EXAM I Intro to the Nervous System

Question 1

describe the general principles of direct actions of neurotransmitters

Answer 1

• NT binds to and opens ion channels
• promotes rapid responses by altering membrane potential

Question 2

describe the general principles of indirect actions of neurotransmitters

Answer 2

• NT acts through intracellular second messengers, usually G protein pathways
• broader, longer-lasting effects

Question 3

___ is an excitatory neurotransmitter

Answer 3

glutamate

Question 4

___ and ___ are inhibitory neurotransmitters

Answer 4

dopamine and GABA

Question 5

___, ___, and ___ are both excitatory and inhibitory neurotransmitters

Answer 5

acetylcholine, norepinephrine, and serotonin

Question 6

is GABA a direct or indirect acting neurotransmitter?

Answer 6

direct

Question 7

___ membrane channels open and close in response to voltage changes across the membrane; what are some examples?

Answer 7

• voltage-gated
• examples: voltage-gated Na+ channels and lidocaine

Question 8

___ membrane channels involve a hormone, drug, or transmitter than bind to the protein and the channel opens up; what are some examples?

Answer 8

• ligand-gated (ionotropic)
• examples: glutamate (AMPA), nicotine ACh receptors, and GABA

Question 9

what is the action length of ligand-gated (ionotropic) receptors?

Answer 9

action is immediate and brief

Question 10

are ligand-gated (ionotropic) receptors excitatory or inhibitory?

Answer 10

• some are excitatory and open channels for small cations
• some are inhibitory and allow Cl- influx or K+ efflux to cause hyperpolarization

Question 11

T or F:

metabotropic receptors are not directly linked to ion channels

Answer 11

true

Question 12

how do metabotropic receptors work?

Answer 12

• initiates a biochemical process that mediates more long-term effects and modifies the responsiveness of the neuron
• NT acts as the first messenger which activates a second messenger that in turn changes the excitability of a neuron

Question 13

what are the two types of metabotropic receptors?

Answer 13

• membrane-delimited - occur entirely in plane of membrane
  
  • when G-proteins interact with calcium channels, they inhibit channel function (presynaptic inhibition)
  • when G-proteins interact with K+ channels, they open (activate) channels causing postsynaptic inhibition
• diffusible second messengers

Question 14

what are examples of diffusible second messengers (metabotropic)?

Answer 14

beta-adrenergic receptors and cAMP

Question 15

___ are receptors on an axon terminal through which the neuron’s own NT can influence the function of the terminal (usually inhibitory) - for example, D2 receptors

Answer 15

autoreceptors

Question 16

___ are receptors on an axon terminal through which NTs from other neuronal types can influence the function of the terminal

Answer 16

heteroreceptor

Question 17

what are the 3 catecholamines?

Answer 17

dopamine, norepinephrine, and epinephrine

Question 18

___ can act like dopamine due to its similar structure

Answer 18

amphetamine

Question 19

which enzyme catalyzes the conversion of NE to epi?

Answer 19

phenylethanolamine-N-methyltransferase (PNMT)

Question 20

epinephrine is typically made by ___, but can also be made by some ___

Answer 20

• adrenal medullary cells
• CNS neurons

Question 21

what is a monoamine?

Answer 21

one amino group connected to an aromatic group by a 2-carbon chain

Question 22

what are 3 exmamples of monoamines?

Answer 22

catecholamines, serotonin, histamine

Question 23

is serotonin a catecholamine?

Answer 23

no, it is an indoleamine

Question 24

which amino acid is inhibitory?

Answer 24

GABA

Question 25

which amino acid is excitatory?

Answer 25

glutamate

Question 26

H3 (histamine) receptor is thought to function as an ___

Answer 26

inhibitory heteroreceptor

thus, activtaion of brain H3 receptors decreases the release of acetylcholine, dopamine, norepinephrine, serotonin, and certain peptides

Question 27

what is neurotensin? where is it found?

Answer 27

• a neuropeptide that acts as an endogenous neuroleptic and regulates dopamine systems (inhibitory feedback)
• it is found in the GI tract (inhibits GI motility) and circulation (causes vasodilation)

Question 28

describe nitric oxide

Answer 28

• gaseous signaling molecule
• CNS role is controversial
• relaxes vascular smooth muscle

Question 29

how do endorphins make you happy?

Answer 29

endorphins bind to µ receptors, causing a decrease in GABA release, which causes an increase in dopamine release (= happy feeling)