Exam #3

Differentiate between sensory nuclei and motor nuclei.

Sensory nuclei receive and relay sensory information from peripheral receptors. Motor nuclei issue motor commands to peripheral effectors.

A disease that damages myelin sheaths would affect which part of the spinal cord?

A disease that damages myelin sheaths would affect the columns in the white matter of the spinal cord, because the columns are composed of bundles of myelinated axons.

Which of the following axons is myelinated: one that propagates action potentials at 50 meters per second, or one that carries them at 1 meter per second?

Action potentials travel along myelinated axons (by saltatory propagation) at much higher speeds than along unmyelinated axons. The axon with a propagation speed of 50 meters per second must be the myelinated axon. Typical propagation speeds for unmyelinated axons are about 1 m/sec.

Define action potential.

An action potential is a propagated change in the membrane potential of excitable cells, initiated by a change in the membrane permeability to sodium ions.

One pathway in the central nervous system consists of 3 neurons, another of 5 neurons. If the neurons in the two pathways are identical, what process will determine which pathway will transmit impulses more rapidly?

Because of synaptic delay, the pathway with fewer neurons (in this case, 3) will transmit impulses more rapidly.

List the neuroglia of the central nervous system.

Central nervous system neuroglia include astrocytes, ependymal cells, oligodendrocytes, and microglia.

What would be the effect of damage to the afferent division of the PNS?

Damage to the afferent division of the PNS, which is composed of nerves that carry sensory information to the brain and spinal cord, would interfere with a person's ability to experience a variety of sensory stimuli.

Damage to which root of a spinal nerve would interfere with motor function?

Damage to the anterior root of a spinal nerve, which contains both visceral and somatic motor fibers, would interfere with motor function.

What effect would a chemical that blocks the voltagegated sodium ion channels in the plasma membrane of a neuron have on its ability to depolarize?

If the voltage-gated sodium ion channels in the plasma membrane of a neuron could not open, sodium ions could not flood into the neuron and it would not be able to depolarize.

If a synapse involves direct physical contact between cells, it is termed ____ ; if the synapse involves a neurotransmitter, it is termed ____ .

If a synapse involves direct physical contact between cells, it is termed ____ ; if the synapse involves a neurotransmitter, it is termed ____ .

How would decreased diffusion across the arachnoid granulations affect the volume of cerebrospinal fluid in the ventricles?

If diffusion across the arachnoid granulations decreased, less CSF would reenter the bloodstream, and CSF would accumulate in the ventricles. The increased pressure within the ventricles due to accumulated CSF could damage the brain.

What effect would decreasing the concentration of extracellular potassium ions have on the membrane potential of a neuron?

If the extracellular concentration of potassium ions decreased, more potassium would leave the cell, and the membrane potential would become more negative. This condition is called hyperpolarization.

What would happen if the normal circulation or resorption of CSF were blocked?

If the normal circulation or resorption of cerebrospinal fluid (CSF) became blocked, CSF would continue to be produced at the choroid plexus in each ventricle, but the fluid would remain there, causing the ventricles to swell—a condition known as hydrocephalus.

Many water-soluble molecules that are abundant in the blood occur in small amounts or not at all in the cerebrospinal fluid (CSF) of the brain. Why?

Many watersoluble molecules are rare or absent in the extracellular (ECF), or cerebrospinal fluid (CSF), of the brain because the blood brain barrier regulates the movement of such molecules from the blood to the ECF of the brain.

Identify the neuroglia of the peripheral nervous system.

Peripheral nervous system neuroglia include satellite cells and Schwann cells (neurolemmocytes).

What brain regions make up the brainstem?

The brainstem is made up of the midbrain, pons, and medulla oblongata.

Where is the cerebrospinal fluid that surrounds the spinal cord located?

The cerebrospinal fluid that surrounds the spinal cord is located in the subarachnoid space, which lies between the epithelium of the arachnoid mater and the pia mater.

Name the four major regions of the brain.

The four major regions of the brain are the cerebrum, cerebellum, diencephalon, and brainstem.

Identify the steps involved in the generation and propagation of an action potential.

The four steps involved in the generation of action potentials are (1) depolarization to threshold; (2) activation of voltage-gated sodium ion channels and rapid depolarization; (3) inactivation of voltage-gated sodium ion channels and activation of voltage-gated potassium ion channels; and (4) closing of voltagegated potassium ion channels and return to normal permeability.

Describe the general structure of a synapse.

The general structural components of a synapse, the site where a neuron communicates with another cell, are a presynaptic cell and a postsynaptic cell, whose plasma membranes are separated by a narrow synaptic cleft.

From superficial to deep, name the layers that make up the cranial meninges.

The layers of the cranial meninges are the outer dura mater, the middle arachnoid mater, and the inner pia mater.

A man with polio has lost the use of his leg muscles. In which area of his spinal cord would you expect the virusinfected motor neurons to be?

The polio virus-infected neurons would be in the anterior horns of the spinal cord, where the cell bodies of somatic motor neurons are located.

What is the relationship between myelin and the propagation speed of action potentials?

The presence of myelin greatly increases the propagation speed of action potentials.

Define resting membrane potential.

The resting membrane potential is the membrane potential of a normal, unstimulated cell.

Which primary brain vesicle is destined to form the cerebellum, pons, and medulla oblongata?

The rhombencephalon or hindbrain develops into the cerebellum, pons, and medulla oblongata.

Which type of neuroglia would increase in number in the brain tissue of a person with a CNS infection?

The small phagocytic cells called microglia occur in increased numbers in infected (and damaged) areas of the CNS

Identify the three spinal meninges.

The three spinal meninges are the dura mater, arachnoid mater, and pia mater.

Describe the two functional divisions of the peripheral nervous system, and cite their primary functions.

The two functional divisions of the peripheral nervous system are the afferent division, which brings sensory information to the CNS from receptors in peripheral tissues and organs, and the efferent division, which carries motor commands from the CNS to muscles, glands, and adipose tissue.

Identify the two components of the efferent division of the PNS and their effectors.

he two components of the efferent division of the PNS and their effectors are the somatic nervous system (SNS) and the autonomic nervous system (ANS). The SNS effectors are skeletal muscles and the ANS effectors include smooth and cardiac muscle, glands, and adipose tissue.

Describe the three anatomical divisions of the nervous system.

the three anatomical divisions of the nervous system are the central nervous system (CNS), consisting of the brain and spinal cord, the peripheral nervous system (PNS), consisting of all nervous tissue outside the CNS and ENS, and the enteric nervous system (ENS), consisting of the network of neurons and nerve networks in the walls of the digestive tract.