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CHAPTER 15
7TH GRADE
I Skin
A. largest organ of the body.
B. 3 layers—each has different cells
1. Epidermis—outer, thinnest layer.
a. cells are dead and repel water.
b. new cells push old ones to surface.
c. melanin—pigment protects skin—color
2. Dermis—contains blood vessels,
nerves, muscles, oil and sweat glands.
3. fatty layer—insulates the body-fat
deposited here cause weight gain.
II Function of skin
A. protection.
B. Sensory response
C. Forms vitamin D—absorbs calcium into
blood.
D. Regulates body temperature.
E. Gets rid of waste.
*Glands—regulate body temperature, evaporating
sweat cools the body.
3 million sweat glands
They release sweat, salt, and water.
III Skin injury
A. scratched, burned, ripped, exposed to
harsh conditions—new cells are made
to help repair these conditions.
B. Bruises—caused by bursting of
capillaries under the skin.
a. Red blood cells get into
surrounding tissues.
b. Hemglobin breaks down into
different
pigments—blue->red>purple->yellow
c. Swelling occurs because amount
of blood in tissue.
C. Skin grafts—are used to repair skin that
can not repair itself.
SECTION 2 (PAGE 439-443)
I Muscle System
A. 600 muscles
B. 2 types of muscles
1. Voluntary—muscles able to
use with conscious thought.
a. walking, chewing, winking,
smiling.
2. involuntary—muscles you do not
consciously control
a. heart, diaphragm, blinking.
D. 3 types of muscle tissue.
a. Skeletal—voluntary and move
bone—most common.
i. Tendons—attach muscle to
bone.
ii. Striated tissue makes up
skeletal muscle.
b. Cardiac—involuntary—found only
in the heart, also striated tissue.
i. Contracts 70 times per
minute.
c. Smooth muscle—involuntary—not
striated tissue-found in intestines,
bladder, blood vessels, and organs.
II Muscle Movement
A. Moves like a simple machine, opposing
pairs.
B. One muscle contracts—opposite muscle
extends.
C. Muscle always pull-never push.
D. Use of muscles makes them stronger and
faster.
E. Break down muscle—repairs itself
stronger.
F. Chemical energy changed to mechanical
energy and thermal energy.
SECTION 3 (PAGES 444-448)
I Functions of Skeletal System
A. Gives shape and support.
B. Protects organs.
C. Muscles are attached here.
D. Blood cells are made in bone marrow.
E. Calcium and phosphorus are stored.
II Part of Bones
A. Compact bone—vessels, cells, nerves—
periosteum—bone covering.
B. Spongy bone—end of long bones and
under compact bone—makes bones
light.
C. Marrow—2 types
a. yellow marrow—contains fat.
b. Red marrow—makes red blood
cells—2million to 3million per
second.
D. Cartilage—smooth, thick, slippery at
joints
a. Flexible and absorbs shock at
joints.
b. Reduces friction.
III Making Bone
A. Born with only cartilage.
B. Ostoeblasts—cells that form bone.
C. 300 bones at birth—206 bones as an
adult.
D. New bone always being made.
E. Ostelclasts—break down old bone and
release calcium and phosphorus into
blood to help body function.
IV Joints
A.
B.
C.
Where two or more bones come
together.
Ligaments—hold bones together with
tough bands of tissue.
Cartilage is between joints so bones
don’t rub.
V 2 Types of Joints
A. Immoveable—little or no movement.
a. skull, pelvis.
B. Moveable—allows body to make wide
range of motions.
a. pivot joint—one bone rotates and
other bone doesn’t move.
b. ball-n-socket—one bone has a
rounded end fits into a cuplike cavity on the other
bone.
i.legs, arms—at shoulder and
hip.
c. hinge—back and forth motion
i. elbows, knees, fingers.
d. gliding—one bone glides over
another—back and forth motion.
i. wrists, ankles, vertebrae
ii. used the most.
VI Moving with Comfort
A. Cartilage allows for smooth movement.
B. Reduces friction.
C. Disks are found in vertebrae.
VII Joint Problems.
A. ACL injuries.
B. Arthritis—1 out 7 people have it in USA
C. Slipped disks in the back.
SECTION 4 (PAGES 449-451)
I Nervous System
A. Cause a response to stimuli.
a. Stimuli—an external or internal
change that causes a response.
i. noise, food smells,
temperature, hormones.
B. Homeostasis—keeping the body at
steady, life-maintaining conditions.
a. regulation of heart, lungs, digestion.
II Nerve Cells
A. Neurons—basic units of the nervous
system.
B. 3 parts.
a. Cell body
b. Dendrites
c. Axon
C. Impulses—messages carried by
neurons—always go one way.
a. Stimulus->dendrites->cell body>response->cell body->axon.
D. 3 Types of Neurons
a. Sensory neurons—receive
information and send impulses to
brain or spinal cord.
b. Interneurons—relay these
impulses to motor neurons.
c. Motorneurns—conduct impulses
from brain or spinal cord to
muscles or glands in body.
E. Synapses—small spaces between
neurons—axon releases chemicals that
reach other neurons’ dendrite.
III Parts of Nervous System
A. Central nervous system—includes the
brain and spinal cord.
a. Brain—control center.
b. Spinal cord—bundles of
neurons—43 cm long.
B. Peripheral nervous system—all the
nerves outside the brain and spinal cord.
a. 12 pairs—cranial nerves—from
brain
b. 31 pairs—spinal nerves—from
spinal cord.
i. Somatic system—nerves
that cause voluntary
function.
ii. Autonomic system—nerves
that cause involuntary
function. Ex: heart, lungs,
digestion, glands.
C. Reflexes—an involuntary, automatic
response to a stimulus.
a. Reflex arc is sent from body injury
to spinal cord and back.
b. Brain is not used.
c. May keep body from further
injury.
I Senses
A. specific organs that intercept stimuli--
light rays, sound, heat, chemicals, pressure and
send them to the brain
B. Help maintain homeostasis.
II TypesA. Vision-light hits receptors in back of the
eye, which sends impulses to the brain.
1.Brain tells you what you are seeing.
2.Light passes through the cornea strikes
the retina.
3.Retina has rods and cones that are
sensitive to light.
a. Rods—let you see at night and are
sensitive to black and white.
b. Cones—are sensitive to color.
4. Impulses are sent through the optic
nerve to the brain.
B. Hearing
a. Outer ear—sound collector
b. Middle ear—sound amplifier
2. Has 3 bones and eardrum
c. Inner ear—cochlea and liquid
change vibrations to nerve
impulses.
d. Hearing allows you to collect
sound waves to be interpreted by
the brain.
e. Balance—inner ear controls this
1. cristae ampullaris—
react to rotating body
parts
2. maculae—responds to
tilt of the head.
C. Smell
a. Molecules from food moves into
the air.
2. These molecules stimulate
olfactory cells.
3. Enough molecules must be
present for a person to
smell.
4. Brain tells you what you
smell.
D. Taste
a. 10,000 taste buds all over your
tongue.
b. 5 tastes—sweet, salty, sour, bitter
and MSG.
c. To taste something must be
dissolved in water—saliva
d. Taste and smell are related.
II Drugs and Nervous System
A. Alcohol—goes directly to blood and slows down
neuron function in the brain. Can slow so much you
die.
B. Stimulants—speed up activity in the brain.