1. Neurocytology Flashcards
General Organization of the Nervous System Anatomically: • Central – CNS: – \_\_\_\_. – Spinal cord. – Neural parts of the \_\_\_\_.
• Peripheral – PNS:
– ____ nerves.
– ____.
– ____.
brain eye peripheral nerves ganglia nerve endings
Function of Nervous System • Peripheral – PNS – Receive information: sensory - \_\_\_\_. – Transmit response to effector organ: motor – \_\_\_\_.
• Central – CNS
– Integration
– Analysis
– Response
afferent
efferent
General Organization of the Nervous System Cell components • CNS: - Neurons - Glia --- \_\_\_\_ --- Oligodendrocytes --- \_\_\_\_
• PNS:
– Neurons
– ____ Cells.
– ____ Cells.
• Only common cell type: ____
astrocytes microglia satellite schwann neurons
Cell types: Neuron
• Highly specialized, excitable. • Structure: – \_\_\_\_: • Nucleus and most organelles. – Dendrites: • Tree-like processes: dendritic tree. – Axon: • \_\_\_\_ process. • Originates at the \_\_\_\_. • Ends in the \_\_\_\_. • Telodendron endings: \_\_\_\_.
• In response to NT, cell responds by changing the cxn of ions, resulting in a change of currents ◦ Can respond in a specific way • \_\_\_\_ terminals of telodendron ◦ Synaptic terminals • 3 divisions are related to the three regions: ◦ Dendrites/soma = \_\_\_\_ region ◦ Axon = \_\_\_\_ region ‣ Transmits the AP ◦ Synaptic terminal = \_\_\_\_ region ‣ Releases a NT
soma single axon hillock telodendron synaptic terminals
cytoplasmic
receptor
conductive
effector
The Neuron: Soma
• Soma:
– Nucleus (with prominent
____) + cytoplasm (a.k.a. ____ [“around the nucleus”]).
– Abundant ribosomes: often associated with the ER → ____ or ____ substance.
– Prominent Golgi apparatus.
– Abundant mitochondria.
• \_\_\_\_ active neurons • Soma contains all components of secretory pathways • ER is easily stainable and visible ◦ \_\_\_\_ stain in many neurons
nucleolus perikaryon Nissl bodies Nissl's substance metabolically granulated
The Neuron: Dendrites
• Dendrites: – \_\_\_\_ (“tree-like”). – Primary receiving site for synaptic information. – Surface may show dendritic spines: increase \_\_\_\_.
arborescent
surface area
The Neuron: Axon
• Axon: – Starts at the \_\_\_\_. – Initial segment: proximal region of the axon where \_\_\_\_ start. – Diameter usually remains \_\_\_\_. – May be myelinated: myelin sheath from initial segment to telodendron. – May have \_\_\_\_ branches.
• Axon hillock = area where AP begins ◦ Cxn of \_\_\_\_ is different here from the rest of the axon • Aren't always myelinated • Only the \_\_\_\_ are myelinated (not soma or dendrites)
axon hillock
AP
constant
collateral
ion channels
axons
Types of Neurons
• Based on the number of ____ emerging from the soma:
– ____ neurons:
• Two processes.
– ____ neurons:
• One short process that divides into two branches.
– ____ neurons:
• Many processes.
• Single axon.
• More than one dendrite.
processes
bipolar
pseudounipolar
multipolar
Types of Neurons
• Bipolar neuron: • Two processes. • \_\_\_\_ axon emerges from either side of the soma. •Common in \_\_\_\_ structures: – \_\_\_\_ – Olfactory epithelium – \_\_\_\_ and \_\_\_\_systems
• Either side is similar \_\_\_\_ • Place where input and output is produced is not \_\_\_\_ ◦ Bottom: effector; but upper process would then be the sensory part
single sensory retina vestibular auditory visually equivalent
Types of Neurons
• Pseudounipolar neuron:
• Single axon divides a ____ distance from the
soma.
• Axon branches:
– ____: information from the periphery.
– ____: ends in the spinal cord or brainstem.
• ____ of cranial and spinal nerves.
- Good at transmitting information ____
- One branch: transmits information from ____; would induce a response in the other end of branch which would reside in ____
- Transmits information without any form of ____
short peripheral central sensory ganglia quickly PNS CNS integration
Types of Neurons
• Multipolar neurons:
– Many ____.
– ____ axon.
– Examples:
• ____ cell of the cerebral cortex.
• ____ cell of the cerebellar cortex.
dendrites
single
pyramidal
purkinje
Synaptic Terminals and Synapses
• Synapse:
– Junction between the ____ terminal
of an axon and the ____ membrane receptor surface (a dendrite or a muscle cell).
• Synaptic terminal:
– Specialized neuronal structure for the
transmission of a ____ (neurotransmitter) in response to an action
potential.
• Postsynaptic membrane does not have to belong to another ____
presynaptic
postsynaptic
chemical message
neuron
Classification of Synapses
• Based on their location on the \_\_\_\_ neuron: – \_\_\_\_ synapse: • Axon terminal ending on the soma of a neuron. – \_\_\_\_ synapse: • Axon terminal ending on another axon terminal. – \_\_\_\_ synapse: • Axon terminal ending on a dendrite. – \_\_\_\_ synapse: • Axon terminal facing a dendritic spine
• Axoaxonic are common
◦ Postsynaptic controlled in activity by controlling the releaser of NT
◦ Typical of neurons that are ____ on the PSN
• Axodendritic are the most ____ contact
postsynaptic axosomatic axoaxonic axodendritic axospinous
inhibitory
“traditional”
Designation of groups of neurons and axons
PNS: – \_\_\_\_: Cluster of neurons. • Sensory • Motor – Nerves, rami (sing. ramus), or roots: Axons derived from a ganglion.
• CNS:
– ____: Aggregate of functionally and structurally related neurons.
– ____: Clusters of neurons arranged in a layer.
– ____ (cerebral cortex): Clusters of neurons arranged in longitudinal groups.
– ____, fasciculus, or ____: Bundles of axons.
– ____: darker tissue of the brain and spinal cord, consisting mainly of nerve cell bodies and
branching dendrites.
– ____: lighter tissue of the brain and spinal cord, made of axons connecting different parts
of grey matter to each other.
ganglia nucleus stratum lamina tract lemniscus gray matter white matter
Support Cells
PNS
• ____ cells
• ____ cells (ganglion glia)
CNS (Glial Cells) • Oligodendrocytes – \_\_\_\_ - gray matter – \_\_\_\_ - white matter • Astrocytes – \_\_\_\_ - white matter – \_\_\_\_- grey matter • Microglia – macrophages
schwann
satellite
perineuronal
interfascicular
fibrous
protoplasmic
Schwann Cells and Myelination
• Derive from the \_\_\_\_. • Cover most of the surface of all axons in \_\_\_\_ nerves. • Envelop axons in a sheath of myelin: facilitates transmission of action potentials. • One axon: myelin sheaths from \_\_\_\_ Schwann cells • \_\_\_\_: – Segments of axons covered with myelin. • Nodes of Ranvier: – Gaps without \_\_\_\_ between internodes – Function: nerve signal boost; \_\_\_\_.
- Similar embryological origin to ____ (derive from neural crest)
- Some of the axon will be covered by the ____ itself, and the myelin sheath
- Need many Schwann cells to cover an axon in myelin
neural crest peripheral multiple internodes myelin saltatory conduction
neural crest
schwann cell
Development of the Myelin Sheath
- During ____, the axon is close to a schwann cell
- After Schwann cell precursor attaches, it begins to ____ around
development
wrap
Development of the Myelin Sheath
____ movement
• Wrapping creates consecutive ____
◦ Embed ____ of Schwann cell
clockwise
layers
cytoplasm
