THE NERVOUS SYSTEM
Your nervous system receives, processes, and sends out
information, and it also monitors and responds to change in the
environment. Some activities your nervous system does
automatically are blinking, blood pressure, breathing, temperature,
digestion, shivering, and heart beats. Changes occurring in the
environment around you are called stimulus or stimuli. An
example of this would be when a bug comes near your eye, it
causes you to blink. The basic unit of structure in the nervous
system is called a neuron (nerve cells).
CELL BODY
NUCLEUS
DENTRITE
AXON
SYNAPSE
CNS
~ contains nucleus (houses it)
~ controls all activities of the cell
~ carries messages to the cell body
~ carries messages away from the cell body
~ space between two nerve cells
~ central nervous system
TYPES OF NEURONS:
SENSORY NEURONS ~ carries messages to the brain & spinal
cord
INTERNEURONS
~ “middle man” relays messages between
sensory and motor
MOTOR NEURONS ~ carry messages from CNS to body
Receptor cells detect changes in your surroundings. While
effectors (basically muscles) carry out the instruction of your CNS to
the body. A nerve impulse is an electro, a chemical message in the
nervous system. A nerve impulse can travel 120m/sec. A nerve
impulse can “jump” a synapse by getting a message which becomes a
chemical and flows across the synapse.
THE CNS & PERIPHERAL NERVOUS SYSTEM
The major parts of the CNS are the brain and the spinal cord.
The brain is the main control center. The spinal cord is the link
between the brain and the body.
THE BRAIN
The brain weighs 1.4kg (~3 pounds). The skull is protects the
brain along with 3 layers of tissue (that forms a pillow like coating)
and fluid. The three parts of the brain are the cerebrum (separates
humans from animals), medulla and the cerebellum.
THE CEREBRUM (pink part of the brain ~ on a model)
The cerebrum is the largest and arguably most important part of
the human brain. Important tasks that the cerebrum is in charge of are
the voluntary muscles, emotions, attitude, higher thinking and your
speech. The term hemisphere means that it is divided into two halves,
the right and left. The right hemisphere is responsible for your
creativity, you are artistic. It also controls the left side of your brain.
The left hemisphere is responsible for your math ability, logic,
analytical thinking. It controls the right side of your brain.
THE CEREBELLUM (brownish part of the brain ~ on a model)
The cerebellum coordinates muscle movement and balance.
THE MEDULLA (at the base of the brain stem)
The medulla connects the brain to the spinal cord. It controls
involuntary actions such as breathing, sweating, hear beat,
digestion… Autonomic processes refer to those that are involuntary
or automatic.
THE SPINAL CORD
The spinal cord is approximately 43cm long. The vertebra or
backbones protect the spinal cord. The spinal cord connects the
brain to the body and it controls reflexes. Reflex is a quick
response to a stimulus, an automatic reaction.
THE PERIPHERAL NERVOUS SYSTEM
The peripheral nervous system links between the CNS and
the rest of your body.