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CH 14 Blood Vessels, Blood Flow, and Blood Pressure
Fichas del conjunto (17)
- 1What is a pressure gradient? Where are pressure gradients present in the vasculature?pressure gradient- difference between the pressures at the two ends of the "pipe" (it is what drives blood flow)
by pumping blood into arteries, the heart increases the mean arterial pressure, which creates a difference in pressure between the arteries and the veins that drives the flow of blood - 2What are some factors that affect resistance in the vasculature? How does resistance affect blood flow?diameter and length of blood vessels
-changes in vessel diameter enable organs to adjust their own blood flow to meet metabolic requirements of the tissue
organization of vascular network (series and parallel arrangements)
physical characteristics (viscosity) of the blood
extravascular mechanical forces acting pon the vasculature - 3Name the 3 types of tissue commonly found in blood vessel walls. Compare the wall thickness of the different blood vessels (in order from thickest to thinnest).endothelium, smooth muscle, connective tissue
artery- thickest wall, muscular, highly elastic
vein- thin wall (compared to arteries), largest diameter, fairly muscular
arteriole- muscular, well-innervated
venule- thin-walled, some smooth muscle
capillary- thinnest wall, highly permeable, just endothelium - 4Define compliance. How does the compliance of arteries contribute to their function as a pressure reservoir?the change in volume of a blood vessel created by the change in the pressure pushing the walls of the vessel outward
low compliance and high elasticity allows arteries to act as pressure reservoirs - 5Define vasodilation and vasoconstriction. How do they affect resistance to blood flow?vasodilation- an increase in blood vessel radius (arteriolar smooth muscle relaxes, the radius of arterioles increases, and resistance decreases)
vasoconstriction- a decrease in blood vessel radius (arteriolar smooth muscle contraction increases, the radius of arterioles decreases, and resistance increases) - 6Explain the different functions of intrinsic and extrinsic controls of arteriole radius.intrinsic controls include a variety of local metabolites that regulate blood flow to match the metabolic needs of the cells in the region
extrinsic controls include both the autonomic nervous system and hormones; these controls regulate MAP - 7Name some intrinsic and extrinsic factors that affect radius.intrinsic:
-active hyperemia: increase in blood flow following an increase in metabolic activity (ex. exercise)
- reactive hyperemia: increase in blood flow in response to a previous reduction in blood flow
-myogenic control: if blood pressure and blood flow to an organ are low then the smooth muscles of adjacent arterioles relax. the resulting vasodilation restores adequate blood flow. if blood flow to an organ is excessive then the smooth muscle of the arterioles will vasoconstrict, thus reducing flow to appropriate levels
extrinsic:
-sympathetic control of arteriolar radius: arterioles are innervated by the sympathetic nervous system only. sympathetic nerve fibers secrete norepinephrine. binding of norepinephrine to receptors on the smooth muscle of arterioles causes contraction and thus leads to vasoconstriction. vasodilation is accomplished by decreasing sympathetic stimulation below baseline level (vascular tone)
-hormonal control of arteriolar resistance: epinephrine (released by adrenal medulla), vasopressin (ADH) (secreted by posterior pituitary), and angiotensin II - 8How do fenestrated capillaries differ from continuous capillaries?fenestrated capillaries- the endothelial cells possess relatively large pores that allow for the rapid diffusion of small water-soluble substances (found primarily in organs whose functions depend on the rapid movement of materials across capillary walls, including the kidneys, intestines, and endocrine glands)
continuous capillaries- most common, the endothelial cells are joined together with tight junctions such that the spaces between them (intercellular clefts) are narrow (highly permeable to water-soluble substances and lipid soluble substances, not to proteins and macromolecules) - 9Of the following changes, which would tend to cause an increase in the rate at which fluid is filtered from capillaries? Choose all that apply: a decrease in plasma osmotic pressure; a decrease in interstitial fluid osmotic pressure; an increase in venous pressure; an increase in plasma protein concentrationa decrease in plasma osmotic pressure
an increase in venous pressure - 10Does an increase in venous pressure tend to increase or decrease cardiac output? Explain.an increase in venous pressure increases cardiac output
increased venous pressure leads to increased venous return which in turn increases end-diastolic volume and thus stroke volume, cardiac output, and ultimately MAP - 11Compare the compliance of arteries and veins, and explain the functional significance of their differences.contraction of smooth muscles in arteries reduces their compliance, thereby decreasing arterial blood volume and increasing arterial blood pressure
relaxation of smooth muscles increase compliance (important in regulation of venous pressure and cardiac preload) - 12What is a baroreceptor? Where are arterial baroreceptors located? Where are low-pressure baroreceptors located? What is the baroreceptor reflex?baroreceptor- a type of sensory receptor neuron in blood vessels and the heart that responds to changes in pressure within the cardiovascular system
arterial baroreceptors are found in the aortic arch and the carotid sinuses of the carotid arteries
low-pressure baroreceptors are found in the right atrium and large systemic veins (volume receptors), which monitor venous pressure
baroreceptor reflex- homeostatic mechanism that helps to maintain blood pressure at nearly constant levels - 13Indicate whether each of the following autonomic nervous activities increases or decreases when arterial pressure falls: sympathetic nervous activity; parasympathetic nervous activity; heart rate; myocardial contractility; vascular resistance (in most tissues); venomotor tonesympathetic nervous activity- increases
parasympathetic nervous activity- decreases
heart rate- increases
myocardial contractility- increases
vascular resistance (in most tissues)- increase
venomotor tone- increase - 14Name 2 organs whose vascular resistance is generally unaffected by baroreceptor reflexes. Why is this beneficial?resistance in the brain and heart are affected very little by sympathetic influences, so they are not altered significantly by the baroreceptor reflex
when a baroreceptor reflex triggers a compensatory rise in MAP, it acts to maintain blood flow to the heart and brain and does so at the expense of other organs (blood shifts away from other organs and towards organs more important for short-term survival) - 15What is respiratory sinus arrhythmia?rhythmic variation in heart rate in which inspiration is accompanied by increases in sympathetic activity and heart rate, whereas expiration is accompanied by increases in parasympathetic activity and a decrease in heart rate
- 16What is a chemoreceptor? Which cardiovascular changes are triggered when chemoreceptors detect a drop in arterial oxygen levels?chemoreceptor- neurons specialized to monitor concentrations of carbon dioxide (and oxygen when it falls to extremely low levels) in the blood
- 17When body temperature rises, does vascular resistance in the skin increase or decrease? How does this change help the body regulate its temperature?decrease
the rate of heat loss through the skin increases which helps counteract the rise in body temperature
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- Bachelors (UNIT 1 RAP) Physiology Fichas sobre CH 14 Blood Vessels, Blood Flow, and Blood Pressure, creado por Katie Ford el 18/01/2016.
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