Human Anatomy & Physiology: Neurons & Nerve Transmission
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Questions and Answers

What primary role does the Na+ - K+ ATPase pump play in neuronal function?

  • It initiates action potentials in myelinated axons.
  • It enhances the propagation speed of signals along the axon.
  • It converts graded potentials into action potentials.
  • It restores intracellular ion concentrations after overshoot. (correct)

In which state can the axon hillock region not generate an action potential?

  • While neurotransmitter receptors are activated.
  • After the peak of action potential.
  • At the onset of graded potential.
  • During the absolute refractory period. (correct)

Which characteristic distinguishes saltatory conduction from continuous conduction in axons?

  • It relies solely on the diameter of axons.
  • It produces a signal that degrades faster than in continuous conduction.
  • It occurs only in non-myelinated axons.
  • It involves the jump of action potentials from node to node. (correct)

What type of ion channels are primarily responsible for generating action potentials?

<p>Voltage gated ion channels. (D)</p> Signup and view all the answers

What is the effect of myelination on the speed of action potential propagation?

<p>Increases the speed and decreases energy usage. (A)</p> Signup and view all the answers

What is the primary function of sensory neurons?

<p>To deliver information from external stimuli (D)</p> Signup and view all the answers

Which neuroglia cell type in the CNS is primarily responsible for forming the blood-brain barrier?

<p>Astrocyte (A)</p> Signup and view all the answers

What role does the myelin sheath play in nerve transmission?

<p>It enhances the speed of nerve transmission. (D)</p> Signup and view all the answers

Which of the following correctly identifies the structural classification of a neuron with two processes?

<p>Bipolar (A)</p> Signup and view all the answers

What is the primary function of ependymal cells in the central nervous system?

<p>To line fluid-filled cavities and produce cerebrospinal fluid (C)</p> Signup and view all the answers

Which statement best describes a node of Ranvier?

<p>It is a gap in the myelin sheath that allows for faster signal conduction. (A)</p> Signup and view all the answers

Which function is associated with Schwann cells in the peripheral nervous system?

<p>Myelinating axons to speed up nerve transmission (B)</p> Signup and view all the answers

Which part of the neuron is responsible for releasing neurotransmitters?

<p>Axon terminal (D)</p> Signup and view all the answers

Which structure is responsible for releasing neurotransmitters at the synapse?

<p>Axon terminal (D)</p> Signup and view all the answers

What happens to the neurotransmitter acetylcholine (Ach) after it binds to the receptor on the post synaptic cell?

<p>It is degraded by acetylcholine esterase. (B)</p> Signup and view all the answers

Which component of the synapse is described as the extracellular space?

<p>Synaptic cleft (D)</p> Signup and view all the answers

During synaptic transmission, what triggers the fusion of vesicles containing neurotransmitter with the cell membrane?

<p>Calcium ion influx (D)</p> Signup and view all the answers

The depolarization resulting from neurotransmitter binding can result in which of the following?

<p>An excitatory postsynaptic potential (EPSP) (C)</p> Signup and view all the answers

Which component of the neuromuscular junction contains receptors for neurotransmitters?

<p>Skeletal muscle effector (D)</p> Signup and view all the answers

What is one role of neuroglia in the nervous system?

<p>Providing structural support (B)</p> Signup and view all the answers

What term describes the interaction between a neurotransmitter and its receptor?

<p>Key and lock interaction (A)</p> Signup and view all the answers

Which type of ion channel is primarily involved in the depolarization of the post synaptic neuron upon neurotransmitter binding?

<p>Sodium gated channels (A)</p> Signup and view all the answers

What is the primary function of the synaptic cleft in neurotransmission?

<p>To provide a space for neurotransmitter diffusion (C)</p> Signup and view all the answers

What occurs in the axon hillock region of a neuron?

<p>Graded potentials are summed to determine if the threshold is reached. (A)</p> Signup and view all the answers

Which of the following accurately describes the role of neurotransmitters in nerve transmission?

<p>They can have stimulatory or inhibitory effects depending on the receptor type. (C)</p> Signup and view all the answers

What is the primary function of the myelin sheath in a neuron?

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

In which part of the neuron does an action potential form?

<p>Axon hillock (A)</p> Signup and view all the answers

What is the role of calcium ions in the process of neurotransmitter release?

<p>They trigger vesicle fusion in the axon terminal. (C)</p> Signup and view all the answers

What characterizes an inhibitory postsynaptic potential (IPSP)?

<p>It makes the postsynaptic neuron less likely to fire an action potential. (C)</p> Signup and view all the answers

What is the main difference between temporal and spatial summation in neurons?

<p>Temporal summation refers to rapid firing of one presynaptic neuron, while spatial summation involves different neurons. (C)</p> Signup and view all the answers

During nerve transmission, what effect does an action potential have on the postsynaptic neuron?

<p>It results in a graded potential due to neurotransmitter binding. (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of neuroglia?

<p>They are capable of generating action potentials. (D)</p> Signup and view all the answers

Which structure in a neuron is primarily responsible for receiving information?

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

What is the primary function of neuroglia in the nervous system?

<p>Support and protect neurons (A)</p> Signup and view all the answers

The myelin sheath is crucial for which of the following processes?

<p>Saltatory conduction of action potentials (C)</p> Signup and view all the answers

Which component forms the junction between two neurons, facilitating neurotransmission?

<p>Synapse (B)</p> Signup and view all the answers

Which structure at the end of an axon contains synaptic vesicles filled with neurotransmitters?

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

What is the role of the axon hillock in neuron function?

<p>Integrate incoming signals and initiate action potentials (D)</p> Signup and view all the answers

What specifically constitutes Nissl bodies within a neuron?

<p>Clusters of ribosomes and rough endoplasmic reticulum (A)</p> Signup and view all the answers

At the neuromuscular junction, the neurotransmitter primarily involved in muscle contraction is?

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

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

<p>Graded potentials can vary in amplitude, whereas action potentials are all-or-nothing. (A)</p> Signup and view all the answers

Which type of ion channel is primarily involved in generating an action potential?

<p>Voltage-gated channels (C)</p> Signup and view all the answers

Flashcards

Action Potential Propagation

The way an electrical signal travels down an axon, where a series of depolarizations and repolarizations occur in a chain reaction.

Saltatory Conduction

A faster and more energy-efficient form of action potential propagation that occurs in myelinated axons, where the signal jumps between nodes of Ranvier.

Refractory Period

The time period after an action potential where the neuron is unable to fire another action potential, ensuring unidirectional transmission.

Graded Potential vs. Action Potential

Graded potentials are localized changes in membrane potential that can vary in magnitude and duration, while action potentials are all-or-none events with a fixed magnitude and duration.

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Integration at Axon Hillock

The summation of all graded potentials occurring at the axon hillock, where the decision to fire an action potential is made based on the overall signal strength.

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Synapse

The junction between two neurons or a neuron and a muscle cell, where signals are transmitted.

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Axon terminal

The end of an axon where neurotransmitters are released.

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Synaptic cleft

The space between the axon terminal of one neuron and the dendrite or cell body of another neuron (or muscle cell).

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Neurotransmitter

A chemical messenger that transmits signals across a synapse.

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Motor end plate

The region of a muscle cell membrane that receives signals from a motor neuron.

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Action potential arrival

The signal that triggers the release of neurotransmitters at the synapse.

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Calcium ions

Ions that trigger the release of neurotransmitters from vesicles.

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Vesicle

A small sac that stores and releases neurotransmitters.

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Receptor

A protein on the postsynaptic neuron (or muscle cell) that binds to neurotransmitters.

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Depolarization

A change in membrane potential that makes the inside of the cell more positive, potentially triggering an action potential.

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What are neurotransmitters?

Neurotransmitters are chemical signals that transmit information between neurons at synapses.

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What are the 3 types of structural neurons?

Neurons are classified based on their structure: Unipolar neurons have one process, Bipolar neurons have two processes, and Multipolar neurons have many processes.

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What is the function of an interneuron?

Interneurons connect and integrate signals between other neurons, making decisions in the nervous system.

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What is the role of neuroglia?

Neuroglia, also known as glial cells, support and protect neurons in the nervous system.

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What is the function of an astrocyte?

Astrocytes provide structural support, regulate the chemical environment of neurons, and form the blood-brain barrier.

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What is the function of the myelin sheath?

The myelin sheath acts as an insulator around axons, increasing the speed of nerve impulse transmission.

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What is the function of Schwann cells?

Schwann cells produce the myelin sheath around axons in the peripheral nervous system (PNS).

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What is the function of the node of Ranvier?

Nodes of Ranvier are gaps along the myelin sheath that allow for faster nerve impulse transmission, as well as the formation of collateral branches.

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What are the main functions of a neuron?

Neurons are responsible for receiving and transmitting electrical impulses throughout the body, enabling communication between different parts of the nervous system.

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What is the cell body of a neuron called?

The cell body, also known as the soma, is the central part of a neuron that contains the nucleus and other essential organelles.

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What are Nissl bodies?

Nissl bodies are clusters of rough endoplasmic reticulum (RER) found within the cell body of a neuron, responsible for protein synthesis.

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What is the function of dendrites?

Dendrites are branching extensions of the neuron that receive information from other neurons or sensory receptors.

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What is the function of an axon?

The axon is a long, slender projection of the neuron that transmits information from the cell body to other neurons, muscles, or glands.

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What is the axon hillock?

The axon hillock is the region where the axon emerges from the cell body and where integration of incoming signals occurs.

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What are telodendria?

Telodendria are fine branches at the distal end of the axon that form synapses with other neurons or target cells.

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What are the main types of gated ion channels?

There are three primary types of gated ion channels: ligand-gated, voltage-gated, and mechanically gated. Each type opens in response to specific stimuli.

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What is the difference between graded and action potentials?

Graded potentials are short-distance signals that vary in strength, while action potentials are long-distance signals of a fixed strength.

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What is saltatory conduction?

Saltatory conduction is the rapid transmission of action potentials along myelinated axons, where the signal jumps from one node of Ranvier to the next.

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What are the effects of neurotransmitters?

Neurotransmitters can either excite (stimulatory) or inhibit (inhibitory) the receiving neuron.

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What determines the effect of a neurotransmitter?

The effect of a neurotransmitter depends on the type of receptor it binds to on the receiving neuron.

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What are graded potentials?

Small, temporary changes in membrane potential that occur in the dendrites and cell body of a neuron.

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What is the difference between IPSP and EPSP?

IPSP (Inhibitory Postsynaptic Potential) makes a neuron less likely to fire an action potential, while EPSP (Excitatory Postsynaptic Potential) makes it more likely to fire.

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What is integration?

The process of summing up all the incoming graded potentials at the axon hillock to determine whether or not to fire an action potential.

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What is the threshold?

The minimum level of stimulation required to initiate an action potential.

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What is an action potential?

A rapid, brief reversal of membrane potential that travels down the axon of a neuron.

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How does an action potential cause neurotransmitter release?

The arrival of an action potential at the axon terminal opens calcium channels, causing the release of neurotransmitters from synaptic vesicles.

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What is a serial circuit?

A neuron circuit where information flows in a single, linear path from one neuron to the next.

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Study Notes

Neurone & Nerve Transmission

  • Course: Human Anatomy & Physiology
  • Status: Complete
  • Materials: 3. The Neuron and Nerve Transmission - Slides

The Neuron

  • Function: Receives and transmits electrical impulses
  • Structure: Cell body and processes
  • Nissl bodies: Clusters of RER
  • Neurofibrils: Cytoskeletal elements for shape
  • Dendrites: Receive information
  • Axon: Sends information
  • Collateral: Branch off of axon
  • Axon hillock: Integration area
  • Telodendria: Branches at the distal end of axon

Neuron Classification

  • Structural: Based on the number of processes on the cell body
    • Unipolar: One process
    • Bipolar: Two processes
    • Multipolar: Many processes
  • Functional: Based on function
    • Sensory (1): Delivers information
    • Inter or Association (2): Makes a decision
    • Motor (3): Sends information to muscles

Neuroglia

  • In the CNS:
    • Astrocyte: Provides 3-D framework and controls the environment (forms the blood-brain barrier)
    • Oligodendrocyte: Myelin sheath of the CNS
    • Microglia: Immune function
  • In the PNS:
    • Satellite cell: Same function as astrocyte

Myelin Sheath

  • Structure: Multiple membrane layers wrapping around the axon
  • CNS: Oligodendrocyte
  • PNS: Schwann cell
  • Function:
    • Protect and insulate
    • Increase speed of nerve transmission
  • Node of Ranvier: Gaps along the myelin sheath
    • Where collaterals arise
    • Nerve impulse is transmitted

Nerve Transmission

  • Membrane Potential: Unequal charge difference across a membrane
  • Resting membrane potential for most cells is -70mV
  • A membrane potential occurs because:
    • Membranes are barriers to charges (ions)
    • Sodium-potassium ATPase pump establishes and maintains ion gradients resulting in
      • High potassium inside the cell
      • High sodium outside the cell
    • Negatively charged proteins inside the cell
      • Membranes leak so the pump is always on
  • Changes in membrane potential are used to create a signal
    • Occurs when gated ion channels open or close, and ions move down their gradients
    • A few ions move across rapidly
    • lon concentration changes are corrected by the sodium-potassium ATPase pump

Types of Gated Ion Channels

  • Chemically regulated
  • Voltage regulated
  • Mechanically regulated
  • Light regulated
  • Others

Terms used to describe changes in membrane potential

  • Rest or Resting state: -70mV
  • Polarized: The resting membrane potential (-70mV)
  • Depolarization: Potential becomes more positive (less polar)
  • Hyperpolarization: Potential becomes more negative (more polar)
  • Repolarization: Becomes more negative returning to rest
  • Hyper-repolarization: Becomes more negative than -70mV

Location of gated ion channels

  • Chemically gated Na⁺ or K⁺: Cell body and dendrites
  • Voltage gated Na⁺ and K⁺: Axon
  • Voltage gated Ca²⁺: Axon terminal

Types of Changes in Potential

  • Graded Potential: Due to chemical gates, occurs along the cell body and dendrites.
  • Action Potential: Due to voltage gates, occurs along the axon. Can vary in magnitude, and may be depolarization or hyperpolarization.

Action Potential

  • Action Potential: All-or-none response resulting in depolarization and repolarization
  • Note parts of the graph:
    • Threshold
    • Depolarization
    • Repolarization
    • Absolute refractory period
    • Relative refractory period
    • Resting membrane potential
    • Stimulus

Steps in Action Potential Formation

  • Stimulus brings membrane to threshold, opening sodium voltage-gated ion channels
  • Sodium moves in, bringing membrane to +30mV (depolarization).
  • At +30mV, potassium voltage-gated channels open and sodium voltage-gated ion channels close.
  • Potassium ion moves out, repolarizing the membrane

Transmission of outgoing signals

  • Occurs by propagation
    • Events creating change in potential are repeated along the axon
  • Steps:
    • Graded potential of +30mV forms in axon hillock region
    • Local current depolarizes adjacent segment bringing sodium voltage gates to threshold
    • Action potential forms while hillock region enters refractory period
    • Cycle repeats until reaching axon terminal

Saltatory Conduction

  • Occurs in myelinated axons
  • Myelin resists flow of ions

The Synapse

  • Components:
    • Axon terminal (filled with vesicles containing neurotransmitter)
    • Synaptic cleft (extracellular space between)
    • Motor end plate (contains receptors for neurotransmitters or chemically gated ion channels)

Steps at the Synapse

  • Action potential arrives
  • Voltage calcium gates open and calcium ion moves in
  • Calcium triggers fusion of vesicles with the cell membrane, releasing neurotransmitter
  • Neurotransmitter binds to receptors on the postsynaptic neuron or muscle (forming EPSP or IPSP)
  • Depolarization (graded potential or EPSP) may or may not generate an action potential

The Neurotransmitter (NT)

  • 50-100 different types of neurotransmitters
  • Lock and key interaction
  • Each neuron is exposed to a variety of NT
  • Effects are stimulatory or inhibitory
  • Response depends on receptor

Neuron Circuits

  • Types of neuron circuits
    • Diverging
    • Converging
    • Reverberating
    • Parallel after-discharge

Nerve Transmission Summary

  • Sensory signal: IPSP and EPSP, graded potentials are summed temporally or spatially in the axon hillock.
  • Motor signal: If threshold is reached in axon hillock region, action potential forms in the axon, Action potential propagates along the axon, Action potential opens calcium channels in axon terminal, Calcium triggers vesicle fusion, Transmitter is released, NT binds postsynaptic neuron or muscle, forming a graded potential.

Neuro Musclar Junction

Information about neuro-muscular junctions and steps.

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Human Anatomy & Physiology: The Neurone & Nerve Transmission PDF

Description

This quiz covers key aspects of neurons and nerve transmission in human anatomy and physiology. Learn about the structure and function of different types of neurons, their classifications, and the role of neuroglia. Test your knowledge on the foundational concepts relevant to the nervous system.

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