4 - Neurotransmitters

Question 1

What are the major classes of neurotransmitters? (5 classes)

Answer 1

1. acetylcholine
2. amino acids
3. biogenic amines
4. neuropeptides
5. gases

Question 2

What neurotransmitter(s) are in the acetylcholine class?

Answer 2

Acetylcholine

Question 3

What neurotransmitter(s) are in the amino acid class

Answer 3

1. glutamate
2. GABA
3. glycine

Question 4

What neurotransmitter(s) are in the biogenic amine class?

Answer 4

1. norepinephrine
2. dopamine
3. serotonin

Question 5

What neurotransmitter(s) are in the neuropeptide class?

Answer 5

1. substance P
2. met-enkephalin (an endorphin)

Question 6

What neurotransmitter(s) are in the gas class?

Answer 6

Nitric oxide

Question 7

Function (1) and examples of malfunctions (2) of acetylcholine

Answer 7

1. enables muscle action, learning, and memory
2. undersupply, as Ach-producing neurone deteriorate, marks Alzheimer’s disease

Question 8

Function (1) and examples of malfunctions (2) of dopamine

Answer 8

1. influences movement, learning, attention, and emotion
2. excess dopamine receptor activity linked to schizophrenia; starved of dopamine, the brain produced the tremors and decreased mobility of Parkinson’s disease

Question 9

Function (1) and examples of malfunctions (2) of serotonin

Answer 9

1. affects mood, hunger, sleep. and arousal
2. undersupply linked to depression; Prozac and some other antidepressant drugs raise serotonin levels

Question 10

Function (1) and examples of malfunctions (2) of norepinephrine

Answer 10

1. helps control alertness and arousal
2. undersupply can depress mood

Question 11

Function (1) and examples of malfunctions (2) of GABA (gamma-aminobutyric acid)

Answer 11

1. a major inhibitory neurotransmitter
2. undersupply linked to seizures, tremors, and insomnia

Question 12

Function (1) and examples of malfunctions (2) of glutamate

Answer 12

1. a major excitatory neurotransmitter; involved in memory
2. oversupply can overstimulate brain, producing migraines or seizures (which is why some people avoid MSG, monosodium glutamate)

Question 13

What are the two major classes of acetylcholine receptor?

Answer 13

Vertebrates have two major classes of acetylcholine receptor, one that is ligand gated and one that is metabolic

Question 14

Somatic efferent system pathway(s)

Answer 14

CNS -> ACh (nic) activates skeletal muscle

Question 15

Sympathetic system pathway(s)

Answer 15

CNS -> ACh (nic) -> NA activates blood vessels
CNS -> ACh (nic) -> ACh (mus) activates sweat glands
CNS -> ACh (nic) activates adrenal medulla

Question 16

Parasympathetic system pathway(s)

Answer 16

CNS -> ACh (nic) -> ACh (mus) activates salivary glands

Question 17

What are neuromuscular synapses?

Answer 17

Nerves descending from the spinal column are attached to skeletal muscle and form synapses

Question 18

What does noradrenaline do?

Answer 18

• activates blood vessels causing dilation
• the contraction of certain blood vessels at the skin surface to limit unnecessary blood vessels at the skin surface (want to direct blood away from skin to the muscles)

Question 19

How is the gut involved in the sympathetic nervous system?

Answer 19

• constriction of the blood vessels to the gut
• this switches of digestion and opens up blood vessels to the heart

Question 20

How are the liver and lungs involved in the sympathetic nervous system?

Answer 20

• production and release of glucose from the liver to feed the muscles
• dilation of the bronchioles so we get oxygen entering the lungs
• this is to oxygenate the blood for flight or flight

Question 21

Function of the nicotinic acetylcholine receptor

Answer 21

Depolarise the post-synaptic muscle membrane upon release of ACh permeable to: Na+ (in) and K+ (out)

Question 22

Structure of the muscle nAChR (4 points)

Answer 22

1. the five receptor subunits form a cluster surrounding a central transmembrane pore, the lining of which is formed by the M2 helical segments of each subunit
2. these contain a preponderance of negatively charged amino acids, which makes he pore cation selective
3. there are two ACh binding sites in the extracellular portion of the receptor, at the interface between the alpha and the adjoining subunits
4. when ACh binds, the kinked alpha-helices either straighten out or swing out of the way, opening the channel pore

Question 23

What forms the ligand binding site for ACh?

Answer 23

multiple subunits- alpha-delta and alpha-gamma subunits

Question 24

What is tubocurarine?

Answer 24

• competitive reversible antagonist of ACh at nicotinic receptors on skeletal muscle cells
• used to relax skeletal muscle in surgery
• actions are reversed by increasing ACh concentration by inhibiting the enzyme (acetylcholinesterase) which destroys ACh
• discovered by the indigenous people of South America - used curacine found on tree bark as arrow poison to cause flaccid paralysis in animals

Question 25

Example of a competitive reversible antagonist of ACh

Answer 25

Tubocurarine

Question 26

Subunits of GABA(A) receptors

Answer 26

- beta subunit: principal subunit for GABA - alpha subunits: principal subunit for BZs - all subunits: 2 cysteines, alpha-alphas apart

Question 27

The GABA(A) receptor and its associated binding sites (5 points)

Answer 27

1. the receptor is pentameric, being composed of 2 alpha, 2 beta, and 1 gamma subunit 2. GABA(A) receptors contain recognitions sites for a variety of clinically relevant drugs 3. the binding of GABA in 2 GABA binding sites at the interface between alpha and beta subunits open the receptor associated chloride channel 4. the benzodiazepine binding site is located at the interface between alpha and gamma-2 subunits 5. barbiturates, ethanol, and neurosteroids bind to sites in the membrane - spanning transmembrane regions of the subunits

Question 28

What structure is the GABA(A) receptor?

Answer 28

The receptor is pentameric, being composed of 2 alpha, 2 beta, and 1 gamma subunit

Question 29

What sites do GABA(A) receptors contain?

Answer 29

GABA(A) receptors contain recognitions sites for a variety of clinically relevant drugs

Question 30

What causes the receptor associated chloride channel to open?

Answer 30

The binding of GABA in 2 GABA binding sites at the interface between alpha and beta subunits open the receptor associated chloride channel

Question 31

Where is the benzodiazepine binding site located?

Answer 31

The benzodiazepine binding site is located at the interface between alpha and gamma-2 subunits

Question 32

What compounds bind to sites in the membrane?

Answer 32

Barbiturates, ethanol, and neurosteroids bind to sites in the membrane - spanning transmembrane regions of the subunits

Question 33

Give two examples of ligand gated ion channels and the synaptic potentials

Answer 33

1. acetylcholine produces excitatory post synaptic potentials (epsps) 2. GABA and glycine produce inhibitory post synaptic potentials (ipsps)

Question 34

When there is a stimulus, what does acetylcholine production cause?

Answer 34

An action potential on the post synaptic cleft because there is an influx of sodium

Question 35

When there is a stimulus, what does GABA(A) receptor cause?

Answer 35

- an inhibitory action in the post synaptic cell, in the post synaptic neurons - basically switches cell activity off - causes a tranquillising effect

Question 36

What happens when the GABA binds to the GABA receptor?

Answer 36

The receptor forms a channel in the cell membrane, allowing the passage of negatively charged chloride ions into the cell - this causes hyper polarisation - as you increase the negative charge, action action potential is reduced, and the system is depressed - the cell responds by coming inhibited - the opposite of an action potential - any action potentials in the post-synaptic neuron would be blocked

Question 37

What does the GABA(A) receptor do?

Answer 37

Opens a chloride ion channel causing hyper polarisation and cell inhibition