Chp 3.1: Action Potentials Flashcards
Neurons
The basic building blocks of the nervous system
What are the 3 (+1) main parts of a neutron?
a cell body, dendrites, and an axon (and axon terminal)
Soma (Cell Body) (3)
- Contains structures needed to keep the neuron alive
- its nucleus contains the genetic information that determines how the neuron develops and functions
- Processes and integrates information
Dendrites
-Receives information
Axon (use of it)
-Conducts electrical impulses away from the cell body to other neurons, muscles, or glands
Simplified: Carries the information along long distances from one part of the neuron to another
What are the functions of neurons? (2) And what are the use? (1)
- Generate electricity
- Release chemicals
Allows neurons communicate with other neurons, as well as muscles and glands
Blood-Brain Barrier
Prevents many substances, including a wide range of toxins, from entering the brain
Resting Potential
-Internal difference of around -70 millivolts (inside is 70mv less than positive than outside)
- Outside the cell: high concentration of sodium ions (Na+)
- Inside in cell: more potassium ions (K+) /protein (A-)
=creates a chemical gradient (cell membrane)
-at rest there are more positively charged ions outside the cell relative to the inside
=results in difference in charge across the the membrane
=electrical gradient
=electrochemical gradient
-Neuron is at a state of polarisation
What happens when neuron is stimulated? (2)
- A flow of ions in and out of the cell membrane reverses the electrical charge of the resting potential
- This produces an action potential (nerve impulse)
Action potential
-A sudden reversal in the neuron’s membrane voltage
-based on the strength of the incoming stimulation (to dendrite) the neuron decides whether to pass the signal along
-if the stimulation is strong enough, the signal is transmitted along the entire length of the axon in a phenomenon called an action potential
= the neuron fires
Depolarization
The shift from negative to positive charge of a neuron.
Absolute Refractory Period (2)
- A recovery period that reestablishes the original distribution of ions immediately after an impulse
- can’t generate another action potential during this time
All-or-None Law (2)
- Action potential is not proportional to stimulation (not affected by strength)
- neurons fire at maximum intensity, or do not occur at all
(Neuron may fire many more times per second: eg. Pain/ or less frequent: eg. Breeze of air)
Graded potentials
Explained:
-when the change in membrane potential is small, and not big enough to be an action potential
-as ions move through each channel, they cause the membrane potential of the cell to move away from the resting potential
=graded potential
-can be positive or negative
Action Potential Threshold
The negative potential inside the axon has to be changed from -70 millivolts to -50 millivolts before triggering the action potential
