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Interest Grabber
Section 35-1
An Important Process
While walking along a dusty path, you begin to cough. As you continue
your walk, a small insect comes flying toward you. You blink and then duck
so that it misses you. These actions are just a few examples of
homeostasis. Homeostasis is the process by which organisms keep
internal conditions relatively constant despite changes in their external
environments.
1. List three other examples of homeostasis that occur in organisms.
2. Why is homeostasis important to an organism?
Section Outline
Section 35-1
35–1
Human Body Systems
A. Organization of the Body
1. Levels of Organization
2. Types of Tissues
B. Maintaining Homeostasis
1. A Nonliving Example
2. In the Body
Levels of Organization in a
Multicellular Organism
1. Cells
2. Tissues – groups of similar cells that
perform a single function
3. Organs – group of tissues that work
together to perform a complex function
4. Organ Systems – group of organs that
perform closely related functions
5. Organism
Humans contain 11 organ systems
that work together to maintain a
stable internal environment
(Homeostasis).
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 I
Section 35-1
Nervous System
Integumentary System
Skeletal System
Muscular System
Circulatory System
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 I
Section 35-1
Nervous System
Integumentary System
Skeletal System
Muscular System
Circulatory System
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
Excretory System
Reproductive System
Lymphatic System
Types of Tissues
Muscle Tissue
Epithelial Tissue
Connective Tissue
Nervous Tissue
1. Muscle Tissue
Most abundant
Controls the internal
movement of materials
Example: pushing food
through the digestive
system
Controls the external
movements of the entire
body or parts of the
body
Example: typing on a
keyboard
2. Epithelial Tissue
Cover the surface
of the body and line
internal organs
Consist of closely
packed cells
Example: lines
chambers of the
heart, makes up
glands
3. Connective Tissue
Holds organs in place
and binds different
parts of the body
together
Examples: tendons
and ligaments
Provides support for
the body
Pads and insulates
the body
4. Nervous Tissue
Receives messages
from the body’s
external and
internal
environments
Analyzes the data
and directs the
response
Maintaining Homeostasis
Feedback Inhibition
– Process by which the product of a
system shuts down the system or limits
its operation
– Examples
• Furnace in a house
• Temperature regulation in the body
• Human Menstrual Cycle
Examples of Feedback Inhibition
Section 35-1
Thermostat senses temperature
change and switches off heating
system
Heating system turns on
Room temperature decreases
Thermostat senses temperature
change and switches on heating
system
Interest Grabber
Section 35-2
You’ve Got a Lot of Nerve!
The nervous system controls and coordinates functions throughout the
body. The nervous system is one of the body’s communication systems.
Without communication, parts of the body could not work together
smoothly.
Interest Grabber continued
Section 35-2
1. Think about tying the shoelace of a sneaker. Construct a flowchart that
shows what happens between your eyes and your brain, and between
your brain and your hands, when you tie a bow in the shoelace.
2. How would the communications be different if you tried to tie the
shoelace with your eyes closed?
Section Outline
Section 35-2
35–2
The Nervous System
A. Neurons
B. The Nerve Impulse
1. Resting Potential
2. The Moving Impulse
3. Threshold
C. The Synapse
The Human Nervous System
Function – controls and
coordinates functions
throughout the body and
responds to internal and
external stimuli
Neurons (Nerve Cells)
Cells that transmit
impulses
(electrical signals)
3 types
Types of Neurons
Sensory – carry impulses from the sense
organs to the spinal cord and brain
Motor – carry impulses from the brain and
spinal cord to muscles and glands
Interneurons (associative neurons) – connect
sensory and motor neurons and carry
impulses between them
Parts of Neurons
Cell Body
– Largest part of a typical neuron
– Contains the nucleus and cytoplasm
– Most metabolic activity of the cell takes place
in the cell body
Dendrites
– Branched extensions
– Carry impulses from the environment or from
other neurons toward the cell body
Parts of Neurons (continued)
Axon
– Long fiber that carries impulses away
from the cell body
– Ends with axon terminals (small
swellings)
Myelin Sheath
– Insulating membrane that surrounds
some of the axons
– Increases the speed at which the
impulse can travel
A Neuron
Section 35-2
Nucleus
Axon terminals
Cell body
Myelin sheath
Nodes
Axon
Dendrites
Nerve Impulse
Production depends on the movement of
positively charged ions across a cell
membrane
Resting Potential
Difference in electrical charge across the
cell membrane of a resting neuron
Negative charge builds up on the inside of
the membrane
Positive charge builds up on the outside of
the membrane
Figure 35-6 Resting Potential
Section 35-2
Outside of cell
Cell membrane
Inside of cell
A nerve impulse begins when a neuron is
stimulated by another neuron or by its
environment.
Action Potential
Reversal of charges
Inside membrane gains a positive
charge and the outside gains a negative
charge
Figure 35-7 An Impulse
Section 35-2
Action Potential
At rest.
Action Potential
At the leading edge of the impulse, the
sodium gates open. The membrane becomes
more permeable to Na+ ions and an action
potential occurs.
As the action potential passes, potassium
gates open, allowing K+ ions to flow out.
Action Potential
The action potential continues to move along
the axon in the direction of the nerve impulse.
Figure 35-7 An Impulse
Section 35-2
Action Potential
At rest.
Action Potential
At the leading edge of the impulse, the
sodium gates open. The membrane becomes
more permeable to Na+ ions and an action
potential occurs.
As the action potential passes, potassium
gates open, allowing K+ ions to flow out.
Action Potential
The action potential continues to move along
the axon in the direction of the nerve impulse.
Figure 35-7 An Impulse
Section 35-2
Action Potential
At rest.
Action Potential
At the leading edge of the impulse, the
sodium gates open. The membrane becomes
more permeable to Na+ ions and an action
potential occurs.
As the action potential passes, potassium
gates open, allowing K+ ions to flow out.
Action Potential
The action potential continues to move along
the axon in the direction of the nerve impulse.
Figure 35-7 An Impulse
Section 35-2
Action Potential
At rest.
Action Potential
At the leading edge of the impulse, the
sodium gates open. The membrane becomes
more permeable to Na+ ions and an action
potential occurs.
As the action potential passes, potassium
gates open, allowing K+ ions to flow out.
Action Potential
The action potential continues to move along
the axon in the direction of the nerve impulse.
Threshold
Minimum level of a stimulus that is
required to activate a neuron
Any stimulus that is stronger than the
threshold will produce an impulse
Any stimulus that is weaker than the
threshold will produce no impulse
Synapse
Location at which a neuron can transfer
an impulse to another cell
Gap (small cleft) which separates the
axon terminal from the dendrites of
the adjacent cell
Terminals contain tiny sacs (vesicles)
filled with neurotransmitters
Figure 35-8 The Synapse
Section 35-2
Direction of Impulse
Dendrite of
adjacent neuron
Axon
Vesicle
Receptor
Axon
terminal
Synaptic cleft
Neurotransmitter
Neurotransmitters
Chemicals used by a neuron to transmit
an impulse across a synapse to
another cell
Diffuse across the gap and attach
themselves to receptors on the
membrane of the neighboring cell
Examples: Acetylcholine &
Norepinephrine
Interest Grabber
Section 35-3
Brainiac
Imagine that you are a computer systems engineer and your job is to
design a computer that can perform all the functions of a human brain.
1. Which brainlike functions can already be performed by computers?
2. Which brainlike functions cannot be performed by computers?
3. How successful do you think you (or anyone) could be in designing a
computer that can perform all the functions of the human brain? Explain
your answer.
Section Outline
Section 35-3
35–3
Divisions of the Nervous System
A. The Central Nervous System
B. The Brain
1. The Cerebrum
2. The Cerebellum
3. The Brain Stem
4. The Thalamus and Hypothalamus
C. The Spinal Cord
D. The Peripheral Nervous System
1. The Somatic Nervous System
2. The Autonomic Nervous System
Divisions of the Nervous
System
Central Nervous System
Peripheral Nervous System
Central Nervous System
Relays messages, processes information, and
analyzes information
Consists of the brain and the spinal cord
Wrapped in connective tissue (meninges)
Cerebrospinal fluid protects the brain and
spinal cord and serves as a site for
exchange
Brain
Cerebrum
– Site of
intelligence,
learning, and
judgment
Cerebellum
– Coordinates
and balances
the actions of
the muscles
Brain (continued)
Thalamus
– Receives messages
from the sense organs
and relays the
information to the
proper region of the
cerebrum
Brain Stem (pons
and medulla
oblongata)
– “switchboard”
regulating the
flow of
Hypothalamus
information
– Control center for
between the
recognition and
brain and the
analysis of hunger,
rest of the body
thirst, fatigue, anger,
and body temperature
Spinal Cord
Pathway that delivers messages to the
brain or moves messages from the
brain
Responds to stimuli requiring reflex
reaction
Diagram of reflex arc
Reflex Arc
Stimulus – Receptors
(Sense Organs)
Sensory Neurons
Brain or Spinal
Cord
Response –
Effectors
(Muscles or
Glands)
Motor Neurons
(Interneurons or
Associative
Neurons)
Peripheral Nervous System
Receives information from the
environment and relays commands from
the central nervous system to organs
and glands
Consists of all of the nerves and
associated cells that are not part of
the brain and the spinal cord
Divisions of the Peripheral
Nervous System
Sensory
– Transmits
impulses from
sense organs
to the central
nervous
system
Motor
– Transmits
impulses from
the central
nervous
system to the
muscles or
glands
Motor Division
Somatic Nervous
System
– Regulates
activities that
are under
conscious control
– Examples:
moving skeletal
muscles
Autonomic nervous
System
– Regulates
activities that
are automatic or
involuntary
– Examples:
heartbeat,
contraction of
smooth muscles
in the digestive
system
Concept Map
Section 35-3
The Nervous
System
is divided into
Central nervous
system
Peripheral
nervous system
Motor
nerves
which consists of
that make up
Somatic nervous
system
Autonomic
nervous system
which is divided into
Sympathetic
nervous system
Parasympathetic
nervous system
Sensory
nerves
Figure 35-9 The Brain
Section 35-3
Cerebrum
Thalamus
Pineal
gland
Hypothalamus
Cerebellum
Pituitary gland
Pons
Medulla oblongata
Spinal cord
Figure 35-11 The Spinal Cord
Section 35-3
Gray matter
Spinal nerve
Central canal
White matter
Meninges
Interest Grabber
Section 35-4
Taking It All In
Your senses—sight, hearing, smell, touch, taste—are constantly receiving
information about your environment. Even if you are not thinking about it,
your body is sensing and responding to conditions around you, such as the
temperature of the room.
1. List ten things you observe about the room you are in.
2. Next to each observation, write the sense that you used to make that
observation.
3. What sense did you use most?
Section Outline
Section 35-4
35–4
The Senses
A. Vision
B. Hearing and Balance
1. Hearing
2. Balance
C. Smell and Taste
D. Touch and Related Senses
The Senses of Smell and Taste
Section 35-4
Olfactory
(smell) bulb
Taste
sensory
area
Olfactory
nerve
Thalamus
Cerebral cortex
Smell
receptor
Nasal cavity
Smell
sensory area
Taste bud
Taste
pore
Taste
receptor
Sensory
nerve fibers
Figure 35-14 The Eye
Section 35-4
Vitreous humor
Muscle
Lens
Fovea
Aqueous humor
Cornea
Pupil
Optic nerve
Iris
Blood vessels
Ligaments
Retina
Choroid
Sclera
Figure 35-15 The Ear
Section 35-4
Anvil Stirrup
Hammer
Oval
window
Semicircular canals
Cochlear nerve
Cochlea
Bone
Auditory canal
Tympanum
Round window
Eustachian tube
Interest Grabber
Section 35-5
Poster Designer
Imagine that you are working with a local community group to help stop
drug abuse among teenagers. Your first assignment is to design a drug
abuse awareness poster.
1. Complete a brief sketch of your idea on a sheet of paper. What effects
of drugs does your poster depict?
2. Why do you think teenagers will pay attention to your poster?
Section Outline
Section 35-5
35–1
Drugs and the Nervous System
A. Drugs That Affect the Synapse
1. Stimulants
2. Depressants
3. Cocaine
4. Opiates
5. Marijuana
6. Alcohol
7. Alcohol and Disease
B. Drug Abuse
Commonly Abused Drugs
Section 35-5
Drug Type
Medical Use
Examples
Effects on the body
Stimulants
Used to increase alertness,
relieve fatigue
Amphetamines
Increase heart and respiratory rates;
elevate blood pressure; dilate pupils;
decrease appetite
Depressants
Used to relieve anxiety,
irritability, tension
Barbiturates
Tranquilizers
Slow down the actions of the central
nervous system; small amounts cause
calmness and relaxation; larger
amounts cause slurred speech and
impaired judgement
Opiates
Used to relieve pain
Morphine
Codeine
Act as a depressant; cause
drowsiness, restlessness, nausea