4.2 The ANS and CVS Flashcards
What is the ANS split into?
The parasympathetic and the sympathetic nervous system
Where does the sympathetic nervous system originate from?
The thoracolumnar area.
Segments T1 to L2
Where does the parasympathetic nervous system originate from?
The craniosacral area
Cranial nerves (III, VII, IX, X)
Sacral nerves S2 to S4
What do all preganglionic neurones release?
Acetylcholine
What do postganglionic parasympathetic neurones release?
Acetylcholine
What do postganglionic sympathetic neurones release?
Noradrenaline
What is a chromaffin cell?
Present in the adrenal medulla
Specialised sympathetic neurone which releases adrenaline
Why are there subtypes of adrenoreceptors?
Allows for diversity or action and selectivity of drug action
When does the sympathetic nervous system tend to act?
Under stress
When does the parasympathetic system tend to act?
Under basal conditions
In what way does the ANS control the CVS?
Controls:
Heart rate
Force of contraction
Peripheral resistance of the blood vessels
Which nerves supplies parasympathetic innervation to the heart?
Where does it synapse?
Vagus nerve
SAN and AVN
How does parasympathetic innervation slow the heart rate?
Acetylcholine reacts with the muscarinic receptors to decrease AV node conduction velocity
How does sympathetic innervation increase the heart rate?
Increases the force of contraction
How does sympathetic activity change the shape of the SA node action potential graph?
The funny current slope gradient is increased so the threshold is reached more quickly.
How is the force of heart contraction increased?
Noradrenaline acts on B1-receptors. This causes an increase in cAMP which activates PKA. Ca2+ channels are phosphorylised causing more Ca2+ to enter the cell during depolarisation. More Ca2+ in the sarcoplasmic reticulum means a greater contraction on depolarisation.
In vasculature what happens with:
i. ) Increased sympathetic output
ii. ) Stable sympathetic output
iii. ) Decreased sympathetic output
i. ) Vasoconstriction
ii. ) Vasomotor tone
iii. ) Vasodilation
What is the job of a baroreceptor and where are they found?
Detects high pressure in vessels
Found in the aortic arch and in the carotid sinus
When is adrenaline given clinically?
Restores function after a cardiac arrest
Given for anaphylactic shock
Name 3 mechanisms the ANS regulates
Heart rate
Blood pressure
Body temperature
