part 8

Question 0

the excitatory action of an EPSP is when?

Answer 0

membrane depolarizes closer to threshold of action potential, thus increasing excitability.

Question 1

Describe Excitatory Postsynaptic Potentials (EPSP).

Answer 1

depolarization caused by an increase in permeability of Na+ and K+ channel

Question 2

What leads to an Inhibitory Postsynaptic Potential (IPSP)?

Answer 2

hyperpolarization caused by increase in permeability of Cl- or K+ channel
– Influx of Cl- ions and efflux of K+ ions hyperpolarize membrane

Question 3

describe the Inhibitory action of an IPSP?

Answer 3

membrane hyperpolarizes away from threshold, decreasing excitability.

Question 4

Excitatory synapses usually occur on?

Answer 4

dendrites

Question 5

inhibitory synapses usually occur on ?

Answer 5

cell bodies

Question 6

simultaneous activation of excitatory synaptic potentials from different regions is known as ?

Answer 6

Spatial summation of psp’s

Question 7

successive synaptic potentials from same synapse can summate to create overall excitation or inhibition. this is known as?

Answer 7

Temporal summation of PSP’s

Question 8

what produces EEG waves?

Answer 8

Synchronization of PSPs among large populations of neurons

Question 9

“analog” information processing of PSPs is done at what two regions of a neuron?

Answer 9

Dendrites and cell bodies

Question 10

Axon potential initiation happens at the ?

Answer 10

Axon Hillock

Question 11

“digital” information is processed by the ?

Answer 11

Axon

Question 12

Non-gated channels have ___ ion channels and are located __?

Answer 12

K+

along whole cell except initial segment & nodes of Ranvier

Question 13

Voltage gated channels have __, __, __ ion channels and are located __?

Answer 13

Na+, K+, Ca++
(Na+, K+) Initial segment, nodes of Ranvier (APs),
(Ca++) Axon terminal (transmitter release)

Question 14

neruotransmitter/ ligand gated channels have __, __, __ ion channels and are located __?

Answer 14

Na+,K+, Cl-
(Na+,K+) Postsynaptic dendrite membranes (EPSP’s)
(Cl-) Postsynaptic cell body membrane (IPSP’s)

Question 15

what does METABOTROPIC (INDIRECTLY) GATED TRANSMISSION involve?

Answer 15

Involves cell signaling systems that utilize enzymes and/or genomic regulation (“metabolism”)

Question 16

Compare metabotropic and Ionotropic transmissions

Answer 16

ionotropic transmission: the receptor for the transmitter is on the ion channel itself. The response is fast, but of short duration
metabotropic transmission: the receptor is a membrane protein that activates a cascade of enzymes that stimulate synthesis of second messengers and/or alter gene activity.

Question 17

These proteins are a complex of α, β, and γ units that dissociate from the receptor protein and activate other enzymes to produce second messengers.

Answer 17

G proteins

They utilize GTP (Guanosine triphosphate), hence the name G.

Question 18

these Proteins are the most important signal transducing molecules in cells

Answer 18

G PROTEINS

Question 19

two ways in which Ligand receptor activates G protein?

Answer 19

1. Transmitter causes receptor to bind with inactive G protein
2. GTP replaces GDP, activating the G protein

Question 20

3 ways in which α, β, γ portions of activated G protein generate cell activity?

Answer 20

1. Direct action on the permeability of ion channels
2. Activation of second messengers (eg. cAMP)
3. Gene transcription of proteins

Question 21

Explain how Direct action of G proteins on ion channels works?

Answer 21

• β, γ portions G protein bind directly onto ion channels to alter its permeability
for example.. In heart deceleration, vagus nerve stimulates the SA node using Ach to open K channels and hyperpolarize the cell. This inhibits cardiac action potentials and decreases the heart rate

Question 22

two primary examples of second messengers that occur in all body cells?

Answer 22

cAMP and IP3/DAG

Question 23

explain the second messenger cascade?

Answer 23

G protein >Enzyme > 2nd messenger >Effector (kinase or other enzymes) >Cell function

Question 24

explain the entire metabotropic action leading to a cell response

Answer 24

Ligand (first messenger) binds to a receptor, this activates a G protein, this activates an amplifier enzyme (adenylate C, guanylate C or phospholipase C) these get phosphorlated to ATP, GTP or PIP, which activate second messangers (cAMP,cGMP, IP3/DAG) which activate a intracellular effector which leads to a cell response!!

Question 25

explain the funamentals of cyclic AMP

Answer 25

• G protein stimulates adenyl cyclase to convert ATP to cAMP

* cAMP activates the enzyme PKA via phosphorylation.

Question 26

explain step 1 of the signal transduction pathway using cAMP

Answer 26

a signaling molecule activates GPCR (G protein coupled receptor). this causes G protein to bind GTP, thereby promoting the dissociation of the α subunit from the β/γ dimmer.

Question 27

explain step 2 of the signal transduction pathway using cAMP.

Answer 27

the binding of the α subunit to adenyl cyclase promotes the synthesis of cAMP from ATP.

Question 28

explain step 3 of the signal transduction pathway using cAMP.

Answer 28

cAMP binds to the regulatory subunits of PKA, which releases catalytic subunits of PKA.

Question 29

explain step 4 of the signal transduction pathway using cAMP.

Answer 29

the catalytic subunits of PKA use ATP to phosphorylate specific cellular proteins thereby cause a cellular response.

Question 30

Stimulatory vs inhibitory effects of G proteins on cAMP depends on this portion of a G protein?

Answer 30

alpha portion

total amount of cAMP in cell depends on balance between the two effects.

Question 31

Explain the basic differences in signal amplification between metabotropic and ionotropic transmission

Answer 31

• Metabotropic transmission uses G proteins to amplify a cell’s response to ligands / transmitters.
• Ionotropic transmission is fast with a short duration

Question 32

explain Some actions of cAMP

Answer 32

• cAMP induces PKA phosphorylation of contractile proteins, ion channels, enzymes and regulatory proteins.
• Produce long term (hours) changes in neuronal excitability by altering permeability of “non- gated” K+ channels.
• cAMP regulates metabolic pathways
– Convert glycogen to glucose in liver & muscle cells
– Release fatty acids from adipose cells
In adipocytes, cAMP stimulates hormone sensitive lipase (HSL) to facilitate triglyceride breakdown into fatty acids.

Question 33

how are second messengers inositol triphosphate (IP3) and

diacylglycerol (DAG) created from G proteins?

Answer 33

G protein activates phospholipase C (PLC), which cleaves phosphatidyl inositol (PIP) into second messengers (IP3 and DAG)

Question 34

IP3 releases Ca++ from endoplasmic reticulum. what becomes of these two molecules?

Answer 34

– Ca regulates smooth muscle contraction, cell secretion, etc.
– IP3 is degraded to inositol and reincorporated into the membrane. (Inhibited by Lithium)

Question 35

DAG (Diacylglycerol) activates the enzyme protein kinase C, which promotes ?

Answer 35

cell division and proliferation

Question 36

Li acts in these two areas to improve memory?

Answer 36

hippocampus in the limbic system

Question 37

Lithium has many actions including:

Answer 37

mood and memory stabilization by:
• Inhibition of glycogen synthase kinase-3 (GSK-3) blocks protein degradation and apoptosis of neurons
• Inhibition of inositol monophosphatase (IMP-ase) leads to increased IP3 and long term modulation of synaptic connections and modulation of neuronal circuits

Question 38

G proteins can alter genomic regulation through the use of cAMP by this mechanisim?

Answer 38

cAMP > PKA > CREB
– PKA phosphorylates a transcriptional activator CREB (cAMP
response element binding protein).
CREB proteins are transcription factors that can produce long term changes in the functions of ion channels.

Question 39

briefly explain up or down regulation in ion channels

Answer 39

cAMP-activated proteins interact with regulatory TF on the DNA to up or down regulate gene expression
• Effects last for hours to several days
• Mediated by changes in rate of receptor turnover, receptor gene transcription or receptor mRNA turnover.