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Flashcards in nervous system - histo lec Deck (61):
1


receive stimuli from the environment or from different organs of the body
transmit impulses to the brain and spinal cord

Nervous tissues

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Properties of Nervous Tissues:

1. Irritability
- react to various stimuli
2. Conductivity
- transmit impulses

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A. Anatomical Division

CNS – brain and spinal cord
PNS – Peripheral Nervous System
- nerves outside the CNS and their associated ganglia

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B. Functional Division

Sensory component – transmits signal ( electrical impulses) to the CNS
Motor component – transmits impulses from the CNS to various structures of the body
1. somatic
2. autonomic

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C. Consists of two types of cells

Nerve cells (neurons) – conduct electrical impulses
glial (neuroglial cells – support, nurture, and protect the neurons

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2 elements of nervous tissue:

- structural and functional units
- receive and transmit impulses

1. Neurons

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2 elements of nervous tissue:
- glial cells
- specialized type of connective tissue
- non neuronal cells of the CNS and PNS

2. Neuroglia

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Nucleus – “owl-eye nucleus”
-abundant in ?

euchromatin

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cytoplasmic organelles in neurons

Cytoplasmic organelles
a. Nissl bodies - polysomes and RER
most abundant in motor neuron
b. Golgi complex and mitochondria
c. melanin- containing granules
d. Lipofuscin- containing granules
e. lipid droplets

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- polysomes and RER most abundant in motor neuron

Cytoplasmic organelles
a. Nissl bodies

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3. cytoskeletal filaments of neuron

a. neurofilaments
b. microtubules
c. actin filaments

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receive stimuli from sensory cells, axons or other neurons

dendrites

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and convert these signals into action potentials that are transmitted toward the soma

dendrites

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presence of arborized terminals


dendrites

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spines on the surface

dendrites

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cytoplasm lacks Golgi complex

dendrites

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1. conducts impulses away from the soma to the axon terminals






AXONS

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2. up to 100 cm length

AXONS

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3. originates at the axon hillock

AXONS

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4. with axon collateral

AXONS

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5. axoplasm with SER, RER, mitochondria

AXONS

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8. Initial segments for site if various excitatory and inhibitory stimuli

AXONS

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7. terminates into axon terminals

AXONS

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6. membrane is called axolemma

AXONS

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- many dendrites and one axon
ex. neurons in the CNS



1. Multipolar neuron

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- one axon and one dendrite
ex. neurons in the retina of the eye and neurons in the nasal cavity

2. Bipolar neuron

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- one process extending from the cell body that divides into an
axon and dendrite
ex. Spinal and cranial ganglia

3. Unipolar neurons (pseudounipolar)

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>Protect and support neurons
>Do not conduct impulses or form impulses or form synapses
>Cell Division
>Revealed only in histologic sections by special gold and silver stains

neuroglial cells

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Are the largest of the neuroglial cells



astrocytes

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“perivascular feet” that surround blood vessels and pia matter

astrocytes

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glial cell
Supply energy for metabolism

astrocytes

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Forms a protective sealed barrier between the pia mater and the nervous tissue of the brain and spinal cord

astrocytes

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Scavenge ions or debris from neuronal activity

astrocytes

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glial cell
Structural support

astrocytes

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Form scar tissues after injury to CNS
(e.g cerebral infarct)

astrocytes

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Two types of Astrocytes

gray matter
branched processes envelop blood vessels, neurons and synaptic areas
Blood-brain barrier
With GFAP



Protoplasmic

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Two types of Astrocytes
white matter
Long slender processes

fibrous

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protects the CNS from fluctuating levels of electrolytes,hormones, and tissue metabolites
circulating in the blood vessels

The blood–brain barrier

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Live symbiotically with neurons in the CNS
Located both in gray and white matter

Oligodendrocytes

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Produces myelin that insulates and protects axons

Oligodendrocytes

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increases the speed of transmission of the action potential down the axon.


Myelin sheath:

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decreases the metabolic needs of the neuron by reducing the total amount of ion exchange that happens during an action potential.

Myelin sheath:

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Flat cells, few mitochondria and GA
From neural crest cells


Schwann Cells

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For regeneration of nerve fiber

Schwann Cells

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Protect and insulate neuron in PNS

Schwann Cells

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- phagocytic
- remove bacteria and cell debris from the CNS
- distributed in GM and WM
- secrete cytokines

3. Microglia

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line the neural tube and ventricles of the brain and spinal cord



Ependymal cells

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transport and circulation of the CSF

Ependymal cells

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no basal lamina

Ependymal cells

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low columnar/cuboidal GLIAL CELL

Ependymal cells

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Contribute to formation of choroid plexus

Ependymal cells

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Functional apposition where signals are transmitted from one neuron to another or from neuron to other type of cell (e.g. muscle)

synapse

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- enclosed by myelin sheath
- prevents loss of nerve impulse
- circular constrictions (Nodes of Ranvier)
- internodal segments or Schwann segments

Myelinated nerve fibers

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- naked axons
- devoid of myelin sheath
- neurolemma

Unmyelinated nerve fibers

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classification of peripheral nerves as to function

Sensory – contain afferent fibers (to the CNS)

Motor – contain efferent fibers (from the CNS)

Mixed – contain both afferent and efferent fibers

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Are encapsulated aggregations of neuronal cell bodies (soma) outside the CNS




GANGLIA

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Two types of ganglia

Autonomic ganglia
Craniospinal ganglia

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mostly myelinated nerve fibers, some unmyellinated and glial cells


White matter –

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– mostly neuronal cell bodies, unmyelinated
fibers, and neuroglial cells

Gray matter

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Degeneration of distal axonal segment
(anterograde changes)

“Wallerian degeneration”

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2. Regeneration of proximal axonal segment

(retrograde changes)

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