Chapter 12 Nervous Tissue
Which of the following is true regarding unmyelinated nerve fibers in the PNS?
A Schwann cell folds its plasma membrane around several fibers.
Conduction of a nerve impulse would be the fastest in which of the following?
A large diameter myelinated fiber
How does a neuron transport enzymes produced in the neurosoma to its axon terminals?
Along microtubules
Which statement about the nervous and endocrine systems is true?
Both systems are dedicated to maintaining stable internal conditions by detecting and responding to stimuli.
bundles of nerve processes in the CNS vs PNS are called
CNS - tracts PNS - nerves
CSF is secreted into each lateral ventricle by choroid plexus and flows into the third ventricle where more is added...... CSF then flows down the cerebral aqueduct to the fourth ventricle....... Choroid plexus in the fourth ventricle adds more CSF.... Followed by.....
CSF then flows out two lateral apertures and one median aperture...... CSF fills the subarachnoid space and bathes external surfaces of brain and spinal cord..... At arachnoid villi, CSF is reabsorbed into venous blood of dural venous sinuses.
In which part of a neuron is the postsynaptic membrane usually found?
Dendrite
What property of neurons allows them to respond to changes in the environment?
Excitability
In the brain, neurons are more abundant than neuroglia. T or F
False
Neurons move material away from the neurosoma by retrograde transport. T or F
False
The nervous system employs exclusively electrical means to send messages, whereas the endocrine system communicates by means of chemical messengers. T or F
False
Oligodendrocytes
Form the myelin sheath in CNS
Where are unmyelinated nerve fibers surrounded by Schwann cells?
In the PNS
In PNS nerve fiber regeneration, how is a growing axon directed to its original destination?
It grows within a regeneration tube.
What is the primary site on a neuron for receiving signals from other neurons?
The dendrites
While both systems maintain homeostasis, how does the nervous system differ from the endocrine system?
The nervous system releases neurotransmitters between cells, while the endocrine system releases hormones into the blood.
Most metabolic and regulatory functions in a neuron happen where?
The neurosoma
In order to regenerate, a peripheral nerve fiber must have which of the following?
The neurosoma and at least some neurilemma intact
Most neurons have multiple dendrites. T or F
True
Unipolar neurons have only a single process leading away from the neurosoma. T or F
True
Some __________ neurons are specialized to detect stimuli, whereas __________ neurons send signals to the effectors of the nervous system.
afferent; efferent
interneurons
also known as community neurons most entirely within the CNS 90% of neurons are interneurons
___________________ are to the CNS, as _____________________ are to the PNS
astrocytes;satellite
when a nerve fiber is cut, the fiber distal to the injury __________ survive.
cannot
A resting membrane potential of -70 mV indicates that the ________________.
charges lining the inside of the plasma membrane are negative compared to the charges lining the outside
a resting membrane potential of -70 mV indicates that the ________________.
charges lining the inside of the plasma membrane are negative compared to the charges lining the outside
Ependymal Cells
ciliated cells resembling epithelium and produce and circulate CSF
Schwann Cells
form the myelin sheath in the PNS and insulate neurons and enhance the rate of transmission in the PNS
Which of the following are effectors?
glands
About 90% of the neurons in the nervous system are __________ neurons.
inter-
A myelin sheath is composed primarily of __________.
lipids
Microglia
macrophages of the CNS
Astrocytes
most abundant CNS glial cells and multi-functioning cells involved with neurogenesis, scar formation, etc
Anterograde Transport
movement down the axon away from soma
slow anterograde transport
movement of enzymes and cytoskeletal components down the axon to renew worn-out explasmic components
Fast Anterograde Transport
movement of enzymes and small molecules toward the distal end of the axon
What is the most common type of neuron?
multipolar
a damaged ___________ nerve fiber may regenerate if its soma is intact and some neurilemma remains.
peripheral
near the site of injury, the basal lamina and the neurilemma form a _____________ tube.
regeneration
Fast Retrograde Transport
returns used synaptic vesicles and other materials to the soma and informs the soma of conditions at the axon terminals
If a neuron is prevented from sending a neurotransmitter across a synapse to another cell, which neuron property is being inhibited?
secretion
what are the 3 overlapping functions of the nervous system?
sensory input integration motor output
Normally, sodium and potassium leakage channels differ because ___________________.
sodium ions diffuse through leakage channels into the cell, but potassium ions diffuse through leakage channels out of the cell
normally, sodium and potassium leakage channels differ because ___________________.
sodium ions diffuse through leakage channels into the cell, but potassium ions diffuse through leakage channels out of the cell
when contact is established, the _________ shrinks, and reinnervated muscle fibers regrow.
soma
Satellite Cells
surround and insulate cells of the PNS and found around the somas
The __________ division tends to prepare the body for action.
sympathetic
the tube guides the growing sprout back to the original target cells, reestablishing ___________ contact.
synaptic
The CNS gets information to decipher from the PNS, while...
the PNS receives commands from the CNS to communicate
sensory division (afferent) carry signals TOWARD the CNS
the motor division (efferent) carry signals AWAY from the CNS
Axonal Transport
two-way passage of proteins, organelles, and other material along an axon
The __________ division carries signals to the smooth muscle in the large intestine.
visceral motor
What is another name for the autonomic nervous system?
visceral motor system
