Neurotransmission

Question 1

what are the components of a neuron?

Answer 1

dendrites - receive information
soma - cell body, controls cell processing
axon - carries info from soma to terminal boutons
terminal boutons - at the end of the axon, location of the synapse

Question 2

what is the neuronal membrane made up of?

Answer 2

a lipid bilayer - hydrophillic and hydrophobic layers which only allow certain substances in and out of the cell

Question 3

what is a membrane potential?

Answer 3

a potential gradient that creates the movement of particles across a membrane due to two forces

Question 4

when the cell is at rest, what are it’s potentials?

Answer 4

the inside is more negatively charged than the outside

Question 5

what is used to measure flow and strength of electrical voltage?

Answer 5

voltmeter

Question 6

what causes there to be a membrane potential?

Answer 6

force of diffusion - molecules move from a high to a low concentration
force of electrostatic pressure - opposite charges attract and the same charges repel

Question 7

describe how an equilibrium potential happens

Answer 7

• positive ions move across membranes by diffusion force
• as more positive ions move there is an increase in the electrical potential across the membrane
• eventually a point is reached when the diffusion force = the electrostatic force

Question 8

what charge are organic ions?

Answer 8

negative

Question 9

why does the membrane come to rest near the potassium equilibrium potential?

Answer 9

because more potassium channels are open than sodium channels, meaning that more potassium than sodium ions can diffuse

Question 10

what does the Nernst equation?

Answer 10

it can calculate the equilibrium potential for any ion

Question 11

what mechanism maintains the ionic concentration gradients across the membrane?

Answer 11

sodium potassium pumps
ATP (made by mitochondria) is broken down to release energy which forces the ions to move against their concentration gradient

Question 12

what is an action potential?

Answer 12

a nerve impulse which travels down the axon and allows communication with the neuron.
it is generated at the axon hillock
it is generated by the summation of converging inputs from dendrites

Question 13

what is hyperpolarisation?

Answer 13

when the membrane potential is more negative than the resting membrane potential, causing more positive ions to move out and negative ions to move in.
it inhibits action potentials

Question 14

what is the term used to describe: the membrane is more positive than at resting membrane potential, more positive ions move in and negative ions move out.

Answer 14

depolarisation

Question 15

what is decremental conductance?

Answer 15

when stimulated, depolarisation occurs which decays as it moves through the neuron

Question 16

where does an action potential come from?

Answer 16

stimulation causes sodium channels to open, and NA rushes in. once depolarisation threshold is reached the AP is fired. an all or nothing response

Question 17

describe voltage gated channels

Answer 17

there are two types:

• sodium channel: activated at rest and inactivated at the refractory period
• potassium channel: activated with lots of depolarisation, inactivated when too little depolarisation

Question 18

describe the process of action potentials firing

Answer 18

• at resting membrane potential most of the voltage gated channels are closed
• a small depolarisation opens a few sodium channels leading to further depolarisation
• if the stimulation is above the action potential threshold most of the sodium channels open, more sodium moves in, further depolarisation
• some potassium channels open, potassium leaves through diffusion
• the inside of the neuron is now more positive so sodium channels become deactivated (refractory period)
• potassium continues to leave and makes the membrane potential negative (repolarisation)
• both channels close, hyperpolarisation occurs
• potassium channels close and external potassium is diffused away, resting membrane potential is restored

Question 19

what are the two cells that create myelin sheaths?

Answer 19

oligodendroglial cells - cns

schwann cells- pns

Question 20

what is the only place where action potentials can occur and why?

Answer 20

the nodes of ranvier - the only place sodium and potassium ions can pass, a gap in the myelin sheath

Question 21

what are the two types of synapses?

Answer 21

electrical(rare)

chemical - chemicals released from presynaptic to postsynaptic neuron

Question 22

what are the types of modulation of signal?

Answer 22

axodendritic, axosomatic, axoaxonic

Question 23

what leads to neurotransmitter release?

Answer 23

influx of calcium ions

Question 24

where are inputs summated?

Answer 24

soma

Question 25

what are neurotransmitters?

Answer 25

chemicals used to transmit information from pre to post-synaptic neurons

Question 26

what are the types of receptors on the postsynaptic membrane?

Answer 26

ionotropic receptor - fast transmission

metabotropic receptor - slower transmission

Question 27

glutamate and GABA are part of what class of neurotransmitter?

Answer 27

amino acids

Question 28

describe glutamate

Answer 28

a fast excitatory neurotransmitter in the CNS

Question 29

describe GABA

Answer 29

a inhibitory neurotransmitter

Question 30

can EPSPs be abolish/decreased?

Answer 30

yes, by IPSPs that are active at the same time

Question 31

what are autoreceptors?

Answer 31

• located on presynaptic terminal
• respond to neurotransmitters in the synaptic cleft
• control neuronal communication
• negative feedback mechanism

Question 32

what is the refractory period?

Answer 32

a period of time where the cell can’t repeat a particular action. happens after an AP is fired