2or “Everything you ever wanted to know about Muscles, but were afraid to ask” !!! This is the presentation on the muscular system for Human Anatomy and Physiology I at Oklahoma City Community College. I am Dennis Anderson.
3Did you know that ?more than 50% of body weight is muscle !And muscle is made up of proteins and water
9Classification of Muscle Skeletal-found in limbsCardiac-found in heartSmooth-Found in visceraStriated, multi- nucleatedStriated, 1 nucleusNot striated, 1 nucleusvoluntaryinvoluntary
10Characteristics of Muscle Skeletal and smooth muscle are elongatedMuscle cell = muscle fiberContraction of a muscle is due to movement of microfilaments (protein fibers)All muscles share some terminologyPrefixes myo and mys refer to musclePrefix sarco refers to flesh
11Shapes of Muscles Triangular- shoulder, neck Spindle- arms, legs Flat- diaphragm, foreheadCircular- mouth, anus
12Skeletal Muscle Most are attached by tendons to bones Cells have more than one nucleus (multinucleated)Striated- have stripes, bandingVoluntary- subject to conscious controlTendons are mostly made of collagen fibersFound in the limbsProduce movement, maintain posture, generate heat, stabilize joints
13Structure of skeletal muscle Each cell (fibre) is long and cylindricalMuscle fibres are multi-nucleatedTypically 50-60mm in diameter, and up to 10cm longThe contractile elements of skeletal muscle cells are myofibrils
14Skeletal muscle - Summary Voluntary movement of skeletal partsSpans joints and attached to skeletonMulti-nucleated, striated, cylindrical fibres
15Smooth Muscle No striations Spindle shaped Single nucleus Involuntary- no conscious controlFound mainly in the walls of hollow organs
16Smooth muscle Lines walls of viscera Found in longitudinal or circular arrangementAlternate contraction of circular & longitudinal muscle in the intestine leads to peristalsis
17Structure of smooth muscle Spindle shaped uni-nucleated cellsStriations not observedActin and myosin filaments are present( protein fibers)
18Smooth muscle - Summary Found in walls of hollow internal organsInvoluntary movement of internal organsElongated, spindle shaped fibre with single nucleus
19Cardiac Muscle Striations Branching cells Involuntary Found only in the heartUsually has a single nucleus, but can have more than one
20Cardiac muscle Main muscle of heart Pumping mass of heart Critical in humansHeart muscle cells behave as one unitHeart always contracts to it’s full extent
21Structure of cardiac muscle Cardiac muscle cells (fibres) are short, branched and interconnectedCells are striated & usually have 1 nucleusAdjacent cardiac cells are joined via electrical synapses (gap junctions)These gap junctions appear as dark lines and are called intercalated discs
22Cardiac muscle - Summary Found in the heartInvoluntary rhythmic contractionBranched, striated fibre with single nucleus and intercalated discs
23Muscle Control Type of muscle Nervous control Type of control Example SkeletalControlled by CNSVoluntaryLifting a glassSkeletalCardiacRegulated by ANSInvoluntaryHeart beatingSmoothControlled by ANSInvoluntaryPeristalsis
24Types of Responses Twitch- Tetanus A single brief contraction Not a normal muscle functionTetanusOne contraction immediately followed by anotherMuscle never completely returns to a relaxed stateEffects are compounded
25Where Does the Energy Come From? Energy is stored in the muscles in the form of ATPATP comes from the breakdown of glucose during Cellular RespirationThis all happens in the Mitochondria of the cellWhen a muscle is fatigued (tired) it is unable to contract because of lack of Oxygen.
26Muscle FatigueIf muscle is continued to be stimulated, the strength of the contraction decreases until eventually it will no longer contract!!When oxygen supplies of muscle run low, the cells switch to anaerobic respiration, but at a cost.This produces lactic acid that makes you sore!!!
27Muscle FatigueOxygen Debt- continued increased metabolism that must occur in cell to remove excess lactic acid that accumulates during prolonged exercise.Labored breathing after exercise is needed to “pay the debt”
28How are Muscles Attached to Bone? Origin-attachment to a movable boneInsertion- attachment to an immovable boneMuscles are always attached to at least 2 pointsMovement is attained due to a muscle moving an attached bone
29Exercise and MusclesIsotonic- ( most normal exercise) produces movement. Muscle shortens and lengthens. Tension on muscle stays the same.Isometric- tension in muscles increases, no movement occurs (pushing one hand against the other)
30Effects of Exercise on Skeletal muscle Changes correspond to amount of work they do. Prolonged inactivity- muscle mass shrinks--- called disuse atrophy. Exercise- increase in muscle size called hypertrophy.Can be enhanced by strength training- number of fibers stays same but number of myofilaments increase causing increase in mass of muscle
31Exercise and muscle cont. Aerobic or endurance training- no muscle hypertrophy but get better blood flow, with increased oxygen and glucose delivery to muscle. Increase in mitochondria----- more production of ATP
32Functions of skeletal muscle MovementPosture (muscle tone)- from “tonic contractions”. Hold muscles in position but do not move any body partsHeat production- reverse hypothermia
33MovementMuscles pull on bones. Insertion bone moves and origin bone stays put.Muscle responsible for producing any particular movement is called the prime mover. Other muscle that help in producing movement are called synergists.As prime movers and synergists contract, other muscles called antagonists relax
34Motor UnitBefore skeletal muscle can contract, it must be stimulated by nerve impulse(the nerve fiber is a motor neuron)Point of contact between nerve ending and muscle fiber is called the neuromuscular junctionA single motor neuron and the muscle cells it innervates is called a motor unit
35Muscle StimulusMuscle fiber will not contract until a stimulus reaches a certain level of intensity. This minimal level required for a contraction is called the threshold stimulusWhen muscle cell is subjected to threshold, it contracts completely. Called “all or none” response.Number of fibers involved changes with load
36Muscle Attachments Insertion Origin Muscles attach in at least two places in the body. *The origin is the attachment that moves the least. *The insertion is the attachment that moves the most. This diagram illustrates the origin and insertion of one of the neck muscles. Note the origin is on the clavicle and sternum. The insertion is on the skull. When the muscle contracts it will shorten the distance between the origin and insertion. The head will move when this muscle contracts. Remember the insertion is the end of the muscle that moves the most. Since the head moves the attachment on the head is called the insertion. The origin is generally on a larger body part will move the least. The chest does not move when this muscle contract. The bones in the chest are therefore the origin.
37Types of Musculo-Skeletal Movement FlexionYou will need to know the action or movement performed for each of the muscles we study. The first type of movement is called flexion. Note the lower leg is being flexed in this diagram. During flexion the angle of joint is decreased. As the knee is flexed, the angle between the lower leg and the thigh is decreased. Flexion of the upper arm is also illustrated in this diagram. Here the angle between the arm and the frontal plane is decreased.
38ExtensionExtension is the opposite of flexion. In extension the angle of a joint is increased. Extension of the lower leg causes an increased angle between the lower leg and the thigh.
39HyperextensionFlexion and extension also apply to the neck. When a joint is extended past the anatomical position the movement is called hyperextension.
40Abduction, Adduction & Circumduction Abduction refers to moving away from the median plane of the body. Adduction is the opposite movement to abduction. It is moving toward the medial plane. Circumduction refers to inscribing a circle while moving a limb.
41RotationRotation is turning a bone on its own axis. Moving the head back and forth to indicate “no” is an example of rotation. Note the difference between medial and lateral rotation. In lateral rotation the limb is rotated the lateral side of the body. Medial rotation rotates the limb toward the medial side of the body.
42More Types of Movement…… Inversion- turn sole of foot mediallyEversion- turn sole of foot laterallyPronation- palm facing downSupination- palm facing upOpposition- thumb touches tips of fingers on the same hand
43The Skeletal Muscles There are about 650 muscles in the human body The Skeletal Muscles There are about 650 muscles in the human body. They enable us to move, maintain posture and generate heat. In this section we will only study a sample of the major muscles.There are about 650 muscles in the human body. They enable us to move, maintain posture and generate heat. In this unit will only study a sample of the major muscles.
44Sternocleidomastoideus Flexes and Rotates HeadThe first muscle we will learn is the sternocleidomastoideus. It is sometime called the sternocleitomastoid. It is the same neck muscle shown on the previous slide. * This muscle has two origins. The first origin is on the sternum manubrium. The second origin is on the clavicle. *The insertion is on the mastoid process of the skull. *Contraction of both sternocleidomastoideus muscles will flex the head. If just on of the muscles contracts, the head will rotate.
45Masseter Elevate Mandible The masseter is one of major chewing muscles. *The origin of the masseter is on the zygomatic arch. *The insertion is on the mandible. *Contraction of the masseter will elevate the jaw.
46Elevate & Retract Mandible TemporalisElevate & Retract MandibleThe temporalis is another chewing muscle. Note how it attaches on the side of skull. *It also elevates the mandible. Also note I did not give the origin and insertion of this muscle. You will only need to know the origin and insertion of a few of the muscles in this unit.
47Extend Head, Adduct, Elevate or Depress Scapula TrapeziusExtend Head, Adduct, Elevate or Depress ScapulaThe trapezius is a large muscle in the upper back. It attaches to the skull, shoulder and vertebrae of the back. *When this muscle contracts it will cause the head to extend. It will also move the scapula. The direction the scapula moves depends on which part of the trapezius contracts. The trapezius may adduct elevate or depress the scapula.
48Extend, Adduct & Rotate Arm Medially Latissimus DorsiExtend, Adduct & Rotate Arm MediallyThe latissimus dorsi is a large muscle in the back. It is often referred to as a lat. *It has origins on the vertebrae, ilium ribs and scapula. *The insertion is on the humerus. When it contracts it moves the humerus. *It can extend, adduct and rotate the arm medially. This is the main muscle used in movement such as pounding a nail with a hammer.
49Abduct, Flex & Extend Arm DeltoidAbduct, Flex & Extend ArmThe deltoid covers the shoulder and has the shape of a delta. *It has origins on the scapula and clavicle. *The deltoid inserts on the deltoid tuberosity of the humerus. *Contraction of the deltoid will adduct the arm. If only the anterior fibers of the muscle contract it will flex the arm. Contraction of the posterior fibers will extend the arm.
50Flexes, adducts & rotates arm medially Pectoralis MajorFlexes, adducts & rotates arm mediallyThe pectoralis major is a large muscle in the pectoral region of the body. *It has origins on the clavicle and sternum. *The insertion is on the greater tubercle of the humerus. *Contraction of the pectoralis major will flex the arm. It will also adduct and rotate the arm medially. The pectoralis major is used in movements such a climbing, throwing and doing pushups.
51Biceps Brachii Flexes Elbow Joint The biceps brachii is located on the anterior side of the upper arm. It is often just called the biceps. There is a biceps femoris in the leg we will study shortly. *The biceps has two origins. One origin is on the corocoid process and the other on the Glenoid cavity of the scapula. The “bi” in biceps refers to the two origins. *It inserts on the radial tuberosity. *Contraction of the biceps will cause flexing at the elbow joint.
52Triceps Brachii Extend Elbow Joint The triceps is on the back of the upper arm. *It has three origins. Two origins are on the back of the humerus and one on the scapula. *The triceps inserts on the olecranon. *Movement of the triceps will extend the elbow joint.
53Rectus Abdominus Flexes Abdomen Rectus abdominus is a long muscle in the abdomen. *The muscle originates on the pubis. *It inserts on the xiphoid process of the sternum and also on cartilage of the ribs. *When rectus abdominus contracts it will flex the abdomen.
54External Oblique Compress Abdomen Another muscle in the abdomen is the external oblique. It has muscle fibers that run in an oblique direction across the abdomen. *Contraction of the external oblique will compress the abdomen.
55External Intercostals Elevate ribsThere are two groups of muscles that run between the ribs. The first are the external intercostals. *They will elevate the ribs.
56Internal Intercostals Depress ribsThe internal intercostals are also located between the ribs. *They will depress the ribs.
57Diaphragm Inspiration This is an inferior view of the diaphragm. This muscle separates the abdominal cavity from the thoracic cavity. *When it contracts it will cause inspiration.
58Forearm Muscles Flexor carpi—Flexes wrist Extensor carpi—Extends wrist Flexor digitorum—Flexes fingersExtensor digitorum—Extends fingersPronator—PronatesSupinator—SupinatesThere are several muscles in the forearm that have important movements. *The flexor carpi are used to flex the wrist. *Extensor carpi extend the wrist. *Flexor digitorum flexes the fingers. *Extensor digitorum extends the fingers. *The pronator pronates. *A supinator muscle will supinate.
59Extends & Rotates Thigh Laterally Gluteus MaximusExtends & Rotates Thigh LaterallyThe large muscle on the posterior side of the body at the top of each leg is the gluteus maximus. *The gluteus maximus originates on the ilium, sacrum and coccyx. *It inserts on the gluteal tuberosity of the femur. *This muscle will extend and rotate the thigh laterally.
60Flexes Thigh, Extends Lower Leg Rectus FemorisFlexes Thigh, Extends Lower LegRectus femoris is located on the anterior side of the thigh. *It originates on the ilium. *The insertion is on the patella and the tibial tuberosity. *When rectus femoris contracts it will flex the thigh and extend the lower leg.
61Adducts and Flexes Thigh GracilisAdducts and Flexes ThighThe gracilis is on the medial side of the thigh. *It adducts and flexes the thigh.
62Flexes Thigh, & Rotates Thigh Laterally SartoriusFlexes Thigh, & Rotates Thigh LaterallySartorius is a long, strap like muscle. *It originates on the anterior superior iliac spine of the ilium. *The insertion is on the medial side of the tibia. * Contraction of the sartorius flexes the thigh and rotates the thigh laterally. This is the muscle used when crossing the legs to sit on the floor.
63Extends Thigh & Flexes Lower Leg Biceps FemorisExtends Thigh & Flexes Lower LegBiceps femoris is one of the hamstring muscles. *The origin is on the ischial tuberosity. *Biceps femoris inserts on the tibia and fibula. This muscle extends the thigh and flexes the lower leg.
64Plantar Flexes Foot & Flex Lower Leg GastrocnemiusPlantar Flexes Foot & Flex Lower LegGastrocnemius is commonly called the calf muscle. *It originates on the distal end of the femur. *The insertion is on the calcaneus bone of the foot. *It will cause plantar flexion of the foot and also flex the lower leg.
65Dorsiflexes and Inverts Foot Tibialis AnteriorDorsiflexes and Inverts FootTibialis anterior is located on the anterior side of the tibia. *It will dorsiflex and invert the foot.