Arteries Flashcards
High compliance of aorta allows the ______ during systole
Stretch
What helps propels blood forward during diastole
Elastic recoil
What allows the aorta and large arteries absorb energy during systole and redeliver a portion of it back to the column of blood
Elastic fibers
What has happened when the systolic pressure rises and capillary flow becomes pulsatile?
Loss of arterial compliance
Atheroscletosis results in the loss of
Compliance of the arteries
Conducted along vessels at a higher velocity than blood flow
Pulse waves
Velocity of conduction increases with _________ stiffness of vessel wall
Increasing
Amplitude of pulse wave is _________ with stiffer walls
Greater
Constriction of small muscular arteries and arterioles to increase TPR and therefore
Blood pressure
Changes in capacitance of veins (constriction) to _____ venous return (preload) to _______ strength of contraction
Increase venous return to increase strength of contraction
Aortic and carotid sinuses:
- _____ nerve endings
- Depolarize in response to
- Modulation of
- Afferent from carotid sinus
- Afferent from aortic sinus
- Synapse to and innervate
- Bare nerve endings
- Depolarize in response to distortion caused by stretch
- Frequency modulated
- Afferent from carotid sinus travel to medulla via CN IX
- Afferent from aortic sinus travel to medullary via CN X
- Synapse with autonomic nerves that innervate the heart and vessels
Baroreceptor signaling between 75 and 125 mmHg what do we see in AP signaling?
AP occur in early systole and then decrease as the receptors adapt
< 75mmHg action potential activity
Drops to low values
> 150 mmHg action potentials are
Continuous
Largest pressure drop is associated with the
Arterioles
Who is primarily responsible for regulating TPR by constriction/relaxation
Arterioles
Arterioles 3 functions
- Reduce the blood pressure to about 30 mmHg at entrance to capillaries (they are very muscular )
- Dampens pressure pulses (constant flow)
- Involved in distribution of blood flow between and within tissues
Allows local control of blood flow w/out involvement of the ANS
Autoregulation
Artificial increase of MAP produces an
Increase in initial blood flow that quickly returns to normal
True or false:
Tissue blood flow remains constant in spite of changes in arterial pressure
True
Myogenic mechanism of autoregulation
Response to increase in arterial pressure is due to the sensing of the stretch of vascular smooth muscles which leads to calcium released and vasoconstriction
Metabolic mechanism of autoregulation
Vasodilator will cause increase blood flow and vasoconstrictors will cause decrease in blood flow
Distribution of blood flow between tissues aided by (3)
What does characteristics allow?
- Muscular walls of arterioles
- Met arterioles
- Precapillary sphincters
- allows for time sharing of blood between capillary beds
Precapillary sphincters can direct blood flow by
Constriction/relaxation
Blood flows down the path of ______ resistance
Least
Capillaries are adapted for
Exchange of fluid and nutrient of solutes with tissues
Pores or fenestrations in capillaries membranes allow passage of but restrict
Allow passage of water and small molecules but normally restrict larger molecules such as proteins
Histamine increases or decreases permeability
Increases thus allowing larger molecules and even leukocytes during inflammation into the extra cellular space
Hydrostatic pressure
Forces fluid out of capillary
Colloid osmotic pressure (oncotic) of proteins within the capillary
Pulls fluid into the capillary
Small excesses of fluids left in the extra cellular space are drained by
Lymphatic
Small solute molecules are exchanged by
Solvent drag
Edema
Excess accumulation of fluid in the tissues
Dehydration
Decrease in extra cellular fluid volume
Causes of edema (3)
- Increased venous pressure which leads to increased capillary hydrostatic pressure
- Decreased blood osmotic pressure—> less osmotic pressure pulling water into the capillaries
- increased interstitial osmotic pressure—> increased interstitial protein concentration acts to pull water out of the capillaries
Veins have a greater or lesser capacity for blood containment than arteries
Greater
Veins have ____ walls:
Thinner walls—> flaccid, less muscular and elastic tissue
Veins are hard to collapse and expand
False: collapse when empty and expand easily
Veins have steady blood flow
True
Veins are subjected to low or high blood pressure
Low
What drives the venous return to the heart
Small pressure drop between capillaries and the vena cava
Are veins complaint?
Yep— highly complaint they are able to store large volumes of blood when CO is low
Sympathetic stimulation in veins
Act on alpha-1 receptors to contract helically arranged smooth muscles to force pooled blood towards the heart
Veins have one-way valves?
Yep
Veins function as variable capacitor that can either store blood or increase venous return the heart and lead to increased _______ and thus resulting in
Increased EDV (preload) and thus increasing CO
In an upright individual where is the most of the body’s blood?
Lower extremities in veins
Factors that increase O2 demand of the heart: (3)
- Increased afterload (arterial pressure)
- Increased stroke volume
3, increased heart rate
The only way to increase O2 delivery is to
Increase coronary circulation
Coronary artery smc are innervate by
Alpha-1 sympathetic nerves which constrict them
Most important autoregulation of coronary artery?
Adenosine—> potent vasodilator that overcomes sympathetic stimulation
Coronary blood flow in left ventricle occurs primarily during
Diastole
Increased heart rate can decrease blood flow to the heart
Yep—> it decreases the diastolic interval
Aortic regurgitation affects
Lowers diastolic pressure thus limits O2 delivery
Lack of O2 delivery to a tissue is called ____ an can lead to
Ischemia which can lead to angina
