17: The Cells of the Nervous System Flashcards
What does the CNS consist of?
Brain and Spinal Cord
The main types of cells in the nervous system
Neuronal and Glial Cells
What do neurons do?
Conduct nerve impulses within the CNS, and between the central and peripheral nervous systems.
What must neurons be to conduct nerve impulses?
Neurons must be electrically excitable and be able to conduct electricity.
Structure of a Neuron
Dendrites, Cell body, Axon Hillock (Where cell body joins axon), Axon, Axon terminal (End of axon), Myelin Sheath, Nodes of Ranvier.
Dendrites function
Input Zone: Receive inputs (excitation occurs), Sends information to the cell body
Cell body function
Input Zone: Consists of nucleus and organelles, sums the input.
Axon Hillock function
Summation zone: makes decision whether to transmit signal down the axon.
Axon function
Conduction Zone: Carries electrical impulses, may or may not be myelinated.
Axon terminal function
Output Zone: neurotransmitter release
Myelin Sheath function
Multiple Schwan cells, increase conduciton speed of nerve impulses.
-Lipid layer around axon
Nodes of Ranvier
Gaps between myelin, increases conduction
What do glia cells do?
Maintain the local environment of neurons, act as ‘support cells’ (maintains homeostasis)
Types of Glia cells in CNS
Astrocytes, Microglia, Ependymal, oligodendrocytes.
Astrocytes
- Star shaped glia
- located near blood vessels from which they extract glucose for fuel.
- Supply nutrients for neurons, transmit information, unsheathe blood capillaries
- Form blood brain barrier that protects the brain from unwanted substances.
Microglia
- mobile
- immune cells of the CNS
- Engulf micro-organisms and debris
Ependymal Cells
- Line the fluid filled spaces in the brain and spinal cord (Ventricles)
- have cilia to circulate cerebral spinal fluid (CSF)
Oligodendrocytes
- Support nerve fibres
- Wrap around axons to insulate them forming myelin sheath.
Type of Glia cell in PNS
Schwann cells
Schwann cells
- supports peripheral nerve fibres
- Ensheath’s them with myelin
- Similar to oligodendrocytes but are for the PNS
Multipolar Neurons
Have one axon and many highly-branched dendrites coming form the cell body.
Bipolar Neurons
Have one axon and a single dendrite coming from the cell body.
(pseudo)Unipolar Neurons
One extension from the cell body which leads to an axon that then branches off into dendrites.
What is a synapse
Junction where a neural cell meets another cell and passes on information
