Lecture 9 -Nervous Flashcards
2 core divisions of the nervous system
Central nervous system and the peripheral nervous system
what makes up the central nervous system and what is it derived from?
brain and spinal cord. derived from the neural tube
what makes up the peripheral nervous system and what is it derived from?
all nervous tissues outside of the CNS. Derived from neural crest cells
What are the 3 primary functions of nerve cells?
Irritability (speed of response), conductivity (transmit a response), and secretion (neurotransmitters)
Glial cells
support and protect neurons. Formed from monocytes.
Afferent system
receive and transmit information from the environment to the CNS
Efferent system
Transmits info from the CNS to the periphery (exiting from the CNS)
3 main types of neurons
bipolar, multipolar, and pseudounipolar
Most common type of neuron
multipolar
Bipolar
two dendrites, found in retina, cochlear, and olfactory
Multipolar
Lots of dendrites. Most commonly found
Pseudounipolar
Cell body is down the axon terminal. Found in long neurons, such as the dorsal root ganglia.
Afferent neurons primarily are what type of neuron?
Pseudounipolar
Somatic vs autonomic
somatic: voluntary muscles
autonomic: involuntary smooth muscles (both parasympathetic and sympathetic)
Interneurons
coordinate all neural activities and consist of mostly multipolar neurons.
Myelinated neurons in PNS
myelin sheath formed by schwann’s cells (roll themselves around the axons).
Myelinated neurons in CNS
myelination formed by glial cells or oliogodenrocytes
Non-myelinated neurons
Also have schwann cells present but do not roll around axons. Primarily used for support
Cholinergic neurotransmitter
acetylcholine. Most efferent nerves
Adrenergic neurotransmitter
norepinephrine. Postganglionic sympathetic neurons
Perikaryon
cell body around the nucleus
Dendrite
short processes that receive the stimuli. Lack golgi.
Synapse
connection of the dendrite
Collateral branch
when some of the axons get branched. Have terminals which make the connection with the next cell
Nissil bodies
regions of RER in cell body and dendrite . basophilic stain.
Axons contain what type of filaments?
Microtubules. Which allow for transport of proteins and other cellular contents
Lipofuscin
residual bodies left over from lysosomal digestion
Main cytoskeleton support in perikaryon?
Neurofilaments
Axon hillock
area where the coordination preparation occurs for the action. No nissil bodies. initial site of microtubule bundling
Initial segment of axon
nonmyelinated. site of neuron where stimulus is integrated. Lots of mitochondria
axoplasm
cytoplasm material in the axon. Allows for electric current to pass through it. Thus low protein content and high ion content
Anterograde protein vs Retrograde protein
Anterograde - kinesin
Retrograde - dynein (REaDY)
Anterograde transport
Kinesin. slow stream: axon growth (1-4 mm/day)
fast stream: neurotransmitter transmission (50-400 mm/day)
Retrograde transport
Dynein. Intermediate stream: salvage pathway (10-100 mm/day)
Transports cytoskeletal components
3 types of synapses
chemical, electrical, and mixed
Chemical synapse
secreted neurotransmitters binding to the receptors with a certain space in between the membranes. Arrival of nerve impuse cuases an influx of Ca into the axon terminal, which causes an exocytosis of transmitter.
Electrical synapse
much smaller space between the membranes (gap junction) via connexins.
Adrenaline secreted into cleft
sympathetic
Acetylcholine secreted into cleft
parasympathetic
4 types of synapses
axon-dendritic
axo-somatic
dendro-dendritic
axo-axonic
presynaptic cells will contain lots of what?
vesicles
Sodium potassium pump
3 sodium out, 2 potassium in (3N, 2K). More positive outside of cell and more negative inside the cell. ATP dependent.
Ion channels different types
resting channel, voltage gated channel, ligand gated channel, and signal gated channel
Resting channel
always open
Voltage gated channel
opens in response to electrical change in the membrane potential
Ligand gated channel
opens in response to a specific extracellular signal
signal gated channel
opens or closes in response to a specific intracellular signal
Resting potential
more K leak channels are open compared to Na channels. -70 mV (small K oustide and large Na concentration). Pumping 3 Na out and 2 K in, will continue the gradient.
Action potential
maximum value of +30mV (thus a 100mV difference). Occurs from depolarization as sodium enters into the cell.
Repolarization
potassium leaves the cell and will overshoot, causing a hyperpolarization. Sodium channels are inactivated
Depolarization
sodium enters into the cell through open channels
Nodes of Ranvier
space between cells that are left unmyelinated. Where sodium channels are exposed and thus allow for the start of an action potential. (saltatory conduction)
Purpose of myelination
to insulate the action potential from electrical changes that occur outside the cell.
3 key players in CNS
cerebrum, cerebellum, and the spinal cord
Cerebrum
controls thinking and speaking. largest portion
Cerebral cortex
outside layer of the cerebrum, composed of primarily gray matter
Basal ganlia
base of cerebrum. controls and synchronizes movements.
Amygdala
memory and emotional behavior
Hippocampus
transfer short term memory into long term memory
Cerebellum
occipital region of the brain. Coordination of movement, motions, reflexes, and balance
Midbrain
between the cerebrum and cerebellum. Involved in hearing and sight reflexes
brain stem
consists of the midbrain, medulla, and pons
Pons
in the brain stem. responsible for REM sleep
Medulla
at the base of the brain. regulates heart rate, breathing, and digestion
Gray matter of spinal cord
non myelinated neurons. Cell bodies, perikaryons and glial cells. H in the spinal cord.
white matter of spinal cord
primarily glial cells and nerve fibers, no neuron cell types. contains myelinated neurons (tracts).
Cortical gray matter
Neurons and glial cells (outside of the brain) and nerve fibers
Medullary white matter
nerve fibers and glial cells (inside of the brain)
2 layers of cerebrum
superficial layer and pyramidal layer
Superficial layer
comprised of a few cells, mostly axons
Pyramidal layer
axons can reach deep into cortical layers or white matter. some extend into spinal motor neurons.
Cerebellum’s grey matter
composed of cell bodies and nerve fibers. found on the outside.
3 layers of cerebellum’s grey matter
Molecular layer: unmyelinated fibers, few perikaryons
GL/Purkinje cell layer: large cells’ dendrites penetrate ML
GrL/Inner granular layer: Packed with small multipolar neurons
4 types of glial cells
oligodendrocytes, astrocytes, microglia, and ependymal cells
Oligodendrocytes
similar to schwann cells, can roll around the axons in the CNS. Can wrap around multiple axons. Myelination is not complete at birth, but takes place during development. Slow cell division.
Astrocytes
found between tracts of axons and dendrites. Provide protection and contribute to the removal of some of the residues. Take up K+
Microglia
have lots of processes, could be stimulated to have an immune response upon injury
Ependymal cells
lining certain components of the CNS and secrete the CSF (mostly pseudostratified columnar epithelia) Cilia keep the CSF moving.
Function of glial cells
sustain neurons physically, metabolically, and help regulate ionic concentrations in the extracellular space.
Fibrous astrocytes
always only in the white matter
Protoplasmic astrocytes
only in the gray matter. Fewer filaments and processes.
3 parts of Meninges and the overall function
Dura mater, arachnoid, and Pia mater. Provide cushioning for the skull
Dura mater
very dense CT, connected to periosteum of cranial bones by loose CT. Well vascularized
Arachnoid membranes
Middle layer that makes up trabeculae. filled with CSF and loosely conforms to brain folds.
Pia mater
Inner most layer. Collagen fibers covered with squamous epithelial cells. Follow the blood vessels
Blood-brain barrier
limit access of lipid soluble material from blood to brain and spinal chord.
CSF
extra layer of protection for the brain. If too dense (hydrocephalus) the brain could swell.
Dorsal Root Ganglia
afferent neuron collection. located in the posterior. primarily pseudounipolar.
Autonomic ganglia
collections of efferent neurons. Contain multipolar neurons.
3 layers of CT coverings
Epineurium, perineurium, endoneurium
Epineurium
outer most cover
Perineurium
directly covers bundles of nerves
Endoneurium
vascularized loose CT between individual fibers
Chromatolysis
nissil bodies dissolve and begin regeneration of damaged cells. First step in regeneration
Steps of regeneration of nerve fibers
Perikaryon changes, schwann cells start proliferation, perikaryon returns to normality, nerve fiber penetrates schwann cell column
Parasympathetic branches from what area of spinal cord
thoracic and lumbar
Sympathetic branches from what area of spinal cord
sacral and cranial
Paravertebral ganglia
located outside spinal column antero-laterally extending from cervial to sacral regions. primarily sympathetic preganglionic axonal endings and postganglionic cell bodies
prevertebral ganglia
in abdomen. Meeting of preganglion sympathetic axons and postganglionic neurons
Terminal ganglia
located near the organs to be innervated. mostly parasympathetic axonal endings and postganglionic cell bodies
