The Muscular System

produce movement maintain posture stabilize joints generate heat Muscle Function

Excitability- respond to a stimulus Contractility- ability to shorten forcibly when adequately stimulated Extensibility- the ability to be stretched Elasticity- the ability of a muscle fiber to resume its resting length after being stretched Functional Characteristics

Skeletal Muscle Striated Multinucleate Voluntary

Cardiac Muscle Striated Uninucleate Involuntary Branching Intercalated discs

Cardiac Muscle Tissue

Smooth Muscle Unstriated Uninucleate Involuntary Hollow walled organs and blood vessels

Smooth Muscle Tissue

Gross Anatomy Skeletal Muscle

Muscle Anatomy myofibril sarcomere muscle fiber (cell)

Muscle Cell Sarcoplasmic reticulum

Myofibril

Myosin (Thick) Filament

Actin (Thin) Filament

Cross Bridges

Sliding Filament Hypothesis

No Calcium Ion Calcium Ion Present tropomyosin troponin myosin binding sites actin

Actin & Myosin Interaction

Biology 100 Human Biology Motor Unit spinal cord motor neurons muscle bundle muscle fibers neuromuscular junctions

Neuromuscular junctions branching axon to motor unit muscle fibers

Stimulation of Skeletal Muscle

stimulus latent period period of contraction period of relaxation Muscle Twitch

Contraction Response

Origin- fixed point of attachment; for biceps brachii O= clavicle and humerus Insertion- moveable, usually crosses a joint; O= radius Prime mover- - muscle group responsible for producing particular movement Antagonist- works opposite of prime mover Synergist-reduces undesirable or unnecessary movement Contraction of a muscle crossing 2 or more joints would cause movement of all if synergists weren’t there to stabilize it Ex. make a fist without bending wrist Fixator- specialized synergist- helps maintain posture; ex. muscles of the back fix scapula

Antagonistic Muscles

Direction of muscle fibers- straight, transverse Size of muscles- maximus, minimus, longus, brevis Location- frontalis, temporalis, occipitalis # of origins- biceps, triceps, quadriceps location of muscles origin and insertion- sternoclediomastoid- O= sternum and clavicle, I = mastoid process of temporal bone shape of muscle- deltoid- triangle shape, trapezius- trapezoid shape action of muscle- adductor muscle (adducts, brings in thigh) Naming skeletal muscles:

Frontalis Orbicularis oris Orbicularis oculi Masseter sternocledeomastoid zygomaticus aponerosa temporalis

Frontal Sternoclediomastoid Temporalis Masseter Obicularis oris Obicularis oculi Deltoid Pectoralis major Biceps Rectus abdominusExternal oblique quadriceps sartorius Tibialis anterior

Lattisimus dorsi aponerosa triceps Trapezius Deltoid occipitalis Gluteus maximus hamstrings gastrocnemus Achilles tendon

ATP is Generated by: 1.creatine phosphate ADP + creatine phosphate  creatine + ATP 2. lactic acid fermentation From stored glycogen via anaerobic glycolysis; glucose  pyruvic acid (no O 2 )  lactic acid O2O2 3. aerobic respiration Glucose  pyruvate  acetyl CoA  Krebs  CO 2 + H 2 O + ATP Energy for muscle contraction: ATP is the only energy source ATP  (ATPase + H 2 O)  ADP + Pi

Slow-Twitch Versus Fast-Twitch Muscle Fibers

Muscle Fiber Types Fast glycolitic Slow oxidative Fast oxidative-glycolytic Ratio- red:white (all 3 types in body)

white muscle fibers low myoglobin anaerobic glycolysis few mitochondria fast twitch fibers high glycogen stores short bursts fatigues easily Fast glycolitic:

Slow oxidative: red muscle aerobic high myoglobin low glycogen stores lots mitochondria slow long distance

Fast glycolitic-oxidative: red  pink aerobic fast high myoglobin intermediate amt. of mitochondria intermediate glycogen intermediate fatigue resistance

Red vs White Muscle long distance blue fin tuna- mostly red meat quick bursts- yellow tail- more white meat

Sprinter- anaerobic respiration Long distance Runner- aerobic respiration

Disuse- atrophy Muscles must be physically active if they are to remain healthy Cast Cast- muscle strength can decrease at a rate of 5%/ day; can use e- stimulus Avoid muscle injuries: warm up muscles- walk fast 5 minutes then stretch- avoids pulls and tares Effects of Exercise

cramp- sustained spasm or tetanic contraction; may be due to low blood sugar levels, electrolyte depletion, dehydration strain- muscle pull spasm- tics Muscle Injuries hernia- protrusion of organ through body cavity wall  may be due to heavy wts.

Isotonic and Isometric Contractions Isotonic contraction Contraction with a change in length The muscle shortens and movement occurs. Isometric contraction Contraction without any change in length The muscle does not shorten and there is no movement produced even though the muscle contracts.

Isotonic and Isometric Contractions Isotonic Isometric