Neuroscience: Action Potentials and Nervous System

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Questions and Answers

What is the significance of the refractory period in the conduction of action potentials?

It increases the speed of the action potential propagation.

It allows action potentials to travel in two directions.

It prevents summation of action potentials, ensuring impulses travel one way. (correct)

It reduces the threshold required for action potential initiation.

What causes the depolarization of the axon's membrane during an action potential?

The diffusion of Na+ into the axon once threshold is reached. (correct)

A decrease in Na+ concentration inside the axon.

The influx of K+ ions into the axon.

The closing of voltage-gated channels along the axon.

What does the term 'all-or-nothing' mean in the context of action potentials?

The refractory period can be ignored if stimulus is strong enough.

The action potential can occur at various intensities.

The action potential can be partially suppressed during transmission.

The action potential either fully occurs or not at all once the threshold is met. (correct)

What is the role of voltage-gated ion channels during the action potential process?

They open and close in response to changes in membrane potential. Signup and view all the answers

What happens to the action potential when it travels along a long axon?

The action potential remains unchanged and is not attenuated. Signup and view all the answers

During which phase does a new action potential site get established?

When the membrane potential reaches threshold. Signup and view all the answers

What effect does the refractory period have on the frequency of action potentials?

It prevents further action potentials from occurring until after a brief delay. Signup and view all the answers

What initiates the opening of the voltage-gated Na+ channels?

Reaching the threshold voltage. Signup and view all the answers

What is the primary neurotransmitter released by the postganglionic fibers of the sympathetic system?

Noradrenaline/epinephrine Signup and view all the answers

During which state is the parasympathetic system predominantly active?

During rest and routine body activities Signup and view all the answers

What type of receptors are found in the postganglionic fibers of the parasympathetic nervous system?

Muscarinic receptors Signup and view all the answers

Which of the following statements about the sympathetic system is true?

It controls functions during situations of danger and stress. Signup and view all the answers

What is the characteristic length of the preganglionic fibers in the sympathetic nervous system?

Short Signup and view all the answers

Which subdivision of the nervous system primarily deals with the formation of resting and action potentials?

Central Nervous System Signup and view all the answers

Where do the sympathetic fibers emerge from in the central nervous system?

Thoracic and lumbar regions Signup and view all the answers

What is the resting potential of a nerve cell?

The negative charge when the nerve is at rest Signup and view all the answers

Which type of fibers are longer in the parasympathetic nervous system compared to the sympathetic nervous system?

Preganglionic fibers Signup and view all the answers

Which of the following neurotransmitters is released at the effector in the parasympathetic system?

Acetylcholine Signup and view all the answers

Which cranial nerve is primarily responsible for vision?

Optic nerve (II) Signup and view all the answers

How many spinal nerve pairs are classified under the lumbar category?

5 Signup and view all the answers

What is the primary function of a dermatome?

Supply sensory information from a specific skin region Signup and view all the answers

What is indicated by the term myotome in the context of spinal nerves?

The muscle innervated by motor fibers from a spinal nerve Signup and view all the answers

In terms of the autonomic nervous system, what is a characteristic of the sympathetic and parasympathetic divisions?

They often have opposite effects on the body’s organs Signup and view all the answers

What structures form the H shape of the gray matter in the spinal cord?

Three columns of neurons Signup and view all the answers

Which part of the gray matter is primarily responsible for afferent input?

Posterior horns Signup and view all the answers

How is white matter primarily characterized in the spinal cord?

Myelinated nerve fibers Signup and view all the answers

What is a key function of the lateral horns in gray matter?

Integration of spinal reflexes Signup and view all the answers

What does the term 'dermatome' refer to?

An area of skin innervated by a single spinal nerve root Signup and view all the answers

What is the role of descending tracts in the spinal cord?

They transmit impulses from the brain to the spinal cord Signup and view all the answers

Which of the following best describes the function of the spinal nerve?

It conveys mixed signals: motor, sensory, and autonomic Signup and view all the answers

In comparing sympathetic and parasympathetic structures, which statement is true?

Parasympathetic functions are often referred to as 'rest and digest' Signup and view all the answers

Which component of the autonomic system is responsible for the 'fight or flight' response?

Sympathetic nervous system Signup and view all the answers

What is the main significance of myotomes in the nervous system?

They assist in mapping out muscle innervation by spinal nerves Signup and view all the answers

What is the primary change that occurs during depolarisation in a nerve cell?

A change from negative to positive electrical potential Signup and view all the answers

What triggers the opening of voltage-gated sodium channels according to the content?

Reaching a specific threshold voltage Signup and view all the answers

During the re-polarisation phase, what is the direction of the electrical potential change?

From positive back to negative resting potential Signup and view all the answers

What is the result of the sodium ions diffusing into the axon during an action potential?

It initiates the propagation of the nerve impulse Signup and view all the answers

What defines the term 'refractory potential' in the context of action potentials?

The time when the membrane is unable to generate another action potential Signup and view all the answers

What allows an action potential to travel unidirectionally along an axon?

The inactivation of sodium channels after depolarisation Signup and view all the answers

What is the primary purpose of the action potential in a nerve cell?

To transmit nerve impulses over long distances Signup and view all the answers

What occurs immediately after an action potential is generated?

The sodium channels close and potassium channels open Signup and view all the answers

What is expected to happen if the threshold potential is not reached?

The membrane remains at resting potential without any change Signup and view all the answers

What is the primary ion involved in depolarisation during an action potential?

Sodium ions Signup and view all the answers

Study Notes

Organization of the Nervous System (Function) - Part 3

Nervous system organization is covered in part 3
Part 2 content was previously discussed.

Structural Classification of Neurons

Neuroglia surround neurons, provide nutrients, and remove dead neurons
Astrocytes supply nutrients to neurons
Ependymal cells form cerebrospinal fluid (CSF)
Microglial cells protect from disease and clear debris
Oligodendrocytes, form myelin around axons in the central nervous system (CNS)
Schwann cells form myelin around axons in the peripheral nervous system (PNS)

The Brain

Protective coverings include cranial bones and meninges (dura mater, arachnoid mater, pia mater)
Cerebrum (largest part) controls cognitive functions, including movement, sensory perception, and memory
Cerebellum controls balance and coordination
Brainstem (medulla oblongata, pons, midbrain) regulates vital functions like breathing and heart rate
Diencephalon includes the thalamus (relay center for sensory information) and hypothalamus (regulates homeostasis)

Spinal Cord

An elongated cylinder extending from the brainstem through the foramen magnum of the skull
Gray matter is the interior; white matter surrounds it.
31 pairs of spinal nerves attached by dorsal and ventral nerve roots
Lies within the spinal cavity and extends to the first lumbar vertebra, tapering downward
Two bulges, a cervical and lumbar region
Anterior median fissure and posterior median sulcus are two deep grooves
Fibers of the dorsal nerve root carry sensory information
Dorsal root ganglion houses cell bodies of unipolar sensory neurons
Fibers of the ventral nerve root carry motor information
Cell bodies of multipolar motor neurons are in gray matter
Interneurons are located in the spinal cord's gray matter
Cauda equina is a bundle of nerve roots extending from the conus medullaris

Spinal Nerve

31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)
Carry motor, sensory, and autonomic signals between the spinal cord and body

Types of Spinal Nerves

Cervical nerves: supply movement and sensation to the arms, neck, upper trunk; control breathing
Thoracic nerves: supply the trunk and abdomen
Lumbar nerves: supply legs, abdomen, groin, knees
Sacral nerves: supply legs, bladder, bowels, and sexual organs,
Coccygeal nerve innervates the skin of the coccygeal region

Dermatomes

Area of skin surface supplied by sensory fibers of a given spinal nerve

Myotome

Skeletal muscles supplied by motor fibers of a given spinal nerve

Cranial Nerves

12 pairs of cranial nerves
Carry sensory information to and control functions of the head and neck
Afferent and efferent nerve fibers run in pairs
Cranial nerve nuclei located in the brainstem

Somatic vs Autonomic

Somatic: controls voluntary functions; input from sense organs; output to skeletal muscles (muscle contractions)
Autonomic: controls involuntary functions; input from internal receptors; output to smooth muscles, glands (digestion, body temperature)
Autonomic NS (comparission with Somatic NS): Two neuron chain, pre-ganglionic, post-ganglionic.
Sympathetic/ parasympathetic NS (comparisons)

Autonomic: Sympathetic vs Parasympathetic

Sympathetic: dominant during danger, stress, increase metabolism, increase rhythmic activities
Parasympathetic: dominant during rest, controls routine body activities, decreased metabolism

Difference Effect of Autonomic

Different effects on various organs (eye, tear glands, salivary glands, lungs, heart, gut, liver, bladder) based on sympathetic and parasympathetic activation

Learning Outcome 5: Action Potentials

Membrane potentials: are electrical signals across a membrane
Resting potential: negative charge when the nerve is inactive
Depolarization: shift to a more positive charge
Repolarization: returns to a more negative charge
Refractory period: brief time the nerve cannot immediately respond to stimulation
Impulse transmission: propagating along the axon, voltage gated channels, all-or-none principle

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Description

Explore the crucial aspects of action potentials including their refractory period, depolarization mechanisms, and the role of voltage-gated ion channels. This quiz also covers the sympathetic and parasympathetic nervous systems and their neurotransmitters. Test your understanding of the fundamental principles that govern neuronal conduction.