HUMB1000 Lecture Notes - Lecture 8: Central Nervous System, Peripheral Nervous System, Cranial Nerves
12 Jun 2018
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Introduction to the Nervous System
Functions of the nervous system
(1) Maintaining homeostasis
(2) Receives sensory input
a. Internal
b. External
(3) Integrating information
(4) Motor output
(5) Establish and maintain mental activity
Structural divisions of the nervous system
❖ Central nervous system (CNS)
❖ Brain and spinal cord
❖ Peripheral nervous system (PNS)
❖ Spinal nerves and cranial nerves
Functional divisions of the nervous system
Further terminology
• Neuron (nerve cell): basic structural unit of the nervous system
• Axon: nerve fibre
• Nerve: bundle of axons (or nerve fibres) and their sheaths (outer covering)
• Sensory receptors: neuron endings or separate specialised cells which detect
temperature, pain, touch, pressure, light, sound, odour and other stimuli
• Action potential: electrical signal
• Effector organ or effector cell: the organ or cell in which an effect or an action takes
place
• Ganglion: collection of cell bodies located outside the CNS
• Plexus: extensive network of axons or cell bodies
• Synapse: junction of a neuron with another cell e.g. end of a neuron with a muscle
cell or another neuron
Autonomic Subdivisions
❖ Involuntary and under subconscious control
❖ Action potentials travel from the CNS to smooth or cardiac muscle, or glands
❖ Two-neuron system
❖ Cell bodies are located in the CNS and autonomic ganglion
Somatic Subdivisions
❖ Voluntary and under conscious control
❖ Action potentials travel from the CNS to skeletal muscles
❖ Single neuron system
❖ Cell bodies are located in the CNS
Neuron
❖ Structural unit of the nervous system
❖ Dendrites
❖ Dendritic spines
❖ Cell body (soma)
❖ Axon
❖ Axon hillock
❖ Initial segment
❖ Trigger zone
❖ Axon collaterals
❖ Axon terminal or presynaptic terminal
❖ Terminal boutons or synaptic knobs
Types of neurons
Structural Classifications
Functional Classifications
Multipolar
Sensory neuron
Bipolar
Motor neuron
Unipolar
Inter-neuron
Central Nervous System
❖ Astrocyte cells
o Forming a supporting framework for blood vessels and neurons
o Assists in the formation of tight junctions between endothelial cells of the
capillaries
o Respond to tissue damage in the CNS
❖ Ependymal cells
o Line the central cavities of the brain and spinal cord
❖ Microglial cells
o Monitor the health of surrounding neurons
o Phagocytose microorganisms, infection, trauma or inflammation
❖ Oligodendrocytes
o Cover axons which forms an insulating sheath around them myelin sheath
Cells of the Peripheral Nervous System
❖ Schwann cells
o Also known as neurolemmocytes
o Form an myelin sheath around axons → insulating
❖ Satellite cells
o Provides support and nutrition to cell bodies in ganglia
o Protect cell bodies from harmful substances
Myelinated and Unmyelinated Axons
❖ Myelinated axons
o Nodes of Ranvier
❖ Unmyelinated axon
Document Summary
Functions of the nervous system (1) maintaining homeostasis (2) receives sensory input. Internal: external (3) integrating information (4) motor output (5) establish and maintain mental activity. Action potentials travel from the cns to smooth or cardiac muscle, or glands. Cell bodies are located in the cns and autonomic ganglion. Action potentials travel from the cns to skeletal muscles. Cell bodies are located in the cns. Inter-neuron: forming a supporting framework for blood vessels and neurons, assists in the formation of tight junctions between endothelial cells of the capillaries, respond to tissue damage in the cns. Ependymal cells: line the central cavities of the brain and spinal cord. Microglial cells: monitor the health of surrounding neurons, phagocytose microorganisms, infection, trauma or inflammation. Oligodendrocytes: cover axons which forms an insulating sheath around them myelin sheath. Schwann cells: also known as neurolemmocytes, form an myelin sheath around axons insulating.
