Podcast
Questions and Answers
What is the primary function of the myelin sheath that surrounds the axon of some neurons?
What is the primary function of the myelin sheath that surrounds the axon of some neurons?
- To facilitate the exchange of ions necessary for maintaining resting potential.
- To provide structural support to the axon and prevent physical damage.
- To insulate the axon and increase the speed of impulse transmission. (correct)
- To synthesize neurotransmitters required for impulse transmission.
During the repolarization phase of an action potential, which of the following events occurs?
During the repolarization phase of an action potential, which of the following events occurs?
- Chloride ions (Cl-) rush into the cell, further increasing the positive charge.
- Sodium ions (Na+) rush into the cell, making the inside more positive.
- Potassium ions (K+) rush out of the cell, making the inside more negative. (correct)
- Calcium ions (Ca2+) are actively transported out of the cell to restore balance.
How does the 'all-or-nothing' principle relate to the generation of an action potential in a neuron?
How does the 'all-or-nothing' principle relate to the generation of an action potential in a neuron?
- The neuron generates multiple action potentials with varying amplitudes based on the strength of the stimulus.
- The neuron always generates an action potential, regardless of the stimulus received.
- An action potential is only generated if the stimulus exceeds a certain threshold; otherwise, no impulse is sent. (correct)
- The strength of the action potential is directly proportional to the strength of the stimulus.
Which of the following best describes the role of the sodium-potassium pump in maintaining the resting potential of a neuron?
Which of the following best describes the role of the sodium-potassium pump in maintaining the resting potential of a neuron?
What is the immediate consequence if the Nodes of Ranvier were evenly distributed, but much further apart from each other than normal?
What is the immediate consequence if the Nodes of Ranvier were evenly distributed, but much further apart from each other than normal?
How does the refractory period contribute to the function of neurons?
How does the refractory period contribute to the function of neurons?
Which of the following correctly pairs a division of the nervous system with its primary function?
Which of the following correctly pairs a division of the nervous system with its primary function?
An injury damages the motor neurons connected to a specific muscle. Which of the following is a likely consequence?
An injury damages the motor neurons connected to a specific muscle. Which of the following is a likely consequence?
How would a significant decrease in the diameter of a neuron's axon affect the transmission of nerve impulses?
How would a significant decrease in the diameter of a neuron's axon affect the transmission of nerve impulses?
A neurotoxin blocks the function of the sodium-potassium pump in a neuron. What would be the most likely immediate effect on the neuron?
A neurotoxin blocks the function of the sodium-potassium pump in a neuron. What would be the most likely immediate effect on the neuron?
Flashcards
Central Nervous System (CNS)
Central Nervous System (CNS)
The brain and spinal cord, the control center of the nervous system.
Peripheral Nervous System (PNS)
Peripheral Nervous System (PNS)
Pairs of nerves that branch out from the CNS, connecting it to the rest of the body.
Sensory Neurons
Sensory Neurons
Neurons that carry signals from sensory receptors to the CNS.
Motor Neurons
Motor Neurons
Neurons that carry signals from the CNS to effectors (muscles or glands).
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Myelin Sheath
Myelin Sheath
Insulating layer around the axon of a neuron, made of Schwann cells, that speeds up impulse transmission.
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Nodes of Ranvier
Nodes of Ranvier
Gaps in the myelin sheath where action potentials occur, allowing for faster impulse transmission.
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Resting Potential
Resting Potential
The electrical potential of a neuron at rest, typically around -65mV.
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Depolarization
Depolarization
The change in a neuron's membrane potential, making the inside more positive due to Na+ influx.
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Repolarization
Repolarization
The rapid return of a neuron's membrane potential to negative after depolarization, due to K+ efflux.
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All-or-Nothing Principle
All-or-Nothing Principle
The principle that if the threshold potential is reached, a full action potential occurs; otherwise, nothing happens.
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- The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
- The CNS consists of the brain and spinal cord.
- The PNS comprises pairs of nerves that originate from the CNS.
- Sensory neurons carry impulses to the CNS.
- Motor neurons carry impulses away from the CNS to effectors.
- The voluntary nervous system allows for conscious control, such as moving muscles.
- The autonomic nervous system controls involuntary actions like heartbeat and digestion.
Neuron Structure
- The cell body contains the nucleus and rough endoplasmic reticulum which make proteins/neurotransmitters.
- Dendrons/dendrites carry impulses toward the cell body.
- The axon is a long fiber that carries impulses away from the cell body.
- The myelin sheath provides insulation for faster impulses via Schwann cells.
- Nodes of Ranvier are gaps in the myelin sheath where action potentials occur.
Action Potential
- Resting potential is -65mV and is maintained by the sodium-potassium pump.
- Depolarization occurs when sodium channels open, allowing Na+ to enter, making the inside positive.
- Action potential reaches +40mV, triggering the nerve impulse.
- Repolarization occurs when potassium channels open, allowing K+ to leave, restoring the negative inside.
- Hyperpolarization can occur if too much K+ exits the cell.
- The sodium-potassium pump restores the resting potential.
All-or-Nothing Principle
- If the threshold potential is not met, no impulse is sent.
- When the threshold is exceeded, a full action potential always occurs.
Action Potential Passage
- In unmyelinated axons, the impulse moves step by step, which is slow.
- In myelinated axons, saltatory conduction occurs where the impulse jumps from node to node, greatly increasing the speed.
Factors Affecting Nerve Impulse Speed
- The presence of a myelin sheath increases speed.
- A wider axon diameter results in faster impulse transmission.
- Higher temperatures increase speed, but excessive heat can denature proteins.
Refractory Period
- Ensures the one-way flow of nerve impulses.
- Prevents overlapping action potentials.
- Limits the frequency of nerve impulses.
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