lect9: guyton chapter 18 Flashcards
regulation of perpheral blood flow is a dual control of what type
extrinsic, intrinsinc
extrinsic regulationship of peripheral blood flow is controlled primarily by what
nervous system and homrones
intrinsic regulationship of peripheral blood flow is controlled primarily by what
controlled locally in the tissues
controlled by the conditions in the immediate vicinity of the blood vells
extrinsic control is done locally
flase
extrinsic control is.a combo of what to control BP
1) shortt term nerural and hormonal controls
2) long term renal reg.
short term neural and hormonal controls counteract what
Counteract fluctuations in blood pressure by altering peripheral resistance and cardiac output
long term renal regulation conteracts what
counteracts fluctatuion in BP by altering blood volume
which extrinsic conrtol alters blood volume
long term renal
which extrinsic control alterls peripheral resistnace and cardiac output
short term neural and hormonal controls
neural controls regulate via what
via autoonomic nervous system
neural control allows for slow or rapid arteiral pressure control
rapid contol (w/i seconds in response to ext stim)
neural controls maintain MAP by doing what
altering blood vessel diamter
according to neural controls, if there is a low blood volume what happens to the vessels
all vessels constricted except those to heart and brain (because they are essential)
neural controls alter blood distribution to organs in response to what
specific demands
true or false; neural controls act by increasing or decreasing pumping actiivty of the heart
increasing
SNS is is important in control of
ccirculation.
PNS system is important in regulating what
heart function
which nervous system is important for controlling circualtion
SNS
which nervous system is imporant in regulating heart fucntion
PNS
where does the PNS innervation
near SA and VA node (effects HR)
what does the SNS innervation
the heart and blood vessels (increases HR and contractiility)
sympathtietic nerve fibers innervate all vessels except
capillaries and precapilly sphincts and some metarterioles.
eexplain why sphincts are not innervated by sympathetic nerve fibers
they are effected by metabolites, oxygen etc which means itt will constrict or dilate depending on that response
-regulate blood a tlocal level
Innervation of small arteries and arterioles allow sympathetic nerves to BLANK
increase vascular resistance.
leads to vasoconstinction=increase resistnace
large veins and heart are innervated by what
SNS nerves
what are the 3 ways the nervous system can increase arterial pressure within seconds
constricting almost all arterioles of the body which increases total peripheral resistance
constricting large vessels of the circulation thereby increasing venous return and cardiac output
directly increasing cardiac output by raising heart rate and contractility
Rapid (5 – 10 sec) increases in arterial pressure can occur when
during exercise or with fight/flight.
what controls the dilation and contraction (besides sphincs)
the vasomotor center (VMC)
what does the VMC transmit
transmits impulses downward through the cord to almost all blood vessels.
where is the VMC located
VMC is located bilaterally in the reticular substance of the medulla and the lower third of the pons.
the VMC is composed of 3 areas, what are they
The VMC is composed of a vasoconstrictor area, vasodilator area, and sensory area.
true or falose; VMC is the highest center of control of excitatory and inhibition
Many higher centers of the brain such as the hypothalamus can exert powerful excitatory or inhibitory effects on the VMC
what is it called when the Vasoconstrictor area of VMC transmits signals continuously to sympathetic nerve fibers
called sympathetic vasoconstrictor tone.
the signals sent continuously to sympathetic nerve fibers (sympathetic vasoconstrictor tone). main what
These impulses maintain partial state of contraction in blood vessels called vasomotor tone.
true or false, the vessels are always constantly under vasocontstircor tone
true
what do the lateral portions of the VMC control and how
Lateral portions of VMC controls heart activity by increasing heart rate and contractility.
what do the medial portions of the VMC control and how
Medial portion of VMC transmits signals via vagus nerve to heart to decrease heart rate.
The VMC comtrols vessel fucntion (diltate and constrict) by using whtat
neurotramistters
explain how vVMC affects vessel function at the local level
Sympathetic nerve endings release almost exclusively norepinephrine (alpha adrenergic receptors).
=lead to vasocontriction nad decrease bloof fvessel diamter
explain how vVMC affects vessel function at the systemic level
Adrenal medulla secretes epinephrine and norepinephrine which constricts blood vessels via alpha adrenergic receptors.
=slow
true or false the local and systemic levels of VMC affect on vessel formation work in parallel
true
how can epinephrine dialte vessels
Epinephrine can also dilate vessels through a potent Beta2 receptor.
what are some examples of tissues tat use epinephrin for vasodilation
skeletal msucle
what are osme explain of tissues that use epinephrine for vasocontrsction
kidnyes, guts, spleen, skin)
In some tissues (skeletal muscle), epinephrine causes vasodilation through what receptors
beta adrenergic receptors
. In (kidneys, gut, spleen, skin), epinephrine leads to vasoconstriction through what recepots
alpha adrenergic receptors.
true or false: Vasoconstrictor fibers are distributed throughout only cerntain segments of the circulation but with a higher concentration in certain tissues.
false, all over
what reflex is imporant in short term regulation of arterial pressure
arterial baroreceptor relgex
how is the arterial bararecptor initiated
Reflex is initiated by stretch receptors called baroreceptors or pressoreceptors.
explain the arterial barareceptor reflex
A rise in pressure stretches baroreceptors and causes them to transmit signals to the VMC and feedback signals are sent via the autonomic nervous system to the circulation to reduce arterial pressure back to normal.
baroreceprots at the carotid sinus level protect what
perfusion into the brain
baroreceprots at the aortic level protect what
protect the cirulation and heart
explain the relationship between BP and the arteiral baraceptors relfext
if there is an icnrease in BP
the arterial baroreceprors will be stretched and will increase their firing frequency to the VMC
VMC sends signals into crilation
VMC will vasodilate vessels to refuce pressure and reduce heart controactility and heart rate
Carotid sinus baroreceptors respond to pressures between
60 and 180 mmHg.
Baroreceptors respond to changes BLANK
arterial pressuer
where is the barorecptove reflex more sensity
pressure of 100 mmHG
As pressure increases the number of impulses from carotid sinus this results in:
1) inhibition of the vasoconstrictor
2) activation of the vagal center (brings BP beacuse to normal and firinng freq iqll dexreaseO
give an example of the response of the barareceptors to pressure (like protecting brain)
1) constrict common carotids
2) decreae pressure at the carotid sinuses
3) arterial pressure will increase (increase firing frew to VMC, vasoconstriction, increase HR and increase contract)
explain why arterial pressure must increase if the cartoid get clamped
there is a blockage therefore the heart must inrease ipressure to incrase gradient and overcome this icnreases resitance
what is the function of the baroreceptor in term sof posteure
Maintains relatively constant pressure despite changes in body posture.
explain how the barorecptors react when going from supine to standing
1) supine to stranding
2) decreae central blood volume (derase venous return because blood will pool in legs)
3) decrase cardiac output
4) decrease arterial pressure
5) decreae is sensed by barorepceotrs (firing freq will decrease)
6) this wil lstim the VMC which will dilate and do symptathic nervous actitivty to icrease BP
true or false: Baroreceptors ineffective if altered blood pressure sustained
Baroreceptors ineffective if altered blood pressure sustained becayse fhet dapt
what is the main function of the barorecptors.
Opposes either increases or decreases in arterial pressure thereby reducing daily variations in arterial pressure.
true or false: baroreceptors are imporatnt in long term control of arterial prssure
false They are unimportant in long term control of arterial pressure because the baroreceptors adapt.
true or false: chemoreceptor is a short term mechanism
true
true or false: chemoreceptors are the exact same as baros
false, they are similarbut they repsond to chemical chagnes
how can chemoreceptor reflexes incrase BP
Signaling cardioacceleratory center increase CO
Signaling vasomotor center increase vasoconstriction
give an example of chemoreceptor reflex
if there is a change inn the chemicals in the blood (like an icnrase in waste products), the body will icnreas BP to flush away these waste products
Chemoreceptors are chemosensitive cells sensitive to…
lack of O2, excess of CO2 or H+.
where are chemoreceptors located
Chemoreceptors are located in carotid bodies near the carotid bifurcation and on the arch of the aorta.
Activation of chemosensitive receptors results in what
excitation of the vasomotor center. (increase CO, icnrease HR, increae contractility, increase vasoconstriction)
Chemoreceptors are not stimulated until what
pressure falls below 80 mmHg.
know the diagram/grafic on page 20
what is the extreme chemioreceptor
CNS ischemic response
when is CNS ishcmeic repsonse is acvitated in resposne to what
cerebral ischemia (lack of o2 in brain)
explain the CNS ishmic response
Reduced cerebral blood flow causes CO2 buildup which stimulates vasomotor center thereby increasing arterial pressure.
true or falsep CNS Ischemic response is one of the most powerful activators of the sympathetic vasoconstrictor system.
true
explain the connection between cerebral ishmia and arterial pressure
if there is cerebral ischemia (increase co2)
the vasomotor will cause increase in sympathic avicty and then the arterial pressure will icnrase
when is the CNS ischemic response initiated
If blood flow is decreased to the vasomotor center in the lower brainstem and CO2 accumulates,
CNS CNS ischemic response is not activated until pressure falls below
60
when does greatest activattiton of CNS iscmic response occur
at pressure 15-20
tru or falsel CNS ischemic repsonse help faciliate perfusion ot the heart
false, the brain
the CNS is a very strong sympathiec stim which causes what
vasoconsctiction and cardiac accelration
pronlongued CNS ischemia has what effect on the vasomotor center
depressant
know cushin raection
.
what do Low pressure receptors in atria and pulmonary arteries do
minimize arterial pressure changes in response to fluctuations in blood volume.
increases in blood volume activate what
low pressure receptors which in turn lower arterial pressure.
activation of low pressure recprors enhances NA and water extretion by …
Decreasing rate of antidiuretic hormone
- Increasing glomerular filtration rate - Decreasing Na reabsorption
explain the flow of atrial and pulmonary relfexes
1) incrase blood volume
2) increase arterial stretch
3) increase atrial natriuretic peptide and decrease renal sympathetic acvity (blood vessels in kidneys will vasodialte)
4) increase sodium and water excretion
what is the function of the brainbridge reflex
Prevents damming of blood in veins, atria and pulmonary circulation.
how does the bainbridge relfx work
stretch of the atria sends signal to the VMC via vagul afferents to increase HR and contractility
explain the flow of the brainbridge reflex
arterial stretch
send signals to VMC via vagal afferents
VMC will icnrease HR and contractility (ejects more blood=no draining and blood passes through heart more rapidly.
