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

striations Multi-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.

Human Physiology 301. (n. d.) Retrieved from http://people.eku.edu/ritchisong/RITCHISO/301notes3.htm

Muscle Contraction

Cross Bridge

Human Physiology 301. (n. d.) Retrieved on April 11, 2011 from http://people.eku.edu/ritchisong/RITCHISO/crossbridge3.gif

Figure 7-3, page 158

Sliding Filaments of Muscle Contraction

Human Physiology 301. (n. d.) Retrieved on April 11, 2011 from http://people.eku.edu/ritchisong/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

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 Walkhttp://www.bodybuilding.com/fun/strongman13.htm

Professor Abram’s Farmers Walk ExerciseTwo 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– 2nd question

Why would a “physically fit” person return to normal breathing and heart rate levels more quickly than an unfit person?

Farmers Walk– 2nd 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– 3rd question

Aerobic training also increases the number of mitochondria in muscle fibers.

Why would this benefit the muscle contraction process?

Exercise– 3rd 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 GroupsTable 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 ortrauma

Cramps are painful muscle spasms (involuntary twitches)

Infections Muscular dystrophy Myasthenia gravis

Questions?????

Do you have any questions?