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
Myelin Sheath
A fatty insulation layer derived from glial cells during development
What is the use of the myelin sheath? (2)
- Insulates axon from electrical activity
- acts to increase rate of transmission of signals
Nodes of Ranvier
Gaps that exist in myelin sheath along axon
What is the use of nodes of Ranvier in myelin sheath?
Signals jump from one gap to the next
What is an example of a result of damage of myelin sheath?
Multiple sclerosis
- caused by demyelination of axons
- immune system attacks myelin sheath
Axon terminal
-transmits the information to the next cell in the chain
What do you call a bundle of axons travelling together?
Nerve (very long)
