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Unit 5: Body Systems
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table of contents, and then
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Levels of Organization
Recall that there are 6
characteristics of living things, we
are focusing on two for Unit 5:
• all living things are made up of
cells
• all living things are organized
Tissues are groups of similar types of
cells in multicellular organisms that work
together to carry out specific tasks
• Humans, like most
other animals, have
four main types of
tissue: muscle,
connective, nervous,
and epithelial
Add tissue to your index
• made up of layers of tightly
packed cells that line the
surfaces of the body
• examples of epithelial tissue
include the skin, the lining of
the mouth and nose, and the
lining of the digestive system
• made up of bands of cells that
contract and allow movement
• made up of many different types
of cells that are all involved in
supporting and binding other
tissues of the body
• examples include tendon,
cartilage, and bone. Blood is also
classified as a specialized
connective tissue
• made up of nerve cells that
sense stimuli and transmit
signals
• nervous tissue is found in
nerves, the spinal cord, and the
brain
• Organs are groups of different tissues
working together to perform a particular
job.
• Organ systems are groups of different
organs that work together to complete
a series of tasks.
Add organs and organ
systems to your index
Multicellular organisms usually have many
organ systems that work together to carry
out all the jobs needed for the survival of
the organism.
Right Now
• Copy down your homework
• Take out your homework
• Today’s Plan
– Review homework
– Continue notes on Body Systems
Place this tape-in into your notebook and label
each level of organization
• Systems may interact with other systems
• Systems may have subsystems and be
part of larger complex systems
The Circulatory System
• includes the heart, blood vessels
and blood
• transports oxygen, hormones
and nutrients to the body’s
cells
• moves waste and carbon
dioxide away from cells
The Excretory System
• includes the kidneys and bladder
• removes water, salts, and
waste products from blood and
body
• controls pH
• controls water and salt
balance
The Digestive System
• includes the stomach, small
intestine, and large intestine
• digests foods
• absorbs nutrients, minerals,
vitamins, and water
The Respiratory System
• includes the trachea, larynx,
pharynx, and lungs
• brings air to sites where gas
exchange can occur between the
blood and cells (around the body)
or blood and air (in the lungs)
The Muscular System
• includes cardiac (heart) muscle,
skeletal muscle, smooth muscle,
and tendons
• involved in movement and heat
production
The Nervous System
• includes the brain, spinal cord,
and nerves
• collects, transfers, and
processes information
The Endocrine System
• includes all of the glands of the
human body
• produces hormones
• regulates metabolism, growth
and development, sleep and
mood
Homeostasis
What is the first sign that you may be sick?
Homeostasis
The systems in your body work together to
maintain homeostasis
Homeostasis is the ability to maintain
constant internal conditions when outside
conditions change
System Interactions
• Nutrients are processed when the digestive,
muscular, and circulatory systems work
together.
• The respiratory, circulatory, muscular, and
digestive systems work together and process
oxygen and move wastes from the body.
• The nervous system communicates with the
muscular and skeletal systems and
coordinates movement and responds to
stimuli.
Unit 5 B: Signals in Your
Body
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table of contents, and then
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Sensory Receptors
• Sensory receptors are specialized cells to
detect specific stimuli
– Interoceptors – detect stimuli inside the body
• Include receptors for blood pressure, blood
volume, and blood pH
• Directly involved in homeostasis
– Exteroceptors – detect stimuli outside the
body
• Include receptors for taste, smell, vision, hearing,
and equilibrium
Add sensory receptors to
your index
Types of Sensory
Receptors
• Chemical receptors – respond
to chemicals
– Taste, smell, blood pH
• Photo receptors – respond to
light energy
– Vision (light)
• Mechanical receptors –
stimulated by mechanical
forces
– Hearing, gravity, motion, body
position
• Thermoreceptors –
stimulated by changes in
temperature
– Located in the hypothalamus
(region of brain) and skin
• Nociceptors (Pain
receptors) – free nerve
endings that are stimulated
by chemicals released by
damaged tissue
– Alert us to possible danger
How Sensation Occurs
There are three steps to
interpreting sensation:
• Detection occurs when
environmental changes stimulate
sensory receptors
• Sensation occurs when nerve
impulses arrive at the cerebral
cortex of the brain
• Perception occurs when the
brain interprets the meaning of
stimuli
The cerebral cortex
plays a key role in
memory, attention,
perception,
awareness, thought,
language, and
consciousness
• We are aware of a
reflex action when
sensory information
reaches the brain
• The brain integrates
this information with
other information
received from other
sensory receptors
Sense of Taste
• Taste buds contain
chemoreceptors and are
located primarily in the
tongue
• Different receptors exist
for salty, sour, bitter,
sweet tastes and umami
(savory)
How does the Brain Receive Taste
Information?
• Detection – food makes contact with
your taste buds
• Sensation – three different nerves in
your tongue send signals to your
brain
• Perception – your brain interprets
these signals and tells you what you
are tasting
Sense of Smell
• 80-90% of what we
perceive as taste is
actually due to smell
• Olfactory cells
– Chemoreceptors are
located high in the nasal
cavity
How does the Brain Receive Odor
Information?
• Detection – during respiration scent
molecules enter your nose
• Sensation – nerve fibers in your nose
send signals to your brain via the
olfactory tract
• Perception – your brain determines
what you are smelling or an odor’s
“signature”
Sense of Vision
• Vision requires the
work of the eyes
and the brain
• It is believed that at
least 1/3 of the
cerebral cortex
takes part in
processing vision
How does the Brain Receive Sight
Information?
• Detection – light enters the eye, it is
focused on photoreceptors in the
retina
• Sensation – signal is sent from optic
nerve to the visual cortex
• Perception – your visual cortex
deciphers the image
Sense of Hearing
• The ear has two sensory
functions- hearing and
balance (equilibrium)
– Sensory receptors for
both of these are located
in the inner ear
– Each consists of hair
cells with stereocilia (long
microvilli) that are
sensitive to mechanical
stimulation
(mechanoreceptors)
How does the Brain Receives
Sound Information?
• Detection – sound waves enter the
auditory canal and your ear drum
vibrates
• Sensation – the vibrations send
signals to your auditory cortex
• Perception – your brain interprets the
sound
Sense of Touch
• You probably think of the
sense of touch as relating to
your skin, after all, you have
about 5 million sensory nerve
receptors in your skin
• When the touch, pain or heat
sensors in your skin are
stimulated, they send electrical
pulses to your neurons,
special cells that relay
electrochemical impulses
How does the Brain Receive
Feeling Information?
• Detection – contact is made with sensory
receptors
• Sensation – sensory receptors send
signals to spinal cord
• Perception – brain receives and translates
signal from spinal cord to determine
feeling (touch, pain, heat, etc.)