Download The Nervous System

The Nervous System
Physiology Unit
CA Biology Standard 9


Standard 9a: Students know how the
complimentary activity of major body
systems provides cells with oxygen and
nutrients and removes toxic waste
products such as carbon dioxide.
Think about it…..How do the following
body systems act together to maintain
homeostasis?
Digestive System, Respiratory System,
Circulatory System
Standard 9a

Digestive System
– Breaks down food and delivers glucose to the
circulatory system.

Respiratory System
– Takes in Oxygen molecules through the lungs
and delivers to the circulatory system.
– Receives CO2 waste from the circulatory
system and removes from the body through
the lungs.

Circulatory System
– Carries glucose and oxygen to cells so they can
use them during cellular respiration to make
ATP
– Takes waste products like CO2 to the
appropriate place for removal from the body.
What is the Nervous System?


Recognizes and
coordinates the
body’s response to
changes in its
internal and external
environment.
Parts of the System:
– Brain
– Spinal Cord
– Peripheral Nerves
 A.K.A. Neurons or
Nerve Cells
Divisions of the Nervous System

Central Nervous System (CNS)
– The control center of the body
– Relays messages, processes information, and
analyzes information
– Consists of the brain and the spinal cord

Peripheral Nervous System (PNS)
– Lies outside of the CNS
– Consists of all nerves and associated cells that
are NOT included in the spinal cord
– Sensory Division: Transmits impulses from
sense organs to the CNS
– Motor Division: Transmits impulses from the
CNS to the muscles or glands
Neurons
Cells that transmit
nerve responses.
 3 Main Types

– Sensory Neurons:
Receive signals from
the external
environment.
– Interneurons: Carry
messages to other
neurons.
– Motor Neurons: Tell
muscles to move in
response to external
signal.
The Brain



Contains about 100 billion neurons
Weighs about 1.4 kg
Cerebrum
– Voluntary, conscious activities

Cerebellum
– Coordinates activity so muscles can
move efficiently

Brain Stem
– Connects the brain to the spinal cord
– Controls blood pressure, heart rate,
breathing & swallowing

Hypothalamus
– Recognition of hunger, thirst, fatigue,
anger and temperature.
– Coordinates nervous & endocrine
systems

Grey Matter
– Mostly neuron cell bodies

White Matter
– Mostly neuron axons
Spinal Cord
Main communication
link between the
brain and the rest of
the body
 31 pairs of spinal
nerves branch out
from the spinal cord
connecting the brain
to all parts of the
body
 Reflexes are
processed directly in
the spinal cord

Standard 9b
 Students
know how the nervous
system mediates communication
between different parts of the body
and the body’s interaction with the
environment.
What is a Reflex?
 Reflex:
A quick, automatic response to
a stimulus. Pathway occurs along the
Central Nervous System (CNS).
 Stimulus: Environmental item that is
sensed by an individual.
– Example: temperature, pressure, smells,
tastes, light and sounds
 Individuals
become aware of the
environment through the sense organs
and other receptors
 The body responds to stimuli through
reflex arcs.
The
Reflex
Arc
1.
2.
3.
4.
5.
Stimuli is sensed by receptors in skin
Message detected by sensory neurons
Message sent to interneurons in the spinal cord
Motor neurons then tell the muscle to move and
respond to the stimuli
The muscle is referred to as an effector
Stimuli
Effector