Week 5: Neuronal Communication Flashcards
What is an action potential?
The part of the message potential that occurs inside of the neuron in the format of an electrical impulse.
What is the synapse
when a message turns chemical and passes an extracellular space
What are the three universal properties of neurons?
- they are excitable
- they are conductive by sending electrical signals
-they are secretory (secrete NT in order to communicate)
What are the basic functions of the NS
the ability to sense external stimuli and respond to it, the ability to process information, motor output (response)
What are interneurons
integrators in the processing centre that live inside the CNS
What is membrane potential?
the difference in charge between extracellular and intracellular environment
What is the plasma membrane?
a lipid bilayer that separates internal/external cellular environments, an electrical insulator that controls the movement of substances
what units are used to measure resting membrane potential?
mV
what is resting membrane potential?
-70 mV
What specific ions play a role in ion channels and pumps?
K+, Na+, CA2+, Cl-
What are the 3 ways in which gated channels can open and close?
- Voltage gated
- Chemically/ligand gated
-mechanically gated
what does voltage gated respond to?
a change in charge/ electrical potential
what does chemically/ligand gated respond to?
a change in chemical concentration or a binding of a chemical
what does mechanically gated respond to
a change in mechanical stimuli
What are leakage channels
Unreliable in letting substances in and out, randomly alternate between open and closed
What is the Na/K+ pump
ensures movement of sodium and K across the membrane, continuously working and active, requiring ATP
What does the sodium work in transporting
3 Na+ ions out of the cell
2 K+ ions into the cell
against the concentration gradient
What occurs in the initiation stage
- all or nothing event
-stumuli reaches threshold at -55 mv - neuron receives a message at rest
- action potential initiated
What occurs in depolarisation
- change in charge influx of positive ions into the cell
- voltage increases to +40 v
- voltage gated sodium channels open
-sodium flows into cell and carries positive charge w it - inside of cell becomes more positive
-explosive and fast - stimuli reaches threhold value of -55 mV
What occurs in repolarisation
-returning to the rest state
-potassium channels open
-voltage gated na+ ion channels close
exit of K+ve ions out of the cell
- inside of cell more -ly charged
- restoration of resting membrane potential
What occurs in hyperpolarisation
excess of positive ions exit the cell
What occurs at resting potential
- neuron is at rest
Na and K+ voltage gated channels are closed
Na/K pump maintaining potential at -70 mV - high concentration of Na+ on outside
- high concentration of K+ on inside
What is the role of the myelin in impulse conduction
What is the role of the nodes of ranvier in impulse conduction?
How does the action potential move down a neuron
It spreads as a wave of depolarisation, from one segment of the membrane to the next, down the axon to the axon terminals
What are the two different types of conduction that move an AP down a neuron?
saltatory and continuous
In myelinated neurons, what do action potentials undergo?
saltatory conduction
What is myelin?
a protein lipid complex that coats the axons of our neurons and acts as a protector/insulator by protecting the signal being lost through the membrane by leaking through the membrane into the outside environment
What are nodes of Ranvier?
gaps along the axon that play an important role in signal propagation down the axon, they act as pit stops/charging stations for the AP
What is the purpose of an EMG
to measure the electrical activity in resting and contracting muscles
- forceful contraction produces increased electrical activity
how does an EMG help evaluate muscle weakness/paralysis
- determine if it has occurred from malfunction of muscle or nerves supplying the muscle
What is the difference between surface and intramuscular EMG
SEMG:
- electrodes placed on skin over muscle, non invasive, time efficient, less accurate
IEMG:
-thin wires inserted into muscle, invasive, time-consuming, more accurate
