nervous system - histo lec Flashcards
receive stimuli from the environment or from different organs of the body
transmit impulses to the brain and spinal cord
Nervous tissues
Properties of Nervous Tissues:
- Irritability
- react to various stimuli - Conductivity
- transmit impulses
A. Anatomical Division
CNS – brain and spinal cord
PNS – Peripheral Nervous System
- nerves outside the CNS and their associated ganglia
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
C. Consists of two types of cells
Nerve cells (neurons) – conduct electrical impulses glial (neuroglial cells – support, nurture, and protect the neurons
2 elements of nervous tissue:
- structural and functional units
- receive and transmit impulses
- Neurons
2 elements of nervous tissue:
- glial cells - specialized type of connective tissue - non neuronal cells of the CNS and PNS
- Neuroglia
Nucleus – “owl-eye nucleus”
-abundant in ?
euchromatin
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
- polysomes and RER most abundant in motor neuron
Cytoplasmic organelles
a. Nissl bodies
- cytoskeletal filaments of neuron
a. neurofilaments
b. microtubules
c. actin filaments
receive stimuli from sensory cells, axons or other neurons
dendrites
and convert these signals into action potentials that are transmitted toward the soma
dendrites
presence of arborized terminals
dendrites
spines on the surface
dendrites
cytoplasm lacks Golgi complex
dendrites
- conducts impulses away from the soma to the axon terminals
AXONS
- up to 100 cm length
AXONS
- originates at the axon hillock
AXONS
- with axon collateral
AXONS
- axoplasm with SER, RER, mitochondria
AXONS
- Initial segments for site if various excitatory and inhibitory stimuli
AXONS
- terminates into axon terminals
AXONS
- membrane is called axolemma
AXONS
- many dendrites and one axon
ex. neurons in the CNS
- Multipolar neuron
- one axon and one dendrite
ex. neurons in the retina of the eye and neurons in the nasal cavity
- Bipolar neuron
- one process extending from the cell body that divides into an
axon and dendrite
ex. Spinal and cranial ganglia
- Unipolar neurons (pseudounipolar)
> 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
Are the largest of the neuroglial cells
astrocytes
“perivascular feet” that surround blood vessels and pia matter
astrocytes
glial cell
Supply energy for metabolism
astrocytes
Forms a protective sealed barrier between the pia mater and the nervous tissue of the brain and spinal cord
astrocytes
Scavenge ions or debris from neuronal activity
astrocytes
glial cell
Structural support
astrocytes
Form scar tissues after injury to CNS
(e.g cerebral infarct)
astrocytes
Two types of Astrocytes
gray matter
branched processes envelop blood vessels, neurons and synaptic areas
Blood-brain barrier
With GFAP
Protoplasmic
Two types of Astrocytes
white matter
Long slender processes
fibrous
protects the CNS from fluctuating levels of electrolytes,hormones, and tissue metabolites
circulating in the blood vessels
The blood–brain barrier
Live symbiotically with neurons in the CNS
Located both in gray and white matter
Oligodendrocytes
Produces myelin that insulates and protects axons
Oligodendrocytes
increases the speed of transmission of the action potential down the axon.
Myelin sheath:
decreases the metabolic needs of the neuron by reducing the total amount of ion exchange that happens during an action potential.
Myelin sheath:
Flat cells, few mitochondria and GA
From neural crest cells
Schwann Cells
For regeneration of nerve fiber
Schwann Cells
Protect and insulate neuron in PNS
Schwann Cells
- phagocytic
- remove bacteria and cell debris from the CNS
- distributed in GM and WM
- secrete cytokines
- Microglia
line the neural tube and ventricles of the brain and spinal cord
Ependymal cells
transport and circulation of the CSF
Ependymal cells
no basal lamina
Ependymal cells
low columnar/cuboidal GLIAL CELL
Ependymal cells
Contribute to formation of choroid plexus
Ependymal cells
Functional apposition where signals are transmitted from one neuron to another or from neuron to other type of cell (e.g. muscle)
synapse
- enclosed by myelin sheath
- prevents loss of nerve impulse
- circular constrictions (Nodes of Ranvier)
- internodal segments or Schwann segments
Myelinated nerve fibers
- naked axons
- devoid of myelin sheath
- neurolemma
Unmyelinated nerve fibers
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
Are encapsulated aggregations of neuronal cell bodies (soma) outside the CNS
GANGLIA
Two types of ganglia
Autonomic ganglia
Craniospinal ganglia
mostly myelinated nerve fibers, some unmyellinated and glial cells
White matter –
– mostly neuronal cell bodies, unmyelinated
fibers, and neuroglial cells
Gray matter
Degeneration of distal axonal segment
(anterograde changes)
“Wallerian degeneration”
- Regeneration of proximal axonal segment
(retrograde changes)
