Anatomy Chapter 8

What are the functions of the nervous system?

- Monitors the body's internal and external environments - Integrates sensory information - Coordinates voluntary and involuntary responses

The resting potential of a neuron is

-70 mV

The neurilemma of axons in the peripheral nervous system is the outer layer of

Schwann Cells

The branching structures that, together with the cell body, are sensitive to chemical, mechanical, or electrical stimulation are called

dendrites

Most neurons in the brain are

multipolar

Adrenergic neurons release the neurotransmitter

norepinephrine

Adrenergic synapses release the neurotransmitter

norepinephrine.

The myelin sheaths that surround the axons of some of the neurons in the CNS are formed by

oligodendrocytes

All of the nervous tissue outside of the central nervous system comprises the

peripheral nervous system

The ________ is the layer of the meninges that is in direct contact with the surface of the brain.

pia mater

When a neuron is at rest, which ion passes through its membrane most easily?

potassium

Head injuries that damage cerebral blood vessels are serious conditions because

these spaces compress and distort the relatively soft tissues of the brain

Which spinal cord structure(s) contains the axons of CNS motor neurons that control muscles and glands?

ventral roots

Most neurons lack centrioles. This observation explains

why such neurons cannot divide through mitosis

Which ion is needed to trigger the release of acetylcholine, via exocytosis, into the synaptic cleft?

calcium

The gray matter of the spinal cord is dominated by

cell bodies of neurons and glial cells

The brain and spinal cord comprise the

central nervous system

Opening of voltage-gated sodium channels in the membrane of a neuron results in

depolarization

In adults, the spinal cord usually extends to which level?

first or second lumbar vertebra

Changes in the membrane potential that cannot spread far from the site of stimulation are called

graded potentials

The projections of gray matter extending through the white matter toward the outer surface of the spinal cord are called

horns

A stimulus that opens gated potassium ion channels, taking the membrane potential away from 0 mV, results in which of the following?

hyperpolarization

Enlargements of the spinal cord occur

in the cervical and lumbar regions

What is the function of the efferent division of the nervous system?

sending signals to muscles

Identify the correct sequence of steps in the generation of an action potential. 1. Activation of sodium channels and rapid depolarization 2. Inactivation of sodium channels and activation of potassium channels 3. Depolarization to threshold 4. Closing of potassium channels

3, 1, 2, 4

The entire spinal cord is divided into ________ segments.

31

Which of the following is the correct order of events that occur at a cholinergic synapse? 1. Extracellular calcium enters the axon terminal, triggering the exocytosis of acetylcholine. 2. Acetylcholine is removed by acetylcholinesterase. 3. Acetylcholine binds to receptors and depolarizes the postsynaptic membrane. 4. Axon terminal depolarizes.

4, 1, 3, 2

The largest and most numerous of the glial cells in the central nervous system are the

astrocytes

Neurons that have one axon and one dendrite with the soma between them are called

Bipolar

Branches that sometimes occur along the length of an axon are called

Collaterals

Which neuroglial cells produce CSF in some regions of the brain?

Ependymal Cells

What nervous system provides involuntary regulation of smooth muscle, cardiac muscle, and glandular activity?

autonomic

Neurons that have two or more dendrites and a single axon extending away from the soma are called

Multipolar

Clusters of rough endoplasmic reticulum and free ribosomes are known as

Nissl bodies

Bundles of CNS axons that share a common origin, destination, and function are called

Tracts

Which of the following neurotransmitters usually depolarizes postsynaptic neurons?

acetylcholine

What division of the nervous system brings sensory information to the central nervous system?

afferent

The part of the peripheral nervous system that brings information to the central nervous system is the

afferent divison

The all-or-none principle states that

all stimuli great enough to bring the membrane to threshold will produce identical action potentials

Interneurons

are found only in the central nervous system

The glial cells responsible for maintaining the blood-brain barrier are the

astrocytes

If the dorsal root of a spinal nerve is severed,

incoming sensory information would be disrupted

In general, the nervous system

is fast acting

Saltatory conduction

is faster than conduction on an unmyelinated axon

During continuous conduction,

local currents depolarize adjacent areas of membrane so that action potentials continue to form along the membrane.

Small phagocytic glial cells, which are derived from white blood cells, are called

microglia

The posterior horns of the spinal cord contain

sensory nuclei

The specialized membranes that protect the spinal cord are termed

spinal meninges

Which of the following contains a delicate network of collagen and elastin fibers through which cerebrospinal fluid circulates?

subarachnoid space