April 29, 2016 Neurophysiology Chul-Kyu Park, Ph.D. Assistant Professor Department of Physiology, Graduate School of Medicine, Gachon University,
Cells in the brain Neurons glia 1. Astrocytes 2. Microglia 3. Oligodendrocytes (Schwann cells) 4. Ependymal cells Endothelial cells
Identification of Neurons
Identification of Neurons
The neuron doctrine
The structure of neuron soma/cell body/perikaryon neurites (dendrites, axon)
Neurons are similar to other cells in the body Neurons are surrounded by a cell membrane. Neurons have a nucleus that contains genes. Neurons contain cytoplasm, mitochondria and other organelles. Neurons carry out basic cellular processes such as protein synthesis and energy production.
Neurons differ from other cells in the body Neurons have specialize cell parts called dendrites and axons. Dendrites bring electrical signals to the cell body and axons take information away from the cell body. Neurons communicate with each other through an electrochemical process. Neurons contain some specialized structures (for example, synapses) and chemicals (for example, neurotransmitters).
The soma Neuron's cell body
Gene expression in nucleus Central dogma in molecular biology
Gene expression in nucleus Contains genetic material (chromosomes) including information for cell development and Synthesis of proteins necessary for cell maintenance and survival. Covered by a membrane.
Rough endoplasmic reticulum System of tubes for transport of materials within cytoplasm. Can have ribosomes (rough ER) or no ribosomes (smooth ER). With ribosomes, the ER is important for protein synthesis.
Smooth ER and Golgi network
Mitochondria Produce energy to fuel cellular activities.
Cytoskeleton System of transport for materials within a neuron and may be used for structural support.
Axon Take information away from the cell body Smooth surface Generally only 1 axon per cell No ribosomes Can have myelin Branch further from the cell body Recurent collaterals
Axon terminal Microtubules do not extend into the terminal. Contains synaptic vesicles. Dense mitochondrial location Terminal bouton
Axoplasmic transport anterograde vs. retrograde transport slow transport (1-10 mm/day) fast transport (~10 cm/day) Useful method for circuit study /dynein
Dendrites Bring information to the cell body Rough surface (dendritic spines) Usually many dendrites per cell Have ribosomes No myelin insulation Branch near the cell body Synaptic polyribosome complex
Classification of neurons based on the number of neurites Pseudounipolar cells (example: dorsal root ganglion cells). Actually, these cells have 2 axons rather than an axon and dendrite. One axon extends centrally toward the spinal cord, the other axon extends toward the skin or muscle. Bipolar neurons have two processes extending from the cell body (examples: retinal cells, olfactory epithelium cells). Multipolar neurons have many processes that extend from the cell body. However, each neuron has only one axon (examples: spinal motor neurons, pyramidal neurons, Purkinje cells).
Classification of neurons based on dendrites 1. Pyramidal cells, Stellate cells 2. Spiny, aspinous
Classification of neurons Based on connections 1. Sensory neurons 2. Motor neurons 3. Interneurons Based on axon length 1. Golgi type I neurons (projection neurons) 2. Golgi type II neurons (local circuit neurons) Based on neurotransmitters
On/Off of Neuron
Electrophysiology Peripheral Nervous System Central Nervous System lamina II neurons Patch pipette DRG neurons Spinal neurons
Action potential: ON state of neuron
Neuroglia CNS PNS Astrocytes Microglia Oligodendrocytes Schwann cells
Astrocytes
Astrocytes
Properties of Astrocytes 1. Physical support for neurons 2. Maintenance of extracellular ion concentration 3. Neurotransmitter uptake 4. Maintenance of the blood-brain barrier 5. Induce Neurogenesis 6. Aid neuron migration 7. Respond to injury or infection astrogliosis 8. Expression of immune mediators :cytokines, chemokines, and adhesion molecules
Microglia
Microglia
Properties of Microglia 1. Innate immune cells of CNS 2. Become phagocytic cells upon activation 3. Rapid proliferation upon brain injury 4. Antigen presenting properties 5. Cytokine/chemokine production 6. Expression of neurotoxic mediators
Oligodendrocytes Provide the insulation (myelin) to neurons in the central nervous system.
Oligodendrocytes
Schwann cells Provide the insulation (myelin) to neurons in the peripheral nervous system.