Lecture 25 - Neurons Flashcards
Neurons
Structural units of nervous system
Specialized cells that conduct messages in form of electrical impulses throughout body
Special characteristics of neurons
Extrem longevity
Amitotic
High metabolic rate
Neuron cell body
Aka perikaryon or soma
Biosynthetic centre of neurons where proteins,membranes and chemicals are synthesized
Nissl bodies
Granules of rough endoplasmic reticulum
Nuclei
Clusters of neuron cell bodies in CNS
Ganglia
Clusters of neuron body cells in PNS
Tracts
Bundles of neuron processes in the CNS
CNS contains both neuron cell bodies and their processes
Nerves
Bundles of nerve processes in PNS
PNS mostly made up of neuron processes
Dendrites
receptive regions of the cell and provide surface area for receiving signals from other neurons
Convey incoming messages toward cell body as GRADED POTENTIALS (short distance signals)
Axon
Each neurons has one axon
Some neurons, axons are short or absent
Others axons comprises almost entire .length of cell
Axon hillock
Cone shaped area where axon starts
Long axons
Nerve fibres
Axon branches aka…
Axon collateral
Ends of axon (branches)
Axon terminals
Axon functions
Conducting region of neuron
Generates nerve impulses and transmits them along axolemma to the axon terminal
Axolemma
Neuron cell membrane
Axon terminals
Secretory region of cell
Release neurotransmitters that either excite or inhibit other neurons or effector cells
Axon transport
Molecules and organelles are moved along axons by motor proteins and cytoskeletal elements
Anterograde
Movement away from cell body
Retrograde
Movement is towards the cell body
Viruses that use retrograde atonal transport
Polio
Rabies
Herpes
Tetanus toxins
Multipolar neurons
Most common type of neuron
Three or more processes
Bipolar neurons
Have a single axon and dendrite
Located within retina of eye and olfactory mucosa
Unipolar
Aka psuedounipolar
Have single T-shaped process
Peripheral process is associated with a sensory receptor and the proximal process enters the CNS
Functional class of neurons - sensory
Afferent neuron, conducts impulses TOWARD the CNS from receptors. Almost all are unipolar and cell bodies are located in ganglia in the PNS
Functional class of neurons- motor
Efferent neurons, conduct impulses from the CNS to effectors.
Multipolar
Functional class of neurons- interneurons
Aka association neurons
Conduct impulses between sensory and motor neurons, or in CNS integration pathways
Most are entirely within CNS
99% of body’s neurons are interneurons
