KIN 4571: Neurophysiology

Action Potentials

sends message within neurons

Synaptic Transmission

send message between neurons

Neurotransmitters

affects excitation or inhibition of neurons

Resting potential is at?

~ -65mv

What is the resting the potential?

the sum of electrical potential from different ions across membrane when the cell is in non-excited state

What is the receptor potential?

the voltage change in response to stimuli

If the voltage reached the threshold, action potentials will be...

generated

What affects the neurotransmitter on the postsynaptic neuron?

IPSP (inhibitory postsynaptic potential "-") and EPSP (excitatory postsynaptic potential "+")

IPSP

Cl- channels open, move further from the threshold

EPSP

Na+ channels open, move closer to the threshold

Action Potentials are...(4 things)

1. Unidirectional: achieve through refractory periods

2. Fast: through (up arrow) diameter and myelin

3. Efficient: only generate at the nodes of Ranvier

4. Simple: All or None principle

The magnitude of the AP...

remains the same

Is the stimulus duration or the amplitude of the AP important?

stimulus duration

Two types of summation:

temporal and spatial

Temporal Summation:

multiple # of inputs per unit of time inter-event intervals are shorter than the duration of the postsynaptic potential

Spatial Summation

multiple neural inputs simutaneously

To reach the threshold, multiple synapse receiving inputs must be:

- close together (spatial summation)

- at close time frame (temporal summation)

The initiation of AP:

electrical impulse causing the propagation of information along the surface of a neuron

Threshold potential

Na+ channels only open when the membrane depolarized to the threshold

Refraction period

the understanding phase

Ion pumps (Na+/K+ ATPase) restore the _____________

homeostasis

Once the receptor potential reaches the threshold

- increase Na+ permeability, which will lead to:

- Na+ channel open

- Na+ flow inside the cell

the membrane potential will then decrease and that's depolarization

At a certain point after depolarization:

- Na+ channel close and K+ channel open

this causes K+ to flow outside

as a result the membrane potential will decrease which is repolarization

At hyperpolarization

- K+ conductance is higher than resting condition

During hyperpolarizaton

Na+/K+ ATPase restore homeostasis

Active current

movement of Na+ ion through ion channel

Passive current

shuffling of change along neuronal process --> change in membrane potential --> generate another AP

The transmission of electrical signal dissipate as ion _____ across the membrane

leak

What are the two types of AP propagation?

continuous conduction (unmyelinated axons) and saltatory conduction (myelinated axons)

Continuous conduction

passive current flow along axon and continuously open Na+ channels

Saltatory conduction

- Na+ channels are accumulated at the gaps of myelinated sheet (nodes of Ranvier)

- AP regenerated at the nodes of Ranvier

Synapses are

electrical signals

Most synapses are

neurotransmitters

Synapses are strengthened with __________ and weakened ________

activity; without

Synapse types are based on

# and connection

Based on #

monosynaptic and polysynaptic

Based on connection

Axodendritic: axons --> dendrites

Axosomatic: axons --> cell bodies

Axoaxonic: axons --> axons

Signal Transduction effects on presynaptic neurons:

usually achieved through Axoaxonic Synapse

Axoaxonic synapses

presynaptic inhibition, presynaptic facilitation

Presynaptic inhibition: increase or decrease neurotransmitter released by presynaptic terminals

decrease

Presynaptic inhibition: increase or decrease effects on postsynaptic neuron

decrease

Presynaptic facilitation: increase or decrease neurotransmitter released by presynaptic terminals

increase

Presynaptic facilitation prolong __________ _________ (not increase amplitude)

action potentials

Long-term potentiation (synaptic enhancment)

increases the amplitude of an EPSP above the "normal" for a give afferent input

Long-term potentiation depends on?

repeated activity

Long-term potentiation is like "presynaptic facilitation" but...

changes are in the postsynaptic neuron

In long-term potentiation the cell is?

hypersensitive

Neuromodulators

indirectly affect excitation/inhibition; alter the input/output properties of neurons

Neuromodulators diffuse _______

release

Neuromodulators use different ___________ - effects and can last longer than other neurotransmitters

receptors

Neuromodulators alter the excitatory or inhibitory properties of neurons by changing membrane characteristics. _________ resting potentials and ________ hyperpolarization.

decrease resting potentials; increase hyperpolarization

Neuropeptides are released with ______________

neurotransmitters

Neurotransmitter: acetylcholine (ACh)

Postsynaptic effect: excitatory

Neurotransmitter: Dopamine

Postsynaptic effect: excitatory (via D1 receptors) and inhibitory (via D2 receptors)

Neurotransmitter: Serotonin

Postsynaptic effect: excitatory or inhibitory

Neurotransmitter: Histamine

Postsynaptic effect: excitatory

Neurotransmitter: Adenosine triphosphate (ATP)

Postsynaptic effect: excitatory/neuromodulatory

Neurotransmitter: Substance P

Postsynaptic effect: excitatory

Neurotransmitter: Metenkephalin

Postsynaptic effect: inhibitory

Neurotransmitter: opioids

Postsynaptic effect: inhibitory

Neurotransmitter: Adrenocorticotropin

Postsynaptic effect: excitatory

Which neurotransmitters are neuromodulators?

ACh, Dopamine, Serotonin, Histamine, and ATP

What are neuropeptides?

peptides released by neurons with neurotransmitters; pain,stress

Which neurotransmitters are neuropeptides?

Substance P, Metenkephalin, Opioids, and Adrenicorticotropic

What involves changes in the presynaptic neuron?

presynaptic inhibition and presynaptic facilitation

What involves changes on the postsynaptic neuron?

Long-term potention

What would limit transmission of information?

Presynaptic inhibition

REVIEW Action Potential

Send message _________ neurons

_________ determine the impact of AP

within neurons

duration determine

REVIEW Synapse

Send message ________ neurons

__________ with activity, ________ without

send message between neurons

strengthen with activity, weaken without

EPSP: postsynaptic facilitation or postsynaptic inhibition

postsynaptic facilitation

IPSP: postsynaptic facilitation or postsynaptic inhibition

postsynaptic inhibiton

Achieved through axoaxonic synapse: presynaptic facilitation or presynaptic inhibition

BOTH

Decrease neurotransmitters released presynaptic neuron: presynaptic facilitation or presynaptic inhibition

presynaptic inhibition

Long term pontentiation: postsynaptic facilitation or postsynaptic inhibition

postsynaptic facilitation

Neuromodulators: postsynaptic facilitation or postsynaptic inhibition

BOTH

Repeated activities: postsynaptic facilitation or postsynaptic inhibition

postsynaptic facilitation