- sensory or afferent neuron - motor or efferent neuron - interneuron

- Voltage or membrane potential across its plasma membrane

Lec 5: Membrane Potential Flashcards by IVAN Dyan

Functional Units of Nervous System
receive, process and transmit information to other cells

Neurons

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Three main parts of neuron

Soma
dendrites
Axon

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metabolic maintenance

Soma

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receptive surface that brings signals from other neurons toward the cell body

Dendrites

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conduct signals away from the cell
carry information for long distances with high fidelity and without loss

Axons (nerve fibers)

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Types of neurons

sensory or afferent neuron
motor or efferent neuron
interneuron

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carry signals from sensory receptors

sensory or afferent neuron

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transmit signals from the CNS to muscles or glands, leading to an action or response

Motor or efferent neuron

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act as connectors or intermediaries between sensory and motor neurons.

Interneurons

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Transmission of signals in a single neuron

surface membrane innervated
action potential initiation
AP carried from spike-initation zone to axon terminal

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integrates input to initiate an action potential

Soma

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surface membrane of motor-neuron dendrites & soma are ____

Innervated

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Where is the spike-initiating zone of a motor neuron located

near axon hillock to the axon terminal

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Potential target of AP when it reach axon terminal

Skeletal muscle cell or glands

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Localized electrical gradient
electrical potential differences across the cell membrane caused by different concentration of K+, Na+ and Cl- ions

Membrane potential

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Membrane potential of neurons is usally between ___ and ___ mV

-60 to -80 mV

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Excitable cells use changes in membrane potential as

communication signals

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location of excess of negative charges

Plasma membrane side

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location of excess positive charges

on the other side

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Every cell has what?

Voltage or membrane potential across its plasma membrane

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is a localized electrical gradient across membrane

Membrane potential

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are more concentrated within a cell

Anions (negative)

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are more concentrated in the extracellular fluid

Cations (positive)

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Factors affecting membrane potential

Concentration gradient for an ion
Membrane that is permable to that ion

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measures membrane potential

Voltmeter

Resting pontential of an unstimulated cell

-70 mV

equal numbers of anion and cations

Electroneutral

Channel that potassium ions move out of the cell along concentration gradient

Potassium channel

Results when potassium moves out

- Electronegativity

draw positive charges into the cell

Excess negative charge inside

How a cell maintain a membrane potential

- Cations - Anions

the principal intracellular cation

K+

is the principal extracellular cation

Na+

is principal extracellular anion

Cl–

principal intracellular anions

- Proteins - Amino acids - Sulfate - Phosphate

Cations

- K+ - Na+

Anions

- Proteins - Amino acids - Sulfate - Phosphate - Cl-

at resting potential, concentration of ___ is greater inside the cell, while ___ is greater outside the cell

K+ greater inside the cell, Na+ is greater outside the cell

use the energy of ATP to maintain these K+ and Na+ gradients across the plasma membrane

Sodium-potassium pumps

converts chemical potential to electrical potential

opening of ion channels

a neuron at resting potential

- many open K+ channels - fewer open Na+ channels - K+ diffuses out of the cell

allow ions to diffuse across the plasma membrane - always open

Non-gated ion channels

can generate large changes in their membrane potential

Excitable cells

open or close in response to stimuli

Gated ion channels

Types of gated ion channels

- Chemically-gated ion channels (ligand-gated ion channels) - voltage-gated channels

open or close in response to a chemical stimulus

Chemically-gated ion channels (ligand-gated ion channels)

open or close in response to a change in membrane potential

voltage-gated ion channels

are changes in membrane potential

Graded potentials

Types of graded potentials

- Hyperpolarization - Depolarization

- Gated K+ channels open - K+diffuses OUT of the cell - the membrane potential becomes more negative

Hyperpolarization

Gated Na+ channels open - Na+diffuses INTO the cell - the membrane potential becomes less negative

Depolarization

All or Nothing Depolarization

The Action Potential

What happens when graded potentials sum to approximately -55 mV?

Threshold potential is achieved

What happens when threshold potential is reaches?

Action potential is triggered

In resting state, what happens to K+ channels

- Closed voltage-gated K+ channels open slowly, in response to depolarization

Two gates of Voltage-gated Na+ channels

- Closed activation - Open inactivation

open rapidly in response to depolarization

Closed activation gates

close slowly in response to depolarization

Open inactivation

Phases of action potential

- Depolarization - Overshoot - Repolarization

a result of a temporary inactivation of the Na+ channels.

Refractory period

What happens to action potential after the refractory period

Cannot be initiated

a state of recovery that occurs after a neuron has fired an action potential

Refractory period

Where does nerve impulses propagate?

Along the axon

the rapid method by which nerve impulses move down a myelinated axon

Saltatory conduction

Site of excitation

Nodes of Ranvier

Classes of Synapses

- Electrical synapses - Chemical synapses

action potential travels directly from the presynaptic to the postsynaptic cells via gap junctions

Electricl synapses

more common than electrical synapses

- chemical synapses

is a region where neurons nearly touch and where nerve impulse is transferred

Synapse

is the small gap between neurons

Synaptic cleft

Carried out transmission across synapse

Neurotransmitters

Primary factors influencing impulse transmission

- Axon diameter - Myelination - Temperature

Typical diamter of axon

around 1 micrometer

formation of the myelin sheath around a nerve

Myelination

the lower the temperature, the ____ the impulses move.

slower

varies as a function of axon diameter and myelination

Velocity of impulse propagation

how fast the membrane ahead of the active region is brought to threshold by the local-circuit current

Conduction velocity of AP

Evolutionary adaption to increase length constant

Invertibrates - increase axonal diameter Vertebrates - myelination

Lec 5: Membrane Potential Flashcards

(78 cards)