1.2 - Neural Impulses Flashcards

What are the two categories of nerve cells?

Neurons and glia

True or False: The shape of neurons dictate the function and direction of information

True

What is resting membrane potential?

The difference in electrical charge between the inside and outside of the cell when neurons are at rest, this spans the membrane of the cell

What is the measurement of resting membrane potential?

-70 mV, this neuron is said to be polarized because the inside is more negatively charged than the outside

What are the four ions that contribute to resting membrane potential?

Sodium (Na^+), Chloride (Cl^-) —> Greater concentration outside the cell

Potassium (K^+) and Negatively charged proteins —> Greater concentration inside the cell

True or False: Despite the homogenizing influence of these electrochemical forces, unequal ion distributions are maintained

True

What is selective permeability?

The ability of a cell membrane to let certain molecules to pass through while blocking others

What are the four factors acting on the resting membrane?

Electrostatic forces, diffusion, selectively permeable membrane, and sodium-potassium pump

What does resting membrane potential set the stage for?

An action potential

What does the Sodium-Potassium Pump do?

Actively move sodium ions out of the cell and potassium ions into the cell against their respective concentration gradients

What are the pre-synaptic terminals called that release chemicals when neurons fire?

Neurotransmitters

What do neurotransmitters do?

Diffuse across the synapse and interact with receptors on the post-synaptic cell’s membrane

What are the the two effects that neurotransmitters make have when they bind to receptors?

Depolarize—> the post synaptic membrane (decrease the resting membrane potential) and Hyper polarize—> the post synaptic membrane (increase the resting membrane potential)

What are Excitatory Post-Synaptic Potentials (EPSPs)?

Post-synaptic depolarizations—> increase the likelihood that a neuron will fire

What are Inhibitory Post-Synaptic Potentials (IPSPs)?

Post-synaptic hyper-polarization—> decrease the likelihood that a neuron will fire

True or False: Both EPSPs and IPSPs are considered to be graded potentials

True

What do weak signals elicit (IPSPs and EPSPs)?

Small post-synaptic potentials

What do strong signals elicit (IPSPs and EPSPs)?

Large post-synaptic potentials

Why is transmission of EPSPs and IPSPs decremental?

They decrease in strength as they travel through the neuron (like sound through air)

What effect do post-synaptic potentials created at a single synapse have?

A little effect on neuronal firing

True or False: Most neurons are covered with thousands of synapses

True

What is neuronal firing dependent on?

The net effect of post-synaptic potentials across all synapses and the balance between EPSPs and IPSPs

What does the axon hillock do?

It is the decision maker

What is spatial summation?

Summing signals that occur at the same time across different synapses

What is temporal summation?

Summing signals that occur at the same synapse across time

What is Action Potential?

Rapid depolarization and reversal of the resting membrane potential

What causes the membrane potential to reverse polarity?

Rapid opening of voltage-gated sodium channels and subsequent massive influx of sodium ions into the cell

What is the first step of action potential?

Sodium (Na^+) channels open, Sodium rushes in

What is the second step in action potential?

Potassium (K^+) starts to leave cell

What is the third step of action potential?

Sodium (Na^+) channels close

What is the fourth step of action potential?

Potassium (K^+) channels close

What happens immediately after an action potential?

The neurons enter a refractory period

What does the Absolute Refractory Period do?

The neuron cant product an action potential

What does the Relative Refractory Period do?

The neuron can produce an action potential, but requires more stimulation than usual

Why does the refractory period exist?

To help the body enter a natural recovery phase where the body cannot temporarily cannot be aroused or achieved another climax

What is the All-or-none Law?

When an individual nerve or muscle fiber responds to a stimulus with a complete, maximal reaction or not at all, regardless of how strong the stimulus is

True or False: All neurons are alike when it comes to action potentials

False

How do neurons differ regarding action potetials?

The threshold for triggering the action potential may differ, the magnitude of the action potential may differ, and the duration of the refractory period may differ

True or False: While neurons differ from one another, each neuron is consistent

True

What is the first step of how an action potential move (propagate) down the axon?

It begins at the axon hillock

What is the second step of how an action potential move (propagate) down the axon?

During the rising phase, sodium enters the axon

What is the third step of how an action potential move (propagate) down the axon?

Positive ions move toward patch neighboring axon with negative charge

What is the fourth step of how an action potential move (propagate) down the axon?

Voltage-gated Na^+ (sodium) channels open on this patch of membrane

What is the fifth step of how an action potential move (propagate) down the axon?

New action potential is regenerated

What happens once an action potential is generated?

It travels unchanged in magnitude down the entire length of the axon (all-or-none law)

How is the movement of action potentials down an un-myelinated axon?

It’s slow (~11 mph) and metabolically demanding because action potential has to be regenerated at each point along the axon’s membrane and since the sodium-potassium pump is an active process, requiring energy

True or False: Propagation down myelinated axons is faster (~270 mph) and requires less energy

True

What is Saltatory Conduction?

The rapid way an electrical impulse (action potential) “jumps” from one gap to the next along a myelinated nerve fiber

What is multiple sclerosis?

A neurodegenerative disease where the immune system mistakenly attacks the protective covering (myelin sheath) the nerve fibers

What happens to the action potentials in multiple sclerosis?

They will die out between one node and the next

What symptoms can multiple sclerosis cause?

Tremor, loss of coordination, visions problems, and cognitive impairment