L5 Neural Tissues Flashcards
What is the difference between the central nervous system and the peripheral nervous system?
•CNS is the brain & spinal cord; PNS is all else. CNS is associated with Cerebrospinal fluid. CNS has a different cohort of glial cells (egoligodendrocytes vs Schwann cells)
Which embryonic layer/tissue is the nervous system derived from?
•Ectoderm (or neuroectoderm)
What are the main functions of neuroglia?
- Protect, nourish, support
- Make myelin (and increase conduction velocity)
- Regulate fluid and ion transport across membranes
What is a Node of Ranvier?
- On an axon, this is a segment of an axon that is not covered with myelin, but is bare and facing the extracellular fluid
- It is an excitable part of the axon (whereas membrane under myelin is not excitable)
–Na+ channels are clustered at nodes
•This is where action potentials occur, and it is fundamental in saltatory conduction
What is myelin?
- Myelin is a protective substance surrounding axons that is made up of successive layers of plasma membrane. As such, it is mostly lipid bilayers.
- It works as an electrical insulator
- It increases transmembrane resistance and decreases transmembrane capacitance
What is the purpose of myelin?
- By reducing transmembrance conductance, myelin can lead to saltatory conduction
- Thus myelin increases conduction velocity.
- This means axons can have a thinner diameter and retain their conduction velocity
What histological and physiological traits distinguish a neuron?
- Neurites (outgrowths)
- Excitability (can have action potentials)
- Many neurons have quite large cell bodies
What histological traits distinguish an astrocyte?
•Many processes
–Star shaped
•Its feet abut blood vessels
What histological traits distinguish a microglial cell?
- Small compared to other glia
- Spindly processes
What histological traits distinguish an ependymal cell?
- Adjacent to a Site of CSF
- Organised as an epithelial layer
–I.e. highly cellular
–cilia
What histological traits distinguish an oligodendrocyte?
•Can surround multiple axons
What histological traits distinguish a Schwann cell?
- Wrapped around an axon
- Only around a single axon
- Peripheral nervous system only
What histological traits distinguish
a satellite cell in the peripheral nervous system?
- Small and round
- Located as a group around a neuron’s large soma
- Often shown in Dorsal Root ganglia
What is the function of a neuron?
- It communicates information quickly (allowing organism to respond to the environment)
- It does this by firing axon potentials
- In networks, it integrates information
What is the function of an astrocyte?
- Support of nervous tissue
- Contributes to blood vessel control in CNS
–Perfusion, possibly permeability
- May be involved in the blood brain barrier
- Repair of nervous tissue after trauma
What is the function of a microglial cell?
•Immune defense in the CNS
–Protect nervous tissue
–CNS is immune-privileged due to blood brain barrier
–Antibodies from rest of body are not in CNS
–CNS cannot tolerate inflammation
What is the function of an ependymal cell?
•Forms CSF
–Controls fluid and ion transport
•Forms the epithelium that lines ventricular system
What is the function of an oligodendrocyte?
•Forms myelin in CNS
–Increase conduction velocity
–Insulates axons
–Increases transmembrane resistance & decreases capacitance
What is the function of a Schwann cell?
•Makes myelin in the peripheral nervous system
–Increases conduction velocity
–Insulates axons
–Increases transmembrane resistance & decreases capacitance
What is the function of a satellite cell in the peripheral nervous system?
•In PNS, these support neurons
–Control microenvironment
–Similar roles to astrocytes
•Protect and cushion neurons
Name a cell type or place where you would find a multipolar neuron.
- Many possible answers, including
- Cerebral cortex –Pyramidal cells
- Cerebellar cortex–Purkinje neurons
Name a cell type or place where you would find a bipolar neuron.
- Many possible answers, including
- Retina
–Bipolar cells
•ganglia of the vestibulocochlear nerve
–Bipolar cells
Name a cell type or place where you would find a pseudounipolarneuron.
- Best example is dorsal root ganglia
- Also in semilunar ganglia of trigeminal nerve
Name a place where you would find afferent neurons.
- Many examples including sensory neurons from
- Special senses (retinal ganglia, cochlea, etc)
- Sensory neurons (and pain receptors) from skin
- Proprioceptors from muscles
Name a place where you would find efferent neurons
- Many examples including motor outputs from brain
- Motor cortex
- Ventral horn of spinal cord
What kind of axon fibres have the fastest conduction velocity?
- Neurons that are myelinated
- Neurons that have a large cross-sectional area
- E.g. Alpha motor neurons
Name 4 ways in which glia (in general) differ from neurons (in general).
- Neurons have action potentials, glia do not *E
- Glia do not form synapses
- Glia are able to divide, neurons cannot *E
- Glia form myelin sheaths
- Neurons are usually bigger *E
- There are many more glial cells than neurons
Name 4 differences between a glioma and a neuroblastoma.
- Glioma typically affects older individuals, neuroblastoma typically affects babies and very young individuals
- Glioma is usually inside cranium, neuroblastoma is usually outside cranium
- Glioma often has a poor outcome (malignant), neuroblastoma often has a good outcome
- Neuroblastoma often secrete catecholamines, leading to high blood catecholamines
Name two differences between an oligodendrocyte and a Schwann cell.
- Oligodendrocyte is in CNS
- Oligodendrocyte typically myelinates many neurons
What kind of neurons (histologically) would you expect to find in the dorsal root ganglia?
•Pseudounipolar
Name two locations where you would expect to find ganglia in the peripheral nervous system.
- Enteric nervous system –Auerbach’s and Meissner’s
- Parasympathetic ganglia in glands
- Sympathetic chain ganglia
Approximately how many neurons are in the brain?
- 1011
- 100 (American) billion
What is a Brodmann area
•A region of nervous tissue on the cerebral cortex
–E.g. the primary visual cortex (V1) of the occipital cortex is Brodmann area 17
–E.g. the motor cortex is Brodmann area 4
•Each region is defined by its structure or organisation of cells
Which part of the prefrontal cortex is nearest to the primary auditory cortex (on the outer shell of the temporal lobe): ventrolateral, ventromedial, dorsolateral, dorsomedial?
•Ventrolateral prefrontal cortex is closest to the auditory cortex of the temporal lobe
