innervating the heart Flashcards
VAGUS HAS AFFERENTS AS WELL AS EFFERENTS.
Yas
if u denervate the heart, will it beat in a faster or slower rate and why?
faster, bc parasympathetic is dominated at rest.
***METABOLITES play a major role in making sure the skelteal muscle amd cornory muscle get adequate perfusion
More important than the act of B2 recepters
BP=COx TPR
Ok
during shock, u wanna give a shot of Adrenaline, why?
to cause vasoconstriction
An asmatic patient came with a problem in heart condition & u adminstered propanol, he developed an asmatic attack, why is this so?
Propanol is non selective B antagonist
Its slowers heart rate and reduces force of comtraction but also acted kn the b2 in the lings and causes bronchocomstriction.
describe sympathetic activity of vessels
symp. activates a1 for vasoconstriction
symapthetic
preganglionic fibres
- innervates SA, AV, Myocardium
- release NE
- acts mainly on B1 adrenocepters
INCREASES heart Rate (chronotropy)
INCREASES FORCE OF contraction (inotrphy)
(B2 & B3 r also in the heart, but main effect is via B1)
Effect of administering atenolol?
Its a SELECTIVE b1»_space; therefore causing less risk of bronchocomstriction
explain what the vasomotor tone is? what allows this arise?
Bv must always remain PARTIALLY contracted in order to maintain a stable arterial pressure!!
via the vasconstrictor area in the vasomotor centre.
We want to examine the eyes of a patient, what do we administer and why?
Atropine» dilates the eyes
Muscuranic antagnoist
What r some drugs that work on the ANS
Sympathomimetics
- a adrenorecepters agonists
- b adrenorecepters agonists
adrenorecepter ANTAGONISTS
Cholinergics
- List the probable physiological effects of giving an individual a drug which antagonises the action of noradrenaline at a- adrenoreceptors.
Arteriolar vasodilation, reduces blood pressure and may cause postural
hypotension
Initial increase in heart rate mediated by baroreceptor reflex Relaxes GI and urinary sphincters
During excersize, what increases BF to the tissues?
The vasodilation of bv via B2 isnt the main reson why we get increased BF, it is mostly through the action of METABOLITES.
The more active the tissue becomes, the more it will release metabolites! (Adenosine, pottasium, H+, Co2) these act on vascular smooth muscle cells to cause relaxation.
What organ is responsible for controlling plasma volume and
how does it do so?
Kidneys, by increased na reabsorbtion
Why are baroreceptors not able to control longer term changes
in blood pressure?
Baroreceptors can re-set to higher levels with persistent increases in blood
pressure
where r baroreceptors located? what do they do?
they r stretch receptor found:
- carotid sinus (dilated region at the bifurcation)
- aortic arch wall
they detect changes in BP
But only short term regulatiom , bc it tends to reset itself after a few days
barorecepters in the carotid sinus send sensory signal via_________ nerve
barorecepters in the aortic arch send sensory signal via_________ nerve
glossopharyngeal
Vagus
TPR=______________
Bp/Co
A patient with an overactive thyroid gland has an increased
response to sympathetic input to the heart. How will the
patient’s heart rate and cardiac output differ from normal?
The patient will have a fast heart rate and increased cardiac output.
When changes in pressure occur, from where r the afferent nerves coming from goint to the brain?
Barorecepters>carotid sinus & carodis body» high pressure
Pressure recepters> atria> low pressure system
how does NA increase force of contraction?
acts on B1 G-s Recepters in myocardium> Adeyly cyclase> increase CAMP > PKA
- phosphorylate Ca+ channels
- increased uptake of Ca in SR (increase Ca store)
- increased sensitivity of contractile machinery to Ca
most vessels receive sympathetic/parasympathetic innervation?
what type?
sympathetic
mostly a1
B2
Effct of prazosin?
A1- antagonist»vasodilaton of bv wil occur
explain what the vasomotor tone is? what allows this arise?
Bv must always remain PARTIALLY contracted in order to maintain a stable arterial pressure!!
***u want there to be a tone so either dilation or constriction can occur.
via the vasconstrictor area in the vasomotor centre.
if we denervate the heart, will it still pump?
yes, electrical activity is activated bc the spontaneous activity of the cell in the ca node.
Some individuals react to bee sting or nettle sting with a
massive release of chemical mediators tending to dilate blood
vessels and constrict the airways of the lung. What substance
would you need to inject into some one suffering this ‘anaphylaxsis’ and why?
Adrenaline
Constriction of resistance arterioles caused by a high concentration of adrenaline acting on α1 receptors increases blood pressure
Relaxes airways of the lung via action on β2 adrenergic receptors
some bv have B2 as well as A1 receptor, describe them and their affinities to circulating adrenaline
a1> vasocontrciotn
B2> vasodilation
But B2 has an higher affinity to normal circulating levels of NA, but if we increase the amount NA, IT will act on the a1
most vessels receive sympathetic/parasympathetic innervation?
sympathetic
mostly a1
(but coronory and skeletal muscle vasculature have B2)
what is BNP?
brain natriutic peptide, ventricular myoctyes release them in response to high tension.
good marker for HF
Parasympathetic control of the heart is via the _______nerve
Vagus 10th cranial nerve
What effect does PKA have on MLCK? Give an examle where this can be seen
It phosphorolates it» therefore inhbits it action»_space; stops comtraction
On B2 adrenocepters on the smooth muscle artery wall., vasoldilation occurs
How do barorwcpeters rwgulate bp? Is this a short term or longterm regulation?
Short term, it detects rise in bp> stretches> signals sent to medulla in the coordinating centre>efferent signals leave and inhibit sympatheic activity to heart and bv
**this is only short term, 7ada bs 1-2 days bs!
A pateint developed an anaphylactic shock, what do we give him?
We 2 shots epipen (epinephrine pen) (the shot bl leg)
A big dose of Adreneline since that will work on A1 recepters on bv and cause vasoconstriction.
what control the levels of sympathetic and parasympathetic outflows?
the cv centre in the medulla oblongata
circulating Adrenaline has a higher affinity to B2 or A1 receptors?
B2, but at higher concentrations it will activate A1 as well.
What do we use for the treamtnet of glaucoma?
Pilocarpine»muscuranic agonist» used in treamtment of glaucoma
** activates constrictor pupillae muscle
What is meant when said that the atrial recepter is a “low pressure system”?
Theyre on the low pressure side of the system (gunna detect the venous pressure) unlike the carotid ones
A patient had a cardiogenic shock, what can we adminster him?
If u wanna act on the heart bs, use a SELECTIVE B1 agonist-dobutamine
The ANS does not initiate electrical activity in the heart
Ok
Describe the parastmpathetic input to heart
Recepter type? Neurotransmitter? How would that effect the heart
postganglionic cells release ACh
• acts on M2-receptors
– decrease heart rate (-ve chronotropic effect)
– decrease AV node conduction velocity
Sympathetic control of the heart is via the …………. nerves
Cardiac
The cardiac output is the product of ……………. and …………………..
………………………..
Sv & HR
The cardiac output is the product of ……………. and …………………..
………………………..
Sv & HR
If you gave an individual an injection of adrenaline (at a dose
higher than the normal circulating levels in exercise) what
cardiorespiratory effects would occur?
T h e r e w o u ld b e a n in c r e a s e in h e a r t r a t e , s t r o k e v o l u m e a n d t h e r e f o r e c a r d i a c o u t p u t T h e a r t e r i o le s t o t h e s k i n w o u l d v a s o c o n s t r ic t ( a c t io n o f a d r e n a l in e o n α 1 r e c e p t o r s ) T h e a ir w a y s w o u ld d i l a t e ( a c t io n o f a d r e n a l i n e o n β 2 receptors)
What does an individual with a high circulating level of adrenaline
look like to an outside observer?
An x i o u s Sw e a t y ( a d r e n e r g ic s w e a t i n g ) Pa l e D i l a t e d p u p i ls
In principle, what sort of drug would you use to limit the
autonomic effects of poisoning with an acetylcholinesterase
inhibitor?
M u s c a r i n ic r e c e p t o r a n t a g o n is t s , e . g . a t r o p in e
most arteries and veins have α1 adrenocepters
– ——–and ———-muscle vasculature also have β2
Coronory and skeletal muscle
Give 2 examples of β-adrenoreceptor antagonists
-propranolol
Non selective b1/b2 antagonist
Slows HR, reduce force of contraction, acts on bronchiol smooth muscle (b2)-brinchocomstriction
-atenolol Selective b1 (selective β1 (cardio-selective) - less risk of bronchoconstriction
