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