7.1 Flashcards
(20 cards)
What are action potentials?
Electrical impulses
Intra-neuron
Rapid change in membrane potential
What are synapses?
Chemical signals
Inter-neurons
Release and binding of neurotransmitters
How do neurons talk?
Excitable: respond to changes in environment
Conductive: send electrical signals
Secretory: secrete neurotransmitters in order to communicate
What is membrane potential?
The difference in charge between extracellular and intracellular environment
What is the resting membrane potential?
-70mV
What do ions channels and pumps facilitate?
Enters and exit of ions
What are the three gated ion channels?
Voltage: respond to changes in charge
Chemically/ligand: respond to change in chemical concentration
Mechanically: respond to mechanical stimuli
What is a leakage ion channel?
Always open or randomly alternate between open and closed
Describe the Na+ / K+ pump
Continuously working
Active (ATP)
Transports 3Na+ ions out of the cell and 2k+ ions into the cell against the concentration gradient.
What causes membrane potential?
Positive ions outside the cell = greater positive charger
Negatively charged proteins = greater negative charge
What are the 4 phases of action potential?
Initiation
Depolarisation
Repolaristation
Hyperpolarisation
What occurs in initiation?
All or nothing event
Stimulus reaches threshold at -55mV
What occurs during depolarisaition?
Influx of positive ions into the cell
Voltage increases to +40mV
What occurs during repolarisation?
Exit of positive ions outside of the cell
Restoration of resting membrane potential
What occurs during hyperpolarisation?
Excess of positive ions exit the cell Restoration
What does resting potential look like?
Neurons at rest
Na+ and K+ voltage gated channels are closed
Na+/K+ pump maintaining potential at -70mV
High concentration of Na+ on the outside
High concentration of K+ on the inside
What does depolarisation look like?
Stimulus reaches threshold value of -55MV
Voltage gated Na+ ion channels open
Na+ ions flood into the cell axon
Inside the cell becomes more positive
Continues until the membrane potential reaches +40mV
Explosive and fast
What does repolarization and hyperpolarisation look like?
Returning to the “rest state”
Voltage gated Na+ ion channels close
Voltage gated K+ channels open
K+ ions exit the cell
The inside of the cell becomes more negatively charged
Excess K+ pumped out of the cell
Some K+ re-enters back
Resting potential is restored
What does the action potential look like along the axon?
Spreads a wave of depolarisation from one segment of membrane to the next down the axon
Chain reaction
Saltatory and continuous conduction
What is saltatory conduction?
Electrical impulse
Insulated by myelin
Propels via nodes of ranvier
Fast
