Test 1- General NS

Question 1

The autonomic nervous system (ANS)

Answer 1

The autonomic nervous system (ANS) is the part of the nervous system that controls visceral functions, below the level of consciousness.

The ANS is divided into the sympathetic “Fight or Flight” and parasympathetic “Rest and Digest”.

Question 2

somatic nervous system

Answer 2

In this it is different from the somatic nervous system which controls voluntary functions (like muscle movement)

Question 3

In general, drugs that act on the autonomic nervous system can be either

Answer 3

In general, drugs that act on the autonomic nervous system can be either ‘mimetics’ which stimulate the system in question (parasympathomimetic, sympathomimetic) or ‘lytics’ which block the system (parasympatholytic, sympatholytic).

Question 4

The parasympathetic nervous system (PSNS) originate

Answer 4

The parasympathetic nervous system (PSNS) originates in the central nervous system at the ‘ends’ of the spinal cord (craniosacral) with neurons originating with the cranial nerves III, VII, IX, and X cranially and originating from the sacral spinal segments (S2-S4) caudally.

Question 5

The sympathetic nervous system (SNS) by contrast arises from

Answer 5

The sympathetic nervous system (SNS) by contrast arises from ‘middle’ section, the thoracolumbar spine

Question 6

Both parts of the ANS consist of an origin in the CNS

Answer 6

Both parts of the ANS consist of an origin in the CNS that sends out an efferent nerve to synapse on an intermediate ganglion which sends a post-ganglionic neuron to the target tissue or organ.

Question 7

In the parasympathetic system

Answer 7

In the parasympathetic system the pre-ganglionic neurons travel a long way before synapsing on their ganglion relatively closer to the target organ or tissue.

Question 8

By contrast, the sympathetic system has

Answer 8

By contrast, the sympathetic system has short pre-ganglionic axons which synapse on the ganglia that form a chain alongside the spinal column and then send out relatively long post-synaptic axons to the end organ.

Question 9

The predominate neurotransmitters at each of these intersections

Answer 9

The predominate neurotransmitters at each of these intersections varies. At the terminal synapses of the sympathetic neurons it is usually norepinephrine (adrenergic). At the terminal synapses of the parasympathetic neurons it is acetylcholine (cholinergic). Additionally all ganglionic synapses utilize acetylcholine, as do the terminal synapses of the somatic nerves (neuromuscular junction).

Question 10

The two major adrenergic (sympathetic) receptors are

Answer 10

The two major adrenergic (sympathetic) receptors are α and β (which have further subdivisons – α-1, α-2, etc).

Question 11

The two major cholinergic (parasympathetic) receptors are

Answer 11

The two major cholinergic (parasympathetic) receptors are Muscarinic and Nicotinic.

Question 12

Nicotinic receptors are found at

Answer 12

Nicotinic receptors are found at all ganglionic and somatic synapses

Question 13

Muscarinic receptors are found

Answer 13

Muscarinic receptors are found on the target tissues of the parasympathetic nervous system (and the less common post-ganglionic cholinergic of the SNS).

Question 14

medullary outflow

Answer 14

The organs innervated by the cranial CNS (medullary outflow) are the eye, lacrimal gland, salivary glands, heart, lungs and upper GI tract.

Question 15

sacral outflow

Answer 15

The caudal CNS (sacral outflow) supplies the lower GI tract, bladder and genitals.

Question 16

exocytosis

Answer 16

When a nerve axon brings an action potential calcium channels open and the increased calcium ion concentration stimulates exocytosis of vesicles containing preformed neurotransmitters (for the PNS that is acetylcholine). The acetylcholine moves into the synapse and interacts with post-synaptic receptors (Nicotinic or Muscarinic).

Question 17

cotransmission

Answer 17

Many neurons apparently respond to more than one neurotransmitter (cotransmission) which may explain why multiple drugs in combination can be particularly effective and why some drugs act on more than one neurotransmitter.

Question 18

Nicotinic receptors

Answer 18

Nicotinic receptors are 5-unit ion channels with multiple subtypes. The significance of the subtypes is that they are different for different locations of nicotinic receptors (e.g. the neuromuscular junction, the ganglionic synapses, etc).

Question 19

Muscarinic receptors come in five flavors:

Answer 19

• M1 – Excitatory – Neural (CNS stimulation, gastric acid secretion, increased GI motility)
• M3 – Excitatory – Glandular (Secretions, smooth muscle contraction, vasodilation)
• M5 – Excitatory – Salivary glands, iris, substantia nigra
• M2 – Inhibitory – Cardiac (cardiac and neural inhibition)
• M4 – Inhibitory – CNS/Smooth muscle

Question 20

Acetylcholine

Answer 20

Acetylcholine has a large number of effects, depending on which receptor it is released at. Drugs will affect these various locations to different degrees, which is very useful clinically.

Question 21

When ACH is released at the ganglia it stimulates

Answer 21

When released at the ganglia it stimulates the post-synaptic neuron to carry on the signal (sometimes this may be an adrenergic ganglion – remember, they use ACh too)

Question 22

When Ach is released at the neuromuscular junction

Answer 22

When released at the neuromuscular junction it stimulates muscle contraction

Question 23

When ACH is released in the CNS

Answer 23

When released in the CNS it can cause convulsions

Question 24

When ACH is released at a parasympathetic terminal synapse

Answer 24

When released at a parasympathetic terminal synapse with the target organ it will facilitate

muscarinic signs:

o Diarrhea

o Urination (smooth muscle contraction in the bladder)

o Miosis
o Bradycardia and Bronchoconstriction
o Emesis (increased GI motility)

o Lacrimation
o Salivation (increased secretions, also in airways)

Question 25

parasympathomimetics.

Answer 25

Drugs that cause the same response ACh would are considered parasympathomimetics. These may be direct or indirect acting. The direct-acting drugs will interact directly with post-synaptic receptors (thus they are muscarinic agonists). Acetylcholine is, of course, the prototype of this.

Question 26

Acetylcholinesterase

Answer 26

Acetylcholinesterase is an enzyme that breaks down acetylcholine and is important in stopping the stimulation of the post-synaptic nerve. They are membrane bound enzymes that bind acetylcholine and break it into choline and acetate which can then be recycled into more acetylcholine. Pseudocholinesterases are enzymes in plasma and other tissues that break down a number of esters.