Lecture 2 Flashcards
What are the 2 major classes of cells in the brain?
Neurons and Glia
How many neurons are there? What is their function?
~85 billion neurons in the human brain
- receives, integrates, and transmit information (on average >1000 synaptic inputs)
What are the 3 major types of glia?
1) Oligodendrocytes and Schwann cells
2) Astrocytes
3) Microglia
What is the function of Oligodendrocytes and Schwann cells?
They wrap around the axon to provide insulation in the form of myelin.
What’s the difference between Oligodendrocytes and Schwann cells?
Oligodendrocytes are found in the CNS and Schwann cells are in the PNS.
What does glia mean?
Glue
What’s the function of Astrocytes?
They provide supporting function for neurons. They buffer potassium ions, take up glutamate released by neurons, and provide metabolic fuel.
What’s the function of microglia?
Resident immune cells in the brain; they become activated to help fight off infection and clear cellular debris via phagocytosis
What’s the general function of glia?
Insulate, support, and nourish neurons
What’s the general function of the neurons?
Process information, sense environmental changes, communicate changes to other neurons, and command body response
Excitable cells!
Define histology.
Microscopic study of tissue structure
What’s the differences between the 2 stains used?
Nissl Stain: stains cell bodies
- facilitates the study of cytoarchitecture in the CNS
Golgi Stain: sparsely stains whole cells
- allows imaging of a whole neuron - cell body and neurites
Who came up with the Reticular theory? What was it?
Camillo Golgi described nervous system as a continuous network.
Who came up with the Neuron doctrine and how? What is it?
Ramon y Cajal used the gogli stain.
Neuron Doctrine stated that the nervous system is made up of discrete individual cells.
- Neurons communicate by contact, not continuity.
- Neural circuitry
Describe how a model neuron looks.
Center body: Soma
Branches: dendrites
Long stem: Axon
What’s the neuronal membrane made of?
Phospholipid membrane encloses cytoplasm
~5 nm thick
Structure of discrete membrane regions influences neuronal function
What is in the cytoplasm?
cytosol: watery fluid inside the cell
organelles: membrane-enclosed structures within the soma
What is the nucleus responsible for?
Gene expression
Transcription
RNA processing
What’s the function of ribosomes?
Major site for protein synthesis
What’s the purpose of rough ER and golgi apparatus?
Sites for preparing/sorting proteins for delivery to different cell regions and regulating substances
What do free ribosomes produce?
cytosolic proteins
What is the function of the mitochondria?
site of cellular respiration, krebs system
What are the 3 structures in the cytoskeleton?
Microtubules: individual tubulin molecules
Microfilaments: individual actin molecules
Neurofilaments: long polypeptide molecules
List the 3 structures from smallest to largest in size.
Microfilament: 5 nm
Neurofilament: 10 nm
Microtubule: 20 nm
What are dendrites?
Antennae of neurons
Synapse = receptors
Spines = Postsynaptic (receives signals from axon terminal)
How long can axons be?
A millimeter to over a meter long
Describe the structure of an axon?
Beginning: Axon Hillock
Middle: Axon proper
Axons that branch off the main axon: axon collaterals
Site of synaptic transmission: Axon terminal
What are the differences between axon and soma?
ER doesn’t extend into axon.
Soma doesn’t have free ribosomes so no protein synthesis.
Protein composition of axonal membrane is unique
Differentiate anterograde and retrograde.
Anterograde: Soma to terminal transport
Retrograde: Terminal to soma transport
What are the 2 motor proteins responsible for transport?
Kinesin for anterograde transport
Dynein for retrograde transport
What are the main components of the axon terminal?
- No microtubules in terminal
- Presence of synaptic vesicles
- Abundance of membrane potentials
- Large number of mitochondria
What can dysfunction of the synaptic transmission lead to?
Mental disorders
What are 2 types of synaptic transmission?
- presynaptic neuron to postsynaptic neuron
- electrical to chemical to electrical transformation
What does the classification Golgi Type I mean?
long axons. Extend from one brain region to another
- projection neurons
What does classification Golgi Type II mean?
Short axons. don’t extend past immediate brain region
- local circuit neurons
How are different neurons classified?
1) Connections and functions within the CNS
2) Axonal Length
3) Gene Expression
4) Neurotransmitter type
5) Number of Neurites
6) Dendritic and Somatic Morphology
What does unipolar mean? Bipolar? Multipolar?
Unipolar: single neurite
Bipolar: two neurites
Multipolar: more than two
What are the different shapes neurons can be?
- Stellate cells (star shaped)
- Pyramidal cells (pyramid-shaped)
- spiny or aspinous
Brief description of astrocytes: amount in brain, where are they found, what do they do?
Most numerous glia in the brain
fill spaces between neurons
influence neurite growth and regulate chemical content of extracellular space
What 2 types of glia fall in the myelinating category?
Oligodendroglia and Schwann cells
What’s the node of ranvier?
Region where axonal membrane is exposed between adjacent myelinating cells
What is microglia? Function? Involved in what?
Specialized form of glia
- functions as phagocytes: pruning/elimination of synapses
- involved in regulating synapse numbers
