Nervous Tissue and the nervous system histology Flashcards
the ____ component of the nervous system transmits electrical impulse to the CNS
sensory
the ___ component of the nervous system transmits impulses from the CNS to various structures of the body
motor
the motor component is divided into the ____ and _____ systems
somatic and autonomic
nervous tissue contains these two types of cells
nerve cells/neurons and glial/neurological cells
these cells conduct electrical impulses
neurons/nerve cells
these cells support, nurture, and protect neurons
glial/neuroglial cells
a cell body and its processes, which are usually multiple dendrites and a single axon
neuron
type of neuron in some sense organs like the vestibulocochlear mechanism
bipolar
type of neuron in spinal and cranial sensory ganglia
pseudounipolar
multipolar neurons
motor neurons
unipolar or pseudounipolar
multipolar/motor
Sensory neurons
receive stimuli from the internal and external environments. They conduct impulses to the CNS for processing and analysis.
Interneurons
connect other neurons in a chain or sequence. They commonly connect sensory and motor neurons and also regulate signals transmitted to neurons.
Motor neurons
conduct impulses from the CNS to other neurons, muscle, and glands.
region of a neuron containing the nucleus, various cytoplasmic organelles and inclusions, and cytoskeletal components.
neuronal cell body
composed of polysomes and rER. They appear as clumps under light microscopy and are most abundant in large motor neurons.
Nissl bodies
receive stimuli (signals) from sensory cells, axons, or other neurons and convert these signals into small electrical impulses (action potentials) that are transmitted toward the soma.
dendrites
_____ on the surface of dendrites increase the area available for synapse formation with other neurons.
spines
conduct impulses away from the soma to the axon terminals without any diminution in their strength
axons
axons originate
axon hillock
specialized region of the soma that lacks rER, ribosomes, Golgi cisternae, and Nissl bodies but contains many microtubules and neurofilaments
axon hillock
cherry red spots on macula
Tay Sachs disease
lysosomal storae disease where glycolipids (GM2 gangliosides) accumulate in the lysosomes of neurons
Tay Sachs is a deficiency of ____ and results in _____
the enzyme hexosaminidase A - so glycoplipds accumulate in the lysosomes
degenerative changes in the CNS
common age of death in Tay Sachs
demographic
age 4
european jewish descent
differential for cherry red spots on macula densa
- Tay-Sachs disease
- Niemann- Pick (sphingomyelin accumulation)
- central renal artery occlusion
5 types of neuroglial cells
- astrocytes
- oligodendrocytes
- microglia
- schwann cells
- ependymal cells
frequency of neuroglial cells to neurons
10:1
do the neuroglial cells conduct impulses?
no! they do not form synapses with other cells either
constitute 50% of intracranial tumors
neuroglial tumors
These tumors range in severity from slowly growing _______ to rapidly growing fatal ______.
benign oligodendrogliomas
malignant astrocytomas
_________ reside mostly in gray matter and have branched processes that envelope blood vessels, neurons, and synaptic areas
protoplasmic astrocytes
largest type of neuroglial cell
astrocytes
functions of astrocytes
scavenge ions/debris, supply energy for metabolism, contribute to the glia limitans, provide sturctural support, form scar tissue after CNS injury, covers axon at nodes of ranvier in CNS, contributes to blood brain barrier
the barrier between the pia mater and the nervous tissue of the brain and spinal cord
glia limitans - part of astrocytes
reside mostly in white matter and have long, slender processes with few branches
fibrous astrocytes
intermediate filaments of astrocytes contain this protein
GFAP glial fibrillar acidic protein
type of junctions in continuous somatic capillaries within the blood brain barrier
tight junctions with no fenestrations within cells
characteristics important for the blood brain barrier
protoplasmic astrocytes along with continuous/somatic capillaries - not fenestrated and tight junctions
necessary for the survival of neurons in the CNS
oligodendrocytes
location of oligodendrocytes
both gray and white matter
»Each oligodendrocyte produces myelin for ___ axons, although only one axon is shown in the diagram.
several
microglial
small, phagocytic cells derived from mononuclear cells in bone marrow
Activated microglial cells become antigen-presenting cells and secrete _______
cytokines
Brains of patients with ___ and ___ possess large populations of microglial cells. Although these microglia do not attack neurons, they produce cytokines that are toxic to neurons.
AIDS and HIV-1
cells that protect and insulate neurons in the PNS
schwann cells
Form either unmyelinated or myelinated coverings over neurons
schwann cells
Produce endoneurium (the connective tissue surrounding a neuron)
schwann cells
a single schwann cell can insulate ___ a single axon
ONLY
A myelin sheath consists of several Schwann cell _____ wrapped around a single axon.
plasmalemmae
what are the blue wavy lines?
schwann cell nuclei
Line the neural tube and ventricles of the brain
ependymal cells
ependymal cells sometimes possess ___ in the brain to move CSF
cilia
Modified ependymal cells contribute to the formation of the _____ which forms CSF in the ventricles.
choroid plexus
myelin sheath is produced by ___ in CNS and ___ in the PNS
oligodendrocytes in the CNS and schawann cells in the PNS
»Consists of several spiral layers of the plasma membrane of an oligodendrocyte or Schwann cell wrapping around the axon
myelin sheath
the myelin sheath is_______ along the length of the axon; is interrupted by gaps called nodes of Ranvier
not continuous
Regions along the axon that lack myelin and represent discontinuities between adjacent Schwann cells or oligodendrocytes
nodes of ranvier
____ is a long, flexible protein, composed of an alpha–chain and a beta–chain, that forms tetramers and provides a scaffold for structural reinforcement.
spectrin
during high speed car accidents or shaken baby syndrome, the sudden acceleration causes sheer damage to the axons at the interface between white and gray matter causing diffuse axonal injury. Exam displays irreparable cleavage of ____
spectrin
»Multipolar neurons and pseudounipolar neurons in the somatic nervous system are _____ myelinated.
HEAVILY
Preganglionic neurons in the autonomic nervous system are ____ myelinated.
lightly
motors for vesicle or organelle movement within the axon
kinesin and dynein
Postganglionic neurons in the autonomic nervous system are typically (un)/myelinated.
unmyelinated
connective tissue layers of nerves
- epineurium
- perineurium
- endoneurium
the layer of fibrous dense connective tissue (fascia) that forms the external coat of nerves
Epineurium
surrounds each bundle of nerve fibers (fascicle). Its inner surface consists of layers of flattened cells joined by tight junctions that prohibit passage of macromolecules.
Perineurium
the thin layer of reticular fibers, produced mainly by Schwann cells, that surrounds individual nerve fibers.
Endoneurium
contain afferent fibers and carry sensory signals only from the internal/external environments to the CNS
sensory nerves
contain efferent fibers and carry signals only from the CNS to effector organs
motor nerves
the most common type of nerve, containing both afferent and efferent fibers and thus carry both sensory and motor signals.
mixed nerves
ganglia
Encapsulated aggregations of neuronal cell bodies outside the CNS
types of ganglia
autonomic and sensory
motor ganglia in which axons of preganglionic neurons synapse on postganglionic neurons.
autonomic ganglia
Cell bodies are irregular in shape, far apart from one another, and surrounded by only a few satellite cells (nourishing cells) to make room for synapses
autonomic ganglia
Preganglionic fibers synapse with _____ postganglionic cell bodies in the ganglion
multipolar
where are the autonomic parasympathetic ganglia
(1) Ciliary
(2) Pterygopalatine
(3) Otic
(4) Submandibular
(5) Ganglia near or within the walls of organs.
where are the sympathetic autonomic ganglia
(1) Collateral or paravertebral ganglia, which are the numerous ganglia of the sympathetic chain
(2) Preaortic or prevertebral ganglia (e.g., celiac, superior mesenteric, aorticorenal, and inferior mesenteric ganglia).
Unlike autonomic ganglia, sensory ganglia do not possess
synapses
sensory ganglia cell bodies are ____ neurons
pseudounipolar neurons
gray matter of brain
Contains neuronal cell bodies, many unmyelinated fibers, some myelinated fibers, and neuroglial cells
white matter of brain
Contains mostly myelinated nerve fibers but also some unmyelinated nerve fibers and neuroglial cells
Spinal cord _______ appears in the shape of an H in cross sections of the spinal cord
gray matter
A small central canal, lined by ____ cells, is at the center of the crossbar in the H in the cross section of the spinal cord
ependymal
how many layers of cerebral cortex
6
- molecular
- external granular layer
- external pyramidal layer
- internal grandular layer
- internal pyramidal lyaer
- multiform layer
label the layers
description of alzheimers
Characterized by loss of neurons and synapses mainly within the cerebral cortex followed by atrophy of the individual cerebral lobes
in alzheimers, nPatients develop_____and____ that render the neurons nonfunctional.
β–amyloid plaques
and
neurofibrillary tangles
_____disease is caused by loss of dopaminergic neurons from the ______
parkinson
substantia nigra
Silver-staining spherical aggregation of tau proteins in neurons are ______
Pick bodies
Pick disease characteristics
progressive dementia, changes in personality
Circular groupings of dark tumor cells surrounding pale neurofibrils are Homer-Wright rosettes (neuroblastoma, medulloblastoma).
3 layers of cerebellar cortex
molecular layer
purkinje cell layer
granular layer
A ____ has a cell body that is bulbous with one or two large primary dendrites branching very extensively (“arborized”) into the outer molecular layer and a single myelinated axon on the opposite side of the cell body.
purkinje cell
Negri bodies of rabies
Eosinophilic cytoplasmic inclusion bodies in the cytoplasm of cerebellar and hippocampal neurons
neuronal cell death may be followed by proliferation of _____
neuroglia, which fills in areas left by dead neurons
Degeneration of a distal axonal segment (anterograde changes).
The axon and its myelin sheath, which are separated from the cell body, degenerate completely (wallerian degeneration), and the remnants are removed by macrophages. Schwann cells proliferate, forming a solid cellular column that is distal to the injury and that remains attached to the effector cell.
Regeneration of proximal axonal segment (retrograde changes).
The distal end, closest to the wound, initially degenerates, and the remnants are removed by macrophages. Growth at the distal end then begins (0.5 to 3 mm/day) and progresses toward the column of Schwann cells. Regeneration is successful if the sprouting axon penetrates a Schwann cell column and reestablishes contact with the effector cell.
Transection of peripheral axons
induces changes in the cell body, including chromatolysis (disruption of Nissl bodies with a concomitant loss of cytoplasmic basophilia), increase in cell body volume, and movement of the nucleus to a peripheral position.
