12.13.2 Human Regulation: Nervous System: Nerve Function and Reflexes

Question 1

Human Regulation: Nervous System: Nerve Function and Reflexes

Answer 1

• A neuron’s structure reflects its function. The three major classes of neurons are sensory neurons, interneurons, and motor neurons. Neurons are classed according to function, but neuronal structure also varies greatly within each class.
• Sensory neurons receive signals from the environment and transmit them to the central nervous system. A sensory neuron’s structure relates to its function, which could be to sense light, pressure, or the presence of chemicals.
• Interneurons link sensory and motor neurons. They synapse only with other neurons and typically have multiple dendrites. The structure of an interneuron allows it to send impulses to different locations.
• Motor neurons convey messages from the central nervous system to effectors, the muscle or gland cells that carry out the response.
• A reflex is any quick, automatic response to a stimulus. An example of a reflex is the knee-jerk reflex. The knee-jerk reflex occurs as part of a neural circuit consisting of sensory receptors, motor neurons, and interneurons.

Question 2

sensory and motor neuron

Answer 2

• The knee-jerk reflex, shown in the diagram to the left, occurs when the leg jerks in response to a tap on the leg just below the knee.
• Sensory receptors detect the pressure from the tap. A signal travels along a sensory neuronto the spinal cord. The signal then travels to a motor neuron, which triggers the quadriceps to contract and the leg to kick.
• At the same time, the sensory signal also travels through an interneuronto another motor neuron that inhibits contraction of the flexors. Contraction of the flexors opposes the contraction of the quadriceps; thus, if the flexors were to contract, there would be no knee-jerk response.

Question 3

Which of the following is not true about a reflex?

Answer 3

• It cannot involve interneurons.

Question 4

Which of the following is not a type of neuron?

Answer 4

• synapse neuron

Question 5

The synaptic terminal of a sensory neuron is located in the __________, while the synaptic terminal of a motor neuron is located in the __________.

Answer 5

• CNS, muscle cell

Question 6

Interneurons

Answer 6

• integrate sensory and motor input.

Question 7

Interneurons

Answer 7

• generally interact with more than two other neurons.

- do not generally have the long axons associated with motor and sensory neurons.

Question 8

The basic function of nerve cells is

Answer 8

• the conduction of electrical impulses.