Neurotransmission

Question 1

Neural activation

Answer 1

Neurons are always activated by changing permeability and depolarizing neurons until Na+ channels are activated

Question 2

Voltage-gated channels

Answer 2

When potential rises above a threshold then Na+ channels open.

Na+ influx/ depolarization.

K+ channels open.

Na+ channels quickly inactivate

Question 3

Lifecycle of an Action Potential (5 steps)

Answer 3

1. depolarization until a critical threshold
2. (-70) Na+ channels open
3. (-50) K+ channels open
4. Na+ channels close/deactivate
5. K+ channels close (total time ~1ms)

Question 4

Electrical synapse

Answer 4

• Has a gap junction.
• Allows fast, reliable, and direct spread of AP between neurons.
• Large-pore transmembrane.
• Direct apposition between neurons

Question 5

Chemical synapse

Answer 5

• Most common form of synapse in the brain.
• Uses neurotransmitters.
• Allows for a diversity of responses in postsynaptic neurons

Question 6

Postsynaptic receptors (2 classes)

Answer 6

Ionotropic & Metabotropic

Question 7

Ionotropic

Answer 7

• Alter membrane permeability to ions.
• Ligans-gated ion channels.
• Structure of membrane protein determines which ions flow through
  
  • “Lock and Key”

Two types:

1. Glutamate
2. GABA receptors

Question 8

Metabotropic

Answer 8

• “Neuromodulatory”
• Longer-lasting effects.
• Indirectly influences membrane permiability, production of proteins (neurotransmitter receptors), and production of other neurotransmitters
• Important neuromodulators:
  
  • dopamine
  • serotonin
  • norepinephrine.

Question 9

Resting potential

Answer 9

• Around -70 mV.
• Membrane permeability for K+ is much larger than other ions.
• Tendency for K+ to be slightly greater outside cell than needed for balanced charge.
• Result is slightly more negative charge inside cell than outside

Question 10

Refractory period

Answer 10

Absolute: Na+ channels deactivated

Relative: Greater K+ permeability than at rest

Question 11

Myelin

Answer 11

Glial cells that wrap axons to increase speed of AP. Voltage-gated ion channels located at Nodes of Ranvier. Enables saltatory conduction. Responsible for the white in the brain’s white matter

CNS: Oligodendrogytes

PNS: Schwann Cells

Question 12

Synapse

Answer 12

a specialized point of contact between the axon of a neuron (the presynaptic cell) and a target (postsynaptic) cell. Information is tranferred between the presynaptic and postsynaptic cells by the relsease and receipt of biochemical neurotransmitters

Question 13

synaptic bouton (terminal)

Answer 13

usually adjacent to the postsynaptic specialization of the dendrite or cell body of the contacted cell.

Question 14

Synaptic cleft

Answer 14

The small space between a presynaptic and postsynaptic element across which neurotransmitters must diffuse when relseased

Question 15

dendritic spines

Answer 15

A small extension form the surface of a dendrite that receives synapses.

Beneficial chemical isolation and larger surface area (more receptors)

Question 16

Hebbian learning

Answer 16

“cells that fire together wire together”

Question 17

Afferent neurons

Answer 17

Nerve cells that carry information centrally

• toward the CNS

Question 18

Efferent neurons

Answer 18

Nerve cells that carry information peripherally

• away from the CNS

Question 19

Axon

Answer 19

the extension of a neuron that carries the action potential from the nerve cell body to a target

Question 20

Dendrite

Answer 20

The extension of a neuron that receives synaptic input; usually branches near the cell body

Question 21

Important ions

Answer 21

• Potassium (K+)
• Sodium (Na+)
• Calcium (Ca²⁺)