1 - Neurophysiology

Question 1

CNS Cell Types

Answer 1

Glia, Neurons

Question 2

Parallel Processing

Answer 2

multiple processes occur simultaneously to increase speed, reliability

Question 3

Divergence

Answer 3

one neuron distributes signal to many other neurons

Question 4

Convergence

Answer 4

• Many neurons converge onto one neuron (on average, 7000)
• Summation of input determines if an action potential will occur
• You can see both divergence and convergence in one neural pathway/system

Question 5

Feed Forward/Back Types

Answer 5

1. Feedforward excitation
2. Feedforward inhibition
3. Feedback/Recurrent Excitation
4. Feedback/Recurrent Inhibition

Question 6

Feedforward Excitation

Answer 6

neuron A synapses directly to neuron B, causes AP

Question 7

Feedforward Inhibition

Answer 7

neuron A excites inhibitory interneuron X which inhibits neuron B

Question 8

Feedback/Recurrent Excitation

Answer 8

neuron A excites neuron B which has collateral that feeds back to neuron A to continue/promote excitation

Question 9

Feedback/Recurrent Inhibition

Answer 9

neuron A excites neuron B which has a collateral that feeds-back to interneuron X that inhibits A

Question 10

Rough Endoplasmic Reticulum

Answer 10

• Found only in cell body (not in axon)
• For synthesis of proteins to be packages
• Identified as “Nissl” bodies

Question 11

Golgi Apparatus

Answer 11

Moification and packaging of:

• proteins
• enzymes
• chemical messengers
• vesicles containing neurotransmitters

Question 12

Anterograde Transport

Answer 12

• Microtubules of neuron cytoskeletal components
• Transports materials produced in cell body to end of axon
  
  • Mainly, neurotransmitter vesicles

Question 13

Retrograde Transport

Answer 13

• Microtubules of neuron cytoskeleton
• Transport from axon to cell body
• Removes waste, metabolites
• Use of horseradish peroxidase (dye) shows axon-cell body connectivity

Question 14

How to increase post-synaptic surface area

Answer 14

• Dendritic arborization (branching)
• Dendritic spines/gemmules (projections for sites of contact)

Question 15

Myelination cells in CNS

Answer 15

Oligodendrocytes

Question 16

Myelination cells in PNS

Answer 16

Schwann cells

Question 17

Myelination purpose

Answer 17

• Insulation for saltatory conduction
• Insulation between axons so they don’t influence each other

Question 18

Ion channel location in

• Myelinated axon
• Unmelinated axon

Answer 18

Myelinated: concentrated at unmyelinated Nodes of Ranvier

Unmyelinated: distributed evenly along length of axon

Question 19

Initial Segment

Answer 19

• FIrst part of axon, at/below axon hillock
• Transition zone containing voltage-gated Na+ channels
• Where summation of inputs from all presynaptic cells determines whether an AP will result or not

Question 20

Answer 20

Multipolar neuron

• Most common CNS neuron
• All peripheral motor neurons

A) Dendrites

B) Soma

C) Axon

Question 21

Answer 21

Pseudounipolar neuron

• Most common peripheral sensory neuron
• Cell body sends off one axon and one dendrite that fuse together and split to make one long process that functions as an axon at both branch ends
  
  • One branch projets to periphery, one to CNS

A) Peripheral process

B) Soma

C) Central process

Question 22

Answer 22

Bipolar neuron

• One arborized dendrite, one arborized axon
• ALWAYS special sensory neurons

A) Peripheral process

B) Soma

C) Central process

Question 23

Answer 23

Unipolar Neurons

• No dendrite
• Not usually in vertebrates

A) Soma

B) Axon

Question 24

4 types of glial cells

Answer 24

1. Astrocytes
2. Oligodendrocytes
3. Microglia
4. Ependymal cells

Question 25

Glial Cell Functions

Answer 25

\*\*Basically provide a favorable environment for neurons 1. Development 2. Neuroplasticity (especially after a lesion to the CNS, it's involved in clearing debris) 3. In PNS, involved in promoting regeneration of an axon 4. Support neuron function by controlling movement of nutrients, removing metabolites, maintain NT balances in synaptic clefts, insulating axons, and isolating neurons 5. After neural injury, astrocytes, oligodendroglia and microglia all proliferate and form glial scar tissue, isolating the damaged tissue but also inhibiting neural repair.

Question 26

Astrocytes

Answer 26

* Most numerous glia cells * Tons of functions of support, repair, and scaffolding * Two types: * Fibrous: in white matter (axons) * Protoplasmic: in gray matter (Cell bodies)

Question 27

Oligodendrocytes

Answer 27

* Type of glial cell * More in white matter than gray matter * Responsible for myelination of CNS axons * High electrical resistance, low conductivity * Modulate rate of signal propagation * One oligodendrocyte can myelinate up to 30 axons

Question 28

Ependymal Cells

Answer 28

* Glial cells * Produce, circulate CSF * Helps form choroid plexus * Include tanycytes (modified ependymal cells in 3rd ventricle)

Question 29

Microglia

Answer 29

* Glial cells * Macrophages in CNS * Remove foreign pathogens and cellular debris * Participate in inflammatory and degenerative reactions

Question 30

Resting Membrane Potential

Answer 30

-70 mV

Question 31

Threshold Membrane Potential

Answer 31

-55 mV

Question 32

Forces maintaining resting state membrane potential

Answer 32

1. Passive non-gated ion channels 2. Passive electrical forces 3. Na/K pump (requires ATP)

Question 33

Chemical Synapse

Answer 33

At presynaptic membrane, AP opens voltage-gated calcium (Ca) channels, permitting influx of Ca++ ions into axon terminal which triggers fusion of synaptic vesicles with the presynaptic membrane. NTs are released into synaptic cleft via exocytosis. Can be: * Ionotropic (NT, direct/rapid effect) * Metabotropic (NM, G-protein coupled receptor, slow/indirect effect)

Question 34

Major classes of neurotransmitters

Answer 34

* Amino acids * Small, fast-acting * Excitatory or inhibitory * Amines * Small neuromodulators (G-protein receptors) * Excitatory or inhibotory based on receptor it binds to * Peptides * Large neuromodulators (G-protein) * Excitatory or inhibotory based on receptor it binds to

Question 35

Amino Acid

Answer 35

* Small fast-acting neurotransmitters * **Excitatory**: glutamate and aspartate * **Inhibitory**: GABA (gamma-amino-butyric acid) and glycine

Question 36

Amines

Answer 36

* Small molecules that are neuromodulators (G-protein coupled receptor) * Can be either excitatory or inhibitory, depending on the receptor it binds to. * **Examples** include acetylcholine, the catecholamines (dopamine, epinephrine, norepinephrine), serotonin, and histamine.

Question 37

Peptides

Answer 37

* Large neuromodulators that bind to G-protein coupled receptors * Can be either excitatory or inhibitory, depending on the receptor. * **Examples** include dynorphin, beta-endorphin, enkephalin and substance P.