Neurotransmitters

Question 1

What is a ligand?

Answer 1

a neurotransmitter, catecholamine, or drug that binds to a receptor and stimulates or inhibits some cellular function.

Question 2

What do neurotransmitter signal transduction pathways depend on?

Answer 2

TYPE of receptor and WHERE receptor is, and WHICH neurotransmitter binds to it

Question 3

Which 2 types of receptors are fast response receptors?

Answer 3

Ion receptors–ligand gated/voltage gated/other gated; and g-protein coupled receptors

Question 4

Which 2 types of receptors are slow response receptors?

Answer 4

Enzyme linked transmembrane receptors and intracellular receptors.

Question 5

Which receptor types are within the phospholipid membrane?

Answer 5

ligand gated, g-protein coupled, and enzyme linked transmembrane

Question 6

Name types of ligand-gated ion channels.

Answer 6

Acetylcholine-neuromuscular blocking drugs, serotonin 5HT3, GABA-barbiturates and benzos, NMDA-ketamine and glycine receptors

Question 7

Describe ligand gated ion receptors.

Answer 7

binding of the neurotransmitter causes a conformational change in the receptor which causes the ion channel to open or close. FAST RESPONSE. Examples: Nicotinic, NMDA, GABAa

Question 8

Describe voltage sensitive ion channels.

Answer 8

gated by an ion, no ligand. Extracellular depolarization causing ions to flow. sodium, chloride, potassium, and calcium channels, depolarization causes ion flow through pores. in neurons, skeletal muscle and endocrine cells. LOCAL ANESTHETICS work here

Question 9

Describe g-protein coupled receptors.

Answer 9

MOST ABUNDANT receptors in body, FAST, activates or inhibits an enzyme, ion channel, or other target receptor. Involves 2nd messengers. ex: hormones, catecholamines, opioids, anticholinergics, and antihistamines. ligand binds to a receptor, g-protein ignites effector protein involving intracellular messenger. ion shift or intracellular response

Question 10

What is the difference between g-protein and ligand-gated receptors.

Answer 10

g-protein stimulate or inhibit intracellular messenger

Question 11

Describe enzyme linked transmembrane receptors

Answer 11

SLOW, in luminal membrane, most are tyrosine kinases that use 2nd messenger. ex: insulin receptor, atrial natriuretic peptide, growth hormones.

Question 12

Describe intracellular receptors.

Answer 12

SLOWEST, can cause response in or out of cell. ex: steroid receptors, thyroid hormone receptors, phosphodiesterase inhibitors.

Question 13

Describe neurotransmitters and give examples.

Answer 13

secreted by neurons and act locally on other neurons. generally small organic molecules but polypeptides are larger. EX: acetylcholine, dopamine, NE, epi, histamine, serotonin, substance P, glutamate/aspartate, GABA/glycine

Question 14

True/False: neurotransmitters produce the same effect in different locations depending on types of receptors present.

Answer 14

False. they produce DIFFERENT effects in different locations depending on types of receptors present.

Question 15

Discuss acetylcholine synthesis.

Answer 15

AcetylCoA and choline are presynaptic and react with choline acetyltransferase to form acetylcholine.

Question 16

Discuss acetylcholine degradation.

Answer 16

Acetylcholine and water combine with acetylcholinesterase and form acetic acid and choline. Acetate diffuses away and choline goes back to presynaptic neuron and reused to make more ACh.

Question 17

How does acetylchoine work?

Answer 17

Exocytosis of ACh needed for signal transduction to occur. The basis for all interactions in the para and sympathetic nervous system.

Question 18

Describe nicotinic receptors.

Answer 18

ligand-gated ion channel located between pre and post ganglionic neurons in para and sympathetic nervous system. ion channel opens allowing intracellular influx of Na+. located at NMJ, autonomic ganglia, and CNS.

Question 19

What are nicotinic receptors stimulated by?

Answer 19

ACh, succinylcholine, and nicotine (not at NMJ)

Question 20

What are nicotinic receptors blocked by?

Answer 20

NDMR (at NMJ) and trimethaphan (at autonomic ganglia)

Question 21

Describe muscarinic receptors.

Answer 21

different from nicotinic; between post ganglionic and effector sites in 2 areas (1 para and 1 SNS), G-protein coupled. 5 subtypes M1-M5 located in CNS and organs of PNS. Includes 2nd messenger system.

Question 22

What stimulates muscarinic receptors and what happens?

Answer 22

ACh and muscarine: salivary and sweat gland secretion, pupillary constriction, increases GI peristalsis, slows conduction of SA and AV nodes in heart (M2 receptor)

Question 23

Where are receptors and neurotransmitters located?

Answer 23

between pre and post ganglia, no matter whether in SNS or PNS.

Question 24

Where are catecholamines located?

Answer 24

between post ganglionic and effector cell, mainly SNS

Question 25

Describe catecholamines and give examples.

Answer 25

synthesized by various neurons depending on the enzymes present. dopamine, epi, NE.

Question 26

Where does dopamine act?

Answer 26

CNS neurons

Question 27

Where does epi act?

Answer 27

second order neurons of SNS in adrenal medulla

Question 28

Where does NE act?

Answer 28

second-order neurons of the SNS, adrenal medulla, and CNS neurons

Question 29

Where is dopamine synthesized?

Answer 29

CNS, doesnt cross BBB

Question 30

What are the 2 receptor classes for dopamine?

Answer 30

D1-like (D1 and D5) and D2-like (D2, D3, and D4)

Question 31

What do D1-like receptors do?

Answer 31

increase cAMP

Question 32

What do D2-like receptors do?

Answer 32

decrease cAMP

Question 33

What are the central functions of dopamine?

Answer 33

Memory, problem-solving, reward-pleasure behavior, inhibition of prolactin secretion, fine control of movement, N/V CTZ.

Question 34

What are the peripheral functions of dopamine?

Answer 34

coronary and renal vasodilation, higher serum concentrations affect beta-1 and alpha-1 receptors

Question 35

What are dopamine receptors are stimulated by?

Answer 35

dopamine and L-dopa

Question 36

What happens when dopamine receptors are agonized?

Answer 36

psychosis, euphoria, orthostatic hypotension, nausea

Question 37

What blocks dopamine receptors?

Answer 37

haldol, antipsychotics, antiemetics.

Question 38

What are the side effects of dopamine receptor antagonists?

Answer 38

parkinsonism, extrapyramidal reactions, hyperprolactinemia

Question 39

What terminates the action of dopamine?

Answer 39

diffusion away from the site, reuptake into pre-synaptic neuron, recycled and re-packaged, metabolized

Question 40

There are _____ major classes and _____ types of adrenergic receptors.

Answer 40

2; 5

Question 41

What are the types and classes of adrenergic receptors?

Answer 41

alpha-1, alpha-2, beta-1, beta-2, beta-3

Question 42

What terminates the action of norepi and epi?

Answer 42

diffusion away from the site, reuptake into the pre-synaptic neuron, recycled and repackaged, metabolized.

Question 43

What is histamine?

Answer 43

intrinsic neurotransmitter, synthesized from histadine in CNS (maintaining wakefulness), immune cells (basophils/mast cells), and GI tract (secreted by mast cells in stomach wall)

Question 44

How many types of Histamine receptors are there?

Answer 44

3

Question 45

Where are H1 receptors located?

Answer 45

vascular smooth muscle (dilation) and bronchial smooth muscle (contraction) and in CNS

Question 46

What are H1 antagonists?

Answer 46

diphenhydramine, loratidine

Question 47

Where are H2 receptors located?

Answer 47

stomach (increased acid secretion)

Question 48

What are H2 antagonists?

Answer 48

famotidine to increase gastric pH

Question 49

Where are H3 receptors located?

Answer 49

presynaptic reduction in further histamine release. negative feedback loop, don't send more histamine

Question 50

Where is serotonin (5-hydroxytryptamine) found and what does it do?

Answer 50

intestine--regulates intestinal movement; raphe nucleus in brainstem and projects to other regions of the brain to affect mood, cognition, sleep

Question 51

How many families of serotonin receptors are there?

Answer 51

7

Question 52

What type of receptor are the serotonin receptors 5-HT1,2,4,5,6,7?

Answer 52

g-protein coupled

Question 53

What type of receptor is 5-HT3?

Answer 53

ligand gated Na and K cation channel. Depolarizes plasma membrane, excitatory, only type that is ionotropic.

Question 54

What does 5-HT3 cause?

Answer 54

nausea

Question 55

What are other effects of serotonin?

Answer 55

addiction, aggression, vasoconstriction, increased intestinal motility, learning and memory consolidation

Question 56

What are some serotonin agonists?

Answer 56

busiprone: anxiety; triptans: migraines; LSD, psilocin: psychedelic drugs; cisapride: increases GI motility

Question 57

What are some serotonin antagonists?

Answer 57

ondansetron, risperidone: antipsychotic

Question 58

What is substance P's claim to fame?

Answer 58

primary neurotransmitter produced by pain/temp afferent peripheral neurons

Question 59

What are the substance P receptors?

Answer 59

neurokinin receptors (NK1, NK2, NK3)

Question 60

Where else are substance P receptors located?

Answer 60

gut/CTZ--nausea/emesis pathways

Question 61

What does blocking Substance P do?

Answer 61

reduce N/V

Question 62

What neurotransmitters are associated with PONV?

Answer 62

dopamine, serotonin, acetylcholine, Histamine, (opioids), Substance P

Question 63

What is the primary brain excitatory neurotransmitter?

Answer 63

Glutamate, most prominent in brain

Question 64

What is the primary spinal cord excitatory neurotransmitter?

Answer 64

aspartate

Question 65

Does glutamate cross the BBB?

Answer 65

No, it's charged

Question 66

How is glutamate synthesized?

Answer 66

from glutamine (which does cross the BBB)

Question 67

What is an important Glutamate Receptor?

Answer 67

NMDA receptor (an ionotropic receptor)

Question 68

Describe an NMDA receptor.

Answer 68

N-methyl-d-aspartate receptor, non-specific cation channel, Na and Ca enter cell and K leaves the cell resulting in neuronal depolarization.

Question 69

What is required to activate an NMDA receptor?

Answer 69

glutamate AND glycine

Question 70

What are some NMDA receptor antagonists?

Answer 70

dextromethorphan, Ketamine, N2O, Mg, methadone

Question 71

What is the primary inhibitory neurotransmitter in the brain?

Answer 71

GABA (gamma amino butyric acid).

Question 72

What is the 2nd most abundant neurotransmitter in the brain?

Answer 72

GABA

Question 73

What is the primary inhibitory neurotransmitter in the spinal cord?

Answer 73

glycine

Question 74

Where is GABA synthesized?

Answer 74

pre-synaptic neuron from glutamate, the primary excitatory neurotransmitter is converted to the primary inhibitory neurotransmitter.

Question 75

What type of receptors are GABAa receptors?

Answer 75

ionotropic ligand-gated ion channels

Question 76

How does a GABAa receptor work?

Answer 76

allows passage of Cl- from extracellular to intracellular and the increased intracellular Cl- leads to hyperpolarization of the neuron causing it to be less likely to fire

Question 77

Define allosteric regulation.

Answer 77

drug or chemical binds to a receptor at a site different from primary site and alters regulation of action of receptor's primary agonists and antagonists. can increase receptors affinity for its primary neurotransmitter or decrease the affinity.

Question 78

What do positive allosteric modulators do?

Answer 78

enhance the affinity of the receptor for GABA

Question 79

Name some positive allosteric modulators.

Answer 79

barbiturates, propofol, etomidate, benzos, steroids

Question 80

Name some negative allosteric modulators

Answer 80

Flumazenil. decrease the action of GABA at this receptor

Question 81

What type of receptors are GABAb receptors?

Answer 81

g-protein

Question 82

What do GABAb receptors do?

Answer 82

cause intracellular changes resulting in opening of K channel, K leaves neuron resulting in neuronal hyperpolarizaiton aka inhibition.

Question 83

What are some GABAb agonists?

Answer 83

baclofen, gamma hydroxybutyrate, ecstasy, date rape drug

Question 84

The practice of anesthesia involves the manipulation of neurotransmitters in both _______ and ________.

Answer 84

health and disease.