Nervous Tissue Flashcards
Ganglia
Neuronal cell bodies in the PNS
Afferent
toward CNS- sensory
Efferent
away from CNS- Motor
NissI Bodies (chromatophilic bodies)
clusters of rought ER and free ribosomes
Neurofibrils
intermediate filament bundles, make a network between nissI bodies and preven cell from being pulled apart
neurofilaments
in axon. with action and mictorubles, provide structural strength. aids in axonal transport
Multipolar Nerves
more than 2 processes
~99% of all nerves
multiple dendrites, 1 axon
interneurons and motor neurons are multipolar
Bipolar nerves
2 processes that extend from opposite sides of the cell body
one process is a fused dendrite, the other is the axon.
rare
found in some special sensory organs: inner ear, olfactory epithelium, retina
Unipolar Nerves
one short single process near neuron cell body. It then divides into 2 long processes.
One long branch goes the to CNS (central process), the other one goes to periphery receptors (dendritic process)
Found in some sensory ganglia of the PNS.
Common in dorsal root ganglia of cranial nerves
Neuron Characteristics
longevity
no mitotic division
high metabolic rate
Neuroglial Cells- Astrocytes
CNS
most common.
Radiating processes with bulbous ends cling to neurons/capillaries.
extract blood sugar for energy
sense neurotransmitter release. Regulate neurotransmitter levels by increasing uptake in regions of high activity. They also signal to sincrease blood flow in these regions
-take up and release ions to influence ionic environment
-produce molecules neccessary for neural developement ex: brain derived trophic factor.
propagate Ca2+ signals that may be involved in memory
Neuroglial CellsEpendymal Cells
CNS
simple epithelium that lines the central cavity of the spinal cord and brain. Fairly permeable. Between cerebral spinal fluid and tissue fluid that baths the cells of the CNS.
Have cilia that help circulate CSF
Neuroglial Cells-Microglial cells
CNS
Defense.
-Smallest, least abundant
-elongated with many cell processes that have pointed projections
-phagocytes (dead neurons)
-support maturation of synaptic cleft
- do NOT originate from nervous tissue– derived from monocytes.
Neuroglial Cells- oligodendrocytes
CNS
Have fewer branches than astocytes. Wrap their cell processes around thicker axons. Produce MYELIN sheath. Multiple processes from one oligodendrocyte can myelinate multiple axons.
make nodes of ranvier
Neuroglial Cells- satelite cells
PNS
surround cell bodies
Neuroglial Cells- Schwann Cells
PNS
make myelin sheath in PNS axons by wrapping around them in concentric rings. This causes the cytoplasm to get pushed toward the outer layer– called the neurollema.
These develop during the fetal period and into the first year of life.
Thin PNS axons
unmyelinated. Schwann cells can be around the axon but they dont form concentric rings. Found in ANS and sensory fiber.
Nerves- Endoneurium
layer of delicate CT covering schwann cells
Nerves- nerve fasicles
groups of axons bound in bundles by CT wrapping (Perineurium)
Nerves- perineurium
CT wrapped around nerve fasicle
Nerves- epinerium
though fibourous sheath that surround the entire nerve.
Gray Matter
surround hollow central cavities. Where neuron cell BODIES cluster.
White Matter
no cell bodies. predominantly myelinated axons.
Tracts
bundles of axons passing between specific regions of the CNS. Most of these only go between brain and spinal cord.
Reflex Arcs
chain of neurons responsible for reflexes. Can be somatic (skeletal muscle) or visceral. Made up of 5 components:
- receptor
- sensory neuron
- integration center
- motor neuron
- effector
Reflex Arcs- receptor
at terminal end of sensory nerve. Site where stimulus acts
Reflex Arcs- Senesory Neuron
transmits afferent impulses to the CNS
Reflex Arcs- Integration Center
consists of one or more synapses in the gray matter of the CNS
Reflex Arcs- motor neuron
conducts efferent impluse form the integration center to an effector
Reflex Arcs- effector
muscle or gland cell that responds to the efferent impulses by contracting or secreting.
Monosynaptic Reflex
1 synapse- no interneuron
fast
reflexes that help maintain equilibrium and upright posture ex. knee jerk
Polysynaptic reflexes
more common
multiple interneurons
most simple ones have 1 interneuron
es. withdrawl reflex
Neruonal Circuits- diverging
diverts into multiple paths.
one pre synaptic neuron synapses with multiple neurons
ex. muscle stretch
Neruonal Circuits- Convergent
many synpases–> 1 postsynaptic neuron. may get both excitatory and inhibatory
Neruonal Circuits- Reverberating
one neuron recieves feedback from another in the same circuit. Ex. Breathing
Serial Processing
pass of a signal to a specific destination in sequence along a single pathway. ex: reflex arc
Parallel processing
simultaneously, nerve impulses travel in an axon branch that extends into the spinal white matter and extends as an ascending pathway to the brain. A single stimulus–> multiple perceptions. Ex: withdrawal reflex– pain triggers sensory neuron with initiates spinal withdrawal reflex
