Introductory Physiology Lectures
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Questions and Answers

What role does the Na+ gradient play in the rapid influx of Na+ during an action potential?

The Na+ gradient is large, which contributes to the rapid influx of Na+ into the cell.

Explain the significance of the K+ efflux during the repolarization phase of an action potential.

The efflux of K+ decreases the membrane potential back towards the resting state, contributing to repolarization.

How does the Na+/K+ pump assist in restoring the resting membrane potential after an action potential?

The Na+/K+ pump expels 3 Na+ ions out and brings 2 K+ ions in, re-establishing the ion concentration gradients.

What mechanism ensures that action potentials propagate in one direction along the axon?

<p>The inactivation of Na+ channels following depolarization prevents reverse propagation of the action potential.</p> Signup and view all the answers

Describe the role of myelin sheath in the propagation of action potentials.

<p>The myelin sheath increases the speed of action potential propagation by providing insulation and facilitating saltatory conduction.</p> Signup and view all the answers

What is the primary function of the nervous system?

<p>The primary function of the nervous system is to communicate information throughout the body and coordinate its actions.</p> Signup and view all the answers

How do sensory cells contribute to the detection of stimuli?

<p>Sensory cells detect stimuli by converting external signals into graded potentials.</p> Signup and view all the answers

What role do neurotransmitters play at synapses?

<p>Neurotransmitters transmit signals across synapses, facilitating communication between neurons.</p> Signup and view all the answers

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

<p>Graded potentials are significant as they can summate to reach the threshold for generating action potentials.</p> Signup and view all the answers

What is the importance of action potentials in nerve cell axons?

<p>Action potentials are crucial for the rapid transmission of electrical signals along the axon.</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 of sodium channels and the role of neuroglia.</p> Signup and view all the answers

What is the impact of neuronal circuits on synaptic transmission?

<p>Neuronal circuits enhance synaptic transmission by allowing complex processing and integration of signals.</p> Signup and view all the answers

Define the role of muscle stretch receptors in the nervous system.

<p>Muscle stretch receptors play a critical role in sensing changes in muscle length and send that information to the nervous system.</p> Signup and view all the answers

What is the approximate speed of nerve impulses in Km/h?

<p>360 Km/h</p> Signup and view all the answers

How does the speed of nerve impulses compare to a copper wire?

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

At what speed does diffusion occur compared to nerve impulses?

<p>Diffusion occurs at 0.000000008 Km/h.</p> Signup and view all the answers

What is the primary ion involved in the generation of action potentials in neurons?

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

What voltage range is typically associated with the resting membrane potential of a neuron?

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

What is the formula used to convert the speed of nerve impulses to a speed over time?

<p>1 m / 100 s</p> Signup and view all the answers

What is the relationship between the speed of nerve impulses and the distance they can travel in an hour?

<p>Nerve impulses can travel 360,000 meters in an hour.</p> Signup and view all the answers

How does the conduction speed of nerve impulses compare to that of diffusion?

<p>Nerve impulses are approximately 4 x 10^10 times faster than diffusion.</p> Signup and view all the answers

Why is the speed of nerve impulses critical for bodily functions?

<p>It allows for rapid communication between different parts of the body.</p> Signup and view all the answers

What does the term 'mechanism' refer to in the context of nerve impulses?

<p>It refers to the physiological processes involved in transmitting nerve signals.</p> Signup and view all the answers

What is the threshold potential that must be reached for Na+ channels to open?

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

Explain the significance of graded potentials in relation to action potentials.

<p>Graded potentials contribute to depolarizing the membrane to the threshold level needed to trigger action potentials.</p> Signup and view all the answers

What is the resting membrane potential (RMP) in neurons?

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

How do voltage-gated Na+ and K+ channels contribute to changes in membrane potential?

<p>These channels allow Na+ to flow into the cell and K+ to flow out, causing rapid depolarization and repolarization.</p> Signup and view all the answers

What occurs at the peak of an action potential?

<p>The membrane potential reaches +30 mV, indicating a maximal depolarization.</p> Signup and view all the answers

Define graded potentials and their role in neuronal signaling.

<p>Graded potentials are changes in membrane potential that vary in size and can lead to action potentials if they reach the threshold.</p> Signup and view all the answers

What ions are primarily involved in causing depolarization during an action potential?

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

At what membrane potential do Na+ channels begin to open?

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

What is the role of K+ channels in action potential propagation?

<p>K+ channels help restore the resting membrane potential by allowing K+ to exit the cell.</p> Signup and view all the answers

Why is the concept of 'all-or-nothing' important in action potentials?

<p>It signifies that an action potential occurs fully if the threshold is reached, or not at all if it is not.</p> Signup and view all the answers

How does the brain differentiate between stimuli, given that action potentials are uniform?

<p>The brain identifies stimuli based on the specific nerve pathways and regions in which the action potentials terminate.</p> Signup and view all the answers

What is the significance of graded potentials in sensory cells?

<p>Graded potentials result from stimulation of sensory cells and lead to the graded release of neurotransmitters.</p> Signup and view all the answers

What occurs if the threshold of -55 mV is not reached in a nerve cell?

<p>If the threshold of -55 mV is not reached, no action potential is generated in the nerve cell.</p> Signup and view all the answers

Explain the role of neurotransmitters at synapses.

<p>Neurotransmitters are released from pre-synaptic cells and diffuse to bind with post-synaptic receptors, generating graded potentials.</p> Signup and view all the answers

Describe the effect of maintained threshold levels on action potentials.

<p>Maintaining the threshold of -55 mV results in a high frequency of action potentials being generated and propagated.</p> Signup and view all the answers

What initiates the rapid influx of Na+ ions in sensory cells?

<p>Activation of ligand-gated Na+ channels on sensory cells facilitates the rapid influx of Na+ ions.</p> Signup and view all the answers

Why do action potentials propagate in only one direction?

<p>Action potentials propagate in one direction due to the refractory period that follows their generation, preventing backward flow.</p> Signup and view all the answers

What is the role of neuroglia in the propagation of action potentials?

<p>Neuroglia support and modulate the functions of neurons, playing a critical role in maintaining the environment for action potential propagation.</p> Signup and view all the answers

What happens at the axon hillock when neurotransmitter receptors are activated?

<p>Activation of neurotransmitter receptors at the axon hillock generates graded potentials, influencing the likelihood of an action potential.</p> Signup and view all the answers

How does the release of neurotransmitters affect neighboring nerve cells?

<p>The release of neurotransmitters binds to receptors on neighboring nerve cells, which can generate graded potentials in those cells.</p> Signup and view all the answers

Study Notes

Introductory Physiology Lectures

  • The body is organised into multiple systems:
    • Nervous System
    • Muscle System
    • Nine additional systems (not specified within the text)
  • The course focuses on understanding how these systems function together and what they do
  • The course builds on the fundamentals presented in previous lectures, like cell structure, transport processes, and electrical potentials
  • The nervous system is involved in communication, movement, sensory perception, and cognition

Nerve Impulse Generation

  • The nervous system relies on action potentials (APs) for communication between cells
  • Sensory cells are activated via ion channels
  • APs are generated by a rapid influx of sodium ions (Na+) followed by an efflux of potassium ions (K+)
  • The influx of Na+ causes depolarization, bringing the membrane potential closer to the threshold of -55 mV.
  • This shift in potential triggers the opening of voltage-gated Na+ channels, leading to a rapid increase in Na+ influx.
  • Positive feedback occurs as Na+ channels continue opening, resulting in a rapid increase in membrane potential to +30 mV
  • Once the membrane potential reaches +30 mV, Na+ channels close, preventing further depolarization
  • The closing of Na+ channels is followed by the opening of voltage-gated K+ channels, allowing K+ to efflux
  • K+ moves from the cell to the extracellular space as the membrane potential drops to -90 mV.
  • This repolarization phase helps reset the membrane potential, restoring it to the resting membrane potential of -70 mV

Action Potential Propagation

  • APs travel along nerve axons for transmission
  • The rapid change in membrane potential allows for fast and efficient communication
  • APs are propagated in one direction because the area of the axon that has just experienced an AP is in a refractory period
  • This refractory period is caused by the inactivation of Na+ channels in the recently depolarized region, preventing the generation of another AP in the same area
  • This ensures that the AP propagates away from its point of origin
  • Myelin sheaths, which are formed by specialized neuroglia (glial cells), wrap around the axon and insulate it
  • Myelination increases the speed of AP propagation by reducing the resistance of the membrane to ion flow
  • Myelinated axons are thus much faster than unmyelinated axons

Synaptic Transmission

  • The communication between neurons occurs at synapses
  • Sensory cells are activated, leading to the release of neurotransmitters (NTs)
  • NTs are chemicals that transmit signals from the presynaptic neuron to the postsynaptic neuron
  • The release of NTs is triggered by the arrival of the AP at the synapse and the influx of calcium ions (Ca2+) into the presynaptic terminal
  • NTs diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic neuron
  • This binding triggers a series of events, including changes in membrane permeability and the generation of graded potentials within the postsynaptic neuron
  • The graded potentials can integrate with other signals to determine whether the neuron will fire

Neuronal Circuits

  • Neurons are interconnected in complex circuits, allowing for information processing in the brain and nervous system
  • These circuits are responsible for a wide range of functions, from simple reflexes to complex cognitive processes
  • The brain's ability to perceive and interpret information relies on the integration of signals from various sensory cells and their connections within these neuronal circuits

Local Anesthetics and Neurotoxins

  • Some substances interfere with synaptic transmission
  • Local anesthetics block voltage-gated Na+ channels, disrupting the transmission of APs from sensory neurons
  • This explains their ability to numb specific areas of the body, like when used for dental work or other procedures
  • Neurotoxins also disrupt synaptic transmission, but their mechanisms are different from local anesthetics
  • They may interfere with the release or binding of NTs, which can have serious consequences, including muscle paralysis or even death

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Introductory Physiology Lectures – S1A PDF

Description

This quiz covers the fundamentals of physiology, focusing on the organization and function of various body systems, especially the nervous system. It explores how communication is facilitated through nerve impulses and the role of action potentials. Ideal for students looking to understand the basics of human physiology and the intricate workings of nervous functions.

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