Neuronal Communication

Question 1

function & type of ion channel of dendrites

Answer 1

receives input from neurons (local potentials)

chemically-gated ion channels

Question 2

function & type of ion channel of the cell body (soma)

Answer 2

receives input from neurons (local potentials)

chemically-gated ion channels

Question 3

function & type of ion channel of the axon hillock

Answer 3

summates the local potentials -> generates action potential

voltage-gated ion channels

Question 4

function & type of ion channel of the axon

Answer 4

sends action potential down the axon

voltage-gated ion channels

Question 5

function & type of ion channel of axon terminals

Answer 5

releases neurotransmitter to initiate a response in target cell
voltage-gated ion channels

Question 6

meaning of pre-synaptic neuron

Answer 6

before the synapse

Question 7

meaning of post-synaptic neuron

Answer 7

after the synapse

Question 8

meaning of synapse

Answer 8

the junction between the pre-synaptic and the post-synaptic neuron

Question 9

structure & function of neuronal input

Answer 9

the post-synaptic neuron receives input form the axon terminals of the pre-synaptic neuron
this input creates a local potential

Question 10

how do neurons send signals to other cells?

Answer 10

by transmitting a chemical - a neurotransmitter

Question 11

where is a neurotransmitter released from?

Answer 11

the pre-synaptic cleft, then crosses the synaptic cleft

Question 12

what does the neurotransmitter bind to?

Answer 12

receptors on the post-synaptic cell, opening chemically-gated ion channels

Question 13

excitatory neurotransmitter definition

Answer 13

Na+ enters neuron -> brings membrane potential CLOSER to threshold (depolarising)

Question 14

inhibitory neurotransmitter definition

Answer 14

Na+ leaves neuron -> moves the membrane potential AWAY from threshold (hyper polarising)

Question 15

steps of neuronal input

Answer 15

1. pre-synaptic neuron releases excitatory neurotransmitter -> brings the neuron closer to threshold
2. pre-synaptic neuron releases more excitatory neurotransmitter -> brings the neuron to threshold
3. all of the inputs onto the neuron are summated (added) at the axon hillock -> if the axon hillock reaches threshold (-60mV) then the neuron will fire an action potential down its axon

Question 16

function of integration in the axon hillock

Answer 16

all local (graded) voltage changes add up at the axon hillock
if the net threshold at the axon hillock reaches -60mV then an action potential will fire

Question 17

local potentials vs. action potentials

Answer 17

local potentials = small changes (graded response) in membrane potential at the cell body/dendrites -> INPUT
action potentials = propagate down the axon

Question 18

local potentials function

Answer 18

graded response - depolarises or hyperpolarizes the membrane to different levels
does not propagate
chemical-gated ion channels

Question 19

action potentials function

Answer 19

all or nothing - either the same size action potential or no action potential
depolarises to the same level (+30mV) each time
propagates down the axon
voltage-gated ion channels

Question 20

3 steps of propagation of an action potential

Answer 20

• the action potential regenerates down the length of the axon fast*
  1. voltage-gated Na+ channels closed - RMP = -70mV
  2. voltage-gated Na+ channels open - Na+ enter neuron; membrane potential increases to +30mV
  3. voltage-gated Na+ channels closed, voltage-gated K+ channels open - K+ leaves the neuron; membrane returns to RMP

Question 21

propagation myelinated axons structure & function

Answer 21

myelin is made from a specialised cell called a Schwann cell, and it wrapped around the axon
the action potential regenerates at each gap between the myelin sheath
unmyelinated axons are fast
myelinated axons are really fast

Question 22

5 steps of the output of neural communication

Answer 22

1. depolarisation of axon terminal -> voltage-gated Ca2+ channels open -> Ca2+ enters axon terminal
2. Ca2+ triggers neurotransmitter to be released from vesicles into the synaptic cleft
3. neurotransmitter diffuses across the synaptic cleft
4. neurotransmitter binds to its receptor (chemically-gated ion channel) on the post-synaptic membrane
5. Na+ enters the post-synaptic cell -> depolarises post-synapse cell