Peripheral Nervous System & Action Potential

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Questions and Answers

What is the primary role of the sensory (afferent) division of the peripheral nervous system?

To perceive sensations from the environment.

To send signals from the brain to the muscles.

To transmit action potentials from sensory receptors to the central nervous system. (correct)

To regulate the dilation of blood vessels.

What is meant by 'efferent' in the context of the motor division of the peripheral nervous system?

Regulating the internal functions of the body.

Sending signals towards the sensory receptors.

Transmitting sensory information to the brain.

Conducting signals from the central nervous system to effector organs. (correct)

Which of the following actions is primarily controlled by the motor (efferent) division?

Dilating blood vessels.

Sending sensory information to the CNS.

Perceiving temperature changes.

Sweating in response to heat. (correct)

What happens when sensory neurons detect heat from the environment?

They send action potentials to the central nervous system. Signup and view all the answers

Why is it important for blood vessels to dilate when it is hot outside?

To allow blood to pass through more easily and dissipate heat. Signup and view all the answers

Which of the following correctly defines afferent neurons?

Neurons that conduct signals from sensory receptors to the CNS. Signup and view all the answers

What triggers the sweating response in the body when it is hot?

The perception of heat by sensory neurons. Signup and view all the answers

In the context of the nervous system, what does 'action potential' refer to?

The electrical signal that facilitates communication between neurons. Signup and view all the answers

What initiates the depolarization of the cell?

A strong enough stimulus Signup and view all the answers

What happens to the voltage-gated sodium channels during the depolarization phase?

They close to prevent further sodium entry Signup and view all the answers

What is the effect of Sodium ions entering the cell during depolarization?

The inside of the cell becomes more positive Signup and view all the answers

What characterizes the 'all or none law' in terms of action potential?

Threshold must be reached for an action potential to occur Signup and view all the answers

Why might the cell not reach depolarization with insufficient stimulus?

It will have failed initiation Signup and view all the answers

How do potassium-voltage-gated channels behave during the early stages of depolarization?

They open slowly to manage ionic balance Signup and view all the answers

What occurs when the inside of the cell becomes more positive than the outside?

The cell attempts to reach equilibrium Signup and view all the answers

What role does the sodium-potassium pump play during depolarization?

It is unable to keep up with sodium influx Signup and view all the answers

What process allows action potentials to jump from one node to another along myelinated axons?

Saltatory conduction Signup and view all the answers

What is the result of the influx of calcium ions at the presynaptic terminal?

It causes synaptic vesicles to release neurotransmitters. Signup and view all the answers

Why is less energy required for the sodium-potassium pump in myelinated axons compared to unmyelinated axons?

Ion channels are located only at the nodes of Ranvier. Signup and view all the answers

Which of the following best defines the term 'cleft' as used in synaptic transmission?

A space between the presynaptic and postsynaptic neuron Signup and view all the answers

What mechanism do neurotransmitters use to cross the synaptic cleft?

Diffusion Signup and view all the answers

What is the primary function of the sodium-potassium pump in neurons?

To maintain the resting membrane potential Signup and view all the answers

How do neurotransmitters interact with their receptors on the postsynaptic neuron?

They bind to receptor molecules like keys to locks Signup and view all the answers

Which channels are specifically mentioned as being ligand-gated on the postsynaptic neuron?

Sodium, potassium, and chloride channels Signup and view all the answers

What is the primary role of acetylcholine in the nervous system?

To conduct action potentials to motor neurons Signup and view all the answers

What is one mechanism by which norepinephrine is cleared from the synaptic cleft?

Active transport back into the presynaptic terminal Signup and view all the answers

How does enzymatic degradation affect neurotransmitter function?

It leads to rapid breakdown and recycling Signup and view all the answers

What defines a reflex arc in the nervous system?

Its use of a direct pathway for rapid reactions Signup and view all the answers

Why is the mechanism of neurotransmitter transfer described as occurring 'countless times per second'?

Because synaptic transmission involves continuous input Signup and view all the answers

What is the effect of a converging neuronal pathway?

It reinforces sensory input from multiple neurons Signup and view all the answers

What could happen if acetylcholine is not effectively broken down in the synapse?

Prolonged muscle contraction Signup and view all the answers

Which statement accurately describes the reaction duration of synaptic neurotransmitter action?

It is short in duration and rapidly terminated Signup and view all the answers

What initiates a reflex action without input from the brain?

Interneurons synapsing with sensory neurons Signup and view all the answers

Which branch of the sensory neuron carries an action potential to the brain?

The branch that synapses with ascending neurons Signup and view all the answers

What is formed when the dorsal and ventral roots join together?

Spinal nerve Signup and view all the answers

What type of neuron is described as pseudounipolar?

A sensory neuron with a single long axon Signup and view all the answers

What is the main role of the interneurons in the reflex arc?

They relay signals between sensory and motor neurons Signup and view all the answers

How does a reflex action differ from a voluntary movement?

Reflex actions require no conscious thought Signup and view all the answers

What is a likely consequence of damage to spinal nerves?

Paralysis and loss of movement Signup and view all the answers

What type of communication occurs when signals from the cerebral cortex reach motor neurons?

Conscious movement control Signup and view all the answers

Study Notes

Peripheral Nervous System Divisions

The sensory division is also known as the afferent division.
The afferent division carries signals from sensory receptors to the central nervous system.
The motor division is also known as the efferent division.
The efferent division carries signals from the central nervous system to effector organs.
Sensory neurons transmit action potentials from the periphery to the CNS.
Motor neurons transmit action potentials from the CNS to effector organs.

Action Potential

During an action potential, sodium channels open allowing sodium ions to enter the cell.
This makes the inside of the cell more positive than the outside.
When the cell reaches a certain threshold, the sodium channels close and potassium channels open.
Potassium ions leave the cell, making the inside more negative again.
This process is called repolarization.
The all or none law states that a stimulus must reach a certain threshold to trigger an action potential.

Myelinated Axons

The myelin sheath is a fatty substance that covers some axons.
Myelination increases the speed of action potential conduction.
Action potentials jump from one node of Ranvier to the next, a process called saltatory conduction.
Myelinated axons require less energy than unmyelinated axons because the sodium-potassium pump is only active at the nodes of Ranvier.

Synaptic Transmission

Synaptic vesicles contain neurotransmitters which are released into the synaptic cleft.
Neurotransmitters bind to receptor molecules on the postsynaptic neuron.
Acetylcholine is a common neurotransmitter.
Acetylcholinesterase is the enzyme that breaks down acetylcholine.
Norepinephrine is another common neurotransmitter.

Reflexes

A reflex is an involuntary response to a stimulus.
The reflex arc is the neural pathway that mediates a reflex.
Reflexes do not require conscious thought.
Converging neuronal pathways allow multiple neurons to synapse with the same postsynaptic neuron.

Spinal Nerves

Spinal nerves connect the spinal cord to the periphery
Spinal nerves are formed by the fusion of ventral and dorsal roots.
The dorsal root ganglion contains the cell bodies of sensory neurons.
Pseudounipolar neurons have a peripheral branch and an ascending branch.

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Description

Explore the divisions of the peripheral nervous system, including the sensory and motor divisions, and their roles in signal transmission. Learn about action potentials, their phases, and the mechanisms of depolarization and repolarization in neurons.