15 Central Neural Control of the Cardiovascular System Flashcards
What local influences affect the heart?
intrinsic beating (SAN) Starling's Law
What local influences affect the arterioles?
endothelial
myogenic
metabolic
What local influecnes affect the capillaries?
diffusion
filtration
What is the NA?
Nucleus Ambiguus
cell bodies of Vagal supply to the heart
What is the RVLM?
rostral ventral lateral medulla
main site of neurones supplying the descending, sympathetic pathway
How would a spinal transection affect blood pressure?
no sympathetic control of blood vessels
low ABP
What are the sympathetic reflex influences on hormones?
Catecholamines
Vasopressin (ADH)
Renin-Angiotensin
What are the 2 main regions for baroreceptors?
Carotid sinus
Aortic Arch
What are the carotid sinus baroreceptors supplied by?
glossopharyngeal nerve
What are the aortic baroreceptors supplied by?
vagus nerve
What type of receptors are baroreceptors?
stretch receptors
Where do baroreceptor afferents lead to?
Nucleus Tractus Solitarius (NTS)
What is the significance of the threshold to baroreceptor activity?
about 60mmHg
there is baroreceptor activity at resting ABP
When would the baroreceptor response be highest?
at the peak of systole
What are the ultimate aims of the baroreceptor reflex?
to keep ABP lower than it normally would be
What does the sympathetic nervous system do to increase CO?
increases HR
increases Contractility
Increases vasoconstriction
What does the SNS do to increase TPR?
arterial vasoconstriction
How does arterial vasoconstriction increase CO?
decreases capillary hydrostatic pressure
increases EDV
increases SV
How does venoconstriction increase CO?
increases EDV
increases SV
How does the PNS increase CO?
it reduces its’ action, facilitating the increase of HR by the SNS
What do the glossopharyngeal and the vagus nerve do to the NTS in the baroreceptor reflex?
stimulate it
What effect does the NTS have on the NA?
the NTS stimulates the NA
this increases vagal stimulation to the heart
What effect does the NTS have on the RVLM?
it inhibits it (as this facilitates sympathetic drive of the heart)
What effect does the NTS have on the CVLM?
it stimulates it
the CVLM provides inhibitory input to the RVLM
What is the role of the preoptic hypothalamic nucleus in the baroreceptor reflex?
it is quite a long, inhibitory pathway to the RVLM from the NTS
may have a role in telling integrating areas of hypothalamus about the change in ABP
What is the role of the PVN and SON?
these are inhibited in the reflex, reducing the release of ADH
Where is most of the constriction as a response to a fall in ABP?
how does this increase ABP?
GI (25%)
Skeletal muscle (20%)
also in the skin providing we are not thermoregulating
increases TPR
What proportion of our TPR is supplied by the kidneys?
20%
What is the brain’s autoregulatory range?
60-160
What is the effect of cutting the sinus an aortic nerves on ABP on a dog?
Why is this interesting?
ABP becomes far more variable, but still sticks around the mean
this would suggest there is something keeping it in check somewhat…
this is the volume receptor reflex
Where are the stretch receptors of the volume receptor reflex?
what supplies them?
right atrium
supplied by Vagus nerve
What happens to the CNS if there is an increase in blood volume in the volume receptor reflex?
decreased activity to the NTS and PVN
What happens to the kidney if there is an decrease in blood volume in the volume receptor reflex?
increased sympathetic activity:
increases renal vasoconstriction, reducing GFR
increases renin release
increase ADH action
When is the volume receptor reflex used?
decreased distension (when standing, haemmorrhage, dehydration)
increased distension (when supine, large fluid intake)
What is the difference in response time between the baroreceptor and the volume receptor reflex?
baroreceptor reflex is much faster than volume receptor reflex
When might the set point of the baroreceptor reflex change?
acutely - exercise or mental stress
chronically - hypertension, renal failure
