L8- Cholinergic and adrenergic transmission and the ANS Flashcards
What does cholinerigc transmission involve?
Acetylcholine
What is this?
CH3-CO-O-CH2-CH2-N+-3(CH3)
Acetylcholine
It has an ester linkage and a positive permanent charge
What important feature of acetyl choline allows it to bind to its receptors?
Permanent positive charge.
What does the positive charge of acetylcholine mean for it?
Can bind to receptors
Also wont dissolve in the membrane
WHy is the ester linkage important in ACh?
The breakdown of ACh. It’s the point at which the molecule is cleaved to terminate its synaptic action
Which enzyme breaks down acetylcholine?
Acetylcholinesterase
INto acetate and Choline by cleaving the ester bond
What does Ca2+ do at the cholinergic synapse?
Ca2+ stimulates vesicle fusion with the presynaptic membrane. So ACh is exocytosed- out into synapse
What happens to the choline from ACH?
It’s taken back into the nerve terminal via a carrier. Made back into ACh by the enzyme- choline acetyl transferase.
What happens to the ACh when it’s remade?
The acetyl choline made is then transportd into vesicles and stored ready for release
What are the 2 divisions of ACh receptors?
How fast are they?
Muscarinic= slow
Nictotinic=fast
Where are muscarinic and nictontic receptors important?
muscarinic- to effector organis the in the Parasympathetic NS and some SNS.
nictotinic- skeletal neuromuscular junction and autonomic ganglia
Whats the differenc ein structure between noradrenaline and adrenaline?
adrenaline has an extra methyl group on the end.
What type of molecule are noradrenaline and adrenaline?
Catecholamine. They have an amine group and a catechol group
What do sympathetic neurones release at synapses?
Noradrenaline
What does the adrenal medulla sympathetic tissue release?
adrenaline and noradrenaline in a ratio of 4:1
What happens to noradrenaline and adrenalline released from the adrenal medulla?
adrenaline- goes into blood stream, acts as a hormone.
It’s receptors are the same as noradrenaline which goes through the neurones
What are the steps in adrenaline synthesis?
Tyrosine
DOPA
Dopaminne
Noradrenaline
Adrenaline
How is noradrenaline terminated?
NA actions are terminated by uptake (rather than enzymatic cleavage like ACh)
What are the receptors at the ganglion and at the target tissue in the sympathetic and parasympathetic neurones?
- sympathetic- ganglion- nicotinic acetylcholine receptors
target tissue- adrenergic receptors - para- nicotinic acetylcholine receptors
target tissue- muscarinic acetylcholine receptors.
Where is the first cell body and the ganglion between the neurones?
First cell body is in the CNS. The ganglion in sympathetic is by the spinal column, paras. closer tot he target tissue.
Where are ths sympathetic ganglia mostly located?
Close to the spinal cord in a chain. paravertebral ganglia
What’s the adrenal medulla derived from?
Neuronal tissue
Whats the adrenal medullla? What are its cells like? What does it release?
Specialised part of the sympathetic nervous system. Its cells are essentially neurones that have no axons. They release A and NA into circulation where they act as hormones
Where’s the output in parasympathetic nervous system?
The medullary and sacral regiions
What does the vagus nerve do?
Releases acetylcholine to muscarinic receptors at the SAN. This slows heart rate
What happens when atropine is added at the SAN?
Atropine blocks the ACh from the vagus nerve so the SAN fires at its natural rate. Much faster HR.
