Nervous System: Tissue and Brain Flashcards
The structures of the nervous system are divided into two parts: the ___ nervous system and the ___ nervous system.
central
peripheral
Includes the brain and the spinal cord.
Central nervous system (CNS)
The ___ nervous system is located in the dorsal cavity. The ___ is located in the cranial cavity; the ___ cord is enclosed in the spinal cavity.
central
brain
spinal
Located outside the central nervous system (CNS) and consists of the nerves that connect the central nervous system (CNS) with the rest of the body.
Peripheral nervous system (PNS)
The nervous system performs three general functions: a ___ function, an ___ function, and a ___function.
sensory
integrative
motor
Gathers information from inside the body and from the outside environment.
Sensory nerves
Carries the information to the central nervous system (CNS). For example, information about a cat is picked up by special cells in a person’s eye and transmitted to the brain.
Sensory nerves
Sensory information brought to the central nervous system (CNS) is ___. The brain not only sees the cat but also does much more. It recalls very quickly how a cat behaves. It may determine that the cat is acting hungry or is distressed and ready to attack. The brain ___, or puts together, everything it knows about cats and then makes its plan.
interpreted
integrates
Conveys information from the central nervous system (CNS) toward the muscles and glands of the body.
Motor nerves
Carries out the plans made by the central nervous system (CNS). For example, a person decides to feed the hungry cat. Information must travel along these nerves from the central nervous system (CNS) to all the skeletal muscles needed to feed the cat.
Motor nerves
These nerves convert the plan into action.
Motor nerves
Nervous System: Central Nervous System and Peripheral Nervous System.
Nervous tissue is composed of two types of cells: the ___ and the ___.
neuroglia (ner-o-glee-a)
neurons
The nerve glue.
Neuroglia (ner-og-lee-a)
Neuroglia:
glial cells (glee-ool)
The most abundant of the nerve cells.
Neuroglia (ner-og-lee-a)
Most of these cells are located in the central nervous system (CNS).
Neuroglia (ner-og-lee-a)
These cells support, protect, insulate, nourish, and generally care for the delicate neurons.
Neuroglia (ner-og-lee-a)
Some of these cells participate in phagocytosis; others assist in the secretion of cerebrospinal fluid (CSF).
Neuroglia (ner-og-lee-a)
These cells do not conduct nerve impulses.
Neuroglia (ner-og-lee-a)
Two of the more common glial cells are the ___ and the ___ cells.
astrocytes
ependymal (a-pend-a-mal)
The most abundant of the glial cells and has the most diverse functions; they support the neurons structurally, cover the entire surface of the brain, and help form a protective barrier, called the blood-brain barrier.
Astrocytes
Star-shaped glial cells.
Astrocytes
This barrier helps prevent toxic substances in the blood from entering the nervous tissue of the brain and spinal cord.
Blood-brain barrier
Secrete nerve growth factors that promote neuron growth and enhance synaptic development.
Astrocytes
These cells line the inside cavities of the brain and assist in the formation of cerebrospinal fluid (CSF).
Ependymal (a-pend-a-mal)
True or false: glial cells undergo mitosis; and so, most primary central nervous system (CNS) tumours are composed of glial cells, such as astrocytomas.
True
The most important nerve cell in the transmission of electrical signals.
Neuron
Enables the nervous system to act as a vast communication network.
Neuron
Have many shapes and sizes: some are extremely short; others are very long, with some measuring 4 feet in length.
Neurons
Unlike glial cells, ___ are nonmitotic and therefore do not replicate or replace themselves when injured.
neurons
True or false: neurons are nonmitotic; and so, generally do not give rise to primary malignant brain tumours.
True
They carry information to the central nervous system (CNS).
Sensory neurons
Carry information away from the central nervous system (CNS).
Motor neurons
Found only in the central nervous system (CNS) and form connections between sensory and motor neurons within the central nervous system (CNS).
Interneurons
They play an important role in integrating all sensory information and the appropriate motor responses.
Interneurons
Three Functions of the Nervous System.(A) Sensory function. (B) Integrative function. (C) Motor function.
Neuroglia: Astrocytes and Ependymal Cells
Structure of a Neuron. (A) Dendrites, cell body, axon, and axon terminals. (B) Structure surrounding the axon, showing the myelin sheath, the nodes of Ranvier, and the neurilemma.
The three parts of the neuron are the ___, ___ ___, and ___.
dendrites (den-drites)
cell body
axon (ax-on)
Tree-like structures that receive signals from other neurons and then transmit the signals toward the cell body.
Dendrites (den-drites)
One neuron may have thousands of ___, whereas other neurons have fewer ___. The neuron with the greater number of ___ can receive signals from many other neurons.
dendrites x3 (den-drites)
Contains the nucleus and is essential for the life of the cell.
Cell body
Usually receives thousands of signals from the dendrites and ‘decides’ on the signal it wants to send to the axon.
Cell body
A long extension that transmits signals away from the cell body.
Axon
The end of the axon undergoes extensive branching to form many axon ___.
terminals
The chemical neurotransmitters are stored here.
Axon terminals
An enlarged view of the axon shows several unique structures: the ___ ___, the ___, and the ___ of ___.
myelin sheath (my-a-lin) (sheeth)
neurilemma (ner-a-lem-a)
nodes / Ranvier (ron-vee-eh)
Most long nerve fibres of both the peripheral and central nervous system (CNS) are encased by a layer of this white fatty material.
Myelin sheath (my-a-lin) (sheeth)
Protects and insulates the axon.
Myelin sheath (my-a-lin) (sheeth)
Nerve fibres covered by myelin are said to be ___.
myelinated (my-a-lin-ated)
Some neurons are not encased in myelin and are called ___ neurons.
unmyelinated (un-my-a-lin-ated)
Begins during the fourth month of fetal life and continues into the teenage years.
Myelination (my-a-lin-ation)
True or false: because some axons of immature motor neurons lack myelination, the movements of an infant are slower and less coordinated than those of an older child.
True
True or false: severely restricting the fat intake of an infant or young child is unwise, because the child is still laying down myelin.
True
True or false: the formation of myelin sheath differs in the peripheral and central nervous systems (CNS).
True
The nuclei and cytoplasm of the Schwann cells lie outside the myelin sheath and are called the ___.
neurilemma (ner-a-lem-a)
Form the myelin sheath that surrounds the axon in the peripheral nervous system (PNS).
Schwann cells (shwon)
Important in the regeneration of a severed nerve.
Neurilemma (ner-a-lem-a)
In the central nervous system (CNS), the myelin sheath is formed not by Schwann cells but by ___.
oligodendrocytes (a-ligo-den-dra-cites)
True or false: oligodendrocytes are a type of glial cell.
True
In oligodendrocytes, because there are no Schwann cells, there is no ___. The lack of the ___ surrounding the axons accounts, in part, for the inability of the central nervous system (CNS) neurons to regenerate.
neurilemma x2 (ner-a-lem-a)
True or false: failure of the neurons of the central nervous system (CNS) to regenerate is not fully explained by the lack of neurilemma; other factors include the formation of scar tissue and the lack of critical nerve growth factors.
True
Axonal areas not covered by myelin and appear at regular intervals along the myelinated axon.
Nodes of Ranvier (ron-vee-eh)
The tissue of the central nervous system (CNS) is ___ or ___.
white
grey
White matter is white because of the ___ axons, whereas grey matter is made up of ___ axons, cell bodies, interneurons, and synapses.
myelinated (my-a-lin-ated)
unmyelinated (un-my-a-linated)
Clusters of cell bodies located in the central nervous system (CNS).
Nuclei (new-clee-i)
Small clusters of cell bodies in the peripheral nervous system (PNS).
Ganglia (gang-glee-a)
True or false: patches of grey called the basal nuclei are located in the brain; although, sometimes, these patches of grey are called basal ganglia, despite their location in the central nervous system (CNS).
True
Allow the nervous system to convey information rapidly from one part of the body to the next. For example, a stubbed toe makes itself known almost immediately. Think of how fast the information travels from your toe, where the injury occurred, to your brain, where the injury is interpreted as pain.
Neurons
Information is carried along the neuron in the form of a ___ ___.
nerve impulse
An electrical signal that conveys information along a neuron.
Nerve impulse
The nerve impulse is called the ___ ___.
action potential
There are two phases of an action potential: ___ and ___.
depolarization
repolarization
Refers to the electrical charge difference across the membrane of the resting neuron.
Resting membrane potential
The ___ of a resting neuron is more negative (−) than the ___ (+).
inside
outside
The ___ cell is said to be polarized. As long as the neuron is polarized, no nerve impulse is being transmitted. The cell is quiet or ___.
resting x2
When the neuronal membrane is stimulated, a change occurs in the cell’s electrical state. In the resting (___) state, the inside of the cell is negative. When the cell membrane is stimulated, the inside becomes positive. As the inside of the cell changes from negative to positive, it is said to ___.
polarized
depolarize
Very quickly, the inside of the cell again becomes negative; in other words, it returns to its resting state or ___.
repolarizes
Unless the cell ___, it cannot be stimulated again.
repolarizes
Nerve Impulse (Action Potential). (A) Polarization. (B) Depolarization. (C) Repolarization.
The degree of depolarization that must be attained for the neuron to be fully depolarized.
Threshold potential
If ___ potential is not achieved by the stimulus, the signal decays, and the cell returns to the resting membrane potential.
threshold
Under this condition the action potential fails to fire.
Threshold potential
The resting state is the result of the numbers and types of ___, both positive (cations) and negative (anions), located inside the neuron.
ions
Pumped in by ATP-driven pumps in the cell membrane.
Ions
The chief intracellular cation.
Potassium K+
In the ___ state, some of the K+ ions leak out of the cell, taking with them the ___ charge. The lost ___ charge and the excess anions trapped in the cell make the inside of the cell ___.
resting
positive x2
negative
The outward leak of ___ is responsible for the resting membrane potential.
potassium K+
When the neuron is stimulated, the permeability of the neuronal membrane changes in a way that allows ___ ions to diffuse rapidly across the membrane into the cell, carrying with it a ___ charge.
sodium Na+
positive
It is the rapid inward diffusion of ___ that causes depolarization.
sodium NA+
Soon after the cell depolarizes, the neuronal membrane undergoes a second change. The change in the membrane permeability does two things: (1) it stops additional diffusion of sodium (Na+) ___ the cell, and (2) it allows potassium (K+) to rapidly diffuse ___ of the cell.
into
out
The ___ diffusion of potassium (K+) decreases the positive charge from the inside of the cell, leaving behind the negatively charged anions. Thus, the ___ movement of potassium (K+) causes repolarization and a return to the resting state.
outward x2
Membrane pumps restore intracellular ion concentrations; sodium (Na+) is pumped ___ of the cell, while potassium (K+) is pumped ___ the cell.
out
into
True or false: the repolarizing phase of the nerve impulse is NOT caused by the active transport pumps.
True
Repolarization is caused by the rapid outward ___ of potassium (K+).
diffusion
To convey information, a nerve impulse (___ ___) must move the length of the neuron, from the ___ ___ to the ___ ___.
action potential
cell body
axon terminal
True or false: because of the ability of each nerve impulse to depolarize the adjacent membrane, the nerve impulse moves toward the axon terminal much like a wave.
True
Increases the movement of the nerve impulse along the axonal membrane.
Myelination (my-a-lin-a-tion)
The nerve impulse arrives at the axon from the cell body but cannot develop on any part of the membrane covered with ___. The nerve impulse can, however, develop at the ___ of ___, the bare axonal membrane.
myelin (my-a-lin)
nodes / Ranvier (ron-vee-eh)
In a myelinated fibre, the nerve impulse jumps from ___ to ___, much like a kangaroo, to the end of the axon.
node x2
The nerve impulses ‘jumping’ from node to node to the end of the axon is called ___ ___.
Saltatory conduction (salt-a-tory), from the Latin word saltare, meaning ‘to leap’.
Increases the speed with which the nerve impulse travels along the nerve fibre.
Saltatory conduction (salt-a-tory)
___ fibres are considered fast-conducting nerve fibres.
Myelinated (my-a-lin-ated)
The Ionic Basis of the Nerve Impulse. (A) Polarization. (B) Depolarization. (C) Repolarization.
Helps information move chemically from one neuron to the next.
Synapse (sin-aps)
A space (much like the neuromuscular junction) that exists because the axon terminal of neuron A (presynaptic neuron) does not physically touch the dendrite of neuron B (postsynaptic neuron).
Synaptic cleft (sin-ap-tic)
The dendrite of neuron B contains ___ sites.
receptor
Places on the membrane to which the neurotransmitters bind. For example, acetylcholine (ACh) binds to the receptors on dendrite B.
Receptor sites
True or false: each receptor site has a specific shape and accepts only those neurotransmitters that ‘fit’ its shape.
True
Parts of a Synapse. The steps in the transfer of information across the synapse.
Four Major Areas of the Brain: Cerebrum, Diencephalon, Brain Stem, and Cerebellum.
(A) Lobes of the cerebrum: frontal lobe, parietal lobe, temporal lobe, and occipital lobe. (B) Functional areas of the cerebrum.
Diencephalon, Brain Stem, and Cerebellum.
Three Layers of Meninges: The Dura Mater, Arachnoid Mater, and Pia Mater. Note the subarachnoid space, arachnoid villi, and dural sinuses.
Cerebrospinal Fluid: Formation (Choroid Plexus); Circulation Through the Ventricles, Within the Subarachnoid Space, and in the Central Canal; and Drainage Through the Arachnoid Villi and Dural Sinuses.
