BIO 140.01 - Module 04-03: Membrane Potential

Membrane potential

Difference in electric potential between the interior and exterior of the cell

Sodium-potassium pumps

Membrane potential is maintained primarily by ___

Na, Cl

Ions that will be higher outside of the neuron during resting potential

K

Ions that will be higher inside of the neuron during resting potential

Mimosa pudica

Plant that demonstrates how membrane potential works

Touching triggers a membrane potential across the plant cells that causes water to flows out of the cells

What causes the makahiya plant to close after being touched?

False

T or F: Neurons can connect to other neurons, muscles, or bones.

-70 mv

What is the charge of the resting potential

Polarized

During resting potential the membrane is electrically ___ (polarized/depolarized)

Action potential

a series of rapid propagating changes in the membrane potential of neurons

Length of the axon

The wave of depolarization occurs along the ___

Depolarization

A shift to the resting potential

Voltage-gated Na channels

Depolarization is facilitated by ___

-30 mV

What is the charge of depolarization?

-55 mV

(Charge of stimulus) Voltage-gated Na channels will open at ___

-75 mV

What is the charge of repolarization?

Na, in

When a stimulus reaches the depolarization threshold, ___ ions flow ___ (in/out) of the cell

False

T or F: Depolarization of one axon section causes polarization of an adjacent section

delayed voltage-gated K channels

What other channels are triggered open when depolarization occurs that facilitates repolarization?

-75 mv

Charge of hyperpolarization

K ions, out

During repolarization, ___ ions flow ___ (in/out) of the cell

Refractory period

a period wherein voltage-gated Na channels cannot open

Prevent the backflow of the action potential

Why does refractory period occur?

Hyperpolarization

The refractory period occurs during ___

Na-K pumps

What pumps restore the ionic gradient?

400 km/h

Speed of nerve signals

1 meter

Typical length of nerves

Saltatory Conduction

Action potential “jumps” from one node of Ranvier to another to increase nerve conduction velocity

Multiple sclerosis

Disease that interferes with saltatory conduction

Myelin sheath

In Multiple sclerosis, the ___ is damaged

False

T or F: MS only interferes with motor neurons

False

T or F: Anesthetics and neurotoxins work by blocking the axons of neurons

Conotoxins

Neurotoxin in cone snails that cause paralysis

Tetrodotoxin

Neurotoxin in puffer fish that cause paralysis

True

T or F: At lower doses, conotoxins can be used for therapeutic effects

Baldomero Olivera

Developed a conotoxin-based painkiller

Ziconotide

Conotoxin-based painkiller that is more powerful than morphine, non-addictive, and intolerable

Synaptic cleft

Gap between the pre- and post-synaptic neuron

Neurotransmitters

Transmission of signals across the neural synapse is bridged by ___

Na

Excitatory neurotransmitters open ___ channels

Cl-, K+

Inhibitory neurotransmitters open ___ channels

Na+, less, depolarizes

Excitatory NTs: ___ ions enter into the cell, making the inside ___ (more/less) negative, which ___ (depolarizes/hyperpolarizes) the membrane

Cl-, K+, more, hyperpolarizes

Inhibitory NTs: ___ ions enter or ___ ions leave the cell, making the inside ___ (more/less) negative, which ___ (depolarizes/hyperpolarizes) the membrane

Adrenaline

NT: Fight or flight

Noradrenaline

NT: Concentration

Dopamine

NT: Pleasure

Serotonin

NT: Mood

GABA

NT: Calming

Acetylcholine

NT: Learning

Glutamate

NT: Memory

Endorphins

NT: Euphoria

Interfere with reuptake or destruction of NT, over- or undersecretion of NT, mimic NTs

3 ways psychoactive drugs affect neurotransmitter functions

Inhibit, Reuptake, Serotonin

Antidepressants ___ (inhibit/facilitate) the ___ (effect or action) of ___ (name of neurotransmitter)

Inhibit, Reuptake, Dopamine

Methylphenidates ___ (inhibit/facilitate) the ___ (effect) of ___ (neurotransmitter)

False

T or F: Amphetamines block the reuptake of dopamine

Ecstasy

Psychoactive drug that slows down serotonin reuptake

LSD

Drug that mimics effects of serotonin

Amphetamines, shabu

Drug that blocks dopamine reuptake or induces oversecretion

Cocaine

Drug that blocks dopamine reuptake

Cannabis

Drug that prevents release of neurotransmitters by pre-synaptic cells

Dopamine, dopamine receptors

The brain adapts to dopamine surges by (1) reducing the production of ___ or (2) reducing the number of ___

True

T or F: The reduction of dopamine production or dopamine receptors caused by drug addiction is reversible.

Neuromuscular Junction

Motor neurons connect to muscles via ___

5

Transmission at the neuromuscular junction causes sequential activation of ___ (number) sets ion channels

Increase, Ca2+, myofibrils

When the neuromuscular junction is activated, there is an ___ (increase/decrease) in cytosolic ___ (ion) which causes ___ in the muscle cell to contract

Amyotrophic Lateral Sclerosis

This is caused by damage to motor neurons