Topic 2 - Neural Anatomy & Physiology

Question 1

Axon Hillock

Answer 1

Trigger zone

High degree of voltage gated channels here

All electrical signals converge here and once they reach threshold the potential will propogate down axon

Question 2

Ranvier nodes

Answer 2

Spaces b/w myelin sheaths

High degree of voltage gated channels

Question 3

Terminal branches

Answer 3

OUTPUT

Presynaptic membrane

Release neurotransmitters to communicate with other cells

Question 4

Dendrites

Answer 4

RECEIVE INFO

post synaptic membrane

Question 5

Bipolar neuron

Answer 5

Cell body in middle

Dendritic pole on one end, axonal pole on the other

Bipolar cells in the retina

Question 6

Pseudo-unipolar neuron

Answer 6

Cell body off to side

Dorsal root ganglion

Peripheral sensory neurons (PNS) to spinal cord

Question 7

4 mulitpolar neurons

Answer 7

Alpha motoneuron

Pyramidal neuron

Basket cell

Interneurons

Question 8

2 types of channels important for APs

Answer 8

1. Voltage-gated ion channels
   - open in response to change in membrane potential
2. Ligand- or neurotransmitter-gates channels
   - open in response to interaction with specific chemicals (ex. Synapses b/w neurons)

Question 9

4 phases of the AP

Answer 9

1. Resting potential -70 mV (-ve inside (Cl-), +ve outside (Na+))
2. Depolarization Na+ enters so that inside becomes less -ve
3. Re- and hyperpolarization (K+ leaves the cell making it more -ve)
4. Re-establishment of resting potential (Na+/K+ pump bring some K+ back in and pushes Na+ out)

Question 10

All or none principle

Answer 10

When one Na+ channel opens it fauses a riplling effect

Question 11

Whats is the Refractory Period and what does it allow

Answer 11

Innactivation of Na+ channels once they’ve been opened

Hyperpolarization from K+ out (bc this bring cell furthher from firing potential of -70 mV)

Allows for one direction flow only

Question 12

What does Ca2+ endtering the cell allow for?

Answer 12

Allows for vesicles with neurotransmitters to leave the cell

Question 13

Temporal summation

Answer 13

Multiple EPSPs that occur in wuick sequence at same location, one neuron

Question 14

Sparial summation

Answer 14

EPSPs that occur at different neurons/locations

Question 15

Postsynaptic inhibition

Answer 15

The hyperpolarization of postsynaptic membrane (dendrites)
- this inhibits bc incoming signals will not be able to meet threshold for firing

Caused by cl- entering dendrites of post synaptic cell
-ve ion will hyperpolarze the cell (make it more -ve)

Question 16

Presynaptic inhibition

Answer 16

Decreased neurotransmitter release from inout neuron

Caused by cl- entering presynsptic end of input neuron meaning less Ca2+ enters therefore reducing neurotransmitter release for next neuron
- w/o enough neurotransmitter released, Na+ cannot enter next cell so it cannot depolarizr

Question 17

If neurotransmitters are excitatory, do they cause depolarization or hyperpolarization?

Answer 17

Depolarization

- they start the AP!

Question 18

What is more abundant at the axon hillock, IPSPs or EPSPs?

Answer 18

IPSPs

Question 19

Renshaw cell

Answer 19

Inhibitory cell — a collateral offshoot of alphamotorneurons

Sends inhibitory signals to other cell

Helps with signal-to-noise ratio by helping to activate the alpha motorneurons we actually want

Question 20

Divergence

Answer 20

One cell providing input to many other cells

Question 21

Convergence

Answer 21

Manys cells providing input to one cell

Question 22

Disinhibition

Answer 22

When you send an inhibitory signal to an inhibitory cell (like a renshaw cell)

Question 23

Descending inhibition

Answer 23

Prevents protective measures from taking place bc if so, muscle would inly extend and not be able to continue with the actual intended movement which is flexion

Disinhibition
- sends inhibitory signals to the interneurons that would normally send inhibiting signsls to the alpha motorneuron

Question 24

Membrane resistance and things that influence it

⬆️ permeability = ⬇️ mem resistance

Answer 24

The ability of the membrane to resust things…

⬆️ diameter of axon & dendrites = ⬇️ mem residtsnce bc there are ⬆️ channels so ⬆️ membrane permeability

⬇️ diameter of cell body = ⬇️ mem resistance bc it less synaptic output is needed to cause AP

Question 25

For a specific neuron, is the amplitude and duration of the AP the same?

Answer 25

Yes

Ex. Hard vs soft touch yields same amplitude

Question 26

Does ⬆️er frequency leas to ⬆️er or ⬇️er stimulus intensity

Answer 26

⬆️er frequency = ⬆️er stimulus intensity