MasteringA&P 06 Neurons Flashcards

Questions and Answers

What part of the nervous system performs information processing and integration?

Central nervous system

Which of the following allows us to consciously control our skeletal muscles?

The somatic nervous system

Efferent nerve fibers may be described as motor nerve fibers.

True

What is the name given to the electrical potential difference created by ion distribution across the membrane?

Resting membrane potential (RMP) Signup and view all the answers

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

Leak channels Signup and view all the answers

What does the sign and magnitude of the resting membrane potential value of -70 mV tell you?

The inside surface of the plasma membrane is much more negatively charged than the outside surface. Signup and view all the answers

Why is the plasma membrane much more permeable to K+ than to Na+?

There are many more K+ leak channels than Na+ leak channels in the plasma membrane. Signup and view all the answers

What factors influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane?

The presence of concentration gradients and leak channels Signup and view all the answers

What prevents the Na+ and K+ gradients from dissipating?

Na+-K+ ATPase Signup and view all the answers

Where do most action potentials originate?

Initial segment Signup and view all the answers

What opens first in response to a threshold stimulus?

Voltage-gated Na+ channels Signup and view all the answers

What characterizes depolarization, the first phase of the action potential?

The membrane potential changes from a negative value to a positive value. Signup and view all the answers

What characterizes repolarization, the second phase of the action potential?

Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV. Signup and view all the answers

What event triggers the generation of an action potential?

The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV. Signup and view all the answers

What is the first change to occur in response to a threshold stimulus?

Voltage-gated Na+ channels change shape, and their activation gates open. Signup and view all the answers

What type of conduction takes place in unmyelinated axons?

Continuous conduction Signup and view all the answers

An action potential is self-regenerating because __________.

depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment Signup and view all the answers

Why does regeneration of the action potential occur in one direction, rather than in two directions?

The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential. Signup and view all the answers

What is the function of the myelin sheath?

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals. Signup and view all the answers

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open. Signup and view all the answers

In which type of axon will the velocity of action potential conduction be the fastest?

Myelinated axons with the largest diameter Signup and view all the answers

Which neurotransmitter(s) is/are the body's natural pain killer?

Endorphins Signup and view all the answers

What is the role of acetylcholinesterase?

Destroy ACh a brief period after its release by the axon endings Signup and view all the answers

The substance released at axon terminals to propagate a nervous impulse is called a(n) ________.

neurotransmitter Signup and view all the answers

Enkephalins and endorphins are peptides that act like morphine.

True Signup and view all the answers

Study Notes

Central Nervous System & Somatic Nervous System

The central nervous system is responsible for information processing and integration.
The somatic nervous system enables conscious control over skeletal muscles.

Neuron Functionality

Efferent nerve fibers are classified as motor nerve fibers.
Resting membrane potential (RMP) indicates an electrical potential difference across the plasma membrane.
RMP is typically -70 mV, showing the inside of the membrane is more negatively charged than the outside.

Ion Channels & Membrane Permeability

Leak channels allow sodium (Na+) and potassium (K+) ions to diffuse across plasma membranes.
The plasma membrane is more permeable to K+ due to a higher number of K+ leak channels compared to Na+ channels.
The RMP is influenced by concentration gradients and the presence of leak channels.

Ion Gradient Maintenance

The Na+-K+ ATPase pump maintains Na+ and K+ gradients, preventing dissipation.

Action Potential Initiation & Phases

Most action potentials start at the initial segment of the neuron.
Voltage-gated Na+ channels open in response to a threshold stimulus (-55 mV), leading to depolarization.
Depolarization changes the membrane potential from negative to positive, peaking at +30 mV.
Repolarization occurs as the membrane returns to resting potential, closing Na+ channels and opening K+ channels.

Action Potential Conduction

The generation of an action potential is triggered by sufficient depolarization.
Continuous conduction occurs in unmyelinated axons, while action potentials regenerate due to Na+ influx along the axon.
Action potential conduction is unidirectional because of the inactivation of Na+ channels in segments just fired.

Myelin Sheath & Velocity

Myelin sheaths significantly increase the speed of action potential conduction to axon terminals.
Fastest conduction occurs in myelinated axons with the largest diameters.

Neurotransmitters & Their Functions

Endorphins function as the body's natural painkillers.
Acetylcholinesterase breaks down acetylcholine (ACh) shortly after its release to regulate synaptic transmission.
Neurotransmitters are chemicals released at axon terminals to propagate nerve impulses.
Enkephalins and endorphins, both peptides, mimic the effects of morphine, acting as pain relievers.

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Test your knowledge of neurons and the nervous system with these flashcards. Each card provides a question about key concepts, such as the central nervous system and the somatic nervous system, to help reinforce your understanding. Perfect for mastering anatomy and physiology!