Download The Nervous System

The Nervous System
3.
Objectives:
1.
Describe how the nervous system is divided into different
subsystems.
2.
Describe (Be able to label) a typical neuron.
Be able to trace the path of a reflex arc from stimulus to response.
The nervous system enables us to react to our environment
Cranial nerves
Spinal
nerves
Peripheral
Nervous
System (PNS)
CNS
Spinal cord
Sensory nerves
-carry messages
from inside &
outside to the
brain
2 parts
Somatic
Nervous
System
-under
conscious
control
Brain
Autonomic
Nervous
System
-without
conscious
control
motor nerves
-carry messages
from the brain to
the muscles
− works on a system of STIMULUS / RESPONSE
- change in the environment
detected by the body
- sensory neurons carry
impulses to the brain
- ex. Sight, sound, smell, taste,
touch (pressure & heat)
- body’s reaction to the
change
- motor neurons send
messages to the muscles
(for movement) and glands
(for hormone secretion)
Examples:
STIMULUS
Cookies Baking
Touch a hot stove
Watching a scary movie
RESPONSE
Saliva secreted in mouth
Pull hand away
Heart Rate increases,
sweating, jumping at
scary/loud noises
Nervous system
Central Nervous System
(CNS)
Peripheral Nervous System
(PNS)
- Brain
- Spinal cord
SOMATIC NERVOUS SYSTEM
- under conscious control
- ex. You need to go to the washroom,
but you can hold it.
ex. Your nose is itchy, so you scratch it.
AUTONOMIC NERVOUS SYSTEM
- without conscious control (it
happens automatically)
- ex. Heart beat, dilation of pupils,
saliva secreted. Etc.
The Nervous System: Neurons
dendrite
Cell body
nucleus
Direction of nerve
impulse transmission
Myelin sheath
axon
(Schwann cell)
Muscle cell
Terminal knob
Terminal branches
The Nervous System: Neurons
• A nerve cell or neuron is: a specialized cell that uses
electrical signals to communicate with other cells
• An impulse is: an electrical signal travelling through a
neuron
• A nerve is: a bundle of neurons
• Sensory neurons: carry impulses from receptors (e.g. in
skin) to the central nervous system (brain/spinal cord)
• Motor neurons: carry impulses from brain or spinal cord to
muscle or gland
• Dendrites: carry impulses toward cell body
• Axon: carry impulses away from cell body
• Myelin sheath: fatty white tissue that covers some axons
• Terminal knobs: part of neuron that attaches to another
cell
• Synapse: connection between terminal knob of one axon
and dendrite of another
Reflexes
• The PNS receives input from stimuli and transmits it
to the CNS for processing.
• The brain decides the appropriate responses and
send a signal back along the PNS to the part of your
body that will respond.
• HOWEVER… sometimes your brain gets bypassed!
• The spinal cord coordinates reflex (Actions that
don’t require your brain.)
• Reflexes occur without conscious thought and are
quick.
• EX. When you step on a tack or put your hand on a
hot surface.
illustration from
http://scienceblogs.com/neurotopia
Your Task
• Read pp. 170 – 173
• Answer Questions #4, 5, 7 on pp. 176
• Create a diagram or flow chart to explain
what happens in our nervous system when
we step on tack. (Start with the sensory
receptors and end with the movement off
of the tack. What nervous structures are
involved and in what part of the nervous
system are they located.)