Download Muscular and Skeletal System

Muscular and Skeletal
System
Powerpoint #2
Unit 8 – Chapters 35/36
Working together to create
movement
Skeletal System
Structures:
Bones
Cartilage
Ligaments
Tendons
Skeletal System
Function:
Supports body
Protects internal organs
Allows for movement
Stores mineral reserves
Provides a site for blood
cell formation
Bones:
206 bones in the
human body
Bones: 3 Parts
Spongy bone
–Not soft or spongy
–Very strong
–Structure resembles the
supporting structure of
bridges.
–Strong but lightweight
Compact bone:
–Very dense (no spaces
like spongy bone)
– Outer portion of bone
–Contains Haversian
canal for veins and
arteries to run though
Bone Marrow:
–Soft tissue
–Found in bone cavities
–Yellow Marrow: fat cells
–Red marrow: makes red
blood cells
8
Types of Muscle


The human body is comprised of 324 muscles
Muscle makes up 30-35% (in women) and 42-47%
(in men) of body mass.
Three types of muscle:
Skeletal muscle
Cardiac muscle
Smooth muscle
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A. Skeletal (Striated) Muscle





Connects the various parts of the skeleton through one or more
connective tissue tendons
During muscle contraction, skeletal muscle shortens and moves
various parts of the skeleton
Activated through signals carried to the muscles via nerves
voluntary control
Repeated activation of a skeletal muscle can lead to fatigue
Can have many nuclei
10
Skeletal Muscles work in PAIRS
Bending or straightening of elbow requires
the coordinated movement of biceps and
triceps muscles
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B. Smooth Muscle

Located in the blood vessels, the
respiratory tract, the iris of the eye, the
gastro-intestinal tract

The contractions are slow and uniform

Is fatigue resistant

Activation is involuntary

Has one nucleus
12
C. Cardiac Muscle

Has characteristics of both skeletal and smooth
muscle

Functions to provide the contractile activity of
the heart

Is very fatigue resistant

Activation of cardiac muscle is involuntary
(like smooth muscle)

Can have 2 nuclei, usually has 1
13
Components of skeletal muscle
myofibril
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muscle fiber
muscle fiber bundle
Muscle Fibers

Cylinder-shaped cells that make up skeletal muscle

Each fiber is made up of a number of myofilaments

Diameter of fiber (0.05-0.10 mm) Length of fiber (appr. 15 cm)

Each fiber contains contractile machinery and cell organelles

Group of fiber activated via same nerve: motor unit

Each fiber has capillaries that supply nutrients and eliminate waste

Divided into functional units called sarcomeres
15
High microscope magnification of sarcomeres
within a myofibril
16
Muscle Contraction

Organized in series ( attached end to end)

Two types of protein myofilaments:
- Actin:
thin filament
- Myosin: thick filament

Projecting from each myosin are tiny contractile
myosin bridges
17
Muscle Contraction
 During muscle contraction the myofilaments
myosin and actin slide toward each other and
overlap. This shortens the sarcomere and the
entire muscle. Muscle cells are "shocked" by
nerve impulses from motor neurons.
Muscle Contraction
The filaments slide together because myosin attaches to actin and pulls on it.
Myosin head (H) attaches to actin filament (A), forming a cross bridge.
After the cross bridge is formed the myosin head bends, pulling on the actin
filaments and causing them to slide:
Muscle contraction is a little like climbing a rope. The cross bridge cycle is:
grab -> pull -> release, repeated over and over
(a) At rest
b) Contraction
Cartilage
Tough, elastic, connective tissue
Found in: ears, between bones, larynx, and other various
places.
Tendons
Connect Muscle to Bone
Ligaments
Connect Bone to Bone