Energy Requirements and Skeletal Muscle Anatomy

Energy Source

ATP-energy source for muscle contraction and relaxation

ATP is provided from cellular respiration  (mitochondria)

The energy released from ATP breaks down to ADP

Much of the energy forms heat, which keeps our bodies warm

Cellular Respiration

Anareobic: Lack of oxygen Produces 2 ATP & lactic acid

1 glucose = 2 ATP Occurs in cytoplasm Fast process Inefficient ATP production

Areobic Oxygen present Produces CO2 and H2O & 36 ATP

1 glucose=36 ATP Occurs in mitochondria Slow process Efficient ATP production

Anaerobic

Very important during times of limited oxygen availability

Only occur for a short period of time (2-3 minutes)

Some lactic acid can diffuse out of the cell; the rest can cause short-term (a day or two) muscle pain

Anaerobic respiration is limited by depletion of glucose and buildup of lactic acid

Aerobic

During resting activities & long term exercise (long distance running) fatty acids are used primarily for ATP production

Energy Source

Creatine phosphate-high energy which increases regeneration of ATP

Stores energy that can be used rapidly to maintain adequate amounts of ATP

During inactivity: excess ATP is synthesized into creatine phosphate

During activity: reserves of ATP are used first, then energy stored in creatine phosphate is accessed to produce ATP for muscle contraction

Rigor Mortis

After a person dies ATP is not available, the cross bridges that are formed are not released, causing the muscle to become rigid.

Muscle Terminology

Muscle Twitch = Contraction of entire muscle in response to a stimulus

Threshold = The minimal strength required to cause a contraction

All-or-none response = Muscle fiber contract maximally or not at all. “Charlie Horse”

3 phases to muscle twitch 1. Lag Phase 2. Contraction Phase 3. Relaxation Phase

Phases of Muscle Twitch

Tetanus: When muscles remain contracted without relaxing Tetanus is infection of the nervous system with

the potentially deadly bacteria Clostridium tetani

Excess build up and release of Calcium

Muscle Terminology Continued Muscle Fatigue:  Results when ATP is used

faster than can be produced and lactic acid builds up faster than can be removed. Muscle loses ability to contract and relax after prolonged exercise or strain

Muscle Cramp:  a sustained involuntary contraction

Oxygen Debt: oxygen is used to create ATP, during exercise you may not have enough oxygen    -->  this causes Lactic Acid to accumulate in the muscles

Muscle Fatigue

Results when ATP is used faster than can be produced and lactic acid builds up faster than can be removed

ATP levels can fall too low for muscle cells to produce the maximum force of contraction

During extreme fatigue muscles may not be able to contract or relax; Physiological Contracture

Most common type of fatigue is psychological; perception of central nervous system

Oxygen Debt

After intense exercise respiration rates & volume remain elevated

Pays back oxygen debt that occurred during activity Converts lactic acid to

glucose Replenish depleted ATP

and creatine phosphate stores

Replenish oxygen stores in lungs, blood and muscles

Magnitude of oxygen debt depends on the intensity & length of time of exercise and the physical condition of the person

Exercise and training improves the ability to carry out both aerobic and anaerobic respiration

Muscle Terminology

Muscle Tone: Constant tension produced by muscles of the body over long periods of time.

Slow Fibers: Contract slowly and resistant to fatigue. Type I myosin “Dark Meat”

Fast Fibers: Contract quickly and fatigue quickly. Type IIa or IIb myosin “White Meat”

Muscle Memory: Muscle learn and remember contractions and actions “shooting a basketball”

Attachment of Muscles

Two points of attachment of each muscle are its origin and insertion

Origin = the immovable end of the muscle Insertion = the movable end of the muscle when a muscle contracts the insertion is moved

toward the origin Muscle are attached to bone with tendons

Origin and Insertion

Agonist vs Antagonist

Agonist = muscles working together to cause movement Example: Biceps brachii

Antagonist = muscles working in opposition to another muscle Example: Triceps brachii

Types of Muscle Contraction

Isometric Isotonic Concentric Eccentric

Muscular System

Front

Muscular System

Back

Muscular System

Side

Muscles of the Head and Neck