Presentation on theme: "“myo = muscle” The Muscular System. Muscular System There are 650 skeletal musclesThere are 650 skeletal muscles They make up 40-50% of our body weightThey."— Presentation transcript:
“myo = muscle” The Muscular System
Muscular System There are 650 skeletal musclesThere are 650 skeletal muscles They make up 40-50% of our body weightThey make up 40-50% of our body weight Muscles play a crucial role in communicationMuscles play a crucial role in communication The smallest muscle in the body is the stapedius and controls the stapes (stirrup bone in the ear)The smallest muscle in the body is the stapedius and controls the stapes (stirrup bone in the ear) The largest muscle in the body???The largest muscle in the body??? –Gluteus maximus!
Important functions Movement – both voluntary & involuntary Maintaining posture Supporting soft tissues within body cavities Stabilizing joints Guarding entrances & exits of the body Maintaining body temperature
5 Skeletal muscle – –Striated, has stripes – –Voluntary, multiple nuclei – –Attached to bones Cardiac muscle – –Striated, has stripes – –Involuntary – –Responsible for heart contractions Smooth muscle:Smooth muscle: –non-striated, no stripes –found in the digestive tract, walls of blood vessels, reproductive system –controlled by the autonomic nervous system Types of Muscles
Anatomy of Muscles Muscle cells are called muscle fibers Nerve and blood supply Motor Unit – –Muscle fiber and neuron – –~150 fiber per neuron Neuromuscular Junction – –Communicate at synapse – –Ach (acetylcholine) – neurotransmitter in muscle contraction
Levels of Organization of a Muscle Muscle Fascicles Muscle Fibers (cells) Myofibrils Thick/Thin filaments
Connective Tissue Components Tendons – –Muscle to bone Aponeuroses – –Broad connection to bone (flat sheet between abs and dorsal muscles) Layers of connective tissue called fascia group muscles fibers together and give them strength
Connective Tissue Components Endomysium surrounds individual muscle fiber. Perimysium holds muscle cells together to form a fascicle. Epimysium surrounds groups of fasicles.
Sacromere Sacromere is the individual contractile unit of the muscle cell Sacromere is the individual contractile unit of the muscle cell Consists of: * Sarcolemma *Nuclei *Sarcoplasmic reticulum *Transverse tubules *Mitochondria
Myofibrils Myofibrils: protein strands inside of muscle cell Myofibrils: protein strands inside of muscle cell – Thin filaments: actin, troponin, tropomyosin – Thick filaments: myosin – Z line: boundary between sarcomeres
13 2 Types of Myosin Filament Red (Type I) fibers (slow twitch) – –Fatigue resistant endurance – –use aerobic metabolism White (Type II) fibers (fast twitch) – –participate in brief, powerful movements – –use anaerobic metabolism = slow twitch = fast twitch
14 The Effects of Exercise on Muscle Muscles respond to damage by producing more actin and myosin filaments. This increases muscle size, but not number. Disuse of muscles reverses this process, as in space travel.
Shape, Size and Arrangement Skeletal muscles are considered organs Skeletal muscles are considered organs Muscle arrangement and shape are suited to their function Muscle arrangement and shape are suited to their function ParallelConvergentPennate Bipennate Sphincter
During contraction one bones usually stays stationary During contraction one bones usually stays stationary Skeletal muscles can only pull, not push Skeletal muscles can only pull, not push Origin is point of attachment that doesn’t move Origin is point of attachment that doesn’t move Insertion is point that does move with contraction Insertion is point that does move with contraction Origin and Insertion Points
Muscle Actions Agonist (Ex: biceps brachii) – Also called the prime mover – Contracts to produce movement Antagonist (Ex: triceps brachii) – Performs opposing action of agonist – Relaxes during contraction Synergists (Ex: bracioradialis) – Contract at same time of agonist – Makes prime movers action more efficient Fixator muscles – Stabilize joints – Help maintain posture during movement
Lever Systems First class levers –Work like seesaws Second class levers –Work like wheelbarrow Third class levers –Work like shovel –Most common type in body
How Muscles are Named Location –Brachialis(arm) & gluteus(buttocks) Action –Adductor brevis Direction of fibers –Rectus abdominis Shape –Deltoid (triangular) Number of heads/divisions –Biceps, triceps, quadriceps Origin and Insertion –Sternocleidomastoid (sternum, clavicle, mastoid) Relative Size of muscle –Gluteus maximus, medius and minimus
Quick Check 1.Connective tissue that covers individual muscle fibers? 2. Connective tissue that covers and connects fascicles? 3. Connective tissue that covers and connects groups of fascicles to form a whole muscle? 4. What connects muscle to bone.
Quick Check 5.Name three fiber arrangements? 6. What is the point of attachment that does not move with contraction? 7. What point does move with attachment? 8. Muscle action that contracts to performs a movement? 9. What is the most common type of lever system found in the body?
Thick and Thin Filaments A. Thin Filament Actin Troponin Tropomyosin B. Thick Filament Myosin
24 Muscle Fiber Contraction In the resting muscle, troponin prevents interactions between actin and myosin. the first step (response to stimulus) in the chain of events leading to contraction)The arrival of an action potential (the first step (response to stimulus) in the chain of events leading to contraction)triggers an internal release of calcium. Calcium binds with troponin and allows actin and myosin to interact. The myosin filaments slide past the actin filaments, shortening the sarcomeres and contracting the fiber. Calcium is taken up again into internal organelles, troponin prevents actin and myosin interaction, and the fiber relaxes. Sliding Filament Theory
25 Copyright (c) Allyn & Bacon 2004 Muscle Fiber Contraction When stored Ca is released in the myofibril, it deactivates troponin, myosin interacts with actin by paddling. ATP then releases the myosin from the acitn. Role of ATP
26 – –Neurons in spinal cord or cranial nerve nuclei control contraction of muscles Neural Control of Muscles
28 The Control of Muscle Contractions A single action potential may be sufficient to produce contraction (twitch contraction) Varying amounts of force may be supplied by: – –varying the firing rate of alpha motor neurons. – –recruitment (activating more motor units as more load is placed on a muscle).
31 Control of Alpha Motor Neurons Alpha motor neurons receive input from: – –Muscle spindles – –Golgi tendon organs – –Brainstem and motor cortex neurons – –Spinal interneurons
32 The Muscle Spindle Senses Stretch
Muscle Disorders Muscle Atrophy: shrinkage of muscles due to lack of use. Muscle Spasms: uncontrolled tetanic contractions of a muscle group Muscle Cramp: painful muscle spasm usually due to ion and water imbalance. Rigor Mortis: no ATP so myosin head doesn’t release from actin. Role of ATPRole of ATP
Muscle Disorders Muscular Dystrophy: lack protein dystrophin which holds muscle fibers together. – –Death usually occurs ~21 from cardiac/respiratory muscle degeneration Myasthenia Graves: immune system attacks at neuromuscular junction nerve can’t stimulate muscle contraction – –Death usually results from respiratory distress