Chapter 15
If you checked the pulse in a persons carotid artery and left wrist at the same time would the pressure waves occur simultaneously?
The carotid wave would arrive slightly ahead of the wrist wave because the distance from heart to carotid artery is shorter.
How much blood do veins hold? Why?
They hold more than half of the blood in the circulatory system. Because they have thinner walls with less elastic tissue than arteries, they can expand easily when they fill with blood.
What control are most systemic arterioles under? What is involved in vasoconstriction? what causes vasodialation?
Tonic sympathetic control causes vasoconstriction. Norepinephrine causes vasoconstriction. Decreased sympathetic stimulation causes vasodilation.
When can venous blood volume be shifted into the arteries.
Venous blood volume can be shifted to the arteries if arterial blood pressure falls.
Hypertension
a significant risk factor for development of cardiovascular disease
Parasympathetic output part of pathway for baroreceptors
an increase in parasympathetic output releases more Ach onto muscarinic receptors, to the SA node, decrease in heart rate, causing decrease in cardiac output, causing decrease in blood pressure
Reactive hyperemia
an increase in tissue blood flow following a period of low perfusion
Atherosclerosis
an inflammatory condition in which fatty deposits called plaques develop in arteries. If plaques are unstable they may block the arteries by triggering blood clots.
Arterioles
are the main site of variable resistance in the systemic circulation. A small change in the radius of an arteriole creates a large change in resistance.
Myogenic autoregulation
arterioles regulate their own blood pressure through myogenic autoregulation. Vasoconstriction increases the resistance offered by an arteriole and decreases the blood flow through the arteriole.
total blood flow at any level of circulation is equal to what?
cardiac output
Cardiovascular function can be modulated by what?
cardiovascular function can be modulated by input from higher brain centers and from the respiratory control center of the medulla.
Continuous capillaries
continuous capillaries have leaky junctions between cells but also transport material using transcytosis. Continuous capillaries with tight junctions form the blood brain barrier.
Sympathetic output part of pathway for baroreceptor reflex
decrease in sympathetic output cuases less NE released onto a receptor and b1 receptors, the - receptor effects the arteriolar smooth muscle causing vasodilation causing decrease in peripheral resistance and decrease in blood pressure. The b-1 receptor effects ventricular myocardium, decreasing force of contraction, causing decrease in cardiac output and decrease in b/p
What transport mechanisms are used by capillary exchange of material between the plasma and interstisial fluid compartments?
diffusion transcytosis and bulk flow
When does the baroreceptor reflex function?
each time a person stands up.
Fenestrated capillaries
fenestrated capillaries have pores that allow large volume of fluid to pass rapidly.
Filtration and absorbtion
fluid movement is called filtration if the direction of flow is out of the capillary and absorption if the flow is directed into the capillary
cardiac contraction creates what?
high pressure in the ventricles which drives blood though the vessels of the systemic and pulmonary circuits speeding up cell to cell communication.
Baroreceptors
in the carotid artery and the aorta monitor arterial blood pressure and trigger the baroreceptor reflex
Mean arterial pressure
is defined as diastolic pressure plus one third systolic pressure minus diastolic pressure
What are blood vessels composed of?
layers of smooth muscle, elastic, and fibrous connective tissue and endothelium.
Resistance to flow is regulated by what?
local and reflex control mechanisms that act on arteriolar smooth muscle and help match tissue perfusion to tissue needs
Lymph flow
lymph capillaries accumulate fluid, interstitial proteins and particulate matter by bulk flow. Lymph flow depends on smooth muscle in vessel walls, one way valves and the skeletal muscle pump.
Homeostatic regulation of the cardiovascular system is aimed at what?
maintaining adequate blood flow to the brain and heart
Vascular smooth muscles function?
maintains a state of muscle tone
What does the homeostatic baroreceptor reflex do?
monitors arterial pressure to ensure adequate perfusion of the brain and heart
Active hyperemia
process in which increased blood flow accompanies increased metabolic activity.
Pulse pressure
pulse pressure equals systolic pressure minus diastolic pressure
Precapillary sphincters
regulate blood flow into individual capillaries
Metarterioles
regulate blood flow through capillaries and allow white blood cells to go directly from aterioles to the venous circulation.
Norepinephrine (role, source, type)
role- baroreceptor reflex, Source- sympathetic neurons, Type- neurotransmitter.
Vasopressin (role, source, type)
role- increase b/p in hemorrhage, source- posterior pituitary, Type- neurohormone
Angiotensin (role, source, type)
role- increase b/p, source- plasma hormone, type- hormone
Adenosine (role, source, type)
role- increase blood flow to match metabolism, source- hypoxic cells, type- paracrine
Epinephrine (b2 receptors) (role, source, type)
role- increase blood flow to skeletal muscle, heart, liver, source- adrenal medulla, type- neurohormone
Hisatmine (role, source, type)
role- increases blood flow, source- mast cells, type- paracrine
Nitric oxide (role, source, type)
role- local control of blood flow, source- endothelium, type- paracrine
Natriuretic peptides (role, source, type)
role- reduce b/p, source- atrial myocardium brain, type- hormone and neurotransmitter.
Korotkoff sounds
sound that Blood squeezing through a compressed brachial artery makes
What is edema? What causes it?
the condition in which excess fluid accumulates in the intertitial space. Factors that disrupt the normal balance between capillary filtration and absorption cause edema.
The flow through individual arterioles affects depends on what?
the flow through individual arterioles depends on their resistance. The higher the resistance in an arteriole, the lower the blood flow in that arteriole.
Cardiovascular disease
the leading cause of death in the united states. Risk factors predict the likelihood that a person will develop cardiovascular disease during her or his lifetime.
Bulk flow
the mass movement of fluid between the blood and the interstitial fluid
colloid osmostic pressure
the osmotic pressure difference between plasma and interstitial fluid due to the presence of plasma proteins
baroreceptor reflex
the primary reflex pathway for homeostatic control of blood pressure
Angiogenesis
the process by which new blood vessels grow and develop especially after birth
Reflex control of blood pressure is where?
the reflex control of blood pressure resides in the medulla oblongata
Explain the role of ventricles and aorta in relation to pressure
the ventricles create high pressure that is the driving force for blood flow. The aorta and arteries act as a pressure reservoir during ventricular relaxation.
would you expect to find valves in the veins leading from the brain to the heart?
veins from the brain do not require valves because the blood flow is aided by gravity.
How is blood pressure measured
with a sphygmomanometer
peripheral resistance
1. The total resistance against which blood must be pumped 2. also known as afterload 3. Major factor effecting perfusion.
At rest what is the desirable systolic pressure and diastolic pressure?
120 mm hg and 80mm hg
How much fluid is filtered out of the capillaries each day? What returns the fluid?
About three liters of fluid filter out of the capillaries each day. The lymphatic system returns this fluid to the circulatory system.
Arterial blood pressure
Arterial blood pressure is indicatve of the driving pressure for blood flow.
What is arteriolar resistance influenced by?
Arteriolar resistance is influenced by local control mechanisms that match tissue blood flow to the metabolic needs of the tissue.
How does blood flow against gravity in the veins?
Blood flow against gravity in the veins is assisted by one-way valves and by the respiratory and skeletal muscle pumps.
Properties of the walls of aorta and the function of these properties?
Both stiff and springy, this allows them to absorb energy and release it through elastic recoil.
What is the site of exchange between blood and interstitial fluid?
Capillaries and postcapillary venules
how does the resistance of arterioles affect blood blow?
Changing the resistance of the arterioles affects mean arterial pressure and alters blood flow through the arteriole.
Orthostatic hypotension
Decrease in blood pressure upon standing
Process of reactive hyperemia (pathway)
Decrease in tissue blood flow due to occlusion, metabolic vasodilators accumulate in ECF, arterioles dilate but occulsion prevents blood flow, remove occlusion, decrease resistance creates an increase in blood flow, as vasodilators wash away arterioles constrict and blood flow returns to normal.
efferent output from the what goes to the heart and arterioles?
Efferent output from the medullary cardiovascular control center
What is a powerful vasoconstrictor?
Endothelins are powerful vasoconstrictors
Chemicals that mediate Vasodilation?
Epinephrine (b2 receptors), nitric oxide, adenosine, histamine, natriuretic peptides
What is the role of epinephrine?
Epinephrine binds to arteriolar a-receptors and causes vasoconstriction. Epinephrine on B2-receptors, found in the arterioles of the heart liver and skeletal muscle causes vasodilation.
How does blood exchange occur?
Exchange of materials between the blood and the interstitial fluid occurs primarily by diffusion.
What is the relationship between blood volume and pressure
If blood volume increases, blood pressure increases. If blood volume decreases, blood pressure decreases.
The formula given for calculating MAP applies to a typical resting heart rate of 60-80 beats/min. If heart rate increases would the contribution of systolic pressure to mean arterial pressure decrease or increase and would MAP decrease or increase?
If heart rate increases, the relative time spent in diastole decreases. In that case, the contribution of systolic pressure to mean arterial pressure increases and MAP increases.
Baroreceptor reflex in response to increase in mean arterial pressure pathway
Increase in blood pressure causes increase in firing of baroreceptors in carotid arteries and aorta onto the sensory neurons.They send message to cardiovascular Control center in medulla oblongata, which activate sympathetic and parasympathetic output.
Process of active hyperemia (pathway)
Increase in tissue metabolism, increase in release of metabolic casodilators into ECF, Arterioles dilate, Decrease resistance creates increase in blood flow, Oxygen and nutrient supply to tissue increases as long as metabolism is increased.
What does increased sympathetic activity do? Increased parasympathetic?
Increased sympathetic activity increases heart rate and force of contraction, in the arterioles causes vasoconstriction. Increased parasympathetic activity slows the heart rate. Parasympathetic has no significant effect of arterioles.
what is arterial pressure a balance of?
It is a balance between cardiac output and the resistance to blood flow offered by the arterioles (peripheral resistance).
Clood pressure is highest where? How does it decrease?
It is highest in arteries and decreases as blood flows through the circulatory system.
Vasodilator paracrines for arterioles
Nitric oxide, Hydrogen ions, Potassium, carbon dioxide, prostaglandins, adenosine, histamine. Low oxygen causes vasodilation.
Chemicals that mediate vasoconstriction?
Norepinephrine (a-receptor), Vasopressin, and angiotensin
Describe Pulse
Pressure created by the ventricles can be felt as pulse in the arteries.