Transcript The Nervous system

The Brain and Neurons
Copy everything in RED and
draw/label when told to
Levels of Organization (copy the pyramid)
• Organ systems are living
things made of a group of
organs that contribute to
a specific function within
the body.
• Organs are living things
made of tissues that work
together to perform a
specific, complex function.
• Tissues are living things
made of a group of cells with
similar structures and
functions.
• Cells are the smallest unit of
life.
Types of Tissues
• Different tissue types work together within organs:
• Muscle tissue (most abundant):
controls internal movements of
materials (ex: blood, food)
• Epithelial tissue: closely packed cells
covering the surface of the body and
line internal organs (ex: inside
chambers of heart, glands)
• Connective tissue: holds organs in
place and binds different parts of the
body together (ex: tendons, ligaments)
• Nervous tissue: receives messages
from the body’s external and internal
environments, analyzes the data, and
directs response (ex: controls heart
beat)
Figure 35-2 Human Organ Systems Part I
Section 35-1
Nervous System
Integumentary System
Skeletal System
Muscular System
Circulatory System
Figure 35-2 Human Organ Systems Part 2
Section 35-1
Respiratory System
Endocrine System
Digestive System
Reproductive System
Excretory System
Lymphatic System
11 Functions
• Nervous: coordinates the body’s
response to change in the
internal and external
environments.
• Integumentary: serves as a
barrier against infection and
injury, helps to regulate body
temperature, provides protection
against UV radiation from the
sun
• Respiratory: provides oxygen
needed for cellular respiration
and removes excess carbon
dioxide from the body
Neurons
• Messages carried by the nervous
system are electrical signals =
impulses
• Nerve cells that transmit impulses =
neurons
• Sensory neurons: carry impulses from
sense organs to the spinal cord and
brain
• Motor neurons: carry impulses from
the brain and spinal cord to muscles
and glands
• Interneurons: connect sensory and
motor neurons and carry impulses
between them
Parts of a Neuron
• Cell body = largest part
containing nucleus and
cytoplasm (most metabolic
activity occur here)
• Dendrites = short, branched
extensions spreading out from
the cell body and they carry
impulses from the environment
or other neurons towards the
cell body
• Axon = long fibers that carry
impulses away from the cell
body and ends at the axon
A Neuron
DRAW and LABEL THIS
Section 35-2
Nucleus
Axon terminals
Cell body
Myelin sheath
Nodes
Axon
Dendrites
Synapse
• At the end of the neuron, the impulse
reaches an axon terminal where the
impulse may be passed along to another
neuron or another cell
• The location where a neuron
can transfer an impulse to
another cell = synapse
• The synapse is a small gap that
separates the axon terminal from the
dendrites of the next neuron or another
cell
• The terminals contain tiny sacs or
vesicles filled with neurotransmitters =
chemicals used by a neuron to transmit
an impulse across a synapse
• The impulse will continue with the
stimulation exceeds the cell’s threshold
Figure 35-8 The Synapse
Section 35-2
Direction of Impulse
Dendrite of
adjacent neuron
Axon
Vesicle
Receptor
Axon
terminal
Synaptic cleft
Neurotransmitter
Reaction activity
• Reaction time = the amount of
time required for an impulse
travel from your sensory
neurons to your motor neurons
Brain and Spinal cord
• Both are
• protected by bone
• wrapped in 3 layers of connective
tissue = meninges
• layers may have a space between
them filled with cerebrospinal fluid
which protects (shock absorber)
and exchanges nutrients and
waste
Brain
• About 100 billion neurons,
mainly interneurons
• Major parts of the brain:
•
•
•
•
•
Cerebrum
Cerebellum
Brain stem
Thalamus
Hypothalamus
Figure 35-9 The Brain
Section 35-3
Cerebrum
Thalamus
Pineal
gland
Hypothalamus
Cerebellum
Pituitary gland
Pons
Medulla oblongata
Spinal cord