Chapter 1: The musculoskeletal system 1. 3 The muscular system: functions, types and major muscle groups Functions Body movement (voluntary control) Adequate posture Essential bodily functions (involuntary control) Types Smooth- digestive system, walks of vital organs and involuntary Cardiac- muscle of the heart, involuntary Skeletal (striated)- voluntary movements, development and maintenance of good posture Involuntary – no conscious control of the muscle (cannot be manipulated by you) Voluntary- conscious control of the muscle ^ Tougher test and exams questions on this ^ 1.
4 The muscular system: features, arrangement and microscopic- structure Common features of muscles Nervous control- muscle has nerve running to it from the brain (not every cell has nerves) Contractility- muscles contract and become thicker Extensibility- muscles have the capacity to stretch and extend when force is applied Elasticity- muscles can return to their original size and shape once stretched Atrophy- muscles can decrease in size (waste) as a result of injury, illness or lack of exercise Hypertrophy- muscles can increase in size (growth) with an increase in activity Muscles fibre arrangement Fusiform muscles
Fusiform muscles run the length of the muscle belly. They are designed for mobility because they produce contractions over a large range, yet they produce low force (eg. Sartorius and biceps) Pennate muscles Pennate muscles run at angles to the tendons. These muscles are designed for strength and power. Unipennate muscles- found on one side of a central tendon Bipennate muscles- run off either side of a central tendon (Looks like leaf) (E. g. rectus femoris) Multipennate muscles- branch out from several tendons (Looks like tree branch, good for force, down in flexibility) Structure of skeletal muscles The muscle fibre
The Essay on Internal Control System
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Each muscle fibre is surrounded by a cell membrane called the sarcolemma. Underlying the sarcolemma is a gel-like fluid called sarcoplasm. This fluid contains: Mitochondria – power house/manufacturer of energy in the cell (site of aerobic energy production) Haemoglobin- attached to red blood cells and carries the oxygen in blood cell Myoglobin- carries oxygen in the cell from the membrane to the mitochondria Fat, carbohydrate and protein (energy nutrients) Adenosine triphosphate (an immediate energy source) Enzymes (chemicals that speed up energy production) Actin and myosin myofilaments (contractile proteins)
Each muscle fibre is made up of long strands called myofibrils. Each myofibril consists of many individual units, called sarcomeres, which are responsible for contracting the muscle. 1. 5 The muscular system: initiation of muscular activity, action and control Nervous control of muscles: initiation of muscular activity To enable conscious control of muscles, the brain must send electrical nervous messages to the muscle. Motor units- consists of one motor neuron and the muscle fibre it stimulates. (Each neuron may stimulate a number of muscle fibres) Strength of muscular contraction
For a contraction to occur, there must be a strong enough nerve impulse to stimulate the muscle fibres. To ‘all or nothing’ principle Individual fibres can only contract 100% or not at all. The nerve impulse will not stimulate the muscle fibres until it reaches a certain threshold level. Once the nerve impulse reaches this threshold, all fibres of the motor unit will contract at the same time and maximally. Differences in force exerted are as a consequence/result of how many fibres are recruited/utilised. Intensity of muscular contractions can vary in two ways: 1. Varying the number of motor units stimulated (e. g.
The Essay on Differences Between the Excitation-Contraction Coupling Mechanism Between Skeletal and Cardiac Muscles
Outline the differences between the excitation-contraction coupling mechanism between skeletal and cardiac muscles. Excitation-contraction coupling is the combination of the electrical and mechanical events in the muscle fibres and is related by the release of calcium from the sarcoplasmic reticulum. (Silverthorn, 2007) In the skeletal muscle, action potential in the nerves is generated when the ...
lifting a heavy weight) more nerve impulses are sent, activating more motor units and therefore contracting more muscles fibres. 2. Varying the frequency at which the impulses arrive at the motor unit- The greater the frequency of nerve impulses, the greater the contractions in the muscle. If you require a large degree of strength (e. g. vertical jump) then impulses will be sent a faster rate to the muscles involved. Sensory neuron- message from ‘site’ via the central nervous system (CNS) to the brain Motor neuron- brain via central nervous system to the action site (muscle) Skeletal muscle action and control Muscle action
Skeletal muscles create movement by pulling on the bones to which they are attached. Origin- Fixed point of attachment that is closer (or proximal) to the body’s midline. Insertion- Usually attached to the bone that moves most when the muscle contracts. It is further (or distal) to the body’s midline. When a muscle contracts, the origin and insertion are drawn together, shortening the muscle. (a).
trapezius muscle (b).
deltoid muscle Muscle control Skeletal muscles work in pairs or groups to produce movement- as a muscle contacts on the front side of the body, usually the muscles at the back with the opposite action relax.
Agonist- muscle that causes the major action (prime mover) Antagonist- muscle that relaxes and lengthens to allows movement to occur Synergist- Muscle that assists the agonist to produce the required movement Stabiliser- Group of muscles that ensure that the joint remains stable during movement Coordinated movement Reciprocal inhibition- (works in pairs) process of one muscle contracting (agonist) while the other muscle relaxes (antagonist) to create movement Efficient movement involves a process of give and take on each side of the joint. 1. 6 The muscular system: muscle fibre types and muscular contractions Muscle fibre types
ATP: adenosine triphosphate, the basic source of energy for muscle cell metabolism and movement Slow twitch oxidative (Type 1) Contain large amounts of myoglobin, mitochondria and blood capillaries Red Resistant to fatigue Low intensity Aerobic work Longer duration (endurance) Split ATP at a slow rate Sports such as: marathons, triathlons, long-distance cycling and cross-country skiing. Fast twitch glycolytic (Type 2B) Low myoglobin, few mitochondria and blood capillaries Large amounts of glycogen White Fatigue easily Split ATP at a fast rate Power Sports such as: sprinting, throwing and weight lifting. Aerobic- with oxygen
The Essay on High Living Low Altitude Training
Athletes in preparation for a major competition prepare and practice to make their performance near perfect if not perfect. Indeed, there are various approaches that athletes have developed over the years in preparation for major competitions. Often, high altitude training is adopted. It involves taking practice, exercises and preparations for the main event to highly elevated areas such as ...
Anaerobic- without oxygen Characteristic Slow-twitch Fast-twitch oxidative Fast-twitch glycolytic Also known as Type 1 Type 2A Type 2B Colour Red Red White Used for Aerobic Anaerobic (long-term) Anaerobic (short-term) Fibre size Small Medium Large Motor neuron size (Nerve) Small Large Very large Resistance to fatigue (Long distance) High Medium Low Force production (Strength) Low High Very high Speed of contraction Slow Fast Very fast Hypertrophy potential Low High High Mitochondrial density High High Low Capillary density (Oxygen delivery) High Medium Low Myoglobin content High Medium Low Oxidative capacity
High High Low Glycolytic capacity Low High High Major fuel Triglycerides Creatine phosphate/glycogen Creatine phosphate/glycogen Types of muscular contraction Isotonic contraction- change in muscle length when muscle length shortens (a concentric contraction) or lengthens (an eccentric contraction) throughout the range of movement as force is being developed. Pushups Kicking Throwing Situps Change of length: Concentric – muscles shortens when contracts (e. g. biceps curl where the bicep muscle shortens to lift the dumbbell from the straight are position) Eccentric- muscle lengthens while the force is developed.
It occurs in activities that resist gravity. (E. g. lowering the body during a sit-up or during a squat).
Isometric contraction- generating a force with no change in length (produces the most amount of force of any type of muscular contraction, and therefore causes the muscle to tire more quickly).
(E. g. holding tennis racquet, rock climbing, wrestling and rugby scrum).
1. 7 Responses of the Muscular system to physical activity Increased motor unit and muscle fibre recruitment and muscular contractions Any physical activity creates a need for muscular contractions.
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Does not completing high school increase criminal arrests? The connection between dropout rate in high schools and crime statistics in America has been well established by numerous statistical surveys, which indicate that the probability for the school dropout to get involved in crime equals to approximately 90%. The reason is obvious; students academic inadequacy derives out of his mental ...
When exercise begins, motor unit recruitment must increase so that more muscle fibres are activated to contract. The greater the force or effort required, the greater the number of motor units recruited and the greater the number of muscle fibres activated. Increased blood flow to the muscles As the muscles demand extra oxygen during exercise, this leads to vasodilation of the capillaries and redistribution of blood flow from the internal organs to the working skeletal muscles. Increased muscle temperature Increased blood flow to the muscles coupled with the heat generated as a
by-product of the increased production of adenosine triphosphate (ATP, see chapter 3) during exercise, results in an increase in muscle temperature. Increased oxygen supply and utilization The muscle cells attract and utilize more oxygen during exercise because of the increased demand for ATP. Myoglobin attracts more oxygen to the muscles to be utilized by the mitochondria to produce energy. Depletion of muscle energy stores Muscular sources of fuel for the production of ATP — CP (creatine phosphate), glycogen and triglycerides — begins to deplete during exercise.
