The synapse

Question 1

What is the function of the dendrites?

Answer 1

Receive inputs from other neurones and convey graded electrical signals passively to the soma

Question 2

What is the function of the soma (cell body)?

Answer 2

Synthetic and metabolic centre. Contains the nucleus , ribosomes, mitochondria and endoplasmic reticulum. Intergrates incoming signals that are conducted passively to the axon hillock

Question 3

What is the function of axon hillock and initial segment?

Answer 3

Site of initation of the ‘all or none’ action potential

Question 4

What is the function of the axon?

Answer 4

Conducts output signals as action potentials to other neuroes (or other cells). Mediates transport of materials between the soma and presynaptic terminal and vice versa

Question 5

What is the function of the synapse?

Answer 5

A point of chemical communication between neurones

Question 6

What holds the pre- and post- synaptic membranes together?

Answer 6

A matrix of fibrous extracellular protein within the cleft

Question 7

What does vesicles in the presynaptic terminal store ?

Answer 7

Neurotransmitter

Question 8

What is the gray’s type 1 synapse?

Answer 8

Asymmetrical synapses in which the membrane differentiation on the postsynaptic side is thicker than the presynaptic side (usually excitatory in function)

Question 9

What is the gray’s type 2 synapse?

Answer 9

Symmetrical synapses in which the membrane differentiations are of similar thickness (usually inhibitory in function)

Question 10

What is a axodendritic synapse?

Answer 10

Axons joins at post synaptic dendrite

Question 11

What is a axosomatic synapse?

Answer 11

Axon joins at the soma

Question 12

What is a axoaxonic synapse?

Answer 12

Axon meets at axon

Question 13

what two categories of synapses are there?

Answer 13

• excitatory

- inhibitory

Question 14

What causes the excitatory postsynaptic potential?

Answer 14

Glutamate activates postsynaptic , cation selective, ionotropic, glutamate receptors generating a local, graded , excitatory (depolarising) response

Question 15

What causes the inhibitory postsynaptic potential?

Answer 15

GABA, or glycine, activates postsynaptic, anion selective, ionotropic, GABAA, or glycine, receptors generating a local, graded, inhibitory (hyperpolarizing) response

Question 16

What is spatial summation?

Answer 16

Many inputs converge upon a neurone to determine its output

Question 17

What is temporal summation ?

Answer 17

A single input may modulate output by variation in action potential frequency of that input

Question 18

What are released from synaptic vesicles ?

Answer 18

Amino acids and amines

Question 19

What are released from secretory vesicles?

Answer 19

Peptides

Question 20

What can activate ionotropic ligand-gated ion channels (LGiCs)?

Answer 20

• Glutamate
• GABA
• glycine
• acetylcholine
• 5-HT

Question 21

What is the 9 steps of neurochemical transmission?

Answer 21

1) Upatke of precursor
2) Synthesis of transmitter
3) Storage of transmitter
4) Depolarization by action potential
5) Ca2+ influx through voltage-activated Ca2+ channels
6) Ca2+ induced release of transmitter (exocytosis)
7) Receptor activation
8) Enzyme-mediated inactivation of transmitter OR
9) Reuptake of transmitter

Question 22

How are GABA and amines synthesised?

Answer 22

Must be synthesised by the neurones that release them,requiring specific enzymes

Question 23

How are the enzymes synthesised in the cell body transported to the presynaptic terminal?

Answer 23

Axoplasmic transport

Question 24

How are synaptic vesicles made?

Answer 24

• precursor molecule
• synthetic enzymes
• neurotransmitter molecule
• transporter protein
• synpatic vesicle made

Question 25

How are neurotransmitters synthesised?

Answer 25

1) Synthesis of precursor peptide by ribosomes associated with the rough endoplasmic reticulum (ER) 2) Cleavage of precursor peptide in Golgi apparatus yielding active neurotransmitter 3) Secretory granules bud off from the Golgi apparatus 4) Secretory granules are transported to the presynaptic terminal by fast axoplasmic transport

Question 26

What are the key features of exocytosis : transmitter release?

Answer 26

- Synaptic vesicles ready for rapid release are held in apposition to the presynaptic membrane in a docking complex (SNARE complex) - Depolarization of the presynaptic membrane (arrival of the action potential) opens voltage-activated Ca2+ channels, causing a rise in the concentration of Ca2+ in the vicinity of the docked vesicles - Ca2+ binds to synaptotagmin-1 in the vesicle membrane causing the vesicle to fuse with the presynaptic membrane - Neurotransmitter diffuses from vesicles into the synaptic cleft - Membrane added to the presynaptic terminal is retrieved by endocytosis

Question 27

What are neurotransmitter dependant on?

Answer 27

Calcium

Question 28

What do ligand-gated channels consist of?

Answer 28

Consist of separate glycoprotein subunits that form a central , ion conducting channel

Question 29

What are the 3 states of ligand-gated channels?

Answer 29

1) Unoccupied and close 2) Occupied and close 3) Occupied and open

Question 30

What are G-protein coupled receptors made of?

Answer 30

Receptor G-protein Effecter

Question 31

Is signalling faster via G-proteins or ligand-gated channels?

Answer 31

Ligand-gated channels