Nervous system - Neurons

Question 1

Action potential

Answer 1

Localized area of depolorization of the plasma membrane that travels in a wave-like manner along the axon

Acts as information and takes the form of electrochemical impulses

Question 2

Soma

Answer 2

Central cell body of a neuron; contains nucleus

Question 3

Axon

Answer 3

Middle slender part of the neuron; only one axon per neuron

Question 4

Dendrites

Answer 4

Slender projections of the neuron; many dendrites per neuron

Question 5

Synaptic knob

Answer 5

is a tiny bulge at the end of the terminal branch of a presynaptic neuron

Question 6

Synaptic cleft

Answer 6

Small gap where chemical messengers are released and travelled across

Question 7

Resting membrane potential

Answer 7

-70 mV

Question 8

Sodium phosphate ATPase pump

Answer 8

3 Na+ ions out and 2 K+ ions in the cell:

1) Explains why resting membrane potential is negative
2) High sodium outside and high potassium inside

Question 9

Leak channels

Answer 9

Channels open all the time that allow ions to flow based on their gradient:
1) Few sodium and many potassium leak channels lead to the negative membrane potential

Question 10

Depolarization

Answer 10

Change in the membrane potential from resting potential to less negative or positive potential

Question 11

Repolarization

Answer 11

Returning of membrane potential to normal potential

1) Voltage-gated sodium channels close
2) Voltage-gated potassium channels open
3) Na/K ATPase continues to function

Question 12

Polarized

Answer 12

Describes neurons; Neurons negative on inside and positive on outside

Question 13

Threshold potential

Answer 13

-50mV, potential needed to reach for voltage-gated sodium channels to open; reaches this potential due to Na+ ions from previous depolarization

Question 14

Voltage-gated sodium channels

Answer 14

Channels that utilize passive transport and regulated by the potential; sodium channels open at -50mV

Question 15

Voltage-gated potassium channels

Answer 15

Channels that utilize passive transport and regulated by the potential; potassium channels open at +35mV

Question 16

Saltatory Conduction

Answer 16

Rapid jumping conduction in myelinated axons through nodes of ranvier

Question 17

Myelin

Answer 17

Insulating sheath that wraps around axons; forces the action potential to jump from node to node

Question 18

Schwann cells

Answer 18

Type of glial cells that make up the myelin sheath

Question 19

Nodes of ranvier

Answer 19

Gaps in the myelin sheath where channels are found and membrane depolarization occurs

Question 20

Glial cells

Answer 20

Specialized, non-neuronal cells that typically provide structure and metabolic support to neurons (Schwann cells)

Question 21

Equilibrium potential

Answer 21

Membrane potential at which the driving force of the gradient does not exist due to the repulsion or attraction of charges:

1) Na+ = +50mV; sodium cannot flow in the cell
2) K+ = -90mV; potassium cannot flow out of cell due to attraction

Question 22

Nernst equation

Answer 22

Equation to calculate equilibrium potential using concentration of ions

Question 23

Refractory period (two types)

Answer 23

Non-responsive to membrane depolarization for a short time period after one action potential has passed

1) Absolute refractory period: Voltage Na+ inactivated after depolarization (rather than closed)
2) Relative refractory period: Neuron can be induced to transmit an action potential, but the depolarization required is greater than normal because the membrane is hyperpolarized (membrane potential more negative than the resting potential at -90mV)

Question 24

Summation

Answer 24

Postsynaptic neuron has many different neurons synapsed with it; decision to fire action potential depends on the summation of both excitatory and inhibitory neurotransmitters

Question 25

Neuromuscular junction

Answer 25

Chemical synapse between neurons and skeletal muscle; neurotransmitter released is acetylcholine

Question 26

Acetylcholinesterase

Answer 26

Degrades acetycholine in the synaptic cleft

Question 27

Synapse

Answer 27

Junction between axon terminus of a neuron and other neurons (soma, dendrite or axon) or an organ

Question 28

Electrical synapse

Answer 28

Gap junctions; occur when action potential is spread directly from one cell to another

Question 29

Chemical synapse (and steps)

Answer 29

Found at the end of axons where they meet their target; an action potential is converted into chemical signal

1) Action potential reaches synaptic knob
2) Depolarization of presynaptic membrane opens voltage-gated calcium channels
3) Calcium influx into presynaptic cell causes exocytosis of neurotransmitter stored in secretory vesicles
4) Neurotransmitter molecuels diffuse across the narrow synaptic cleft
5) Neurotrasnmitter binds to ligand-gated ion channels
6) Opening of these ion channels alters membrane polarization; if reaches threshold potential action potential is initiated
7) Neurotransmitter degraded