Nervous System Overview and Neurons
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Questions and Answers

What are the primary functions of the nervous system in the body?

The primary functions include processing sensory information, coordinating movement, and facilitating communication between different body parts.

How do sensory cells contribute to the generation of graded potentials?

Sensory cells convert external stimuli into electrical signals, creating graded potentials that vary in magnitude based on the strength of the stimulus.

What role do neurotransmitters play in synaptic transmission?

Neurotransmitters are chemical messengers that transmit signals across synapses from one neuron to another, facilitating communication.

Describe the significance of graded potentials in the nerve cell body.

<p>Graded potentials in the nerve cell body are crucial for integrating incoming signals and determining whether to generate an action potential.</p> Signup and view all the answers

What is the process of propagation of action potentials in nerve cell axons?

<p>Action potentials propagate along axons through the opening and closing of voltage-gated ion channels, resulting in a wave of depolarization.</p> Signup and view all the answers

Why do action potentials propagate in one direction?

<p>Action potentials propagate in one direction due to the refractory period, where previously activated regions of the axon cannot generate another action potential.</p> Signup and view all the answers

What is the role of neuroglia in the nervous system?

<p>Neuroglia support neurons by providing structural support, insulation, and nutrient supply, as well as participating in signal transmission.</p> Signup and view all the answers

How do additional synapses and neuronal circuits influence the nervous system's functionality?

<p>Additional synapses and neuronal circuits enhance the complexity and flexibility of neural processing, allowing for more sophisticated responses.</p> Signup and view all the answers

What causes the rapid influx of Na+ during an action potential?

<p>The rapid influx of Na+ is caused by a large Na+ concentration gradient and a significant electrical gradient.</p> Signup and view all the answers

What is the membrane potential at the peak of an action potential and why does it occur?

<p>The membrane potential at the peak of an action potential is +30 mV, occurring due to the opening of Na+ channels and the influx of Na+.</p> Signup and view all the answers

Describe the movement of K+ during repolarization and the factors influencing it.

<p>K+ moves out of the cell during repolarization due to a large K+ concentration gradient and a significant electrical gradient favoring efflux.</p> Signup and view all the answers

How does the Na+/K+ pump contribute to the restoration of resting membrane potential (RMP)?

<p>The Na+/K+ pump restores resting membrane potential by actively transporting Na+ out of the cell and K+ into the cell, maintaining their gradients.</p> Signup and view all the answers

Explain the significance of myelin sheaths in the propagation of action potentials.

<p>Myelin sheaths increase the speed of action potential propagation by enabling saltatory conduction, allowing signals to jump between nodes of Ranvier.</p> Signup and view all the answers

What type of receptor detects changes in muscle length?

<p>Stretch receptors</p> Signup and view all the answers

Explain how the propagation of information differs between graded potentials and action potentials.

<p>Graded potentials travel short distances and are local changes in membrane potential, while action potentials can travel longer distances at high speeds.</p> Signup and view all the answers

What role do neurotransmitters play at synapses?

<p>Neurotransmitters are released from the pre-synaptic cell and bind to receptors on the post-synaptic cell to facilitate information transfer.</p> Signup and view all the answers

What type of sensory cell detects photons of light?

<p>Visual receptors</p> Signup and view all the answers

How do sensory cells generate graded potentials?

<p>Sensory cells generate graded potentials through membrane potential changes in response to stimuli.</p> Signup and view all the answers

What is the maximum speed at which an action potential can travel in an axon?

<p>Up to approximately 100 meters per second</p> Signup and view all the answers

Why do graded potentials typically not travel long distances?

<p>Graded potentials diminish in strength as they spread from their point of origin.</p> Signup and view all the answers

What ions do salt taste buds specifically detect?

<p>Sodium ions (Na+)</p> Signup and view all the answers

Describe the quickness of neurotransmitter information transfer at synapses.

<p>Neurotransmitter information transfer is very quick, occurring by diffusion across the synaptic cleft.</p> Signup and view all the answers

What component of the nerve cell also acts as a sensory cell?

<p>The cell body of a nerve cell</p> Signup and view all the answers

What is the approximate speed of a nerve impulse in kilometers per hour?

<p>The speed of a nerve impulse is approximately 360 km/h.</p> Signup and view all the answers

Compare the speed of nerve impulses to that of copper wire.

<p>Nerve impulses are 3 x 10^6 times slower than copper wire.</p> Signup and view all the answers

What is the speed of diffusion mentioned in the content?

<p>The speed of diffusion is 0.000000008 km/h.</p> Signup and view all the answers

How is the speed of nerve impulses quantified in the context provided?

<p>Nerve impulse speed is quantified as 1 metre per 100 milliseconds.</p> Signup and view all the answers

What does the notation -55 mV represent in the context of nerve impulses?

<p>-55 mV represents the threshold potential needed to initiate an action potential.</p> Signup and view all the answers

What is the physiological significance of sodium ion (Na+) concentration in nerve impulses?

<p>Sodium ions (Na+) play a crucial role in depolarizing the neuron's membrane during an action potential.</p> Signup and view all the answers

Analyze the rate at which nerve impulses travel compared to the speed of sound.

<p>Nerve impulses travel at about 360 km/h, much slower than the speed of sound.</p> Signup and view all the answers

In what way is the speed of nerve impulses slower than typical electronic signals?

<p>Nerve impulses are 3 x 10^6 times slower than the speed of electrical signals in copper wire.</p> Signup and view all the answers

What key factor contributes to the significant difference in speed between nerve impulses and diffusion?

<p>The organized structure of neurons and myelination significantly enhances the speed of nerve impulses compared to diffusion.</p> Signup and view all the answers

Explain the implications of nerve impulse speed for human reflexes.

<p>The speed of nerve impulses allows for quick reflex actions, essential for survival.</p> Signup and view all the answers

What is the threshold potential that triggers the opening of voltage-gated Na+ channels?

<p>-55 mV</p> Signup and view all the answers

Describe the direction of ion movement during the initial phase of action potential generation.

<p>Na+ ions move into the cell.</p> Signup and view all the answers

What happens to the membrane potential when graded potentials increase it to -55 mV?

<p>It triggers an action potential.</p> Signup and view all the answers

What is the resting membrane potential (RMP) of a neuron?

<p>-70 mV</p> Signup and view all the answers

Identify the type of channels responsible for the rapid changes in membrane potential during action potentials.

<p>Voltage-gated Na+ and K+ channels.</p> Signup and view all the answers

What occurs at approximately +30 mV during action potential depolarization?

<p>Na+ channels begin to close.</p> Signup and view all the answers

Explain the role of graded potentials in neuron excitability.

<p>Graded potentials can depolarize the membrane to the threshold.</p> Signup and view all the answers

During the resting state, which ion is primarily responsible for maintaining the negative internal charge of the neuron?

<p>K+ ions.</p> Signup and view all the answers

What effect does an increase in Na+ permeability have on the membrane potential?

<p>It causes depolarization.</p> Signup and view all the answers

What metric indicates the change from a resting state to an active firing state in neurons?

<p>Action potential.</p> Signup and view all the answers

Study Notes

Nervous System – Overview

  • The nervous system controls muscle stretch receptors, senses external and internal environments, and makes decisions affecting muscle function, cardiac function, and other systems, including the gastrointestinal system.

Nervous System – Three Types of Neuron

  • There are three main types of neurons: sensory, interneuron, and motor.

Neurons and Neuronal Circuits – Overview

  • Virtually all sensory systems have a sensory cell that releases neurotransmitters when activated.
  • Sensory cells can detect various stimuli:
    • Sweet taste buds detect glucose and other molecules that bind to a “sweet” receptor.
    • Salt taste buds detect Na+ ions in saliva.
    • Visual receptors detect photons of light
    • Stretch receptors detect changes in muscle length.

Nerve Impulse Transmission – The Role of Ion Channels

  • Sensory cells generate graded potentials - as the stimulus increases, the membrane potential also increases.
  • Graded potentials travel short distances through diffusion.
  • Synapses release neurotransmitters (NTs) from the pre-synaptic cell, resulting in the quick transmission of information across a short distance.
  • NTs bind to the post-synaptic cell and affect its membrane potential.
  • The cell body of a nerve gathers information from dendrites.
  • Graded potentials are also generated in the nerve cell body.

Nerve Impulse Transmission – Axons

  • Axons conduct action potentials (APs) which allow for information to travel much longer distances - up to 100m/second - and significantly quicker than across the cell body or synapse.

Nerve Impulse Transmission – Synapses

  • Synapses release NTs from the pre-synaptic cell and transmit information across a short distance by diffusion.

Graded Potentials

  • Graded potentials are changes in membrane potential which can occur in sensory cells and the cell body of a neuron.
  • They don't follow the all-or-nothing principle and their magnitude can vary depending on the strength of the stimulus. They are also local and decay over distance.

Action Potentials

  • Action potentials (APs) are rapid changes in membrane potential, created by the opening and closing of voltage-gated Na+ and K+ channels in the axon.

Resting Membrane Potential (RMP)

  • The inside cell is negative, relative to the outside -70 mV.
  • The RMP is maintained by the Na+/K+ pump.

Action Potential Mechanism

  • When the membrane potential reaches -55 mV, Na+ channels open and Na+ influx occurs, causing a rapid rise in membrane potential to 30 mV.
  • At peak voltage of +30 mV, Na+ channels close.
  • When K+ channels open, K+ efflux rapidly drops membrane potential to -90 mV.
  • The Na+/K+ pump helps reset the RMP to the resting membrane potential.

Nerve Impulses – Key Points

  • Impulses can travel at very high speeds (100 m/s).
  • The speed of nerve impulses is significantly faster than copper wire conduction or diffusion.

Lecture 7 Summary

  • This lecture focuses on the role of neuroglia (specifically myelin sheaths), synaptic transmission, and neuronal circuits.
  • Key topics include explaining the propagation of APs, the role of neuroglia, specialized sensory cells, and the mechanism of synaptic transmission.
  • Also covers how local anesthetics and neurotoxins affect the nervous system.

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Description

Explore the intricacies of the nervous system, including its role in controlling muscle and sensory functions. Learn about the three types of neurons and how nerve impulse transmission occurs through ion channels. This quiz will test your understanding of these fundamental concepts in neurobiology.

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