lect 12 pt 3

What are sensory neurons also called functionally?

Afferent neurons, which carry sensory information toward the CNS.

What is the usual structural classification of sensory neurons?

They are usually unipolar or bipolar.

What are motor neurons also called functionally?

Efferent neurons, which carry signals away from the CNS toward peripheral structures.

What is the usual structural classification of motor neurons?

Multipolar neurons.

Where do interneurons begin and end?

Interneurons begin and end within the CNS and are not part of the PNS.

What is the usual structural classification of interneurons?

Multipolar neurons.

How does a sensory neuron participate in a reflex pathway?

A sensory receptor, such as a pinched skin receptor, generates a nerve impulse that travels along a sensory neuron into the spinal cord.

What happens to the sensory signal when it reaches the spinal cord in the illustrated reflex?

The sensory neuron synapses with an interneuron in the spinal cord.

What happens after the interneuron receives the sensory signal?

The interneuron synapses with a motor neuron, which carries a motor signal back toward a peripheral structure.

What type of response does the illustrated sensory–interneuron–motor pathway represent?

A reflex, in which sensory information enters the spinal cord and a motor response is sent out.

How can information from a reflex pathway also reach the brain?

The interneuron may cross over and synapse with an ascending neuron that carries information toward the brain.

How can the brain influence the motor response in the illustrated pathway?

The brain processes the information and sends a signal down another neuron, which may cross back over and pass the impulse to the motor neuron.

Which neuron types are involved in the illustrated pathway?

Sensory neurons, interneurons, and motor neurons.

What structural types can sensory neurons have?

Sensory neurons are usually unipolar, but they can also be bipolar in certain locations, including the nose.

What are the main parts of a typical neuron discussed in the lecture?

Dendrites, the cell body (soma), the axon, and the axon terminals.

What is the receiving end of a neuron?

The dendrites, which receive incoming signals from other cells.

What is the soma?

The soma is another name for the neuron's cell body.

Why did the instructor mention the terms soma and cell body?

Both terms are commonly used, and the instructor noted that some nervous system terminology has French-derived synonyms because much research was conducted in France.

What is the axon?

The axon carries the nerve impulse away from the cell body toward the axon terminals.

What are axon terminals also called?

Terminal boutons.

What is the synaptic gap?

The small space between communicating cells across which neurotransmitters diffuse.

What are the vesicles in the axon terminals?

Vesicles are small structures containing neurotransmitters that are stored in the axon terminals until needed for release.

Where are neurotransmitter-filled vesicles manufactured, according to the lecture?

They are manufactured in the cell body and transported down the axon toward the terminals.

How are vesicles transported to the axon terminals?

They travel along cytoskeletal proteins that act like railroad tracks, carrying the vesicles down the axon.

What can stimulate a neuron to fire?

A neuron can be stimulated by neurotransmitters released from another neuron or by mechanical stimuli, such as those detected by a mechanical receptor in the skin.

How do neurotransmitters initiate a signal in the receiving neuron?

Neurotransmitters bind to receptors on the dendrites, and enough receptor binding can bring the neuron to its threshold.

What happens when the neuron reaches its threshold?

The axon depolarizes, generating an electrical signal that travels toward the axon terminals.

What happens when the electrical signal reaches the axon terminals?

It prompts the terminals to release neurotransmitters into the synaptic gap.

How does the signal pass from one neuron to the next?

Neurotransmitters diffuse across the synaptic gap and bind to receptors on the next neuron's dendrites, potentially triggering another electrical signal if threshold is reached.

What is the overall pattern of nerve impulse transmission between neurons?

The signal alternates between electrical and chemical forms: electrical along the neuron, chemical across the synaptic gap, and electrical again in the next neuron.