Unit 2 Exam study guide

What is axonal transport?

transporting stuff from the soma to the knob or vice versa

What is the difference between fast and slow axonal transport?

slow depends on diffusion fast uses motor proteins, Motor proteins require calcium, requires ATP

What is a synapse?

a Junction between a neuron and… another neuron, a muscle, a gland

What are the parts of a synapse?

presynaptic: before synaptic cleft Synaptic Knob, releases a neurotransmitter Postsynaptic: After synaptic Cleft Membrane with neurotransmitter receptor.

What is the difference between electrical and chemical synapses?

One synapse has no synaptic cleft and uses gap junctions and is bidirectional while the other uses neurotransmitters and travels in one direction.

Which synapses is most common Electrical or Chemical

Chemical

Fxn of a satellite cell

Surround ganglia, No clear function

Fxn of Schwann Cell

create myelin sheath Can repair a partial damaged, Multiple cells for 1 axon. Like a cinnamon roll

Fxn of Astrocytes

creates the BBB- blood brain barrier, provides nourishment for neurons
Glycogen + Lactate
Can create scar-tissue

Uptake: Water, Potassium, Neurotransmitters

What is uptake?

type of absorption, Like a sponge

Fxn of Microglia

Macrophage, immunity, Digest Dead Neurons

Fxn of Ependymal Cells

in the root of every ventricle, Secrete cerebral spinal fluid

Fxn of Oligodendrocytes

Create myelin Sheath 1 cell for multiple axons, Can’t repair damaged axon

What is the Membrane Potential?

adding all charges in the ICF and surrounding ECF.

What is the RMP i.e. Resting Membrane Potential

adding all charges in the ICF and surrounding ECF. WHEN THE CELL ISN’T STIMULATED

What are the 2 main influencers of the membrane potential?

Concentration Gradient and Membrane Permeability

What is special about the Concentration Gradient in the Membrane potential?

it never changes

What is special about membrane permeability in the Membrane potential?

Ions can’t pass through the membrane without a channel

Which ion is most responsible for a normal RMP?

Potassium

Why is Potassium most responsible for a normal RMP?

most common leak channel

What can change the membrane potential?

when ion channels open or close

How does a membrane potential affect the concentration gradient of any ion involved?

by making ions move down their concentration gradient

Which ions have a higher concentration in the ECF?

Chlorine Sodium

What is the Nernst equation?

Predicts the effect of 1 ion on membrane potential

What does depolarizing do to the membrane potential?

it is stimulating, makes membrane more positive

What does Hyperpolarizing do to the membrane potential?

it is inhibiting, makes membrane more negative than RMP

How does resistance (R) affect the flow of ions?

opposes flow it is inversely proportional

What are the 2 main factors for resistance to ion flow? (R_m & R_i)

Membrane Resistance and Cytoplasm

What is a Graded Potential?

Neurons, Electrical Signals. Starts the whole thing

What is an Action Potential?

Neurons, Electrical Signals

Where does a Graded potential occur?

start in dendrites or the soma end in the axon hillock

Where does an Action Potential occur?

start in the axon hillock (trigger zone) end at the synaptic knob

What types of gated channels are involved in a Graded Potential?

Mechanical, chemical, voltage

What types of gated channels are involved in a Action Potential?

Voltage only

Which ions are involved with a Graded Potential?

Sodium, Potassium, Calcium

Which ions are involved with a Action Potential?

Sodium, Potassium

Is a graded potential hyperpolarizing, depolarizing, or both?

Depolarizing or Hyperpolarizing

Is an action potential hyperpolarizing, depolarizing, or both?

Depolarizing only

How is the strength of the signal action potential?

it doesn’t lose strength

How is the strength of the signal graded potential?

Loses strength as it travels

Does an action potential require a threshold?

Yes

Does a graded potential require a threshold?

no

What is the RMP on a neuron in millivolts?

-70mV

Can a graded potential be summed? (added to create a larger potential)

Yes

Can an action potential be summed? (added to create a larger potential)

No

Does an Action Potential follow the all-or-nothing phenomenon?

Yes

Does an Graded Potential follow the all-or-nothing phenomenon?

No

Does a graded Potential have a refractory period?

No

Does an action Potential have a refractory period?

Yes

What is the threshold for a signal to be created in a neuron? in millivolts?

-55mV

What is subthreshold? What does that mean?

Below threshold; doesn’t create signal

What is suprathreshold? What does that mean?

above threshold; Creates a signal

What are the channels of an Action Potential?

Sodium Activation, Sodium Inactivation, Potassium Voltage

which ion gates are open during RMP?

sodium activation: closed
sodium inactivation: open
potassium voltage: closed

Which ion gates are open at threshold?

sodium activation: open
sodium inactivation: open
potassium voltage: closed

what happens once the threshold is met?

action potential is created every time

What is the maximum depolarization (in mV) of a neuron?

+30mV

which gates open or close at maximum depolarization?

sodium activation: open
sodium inactivation: closed
potassium voltage: open

What happens once maximum depolarization is met?

repolarization happens

What gates are open or closed during repolarization?

sodium activation: open
sodium inactivation: closed
potassium voltage: open

When does hyperpolarization happen? (in mV)

-90mV

What gates are open or closed when the membrane hyperpolarizes?

sodium activation: closed
sodium inactivation: open
potassium voltage: closed

What is a refractory period?

the short time after an Action Potential

What is an absolute refractory period?

absolute NO new signal can be made at this time

What causes absolute refractory period?

Sodium channels are already open so they can’t be more open

What is a relative refractory period?

when the NA voltage gates are starting to reset.

what causes it to be a relative refractory period?

if a stimulus is strong enough it is possible to create a signal

what would happen if the action potential started at mid-axon instead of at the axon hillock?

the action potential may go backwards to the soma

How will a thicker Axon diameter influence the speed of a nerve impulse conduction?

its faster

How will a thinner Axon diameter influence the speed of a nerve impulse conduction?

its slower

How will a myelinated Axon influence the speed of a nerve impulse conduction?

its faster

How will a non-myelinated Axon influence the speed of a nerve impulse conduction?

its slower

How will the Axon length influence the speed of a nerve impulse conduction?

it doesn’t matter

What is saltatory conduction?

appearance of an Action Potential jumping from node to node

What happens to the action potential conductance in demyelinating diseases?

the signal loses strength, makes action potential a graded potential

What is multiple sclerosis?

its an autoimmune disease and its incurable

what is Guillain-Barre?

demyelinating disease gained by a virus and its curable

What is Hypokalemia?

Low ECF K. Means the RMP becomes more negative, this leads to flaccid paralysis

What is normokalemia?

Normal ECF K, RMP is at -70mV

What is Hyperkalemia?

High ECF K, RMP becomes more positive, leads to spastic paralysis i.e. unable to relax

1st Step of neurotransmitter release and termination

action potential travels down an axon

2nd step of neurotransmitter release and termination

at synaptic knob activates 2 voltage gates

3rd step of neurotransmitter release and termination

neurotransmitter releases

Which voltage gates open at the synaptic knob and why?

Sodium to depolarize the membrane and Calcium for exocytosis

What is the name of the process for neurotransmitter release?

Exocytosis

what are the 3 steps the body does to get rid of a neurotransmitter (in the CNS)

action potential stops, calcium voltage gate closes, exocytosis stops

In the CNS, what are the three fates of the neurotransmitter once it isn’t being released?

It diffuses out, Enzymes break it down, uptake by astrocyte, goes back into synaptic knob by endocytosis

What determines the amount of neurotransmitters released?

the Frequency of Action Potential

Which ion(s) have a higher concentration in the ICF?

Potassium

What does the GHK equation calculate?

predicts effect of all ions on the membrane potential