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?

Voltage gated ion channels. Signup and view all the answers

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

Increases the speed and decreases energy usage. Signup and view all the answers

What is the primary function of sensory neurons?

To deliver information from external stimuli Signup and view all the answers

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

Astrocyte Signup and view all the answers

What role does the myelin sheath play in nerve transmission?

It enhances the speed of nerve transmission. Signup and view all the answers

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

Bipolar Signup and view all the answers

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

To line fluid-filled cavities and produce cerebrospinal fluid Signup and view all the answers

Which statement best describes a node of Ranvier?

It is a gap in the myelin sheath that allows for faster signal conduction. Signup and view all the answers

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

Myelinating axons to speed up nerve transmission Signup and view all the answers

Which part of the neuron is responsible for releasing neurotransmitters?

Axon terminal Signup and view all the answers

Which structure is responsible for releasing neurotransmitters at the synapse?

Axon terminal Signup and view all the answers

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

It is degraded by acetylcholine esterase. Signup and view all the answers

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

Synaptic cleft Signup and view all the answers

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

Calcium ion influx Signup and view all the answers

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

An excitatory postsynaptic potential (EPSP) Signup and view all the answers

Which component of the neuromuscular junction contains receptors for neurotransmitters?

Skeletal muscle effector Signup and view all the answers

What is one role of neuroglia in the nervous system?

Providing structural support Signup and view all the answers

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

Key and lock interaction 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?

Sodium gated channels Signup and view all the answers

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

To provide a space for neurotransmitter diffusion Signup and view all the answers

What occurs in the axon hillock region of a neuron?

Graded potentials are summed to determine if the threshold is reached. Signup and view all the answers

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

They can have stimulatory or inhibitory effects depending on the receptor type. Signup and view all the answers

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

To increase the speed of action potential propagation. Signup and view all the answers

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

Axon hillock Signup and view all the answers

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

They trigger vesicle fusion in the axon terminal. Signup and view all the answers

What characterizes an inhibitory postsynaptic potential (IPSP)?

It makes the postsynaptic neuron less likely to fire an action potential. Signup and view all the answers

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

Temporal summation refers to rapid firing of one presynaptic neuron, while spatial summation involves different neurons. Signup and view all the answers

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

It results in a graded potential due to neurotransmitter binding. Signup and view all the answers

Which of the following is NOT a characteristic of neuroglia?

They are capable of generating action potentials. Signup and view all the answers

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

Dendrites Signup and view all the answers

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

Support and protect neurons Signup and view all the answers

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

Saltatory conduction of action potentials Signup and view all the answers

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

Synapse Signup and view all the answers

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

Telodendria Signup and view all the answers

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

Integrate incoming signals and initiate action potentials Signup and view all the answers

What specifically constitutes Nissl bodies within a neuron?

Clusters of ribosomes and rough endoplasmic reticulum Signup and view all the answers

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

Acetylcholine Signup and view all the answers

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

Graded potentials can vary in amplitude, whereas action potentials are all-or-nothing. Signup and view all the answers

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

Voltage-gated channels Signup and view all the answers

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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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.