May 12, Three Types of Muscle

Transcription

1 Muscular System Three Types of Muscle Smooth Muscle Involuntary muscle Makes up the walls of the hollow body organs, blood vessels and respiratory pathways Responsible for Cardiac Muscle muscle Makes up the heart's wall Creates the pulsing action of the organ Cardiac muscle cells: - one nucleus per cell - contain many - specialized membranes between the cells that allows for electrical impulses to travel rapidly - striated Smooth Muscle cells: ***By the time you reach age 70, your heart has contracted on average 2.5 billion times Skeletal Muscle muscle Muscle that is attached to and produces movement at the joints (except for facial and abdominal skeletal muscles) Helps to maintain Helps to generate Skeletal Muscle cells: Structure of a Muscle Individual muscle fibers are arranged in bundles ( Fascicles are held together by What's found in the connective tissue: Endomysium: layer that surrounds the Perimysium: layer around each Epimysium: tough connective tissue sheath that forms the deep **All of these supporting tissues come together to form the

2 Muscle composed of fasicles composed of myofibrils muscle epimysium sarcomere composed of microfilaments muscle fiber myofibrils actin individual types myosin Muscle Terms How do skeletal muscles move? Nerve (motor) impulses stimulate skeletal muscle fibers Motor unit: single neuron and all the muscle fibers it stimulates Neuromuscular junction: point at which a nerve cell contracts a muscle Acetylcholine: involved with muscle contraction What happens at the neuromuscular junction? Acetylcholine is stored in in the nerve fiber's endings Acetylcholine is released and crosses the to attach to receptors on the muscle cell membrane Muscle becomes stimulated, generating an How a muscle contracts Contractility: muscle fiber's capacity to undergo and change its shape Each skeletal muscle fiber ( ) contains 2 filaments - : pearl-like structure, thin and light - : thick and dark **Alternating actin and myosin give skeletal muscle its appearance

3 Summary of how muscles contract Sliding Filament Theory How do muscle cells shorten? Muscles need a lot of and a lot of in order to contract ions help to change the shape of some of the proteins so that the heads can interact with Tropomyosin and troponin: 2 proteins that wrap around actin and prevent myosin from interacting with the actin at rest Nerve impulse from CNS sends a signal down the neurons Acetylcholine is released at the neuromuscular junction and binds to the receptors on the muscle fiber Action potential travels to the SR causing a release of calcium ions into the cytoplasm Calcium binds to troponin and tropomyosin so that binding sites on actin are exposed Myosin heads attach to actin pulling the actin filaments together within the sarcomeres ATP then needed in order to detach the myosin heads and move them back to position Muscle relaxes and calcium pumped back into the SR for next muscle contraction Sarcoplasmic reticulum (SR): the endoplasmic reticulum of muscle cells where is stored during the resting state. Sarcomere Shortening (499.0K) Rigor mortis ATP is needed in order for myosin to detach from actin Dying muscle cells deplete the last of its ATP Rigor mortis ends when lysosomes release enzymes when they rupture and break myosin-actin bonds hours after death rigor mortis occurs - After hours it resolves Energy Sources for Muscle Contraction Myoglobin: stores addition Glycogen: stores additional Creatine phosphate: stores Types of Muscle Contractions Muscle tone: steady low level contracted state which helps stabilize joints and maintain good muscle health Muscle tension - mechanical force a muscle exerts on an object such as a bone Isometric contraction - muscle develops tension but does not shorten ex: you hold a glass of water Isotonic contraction - muscle shortens and moves load ex: lifting weights Muscle Twitch - when a motor unit is stimulated by an electrical impulse - how long it lasts depends on the load - if motor unit is stimulated again before first twitch i completed the strength of contraction increases Skeletal Muscles of the body Human body has approximately skeletal muscles Body part is moved by a group of muscles working together Prime mover- muscle that does the most work ex: Antagonist: muscle that produces an movement to that of the All or None Principle - muscle either contracts fully or not at all Tetany - how are muscles operate normally

4 Muscles of the Head Naming muscles 1. Size Facial expression 1. Frontalis2. Orbicularis oculi- causes "crow feet" 2. Shape 3. Oricularis oris - 3. Direction of fibers 4.Buccinator - located in - allows us to blow out air or whistle - helps hold food in contact with teeth during chewing - allows babies to suck 4. Location 5. Attachment 6. Number of attachments 7. Action 5. Levator anguli orris and Levator labii superioris- lifts corners of the mouth - allows us to smile 6. Depressor anguli oris and Depressor labii oris- pulls down edges of mouth - allows us to pout or frown Muscles for chewing (mastication) Masseter -prime movers for elevating mandible Temporalis- they work synergistically Muscles of the Neck hyoid bone is important for function of swallowing moved by the suprahyoid and infrahyoid muscles movement of hyoid helps close flap over epiglottis Muscles that move the head Muscles of Trunk Sternocleidomastoid - allows for flexing of head when both contract - allows turning of head to the side when only one contracts External and Internal intercostal muscles- movement of rib cage Trapezius- (triangle)- moves scapula Diaphragm- assists inhalation vp=1

5 Muscles of the Shoulder Muscles of the Abdominal Wall Obliques - aid trunk rotation and lateral flexion Deltoid - triangular muscle that covers the shoulder causing a bulge in the arm where it meets the shoulder Pectoralis major - large muscle of the Latissimus dorsi - large triangular muscle in back - important for Rotator cuff- made up of three muscles whose tendons help form a cuff over the proximal humerus Muscles of the Arm Biceps brachii - flexor muscle that bulges when you bend your arm - also allows supination of the hand such as when you turn a doorknob Muscles of the Thigh ILiopsoas - prime mover for flexing thigh and also trunk when we bow Triceps brachii - only muscle of posterior arm Gluteus maximus- largest muscle in the body which covers large part of the buttocks - prime mover of thigh extension Flexor and extensor carpi - flexes and extends wrists and hands Gluteus medius - the thigh Flexor and extensor digitorium- flexes and extends wrist and fingers Adductor group - the thigh Muscles that Move the Leg Quadriceps femoris group- primary extensors of the leg Sartorius - rotates the thigh laterally - allows you to sit cross-legged Hamstring group - flex and rotate the leg - have strong tendons Muscles that Move the Ankle and Foot Gastrocnemius - forms large part of the calf - powerful plantar flexor Tibialis anterior - allows for dorsiflexion and inversion of the foot Flexor and extensor digitorium longus - flex and extend the toes

6 Diseases Disorders and Diseases of Muscular System Spasm - sudden and muscular contraction -when it occurs in muscle it can be due to in muscle after -colic is a spasm of smooth muscle Twitch- contraction of muscles just under the skin - can be caused by fatigue, stress, electrolyte imbalance Strain - caused by of Sprain - tearing of Atrophy - wasting or decrease in size of muscle when it cannot be used Muscular dystrophy - a group of disorders that causes degenerative and weakening of muscles Myasthenia gravis - autoimmune disorder - muscle weakness that particularly affects the muscles of the eyelids, face and neck - muscle contraction is impaired because antibodies destroy acetylcholine receptors ALS - loss of motor neurons that in turn leads to loss of muscle activity (also known as Amyotrophic Lateral Sclerosis or Lou Gehrig's disease) Fibromyalgia -chronic condition that causes pain, tenderness and stiffness of muscles - most commonly found in women Botox Tetanus Acetylcholine stays in the synapse of the neuromusclar junction Person's muscles contract without relaxing Tetanus shot must be administered shortly after exposure to the bacteria Botox is a brand name for a toxin produced by the bacterium Clostridium botulinum. Botox blocks the signals from the nerves to the muscles by attaching to the nerve endings preventing the release of acetylcholine The injected muscle can't contract which makes wrinkles relax and soften Clostridium botulinum also produces neurotoxin that causes botulism: form of a food poisoning Disorders of Associated Structures Anterior cruciate ligament(acl) one of the four major ligaments of the knee usually a sports related injury occurs more often in women Bursitis- inflammation of bursa which can be found all over body -bursa are fluid filled sacs which prevent friction between muscle, tendons and bone - can be caused by repetitive movement or excessive pressure Shin splints- pain over the front of the tibia - can sometimes be caused by medial tibial stress syndrome - this condition results from increased duration of physical training

7 Achilles tendon - fibrous tissue that attaches heel to lower calf - thickest and strongest tendon in the body - each achilles tendon is subject to person's entire body weight with each step Tendonitis- inflammation of tendons Myostatin mutation