Nervous System
Maintaining homeostasis a billion
messages at a time…
Functions
• Monitor changes: sensation
– Stimuli: sensory input (receptors)
– Internal and external
• Integrate
– Processes
– Interprets
– Generates response
• Respond
– Motor output
– Activates effector organs
Two divisions
• Central nervous system (CNS)
– brain and spinal cord
– Center for integration and control
• Peripheral nervous system (PNS)
– Nerves and assoc. cells outside of CNS
– Spinal nerves: carry information to and from the
spinal cord
– Cranial nerves: carry information to and from the
brain
Central Nervous System
• Integration and command center
– Relays messages
– Processes information
– Analyzes information
– Dictates motor responses
Peripheral Nervous System
• Communication lines
• Link all parts of the body to the CNS
Divisions of the PNS
• Sensory (Afferent) Division: TO the CNS
– Somatic afferent fibers: skin, skeletal muscles,
joints
– Visceral afferent fibers: visceral organs
• Motor (Efferent) Division: FROM the CNS
– Stimulates effector organs
– Effect (bring about) motor response
• Contraction
• Secretion
Branches of the Motor Division
• Somatic Nervous System
– Somatic motor nerve fibers
– CNS to skeletal muscles
– Voluntary – conscious control
• Autonomic Nervous System
– Visceral motor nerve fibers
– CNS to smooth and cardiac muscles and glands
– “a law unto itself” - involuntary
And finally: divisions of the Autonomic
Nervous System
• Control same visceral organs
• Opposite effects: antagonistic
• Sympathetic: fight or flight
– Emergency situations
– mobilization
• Parasympathetic: rest and digest
– Nonemergency functions
– Conserves energy
Sympathetic
CENTRAL NERVOUS SYSTEM
SYMPATHETIC
Brain
• Release adrenaline and
noradrenaline
• Increases heart rate and blood
pressure
• Increases blood flow to skeletal
muscles
• Inhibits digestive functions
Dilates pupil
Stimulates salivation
Relaxes bronchi
Spinal
cord
Salivary
glands
Lungs
Accelerates heartbeat
Inhibits activity
Heart
Stomach
Pancreas
Stimulates glucose
Secretion of adrenaline,
nonadrenaline
Relaxes bladder
Sympathetic
ganglia
Stimulates ejaculation
in male
Liver
Adrenal
gland
Kidney
Parasympathetic
CENTRAL NERVOUS SYSTEM
PARASYMPATHETIC
Brain
• Calms body to
conserve and
maintain energy
• Lowers heartbeat,
breathing rate,
blood pressure
Contracts pupil
Stimulates salivation
Spinal
cord
Constricts bronchi
Slows heartbeat
Stimulates activity
Stimulates gallbladder
Gallbladder
Contracts bladder
Stimulates erection
of sex organs
Summary of autonomic differences
Autonomic nervous system controls physiological arousal
Sympathetic
division (arousing)
Pupils dilate
Parasympathetic
division (calming)
EYES
Pupils contract
SALIVATION
Increases
Perspires
SKIN
Dries
Increases
RESPIRATION
Decreases
Accelerates
HEART
Slows
Inhibits
DIGESTION
Activates
Secrete stress
hormones
ADRENAL
GLANDS
Decrease secretion
of stress hormones
Decreases
Root Words
•
•
•
•
•
•
Peri: about, around, enclosing, surrounding
Aff: to
Eff: out, from
Visc: of or pertaining to the internal organs
Soma: body
Auto: self
Brain: basic anatomy
Lobes of the cerebrum…