Outline-3, BIO 2310, Neurophysiology


A. Membrane Potentials

1. Anion, cation distribution

Fixed anions inside cell, Potassium and Sodium are primary cations

2. K potentials {155mEq/l inside; 4mEq/l outside}

3. Na potentials {12 mEq/l inside; 145mEq/l outside}

4. Resting Membrane Potential[-65 to -85mV]

There is a charge difference inside versus outside of the cell

a. Na/K pump [200mill/sec]

3 Na out for every 2 K in contributes to resting membrane potential

b. Differential permeability

Unstimulated membrane is permeable to K but not Na

c. K diffusion

K tends to diffuse out of the cell

d. Na diffusion

Na tries to diffuse into cell but cannot due to membrane permeability

B. Action Potential

1. Local potential{Depolarization below threshold}

Stimulation results in sodium gate to open, and sodium enters cell

2. Events of Action Potential

a. Depolarization to threshold

b. Na gates open, Na in

c. + feedback, voltage regulated gates

d. Short-lived

Sodium gates are open for a very short time

e. Repolarization; K gates

Potassium gates are open for a longer period of time

f. Na/K pump

Returns Na and K concentrations back to normal after action potential is completed

g. All or none

C. Nerve Impulse

1. Unmyelinated axons

a. Current flow

b. Depolarization & Action potentials in adjacent areas

c. Unidirectional –based on the action potential beginning at one end of the neuron

2. Myelinated axons

a. Saltatory conduction

b. Speed (225mph)



-Presence of Myelin

c. Efficiency

d. Newborns

Myelination is not yet complete

D. Synapses

1. Presynaptic Neuron

2. Postsynaptic Neuron

3. Convergence/Divergence

4. Chemical synapses; Synaptic Cleft

5. Synaptic delay


a. Synaptic vesicles

b. Receptors

c. Fate of

d. Acetylcholine as an example


Breaks down acetylcholine

e. Norepinephrine (made from tyrosine) {arousal, dreams}

f. Epinephrine {emotions, behaviors}made from tyrosine

g. Dopamine {speed-build up causes euphoria; emotional responses}made from tyrosine

-Catecholamines group of neurotransmitters synthesized from tyrosine

h. Serotonin {sleep, temp. reg.}

i. Amino acids, Hormones

7. Neuromodulators

Chemicals that influence the synthesis/effectiveness of, or response to neurotransmitters

a. Enkephalins

a specific endorphin, runners “high”

b. Endorphins

Morphine-like chemical that inhibits release of pain neurotransmitters

8. Excitatory synapses (EPSP – excitatory postsynaptic potential)

a. Temporal Summation

b. Spatial Summation

9. Inhibitory synapses (IPSP – inhibitory postsynaptic potential)


10. Receptors

a. Definition

1. Dendrite

2. Specific

3. Converts energy forms to electrical signal

b. Stimulus

1. Graded

2. Intensity

c. Adaptation

11. Effectors

a. Bring response

b. Neuromuscular junction

c. End-Plate potential

Graded potential