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Action and Support: The Muscles and Skeleton Introduction to Life Processes - SCI 102 1 Lesson 15

Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

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Page 1: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Action and Support:

The Muscles and

Skeleton

Introduction to Life Processes - SCI 102 1

Lesson 15

Page 2: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction

• Muscles: tissues that produce movement by

contracting

• Vertebrates have three types of muscles

(muscle tissue)

Skeletal

Cardiac

Smooth

Introduction to Life Processes - SCI 102 2

Page 3: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction

• Vertebrate skeletal muscles have highly organized,

repeating structures

Skeletal muscles move the skeleton and appear striated

This type of muscle tissue consists of a series of nested,

repeating parts

Introduction to Life Processes - SCI 102 3

Page 4: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction

• Parts of skeletal muscle

Tendons: muscles are encased in connective tissue sheaths

Muscle fibers are individual cells found within the sheath

Muscle fibers contain myofibrils encased in the sarcoplasmic

reticulum

Each myofibril consists of repeating elements called

sarcomeres, which contain the protein filaments that make up

muscles

• The filaments of myofibrils are made of myosin and actin, each of

which interacts with the other to contract the muscle fiber

Introduction to Life Processes - SCI 102 4

Page 5: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction

• Muscle fibers contract through interactions between thin and

thick filaments

• The sliding-filament mechanism describes how thick and thin

filaments slide over each other, shortening muscle length

Each spherical actin molecule has a myosin binding site

• Myosin binding sites are blocked by tropomyosin

During contraction, tropomyosin moves aside and exposes the myosin

binding sites

• The myosin heads bind to actin

• The myosin heads pull the thin filaments toward the sarcomere center,

sliding over the thick filaments

Introduction to Life Processes - SCI 102 5

Page 6: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction

• Muscle contraction uses the energy of ATP

Energy from ATP is used to extend the head on the myosin filament

so it can flex the thin filament toward the center of the sarcomere

A skeletal muscle’s reserves of ATP are used up quickly

Muscle cells carry creatine phosphate

• These molecules in muscle tissue quickly resynthesize ATP from ADP, but

only last a few seconds

Glycolysis can provide some ATP for short activities

Cellular respiration provides ATP for prolonged activity

• Glucose and fatty acids are used to form ATP

• An oxygen source is required for efficient ATP formation

Introduction to Life Processes - SCI 102 6

Page 7: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction

• The nervous system controls the contraction of

skeletal muscles

• Motor neurons excite skeletal muscle fibers at

neuromuscular junctions

Motor neurons release neurotransmitters that diffuse

across the synaptic cleft to receptors on the muscle fiber,

triggering an action potential

Introduction to Life Processes - SCI 102 7

Page 8: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction

The action potential travels along the muscle fiber cell membrane and

passes down T tubules, causing the sarcoplasmic reticulum to release

calcium ions into the myofibril cytoplasm

• Calcium ions bind to troponin accessory proteins

• Calcium-troponin binding causes tropomyosin to shift position, exposing

myosin binding sites on actin

• Myosin heads bind to actin

• The actin filaments slide past the myosin filaments, shortening the muscle fiber

When the action potential is over, calcium is actively transported back

into the sarcoplasmic reticulum

• Calcium is removed from the accessory proteins that block the actin binding

sites, and the muscle relaxes

Introduction to Life Processes - SCI 102 8

Page 9: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction

• The nervous system controls the contraction of skeletal

muscles

The size of motor units and the frequency of action potentials

determine the force of muscle contraction

• A motor unit is one branched motor neuron synapsing with many

muscle fibers

The size of a motor unit regulates the type of movement it can

generate

• The nervous system controls the strength of muscle contractions by

varying the number of muscle fibers stimulated and the frequency

of action potentials to each fiber

Introduction to Life Processes - SCI 102 9

Page 10: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction

• Fast-twitch and slow-twitch muscle fibers are

specialized for different types of activity

Muscle fibers come in two basic types, slow-twitch and

fast-twitch

• Slow-twitch fibers contract with less power than fast-twitch

• Fast-twitch fibers contract powerfully but fatigue more quickly

Introduction to Life Processes - SCI 102 10

Page 11: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction: Leg Muscles

• Leg muscle contractions

The strength of leg muscle contractions when lifting a

heavy object is determined by:

• The frequency of action potentials and number of muscle fibers

stimulated

• The largest motor units in the human muscles are

found in the leg muscles

Introduction to Life Processes - SCI 102 11

Page 12: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscle Contraction: Leg Muscles

• Leg muscle fibers

Fast-twitch muscle fibers

• Contain fewer mitochondria than slow-twitch fibers

• Are found in the legs of sprinters

Slow-twitch fibers

• Have more mitochondria

• Contract with less power than fast-twitch fibers but can keep

contracting for a long period of time

• Are found in the legs of marathon runners

Introduction to Life Processes - SCI 102 12

Page 13: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Cardiac, Smooth, and Skeletal Muscle

Property Smooth Cardiac Skeletal

Muscle appearance Nonstriated Striated Striated

Cell shape Tapered at both ends Branched Tapered at both ends

Number of nuclei One per cell One per cell Many per cell

Speed of contraction Slow Intermediate Slow to rapid

Contraction stimuliSpontaneous, stretch,

nervous system, hormonesSpontaneous Nervous system

Function

Controls movement of

substances through hollow

organs and tubes

Pumps blood Moves the skeleton

Under voluntary control? No No Yes

Introduction to Life Processes - SCI 102 13

The three muscle types differ from each other structurally and functionally

Type of Muscle

Page 14: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Cardiac, Smooth, and Skeletal Muscle

• Cardiac muscle powers the heart

The structure and contraction mechanism is similar to that of

skeletal muscle

• One main difference is that cardiac muscle fibers are connected to

each other by intercalated discs

Unlike skeletal muscle, cardiac muscle can generate its own

contractions

• The heart’s pacemaker does this

• Gap junctions allow for the synchronization of contractions by

allowing action potentials to travel from muscle cell to muscle cell

Introduction to Life Processes - SCI 102 14

Page 15: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Cardiac, Smooth, and Skeletal Muscle

• Smooth muscle produces slow, involuntary

contractions

Smooth muscle surrounds blood vessels and most hollow

organs

Smooth muscle cells are not striated because the thin and

thick filaments are scattered throughout the cell

Contractions are initiated by stretch, hormones, or the

nervous system and are slow and sustained

Introduction to Life Processes - SCI 102 15

Page 16: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Cardiac, Smooth, and Skeletal Muscle

• When a person builds up muscle strength, the

muscle becomes resistant to fatigue

In a strong muscle, there are often elevated levels of ATP

to give the muscle the extra energy it needs

Example: marathon runner’s leg muscles are resistant to

fatigue

Introduction to Life Processes - SCI 102 16

Page 17: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Cardiac, Smooth, and Skeletal Muscle

• People who work out often (bikers, athletes, trainers for the

Olympics) often require rapid bursts of high-energy muscle

output

Many of these people will spend money on dietary supplements

such as:

• Amino acids, which are used by the body as building blocks to make more

high-protein muscle cells

• Energy increasers, which are used to increase energy or provide more

endurance during workouts

Many supplements contain creatine, which can donate phosphate

ions to regenerate ATP when there is a lack of oxygen

Introduction to Life Processes - SCI 102 17

Page 18: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• The actions of antagonistic muscles on skeletons

move animal bodies

Three different types of skeletons are seen in the animal

kingdom

Coordinated movement of an animal’s body is produced

by alternating contractions of antagonistic muscles

Introduction to Life Processes - SCI 102 18

Page 19: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Worms, cnidarians, and many mollusks have a hydrostatic skeleton made of fluid and muscle Muscles around fluid cause shape changes and locomotion

• The bodies of arthropods are encased by rigid exoskeletons Movement occurs at joints and is based on antagonistic

muscles Arthropods must molt periodically in order to grow

• Endoskeletons are rigid structures found inside echinoderms and chordates Movement occurs at joints and is facilitated by antagonistic

muscles

Introduction to Life Processes - SCI 102 19

Page 20: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Endoskeleton

Rigid internal skeleton found in vertebrae (animals with a

backbone and humans), as well as in seas stars and related

animals

• The vertebrate endoskeleton serves multiple functions

It supports the body and protects internal organs

It allows locomotion in many different forms

It participates in sensory function in the middle ear

Bones produce blood cells

Bones store calcium and phosphorus

Introduction to Life Processes - SCI 102 20

Page 21: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• The vertebrate skeleton consists of two parts The axial skeleton includes the head, vertebral column,

and rib cage

The appendicular skeleton includes the pectoral and

pelvic girdle and the appendages attached to them

Introduction to Life Processes - SCI 102 21

Page 22: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• The vertebrate skeleton is composed of:

Cartilage

Ligaments

Bone

Introduction to Life Processes - SCI 102 22

Page 23: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Cartilage provides flexible support and connections

During embryonic development, most of the skeleton is

composed of cartilage, which is later replaced by bone

Cartilage covers the ends of bones and provides

flexible support to other parts of the body

The living cells of cartilage are called chondrocytes

• They secrete the collagen matrix

• Cartilage lacks blood vessels, and is slow to heal

Introduction to Life Processes - SCI 102 23

Page 24: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Cartilage plays many roles in the vertebrae skeleton

Examples:

• The entire skeleton of sharks, and many other fish, is composed

of cartilage

• Cartilage covers the ends of bones at the joints

• Cartilage supports the flexible portions of the body (ear, nose)

• Provides the framework for the larynx, trachea, and bronchi of

the respiratory system

Introduction to Life Processes - SCI 102 24

Page 25: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Composition of cartilage

Contains large amounts of glycoproteins

Often has elastic fibers

Lacks blood vessels

• Damage to cartilage tends to heal slowly because of the lack

of blood vessels

Introduction to Life Processes - SCI 102 25

Page 26: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Ligaments connect bone to bone in joints

Are mainly made up of wavy collagen fibers

Do not have significant amounts of elastic fibers

Introduction to Life Processes - SCI 102 26

Page 27: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Bone provides a strong, rigid framework for the body

Bone consists of a hard outer shell of compact bone that encloses spongy bone in its interior

• Compact bone is arranged in osteons, in which collagen and calcium phosphate surround a central canal containing blood vessels

• Spongy bone is lightweight, rich in blood vessels, and porous

There are three types of bone cells

• Osteoclasts break down bone

• Osteoblasts are bone-forming cells

• Osteocytes are mature bone cells

Introduction to Life Processes - SCI 102 27

Page 28: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Bone remodeling allows skeletal repair

Bone remodeling occurs through the coordinated activity

of osteoblasts and osteoclasts

• Bones become thicker and larger as a person grows

Bone remodeling varies with age

The ultimate bone remodeling occurs after a fracture

• Healing begins when a cartilage callus forms at the break site

• The cartilage is replaced by bone

Introduction to Life Processes - SCI 102 28

Page 29: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Bone strength is increased when it is given moderate stress

from weight-bearing exercises

• Many people hope that they will one day be able to travel

into space for extended periods of time

This comes with health risks to the bones and muscles

• Under weightless conditions, space travelers will lose bone and muscle

mass because there is no pull of gravity to strengthen the bones and

muscles.

• To maintain bone and muscle mass, they will have to do special, weight-

bearing exercises each day.

If they do not do exercise, their bones and muscles will atrophy (deteriorate),

which could have additional negative side effects on their body physiology.

Introduction to Life Processes - SCI 102 29

Page 30: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Antagonistic muscles move joints in the vertebrate

skeleton

Joints are held together by ligaments, which are strong

and flexible

• Tendons hold muscles to bones

The origin of any joint is where muscle is attached to the

immovable bone on one side of a joint

• Movement occurs in antagonistic muscle pairs when one muscle

flexes while the other is passively extended

• The insertion is where muscle is attached to the movable bone on

one side of a joint

Introduction to Life Processes - SCI 102 30

Page 31: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• Antagonistic muscles move joints in the vertebrate

skeleton

Hinge joints move in two dimensions

• Examples: elbows, knees, fingers

Ball-and-socket joints allow movement in many planes

• The round end of one bone fits into a hollow depression in another

• Allow movement in several directions

• Examples: hips, shoulder

Introduction to Life Processes - SCI 102 31

Page 32: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

• The knee joint

If there would be a ball-and-socket joint in the knee, there

would be decreased joint stability and the person would be

unable to stand properly

The anterior cruciate ligament (ACL) is one of the major knee

joint ligaments in humans, and damage to this ligament is fairly

common in athletes.

• An ACL tear is most often a sports-related injury but can also result

from accidents, falls, and work-related injuries. Most sports-related

ACL tears occur when a person pivots or lands from a jump.

Instability or weakness of the knee joint happens when a person

has a torn ACL

Introduction to Life Processes - SCI 102 32

Page 33: Action and Support: The Muscles and Skeleton · 2018. 11. 15. · Muscles and Skeletons Work Together to Provide Movement •The vertebrate skeleton consists of two parts The axial

Muscles and Skeletons Work Together to Provide Movement

Introduction to Life Processes - SCI 102 33

The biceps femoris

bends the leg back

when crouching