Chapter 7: The Nervous System
The average resting membrane potential of an axon is
-70mV
An axon will depolarize only if the membrane potential reaches between -70mV and -55mV. This follows the
All-or-none law
Which cells are needed for the formation of synapses in the CNS?
Astrocytes
Which type of cell lines the ventricles of the brain and help produce cerebrospinal fluid?
Ependymal cells
A nerve is a bundle of axons in the CNS
False
All axons in the PNS have a myelin sheath
False
Anterograde transport uses dynein molecular motor proteins
False
Axonal transport from the cell body to the dendrites and axon is retrograde transport
False
Both neurons and neuroglia will easily divide by mitosis
False
Destruction of astrocytes would decrease the rate at which action potential are transmitted
False
Excitable cells are incapable of maintain a constant resting membrane potential
False
Glial cells normally lose their mitotic ability prior to birth
False
Most brain tumors in adults are found within neruons
False
Nerve cells depolarize due to the influx of K+
False
Sensory nerves cause muscle contraction
False
Somatic motoro neruons innervate involuntary effecctors
False
The average resting membrane potential of a neuron is -85mV.
False
The blood-brain barrier prevents hydrophobic molecules from diffusing into the brain
False
The nerve is the basic structural and functional unit of the nervous system
False
Degeneration of spinal motor neurons in adults may be due to a lack of _____ factory
Glial-derived neutrophil (GDNF)
What type of neuron is found entirely in the CNS?
Intraneuron and association neuron are correct
Which type of cell of the CNS is phagocytotic?
Microglia
The following is NOT a structural classification of neurons?
Motor neruon
The following is Not a functional classification of neurons?
Multipolar
Blocking________ channels would prevent neuron depolarization
Na+
During an action potential
Na+ influx causes depolarization
The myelin sheaths of PNS meurons are producced by
Schwann Cells
Action potential transmission in the PNS is decreased if which cells are damaged?
Schwann cells
The minimum depolarization needed to open Na+ gates is called the
Threshold
Action potential frequency encode stimulus intensity
True
All axons in the PNS are surrounded by schwann cells
True
All cells ave a membrane potential
True
Astrocytes can be excited by changes in intracellular Ca2+ concentrations
True
Cells become more negative during hyperpollarization
True
Ganglia are clusters of nerve cell bodies located in the peripheral nervous system
True
Most motor meurons are multipolar
True
Myelinated axons transmit action potentials more rapidly than unmyelinated axons
True
Retrograde axonal transport maybe responsible for movement of herpes virus, rabies virus, and tetanus toxin from nerve terminals to the cell body
True
Schwann cells and oligiodendrocytes have similar functions
True
The blood-brain barrier may prevent medications from reaching brain tissues
True
Sensory meurons
are pseudounipolar and carry impulses towards the CNS
The blood-brain barrier results mostly from the action of ________, a type of glial cells
astrocytes
The most numerous of all cells of CNS nerbous tissue are the
astrocytes
Which division of the nervous system innervates involuntary effectors?
autonomic nervous system
Local anesthetics block conduction of action potential in sensory neurons by
binding to sodium channels
Gliotransmmitters
can stimulate neurons
The brain and spinal cord compromise the
central nervous system
The following is NOT true about axonal transport?
is a passive process
Retrograde transport
moves toward the cell body, moves membranes, vesciles and viruses, use molecular mmotor proteins of dynein.
The disease_______ is chracterized by destruction of CNS myelin sheaths and the formation of hardened scars
multiple sclerosis
Rgeneration of CNS axons may be prevented in part by inhibitory proteins in the membranes of the
myelin sheath
Axonal regeneration is inhinited by
myelin-associated inhibitory protein
What matter is
myelinated axons in the Cns
What sctructure is found around PNS axons that is not found around CNS axons?
neurilemma
Fetal neuron growth requires the actions of a group od chemicals know as
neutrophils
The gap node of exposedaxon in the myelin sheath is the
node of Ranvier
The myelin sheaths of CNS neurons are produced by
oligodendrocytes
Which of the following is true of axon
originates at the axon hillock on the cell body
The following is NOT a function of astrocytes?
phagocytose foreign materials in the CNS
The membrane of restin nerve ccells is more permeable to ______ ions than _______
poatassium, sodium
The mechanisms that allow many Na+ ions to move into the axon is
positive feedback
The following is NOT a function of neutrophins?
regeneration of injured motor neurons
Cells supporting neuron cell bodies in ganglia are termed
satellite cells
A bundle of axons in the CNS is called a/an
tract
The following is NOT true about dendrites
transmits action potential toward the cell body
Ion channels that open in response to depolarization are called
voltage-gated channels
