01._nervous_system_24

What is the nervous system primarily responsible for?

The fast communication system in the body.

What is a reflex arc?

A neural pathway that controls a reflex action.

Which type of neuron carries sensory information to the CNS?

Sensory neurone.

What is the role of the Central Nervous System (CNS)?

Receives sensory information and relays it to motor neurons.

What is an effector?

An organ or structure that responds to a stimulus, such as a muscle.

How do receptors function in a reflex arc?

They detect a stimulus and convert it into a nerve impulse.

What is the resting potential of a neuron approximately measured at?

-70mV.

What is the role of Schwann cells?

To wrap around axons and form myelin sheaths, insulating and increasing conduction speed.

What happens during depolarization of an axon?

Sodium ions flood into the neuron, making the inside positive compared to the outside.

What triggers the opening of sodium ion channels in a neuron?

A stimulus that exceeds the threshold potential.

What is the difference between absolute and relative refractory periods?

Absolute: Na+ channels are inactive; Relative: Na+/K+ balance restores but a strong stimulus can trigger action.

What is hyperpolarization?

When the inside of a neuron becomes more negative than the resting potential.

What process continues to maintain the resting potential?

The sodium-potassium pump, which pumps 3 Na+ ions out and 2 K+ ions in.

What happens to potassium ions during repolarization?

They diffuse out of the neuron, restoring a negative charge inside.

What occurs when a nerve impulse travels down a myelinated neuron?

The impulse jumps between Nodes of Ranvier in a process called saltatory conduction.

What do sensory receptors do?

They transduce energy from one form into electrical energy (nerve impulses).

What is action potential?

A rapid change in membrane potential that travels along the axon.

What opportunities does the refractory period offer?

Ensures unidirectional movement of action potentials along the axon.

What type of receptors detect temperature changes?

Thermoreceptors.

What is the general role of motor neurons?

To carry nerve impulses from the CNS to effectors.

Define depolarization in the context of a nerve impulse.

The process where the membrane potential becomes less negative and approaches +40mV.

What role do neurotransmitters play in synaptic transmission?

They transmit signals between neurons by binding to receptor sites.

During the generation of an action potential, what happens first?

Voltage-gated sodium channels open, allowing Na+ ions to enter.

What role does ATP play in maintaining the resting potential?

It provides energy for the sodium-potassium pump to function.

What is the role of intermediate neurons?

To connect sensory neurons to motor neurons within the CNS.

Identify a characteristic of sensory neurons.

They often have long dendrites which extend from receptors.

What are baroreceptors sensitive to?

Pressure changes.

How is the action potential generated and propagated?

By the opening and closing of voltage-gated sodium and potassium channels.

What mechanisms increase the conduction speed of a neuron?

Myelination by Schwann cells and the presence of Nodes of Ranvier.

Explain the main steps in generating an action potential.

Stimulus opens Na+ channels, Na+ floods in, depolarization occurs, K+ channels then open to repolarize.

What happens if the threshold potential is not reached?

No action potential is generated; this is known as the 'all-or-nothing' principle.

Describe the sodium-potassium pump's function.

It actively transports sodium out of the cell and potassium into the cell to maintain electrical gradients.

What type of channels open during the depolarization phase?

Voltage-gated sodium channels.

During which phase do potassium channels open?

During repolarization.

What is the significance of the -55mV threshold?

It is the critical value at which an action potential is triggered.

What is the 'all or nothing' response?

An action potential is generated fully or not at all, regardless of the stimulus strength.

What happens after an action potential is generated?

The sodium channels close and potassium channels open to repolarize the membrane.

Explain the role of glial cells in the nervous system.

They support and protect neurons, facilitating communication.

What occurs during the repolarization stage of an action potential?

K+ ions exit the neuron, restoring the negative charge inside the cell.