Podcast
Questions and Answers
If the membrane potential of a neuron becomes more negative than its resting potential, it is said to be:
If the membrane potential of a neuron becomes more negative than its resting potential, it is said to be:
What is the typical resting membrane potential of a neuron?
What is the typical resting membrane potential of a neuron?
What is the process called when the membrane potential returns to its resting state after being depolarized?
What is the process called when the membrane potential returns to its resting state after being depolarized?
What causes the membrane potential to become more positive during depolarization?
What causes the membrane potential to become more positive during depolarization?
Signup and view all the answers
Which of the following is NOT a change in membrane potential?
Which of the following is NOT a change in membrane potential?
Signup and view all the answers
Which of the following statements accurately describes the role of the Nodes of Ranvier in myelinated neurons?
Which of the following statements accurately describes the role of the Nodes of Ranvier in myelinated neurons?
Signup and view all the answers
Which of the following is NOT a characteristic of the refractory period in neuronal action potential generation?
Which of the following is NOT a characteristic of the refractory period in neuronal action potential generation?
Signup and view all the answers
What is the primary function of the myelin sheath in nerve fibers?
What is the primary function of the myelin sheath in nerve fibers?
Signup and view all the answers
What is the most likely effect of a drug that blocks the opening of voltage-gated Na+ channels in a neuron?
What is the most likely effect of a drug that blocks the opening of voltage-gated Na+ channels in a neuron?
Signup and view all the answers
During the repolarization phase of an action potential, what is the primary movement of ions across the neuronal membrane?
During the repolarization phase of an action potential, what is the primary movement of ions across the neuronal membrane?
Signup and view all the answers
Which of the following statements accurately describes the relationship between stimulus strength and the size of a graded potential?
Which of the following statements accurately describes the relationship between stimulus strength and the size of a graded potential?
Signup and view all the answers
What is the main difference between an action potential and a graded potential?
What is the main difference between an action potential and a graded potential?
Signup and view all the answers
What is the term for the change in membrane potential of the postsynaptic membrane?
What is the term for the change in membrane potential of the postsynaptic membrane?
Signup and view all the answers
Which type of neurotransmitter is responsible for generating an excitatory postsynaptic potential (EPSP)?
Which type of neurotransmitter is responsible for generating an excitatory postsynaptic potential (EPSP)?
Signup and view all the answers
Which of the following correctly describes the role of voltage-gated Na+ channels in the generation of an action potential?
Which of the following correctly describes the role of voltage-gated Na+ channels in the generation of an action potential?
Signup and view all the answers
What is the threshold potential for the generation of an action potential?
What is the threshold potential for the generation of an action potential?
Signup and view all the answers
Which of the following statements accurately describes the role of leakage channels in the maintenance of the resting membrane potential?
Which of the following statements accurately describes the role of leakage channels in the maintenance of the resting membrane potential?
Signup and view all the answers
Which type of postsynaptic potential is associated with an inhibitory neurotransmitter?
Which type of postsynaptic potential is associated with an inhibitory neurotransmitter?
Signup and view all the answers
Which of the following statements best describes the process of summation in relation to graded potentials?
Which of the following statements best describes the process of summation in relation to graded potentials?
Signup and view all the answers
What is the primary function of the sodium-potassium pump in the context of membrane potential?
What is the primary function of the sodium-potassium pump in the context of membrane potential?
Signup and view all the answers
Study Notes
Unit 2: Part 2 - Action Potential Propagation
- Unit covers action potential propagation (pages 179-193)
Describing Changes in Membrane Potential
- Normal resting potential is approximately -70mV
- Depolarization: Voltage increases relative to resting potential
- Hyperpolarization: Voltage decreases relative to resting potential
- Repolarization: Restoration of resting membrane potential
What Causes Changes in Membrane Potential?
- Stimulus: Any change in the cell's environment
- Ion channels open/close, causing ions to move in/out of the cell
- Resultant change is either a graded potential or an action potential
2 Types of Potentials
- Action potential
- Graded potential
Graded Potentials
- Stimuli cause voltage-gated ion channels to open.
- If the change in charge isn't enough to reach +30mV (action potential threshold), it's a graded potential
- Graded potentials are small changes in membrane potential (voltage across the membrane).
- Stronger stimuli produce larger changes in voltage
- Graded potentials dissipate as they move away from the stimulus area.
Graded Potentials aka Postsynaptic Potentials (PSP)
- Changes in membrane potential of postsynaptic membrane
- Can be either inhibitory (IPSP) or excitatory (EPSP)
Excitatory and Inhibitory Neurotransmitters
- Excitatory neurotransmitters increase the likelihood of an action potential (AP) occurring on the postsynaptic neuron, leading to an excitatory postsynaptic potential (EPSP)
- Acetylcholine is a primary example
- Works by opening Na+ ion channels
- Inhibitory neurotransmitters decrease the likelihood of an action potential occurring, leading to an inhibitory postsynaptic potential (IPSP)
- GABA is a primary example in the brain
- Works by opening Cl- ion channels
Threshold & the Development of an Action Potential
- For an AP to occur, the membrane potential must depolarize to -55mV (threshold)
- If a stimulus is strong enough to bring membrane potential from -70mV to -55mV, an action potential will occur
- Once the threshold (-55mV) is reached, more Na+ gates open, and more Na+ enters the cell until +30mV is reached.
Action Potential
- Action Potential is depicted as a graph. The graph shows the membrane potential fluctuating between -70mV (resting) and +30mV (depolarized ) over time
- Phases of the action potential:
- Phase 1 to 2
- Phase 2 to 3
- Resting potential
Action Potential
- Specialized channels (voltage-gated Na+ and K+ channels) exist on the cell membrane, opening/closing based on membrane potential changes.
Action Potential Sequence of Events
- Stimulus (e.g., temperature, pressure, light, sound) alters resting membrane potential, causing chemically gated Na+ channels to open.
- Strong graded potential reaches threshold (-55mV), triggering voltage-gated Na+ channels to open, allowing Na+ to rush into the cell
- Membrane potential quickly climbs from -70mV to +30mV (action potential generated)
- Na+ channels close, and K+ channels open
- Repolarization occurs as K+ exits the cell.
- K+ channels close slowly, leading to hyperpolarization for a short duration.
Action Potential-All or None Principle
- An action potential either occurs completely or doesn't occur at all. A certain threshold must be reached for an action potential.
Refractory Periods
- Absolute refractory period: No stimulus, regardless of strength, can generate a second action potential during this period
- Relative refractory period: A stronger-than-normal stimulus is necessary to generate a second action potential early in this period. A weaker-than-normal stimulus can trigger one later.
Linking the AP to a Nerve Cell
- Neurons detect stimuli and communicate with other cells.
- Functional cell in the nervous system: neuron
- Stimulus → receptor → integrating center→ effector → response
Details of the Neuron
- Part | Job
- Dendrites | Detect stimuli
- Axon | Develops and sends action potentials
- Cell Body | Nucleus (biosynthetic center)
Action Potential Propagation
- Continuous propagation: Action potential spreads along every section of the membrane and repeats
- Saltatory conduction: Action potentials “jump” from Node of Ranvier to Node of Ranvier
Myelinated Fibers vs. Non-Myelinated Fibers
- Myelinated fibers conduct impulses faster than non-myelinated fibers because the myelin sheath prevents signal decay. Action potentials “jump” between Nodes of Ranvier.
- Non-myelinated axons have voltage-gated channels along the entire length. As a result, the action potential has to travel down the entire membrane segment by segment.
Signal Decay
- In a bare plasma membrane (without voltage-gated channels), voltage decays as current leaks across the membrane
Speed of Nerve Conduction
- Table 7.4 provides conduction velocities based on different nerve fiber types (e.g., A alpha, A beta, A gamma, C), including the fiber diameter and myelination status.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz focuses on the concepts related to action potential propagation, including changes in membrane potential such as depolarization and hyperpolarization. It covers the mechanisms that cause these changes, including ion channel behavior and the types of potentials that result. The quiz will assess your understanding of these fundamental neurophysiological processes.
