Cardiovascular System - Lecture 8 Flashcards
Why are there changes in R, HR and SV?
to maintain flow
What is the idea of the Frank Starling mechanism?
if you stretch a muscle out, it will contract with a greater force
What is the normal value of EDV?
140 mL
What would happen to ventricular filling if EDV increased to 210?
it would increase
What value would SV go up to if EDV was increased to 210?
it would go to 110
What is the Frank Starling Mechanism important in?
exercise
What is preload?
ventricle wall stretch
What are the 2 indices of preload?
EDV and P(RA)
What is the end diastole volume equal to?
preload
What do some critical organs to do maintain flow?
autoregulation
What happens to coronary flow when perfusion pressure decreases?
it decreases
Why does the pressure in the coronary flow increase after 10 seconds when coronary perfusion pressure decreases?
because the resistance drops
If the pressure drops, the flow ___
drops
How does autoregulation maintain flow?
by dilating arterioles
What is the autoregulatory range?
a wide range of pressures (40-160 mmHg) increasing the pressure above or below 120 will result in relatively minor changes to coronary flow
At very low and very high pressures the effect is ___.
lost
What are the two mechanisms responsible for autoregulation?
myogenic mechanism and metabolic mechanism
What is part of the metabolic mechanism autoregulation?
decrease in O2, increase in metabolites
What is part of the myogenic mechanism autoregulation?
decrease in vessel-wall stretch in organ
What are the 5 steps in autoregulation?
- decrease in arterial pressure in organ
- decrease blood flow to organ
- metabolic or myogenic mechanisms
- arteriolar dilation in organ
- restoration of blood flow toward normal in organ
How do the metabolic and myogenic mechanisms operate?
concurrently
What are the 4 steps in autoregulation during exercise?
- increase in metabolic activity of organ
- O2 decreases, increase in metabolites in organ ISF
- arteriolar dilation in organ
- increased blood flow to organ
When is the metabolic mechanism triggered?
during increased activity (increased waste buildup)
What causes local metabolic control?
exercise
Why is it called ‘local’ metabolic control?
because it applies to a specific muscle or organ
What is another name for local metabolic control?
hyperemia
How can you control cardiac output?
by changing heart rate and stroke volume
How can you control mean arterial pressure?
by changing CO, SV and TPR
What does the sympathetic system modulate? (3)
HR, SV and TPR
What does the parasympathetic system modulate? (1)
HR
What happens to plasma epinephrine to increase SA node activity (HR)?
it increases
What happens to the activity of the sympathetic and parasympathetic nerves to the heart to increase SA node activity (HR)?
sympathetic nerves: increase
parasympathetic nerves: decrease
What rhythm controls HR?
sinus node rhythm
What is the sinus node rate modulated by?
sympathetic and parasympathetic innervation
What is the pathway of parasympathetic control of heart rate?
- Preganglionic axon goes to a ganglion (cluster of neurons) –in the cardiac fat pads.
- ACh causes ganglion neurons to fire after binding nicotinic receptors
- This results in ACh release in the sinus node, which binds muscarinic receptors.
Where re preganglionic axons found in the parasympathetic control of HR?
medulla
What causes ganglion neurons to fire after binding nicotinic receptors in the parasympathetic control of heart rate?
acetylcholine
What receptors does acetylcholine bind to when it is released in the sinus node (parasympathetic control of HR)?
muscarinic receptors
What does the parasympathetic control of HR do to neural activity and beat rate?
neural activity: increase
beat rate: decrease
What does atropine do in response to low HR?
binds and blocks the muscarinic receptor
Where are preganglionic neurons found in the sympathetic control of HR?
spinal cord
Where are the ganglia located in the sympathetic system compared to the parasympathetic system?
next to spinal cord (instead of in fat pads)
What does the pre- and postganglionic axons release in the sympathetic control of HR?
preganglionic: ACh
postganglionic: norepinephrine
What does norepinephrine on the sinus node bind to during sympathetic control of HR?
B-adrenergic receptor
What does the sympathetic control of HR do to neural activity and beat rate?
neural activity: increase
beat rate: increase
What is the function of B-antagonists?
prevents binding and lowers HR
What is the function of B-agonists?
binds and increases HR
What neurotransmitter increases stroke volume?
norepinephrine
Does B-agonist increase or decrease stroke volume?
increase
Does B-blocker increase or decrease stroke volume?
decrease
What does B-agonist do to max force, force increase rate and duration of contraction?
max force: +
force increase rate: +
duration of contraction: -
Why do we need to control vessel diameter?
- metabolic local control
- to change MAP
What is the pathway of sympathetic control of vessel tone?
similar to pathway used for HR and SV
What does NE bind to in the sympathetic control of vessel tone?
alpha-adrenergic receptor
Are capillaries surrounded by smooth muscle?
no
Are arteries, arterioles, venules and veins surrounded by smooth muscle?
yes
What do alpha-agonists do to TPR and MAP?
TPR: increase
MAP: increase
What do alpha-blockers do to TPR and MAP?
TPR: decrease
MAP: decrease
Where does the adrenal medulla come from?
cells of the neural crest
Does the adrenal medulla have an associated external ganglion?
no
What parts of the adrenal medulla innervated by?
preganglionic axons that release ACh
What do cells in the adrenal gland synthesize and release?
NE and E
What kind of agonists are NE and E?
beta agonists
What do NE and E affect? (4)
HR, SV, TPR, MAP
Do baroreceptors act quickly or slowly?
quickly
Does the renal system act quickly or slowly?
slowly
What can baroreceptors change? (3)
HR, TPR, SV
What can the renal system control?
total fluid volume
Which is the strongest: baroreceptors or renal?
renal
When do baroreceptors have maximal gain?
at healthy normal BP range (120mmHg)
When does the CNS ischemic reflex work?
when Bp is dangerously low
What is the baroreflex?
fast response to blood pressure changes
Where do baroreceptors come from?
carotid arteries
What do baroreceptors sense?
pressure
What is the pathway of baroreceptors?
- afferent arm
- signal brainstem
- motor arm activated
Where are the 2 locations of the baroreceptors?
aortic arch and carotid sinus
What happens to the aorta and carotid sinus after each heartbeat?
they stretch
What happens to BP when you stand up?
it drops
What happens to sympathetic and parasympathetic tone when you stand up?
sympathetic: increase
parasympathetic: decrease
What 4 things increase when baroreceptor firing decreases?
HR, SV, TPR, venous return
Is an increase in HR by baroreceptors part of sympathetic or parasympathetic control?
both
Is an increase in SV by baroreceptors part of sympathetic or parasympathetic control?
sympathetic
Is an increase in TPR by baroreceptors part of sympathetic or parasympathetic control?
sympathetic
Is an increase in venous return by baroreceptors part of sympathetic or parasympathetic control?
sympathetic
What does the parasympathetic system impact?
HR
What does the sympathetic system impact? (4)
HR
contractility
constriction of veins and arterioles
activation of adrenal glands
