Lecture 19: Action Potentials Flashcards
what is a neuron
basic functional unit of nervous system
what is the function of a neuron
conduct messages & integrate information
come in variety of shapes and sizes
cell body of neuron
- contains organelles
-soma
dendrites
- many, short branched
- recieve info
- sends signals to cell body
axon
- one, long
- axon hillock ( signals fenerated
- synaptic terminals ( tips of branches at the end)
- transmits away from cell body (produces responce to stimulus)
- nerve = axons of many neurons
sensory neuron
- afferent neuron
- sensory receptor -> processing center
interneuron
- intergration
- interact only with other neurons
- 90% of neurons in brain
motor neuron
- efferent neurons
- processing center -> effector
pathway of info processing
- sense organ
- sensory neuron
- interneuron
- motor neuron
- effector
membrane potential
- all animal cells have selective permeable PM -> membrane is polarized
- potential to do WORK
charge difference is
negative on the inside compared to the outside
excitable cells
- generate rapid changes in membrane potential
- neurons and muscles
voltage
- measurement of mp
- use voltmeter
resting potential
- axon is at rest
- 70 mV
- result of NA+-K+ pump ion channels
sodium-potassium pump
- membrane protiens, along with PM of cell body, dendrites, and axon
one complete pumping cycle
- moves 3+ Na+ out for every 2 K+ moved in
- pumped against concentraion gradients ( active transport, requires ATP)
(SALTY BANANA)
ungated ion channels
- pores formed by clusters of specialized membrane-spanning proteins
- (selectively permeable)
- ions diffuse across membrane
-
what generated mp
any net movement of + or - charge
sodium channels
allow Na+ through
potassium channels
- diffusion of potassium ions that tare critical for achieving resting potential
- may more K+ channels than Na+ channels, PM is 100x more permeable to K+ than to Na+
potassium channel rules
- K+ pumped into cell can easily pass out, but once Na+ is out of cell, cannot easily come back in
- outside of cell becomes more positive (inside is more negative) -> major source of MP
-70 mh (RP)
- potential E
- can be changed by stimulus
- any environmental factor which induces change MP
- example: Physical pressure, Chemical change
Hyperpolarization
- MP moves below RP -> more negative, ex: -70 mV to -90 mV
- inhibitory: neurons ability to generate neural impulse
depolarization
- MP becomes more positive -> closer to 0
- EX: from -70 mV to -50 mV
threshold
- MP required to trigger an action potential
- most neurons: -55 mV
action potential : change in MP
- massive change in voltage, depolarization reaches threshold
voltage gated ion changes
- membrane protiens -> gate
- open & close
- shape regulated by changes in voltage
control passage of specific ions
- facilitated diffusion
- follows concentration gradient (no ATP)
types of channels
voltage- gated K+ channel
voltage- gated Na+ channel
gate closed:
no ions flow across membrane
gate opened:
ions flow through channel
strong stimulus
- opens more voltage-gated sodium channels
- produces large change in permeability (depolarization) if memebrane reaches threshols (-55
