Drugs acting on the parasymapathetic and somatic nervous systems

Question 1

how do stimulations travel from the CNS to the effector in the ANS

Answer 1

travels from the CNS as part of cranial or spinal nerve to the ganglia
Then travels along post ganglionic neurons to C- fibre synapses on the visceral effector

Question 2

what type of outflow is the para sympathetoc nervous system

Answer 2

Craniosacral

Question 3

what type of pre and post ganglionic fibres does it have (long or short)

Answer 3

pre long , post short

Question 4

what nerve carries many parasympathetic fibres

Answer 4

the vagus nerve

Question 5

how any post ganglionic neurons do the post ganglionic fibres synapse to

Answer 5

4-5

Question 6

what is pseudo colouring

Answer 6

adding colour to imaging techniques after the black and white version is obtained

Question 7

what is dual innervation

Answer 7

when an organ has both parasympathetic and sympathetic innervation - controlled by both

Question 8

can the 2 divisions of the ANS work together, give an example

Answer 8

• the parasympathetic promotes erection
• the sympathetic produces ejaculation

Question 9

what is the role of the parasympathetic nervous system

Answer 9

rest & digest / feed & breed

Question 10

what is the PSNS outflow

Answer 10

cranial and sacral

Question 11

is the PSNS’s ganglia close or far from the effector

Answer 11

close

Question 12

what is the neurotransmitter at the ganglia in the PSNS

Answer 12

ACh

Question 13

what types of receptors are found at the ganglia

Answer 13

nicotinic

Question 14

what type of receptors are found at the effector in the PSNS

Answer 14

nuscarinic

Question 15

what is Muscarine

Answer 15

an Alkaloid
isolated from Amanita
muscaria (Fly Agaric)

Question 16

what is the role of muscarine

Answer 16

to
selectively stimulate the
receptors present at
parasympathetic nerve
terminals

Question 17

what type of channel links nicotinic receptors

Answer 17

ion linked

Question 18

what type of channel is muscarinic receptors linked to

Answer 18

G protein

Question 19

why are there different types of muscarinic receptors

Answer 19

have different couplings
and different tissue distributions – provides range
of pharmacological targets:

Question 20

where do we find these different types of mAChR? (muscarinic ACh receptors )

Answer 20

M1 (‘neural’) Brain, stomach
* M2 (‘cardiac’) Heart
* M3 (‘smooth muscle’) Eye, GI
tract, bladder, lung

Question 21

Types and
examples of
muscarinic
agonists

Answer 21

Choline esters
- acetyl choline
- methacholine

Alkaloids
-muscarine
- pilocarpine

Question 22

Why not use Acetylcholine
itself as a drug?

Answer 22

it gets broken down quickly by
acetylcholinesterase so has Short-lived effects
So it is not used therapeutically

Question 23

what are choline esters

Answer 23

Range of compounds structurally
similar to acetylcholine
Varying levels of action at
muscarinic receptors, nicotinic
receptors
Different levels of susceptibility to
cholinesterase, so differing
durations of action

Question 24

Clinical uses of muscarinic agonists?

Answer 24

pilocarpine is used in the treatment of glaucoma
- bethanechol to stimulate the emptying of the bladder

Question 25

why is pilocarpine used to treat glaucoma

Answer 25

Lipid soluble - penetrates cornea

Question 26

what is glaucoma

Answer 26

Raised intraocular pressure
* Due to reduced drainage of aqueous humour
* Folding of the iris tissue blocks drainage when the iris is
dilated
* Can result in damage to optic nerve
* Impairment ranges from loss of peripheral vision to
blindness

Question 27

what are the symptoms of glaucoma

Answer 27

early cupping of the occular disk
- vision shrinks

Question 28

how does pilocarpine treat glaucoma

Answer 28

it contracts the constrictor pupillae muscle
- this then constricts the pupil and restores drainage

Question 29

How are muscarinic antagonists used clinically?

Answer 29

treatment of brady chardia (slow heart rate)
- during general anesthesia - to block vagal slowing of the heart and inhibit bronchial secretion

Question 30

But Muscarinic Antagonists exhibit side-effects because muscarinic receptors mediate other effects such as

Answer 30

• Dry mouth
• Constipation
• Urinary retention
• Sedation
• High doses -> restlessness, agitation,
  disorientation
• Tachycardia (mild- 80-90 bpm)

Question 31

what is used instead of Non-selective Muscarinic Antagonists to prevent other areas being effected

Answer 31

Subtype-selective Muscarinic Antagonists
Newer muscarinic antagonists have been
developed that are more selective for one
particular subtype (‘subtype selective’).
However, none are completely free from side
effects due to some action at the other subtypes

Question 32

whats an example of a subtype selective muscarinic antagonist

Answer 32

pirenzepine which selectively blocks M1 receptors involved in gastric acid secretion
its also used as an anti ulcer agent

Question 33

what is the role of the somatic nervous system

Answer 33

consciously controlled

Question 34

what is the function of the SNS

Answer 34

Control of skeletal muscle nerve
stimulation => muscle contraction

Question 35

what is the structure of the SNS

Answer 35

Structure: Single neurone - no ganglia

Question 36

what neurotransmitter is used in the SNS

Answer 36

Neurotransmitter: Ach

Question 37

what type of receptor is present at the effector

Answer 37

Nicotinic (Neuromuscular)

Question 38

how does a NMJ work

Answer 38

Cholinergic neuron
* AChdepolarises
muscle fibre
(excitation
contraction
coupling)
* AChbroken down
by
acetylcholinesterase

Question 39

how is ACh produced and broken down

Answer 39

The synthesis of acetylcholine
from choline and acetyl CoA
requires choline acetyltransferase.
Acetyl CoA is derived from
pyruvate generated by glycolysis,
while choline is transported into
the terminals via a Na+-dependent
transporter. After release,
acetylcholine is rapidly
metabolized by
acetylcholinesterase and choline
is transported back into the
terminal