Seminar 6 The Muscular System Tracy Abram, MAIS, BS

Introduction  Muscular tissue enables the body and its parts to move Movement caused by ability of muscle cells (called fibers) to shorten or contract Muscle cells shorten by converting chemical energy (obtained from food) into mechanical energy, which causes movement Three types of muscle tissue exist in body

3 Types of muscle  Skeletal-attach to bone  Cardiac-Heart muscle  Smooth-makes up many of your internal organs

Structure and Function  Types of muscle tissue Skeletal muscle — also called striated or voluntary muscle

Muscle Tissue  Function — all muscle cells specialize in contraction (shortening)  Let ’ s find out how it does that!

Skeletal muscle structure striationsMulti-nucleated

Parts of a Skeletal muscle  Origin — attachment to the bone that remains relatively stationary or fixed when movement at the joint occurs  Insertion — point of attachment to the bone that moves when a muscle contracts  Body — main part of the muscle

Professor Abram’s Muscles

Professor Abram’s Biceps/Triceps Triceps Brachii Biceps Brachii

Microscopic Structures Contractile cells called fibers — grouped into bundles Fibers contain thick myofilaments (containing the protein myosin) and thin myofilaments (composed of actin)

Myofibrils Myofibrils are protein strands. Very small 100 of them is equal to the diameter of a human hair strand. 100 of them is equal to the diameter of a human hair strand. Human Physiology 301. (n. d.) Retrieved from ng/RITCHISO/301notes3.htm

Muscle Contraction Cross Bridge Human Physiology 301. (n. d.) Retrieved on April 11, 2011 from ng/RITCHISO/crossbridge3.gif

Figure 7-3, page 158

Sliding Filaments of Muscle Contraction Human Physiology 301. (n. d.) Retrieved on April 11, 2011 from ng/RITCHISO/slidingfilaments. gif

Figure 7-3B, page 158

Functions of muscle?  Please list them…..

Functions of muscle?  Movement  Posture  Heat production  Let’s discuss how…

 Movement  How does this protect us?

Movement

Professor Abram’s Back

Posture  Posture or muscle tone

 Heat Production

Heat Production  Requires ATP  Contraction of muscle fibers produces heat  How relevant is this function???

Muscle Fatigue

Muscle Fatigue – what causes it?  Reduced strength of muscle contraction  Caused by repeated muscle stimulation without adequate periods of rest  Repeated muscular contraction depletes cellular ATP stores  Contraction in the absence of adequate oxygen produces lactic acid  Oxygen debt -

Role of Other Body Systems in Movement  Muscle functioning depends on the functioning of many other parts of the body  Respiratory, circulatory, nervous, muscular, and skeletal systems play essential roles in producing normal movements

Role of Other Body Systems in Movement Multiple sclerosis, brain hemorrhage, and spinal cord injury are examples of how pathological conditions in other body organ systems can dramatically affect movement

Motor Unit – how we get muscles to move!  Stimulation of a muscle by a nerve impulse.  B. A motor neuron is the specialized nerve that transmits an impulse to a muscle, causing contraction  C. A neuromuscular junction …  D. A motor unit …  Each muscle has specific nerves that function to make it move!!!

Types of skeletal muscle contractions  Twitch  Tetanic  Isotonic  Isometric

 Twitch  Tetanic  Isotonic  Isometric

Effects of Exercise on Skeletal Muscles  Improves muscle tone  Improves posture  Results in more efficient heart and lung functioning  Reduces fatigue

Effects of Exercise on Skeletal Muscles  Prolonged inactivity causes disuse, called atrophy  Regular exercise increases muscle size, called hypertrophy

Farmer Walk rongman13.htm

Professor Abram’s Farmers Walk Exercise Two 70 pound weights (one in each hand) Walk/Run quickly across the gym floor and back with shoulders back Drop weights and jump across a bench three times Eight Decline Push-up Repeat for 10 minutes without rest

Farmers Walk – ??? For You  Why do breathing and heart rate remain elevated after exercise stops?

Farmers Walk– The answer  Stored ATP is quickly depleted, and if oxygen supplies are not sufficient, muscle cells switch to energy conversion that does not require oxygen. However, this energy conversion produces lactic acid.  The “oxygen debt” is paid when labored breathing and an increased heart rate are required to remove lactic acid and replace depleted energy reserves, even after exercise has ended.

Farmers Walk– 2 nd question  Why would a “physically fit” person return to normal breathing and heart rate levels more quickly than an unfit person?

Farmers Walk– 2 nd answer  increased efficiency of the respiratory and circulatory systems  an increase in the number of blood vessels in muscles  more efficient delivery of oxygen and glucose to muscle fibers  more oxygen is available = the less “oxygen debt” there will be in the muscles.

Exercise– 3 rd question  Aerobic training also increases the number of mitochondria in muscle fibers.  Why would this benefit the muscle contraction process?

Exercise– 3 rd answer  Mitochondria are cellular organelles that convert glucose to ATP  Contraction of muscle cells requires ATP  an increase in the number of mitochondria in a muscle cell increases the speed with which ATP is produced in the cell.  Mitochondria = ATP

Body movements Figure 8-11  Rotation  Adduction and abduction  Pronation and supination  Dorsiflexion and plantarflexion

Examples of movement rotation

Skeletal Muscle Groups Table 8-1  Muscle of head and neck  Muscles that move the upper extremities  Muscles of the trunk  Muscles that move the lower extremities

Head and Neck What muscles are involved with eating?

Exercise – Learning activity  Let’s say we want to strengthen the various muscles listed here….  Biceps brachii  Pectoralis major  Gluteus maximus  Gastrocnemius  Rectus abdominus  What exercises should we do?

Exercise – Learning activity  Let’s say we want to strengthen the various muscles listed here….  Biceps brachii = arm curls  Pectoralis major = push ups  Gluteus maximus = squats  Gastrocnemius = foot flexion and extension  Rectus abdominus = sit-ups

Muscle disorders  Strain—injury from overexertion or trauma  Cramps are painful muscle spasms (involuntary twitches)  Infections  Muscular dystrophy  Myasthenia gravis

Questions?????  Do you have any questions?