Neural Tissue Flashcards
Structural Organization of Nervous System
- CNS: consists of the brain enclosed in the cranium & the spinal cord enclosed in the vertebral column
- PNS: consists of cranial nerves that extend from the brain & brainstem & spinal nerves that extend from the spinal cord
What does the Nervous System do?
Input (sensory nervous system)
Integration (CNS processes sensory input and determines response)
Output (Motor nervous system)
Somatic Nervous System
voluntary; includes processes that are perceived or consciously controlled
somatic sensory (input): conscious & subconscious sensation from skin, muscle, joints, & skin via sensory neurons
somatic motor (output): voluntary & reflexive (involuntary) control fo skeletal muscle via somatic motor neurons
Autonomic Nervous System
involuntary; functions to maintain homeostasis
visceral sensory (input): subconscious sensation from blood vessels & internal organs via sensory neurons
visceral motor (output): involuntary control of cardiac muscle, smooth muscle, & glands via visceral motor neurons
two anatomically & functionally distinct subdivisions: sympathetic NS and parasympathetic NS
Cells of Nervous System
Neurons
- communication cells
- excitable; recieve, generate& transmit impulses
- variety of shapes & sizes
- non-mitotic
Glial Cells
- supporting cells found around neurons
- fn: nourish & protect neurons, waste clearance, injury response
- non-excitable & mitotic
Neurons
- cell body
- dendrites
- axon
Structural Classification of Neurons
classified based upon number of processes extending directly from their cell body
Bipolar
Multipolar
Pseudounipolar
Functional Classification of Neurons
Classified based on direction of the action potentials
Sensory:
‘afferent’
impulses from sensory receptors to CNS
most are pseudounipolar
Interneurons:
only found in CNS
facilitate info between sensory & motor neurons
multipolar & most numerous
Motor Neurons:
‘efferent’
impulses from CNS to effectors
multipolar
Stains
Golgi - stains specific neurons
Nissl - only stains cell bodies
Myelin - stains myelin
Glial Cells in CNS
Microglia
Astrocytes
Ependymal cells
Oligodendrocytes
Astrocytes
most numerous & diverse; forms structural network
characterized by numerous cytoplasmic processes that contact BVs & neurons
Several FNs include:
replace damaged neurons -> glial scar
regulated tissue fluid composition
help regulate synaptic transmission
assists in neuronal development
helps form BBB
Oligodendrocytes
cytoplasmic processes form the myelin sheath in CNS; predominant glial cell in white matter
one oligodendrocyte can wrap around many axons
FN: increases rate of axonal conduction
Ependymal Cells
cuboidal-to-columnar clels that line ventricles of the brain & central canal of spinal cord
covered by cilia & microvilli
FN: assist in producing, monitoring, & circulating CSF
Microglia
Migrate through CNS to areas of inflammation & replicate
FN: secrete cytotoxic factors which can kill bacteria & phagocytize dead cells
Neurolemmocytes (Schwann Cells)
form myelin sheath around ONE axon in PNS; several are needed to myelinate an entire axon
evelope “unmyelinated” axons in PNS; a chain of neurolemmocytes are needed to enclose an entire axon
Myelination in PNS
Insulating covering wrapped an axon
consists mainly of plasma membrane of the neurolemmocytes
fn: improves conduction speed of an action potential
Satellite Cells
flattened cells that surround neuronal cell bodies in ganglia (collection of cell bodies in PNS)
FN: regulate cellular exchange between neurons & their environment
Gray Matter in CNS
neuronal cell bodies predominate; appears grey due to absence of myelin
fn: location where synaptic transmission occurs
White Matter in CNS
axons (tracts, columns, pathways), glia cell bodies, vessels; appears white due to myelination
fn: ascending tracts/columns carry sensory info & descending tracts/columns carry motor info
Gray Matter in PNS
neuronal cell bodies predominate in ganglia; appears grey due to absence of myelin
sensory ganglia contain cell bodies of pseudounipolar sensory neurons, both somatic & visceral
autonomic ganglia contain cell bodies of multipolar autonomic motor neurons
