Cells of the nervous system Flashcards
newly discovered layer in the meninges
The SLYM
The SLYM
Subarachnoid Lympatic-like membrane, very thin layer, helps control follow of CSF and contains immune cells to fight infections
The blood barrier
Allows only certain substance to reach the brain, formed of tightly packed endothelial cells that line blood vessels and capillaries as well as the “feet” of astrocytes that surround capillaries, keep out pathogens, toxins, it allows oxygen , glucose, and a selection of other necessary compounds and proteins to pass through, psychoactive drugs must be able to cross the BBB
What is the nervous system made o
Glial cells and neurons
Multiple sclerosis
Characterized by numbness or weakness in limbs, difficulty walking, lack of coordination, and other symptoms, it is caused by the immune system attacking the myelin sheath around axons in the brain and spinal cord, it slows or stops transmission of signals by those neurons
Glia
Vital, in the brain, just as numerous as
neurons
* More than just “glue”: support,
maintain, repair, insulate neurons,
and regulate neural activity.
- Problems with glia involved in many
neurological disorders
Astrocytes
Regulate chemical content of extracellular fluid, regulate synaptic transmission: they suck up neurotransmitter from the synaptic cleft, they also respond electrochemically to neurotransmitters, they support the blood-brain barrier, regular the blood flow
Why are axons wrapped in myelin
It provides insulation for better electrical conductance, NOT all neurons are myelinated tho
Oligodendrocytes
in the brain and spinal cord
Schwann cells
in the peripheral nerves
Microglia
Borne in bone marrow, enter the brain along with blood and immune cells, respond to damage, clean up dead cells, trigger inflammation, remodel synapses
Ependymal cells
line the central canal of the spinal cord and the ventricle of the brain, help create cerebra-spinal fluid an keep it moving with cilia
Radial glia
From a “scaffold” in the developing cerebal cortex, baby neurons migrate to their correct positions in the cortical layers by crawling of “migrating” along the radial glia fiber
WHAT IS A NEURON (REVIEW FROM PREVIOUS DECK)
A specific type of cell that in the nervous tissue of almost all animals.
* Its key function is to receive and process information and send signals to other
cells.
‣Neurons do computations
* When a neuron “fires,” or produces an “action potential,” an electrical signal
travels down its length.
* It then releases neurotransmitters onto other cells.
* Special features: shape, membrane channels & receptors, electrical charge,
action potentials & neurotransmitter release.
The neuron doctrine
Cell theory of biology: animal tissues are made of discrete cells, which are the fundamental building block of life
Gologis reticular theory
the nervous system is a continuous network, the the blood vessels
Cajal’s neuron doctrine
neurons are discrete cells and there is a cleft at the synapse each neuron is a ‘computational unit’
Outer membrane of a neuron
5 nm thick, studded with receptors and channels that differ in axon vs dendrites and differ across neuron types
Nucleus of a neuron
It is in the soma, transcribing genes and exporting mRNA
Rough endoplasmic reticulum
makes proteins for outer membrane, processed and shipped by the Golgi body
Mitochondria
Makes energy for all activity in the neuron
Cytoskeleton
microtubules, microfilaments, neurofilaments, continually shape the cell and transport molecules
The axon
When the cell receives enough positive input, it “fires” and send an electrical signal down it axon to other cells, <1mm to 1m long, variable thickness (thicker=faster), no rough ER or ribosomes, special proteins embedded in the membrane (channels, receptors and ion pumps), often wrapped in myelin, branches=axon collaterals
Axon terminal
aka “bouton”, is a swelling with no microtubules, many synaptic vesicles containing neurotransmitters, many mitochondria to meet a high energy demand, many protein molecules in the membrane, sometimes multiple boutons on the little branches (the terminal arbor); sometimes the axon continue past this point
Synapse
the point of contact between a presynaptic terminal of one cell and a postsynaptic dendrite of another cell, Cleft between them
Synaptic transmission
Presynaptic electrical signal which release of neurotransmitters then leading to postsynaptic electrical signal
Dendrites
Many little branches that form a tree, or arbor, membrane at synapses contains receptors for specific neurotransmitters, some spines which develop fluidly and isolate chemical reactions from the rest of the cell, lots of mitochondria and cytoskeletal structures, sometimes contain ribosomes for protein synthesis in reaction to synaptic transmission
Cytoskeleton
Microtubules, neurofilaments, microfilaments
Microtubulues
run lengthwise down axon and dendrites, microtuble-associate Proteins (MAPS) hold the structure together; One MAP, tau, is abnormal in Alzheimers disease, associate with distorted and dying neurons in the cerebral cortex, and severe dementia
Neurofilaments
provide strong structure
Microfilaments
made of actin, change cell shape, also in muscle cells
Axoplasmic transport
Stuff made in the soma must be transported down the axon, microtubules are the railroad tracks
Anterograde transport
Kinesin molecules use ATP to walk down the track, from soma to axon terminal, carrying vesicles full of proteins
Retrograde transport
Dynein molecules go the other day (1 meter a day)
Primary sensory neurons
activated directly by external energy of contact (light in the eye, touch of the skin)
Motor neurons
synapse onto muscle cells to make them contract
Interneurons (the most common)
form connections only with other neurons
Projection neurons
very long axons, like pyramidal cells
Local circuit neurons
short axons, like stellate cells
Dendrites are ____ or not
spiny
The axon is _____ or not
mylenated
Electron microscopy
electron bean rather than light to form images, much higher resolution to see tiny details
Fluorescence
When a substance absorbs light and then releases that energy as light of another wavelength
Laser microscopy
Scan a tissue sample with laster beams of a particular wavelength, often elicit fluorescence in tagged molecules
Retrograde tracing
- Some materials enter axon terminals and hitch a ride with Dynein
back up to the soma - Examples: horseradish peroxidase (HRP), herpes & rabies viruses
- Scientists attach a fluorescent molecule to that material
- This retrograde tracing reveals the bodies of cells that synapse into
a target region
Genetic engineering
The genomes of many organisms, including humans, have been fully sequenced.
* Scientists can create organisms with specific genes modified, deleted, or prevented from expression.
* They can copy a gene from one organism (“transgene”) and insert it into a particular place in the DNA of another
organism, such that it will only be expressed in certain cell types, in certain conditions.
GFP
green florescent protein
