Introduction to Neurobiology

Question 1

Ganglia

Answer 1

clusters of neurons

Question 2

CNS

Answer 2

brain and spinal cord

Question 3

PNS

Answer 3

rest of body

Question 4

Excitable cells

Answer 4

neurons and muscle cells

Question 5

Supporting cells

Answer 5

glia

Question 6

Types of neurons

Answer 6

1. sensory
2. interneurons
3. motor

Question 7

Components of spinal cord

Answer 7

gray matter, white matter, dorsal root, dorsal horn, ventral horn, ventral root

Question 8

neuron anatomy

Answer 8

-dendrites
-cell body
-axon hillock
-axon (output)
-axon termini
-synapse

Question 9

Functions of glia

Answer 9

-structural support and insulation
-nutrient support
-blood-brain barrier
-neurotransmitter uptake
-ion homeostasis

Question 10

Schwann cells and oligodendrocytes

Answer 10

-Schwann = PNS
-oligodendrocytes = CNS
-produce myelin sheaths to insulate neurons

Question 11

Resting membrane potential is a consequence of:

Answer 11

1. concentration differences of ions across membrane
2. differential membrane permeability to ions

Question 12

What is the equilibrium potential?

Answer 12

It is the membrane voltage where the electrical gradient is “strong enough” to attract ions back across the membrane, stopping the net flow of ions driven by the concentration gradient of that ion

Question 13

What is driving force?

Answer 13

The difference between E for that ion and the membrane potential
-Ca2+ = very strong (ECF>ICF)
-Na+ = strong (ECF>ICF)
-K+ = moderate (ICF >ECF)
-Cl- = moderate (ECF>ICF)

Question 14

Sodium-potassium pump

Answer 14

maintains ion concentration gradients, 3 Na+ out and 2 K+ in

Question 15

What happens if sodium-potassium pump is poisoned?

Answer 15

The ionic concentration gradients last for a long time before they start to run down

Question 16

Phase of an Action Potential at one point along an axon

Answer 16

1. Resting condition at one point in an axon
2. Depolarization to threshold opens voltage-gated Na+ channels
3. Na+ rushes in and depolarizes
   4a. Na+ channel inactivation gates close, voltage-gated K+ channels open
   4b. K+ rushes out and repolarization occurs
   4c. Near Vm all voltage-gated channels close
4. 1-2 msec later, Na+ channel inactivation gates reset

Question 17

The speed of conduction in an action potential is determined by:

Answer 17

1. speed of current flow in the axoplasm
2. leakage of ions across the plasma membrane
3. kinetics of channel opening and closings

Question 18

Why are larger dm axons faster than smaller ones?

Answer 18

Large diameter axons have lower resistance and current can propagate more quickly and farther in cytoplasm. Ion channels regenerate current and lower resistance allows for less frequent opening and closing of channels

Question 19

Why are myelin sheaths beneficial?

Answer 19

they reduce ion leakage and insulate axons to make action potentials more efficient (saltatory conduction)

Question 20

Where are ion channels clustered?

Answer 20

at the nodes of Ranvier

Question 21

Why is saltatory conduction fast?

Answer 21

1. Electrical (ionic) current travels quickly through the cytoplasm if there are no leakages
2. Fewer ion channels are opening and closing (less time is required for ion channels to open and close)

Question 22

Types of synapses

Answer 22

1. Electrical
2. Chemical

Question 23

Electrical synapses

Answer 23

mediated by gap junctions

Question 24

Chemical synapses

Answer 24

chemical neurotransmitter released from presynaptic cleft to the postsynaptic cell

Question 25

Important neurotransmitters

Answer 25

1. acetylcholine 2. serotonin 3. dopamine 4. glutamate 5. norepinephrine 6. glycine 7. GABA 8. neuropeptides 9. nitric oxide

Question 26

Excitatory neurotransmitters

Answer 26

acetylcholine, dopamine, glutamate, norepinephrine

Question 27

Inhibitory neurotransmitters

Answer 27

serotonin, norepinephrine, glycine, GABA

Question 28

Neuromuscular junction

Answer 28

1. Action potential arrives at axon terminus 2. Depolarization (must exceed threshold) at terminus opens voltage-gated Ca2+ channels 3. Synaptic vesicles fuse w/ membrane 4. NT is released 5. Triggers action potential in postsynaptic cell (elicit contraction in muscle cell)

Question 29

Ligand-gated channels (ACh)

Answer 29

1. ACh opens Na+ channel on postsynaptic membrane 2. Vm across the postsynaptic membrane depolarizes 3. ACh in the cleft is degraded by acetylcholinesterase 4. Signal is terminated

Question 30

Synapses between neurons

Answer 30

1. Excitatory postsynaptic potential 2. Inhibitory postsynaptic potential

Question 31

EPSP

Answer 31

-depolarize postsynaptic cell -might not be strong enough to single-handedly elicit an action potential

Question 32

IPSP

Answer 32

-hyperpolarize cell

Question 33

Where is the critical area for the "decision" to fire an action potential?

Answer 33

axon hillock

Question 34

Spatial summation

Answer 34

several weak signals from different locations are converted into a single larger one

Question 35

Temporal summation

Answer 35

converts a rapid series of weak pulses from a single source into one large signal

Question 36

Types of chemical synapses

Answer 36

1. Ionotropic receptors 2. Metabotropic receptors

Question 37

Ionotropic receptors

Answer 37

bind a NT and cause a direct change in ion movements

Question 38

Metabotropic receptors

Answer 38

GPCRs ex: cardiac adrenergic receptor in heart cells

Question 39

Process of Synaptic Signal Termination

Answer 39

1. NT is released from presynaptic termini as very brief bursts, so channels in postsynaptic membranes are open for very brief intervals. When channels close, the Vm rapidly returns to the resting Vm that is largely determined by the K+ electrochemical gradient. 2. NT is rapidly removed from synaptic cleft by: a) degradation in synaptic cleft b) diffusion c) being taken up by transporters in membrane's presynaptic cell and repackaged/recycled adjacent glial cells