L9: Neurons & Neuronal: Synapses

Question 1

Function of a synapse

Answer 1

Allows a neuron to pass an electrical or chemical signal to another neuron

Question 2

What is a synapse?

Answer 2

Tiny gap where 2 neurons “talk” to each other
- 1 neuron can send a chemical message to the next neuron

Question 3

Structure of a synapse

Answer 3

1) Presynaptic neuron: sender
2) Synaptic cleft: tiny gap
3) Postsynaptic neuron: receiver

Question 4

3 types of synapses

Answer 4

1) Axodendritic
2) Axosomatic
3) Axoaxonic

Question 5

What is an axosomatic synapse?

Answer 5

Axon of 1 neuron attaches to the cell body of another neuron

Question 6

What is an axodendritic synapse?

Answer 6

Axon of 1 neuron terminates on the dendrite of another neuron

Question 7

What is an axoaxonic synapse?

Answer 7

Axons of 2 different neurons meet

Question 8

What is a electrical synapse?

Answer 8

Neurotransmitter-mediated communication

Question 9

What is a chemical synapse?

Answer 9

Direct connection via gap junctions allowing ion flow

Question 10

What are gap junctions?

Answer 10

Allow the exchange of ions between cells

Question 11

Components of the neuron, and what are their functions?

Answer 11

1) Dendrite: Receive signals
2) Cell Body (Soma): Process information
3) Axon: Transport signals to next neuron

Question 12

Describe synaptic communication

Answer 12

1) Neuron at resting potential
2) Voltage-gated Ca2+ channels open, influx
3) Ca2+ triggers exocytosis
4) NT diffuses along cleft & activates post-synaptic cell

Question 13

What is a graded potential?

Answer 13

Changes in membrane potential depending on strength of stimulus

Question 14

What is spatial summation of synaptic communication based on?

Answer 14

Location

Question 15

What is spatial summation?

Answer 15

Multiple presynaptic neurons firing at the same time

Question 16

What is temporal summation of synaptic communication based on?

Answer 16

Timing

Question 17

What is temporal summation?

Answer 17

1 presynaptic neuron firing repeatedly in a short time

Question 18

How many nerves are involved in temporal summation?

Answer 18

1 or 2

Question 19

What happens if 2 nerves in temporal summation fire at different times?

Answer 19

No AP triggered

Question 20

Excitatory synapse
Neurotransmitter:
Effect:
Ion movement:
Outcome

Answer 20

Glutamate
Excitatory
Ion Movement: Na+ enter post-synaptic neuron
Outcome: Depolarisation increases chances of an AP firing

Question 21

Inhibitory Synapse
Neurotransmitter
Effect
Ion movement
Outcome

Answer 21

GABA
Inhibitory
Cl- enter post-synaptic neuron
Hyperpolarisation makes neuron less likely to fire an AP

Question 22

What happens in 2 nerves in temporal summation fire at the same time?

Answer 22

Fire an AP

Question 23

What is an excitatory postsynaptic potential (EPSP)?

Answer 23

Type of postsynaptic potential that makes postsynaptic neuron more likely to fire an AP

Question 24

What is an inhibitory postsynaptic potential (IPSP)?

Answer 24

Makes postsynaptic neuron less likely to generate an AP

Question 25

How to EPSP and ISPS act against each other?

Answer 25

Cancel each other out

Question 26

Two types of receptors

Answer 26

1) Ionotropic 2) Metabotropic

Question 27

What are ionotropic receptors?

Answer 27

Ligand-gated ion channels that open in response to the binding of a neurotransmitter

Question 28

What are metabotropic receptors?

Answer 28

NT activates a G-protein first

Question 29

Examples of IPSP & EPSP in ionotropic receptors

Answer 29

Na+ -> EPSP Cl-/K+ -> IPSP

Question 31

Explain the Knee-Jerk reflex Mention 1) Quadriceps femosis 2) Afferent sensory axon 3) Motor neuron in ventral horn of spinal cord 4) Exiting 5) Efferent motor fibre

Answer 31

1) Reflex hammer hits patellar tendon 2) Stretch receptors in quadriceps femoris muscle are activated 3) AP travels along afferent sensory axon, entering spinal cord through dorsal root 4) Afferent sensory axon synapses onto a motor neuron in ventral horn of spinal cord 5) Motor neuron project axon, exiting spinal cord ventrally 6) Firing along efferent motor fibre results in contraction of quadriceps femoris