Organization of Muscles - 600 human skeletal muscles in the body

Muscle Innervation - nerves supply muscles with directions on when to contract

The Functions of Muscles - movement of body parts and organ contents, maintains posture and prevents movement, control of openings and passageways, heat production

Gross Movement - the abilities required to control the muscles of the body for large movement

Communication - speech, expression, and writing

Myasthenia Gravis – muscles don’t receive signals to contract

Connective Tissues of a Muscle - epimysium, perimysium, endomysium

Epimysium - covers whole muscle belly and blends into CT between muscles

Perimysium - slightly thicker layer of connective tissue

Fascicle - a bundle of individual muscle cells

Endomysium - deepest layer of connective tissue, has thin areolar tissue around each cell that allows room for capillaries

Superficial → Deep - tendon, fascia, epimysium, perimysium, endomysium

Deep Fascia - found between adjacent muscles

Superficial fascia (hypodermis) - adipose between skin and muscles that protects and organizes muscles

Direct (fleshy) attachment to bone - directly attached WITHOUT tendons

Example of direct attachment: intercostal muscles e

Indirect attachment to bone - epimysium continues as tendon or aponeurosis that merges into periosteum as perforating fibers

Example of indirect attachment to bone: biceps brachii or abdominal muscle

Example of attachment to dermis: arrector pili muscle

Origin - attachment to stationary end of muscle

Belly - thicker, middle region of muscle

Insertion - attachment to mobile end of muscle

Flexors/extenders - work against each other to prevent hyperextension

Fusiform muscles - thick in middle and tapered at ends

Example of a fusiform muscle: biceps brachii

Parallel muscles - have parallel fascicles

Example of a parallel muscle: rectus abdominis

Convergent muscle - broad at origin and tapering to a narrower insertion

Pennate muscles - fascicles insert obliquely on a tendon

Unipennate - a muscle which fascicles are all on the same side on the tendon

Example of unipennate: extensor of the forearm

Bipennate - muscles that have fibers on two sides of a tendon

Example of bipennate: rectus femoris

Multipennate - fascicles that insert on multiple tendons tapering towards a common tendon

Example of multipennate: deltoid

Circular muscles - ring around body opening

Example of circular muscle: orbicularis oculi

Prime mover/agonist - produces most of the force

Synergist - aids the prime mover, stabilizes the nearby joint, and modifies the direction of movement

Antagonist - opposes the prime mover, prevents excessive movement and injury

Fixator - prevents movement of bone

Prime mover/agonist during Elbow Flexion = brachialis

Synergist during Elbow Flexion= biceps brachii

Antagonist during Elbow Flexion = triceps brachii

Fixator during Elbow Flexion = muscle that holds scapula firmly in place

Intrinsic and Extrinsic Muscles

Intrinsic muscles - contained within a region and contracts at the same place

Example of intrinsic muscles: tongue

Extrinsic muscles - found outside the region, the response is different than the contraction site Example of extrinsic muscles: wrist muscles

Nomina Anatomica - system of Latin names developed in 1895

Temporalis/Masseter - elevate the mandible

Medial/Lateral Pterygoids - help elevate the mandible, but also produce lateral swinging of jaw

Digastric and Mylohyoid = open mouth

Geniohyoid = widens pharynx during swallowing

Stylohyoid = elevates hyoid

Thyrohyoid = elevates larynx, closing glottis

Examples of sheetlike muscles: internal/external obliques, rectus/transverse abdominus

Functions of the sheet like muscles - support the viscera, stabilize the vertebral column, help in respiration, urination, defecation, and childbirth

Hernias - protrusion of viscera through muscular wall of abdominopelvic cavity

Inguinal hernia - occurs when tissue, such as part of the intestine, protrudes through a weak spot in the abdominal muscles

Hiatal hernia - occurs when the stomach protrudes through diaphragm into thorax

Umbilical hernia - viscera protrudes through the navel

Athletic injuries - caused by sudden and intense stress which is why it is important to condition properly and warmup

Common athletic injuries: shin splints, pulled hamstring, tennis elbow, plantar fasciitis

MTSS – medial tibial stress syndrome

Grade 1 Tear - microscopic tear

Grade 2 Tear - partial muscle tear

Grade 3 Tear - complete muscle tear

Tennis elbow - inflammation of lateral epicondyle

Golfer’s elbow - inflammation of medical epicondyle

Plantar fasciitis - heel pain cause by straining the ligament that supports the arch

Treatment for some athletic injuries: RICE

Types of muscle: skeletal, cardiac, and smooth

Physiology of skeletal muscle: basis of warm-up, strength, endurance, and fatigue

Responsiveness (excitability) - chemical signals, stretch and electrical changes across the plasma membrane

Example of responsiveness: blinking

Conductivity local electrical change triggers a wave of excitation that travels along the muscle fiber

Example of conductivity: brain signals

Contractility – shortens when stimulated

Extensibility – capable of being stretched

Elasticity – returns to its original resting length after being stretched

Skeletal Muscle - voluntary striated muscle attached to bones

Attachments between muscle and bone examples: endomysium, perimysium, epimysium, fascia, tendon

Collagen - extensible and elastic, stretches slightly under tension and recoils when released, protects muscle from injury, returns muscle to its resting length

Parallel components = parallel muscle cells

Series components = joined to ends of muscle

multinucleated – flattened nuclei are pressed against each other inside of the sarcolemma Myoblasts: stem cells that fuse together to form each muscle fiber

Satellite cells: unspecialized myoblasts remaining between muscle fibers and the endomysium

Sacro – replaces plasma membrane of muscle cells

Sarcolemma – outside

Sarcoplasm – inside

Sarcoplasm is filled with myofibrils = bundles of myofilaments

Types of myofilaments: actin, myosin

Actin – thin filament

Myosin – thick filament

Sarcoplasmic reticulum = smooth ER, network around each myofibril

Terminal cistern - store calcium

Triad = T tubule and 2 terminal cistern

Cistern - filters water, pumps water back to the “house”, storage tank to hold calcium

Thick Filaments - arranged in a bundle with heads directed outward in a spiral array around the bundled tails

Central area - bare zone with no heads

Thin Filaments - two intertwined strands fibrous (F) actin and globular (G) actin with an active site

Active site - tropomyosin molecules

Tropomyosin - blocks 6 or 7 active sites of G actins

Titin - springy proteins that provides elasticity, anchors each thick filament to Z disc, prevents overstretching of sarcomere

Contractile proteins - myosin and actin

Regulatory proteins - tropomyosin and troponin, determine whether myosin and actin can interact, switch that starts and stops shortening of muscle cell, contraction activated by release of calcium into sarcoplasm and its binding to troponin, , troponin moves tropomyosin off the actin active sites

Striations = Organization of Filaments

A band - thick filament region

H band - contains no thin filaments

I band - thin filament region

Z disc - Connects to actin and titin and form light band

Dystrophin - attaches to each Z disc which causes big movements

Axons of somatic motor neurons = somatic motor fibers

Terminal branches - supply one muscle fiber

Motor unit - each motor neuron and all the muscle fibers it innervates

Fine control - small motor units contain as few as 20 muscle fibers per nerve fiber

Example of fine control: eye muscles

Example of strength control: gastrocnemius

Neuromuscular Junctions (Synapse) - functional connection between nerve fiber and muscle cell

Synaptic knob - swollen end of nerve fiber (contains ACh)

Junctional folds - region of sarcolemma, increases surface area for ACh receptors, contains acetylcholinesterase that breaks down ACh and causes relaxation

Synaptic cleft - tiny gap between nerve and muscle cells

Basal lamina - thin layer of collagen and glycoprotein over all of muscle fiber

Pesticides (cholinesterase inhibitors) 0 bind to acetylcholinesterase and prevent it from degrading ACh

Tetanus or lockjaw - spastic paralysis caused by toxin of Clostridium bacteria, blocks glycine release in the spinal cord and causes overstimulation of the muscles

Flaccid paralysis (limp muscles) - due to curare that competes with ACh

Example of flaccid paralysis: respiratory arrest

Excitation = nerve action potentials lead to action potentials in muscle fiber

Excitation-contraction coupling = action potentials on the sarcolemma activate myofilaments Contraction = shortening of muscle fiber

Relaxation = return to resting length

Excitation (steps 1 and 2) - Nerve signal (action potential) opens voltage-gated calcium channels, Calcium stimulates exocytosis of synaptic vesicles containing ACh = ACh release into synaptic cleft

Voltage gated channels – opens when receiving an electrical stimulus

Excitation (steps 3 and 4) - Two ACh molecules bind to each to each receptor protein, opening Na+ and K+, Na+ enters, Then K+ exits and RMP returns to -90mV

End-plate potential (EPP) - Quick voltage shift is called first spark created when ACh binds to receptors

Excitation (step 5) - Voltage change (EPP) in end-plate region opens nearby voltage-gated channels producing an action potential that spreads over muscle surface

Excitation-Contraction Coupling (steps 6 and 7) - Action potential spreading over sarcolemma enters T tubules, Voltage-gated channels open in T tubules causing calcium gates to open in SR, Calcium enters the cytosol

Excitation-Contraction Coupling (steps 8 and 9) - Calcium released by SR binds to troponin, Troponin-tropomyosin complex changes shape and exposes active sites on actin, Calcium causes troponin and tropomyosin to move to make active sites available

Contraction (steps 10 and 11) - Myosin ATPase in myosin head hydrolyzes an ATP molecule, activating the head and “cocking” it in an extended position, It binds to actin active site forming a cross-bridge

Contraction (steps 12 and 13) - Power stroke requires ATP to cock and pull, myosin head releases ADP and phosphate as it flexes pulling the thin filament past the thick, causes slide

Relaxation (steps 14 and 15) - Nerve stimulation ceases and acetylcholinesterase removes ACh from receptors, Stimulation of the muscle cell ceases, Calcium drops – endocytosis, AChE – removes ACh

Relaxation (step 16) - Active transport needed to pump calcium back into SR to bind to calsequestrin

Relaxation (steps 17 and 18) - Loss of calcium from sarcoplasm moves troponin-tropomyosin complex overactive sites, stops the production or maintenance of tension, Muscle fiber returns to its resting length due to recoil of series-elastic components and contraction of antagonistic muscles

Rigor Mortis, Stiffening of the body beginning 3 to 4 hours after death caused by deteriorating sarcoplasmic reticulum releases calcium, Calcium activates myosin-actin cross-bridging and muscle contracts but cannot relax, Muscle relaxation requires ATP and ATP production is no longer produced after death

Dystonia - a movement disorder that causes the muscles to contract involuntarily

Length-Tension Relationship - Amount of tension generated depends on length of muscle before it was stimulated length-tension relationship (see graph next slide)

Overly contracted (weak contraction results) - thick filaments too close to Z discs and can’t slide

Too stretched (weak contraction results) - little overlap of thin and thick does not allow for very many cross bridges too form

Threshold = voltage producing an action potential

Twitch - a single brief stimulus at that voltage produces a quick cycle of contraction and relaxation (lasting less than 1/10 second)

Latent period (2 msec delay) = only internal tension is generated no visible contraction occurs since only elastic components are being stretched

threshold stimulus – any stimulus above threshold will result in a muscle contraction o

Isometric muscle contraction - develops tension without changing length, important in postural muscle function and antagonistic muscle joint stabilization

Tension while shortening = concentric

Tension while lengthening = eccentric

anaerobic fermentation (ATP production limited) - without oxygen, produces toxic lactic acid aerobic respiration (more ATP produced) - requires continuous oxygen supply, produces H2O and CO2

Phosphagen system - myokinase transfers Pi groups from one ADP to another forming ATP, creatine kinase transfers Pi groups from creatine phosphate to make ATP

Short-Term Energy Needs – anerobic respiration

lactic acid – causes cramps

Long-Term Energy Needs – aerobic respiration

Fatigue- Progressive weakness from use, ATP synthesis declines as glycogen is consumed

Central fatigue - Beyond what your brain said you could do

Endurance - Ability to maintain high-intensity exercise for >5 minutes determined by maximum oxygen uptake

Oxygen Debt - Heavy breathing after strenuous exercise o known as excess postexercise oxygen consumption (EPOC)

• Purposes for extra oxygen – replace oxygen reserves (myoglobin, blood hemoglobin, in air in the lungs and dissolved in plasma) replenishing the phosphagen system o reconverting lactic acid to glucose in kidneys and liver, serving the elevated metabolic rate that occurs if the body temperature remains elevated by exercise

Slow- and Fast-Twitch Fibers

• Slow oxidative - slow-twitch fibers, more mitochondria, myoglobin, and capillaries, adapted for aerobic respiration and resistant to fatigue

• Fast glycolytic - fast-twitch fibers, rich in enzymes for phosphagen and glycogen-lactic acid systems, sarcoplasmic reticulum releases calcium quickly so contractions are quicker (7.5 msec/twitch), extraocular eye muscles, gastrocnemius, and biceps brachii

Cardiac Muscle - thick cells shaped like a log with uneven, notched ends, Linked to each other at intercalated discs, electrical gap junctions allow cells to stimulate their neighbors o mechanical junctions keep the cells from pulling apart