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Seminar 6 The Muscular System

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1 Seminar 6 The Muscular System

2 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 3 Types of muscle Skeletal Cardiac Smooth

4 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

5 Microscopic Structures
Here’s the breakdown: Muscle >bundles of fibers>individual muscle fibers>sarcomeres>myofilaments A sarcomere is a contractile unit of a muscle fiber. Fibers contain thick myofilaments (myosin) and thin myofilaments (actin).

6 Figure 8-3, page 232

7 Sliding Filament Theory
Actin and myosin myofilaments slide past each other in a “ratchet” motion What two things are required for this contraction to occur?

8 Motor Unit – how we get muscles to move!
Stimulation of a muscle happens by a nerve impulse . Each muscle has specific nerves that function to make it move!!! A motor neuron is the specialized nerve that transmits an impulse to a muscle, causing contraction Neuromuscular Junction is the exact spot where the nerve enters the muscle

9 What are the functions of the muscular system?

10 Functions of the muscular system:
Movement Posture Heat production

11 Movement Prime Mover Synergist Antagonist
The main muscle responsible for a particular movement Synergist The muscle(s) that assist the prime mover with a particular motion Antagonist The muscle that works in opposition to the above

12 Posture Tonic muscle contraction allows us to maintain good posture

13 Heat Production Requires ATP
Contraction of muscle fibers produces heat

14 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 What is meant by Oxygen Debt?

15 Motor Unit Each muscle of the body has a particular nerve or several nerves that “innervate” that muscle. The muscle and the nerve that supplies it’s innervation are known as a motor unit.

16 Types of skeletal muscle contractions
Twitch Tetanic Isotonic Isometric

17 Twitch Tetanic Isotonic Isometric

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

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

20 The Step Test – The question
Why do breathing and heart rate remain elevated after exercise stops?

21 The Step Test – 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.

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

23 Step Test – 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.

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

25 Step Test – 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

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

27 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?

28 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

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

30 Review Function of the muscular system Structure of a muscle
Types of muscle tissue How a contraction occurs Types of contractions How exercise affects muscle

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