Synaptic Transmission

Question 1

dendrites

Answer 1

tapered processes arising from the cell body that greatly increases the receptive surface. The membranes contain receptors for transmitters and voltage gated ion channels that can amplify the graded synaptic signal. primary areas for receiving and integrating complex information from thousands of synapses.

Question 2

cell soma

Answer 2

surrounds nucleus and contains the ER, golgi, etc. performs house keeping functions such as protein synthesis, degradation and processing.

Question 3

axon

Answer 3

single thin process arising from the cell body at the axon hillock. transmits all or none action potentials to the terminals after integrating transmitter mediated bioelectrical changes received in the dendrites and cell body

Question 4

presynaptic terminals

Answer 4

specialized structures that convert electrical signals propagated down the axon (action potentials) into chemical signals (neurotransmitter).

Question 5

synapse

Answer 5

point of contact between pre and post synaptic neuron/target cell.

Question 6

axoplasm

Answer 6

contains parallel arrays of microtubules and neurofilaments that provide structural stability and a means to transport materials back and forth between the cell body and presynaptic terminals.

Question 7

kinesin

Answer 7

microtubule motor that mediates fast antegrograde transport of mitochondria and vesicles from soma to terminals.

Question 8

dynein

Answer 8

mediates fast retrograde transport of degraded vesicular membranes and absorbed toxins/viruses/growth factors from terminal to soma

Question 9

electrical synapses

Answer 9

provide speed and synchrony. how electrical response in one cell is transmitted to another cell. fast and bidirectional. allows direct passive flow of electrotonic current between cells via gap junctions

Question 10

gap junctions

Answer 10

compromised of intramembrane channel proteins called connexions. critical for synchronous electrical coupling in visceral smooth muscle and cardiac muscle.

Question 11

criteria for chemical neurotransmitters

Answer 11

present in presynaptic terminal, released in a voltage and calcium dependent manner, specific receptors present in the post synaptic target cell, means to inactivate the transmitter

Question 12

steps in synaptic transmission

Answer 12

transmitter molecules are synthesized and packaged in vesicles, action potential arrives at the presynaptic terminal, depolarization of terminal opens voltage gated calcium channels, increased calcium in terminals trigger vesicle fusion, transmitter diffuses across cleft and binds to postsynaptic receptors, postsynaptic response occurs, transmitter molecules are cleared/inactivated by enzymatic degradation, uptake or diffusion

Question 13

active zones

Answer 13

a specialized site on the presynaptic terminal where vesicles that are docked to be preferentially released in response to invasion of the terminal by an action potential, activation of voltage sensitive calcium channels, and influx of calcium.

Question 14

functional magnetic resonance imaging (fMRI)

Answer 14

measures changes in regional blood flow associated with changes in local cerebral glucose metabolism.

Question 15

exocytosis

Answer 15

process of neurotransmitter release from the presynaptic terminal.

Question 16

endocytosis

Answer 16

prevents out of control enlargement of the presynaptic membrane. how vesicle membrane that has fused to the presynaptic membrane is recycled.

Question 17

botulinum toxin

Answer 17

causes muscle weakness by cleaving SNAP-25 (A&E) or synaptobrevin (B) proteins in the presynaptic terminal of alpha motor neurons.

Question 18

ionotropic receptor

Answer 18

contain ion channel as part of their structure and transmitter binding triggers a rapid response.

ligand binding site and ion channel

Question 19

metabotropic receptor

Answer 19

commonly linked to G proteins that transduce a slower biochemical signal.

ligand binding site linked to G protein

Question 20

nicotinic AChR

Answer 20

ligand gated channel on the post synaptic membrane. end result is muscle contraction in skeletal muscle

example of ionotropic receptor

Question 21

muscarinic AChR

Answer 21

coupled to a heterotrimeric G protein. end result is decreased heart rate in cardiac muscle.

example of metabotropic receptor

Question 22

How are postsynaptic potentials (PSPs) produced?

Answer 22

conductance changes due to ion channel openings (and sometimes closings) lead to ionic current flow through the channels that in turn lead to changes in the membrane potential.

Question 23

Excitatory PSP (EPSPs)

Answer 23

increase the probability that an action potential will be triggered

Question 24

Inhibitory PSP (IPSPs)

Answer 24

decrease probability that an action potential will be triggered

Question 25

glutamate

Answer 25

major excitatory neurotransmitter and binds to ionotropic and metabotropic receptors. binding of glutamate to specific ligand gated ion channels in the target cell produces both fast and slow depolarizing responses (EPSP) because distinct receptors are activated.

Question 26

GABA

Answer 26

major inhibitory transmitter and binds to ionotropic and metabotropic receptors. binding of GABA to specific ligand gated ion channels in the target cell produces hyperpolarizing responses called IPSP.

Question 27

cable theory takes into account

Answer 27

membrane capacitance, membrane resistance, and longitudinal cytoplasmic resistance between different parts of the neuron

Question 28

decremental conduction

Answer 28

large amount of potential is lost by leakage through the membrane before EPSP can reach the cell soma

occurs because dendrites are long and their membranes are thin and leaky to electric current.

Question 29

What determines the probability that an action potential will be generated?

Answer 29

temporal and spatial summation

Question 30

process of temporal stimulation

Answer 30

two action potentials on one synapse. when the membrane has a longer time constant, some of the depolarization from the first EPSP is still present when the second occurs, and the individual depolarizations can summate.

Question 31

process of spatial summation

Answer 31

two action potential on two different synapses. when the cell membrane has a longer space constant, the EPSP from synapse 1 is able to propagate further along the membrane and can summate with the EPSP from synapse 2, resulting in more depolarization to propagate to the soma and axon hillock.