John Bertram; Week 7 MED1011; Anatomy
Lecture ContentEditNerves consist of nerve cells (neurons), supporting cells (glial cells), blood vessels. There are 30-100 billion neurons in the cortex. They recieve information, process and integrate these signals and conduct nerve impulses to target tissues. Purkinje cells are large neurons in cerebellum. The neuronal cell body contains the nucleus and surrounding cytoplasm, recieves nerve endings, contains highly developed RER (Nissl bodies), contains most organelles. Dendrites increase surface area, have no Golgi apparatus. Axons lack protein synthesis organisms so proteins must be transported down the axon.
May or may not be myelinated, produced by Schwann cells in PNS and oligodendrocytes in CNS. Myelin grows from mesaxon (area of connection where Schwann cell wraps around the axon. Nodes of Ranvier allow for saltatory/discontinuous conduction, speed determined by diameter of axon, thickness of myelin, length of segments. Oligodendrocytes have processes that form myelin sheaths around multiple adjacent axons.
Synapses can be axosomatic, axodendritic and axoaxonic.
Neuroglia are 10 times more abundant than neurons in the mammalian brain, surround neuron cell bodies and axonal and dendritic processes. Glial cells provide a microenvironment suitable for neuronal activity. In CNS this includes astrocytes, oligodendrocytes and microglia. In the PNS this includes Schwann cells.
Fibrous astrocytes are in white matter, protoplasmic are in grey matter. Release metabolic substrates and neuroactive molecules. Microglia are small elongated cells with short irregular processes. Can be phagocytic cells derived from bone marrow. Involved in inflammation and repair of CNS, can act as APCs. Secretes neural proteases, oxygen radicals and immunoregulatory cytokines.
Layering of gray matter in CNS is molecular, external granular, pyramidal, internal granular, large pyramidal and multiform.