Nervous Flashcards
sympathetic nerves are very important in control of what
circulation and heart function
Parasympathetic nervous system plays a role in control of what
only the heart - it has a very minor role in circulation
arterial and venous system are regulated by part of nervous system
sympathetic
sympathetic nerves innervate all vessels except:
microcirculation: capillaries, precapillary sphincters, and metarterioles
when there is sympathetic stimulation blood vessels to what tissues will constrict more than blood vessels to heart or brain
kidneys, gut, spleen, skin
Arterial pressure =
CO x Total peripheral resistance
how do sympathetic increase HR
stimulate heart to increase heart rate and contractility
constrict arterioles to increase total peripheral resistance
contract large veins to decrease compliance
what does sympathetic do to veins
decrease compliance (less blood, so increased CO)
what do beta receptors block
sympathetic control to increase heart rate and contractility directly on the heart
what controls regulation of blood/heart
vasomotor center
what is control fo sympathetic nerves to cardiovasulcar system
vasomotor center
VMC stands for
vasomotor center
important areas of VMC
Vasoconstrictor region
Cardiac region
Sensory Region
vasoconstrictor area transmits signals continously to
sympathetic nerve fibers
where is VMC located
medulla oblongata
how often does vsoconstrictor area fire
constantly
sympathetic tone means there is
tonic activity
sympathetic nerves are constantly firing at
low rate
are sympathetic nerves constantly firing?
yes
sympathetic nerves constantly firing means that blood vessels are always
partially contrcited
what is vasomotor tone
sympathetic nerves constantly firing so blood vessels are always partially constricted
what is importance of vasomotor tone
causes blood pressure in other parts to be higher to push it through tissues
if you fire vasoconstrictor more what happens
vessels constrict more
if you fire less in vasoconstrictore what happens
vessels are more dialted/less constrsicted
where is pressure higher due tot he vasomotor tone controlled by vasoconstrictor area
aorta, lung arteries, small arteries, a little arterioles
if you give someone spinal anesthesia high enought o bloock the VMC, what do you see
blood pressure drop
if you infuse NE into person who has the VMC blocked what happens
blood pressure increases
why is there decrease in BP when you block VMC
blood vessels dilate b/c you can’t get the firing of VMC to cause the vasomotor tone
CA stands for
cardiac accelerator area
CA is what
sympathetic nerves to heart
What does CA do
transmits signals to regulate sympathetic nerves to heart
if CA increases activity what happens
HR increases
What does CI stand for
cardioinhibitory area
where is CI located
dorsal motor nuclei of vagus nerve - where vagus nerve starts
what does CI do
sends parasympathetic impulses to heart through vagus nerve
what cardiac center would increase or decrease blood vessel diameter
VC
what cardiac center would decrease rate/contractility of heart
CI
what cardiac center would increase rate/contracitily of heart
CA
what is transmitted via CA
NE
what is transmitted via CI
Ach
how do we control the cardiac center
there is sensory area located in nucleus tractus solitarius
what does NTS stand for
nucleus tractus solitarius
NTS controls
what happens in cardiac center
how does NTS control cardiac center
baroreceptors that are constantly monitoring blood pressure and it relays it up to NTS and the NTS tells the cardic center what to do
what is reflex control of circulatory function
the baroreceptors talk to NTS which talks to cardiac center which respnods
reflex is
bodies response to initial problem
what are the four negative feedback mechanisms
- Baroreceptor Reflex
- Chemoreceptor reflex
- Atrial and Pulmonary Reflex
- Central Nervous System Ischemic Response
baroreceptors, what are they
stretch receptors
where are baroreceptors located
walls of carotid sinus and aortic arch
baroreceptors are sensory _____
afferents
baroreceptors are ____ afferents
sensory
baroreceptors use ____ to know what pressure is
stretch
baroreceptors terminate where
NTS
vagus nerve is a nerve
trunk
vagus nerve as nerve trunk means
it has afferent to brain and efferent to body
how do baroreceptors communicate to sensory areas
how many impulses they send up
if BP goes from 100 to 160 what do baroreceptors do
the firing rate increases, they send more stimuli to sensory area and that tells brain BP is up
if BP goes from 100 to 80 what do baroreceptors do
the firing rate decreases, less impulses to brain, tells brain BP is lower
rate of firing of baroreceptors tells ____ what is goign on
NTS
ultimately baroreceptors will change what to bring BP to normal
to the cardiac centers, b/c it will talk to NTS which will tell cardiac centers what to do
person hit by car and hemorrhaging, decreased blood volume causes drop in BP, what is first thing that happens
baroreceptors sense drop in BP and firing rate decreases
person hit by car and hemorrhaging, decreased blood volume causes drop in BP, baroreceptors fire less and then what happens
NTS receives signal, then it will tell cardiac centre to increase sympathetic and decrease parasympathetic
so blood vessels and veins constrict, heart increases firing rate and contractility
increaed heart rate, what is medical term
tachycardia
reflex tachycardia
SA node firing faster, result of baroreceptors and NTS
what happens to blood vessels in kidney in response to hemorrhage
they will constrict
what happens to blood vesels in GI tract in response to hemorrhage
constrict
what happens to brain in response to hemorrage
no change - want blood flow to brain to stay the same
what happens to blood vessels in skeletal muscles in response to hemorrhage
constrict a little
what happens to sympathetic nerves is arterial pressure increases
symapthetic nerves decrease
if you decrease sympathetic activity what happens to blood vessels
dilate
if you decrease sympathetic activity what happens to heart
HR falls, contracts a little less strongly
parasympathetic nerves do not innervate
blood vessels
the only thing that controls the blood vessels are
sympathetic
lying position and jump up quickly, you get dizzy , why?
when you are lying flat BP pretty level in body, when you jump up BP in upper part of body falls, so you get dizzy, less blood flow to brain
when you change body posture what are very important
baroreceptors
lying to standing decreases arterial pressure where
head and upper part of body
what is baroreceptor response when person goes from lying to standing position
falling pressure sensed by baroreceptors and increased sympathetic discharge maintains presure
look at graph on pg 17
17
what keeps BP constant during posture chagne
baroreceptors
why do we need to keep BP constant
so tissues get the blood they need
so you don’t pass out/get dizzy
flow =
change in pressure/resistance
role of baroreceptors in long term regulation of arterial presure?
doesn’t change the average BP
they don’t control long term pressure
long term arterial pressure is determined by
kidneys
kidensy determien what blood pressure is, and what keeps it that way
baroreceptors
chemoreceptors where are they located
around arotic baroreceptors and carotid bodies
chemoreceptors monitor changes in
blood levels of things like oxygen, CO2, and hydrogen ions in blood
how do chemoreceptors send sensory afferents
same as baroreceptors - to VMC which then changes sympathetic activity
chemoreceptors only sense what
decrease in pressure
chemoreceptors are not stimulated unless pressure is below
80 mmHg
chemoreceptors are more important in what than in monitoring pressure
respiratory control
what change in O2 will chemoreceptors ense
decrease
what change in CO2 will chemoreceptors sense
increase
what change in pH will chemoreceptors sense
decrease
baroreceptors are ___ pressure sensors
high
what reflex activate the kidney
atrial reflex
if blood volume increases and you stretch the atria, what happens to kidney
sympathetic nerves to kidney, increase in sodium and water excretion to try to lower blood volume
CNS ischemic response is what kind of response
emergency pressure control system
CNS ischemic response is
last ditch effort to kee psomeone alive -
CNS ischemic response is not active untless BP is
below 60 mmHg
CNS Ischemic Response is not from body it is
brain response
CNS Ischemic Response response is activated in response to
creebral ischemia
at some point decrease in blood flow to brain does hat to CO2
causes CO2 to increase in brain
CO2 increase in brain does what
increases talk to vasomotor center, increases sympathetic activity, increase arterial pressure
what is ultimate response of CNS Ischemic Response
sympathetic nerves firing so fast they are closed, so any blood going through heart is going to brain, blood vessels in kidney are closed, blodo vessels in gut are clsoed, you are just getting blood to heart and brain
cushing reaction is what
special type of CNS Ischemic Response
if you increase cerenospinal fluid pressure what will it do
causes arterial pressure to increase to try to open up vessels to get blodo flow there
if you decrease CSF pressure, what happens to arterial pressure
it goes back down
anytime there is atrial stretch, the atrial refelx will increase heart rate by stretchign SA node by stretching atria, and also:
Bainbridge Reflex
what is Bainbridge Reflex
stretchign atria sends afferent to vasomotor center and it only activates heart, doesn’t activate blood vessels
Bainbridge Reflex only activates
heart
Bainbridge Reflex is
stretch of atria causes increase in HR and contractility without affecting blood vessels
why does person who gets shocking news faint?
Vasovagal Syncope reflex gone bad
Vasovagal Syncope (reflex) what is it
emotional stress causes person to faint
list pathway for Vasovagal Syncope
cortex to hypothalamus to medulla, medulla says decrease sympathetic output and increase vagal output ,this decreases total peripheral resistance and decrease venous returna nd cardiac output, thsi decreases arterial pressure and that decreases cerebral blood flow and person loses consciousness
arterial pressure is controlled independently of
local blood flow control & cardiac output control
atrial reflex is what kind of reflex
volume
what are low pressure receptors in atria and pulmonary arteries
atrial reflexes
blood volume changes and what reflex
atrial reflex
increase in blood volume stretch atria and activate low pressure receptors that lower pressure by
working at kidney
activation of atrial reflex does what to kidney
enhances sodium and water excretion
