
Skeletal
Veins pass through skeletal muscle groups which use periodic contractions to maintain flow.
When skeletal muscles contract, they squeeze the vein and cause it to flow from the site of compression.
Veins run parallel to arteries and so the same effect can be achieved by the bulging of the arteries created by a pulse.
Outline the structure and function of pocket valve
structure : three cup-shaped flaps of tissue
function : allow blood to only flow in one d irection. Ensure that blood circulates in the body.
Draw a diagram to illustrate the double circulation system in mammals
see notion
Compare the circulation of blood in fish to that of mammals
Humans/mammals have a two circulations of blood (blood is pumped twice). One circulation (systemic circulation) goes from the left ventricle to the rest of the body and back to the right atrium. The second circulation (pulmonary circulation) goes from the right ventricle to the lungs and returns to the left atrium of the heart.
Fish have a single circulation.
Blood is pumped at high pressure to their gills to be oxygenated.
After flowing through the gills the blood still has enough pressure to flow directly, but relatively slowly, to other organs and then back to the heart.
Explain the flow of blood through the pulmonary and systemic circulations.
Pulmonary
To and from the lungs
Recieves deoxygenated blood that has returned from systemic circulation.
Systemic
To and from all other organs, including the heart muscle
Systemic circulation receives blood that has been oxygenated by the pulmonary circulation.
Explain why the mammalian heart must function as a double pump
essential that blood flowing to and from the two circulations is not mixed. The heart is a double pump because it delivers blood under different pressures to separate circulations.
Describe factors that will increase heart rate
Altitude
Exercise
Caffeine
Increased body temperature
Epinephrine hormone
Describe factors that will decrease heart rate
Anticipation of relaxation
Decreased body temperature
Reduced oxygen availability in cardiac cells
Outline conditions that will lead to epinephrine secretion
Epinephrine is produced by the adrenal glands. The secretion of epinephrine is controlled by the brain and rises and increases when vigorous physical activity may be necessary.
