Download The Nervous System

SNC 2D
 The organ system that is made up of
the brain, spinal cord, and the
peripheral nerves
 System that senses the environment
and coordinates appropriate responses
 Consists of the brain and the spinal cord
 Shielded by bones
 Skull protects the brain
 Spine protects the spinal cord
 Cerebrospinal fluid surrounds the brain and spinal
cord – cushions against injury and transports
chemicals and waste
 Consists of the nerves that connect the body to the
central nervous system
 Relays information about the internal and external
environments of the brain
 Subdivided into
 A) nerves that control voluntary muscles
 B) nerves that carry information from sensory organs
 C) nerves that regulate involuntary functions
 Specialized cells that make up nerve tissue are called
neurons
 Found in brain, spinal cord and nerves
 Approximately 100 billion neurons in human brain
 Neurons conduct electrical signals (nerve impulses)
from one area of body to another
 Nerve cell sends a signal through axon
 Attaches to dendrites of another cell
 Continues until reaches muscle cells
 Signal goes in only one direction
 Fatty material that surrounds the axon
 Acts like an electrical wire preventing electrical
impulses from passing to the wrong neuron
 Bundles of neurons surrounded
by connective tissue
 Allow two-way flow of information
even though each neuron transmits
information only in one direction
 Special cells or tissues that receive input from our
external environment and send signals along our
peripheral nerves to our central nervous system
 Ears, mouth, nose, muscles, and skin
 Other receptors are sensitive to
pressure, temperature, and pain and
make us aware of our balance,
position and motion
 Increase/decrease breathing rate
 Heart beat faster/slower
 Eat/drink/stop
 Perception
 Spinal Cord – acts as a short cut for reflexes
 Reflexes do not use brain, occur without conscious
thought (move hand away from hot surface)
 Peripheral nervous system can undergo cell division to
repair severed nerves (few mm distance)
 Central nervous system do not regenerate easily
 Multiple Sclerosis – destroys myelin sheaths so that
signals are mixed up
 Fall or blow – can result in paralysis, concussions
 Viruses and bacteria can cause permanent damage in
brain
 nervous system
 pork tapeworm