Muscular System.

Muscular System

Functions The main functions of the muscular system are:
movement bones at joints, maintenance of posture, producing body heat, movement of viscera, peristalsis, and pumping of the heart

Types of Muscle Skeletal – striated & voluntary Smooth – involuntary
Cardiac - heart The word “striated” means striped. Skeletal muscle appears striped under a microscope.

Skeletal Muscle Structure
A skeletal muscle is an organ of the muscular system made of skeletal muscle tissue, nervous tissue, blood, and connective tissues

Connective Tissue Coverings
Fascia- layers of fibrous connective tissue, separate a skeletal muscle from other muscles and hold it in place Fascia can extend beyond muscle fibers and connect to a bone – called a tendon – tendon connects with periosteum Fascia can also attach to coverings of other muscles and form broad sheets called aponeuroses

Muscles and Muscle Fiber Structure
Individual muscles are separated by FASCIA, which also forms tendons Video on plantar fasciitis.

Epimysium is the covering of the muscle, perimysium is inward and separates muscle into compartments Muscles are composed of many fibers that are arranged in bundles called FASCICLES Each fiber in a fascicle has connective tissue covering called endomysium All the connective tissue coverings are connected to each other

EPIMYSIUM = outermost layer, surrounds entire muscle.
PERIMYSIUM = separates and surrounds fascicles (bundles of muscle fibers) ENDOMYSIUM = surrounds each individual muscle fiber This model of the muscles uses straws to represent fibers. Green = endomysium Yellow = perimysium Blue = epimysium

Muscle Layers

Epimysium Perimysium Endomysium

Skeletal Muscle Fibers
Skeletal muscle fiber – single cell that contracts in response to stimulation and relaxes when the stimulation ends thin, elongated cylinder with rounded ends and can extend the full length of the muscle Cell membranes (sarcolemma) and cytoplasm (sarcoplasm). Sarcoplasm contains many nuclei and mitochondria and contains myofibrils

Muscles / Cells Sarcolemma = muscle fiber membrane
Sarcoplasm = inner material surrounding fibers (like cytoplasm) Myofibrils = individual muscle fibers, made of myofilaments

Nucleus Sarcolemma Mitochondrion Sarcoplasm Myofibril

Myofibrils are made of ACTIN = thin filaments MYOSIN = thick filaments

Myofibrils help with muscle contraction Thick myofibrils are made of myosin and thin ones of actin Organization of filaments makes the striations I bands (light bands) are made of actin and attached to Z lines A bands (dark bands) made of myosin with thin actin filaments overlapping. H zone made of only myosin and M line is extra thick.

Myofilaments ACTIN (thin) and MYOSIN (thick)
form dark and light bands A band = dArk • thick (myosin) I band = lIght • thin (actin)

Sarcomere – segment of a myofibril that extends from one Z line to the next Z line Also in sarcoplasm is sarcoplasmic reticulum (network of membranous channels that surround and run parallel to myofibrils, functions like ER does in other cells) Transverse tubules (T-tubules) are another set of channels that extend in from fiber’s membrane and pass through the fiber. Sarcoplasmic reticulum and T-tubules activate muscle contraction when the fiber is stimulated

It is important to remember the hierarchy
fasicles Muscle cells myofilaments actin myosin

Neuromuscular Junctions
Each skeletal muscle fiber connects to a nerve cell called a motor neuron Connection between muscle fiber and motor neuron called neuromuscular junction Muscle fiber membrane forms a motor end plate at junctions Ends of motor neurons extends into muscle fiber membranes and contain large amounts of neurotransmitters When neurotransmitters are released, it stimulates a muscle contraction

How Muscles Work with the Nervous System
NEUROMUSCULAR JUNCTION - where a nerve and muscle fiber come together

Neuromuscular Junctions
Motor units are made of a motor neuron and the muscle fibers it controls. Muscle fibers usually a single motor end plate, but each motor neuron is highly branched and connects to many muscle fibers When motor neuron transmits and impulse, all muscle fibers it is connected to contract simultaneously

Motor Unit or Neuromuscular Junction
1. Neuron 2. Sarcolemma (or motor end plate) 3. Vesicle 4. Synapse 5. Mitochondria

The neurotransmitter that crosses the gap is ACETYLCHOLINE.
This is what activates the muscle. Acetylcholine is stored in vesicles

http://highered. mcgraw-hill

Skeletal Muscle Contraction
Muscle contraction involves a complex interaction of cell components and biochemicals Actual movement occurs in the myofibrils, where myosin and actin filaments slide past each other and shorten the myofibril Myofibrils shortening pulls on parts that the muscle is attached to and movement of a body part occurs

Myosin and Actin A myosin filament is made of several myosin protein molecules, each with a globular head that forms cross-bridges with actin An actin filament is two strands of actin twisted together with a strand of tropomyosin and globular protein troponin

SLIDING FILAMENT THEORY (MODEL)
The theory of how muscle contracts is the sliding filament theory. The contraction of a muscle occurs as the thin filament slide past the thick filaments. The sliding filament theory involves five different molecules and calcium ions. The five molecules are: myosin actin tropomyosin troponin ATP

Sliding Filament Handout

ANIMATION OF SLIDING FILAMENT

Animations

Energy Source -ATP is produced by CELLULAR RESPIRATION
which occurs in the mitochondria -Creatine phosphate increases regeneration of ATP * Only 25% of energy produced during cellular respiration is used in metabolic processes - the rest is in the form of HEAT. maintains body temperature.

Why might products like pro-creatine claim to increase energy?
ATP = adenosine triphosphate ADP = adenosine diphosphate

Threshold Stimulus All-or-None Response
Minimal strength required to cause a contraction Motor neuron releases enough acetylcholine to reach threshold All-or-None Response Fibers do not contract partially, they either do or don't

Motor Unit Recruitment Muscle Tone The muscle fiber + the motor neuron
The muscle fiber + the motor neuron Recruitment more and more fibers contract as the intensity of the stimulus increases Muscle Tone Sustained contraction of individual fibers, even when muscle is at rest

Hypertrophy - muscles enlarge (working out or certain disorders)
Atrophy - muscles become small and weak due to disuse

Muscle Cramp - a sustained involuntary contraction
Muscle Fatigue - muscle loses ability to contract after prolonged exercise or strain Muscle Cramp - a sustained involuntary contraction Oxygen Debt - oxygen is used to create ATP, -- not have enough oxygen causes Lactic Acid to accumulate in the muscles → Soreness

11. Origin and Insertion Origin = the immovable end of the muscle
Insertion = the movable end of the muscle The biceps brachii has two origins (or two heads).

Skeletal Muscle Actions
Part of the muscle that is attached to an immovable part is the origin Part of the muscle that is attached to a movable part at a joint is the insertion When muscles contract, the insertion is pulled toward the origin Some muscles have more than one origin or insertion Flexion and extension describe movements at a joint – flexion of the forearm at the elbow

Skeletal Muscle Actions
Skeletal muscles almost always work in groups or pairs – must do more than contract a single muscle to move a body part Muscle that provides most of the movement is the prime mover Nearby muscles may also contract. Those that assist the prime mover are synergists Muscles that can resist a prime mover’s action and cause movement in the opposite direction are antagonists

What is rigor mortis? A few hours after a person or animal dies, the joints of the body stiffen and become locked in place. This stiffening is called rigor mortis. Depending on temperature and other conditions, rigor mortis lasts approximately 72 hours. The phenomenon is caused by the skeletal muscles partially contracting. The muscles are unable to relax, so the joints become fixed in place.

What is tetanus? Tetanus causes cholinosterase to not break down the acetylcholine in the synapse. This results in a person's muscles contracting and not relaxing. A tetanus shot must be administered shortly after exposure to the bacteria. Once you develop tetanus, there is no cure.

Major Skeletal Muscles
Names of skeletal muscles very often describe the muscle May indicate the muscle’s size, shape, location, action, number of attachements, or direction of the fibers External oblique- near the outside with fibers that run in a slanted direction Biceps brachii – two points of origin and attached to the brachium (arm)

Muscles of Facial Expression
Muscles help us communicate emotions, and many are located around the eyes and mouth Muscle Origin Insertion Action Epicranius Occipital bone Skin and muscles around eye Raises eyebrow Orbicularis oculi Maxillary and frontal bones Skin around eye Closes eye Orbicularis oris Muscles near the mouth Skin of lips Closes and protrudes lips Buccinator Outer surfaces of maxilla and mandible Compresses cheeks inward Zygomaticus Zygomatic bone Raises corner of mouth Platysma Fascia in upper chest Lower border of mandible draws angle of mouth downward

Muscles of Mastication
Muscles attached to the mandible and produce chewing movements Two pairs close the lower jaw (biting) Muscle Origin Insertion Action Masseter Lower border of zygomatic arch Lateral surface of mandible Closes jaw Temporalis Temporal bone Coronoid process and lateral surface of mandible

Muscles that Move the Head
Head movements come from actions of paired muscles in the neck and upper back. Muscles flex, extend, and rotate the head Muscle Origin Insertion Action Sternocleidomastiod Anterior surface of sternum and upper surface of clavicle Mastoid process of temporal bone Pulls head to one side, pulls head toward chest, or raises sternum Splenius capitis Spinous processes of lower cervical and upper thoracic vertebrae Rotates head, bends head to one side, brings head into upright position Semispinalis capitis Processes of lower cervical and upper thoracic vertebrae Occipital bone Extendes head, bends head to one side, rotates head

Muscles that Move the Pectoral Girdle
Closely associated with the muscles that move the arm; many connect to the scapula and move the scapula upward, downward, forward, and backward Muscle Origin Insertion Action Trapezius Occipital bone and spines of cervical and thoracic vertebrae Clavicle; spine and acromion process of scapula Rotates scapula and raises arm; raises scapula; pulls scapula medially; pulls scapula and shoulder downward Rhomboideus major Spines of upper thoracic vertebrae Medial border of scapula Raises and adducts scapula Levator scapulae Transverse processes of cervical vertebrae Medial margin of scapula Elevates scapula Serratus anterior Outer surfaces of upper ribs Ventral surfaces of scapula Pulls scapula anteriorly and downward Pectoralis minor Sternal ends of upper ribs Coracoid process of scapula Pulls scapula anteriorly and downward; raises ribs

Muscles that Move the Arm
Action Coracobrachialis Flexes and adducts arm Pectoralis major Pulls arm anteriorly and across chest, rotates humerus, adducts arm Teres major Extends humerus; adducts and rotates arm medially Latissimus dorsi Extends and adducts arm and rotates humerus inwardly, pulls shoulder downward and posteriorly Supraspinatus Abducts arm Deltoid Abducts arm, extends or flexes humerus Subscapularis Rotates arm medially Infraspinatus Rotates arm laterally Teres minor

Muscles that Move the Forearm
Muscles that contract the radius or ulna to the humerus or pectoral girdle produce most of the movements. Other muscles rotate the forearm Muscle Action Biceps brachii Flexes forearm at elbow and rotates hand laterally Brachialis Flexes forearm at elbow Brachioradialis Triceps brachii Extends forearm at elbow Supinator Rotates forearm laterally Pronator teres Rotates forearm medially Pronator quadratus

Muscles that Move the Wrist, Hand, and Fingers
Originate from the distal end of the humerus, radius, and ulna Muscle Action Flexor carpi radialis Flexes and abducts wrist Flexor carpi ulnaris Flexes and adducts wrist Palmaris longus Flexes wrist Flexor digitorum profundus Flexes distal joints of fingers Extensor carpi radialis longus Extends wrist and abducts hand Extensor carpi radialis brevis Extensor carpi ulnaris Extends and adducts wrist Extensor digitorum Extends fingers

Muscles of the Abdominal Wall
Anterior and lateral walls of the abdomen are made of layers of broad, flattened muscles. Connect the rib cage and vertebral column to the pelvic girdle Linea alba (fibrous connective tissue) that extends from xiphoid process of the sternum to the symphysis pubis Contractions of the muscles help press air out during forceful exhalation, aid in movements of defecation, urination, vomiting, and childbirth

Muscles of the Abdominal Wall
Action External oblique Tenses abdominal wall and compresses abdominal contents Internal oblique Transversus abdominus Rectus abdominis Tenses abdominal wall and compresses abdominal contents; flexes vertebral column

Muscles of the Pelvic Outlet
Two muscular sheets – pelvic diaphragm (deeper) and urogenital diaphragm (superficial) – span the pelvic outlet Pelvic diaphragm form the floor of the pelvic cavity and urogenital cavity fills the space within the pubic arch Males and females have the same muscles, however some are shaped slightly differently

Muscles of the Pelvic Outlet
Action Levator ani Supports pelvic viscera and provides sphincter-like action in anal canal and vagina Superficial transversus Supports pelvic viscera Bulbospongiosus Males: assists emptying of urethra Females: constricts vagina Ischiocavernosus Assists function of bulbospongiosus

Muscles that Move the Thigh
Attached to femur and some part of the pelvic girdle; anterior muscles flex the thigh, posterior muscles extend, abduct, or rotate the thigh Muscle Action Psoas major Flexes thigh Iliacus Gluteus maximus Extends thigh Gluteus medius Abducts and rotates thigh medially Gluteus minimus Tensor fasciae latae Abducts, flexes, and rotates thigh medially Adductor longus Abducts, flexes, and rotates thigh laterally Adductor magnus Gracilis Adducts thigh, flexes and rotates lower limb medially

Muscles that Move the Leg
Connect the tibia or fibula to the femur or pelvic girdle; two groups: those that flex the knee or extend the knee Muscle Action Sartorius Flexes leg and thigh, abducts thigh, rotates thigh laterally, and rotates leg medially Hamstring Group Biceps femoris Flexes leg, extends thigh Semitendinosus Semimembranosus Quadriceps femoris group Rectus femoris Extends leg at knee Vastus lateralis Vastus medialis Vastus intermedius

Muscles that Move the Ankle, Foot, and Toes
Attach to the femur, tibia, fibula, and bones of the foot and make the movements dorsiflexion, plantar flexion, inversion, and eversion

Muscles that Move the Ankle, Foot, and Toes
Action Tibialis anterior Dorsiflexion and inversion Peroneus tertius Dorsiflexion and eversion Extensor digitorum longus Dorsiflexion and eversion of foot, extension of toes Gastrocnemius Plantar flexion of foot and flexion of leg at knee Soleus Plantar flexion of foot Flexor digitorum longus Plantar flexion and inversion of foot, and flexion of the four lateral toes Tibialis posterior Plantar flexion and inversion of foot Peroneus longus Plantar flexion and eversion of foot; also supports arch

Muscular System.

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