Neurons Flashcards
what type of charge do neurons carry?
relatively negative = -70mV
this is due to negatively charged protein cells and some Cl- ions
What determines the electrical potential of a membrane
the movement of ions through the semi-permeable membranes
distribution of ions
define non-gated channels
passively allow ions to cross
types of gated-channels
what opens them
examples of each
Modality-gated - open in response to mechanical forces, temp, or chemicals
Ligand-gated - respond to NT’s; ex: NMJ
voltage-gated - respond to changes in electrical potential; ex: axon membrane
axonal transport (orthograde axonal transport)
moves organelles and macromoleules (enzymes, protens) from cell body to axon terminals –> transported via microtubules
anterograde axonal transport
types & what each carries
transport from the cell body to the terminal
Fast = moves macromolecules containing vesicles and mitochondria
Slow = carries structural and metabolic components
retrograde axonal transport
transport from the terminal to the cell body
molecules like growth factors are transported back to the cell or recycled
pathogenically: rabies and tetanus are retrogradely transported
pseudounipolar neurons
what’s the peripheral process do? central process?
what are their anatomical classifications?
found only in sensory ganglia of spinal nerves & somatosensory ganglia of cranial nerves
- peripheral process = conveys sensory info from somatic or visceral structures (goes with peripheral nerves)
- central process = courses with nerve root to convey sensory info into CNS (dorsal root ganglion)
- –they function together as a single axon - even though one is working as an axon and one as a dendrite
multipolar neurons
neurons with a single axon and multiple dendritic processes
-most nerve cells are this
bipolar neurons
round/oval perikaryon with singe process - usually axon + dendrite
found in special senses; i.e. retina, vestibular & cochlear ganglia (CN VIII), olfactory system
unipolar neurons
single process, not common in humans
are afferent and efferent synopsis for sensory/motor?
NO. afferent = towards; efferent = away.
general terms for these fibers
where are interneurons located
all of interneuron must be in the CNS –> usually refers to the interneurons in the gray matter of the spinal cord
define monosynaptic reflex arc
two neurons and one synapse
ex: muscle stretch reflex
define resting potential
what do the ions do at this time
-relative concentration of each
when a neuron is not transmitting information & the inside is relatively more negative than the outside
K+ can easily diffuse in/out but Cl- & Na+ have trouble getting in –> more K+ in & more Na+ out
define local potential
the initial change in membrane potential due to some stimulus –> only spreads a short distance
may or may not cause action potential
1. variable amplitude, 2. localized 3. travel short distances
3 types of local (graded) potentials
- synaptic potentials = potential changes in neurons
- generator potentials (receptor potentials)= local potentials in sensory cells
- end-plate potentials = synaptic potentials of muscle cells
what is the threshold for an action potential
-55mV
define the all or none principle
all action potentials are the same size = it either reaches it’s threshold and depolarizes or it doesn’t
three events of an AP
- rapid depolarization by Na+ in
- decrease in Na+ as the channels close
- Rapid repolarization by K+ influx –> hyperpolarization = refractory period
2 ways to increase AP speed
- increase the diameter of the axon
- Mylein sheath –> myleinated internodes & unmyleinated nodes of Ranvier create saltatory conduction –> AP “jumps” from node to node
What is peripheral neuropathy?
any pathologic change involving peripheral nerves –> usually involves disruption of the nerves’ mylein sheaths
Guillain Barre Syndrome
PNS neuropathy; autoimmune disorder
acute inflammation and demyelination of PNA sensory & motor fibers caused by antibodies attacking the Schwann cells
–> decreased sensation & skeletal muscle paralysis
Multiple Sclerosis
autoimmune disease
antibodies attack the oligodendrocytes of the CNS = patches of demylienation = “plaques” in the white matter
muscle weakness, lack of coordination, impaired vision, impaired sensation, slurred speech
Why are nerve conduction studies administered?
to determine if the nerve transmission is slower than normal
What is a compound action potential
2 types
a measure of the combined electrical potential of a group of axons in a singe nerve
compound motor action potential = CMAP
compound sensory nerve action potential (SNAP)
what are neuroglia (glia) cells?
functions?
types?
non-neural cells in CNS & PNA that support neurons by controlling the environment within in the CNS
-shuttle nutrition from blood to neurons, remove waste products, maintain electrochemical surroundings.
-Mitotic - esp. during trauma/disease
CNS: astrocytes, oligodendrocytes, microglia, ependymal cells
PNS: schwann cells, satellite cells
what is the metabolic center of a neuron
the cell body - contains mitochondria, nuclues, nucleolus, nissl substance
define astrocytes
types
what are their function
type of glia cell found in PNS & CNS
protoplasmic = gray matter
fibrous = white matter
they cover the cells capillaries along with cell body, axons, dendrites & synapses where they play a role in metabolism of NT’s like GABA
what are Nissl bodies
large amounts of rough ER in the cell body of a neuron - there because a neuron creates a lot of protein
what is chromatolysis
what does it indicate
loss of color of the nissil bodies due to damage of the neuron – usually indicates potential neuron death
what is a neurophil / where is it located
=dendrite and synapses located in the gray matter of the Nervous System
what form do cell bodies take in the the CNS? (2); in the PNS?
laminae = sheets/layers OR ganglia in CNS
ganglia only in PNS
what direction do dendrites conduct
towards the cell body
what direction do axons conduct?
away from the cell body
define axon collaterals
define axon hillock
branches off of axons
location in which axons arise
define arborizing
axons branching into fine terminal branches
alternate names for white matter in the CNS
tract, fascicle, lemniscus, bundle
what gets myleinated
large diameter axons
job of microfilaments in the neuron
important in anchoring receptor molecule at synapses and for movement of the advancing tip of growing axons
tau’s role in neurofibillary tangesq
it’s dissociation from the microtubule forming filaments is what causes the cells to tangle
astrocytes in injury
they proliferate & enlarge (as reactive astrocytes) & form glial scars via gliosis
they are responsible for why the CNS has poor regenerative abilities
They also fill the demyelinated spaces in the CNS during MS = MS plaques
what are microglial cells
immune effector cells of the CNS - involved in inflammation
act as macrophages
what are ependymal cells
cells that form the choroid plexus epithelium
=secretes CSF
Most common brain tumors of CNS in order.
of PNS?
- glioblastoma = multiple glia cells
- astrocytomas = astrocytes
- Oligodendrogliomas
- ependymomas = from the ependymal cells (rare)
PNS = vestibular schwannoma
