NERVOUS TISSUE (Lecture 7) Flashcards
main function of nervous tissue
COMMUNICATION
coordinates body function w/ the internal and external env.
sensory input =
afferent = info brought from the periphery to the CNS
external stimuli: touch, pain, temp, muscle tension
motor output =
efferent = info LEAVING the CNS to the periphery
ex: skeletal muscle - voluntary movement like locomotion, chewing, refle
CNS is made up of the _____ and ______
Brain and Spinal cord
The Peripheral NS is made of the _____ + ______
cranial nerves + spinal nerves
Is there any connective tissue in the CNS?
NOOO
the 2 fundamental cells in the nervous tissue
Neurons (functional)
Glial cells (support)
what is included in Neuropil
synaptically dense regions composed of UNmyelinated axons, dendrites, and processes of glial cells
primary function of neurons
generate & propogate action potentials
functions of Dendrites
- receive info from other neurons
- have dendritic spines that increase the SA
dendrites have the same organelles as a cell body MINUS A NUCLEUS
what is unique about dendrite membrane receptors
they can change the potential of the cell membrane
what is contained within a Nissl body?
rough endoplasmic reticulum and free ribosomes
what kind of DNA is found within a neuron cell body
Euchromatin
contents of a neuron cell body
- nucleus
- nucleolus
- nissl bodies
- golgi complexes
- mitochondra
- neuro filaments
- microtubules
what are neurofilaments?
intermediate filaments that provide structural support to the cell
considered a cytoskeletal structure
function of the axons
transport impulses from the cell body
function of dendrites
receive external impulses and tranport them towards cell body
what does it mean that axonal transport is Bidirectional ?
synaptic vesicles can undergo anterograde or retrograde transport
what is axonal transport
aka exoplasmic tranport
axonal transport is the movement mechanism of mitochondra, lipids, synaptic vesicles to & from the cell body and axon
which type of axonal transport is fast
anterograde or retrograde
retrograde
transport TOWARD cell body when cell membranes are being returned to the cell body for reuse or degradation
synapses are connections between ________ used for communcation
between NEURONS
what initiates neurotransmitter release
action potential !
the narrow gap that separates neurons
synaptic cleft
synaptic vesicles contain ______?
Neurotransmitters
what releases ACh from a motornueron and then propogates an action potential w/in the muscle fiber
the Neuromuscular synapse
most common type of neuron
multipolar neuron
where are pseudounipolar neurons found?
sensory ganglia
spinal nerve sensory ganglia and some cranial nerves
what are ganglia?
clusters of cell bodies
What are Glia cells?
Non-neuronal cells of the NS
- interstitial, supportive cells for neurons within the NS
Astrocytes, migroglia, schwann cells (PNS), oligodendrocytes (CNS)
what are the primary immune defense cells of the CNS
microglia
10-15% of glia
function of microglia?
- can become phagocytic and antigen-presenting
- remove damaged neurons and infectious agents
astrocytes have ‘feet’ that help them support what 2 things?
- BBB
- Glia limitans (barrier b/w pia matter and CNS)
where are Schwann cells found
PNS
Where are oligodendrocytes found
CNS
purpose of Schwann cells
- myelinate PNS axons
can only myelinate a single internodal segment per axon
purpose of oligodendrocytes
compose the myelin of the CNS
can myelinate more than one axon and more than one internodal segment per axon
purpose of myelination
improves conductivity of axons, speeds things up
myelination electrically insulate axons to increase conduction
where on an axon is myelin NOT found
initial segment and axon terminal
name for regions where myelin is present
myelin present = insulated
internodal segments
spaces b/w internodal segments
where axon is exposed
nodes of ranvier
what is it called when an action potential ‘jumps’ from node to node
Salatory conduction
myelin is a _____ rich structure
phospholipid
what is the myelin sheath formed from
compressed layers of glial cell plasma membrane
myelin sheaths
________ envelops the myelin sheaths of individual axons of peripheral nerves
endoneurium
- composed of reticular fibers
- produced by schwann cells
______ surrounds each bundle of nerve fibers (fascicle) of peripheral nerves
perineurium
______ is a fibrous coating around an entire peripheral nerve, also fills the space b/w nerve fibers
Epineurium
what are the 3 CT of peripheral nerves?
endoneurium, perineurium, epineurium
explain why an ‘unmyelinated axon’ isn’t truly without schwann cells
these axons are smaller in diameter so they have slower conduction BUT they are still enveloped by glial cells
**enveloped not Wrapped is main difference
