Lab 3

what maintains the Na+/K+ concentrations

Na+/K+ AtPase pumps

where are large negative organic ions found

only inside cytoplasm (trapped)

At rest what has greater permeability in a neuron

K+

non gated ion channels are important for ___

Resting membrane potential

what is RMP

difference in charge that exists across neuron membrane at rest

neuron charge is ____mV at RMP

-70mV

at RMP the cytoplasm is 70mV more ____ than the ECF

negative

3 factors that maintain the RMP

Na/K ATPase pump

non gated K ion channels

Large negative charged organic molecules

does Na/K ATPase pump need energy

yes

1 ATP results in what for Na/K ATPase

3 Na+ out

2 K into the neruon

why is ATP needed for Na/K ATPase pump

moving Na and K against there gradients

what makes the largest contribution to RMP, WHY?

non gated K ion channels

K leaves the cell and makes it more negative inside

when is RMP reached

Na entering and K exiting the cell are equal (no net charge movement)

what does it mean for neurons to be electrically excitable

they can leave RMP

why does membrane potential change when neuron is stimulated

opening of gated ion channels

when will AP occur

if GP reaches threshold point (-55mV)

Graded potential

small change in membrane potential

where do graded potentials occur

dendrites and cell bodies

what causes GP

opening of gated ion channels

GP causes ions to diffuse how far

short distance

the magnitude and distance of electrical potential varies due to___

strength of stimulus

AP is generated if a GP is _______

depolarizing and large enough

critical stimulus

causes GP that is big enough and depolarizing

2 ways GP can be

depolarizing

hyperpolarizing

depolarizing GP

inside of cell becomes more positive then RMP

Hyperpolarizing GP

inside of cell becomes more negative then RMP

Repolarizing

returning to RMP

GP’s can summate TF

true

Action potential arises from____

steep change in membrane potential

does an AP change intesity along an axon length

no

where do AP’s start

trigger zone

what is the trigger zone of bi, multi, unipolar neurons

axon hillock - bi, multi

dendrites - unipolar

what are the 3 phases of AP

depolarization phase

Repolarzation

Post-hyperpolarization

what happens during depolarization phase of AP

voltage gated Na channels open

Na rushes into the cell

inside of cell becomes positivly charged

depolarization phase of AP has a ______ feedback loop

positive

what happens in the repolarization phase of AP

Na channels close and Na levels return to normal

K channels open K rushes out and inside of cell becomes more negative

what happens during post hyperpolarization

brief hyper polarization due to K rushing out (K channels are slow to close)

after post hyperpolarization when does RMP return

once K channels close

2 types of refractory periods after AP

Absolute refractory period

Relative refractory period

Absolute refractory period

AP cannot happen no matter what

What causes absolute refractory period

All Na channels open or not able to open

Relative refractory period

AP can happen but need larger stimulis

what causes relative refractory period

Na channels closed but can reopen

K channels open and membrane is hyperpolarized

what is the all or nothing of AP

every time threshold reached AP generated with same strength (no ½ AP)

Action potentials can move in ____ direction(s) WHY

1

because of refractory period of the AP before it

How do AP’s move along the entirety of the axon

+ charge moves towards - down the membrane

rate of AP propogation is dependent on

Fiber diameter

Whether the fibre is myelinated

how does diameter influence rate of propogation

larger = faster

Myelinated fibers have ______ conduction

saltatory

unmyelinated fibers have _____ conductin

continous

saltatory conduction

AP occurs at nodes of ranvier

Continous conduction

AP accurs along the entire fiber

which is faster saltatory or continous conduction

saltatory

transmission of neural impulses occur across the _____

synapse

Excitatory post synaptic potentials are _____ potentials

graded

EPSPs cause _____ on the post synaptic neuron

depolarization

what causes the potential in EPSP

opening of Na or Ca

or

closing of K channels

what is the most frequent neurotransmitter for EPSP

acetylcholine

where are EPSP located

dendrites and cell body of post synaptic neuron

EPSPs can summate TF

true

when do inhibitory post synaptic potentials happen

when graded potential leads to hyperpolarization

what causes IPSPs

opening of K or Cl

is an AP more likely with EPSP or IPSP

EPSP

what is the common neurotransmitter of IPSP

GABA

the sum of ______ and _____ determine if AP happsn

IPSP and EPSP

what Neurotransmitter is released at neuromuscular junction 100%

Acetylcholine

what does Ach do at neuromuscluar junction

opens Na gates on sarcolemma

what is the specific graded potential that is produced at neuromuscular junction

end plate potential

when is AP able to happen at neuromuscular junction, why?

everytime, no summation needed

lots of Ach released everytime

what types of gated ion channels used in graded potential

chemical

mechanical

thermal

what type(s) of gated ion channels used in AP

voltage

do graded potentials have refractory period

no

explain synaptic transmission

AP arrives at synaptic end bulb (axon terminal)

Ca2+ enters the neuron via voltage gated channels

this triggers the release of NT via exocytosis

NT released onto synaptic cleft where it binds with receptors

causing chemically gated channels to open and start graded potential on post synaptic neuron

post synaptic potential

graded potential that starts on the post synaptic neuron (after synaptic transmission)

glutamate is a NT involved in _PSP

EPSP

what is the threshold value at the dendrites and cell body of post synaptic neuron

+25mV

many different neurons can synapse to the same post synaptic neuron (TF)

True

glycine is a NT for _PSP

IPSP

cerebellum coordinates

muscle contraction

Reflex

rapid and automatic response to stimuli

the stimuli of a reflex always produces a differnet movement TF

false

reflexes involve _______ (#) of neruons

2+

what is the reflex pathway

stimulus reaches receptor

goes to CNS

CNS generates response

effector cell does movement

the type of reflex is dependet on

effector

somatic reflex effector is

skeletal muscle

visceral or automnomic reflexes effector is

smooth, cardiac or gland

in somatic reflex the ____ of CNS recives the reflex

spinal cord

what is the receptor, effecotr, of stretch reflex

R - muscle spindal

E - quad

ipsilateral reflex

stim and respnse on the same side of body

monosynaptic

one sensory neuron and one motor neuron

flexor reflex (withdrawl), Receptor and effector

R - pain, touch

E - hamstring

is flexor reflex monsynaptic or polysnaptic

polysynaptic

polysnaptic

has more than 1 synapse, 2+ neurons

contralateral reflex

stimulus and reflex on opposite sides

flexor reflex is ipsilatteral or contralateral

ispilatteral

crossed extensor reflex is ipsilatteral or contralateral

contralateral

what is R and E of crossed extensor reflex

R - touch, pain

E - quad (contracts)

how are flexor and crossed extensor reflexs related

crossed extensor is the 2nd half of flexor (catch balance)

crossed extensor reflex is mono or polysynaptic

polysynaptic

reciprocal inhibition

agonist activation causes inhibition of antagonist