Nervous Tissue Lab Flashcards
It is made up of closely packed cells that are separated by very little amount of intercellular substance
Nervous tissue
Nervous tissue arises from embryonic ________
ectoderm
The nervous tissue in the body is organized to comprise the __________
Nervous system
Nervous system is anatomically divided into two divisions:
1.) Central nervous system (CNS)
2.) Peripheral nervous system (PNS)
CNS refers to the _______ and _______.
brain and spinal cord
True or False: PNS relates to other nervous tissue in the body.
True
The cells of nervous tissue consists of:
1.) Neurons (nerve cells)
2.) Supporting cells (neuroglial cells or glial cells
are the functional units of nervous tissue that perform all functions of the tissue, they are highly specialized cells that exhibit irritability and conductivity to a high degree
Neurons
are the most morphologically variable cell type in the body
Neurons
characterized the ventral gray matter of the spinal cord and the motor nuclei of the brain stem
stellate neurons
neurons that are present in the cerebral cortex
pyramidal neurons
flask-shaped neurons that give off a dendrite which arborizes like a tree are seen in the middle layer of the cerebellar cortex
Purkinje cells
A neuron consists of a cell body called
perikaryon or soma
Neurons are of two kinds of processes:
1.) axon
2.) dendrite
________ are terminally differentiated cells that are incapable of cell division
Neurons
True or False: axons and dendrites can regenerate when damaged, provided the cell body is intact
True
cell membrane of the nervous tissue is known as
neurolemma
cytoplasm of the nervous tissue is known as
neuroplasm
deeply basophilic, granular masses parts of the neuron’s rER
Nissl bodies
are abundant throughout the perikaryon and are found in dendrites, but they are notably absent in the axon and axon hillock
Nissl bodies
the area of the perikaryon where the axon originates
axon hillock
help in preventing the degeneration of the neuron by not allowing the accumulation of strong oxidizing agents and by playing a role in detoxifying noxious substances
peroxisomes
True or False: Centrosome of a neuron is atypical because it does not contain centrioles, but it is the source of the microtubules that the cells need.
True
are present in nerve cells of the substantia nigra of the midbrain, the locus coeruleus near the fourth ventricle, and the spinal and sympathetic ganglia
Melanin granules
are present in the neurons in the globus pallidus
Iron granules
cytoskeleton of neurons is formed by three types of fibrillar elements, collectively referred to as
neurofibrils
Three types of fibrillar elements
- microfilaments
- intermediate filaments
- microtubules
are present in all neurons but are particularly well-developed in large ones and it extend into the axon and the dendrites
Neurofibrils
are the finest of the fibrillar elements in neurons and are made up of the fibrillar type of actin (F-actin) that consists of two strands of helically-arranged, polymerized G-actin filaments
Microfilaments
provide internal support for the cell and fix the diameter of dendrites and axons
Neurofilaments
microtubules in neurons often referred as
neurotubules
provide internal support for the neurons and strengthen synapses
neurotubules
_______ conducts impulses away from the cell body
axon
_______ carries impulses towards the cell body
dendrites
only one process, an axon is present, and it exists in early embryonic life but is rarely present in adults
Unipolar
a single process, morphologically an axon, leaves the body, but soon bifurcates, neurons are exemplified by sensory neurons that are present in the craniospinal ganglia
pseudounipolar
a processes when a single dendrite and an axon at opposite poles of the cell body
bipolar
a processes when numerous dendrites are present (most neurons are of this type)
multipolar
A type of neurons that receive and transmit stimuli to the CNS
Sensory neurons (afferent neurons)
A type of neurons that transmit impulses from the CNS to effector cells
Motor neurons (efferent neurons)
A type of neurons that convey impulse from one neuron to another
Interneurons (association neurons)
provide most of the receptive surface of the neuron
Dendrite
cytoplasm of axon
axoplasm
is usually more slender than a dendrite but is typically longer
axon
the longest axons in the human body are those that form the _______
sciatic nerve
An axons forms small, rounded swellings called
boutons (terminals)
An axonal transport that involves movement of substances from the perikaryon to the axon
anterograde
An axonal transport that involves the transport of substances from axon terminals to the perikaryon
retrograde
All axons are enveloped by a sheath of cells called
neurilemmal sheath
In PNS neurilemmal sheath is more commonly called
Schwann sheath
Schwann sheath is formed by flattened cells with flattened nuclei called
Schwann cells
The points of discontinuity between successive Schwann cells are referred to as
Nodes of Ranvier
larger axons in the PNS are enveloped by a material that is highly refractile in fresh specimen but black in tissues fixed with osmium tetroxide
Myelin
The structure that forms around the axon, which lies internal to the Schwann sheath, is called
Myelin sheath
True or False: in CNS, there is no Schwann cells
True
In the CNS, the functions of the Schwann cells are performed by cells called
Oligodendrocytes
In the PNS, every nerve fiber is enveloped by some amount of connective tissue that is referred to as
endoneurium
True or False: In the CNS, nerve fibers are invested by connective tissue.
False
Is a point of contact between a neuron and another cell, the site of transmission of a nerve impulse which can either be excitatory or inhibitory in nature
synapse
it allows neurons to communicate with each other or with effector cells and accomplish their integration and control functions
synapse
Synapses are categorized into two types:
- electrical
- chemical
these synapses occur rarely and they exists between some neurons in the brain stem, retina, and cerebral cortex
Electrical synapses
Electrical synapses consists of ________ that are similar to those found in between epithelial and other cells in which enable neighboring neurons to communicate with each other by allowing adjacent cells to exchange molecules and small ions
gab junctions
these synapses are more common and in fact most synapses that neurons make are of this type
chemical synapses
In a chemical synapses, the nerve impulse is transmitted from one neuron to another cell by means of chemical substances called
neurotransmitter
At present, there are about ____ known neurotransmitters
50
The neuron that communicates the impulse in a chemical synapse is called
presynaptic neuron
The cell or neuron that receives the impulse is called
postsynaptic neuron
The part of the presynaptic neuron that participates in a synapse is usually an ______
axon terminal (bouton)
axolemma of presynaptic neuron is thickened and is referred to as
presynaptic membrane
cell membrane of postsynaptic cell is called
postsynaptic membrane
The presynaptic and postsynaptic membranes are separated by a small gap called the
synaptic cleft
The presynaptic membrane, synaptic cleft, and postsynaptic membrane comprise a _______
synapse
the axon of a neuron synapses with a dendrite or a perikaryon of another neuron, forming ________ and __________
axodendritic and axosomatic synapses
the axon of a neuron synapses with the axon of another neuron to form an _________
axoaxonic synapse
are cells that protect neurons; aid them in performing their functions by creating and maintaining an appropriate environment where neurons can carry out their function; and play a role in neural nutrition
Neuroglial cells
In the CNS, there are four types of neuroglial cells:
- astrocytes
- oligodendrocytes
- microglia
- ependymal cells
In the PNS, there are two types of neuroglial cells:
- Schwann cells
- satellite cells
Astrocytes and oligodendrocytes are sometimes collectively referred to as
macroglia
the neuroglial cells, except microglia, arise from _______
embryonic ectoderm
microglia evidently arise from ________
embryonic mesoderm
True or False: Neuroglial cells have the capacity to divide by mitosis
True
are the largest and most abundant of the neuroglial cells, they are star-shaped and have numerous, branching processes
Astrocytes
a type of neuroglial cells that form scar tissue in damaged areas
Astrocytes
are smaller, have fewer and shorter process than astrocytes, have scanty cytoplasm, nucleus usually ovoid or spherical
Oligodendrocytes
are smaller than astrocytes and oligodendrocytes, and are distributed throughout the CNS, it nuclei are small and elongated while its cytoplasm is scanty and contains many lysosomes
Microglia
are phagocytes that remove cellular debris from sites of injury or normal cell turnover
Microglia
_________ cells comprise the simple cuboidal epithelium that lines the cavities of the CNS, it possess short cilia and microvilli
Ependymal cells
cells that form the neurilemmal and myelin sheaths or peripheral nerves
Schwann cells
are small, flattened cells that surround the cell bodies of neurons that are in ganglia, they are the PNS counterparts of astrocytes
Satellite cells
It is an extraordinary complex but highly integrated communication network that receives, stores, processes, and sends out voluminous amounts of information simultaneously and instantaneously.
Nervous System
True or False: the CNS has no connective tissue stroma, hence, the nervous tissue comprises brain and the spinal cord is soft and jelly-like
True
Internal to the bony structures that protect the brain and spinal cord are further protected by enveloping membranes called _______ made up of connective tissue
meninges
There layers of the Meninges:
- dura mater or pachymeninx
- arachnoid membrane
- pia mater
the outermost layer of meninges that is firm and made up of dense collagenous connective tissue
dura mater / pachymeninx
the middle layer of meninges
arachnoid membrane
the innermost membrane layer of meninges that is closely applied to the brain
pia mater
protects the central nervous system by acting as a water cushion and plays an important role in the metabolism of nervous tissue
CSF
CSF is regularly drained into the venous side of the circulation via specialized areas of the arachnoid membrane called
arachnoid villi
The ______ plexus are the chief sources of CSF. Located on the roof of the third and fourth ventricles of the brain and in parts of the wall of the two lateral ventricles
choroid plexus
the ependyma of the choroid plexus acts as a __________
blood-CSF barrier
In the CNS, neurons that have long axons that leave either the CNS or the gray matter and terminate at some distance in another part of the gray matter are termed ________
Golgi type I neurons
Neurons that have relatively short axons that do not leave the region of the gray matter where their cell bodies lie are called ______
Golgi type II neurons
The __________ keeps the nerve fibers within the fascicle together
perineurium
Nerves whose cell bodies are in the brain are called
cranial nerves
Nerves whose cell bodies are in the spinal cord are called
spinal nerves
There are _____ pairs of cranial nerves and ____ pairs of spinal nerves
12 pairs of cranial nerves
31 pairs or spinal nerves
The terminations of nerves in epithelial, connective, and muscles tissues are called
nerve endings
consists of the naked leaf-like terminal of an axon that is in contact with a Merkel cell
Merkel discs
are made up of naked axon terminals enclosed by a lamellated connective tissue capsule
Encapsulated nerve endings
the largest of the sensory nerve endings
Vater-Pacinian corpuscles
is a small, spindle-shaped structure seen in the dermis of the skin, tendons, and ligaments. It consists of bulb-like expansions of the terminal branches of a naked axon that are enclosed by a very thin connective tissue capsule
Ruffini’s corpuscle
encapsulated nerve endings that are found in the conjunctiva and mucous membrane of the lips, dermis, glans penis, and clitoris
End bulbs of Krause
The ______ corpuscle is seen in the dermis of the skin of the fingers, toes, palms, and soles. It is smaller than a Vater-Pacinian corpuscle
Meissner’s corpuscle
this nerve endings are responsible for transmitting the stimulus that commands muscle fibers to contract and glandular cells to secrete
Motor nerve endings
The ____________ nervous system responds to impending danger or stress. It is responsible for the increase of one’s heartbeat and blood pressure, sense of excitement, and other physiological changes that occur in “flight or fight” situations.
Sympathetic nervous system
The ___________ nervous system is called upon during resting and relaxing situations. It is responsible for things such as contraction of the pupil, slowing of heart rate, and dilation of the blood vessels.
Parasympathetic nervous system
The _______ nervous system is responsible for regulating the activities of the digestive tract.
Enteric nervous system
