Nervous System
Ms. Bowman
Nervous System
• Master controlling and communicating system
of the body
• 1-Information that is gathered and sent to the
brain is sensory
• 2-The brain processes and interprets the
information and decides what action should be
taken
• 3-Brain sends a response called a motor output
Nervous System
Central Nervous
System
Spinal Cord
Peripheral
Nervous System
Brain
Motor
Autonomic
Sympathetic
Parasympathetic
Sensory
Somatic
Central Nervous System (CNS)
• Consists of brain and spinal cord
• The integrating and command center of the
nervous system
• Interprets sensory input and dictates motor
responses based on past experience, reflexes,
and current conditions
Peripheral Nervous System (PNS)
• The part of the nervous system outside of the
CNS
• Consists mainly of nerves that extend from the
brain (cranial nerves) and spinal cord (spinal
nerves)
• These nerves serve as the communicating lines
that link all parts of the body to the CNS
• 2 divisions-Sensory and Motor
Sensory Division of PNS
• “carrying toward”
• Consists of nerve fibers that convey impulses to
the CNS from sensory receptors located
throughout the body
• Keeps the CNS constantly informed of events
going on inside and outside the body
Motor Division of PNS
• “carrying away”
• Transmits impulses from the CNS to effector
organs (muscles and glands)
• Impulses activate muscles to contract and glands
to secrete
• They bring about a motor response
• 2 parts: Somatic and Autonomic
Somatic Nervous System
• Voluntary nervous system
• Composed of nerve fibers that conduct impulses
from CNS to skeletal muscles
• Allows us to consciously control our skeletal
muscles
Autonomic Nervous System
• Involuntary nervous system
• Consists of visceral (pertaining to your gut)
motor fibers that regulate the activity of smooth
muscles, cardiac muscles, and glands
• 2 subdivisions: Sympathetic and
Parasympathetic
Sympathetic Division of ANS
• Mobilizes involuntary body systems during
activity
Parasympathetic Division of ANS
• Conserves energy
• Promotes housekeeping functions during rest
Neurons
• Nerve cells
• The structural units of the nervous system
• Highly specialized cells that conduct messages in the
form of nerve impulses from one part of the body to
another
• Special characteristics
▫ Extreme longevity-can function for a lifetime
▫ Amitotic-lose ability to divide; most cannot be
replaced if they are damaged or destroyed
▫ High metabolic rate-require continuous and abundant
supplies of oxygen and glucose
Neurons
• Typically large, complex cells
• Vary in structure, but all have a nucleus and one
or more processes that project
• Processes
▫ Axons-conducting region; generate nerve
impulses and transmit them
▫ Dendrites-receptive or input region; information
collector
Classification of Neurons
• Multipolar-3 or more processes; most common
neuron type in humans and major type in CNS
• Bipolar-2 processes; one axon and dendrite; rare
neurons found in some special sense organs
• Unipolar-1 single short process that divides
T-like
Brain
• Protected by the meninges
▫ Comprised of 3 layers of connective membranes
 Dura Mater-strongest; outermost
 Arachnoid Mater- middle; forms a loose brain covering;
web-like projections anchor it to pia mater
 Pia Mater-composed of delicate connective tissue; lots of
blood vessels; innermost; clings tightly to brain
• Cerebrospinal Fluid (CSF)-watery “broth” that
forms a liquid cushion and protects the brain and
spinal cord; helps to nourish the brain
• Ventricles-canals that carry the CSF within brain
and brain stem
Brain
• Divided into 3 components
▫ Cerebrum
▫ Cerebellum
▫ Brain Stem
Cerebral Hemispheres
• Form the superior part of the brain
• Entire surface marked by gyri (elevated ridges of
tissue) that are separated by sulci (shallow
grooves)
• Fissures (deep grooves) separate large regions of
the brain
• Where our conscious mind is found; enables us
to be aware of ourselves and sensations, to
communicate, remember, understand, and
initiate voluntary movements
Cerebellum
• Processes inputs received from the cerebrum,
brain stem, and sensory receptors
• Provides the precise timing and appropriate
patterns of skeletal muscle contraction for
smooth, coordinated movements and agility
needed for our daily living
• Activity occurs subconsciously so we are not
aware of it
Brain Stem
• Produce the rigidly programmed, automatic
behaviors necessary for survival
• Origin of 10 of the 12 pairs of cranial nerves