Notes

Function of the Nervous System
Sensory input - gathering information
Sensory receptors monitor changes, called stimuli, occurring inside and outside the body
2. Integration
Nervous system processes and interprets sensory input and decides whether action is needed
3. Motor output
A response, or effect, activates muscles or glands

Organization of the Nervous System
A nervous system classifications are based on:
Structures (structural classification)
Activities (functional classification)

Structural Classification
Central nervous system (CNS)
Organs
Brain
Spinal cord
Function
Integration; command center
Interprets incoming sensory information
Issues outgoing instructions
Peripheral nervous system (PNS)
Nerves extending from the brain and spinal cord
Spinal nerves - carry impulses to and from the spinal cord
Cranial nerves - carry impulses to and from the brain
Functions
Serve as communication lines among sensory organs, the brain and spinal cord, and glands or muscles

Functional Classification
Sensory (afferent) division
Nerve fibers that carry information to the central nervous system
Somatic sensory (afferent) fibers carry information from the skin, skeletal muscles and joints
Visceral sensory (afferent) fibers carry information from visceral organs
Motor (efferent) division
Nerve fibers that carry impulses away from the central nervous system organs to effector organs (muscles and glands)
Two subdivisions
Somatic nervous system = voluntary
Consciously (voluntarily) controls skeletal muscles
Autonomic nervous system = involuntary
Automatically controls smooth and cardiac muscles and glands
Further divided into the sympathetic and parasympathetic nervous system

Nervous Tissue: Support Cells
Support cells in the CNS are grouped together as neuroglia
General functions
Support
Insulate
Protect neutrons

Nervous Tissue: Structure and Function
Nervous tissue is made up of two principal cell types
Supporting cells (called neuroglia, or glial cells, or glia)
Resemble neurons
Unable to conduct nerve impulses
Never lose the ability to divide
Neurons

Nervous Tissue: Supporting Cells
CNS glial cells: astrocytes
Abundant, star-shaped cells
Brace and anchor neutrons to blood capillaries
Determine permeability and exchanges between blood capillaries and neutrons
Protect neutrons from harmful substances in blood
Control the chemical environment of the brain
CNS glial cells: microglia
Spider like phagocytes
Monitor health of nearby neutrons
Dispose of debris
CNS glial cells: ependymal cells
Line cavities of the brain and spinal cord
Cilia assist with circulation of cerebrospinal fluid

CNS glial cells: oligodendrocytes
Wrap around nerve fibres in the central nervous system
Produce myelin sheaths
PNS glial cells
Schwann cells
Form myelin sheath around nerve fibres in the PNS
Satellite cells
Protect and cushion neutron cell bodies

Nervous Tissue: Neurons
Neurons = nerve cells
Cells specialized to transmit messages (nerve impulses)
Major regions of all neutrons
Cell body - nucleus and metabolic centre of the cell
Processes - fibers that extend from the cell body
Cell body is the metabolic centre of the neutron
Nucleus with large nucleolus
Nissl bodies
Rough endoplasmic reticulum
Neurofibrils
Intermediate filaments that maintain cell shape
Processes (fibers)
Dendrites - conduct impulses toward the cell body
Neurons may have hundreds of dendrites
Axons - conduct impulses away from the cell body
Neurons have only one axon arising from the cell body at the axon hillock
End in axon terminals, which contain vesicles with neurotransmitters
Axon terminals are separated from the next neutron by a gap