Anatomy and Physiology Chapter 13

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Questions and Answers

What ions are pumped out and into the cell by the Na+/K+ pump?

3 Na+ ions out and 2 K+ ions in (correct)

2 Na+ ions out and 3 K+ ions in

2 K+ ions out and 3 Na+ ions in

3 K+ ions out and 2 Na+ ions in

What term describes a reduction in the charge difference across a neuron's membrane?

Hyperpolarization

Depolarization (correct)

Resting potential

Repolarization

Which type of membrane channel is always open or opens randomly?

Leak channels (correct)

Mechanically-gated channels

Voltage-gated channels

Ligand-gated channels

What causes hyperpolarization in a neuron's membrane potential?

Ions flowing out of the neuron Signup and view all the answers

Which channels are specifically responsive to binding of molecules?

Ligand-gated channels Signup and view all the answers

Which type of channel opens in response to physical pressure or deformation?

Mechanically-gated channels Signup and view all the answers

What is the role of ATP in the Na+/K+ pump?

Provides energy for ion movement Signup and view all the answers

What occurs if depolarization is followed by a return to a polarized state?

Repolarization Signup and view all the answers

What is the resting membrane potential (RMP) primarily created by?

Ion gradients and ion channels Signup and view all the answers

What type of channels respond to specific stimuli by opening or closing?

Active gated channels Signup and view all the answers

What direction do ions flow when channels are open?

From areas of higher concentration to lower concentration Signup and view all the answers

Which type of ion channels are concentrated at the synapse?

Ligand-gated channels Signup and view all the answers

What is the primary energy expenditure of neurons related to?

Creating a net negative charge inside the cell Signup and view all the answers

How do anions typically move in relation to electric charge?

Toward positively charged areas Signup and view all the answers

Which channel opens in response to mechanical deformation?

Mechanically-gated channel Signup and view all the answers

What characteristic best describes leakage channels?

They open and close randomly. Signup and view all the answers

What occurs in a diverging circuit?

A small number of neurons stimulate a much larger number of neurons. Signup and view all the answers

Which type of circuit is characterized by impulses being sent back through repeatedly?

Reverberating circuit Signup and view all the answers

What is a feature of parallel after-discharge circuits?

They involve a single presynaptic cell that stimulates a group of neurons. Signup and view all the answers

What occurs in a converging circuit?

Many neurons converge to stimulate one neuron. Signup and view all the answers

What types of activities are reverberating circuits commonly associated with?

Breathing and coordinated muscular activities. Signup and view all the answers

What occurs when a neurotransmitter binds to receptors on a postsynaptic neuron?

It causes a graded potential. Signup and view all the answers

Which of the following is NOT a method of eliminating neurotransmitters from the synapse?

Deactivation Signup and view all the answers

Which neurotransmitter is classified as an amino acid?

GABA Signup and view all the answers

What type of receptors does acetylcholine act upon?

Nicotinic receptors and muscarinic receptors Signup and view all the answers

Which category of neurotransmitters includes serotonin and dopamine?

Biogenic amines Signup and view all the answers

What enzyme is responsible for breaking down acetylcholine?

Acetylcholinesterase Signup and view all the answers

What aspect does the effect of the same neurotransmitter depend on?

The type of receptor it binds to Signup and view all the answers

Which function is not characteristic of neurotransmitters?

Changing the cellular DNA Signup and view all the answers

What occurs during the relative refractory period?

A second action potential can be initiated only by a larger-than-normal stimulus. Signup and view all the answers

Which type of conduction occurs in myelinated axons?

Saltatory conduction Signup and view all the answers

What factors affect the speed of action potential propagation?

Axon diameter, myelination, and temperature Signup and view all the answers

How do graded potentials differ from action potentials?

Graded potentials do not exhibit a refractory period. Signup and view all the answers

What is one of the characteristics of A fibers?

Large, fast, myelinated neurons that carry touch sensations Signup and view all the answers

Which of the following best describes the nature of signal transmission at the synapse?

It is a one-way transfer from presynaptic to postsynaptic neuron. Signup and view all the answers

What is the function of voltage-gated Ca2+ channels at the axon terminals?

To allow Ca2+ to flow inward and trigger neurotransmitter release Signup and view all the answers

What role does the frequency of action potentials play in stimulus perception?

It affects the intensity of the perceived stimulus. Signup and view all the answers

Study Notes

Na+/K+ Pump

Essential for maintaining resting membrane potential in neurons.
Pumps 3 sodium (Na+) ions out and 2 potassium (K+) ions into the cell using ATP.
Creates chemical and electrical gradients across the membrane.

Changes in Resting Membrane Potential

Membrane potential varies as ions move in and out of neurons.
Depolarizing changes reduce charge difference; hyperpolarizing changes increase it.
Repolarization restores the polarized state after depolarization.
Ion channels facilitate these changes, some are always open, while others respond to stimuli.

Classes of Membrane Channels

Ligand-gated channels: open due to binding of a signaling molecule (ligand).
Mechanically-gated channels: open in response to mechanical pressure.
Voltage-gated channels: open with changes in electrical potential.
Leak channels: randomly open and close, not influenced by a specific stimulus.

Electrical Signals in Neurons

Resting membrane potential (RMP) is crucial for generating electrical signals, akin to a battery.
RMP arises from ion gradients and specific ion channels.
Ions move through channels; cations move toward negative areas and anions toward positive areas.

Types of Active, Gated Channels

Ligand-gated channels: activated by neurotransmitters at synapses.
Voltage-gated channels: activated by changes in membrane electrical potential, found on axons.
Mechanically-gated channels: respond to physical deformation.
Leak channels: always open or randomly operate, influencing ion movement passively.

Action Potentials (AP)

Relative refractory period allows for a second AP only with a stronger stimulus; occurs during ongoing K+ channel activity after Na+ channels reset.
AP propagation initiates at the axon hillock, with two methods:
- Continuous conduction (slow, unmyelinated axons).
- Saltatory conduction (fast, myelinated axons; AP jumps between nodes of Ranvier).

Factors Affecting AP Speed

Axon diameter, amount of myelination, and temperature influence conduction speed.
Frequency of APs and number of activated neurons are critical for stimulus perception.

Fiber Types

A fibers: large/fast (up to 130 m/sec), myelinated, convey touch/pressure, and motor signals.
B fibers: medium speed (15 m/sec), myelinated, including visceral sensory neurons.
C fibers: small/slower (2 m/sec), unmyelinated, primarily sensory and autonomic motor neurons.

Synaptic Transmission

Transmission at the synapse is unidirectional (presynaptic to postsynaptic neuron).
AP reaching axon terminals opens voltage-gated Ca2+ channels, triggering neurotransmitter release.
Neurotransmitters bind to postsynaptic receptors, producing graded potential.

Neurotransmitter Elimination

Neurotransmitters are cleared from synapses by:
- Diffusion
- Reuptake into the presynaptic neuron
- Enzymatic breakdown

Neurotransmitter Categories

Cholinergic: Acetylcholine released by cholinergic neurons.
Amino acids: Include glutamate, inhibitory GABA, and glycine.
Biogenic amines: Serotonin, dopamine, epinephrine, and norepinephrine.

Effects of Neurotransmitters

Same neurotransmitter can produce varying effects depending on the receptor type.

Neural Circuits

Neuronal networks can contain thousands or millions of neurons.
Types include:
- Diverging circuits: few neurons stimulate many.
- Converging circuits: many neurons influence a few.
- Reverberating circuits: recurrent pathways used in functions like breathing, memory.
- Parallel after-discharge circuits: single presynaptic neuron stimulates multiple neurons for complex tasks.

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Description

Explore the critical functions of the Na+/K+ pump in neurons as detailed in Chapter 13 of 'Anatomy and Physiology'. This quiz focuses on the role of this pump in establishing the resting membrane potential through ion transport and energy utilization. Test your knowledge on this essential physiological concept.