Nervous System 1 Nov 18th Flashcards
Mastery
Neural Communication
what is excitable, how do they change
what is a neuron
what is a nerve
3 different types of neurons
Neural Communication
Nerve and muscle are excitable tissues
Can undergo rapid changes in membrane potentials critical to the function of the neurons and
muscles
Neuron
Single nerve cell
Nerve
Bundle of neurons
Bipolar
Pseudo-unipolar
Multipolar
what does cell body do
what do dendrites do
what makes up a neuron
Cell body
Houses nucleus and organelles
Dendrites
↑ surface area for receiving signals
Sends signal toward cell body
- neurons input zone
A typical neuron is
composed of:
* A dendritic region
* A cell body
* Axon hillock
* An axon
* Axon terminals
what do axons do
what does the axon hillock do
axon terminals
Kinesins
Dyneins
Microtubule
Axon
Nerve “fibre”
Conducts impulses (AP’s) away from the cell body
Axon hillock
* Where axon meets cell body
* Neuron’s trigger zone
Axon terminals
* Synapse with other neurons
or effector organ
* Release chemical messengers
Kinesins
Carry nutrients, enzymes, organelles away from cell body
Dyneins
Carries recycled vesicles, chemical messengers back towards the cell body
Microtubule
“railway”
how do you compare membrane potential. Na+K+ pump
membrane potential in nerve and muscle cells
membrane potential in resting potential
how do you measure resting potential
whats the resting #
Sodium potassium pump pumps out 3+ and only takes 2+ in so it is negative, it is relative to the membrane. Lose positive to the outside
Nerve and muscle cells
Excitable cells
can produce rapid, transient changes in their membrane potential
Resting membrane potential
Constant in cells of non-excitable tissues and excitable tissues at rest. The difference between the inside and the outside
put one electrode on inside and one out and measure the difference
-70mV in the resting
what do the movement of ions depend on
pull of Na+ and K+
Depends on
- Permeability. Controlled by channels
- Electrical gradient. Positive charge is drawn to negative
- Concentration gradient. Moves from high to low concentration
K+ moves slower because of charge
Nernst equation
Sodium value
Potassium value
Describes equilibrium potential for an ion
ENa = +60 mV
If only Na were allowed to move, equilibrium would be reached at +60
* Both electrical and concentration gradients encourage
inward movement
EK = -89mV
If only K+ were allowed to move, equilibrium
would be reached at -89mV
* Due to opposing electrical and concentration gradients
Resting membrane potential
Gates? Pumps? What 4 mechanisms?
- Na+ and K+ Gates are closed
- Na+/K+ pumps working
Potential is maintained by 4 mechanisms
- Impermeable membrane
- Na+/K+ ATPase pump
- Increased permeability to K+. Leaks out
- Anions inside the membrane(amino acids, contribute to negative charge)
2 types of potential changes
graded potentials help us get to action potential THRESHOLD
GRADED potentials. what are they initiated by? What cells? where do they go and for how long? can they summize? What does their strength depend on? Excitatory or inhibitory? Refractory period?
Examples of graded potentials:
Graded potentials
* Serve as short-distance signals
Action potentials
* Serve as long-distance signals
* Once initiated, action potentials are conducted
throughout a nerve fibre
Initiated by
- Mechanical stimulus
- Chemical stimulus(heat)
- Electrical stimulus
Usually initiated in Dendrites Eg. Receptor cells
Local and die quickly
They can join together to get stronger
the amplitude of a graded potential depends on
the stimulus strength
Can be excitatory or inhibitory
No refractory period. Temporal effect
Examples of graded potentials:
Postsynaptic potentials(onto the next neuron)
Receptor potentials(gates to open)
End-plate potentials(nerve to muscle)
Pacemaker potentials(heart)
Slow-wave potentials
Action potentials
what size? how big is the change? gates? decrease in distance? time to reset? Na+ and K+ stopping and closing their gates? refractory? how to code for intensity? EXCITATORY OR INHIBITORY
stages of action potential
at the end?
ALL OR NONE. happen at the same size or not
Brief, rapid, large (100mV) changes in membrane potential
potential reverses
Na+ and K+ gates involved
Do not decrease in strength as they travel from their site of initiation
refractory period.
increase frequency cause you can’t change size
only excitatory
Gates need time to reset and restart. Na+ reset fast, because they inactivate
Resting potential
Depolarization(na+ rushes in at -55mV)
Repolarization(Na+ close, K+ opens)
hyperpolarization(K+ slow to close and overshoot)
The Na+/K+ pump gradually restores the concentration gradients disrupted by action potentials
Sodium is pumped into the ECF
Potassium is pumped into the ICF
2 different refractory periods
self propagating action potentials
they only move in ONE DIRECTION
A.R
Absolute Refractory Period
When a second AP is not possible even with a large stimulus
ends at the end or repolarization
Relative Refractory Period
the interval of time during which a second action potential can be initiated, but initiation will require a greater stimulus than before
. In that hyperpolarization phase
An impulse in one region is enough of a
disturbance to cause the neighbouring
regions to reach threshold and trigger an AP
Breakdown the action potential graph
#s to know
where are graded potentials
Resting
Na+ out and K+ in
Depolarization
Na+ moves in
K+ stays in
Repolarization
K+ moves out
Na+ still in
Refractory period
Ions reset
* Na moves out/K+
moves in
Overshoot of K+
