Biology Chapter: The Nervous System and Neurons
48 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following statements accurately describes saltatory conduction?

  • The action potential is generated at the axon terminal and travels back towards the trigger zone.
  • The action potential 'jumps' from one node of Ranvier to the next due to the insulating effect of the myelin sheath. (correct)
  • The action potential travels continuously down the axon without any breaks.
  • The action potential travels slower in myelinated axons compared to unmyelinated axons.

What is the primary factor that determines the speed of action potential propagation?

  • The length of the axon.
  • The diameter of the axon and whether it is myelinated or not. (correct)
  • The concentration of potassium ions in the extracellular fluid.
  • The type of neurotransmitter released at the synapse.

How does myelination affect the speed of action potential conduction?

  • Myelination slows down conduction by creating a barrier to ion flow.
  • Myelination decreases conduction speed by reducing the number of voltage-gated sodium channels.
  • Myelination has no significant effect on conduction speed.
  • Myelination increases conduction speed by allowing the action potential to 'jump' from node to node. (correct)

Which of the following is NOT a characteristic of myelinated axons?

<p>They are found in the autonomic nervous system. (C)</p> Signup and view all the answers

What happens to the amplitude of the action potential as it travels down a myelinated axon?

<p>The amplitude remains relatively constant as the action potential travels from node to node. (D)</p> Signup and view all the answers

Which of the following statements correctly describes the relationship between axon diameter and conduction velocity?

<p>As axon diameter increases, conduction velocity increases. (C)</p> Signup and view all the answers

What is the difference between the speed of action potential conduction in a myelinated 8.6 μm mammalian axon and an unmyelinated 1.5 μm pain fiber?

<p>The myelinated axon conducts at approximately 60 times the speed of the unmyelinated axon. (D)</p> Signup and view all the answers

Which of the following is a primary function of the myelin sheath?

<p>To increase the speed of action potential conduction. (C)</p> Signup and view all the answers

What is the primary function of the nervous system?

<p>To facilitate communication and control vital operations of the body (C)</p> Signup and view all the answers

What are the two types of nerves in the peripheral nervous system?

<p>Afferent and efferent nerves (C)</p> Signup and view all the answers

What is the role of dendrites in a neuron?

<p>To receive messages from other neurons (A)</p> Signup and view all the answers

What initiates the electrical impulse in the axon?

<p>A sufficiently strong stimulus (D)</p> Signup and view all the answers

What does the term 'membrane potential' refer to?

<p>The separation of positive and negative charges across a membrane (B)</p> Signup and view all the answers

Which ions are primarily involved in establishing membrane potential?

<p>Sodium, potassium, and chloride (D)</p> Signup and view all the answers

What is the function of a synapse in neural communication?

<p>To act as a chemical junction between neurons (C)</p> Signup and view all the answers

Which cells can undergo rapid fluctuations in membrane potential?

<p>Both neurons and muscle cells (A)</p> Signup and view all the answers

What effect does the inactivation gate have on the Na+ channel during the action potential?

<p>It delays the channel's movement for 0.5 msec. (C)</p> Signup and view all the answers

Which ions are actively transported by the Na+–K+ ATPase pump?

<p>Three Na+ out of and two K+ into the cell. (D)</p> Signup and view all the answers

What is the primary characteristic of graded potentials?

<p>They vary in size according to the strength of the stimulus. (A)</p> Signup and view all the answers

What causes the influx of Na+ or Ca2+ in excitatory postsynaptic potentials (EPSPs)?

<p>Activation of ligand-gated ion channels by neurotransmitters. (D)</p> Signup and view all the answers

What occurs during an inhibitory postsynaptic potential (IPSP)?

<p>Decreased membrane potential and hyperpolarization. (C)</p> Signup and view all the answers

What happens during the process of neurotransmitter release at the axon terminal?

<p>Voltage-dependent calcium channels cause synaptic vesicle exocytosis. (B)</p> Signup and view all the answers

What effect does hyperpolarization have on the postsynaptic cell?

<p>Makes the postsynaptic cell less likely to reach action potential. (A)</p> Signup and view all the answers

Where in the neuron is the trigger zone typically located?

<p>At the junction of the axon and soma. (D)</p> Signup and view all the answers

What occurs during the falling phase of an action potential?

<p>Hyperpolarization as K moves out of the cell (A)</p> Signup and view all the answers

Which statement is true regarding the absolute refractory period?

<p>Na+ channels are resetting to resting positions (D)</p> Signup and view all the answers

What primarily causes the hyperpolarization of a neuron after an action potential?

<p>Prolonged opening of voltage-gated K channels (B)</p> Signup and view all the answers

Which function do the two gates of Na+ channels serve?

<p>To regulate Na+ ion movement in response to depolarization (D)</p> Signup and view all the answers

Which phase is characterized by the membrane potential becoming positive?

<p>Overshoot phase during action potential (B)</p> Signup and view all the answers

What is required for a cell to fire during the relative refractory period?

<p>A greater excitatory stimulus than usual (A)</p> Signup and view all the answers

What happens to Na+ channels during the repolarization phase?

<p>Na+ channels reset to a resting state (A)</p> Signup and view all the answers

How long does the refractory period last in a neuron?

<p>2 milliseconds (C)</p> Signup and view all the answers

What is the relationship between the strength of a graded potential and the frequency of action potentials triggered?

<p>Stronger graded potentials trigger more frequent action potentials. (B)</p> Signup and view all the answers

What is the role of the trigger zone in the generation of an action potential?

<p>The trigger zone is where the graded potential is converted into an action potential if the threshold voltage is reached. (B)</p> Signup and view all the answers

Which of the following factors contributes to the decrease in strength of a graded potential as it travels through the cytoplasm?

<p>The resistance provided by the cytoplasm to the flow of electricity. (D)</p> Signup and view all the answers

Which of the following is TRUE about hyperpolarizing graded potentials?

<p>They move the membrane potential farther from the threshold value. (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of graded potentials?

<p>They spread over long distances away from the stimulus. (A)</p> Signup and view all the answers

Which of the following factors influences the speed of action potential conduction in unmyelinated axons?

<p>The diameter of the axon. (C)</p> Signup and view all the answers

What is the primary function of Myelin?

<p>Myelin increases the speed of conduction by limiting the amount of membrane in contact with the extracellular fluid. (A)</p> Signup and view all the answers

How does the amount of neurotransmitter released at the axon terminal relate to the frequency of action potentials?

<p>Higher frequency action potentials cause the release of more neurotransmitter. (B)</p> Signup and view all the answers

During which phase of the action potential does the membrane potential become more negative than the resting potential?

<p>Hyperpolarization (C)</p> Signup and view all the answers

What is the primary function of voltage-gated sodium channels during the action potential?

<p>Allow sodium ions to enter the cell, causing depolarization (A)</p> Signup and view all the answers

What is the main difference between graded potentials and action potentials?

<p>Graded potentials are localized, while action potentials propagate along the axon. (D)</p> Signup and view all the answers

Which of the following is considered a triggering event for an action potential?

<p>The binding of a neurotransmitter to a receptor on the cell membrane. (A)</p> Signup and view all the answers

What prevents action potentials from traveling backwards along the axon?

<p>The refractory period during which the membrane is hyperpolarized. (D)</p> Signup and view all the answers

What is the primary function of the sodium-potassium pump in maintaining the resting membrane potential?

<p>Maintaining a concentration gradient of sodium and potassium ions across the membrane. (C)</p> Signup and view all the answers

What is the role of the threshold potential in action potential generation?

<p>It is the point where the membrane potential must be depolarized to trigger an action potential. (D)</p> Signup and view all the answers

Why is it essential for the membrane to become hyperpolarized during the action potential?

<p>To ensure that the action potential cannot travel backwards. (A)</p> Signup and view all the answers

Flashcards

What is the function of the nervous system?

The nervous system is a complex communication network that controls all vital functions of the body.

What is a neuron?

Neurons are the building blocks of the nervous system, responsible for transmitting information as electrical signals.

What are dendrites?

Dendrites are branched structures that receive incoming signals from other neurons and transmit them to the cell body.

What is the function of the cell body?

The cell body integrates incoming signals and generates an outgoing signal if the stimulus is strong enough.

Signup and view all the flashcards

What is the axon?

The axon is a tube-like structure that carries electrical impulses away from the cell body to other neurons, muscles, or glands.

Signup and view all the flashcards

What is a synapse?

A chemical junction between the terminal of one neuron and the dendrites of another neuron, where electrical signals are converted into chemical signals.

Signup and view all the flashcards

What are afferent nerves?

Afferent nerves carry sensory information from the body to the brain or spinal cord.

Signup and view all the flashcards

What are efferent nerves?

Efferent nerves transmit motor commands from the brain or spinal cord to muscles and glands.

Signup and view all the flashcards

Threshold potential

The membrane potential value that, when reached, triggers the initiation of an action potential.

Signup and view all the flashcards

Rising Phase of Action Potential

The rapid depolarization of the cell membrane caused by the influx of sodium ions.

Signup and view all the flashcards

Falling Phase of Action Potential

The rapid repolarization of the cell membrane caused by the efflux of potassium ions.

Signup and view all the flashcards

Refractory Period

A period following an action potential where the neuron cannot generate another action potential.

Signup and view all the flashcards

Absolute Refractory Period

The first part of the refractory period, where the neuron cannot generate another action potential regardless of the stimulus strength.

Signup and view all the flashcards

Relative Refractory Period

The second part of the refractory period, where the neuron can generate another action potential with a stronger stimulus.

Signup and view all the flashcards

Activation Gate

A gate in the sodium channel that opens in response to depolarization, allowing sodium ions to flow into the cell.

Signup and view all the flashcards

Inactivation Gate

A gate in the sodium channel that closes after a short delay, preventing further sodium influx.

Signup and view all the flashcards

What makes nerve and muscle cells excitable?

Nerve and muscle cells generate electrical signals due to changes in membrane permeability, allowing ions to flow across the cell membrane.

Signup and view all the flashcards

What are the triggering events that initiate electrical signals in nerve and muscle cells?

A triggering event can be a chemical messenger binding to a receptor, a stimulus like sound waves, or a change in membrane permeability.

Signup and view all the flashcards

What are the two main types of electrical signals in nerve and muscle cells?

Graded potentials are temporary, localized changes in membrane potential, while action potentials are rapid, long-distance signals that travel along axons.

Signup and view all the flashcards

How are action potentials generated?

Action potentials occur when voltage-gated Na+ and K+ channels open, changing membrane permeability and allowing ion flow.

Signup and view all the flashcards

Describe the phases of an action potential.

Resting potential, depolarization, repolarization, and hyperpolarization are the four phases of an action potential.

Signup and view all the flashcards

Why can't action potentials travel backward?

Action potentials are unidirectional, meaning they travel from the trigger zone to the axon terminal and cannot go backward.

Signup and view all the flashcards

Describe the initial steps of an action potential.

A stimulus depolarizes the cell membrane toward the threshold potential. If threshold is reached, Na+ channels open, causing rapid depolarization.

Signup and view all the flashcards

What happens during the later stages of an action potential?

K+ channels open and K+ leaves the cell, causing repolarization. The membrane becomes hyperpolarized, and the Na+/K+ pump restores the resting potential.

Signup and view all the flashcards

Myelin Sheath Function

The myelin sheath acts as an insulator, preventing the flow of ions across the membrane except at specific points called nodes of Ranvier.

Signup and view all the flashcards

Saltatory Conduction

The process by which action potentials appear to jump from one node of Ranvier to the next in myelinated axons, resulting in faster conduction.

Signup and view all the flashcards

Action Potential Speed

The speed of propagation of an action potential depends on factors like resistance and capacitance within the axon.

Signup and view all the flashcards

Resistance & Conduction Velocity

A decrease in resistance within the axon's core leads to faster action potential propagation.

Signup and view all the flashcards

Capacitance & Conduction Velocity

A decrease in capacitance across the membrane results in faster action potential propagation.

Signup and view all the flashcards

Axon Diameter & Conduction Velocity

Larger axon diameter results in lower internal resistance, leading to faster action potential propagation.

Signup and view all the flashcards

Conduction Velocity Comparison

A comparison illustrating the differences in conduction velocity between myelinated and unmyelinated axons of different sizes.

Signup and view all the flashcards

Action Potential Travel Rate

Action potentials are conducted at varying rates depending on axon diameter and presence of myelin.

Signup and view all the flashcards

Na+ inactivation gate function

The Na+ inactivation gate helps control the flow of sodium ions (Na+) through the channels. It opens slower than the activation gate and closes after a brief period, ensuring that the flow of Na+ is tightly regulated.

Signup and view all the flashcards

Function of K+ channels

K+ channels are crucial for restoring the cell membrane potential back to its resting state after an action potential. They open at a slower rate compared to Na+ channels, allowing K+ to flow out of the cell, repolarizing the membrane.

Signup and view all the flashcards

Na+-K+ ATPase pump function

The Na+-K+ ATPase pump actively transports Na+ ions out of the cell and K+ ions into the cell. This process requires energy and maintains the concentration gradients of Na+ and K+ across the membrane.

Signup and view all the flashcards

What are Graded Potentials?

A graded potential is a localized change in a cell's membrane potential that varies in magnitude according to the strength of the stimulus.

Signup and view all the flashcards

How are Graded Potentials generated?

Graded potentials are primarily driven by the opening and closing of ligand-gated channels, rather than the voltage-gated channels involved in action potentials.

Signup and view all the flashcards

What are Excitatory Postsynaptic Potentials (EPSPs)?”,

Excitatory postsynaptic potentials (EPSPs) are graded potentials that make a postsynaptic neuron more likely to fire an action potential. They are typically caused by the influx of positive ions (Na+ or Ca2+).

Signup and view all the flashcards

What are Inhibitory Postsynaptic Potentials (IPSPs)?

Inhibitory postsynaptic potentials (IPSPs) are graded potentials that make a postsynaptic neuron less likely to fire an action potential. They are typically caused by the influx of negative ions (Cl-) or the efflux of positive ions (K+).

Signup and view all the flashcards

How do graded potentials differ from action potentials?

They are changes in membrane potential that occur in dendrites and cell bodies. They lose strength as they move away from the point of stimulation.

Signup and view all the flashcards

How do graded potentials respond to different stimuli?

A strong stimulus, like a strong light, produces a large graded potential. A weak stimulus, like a faint sound, produces a small graded potential.

Signup and view all the flashcards

What is the trigger zone?

The trigger zone is the region of the neuron where graded potentials are strong enough to initiate an action potential.

Signup and view all the flashcards

Why do graded potentials lose strength?

Current leak and cytoplasmic resistance cause graded potentials to lose strength.

Signup and view all the flashcards

How does axon diameter affect conduction speed?

A larger axon diameter allows for faster action potential conduction.

Signup and view all the flashcards

How does membrane resistance affect conduction speed?

A more leak-resistant membrane allows for faster action potential conduction.

Signup and view all the flashcards

Study Notes

1-The Nervous System

  • The nervous system is a communication and control system regulating vital human body functions.
  • It receives information from the environment and the body, interprets it, and causes the body to respond.
  • The system is responsible for sensing stimuli such as temperature, taste, and texture, and processing emotional responses, including happiness, sadness, and anger.
  • It regulates multiple human functions including movement, feeding, digestion, breathing and more.
  • The building unit of the nervous system is the neuron.

2-The Neuron

  • The cell body contains the nucleus, cytoplasm and plasma membrane.
  • Dendrites extend from the cell body, connecting to other neurons. Dendrites receive information.
  • The axon is a cylindrical structure covered by a myelin sheath, sending information to other neurons.
  • Axon terminals are nerve endings; they send information to the next neuron; or muscle or gland.
  • A synapse is a chemical junction between the axon terminal of one neuron and the dendrites of another neuron.

3-Neural Communication

  • All body cells have a membrane potential; a separation of positive and negative charges across the membrane, related to the unequal distribution of ions, and selective permeability of the plasma membrane.
  • Neurons and muscle cells can change their membrane potentials rapidly, acting as electrical signals in response to stimulation.
  • A triggering event may be a chemical messenger interacting with the membrane's receptor, a stimulus (sound waves in the ears), or a change in ion channel permeability.

4-Electrical Signals

  • Electrical signals are graded potentials and action potentials.
  • Ion channels, including leak channels, voltage-gated channels, and ligand-gated channels, are essential in maintaining membrane potential.

4.1-Action potential.

  • Ion permeability and movement: Voltage-gated ion channels open, changing the membrane's permeability to Na+ and K+, and creating the action potential.
  • Phases of action potentials; Resting potential, depolarization, repolarization, and back to resting potential.
  • Action potentials move in one direction.

4.2. Refractory Period

  • The refractory period is the time after an action potential when the nerve cell cannot generate another action potential.
  • Two phases of refractory period exist: absolute and relative refractory period.

4.3-Na+ Channels Gates

  • Na+ channels maintain membrane potential and have two gates for regulating Na+ movement, the activation gate and the inactivation gate.
  • Action potentials are caused by the rapid opening and closing of these two gates.

4.4-K+ Channels Gates

  • K+ channels are responsible for the repolarization phase of the action potential.

4.5-The Na+-K+ ATPase pump

  • The Na+/K+ pump maintains the resting potential by actively transporting 3 sodium ions out of the cell and bringing 2 potassium ions in.

5-Graded Potentials

  • A graded potential results from a ligand-gated channel opening; it is a change in voltage based on the stimulus; it has varying degrees and moves short distances.
  • Graded potentials can be excitatory (depolarizing) or inhibitory (hyperpolarizing), depending on the ions involved.
  • Graded potentials lose strength as they travel due to current leak and cytoplasmic resistance.
  • Graded potentials that reach the threshold at the trigger zone initiate an action potential.

6-Neurons Conduction Velocity in unmyelinated axon

  • Two factors influence the speed of action potential conduction in a unmyelinated axon.
  • Axon diameter and resistance to leakage of ions in the core.

7-Conduction in Myelinated Axons

  • Myelinated axons limit contact with the extracellular fluid, increasing resistance and velocity.
  • Action potentials in myelinated axons jump between nodes of Ranvier.

8-Conduction Velocity in Myelinated Axons

  • Two factors influence the speed of propagation: resistance within the axon core and capacitance across the membrane.
  • Larger axon diameters decrease internal resistance; decreasing capacitance increases velocity.

9-Examples of Conduction (action potential) velocity

  • Myelinated axons can propagate action potentials much faster than unmyelinated axons.

10-Nerve Disease

  • In demyelinating diseases, loss of myelin in neurons slows action potential conduction and may lead to conduction failure.
  • Multiple sclerosis is a common demyelinating disease that causes various neurological problems.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Electrical Biophysical Approach in Nervous System PDF

Description

Explore the intricate workings of the nervous system and its fundamental building block, the neuron. This quiz covers how the nervous system regulates body functions, processes stimuli, and enables emotional responses. Test your knowledge on the structure and function of neurons and their roles in communication within the body.

More Like This

Biology Nervous System Overview
48 questions

Biology Nervous System Overview

SaneStatistics avatar
SaneStatistics
Nervous System Overview and Neurons
5 questions

Nervous System Overview and Neurons

TopsSphinx avatar
TopsSphinx
Biología y Psiquis Humana - Tema 2
21 questions

Biología y Psiquis Humana - Tema 2

SkilledBeryllium7802 avatar
SkilledBeryllium7802
Human Biology: Central Nervous System
45 questions

Human Biology: Central Nervous System

SimplerPlatinum798 avatar
SimplerPlatinum798
Use Quizgecko on...
Browser
Open
Browser
Browser