changing membrane potential

Question 1

define depolarisation

Answer 1

decrease in the size of the membrane potential from its normal value
cell interior becomes less negative
-70mV to -50mV

Question 2

define hyperpolarization

Answer 2

increase in the size of the membrane potential from its normal value
cell interior becomes more negative
-70mV to -90mV

Question 3

how can membrane potential be changed

Answer 3

changing the selectivity between ions
increasing membrane permeability to a particular ion moves the membrane potential towards the eqm potential for that ion.
k+ eqm potential is -95mV so opening k+ channels will cause hyperpolarization.

Question 4

what are the types of gating

Answer 4

ligand gating
voltage gating
mechanical gating

Question 5

explain ligand gating

Answer 5

channel opens/closes in respose to binding of a chemical ligand e.g ACh
e.g channels at synapses that respond to extracellular transmitters
channels that respond to intracellular messages

Question 6

explain voltage gating

Answer 6

channels open/close in response to changes in membrane potential
e.g channels involved with action potentials

Question 7

explain mechanical gating

Answer 7

channel opens/closes in reponse to membrane deformation.

e.g channels in mechanoreceptors

Question 8

what cells can synaptic connections occur between

Answer 8

nerve cell-nerve cell
nerve cell -muscle cell
nerve cell -gland cell
sensory cell -nerve cell

Question 9

explain fast synaptic transmission

Answer 9

the receptor protein is also an ion channel
very rapid process
transmitter binding causes the channel to open

Question 10

what do excitatory transmitters do

Answer 10

open ligand gated channels that cause membranes depolarisation.
resulting change in membrane potential is called an excitatory post-synaptic potential (EPSP)
can be permeable Na+, Ca2+
transmitters include: ACh, glutamate

Question 11

what do inhibitory transmitters do

Answer 11

open ligand gated channels that cause hyperpolarization
permeable to K+ or Cl-
resulting change in membrane potential is called inhibitory post-synaptic potential (IPSP)
transmitters include : glycine, GABA

Question 12

explain slow synaptic transmission

Answer 12

receptor and channel are separate proteins

1. direct G-protein gating- this localised and quite rapid
2. gating via intracellular messenger-G protein activates enzyme that stimulates a signalling cascade.

Question 13

what factors can influence membrane potential

Answer 13

1) changes in ion concentration - K+ conc most importantly.

2) Electrogenic pumps