UNIT 5

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The Muscular System

Anatomy and

Physiology 1

Mrs. Canale

ESSENTIAL QUESTIONS:

What is the muscular skeleton’s function?

What is a muscle composed of ?

How do muscles contract?

REVIEW:

1. What type of muscles are:

are primarily voluntary

_______________________________

makes up the heart

_______________________________

is found in the digestive tract

_______________________________

2. Skeletal muscles are responsible for moving

_________________

3. What cell organelle provides the ATP needed for

muscle activity? _______________

WHEN I THINK ABOUT MUSCLES . . .

I THINK ABOUT . . .

Allow you to move

Attached to bone

Are attached to skin – ex your lips

Muscles move your vocal chords to speak

Different muscles are responsible for different

types of movements

Tiny muscles attached to the eye for precise

movements

Large muscles in your legs

Some muscles you control consciously - others are

automatic

LETS

MOVE!

Figure 6.2 (1 of 2)

Pectoralis major

•

Biceps brachii

•

Rectus abdominus

•

External oblique

•

Adductor longus

Quadriceps group

•

Tibialis anterior

•

Draws arm

forward

and toward the

body

Bends forearm at elbow

Compresses abdomen

• Bends backbone

• Compresses chest cavity

Lateral rotation of trunk

• Compresses abdomen

Flexes thigh

• Rotates thigh laterally

• Draws thigh toward body

Flexes thigh at hips

• Extends leg at knee

Flexes foot toward knee

THE

MUSCULAR

SYSTEM

Figure 6.2 (2 of 2)

Deltoid

•

Trapezius

• Lifts shoulder blade

• Braces shoulder

• Draws head back

Triceps brachi

• Straightens forearm

at elbow

Gluteus maximus

• Extends thigh

• Rotates thigh laterally

Achilles tendon

• Connects

gastrocnemius

muscle to heel

Hamstring group

• Draws thigh backward

• Bends knee

Gastrocnemius

• Bends lower leg at

knee

• Bends foot away from

knee

Example:

Movement:

Bend forearm up

Bicep origin = scapula

Bicep Insertion = radius

Raises arm

TERMINOLOGY:

Origin= end of muscle that attaches to a stationary

bone

Insertion = other end of muscle that attaches across a

joint

Contraction = causes insertion portion to move towards

origin

1. MUSCLE FUNCTION: PRODUCE MOVEMENT OR

GENERATE TENSION

Principle function

Contraction: shorten distance between bones

Skeletal muscle moves bone

Contraction of muscles (shivering keeps us warm).

Muscle groups

Synergistic: groups work together

Abdomen = sit ups (Rectus abdominus and External oblique)

Antagonistic: groups oppose each other

Bicep and tricep

Hamstring and quadriceps

MUSCLE STRUCTURE

Fascicles: bundles;

Connective Tissue

covering on each

one

Muscle fibers:

MANY muscle

cells

Figure 6.3

Tendon

Bone

Whole muscle

Muscle bundle (fascicle)

surrounded by connective

tissue (fascia)

Single muscle cell

(fiber)

Animation—Muscle

Structure and Function PLAY

Muscles ONLY contract or relax!

SKELETAL MUSCLE CONTRACTILE UNIT

Actin and myosin – protein filaments that allow

for muscle contraction.

Sarcomere – portion of muscle tissue that is

composed of actin and myosin (section of the

myofibril)

Myofibiril – individual fibers of muscle

Z Lines: attachment points for sarcomeres – gives

muscles its striation.

SKELETAL MUSCLE CONTRACTILE UNIT

Figure 6.5a–b

Practice!

4. Muscles fibers are made of individual fibers

(not filaments) called __________

5. Connective tissue that surrounds fascicles is

_________________________

6. A sarcomere is defined as the region

between two __________________________

Fascia

Z-lines

myofibrils

NERVE ACTIVATION OF INDIVIDUAL

MUSCLE CELLS

NERVE ACTIVATION OF INDIVIDUAL

MUSCLE CELLS

All muscles are excitable – meaning they contract

due to stimuli.

Causes - Acetylcholine (neurotransmitter) to be

released from motor neuron at neuromuscular

junction

Electrical impulse transmitted along T tubules

Calcium released from sarcoplasmic reticulum

Calcium allows for myosin and actin filaments to

slide over each other.

WHERE DOES THE CALCIUM COME FROM?

___________________

____________________

CALCIUM INITIATES THE SLIDING FILAMENT

MECHANISM

Figure 6.7

CALCIUM INITIATES THE SLIDING FILAMENT

MECHANISM

Thick filaments: myosin

Thin filaments: strands of actin molecules

Contraction: formation of cross-bridges between

thin and thick filaments

ENERGY REQUIRED FOR MUSCLE

ACTIVITY

Principle source of energy: ATP

ATP is replenished by a variety of means

Creatine phosphate (stored in muscle)

Stored glycogen

Aerobic metabolism of glucose, fatty acids, and other

high-energy molecules

WHY TAKE STEROIDS? WHAT DO THEY DO?

ACTIVITY OF MUSCLES CAN VARY

Isotonic contractions: muscle shortens, movement occurs (pushing or pulling)

Isometric contractions: muscle doesn’t shorten, no movement (standing up)

Degree of nerve activation influences force

TERMS TO KNOW:

Motor unit – motor neuron attached to muscle cells, some motor units only attach to a few muscle cells, others to thousands. (depends on the degree of dexterity needed).

Muscle tension – muscles are strained or tense

All-or-none principle - the strength by which a nerve or muscle fiber responds to a stimulus is not dependent on the strength of the stimulus. If you are pricked with a pin or hit with a hammer you will

still pull away

Muscle tone – helps maintain posture (resistance to passive stretch during resting state).

MUSCLE ACTIVITY

Slow-twitch and fast-twitch fibers

Slow twitch: endurance, long duration

contraction, contain myoglobin

Jogging, swimming, biking

Fast twitch: strength, white muscle, short

duration contraction

Sprinting, weight lifting, tennis

EXERCISE TRAINING

Strength training

Resistance training

Short, intense

Builds more fast-twitch myofibrils, tire quickly but

powerful.

Aerobic training

Builds endurance

Increases blood supply to muscle cells

Reach target heart rate at least 20 minutes, three

times a week

Slow-twitch myofibrils

FEATURES OF CARDIAC AND SMOOTH

MUSCLES

Activation of cardiac and smooth muscles

Involuntary

Specialized adaptations in each

Smooth muscle: Arranged in bundles not sacromeres.

Speed and sustainability of contractions

– smooth muscles can be continuously contracting

and not get tired (peristalsis)

Cardiac muscle – contracts and rests

Arrangement of myosin and actin filaments –

differs from skeletal muscle.

DISEASES AND DISORDERS OF THE MUSCULAR

SYSTEM

Muscular dystrophy – lack dystrophin = too much

calcium leaks into muscle and kills off muscle

cells.

Tetanus – bacterial infection, causes lock jaw,

causes calcium to leak and cause constant muscle

contraction.

Muscle cramps – dehydration and ion imbalance

Pulled muscles – tear in muscle fibers

Fasciitis - inflammation of the connective tissue

around the muscle

ANABOLIC STEROIDS

| Steroids

| The Mitchell Report

PLAY

PLAY

PRACTICE!!