Nervous System

What Influeces diffusion and how does it do it (does it raise or lower rates)

Higher Magnitude of Concentration; Higher Diffusion
Higher Permability; Higher Diffusion
Higher Surface Area, Higher Diffusion
Higher Molecular size/weight; LOWER diffusion
Higher distance to travel / thicker membrance, LOWER diffusion

Does diffusion impact action potentials

yes

What are the two Catagories of diffusion

Chemical
Electrical

chemical diffusion

based on molecule (nonpolar) concentration

Electrical Diffusion

Involves Ions
In regards to molecule charge and the molecule concentration

Electrical and Chemical diffusion work against eachother to create the _____-_______

Membrane Potential

where can you find membrane potential

neurons and plasma membrane

resting MP
why

-70
Permability favors potassium out

P is more common ______ and moves _____
K is more common ______ and moves _____

inside; outward
Outside; inward

Na:K ratio in NA K ATPase

3:1

Membrane potential diffusion favors what

potassium moving out

Parts of an action potential

depolerization
repolerization
hyperpolerization

what flows in during DEPOLERIZATION

Na VG channels open

what flows in during REPOLERIZATION

NA VG channels inactivates, K VG channels open

what flows in during HYPERPOLERIZATION

both VG channels close

Na VG channels have how many states

3
open
Inactive close
active close

Voltage gated K channels move things

out

Voltage gated Na channels move things

inward

Propagation

action potentials propagate when locally generated
depolarizing current spreads to adjacent regions of
membrane causing it to depolarize

Types of propogation

Contiguous conduction
Saltatory

Contiguous conduction propogation

propagation of action potentials in unmyelinated fibers
by spread of locally generated depolarizing current to adjacent regions of membrane, causing it to depolarize

Saltatory Propogation

Jumps between Myelated fiber / myelin
FASTER

can AP’s move backward

NO

absolute refractory period

peak

relative refractory period

the dip following the peak

can a second spike be formed during absolute refractory period

NO

can relative refractory period open to respond to depolerization

yes

does hyperpolerization need a stronger stimulus

yes

Myelin

a multilayered sheath of plasma membrane, derived
from specialized glial cells, that wraps around axonal
fibers and acts as an insulator to the flow of current

Nodes of Ranvier

gaps in myelin insulation containing high
densities of voltage-gated Na+ and K+ channels

types of myelin cells and where they are

Schwann cells (Periferal nervous system)

Oligodendrocytes (CNS)

Schwann cells have the sheaths ________
Oligodendrocytes have them ________

inside
outside

What are Graded Potentials / key traits

Local changes in AP
varies in strength (depends on stimulus) rather than all or nothing
decays over time

how do graded potentials spread

resistance and passive current

AP vs Graded Potential

AP
All-of-none response
Propagates over entire cell
Triggered by threshold

Graded
Depends on stimulus
Decreases with distance
Triggered by stimulus
(• neurotransmitter-post
synaptic cells
• sensory receptor in sensory
neurons)

Synapses

junction between two neurons, or
between a neuron and a muscle or gland that
enables one cell to electrically and/or biochemically influence another cell

types of synaspe

electrical
Chemical

electrical synapse

neurons connected directly by gap junctions

Chemical synapses

chemical messenger transmits
information one way across a space separating the
two neurons

do we have more chemical or electrical synapse

chemical

what are gap jxns made of

connexins proteins

electrical

Synaptic transmission

the primary means of rapid inter-neuronal
communication in the brain

Presynaptic axon

initiates the signal

Neurotransmitter do what

carry signal bw synapse
binds to postsynaptic receptors

Postsynaptic (target) cell

recieves signal

Postsynaptic targets examples

muscle, gland or another neuron

Events for a chemical synapse

1) AP propegation in termin al button / presynaptic neuron
2) Ca enters
3) neurotransmitter release signal to postsynaptic receptora

4) bind of neurotransmitter to the post synaptic receptor
5) open ion channels in subsynaptic membrane

Types of GRADED POTENTIALS

Excitatory postsynaptic potential (EPSP)
Inhibitory postsynaptic potential (IPSP)

autonomic nervous system

homeostasis

somatic nervous system

motor neurons / movement

types of autonomic nervous system and fxn

Sympathetic → fight or flight
Parasympathetic → homeostasis

Excitatory postsynaptic potential (EPSP) key features

• common ones: Glutamate (glu) and ACh

• depolerization

Inhibitory postsynaptic potential (EPSP) key features

most common inhibitory neurotransmitters are gamma-amino
butyric acid (GABA) and glycine (Gly)

Hyperpolerization

Transmitter removal methods and how they work

- degradation - enzymatic breakdown (example: AChE)

- transport - active transport back into the presynaptic cell
“reuptake”

- diffusion - the transmitter simply diffuses away from the
synaptic terminal

Transmitter release example

tetanus toxin blocks vesicular fusion

Transmitter uptake example

- Cocaine blocks the reuptake of dopamine
- SSRIs (paxil, prosac, zoloft) block the reuptake of serotonin

Transmitter removal example

many insecticides block the degradation of ACh

Transmitter binding example

Curare blocks the postsynaptic action of ACh at the neuromuscular
junction

temporal summation

the additive effect of PSPs occurring close
together in time at the same place

spatial summation

he additive effect of PSPs occurring together
on nearby parts of the same cel

cancellation summation

EPSP and IPSP cancel each other.

presynaptic inhibition

synaptic inhibition of a synaptic terminal
causing a decrease in transmitter release