Download Nervous System

KEY CONCEPT #3
The central nervous system interprets information, and
the peripheral nervous system gathers and transmits
information.
The nervous system’s two parts work together.
• The CNS includes the brain and spinal cord.
• The PNS includes four systems of nerves.
• The CNS and PNS pass signals between one another.
1.
2.
3.
4.
5.
Sensory receptor generates impulse.
PNS passes impulse to CNS.
CNS interprets impulse.
CNS passes impulse to PNS.
PNS stimulates a response .
The CNS processes information.
• The brain processes, interprets
signals and generates responses.
• Made up of three parts:
– cerebrum controls thought,
movement, emotion
– cerebellum allows for balance
– brain stem controls basic life
functions
Brain
stem
midbrain
pons
medulla
oblongata
• The brain stem controls life-sustaining processes
• Controls breathing and heart rate
• Has three parts:
– midbrain controls some reflexes
– pons regulates breathing
– medulla oblongata controls
heart function, swallowing,
coughing, aggression.
midbrain
pons
medulla
oblongata
• The spinal cord controls reflexes.
• Involves a
– sensory (receptor) neuron which receives the info and sends it to
spinal cord
– interneuron interprets the info and relays the impulse to the motor
(effector) neuron and causes an action/response
– does not involve the brain
The PNS links the CNS to muscles and other organs.
• The somatic nervous system regulates voluntary functions
like muscle movement
• The autonomic nervous system controls involuntary
functions like digesting food, breathing
• sympathetic nervous system:
controls “fight or flight” response
 Details: Raises heart rate
• parasympathetic nervous system:
calms the body
 Details: conserves energy;
lowers heart rate
KEY CONCEPT #4
The senses detect the internal and external environment
stimuli.
The senses help to maintain homeostasis.
• Senses gather stimuli, and send it
to the nervous system.
• Nervous system responds to
stimuli.
– Pupils shrink when too much
light enters the eyes.
– Goosebumps form when cold
air touches skin.
Types of Sensory (receptors) Neurons
 Mechanoreceptors: detects pressure, touch stretch,




motion, and vibration
Photoreceptor: detects visible light
Chemoreceptor: detects chemicals in the air
Thermoreceptors: responds to temperature differences
Pain receptors: detects pain
The senses detect physical and chemical stimuli.
• The eye contributes to vision.
– Iris controls the size of the pupil
which controls the amount of light
that enters the eye
– Photoreceptors located within the
retina sense light.
– Two photoreceptors work together:
– rod cells: detect light
– cone cells: detect color
Structure of the Eye
• The ear contributes to hearing.
– mechanoreceptors called hair cells
– bend in response to vibrations
Interpreting sound
 Pinna (auricle) collect the sound
 Sound waves travel down the auditory canal
 Sound waves hit the tympanic membrane (eardrum)
causing it to vibrate
 Vibrations are carried along the tiny bones in the ear called
the malleus, incus, and stapes.
 Eventually, the vibrations reach the organ of Corti which
bends the hair cells
 When the hair cells are stimulated, an impulse is sent down
the nerve fibers.
• Taste and smell use chemoreceptors.
– Taste uses tongue, and smell uses nose.
– Chemoreceptors detect chemicals dissolved in fluid.
• The skin senses touch.
• Mechanoreceptors detect pressure.
• Pain receptors detect damaged tissue.
• Thermoreceptors detect temperature.
pain receptor
light pressure receptor
hair follicle
heavy pressure receptor