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Muscle Lecture-BIO 006 Handout1 The Muscular System (rev 3-10) Muscular tissue enables the body and its parts to move Movement is caused by ability of.

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Presentation on theme: "Muscle Lecture-BIO 006 Handout1 The Muscular System (rev 3-10) Muscular tissue enables the body and its parts to move Movement is caused by ability of."— Presentation transcript:

1 Muscle Lecture-BIO 006 Handout1 The Muscular System (rev 3-10) Muscular tissue enables the body and its parts to move Movement is caused by ability of muscle cells (called fibers) to shorten or contract –Function of muscle tissue is to contract (or shorten) Muscle cells use energy to produce movement We have 3 types of muscle tissue in our bodies

2 Muscle Lecture-BIO 006 Handout2 Skeletal muscle —also called striated or voluntary muscle –This type muscle has stripes or striations –Contractions can be voluntarily controlled

3 Muscle Lecture-BIO 006 Handout3 Cardiac muscle —composes bulk of heart –Striated muscle; involuntary (contractions not under voluntary control) –Characterized by unique dark bands called intercalated disks –Cells branch frequently –Interconnected nature of cardiac muscle cells allows heart to contract efficiently as a unit

4 Muscle Lecture-BIO 006 Handout4 Smooth or visceral muscle –Nonstriated, involuntary muscle –Lacks cross stripes or striations when seen under a microscope; appears smooth –Found in walls of hollow visceral structures such as digestive tract, blood vessels, and ureters –Contractions not under voluntary control; movement caused by contractions is involuntary

5 Muscle Lecture-BIO 006 Handout5 Structure of Skeletal Muscle Each skeletal muscle is an organ composed of skeletal muscle cells and connective tissue –Most skeletal muscles extend from one bone across a joint to another bone Parts of a skeletal muscle –Origin—attachment to the bone that remains relatively stationary or fixed when movement at the joint occurs –Insertion—point of attachment to the bone that moves when a muscle contracts –Body or Belly—main part of the muscle

6 Muscle Lecture-BIO 006 Handout6 –Muscles attach to the bone by tendons which are made of strong fibrous connective tissue –Some tendons are enclosed in synovial- lined tubes, called tendon sheaths, and are lubricated by synovial fluid --Bursae—small synovial-lined sacs containing a small amount of synovial fluid; located between some tendons and underlying bones –Both tendon sheaths and bursae make it easier for a tendon to slide over bone

7 Muscle Lecture-BIO 006 Handout7 Microscopic structure Specialized contractile cells called fibers are grouped into bundles –Each skeletal muscle fiber contains thick myofilaments (formed from the protein myosin) and thin myofilaments (formed from the protein actin) –These myofilaments make the striations or stripes we can see in skeletal muscle fibers –The basic functional (contractile) unit of the muscle cell is called a sarcomere. Sarcomeres are separated from each other by dark bands called Z lines

8 Muscle Lecture-BIO 006 Handout8 Sliding filament model explains mechanism of contraction –Thick and thin myofilaments slide toward each other as a muscle contracts and shorten the muscle. This is called the sliding filament model. Contraction requires calcium and ATP Functions of Skeletal Muscle: 1.Movement 2.Posture or muscle tone 3.Heat production

9 Muscle Lecture-BIO 006 Handout9 Movement –Muscles produce movement; as a muscle contracts, it pulls the insertion bone closer to the origin bone –Movement occurs at the joint between the origin and the insertion

10 Muscle Lecture-BIO 006 Handout10 –Groups of muscles usually contract to produce a single movement Prime mover —muscle whose contraction is mainly responsible for producing a movement Synergist —muscle whose contractions help the prime mover produce a movement Antagonist —muscle whose actions oppose the action of a prime mover in a movement

11 Muscle Lecture-BIO 006 Handout11 Types of Movements Produced by Skeletal Muscle Contractions Flexion—movement that decreases the angle between two bones at their joint: bending Extension—movement that increases the angle between two bones at their joint: straightening Abduction--movement of a part away from the midline of the body Adduction--movement of a part toward the midline of the body Rotation—movement around a longitudinal axis

12 Muscle Lecture-BIO 006 Handout12 Supination--hand position with the palm turned to the anterior position Pronation—hand position with the palm turned to the posterior position Dorsiflexion--elevation of the dorsum or top of the foot and Plantar flexion--the bottom of the foot is directed downward

13 Muscle Lecture-BIO 006 Handout13 Posture –A specialized type of muscle contraction, called tonic contraction, enables us to maintain body position In a tonic contraction, only a few of a muscle’s fibers shorten at one time Tonic contractions produce no movement of body parts but DO hold muscles in position –Tonic contractions maintain muscle tone called posture

14 Muscle Lecture-BIO 006 Handout14 Heat production –Survival depends on the body’s ability to maintain a constant body temperature Fever—an elevated body temperature; often a sign of illness Hypothermia—a reduced body temperature –Contraction of muscle fibers produces most of the heat required to maintain normal body temperature Energy for muscle contraction is obtained from ATP. Some of the energy is lost as heat and this is what maintains our body temperature

15 Muscle Lecture-BIO 006 Handout15 Fatigue Causes reduced strength of muscle contraction due to lack of sufficient rest Caused by repeated muscle stimulation Repeated muscular contraction uses up the cellular ATP store and exceeds the ability of the blood supply to replenish oxygen and nutrients

16 Muscle Lecture-BIO 006 Handout16 Contraction in the absence of adequate oxygen produces lactic acid, which contributes to muscle soreness Oxygen debt —term used to describe the metabolic effort to remove the excess lactic acid that may accumulate during prolonged periods of exercise; the body is attempting to return the cells’ energy and oxygen reserves to pre-exercise levels Heavy breathing after exercises helps to return level of oxygen in blood to normal levels

17 Muscle Lecture-BIO 006 Handout17 Motor Unit Stimulation of a muscle by a nerve impulse is required before a muscle can produce movement A motor neuron is the nerve that transmits an impulse to a muscle, causing contraction A neuromuscular junction is the specialized point of contact between a nerve ending and the muscle fiber it innervates A motor unit is the combination of a motor neuron with the muscle cell or cells it innervates

18 Muscle Lecture-BIO 006 Handout18 Muscle Stimulus A muscle will contract only if the stimulus reaches a certain level of intensity –A threshold stimulus is the minimal level of stimulation required to cause a muscle fiber to contract Once stimulated by a threshold stimulus, a muscle fiber will contract completely; this is called an all or none response

19 Muscle Lecture-BIO 006 Handout19 Different muscle fibers in a muscle are controlled by different motor units having different threshold-stimulus levels –Although individual muscle fibers always respond all or none to a threshold stimulus, the muscle as a whole does not –Different motor units responding to different threshold stimuli permit a muscle as a whole to execute contractions of graded force

20 Muscle Lecture-BIO 006 Handout20 Types of Skeletal Muscle Contraction Isotonic contractions  Contraction of a muscle that produces movement at a joint  During isotonic contractions, the muscle changes length, causing the insertion end of the muscle to move relative to the point of origin  Most types of body movements such as walking and running are caused by isotonic contractions

21 Muscle Lecture-BIO 006 Handout21 Types of Skeletal Muscle Contraction Isometric contractions  Isometric contractions are muscle contractions that do not produce movement  Although no movement occurs, tension within the muscle increases

22 Muscle Lecture-BIO 006 Handout22 Selected Skeletal Muscle Groups Muscles of the head and neck  Facial muscles  Orbicularis oculi—closes your eye  Orbicularis oris—puckers your lips (kissing muscle)  Zygomaticus—raises the corners of the mouth (smiling muscle)  Temporalis—chewing muscle; closes jaw  Masseter—chewing muscle; closes jaw  Neck and Shoulder muscles  Sternocleidomastoid—flexes head  Trapezius—elevates shoulders and extends head

23 Muscle Lecture-BIO 006 Handout23 Muscles that move the upper extremities  Pectoralis major—flexes upper arm; hugging muscle  Latissimus dorsi—extends upper arm  Deltoid—abducts upper arm  Biceps brachii—flexes forearm  Triceps brachii—extends forearm

24 Muscle Lecture-BIO 006 Handout24 Muscles of the trunk  Abdominal muscles  Rectus abdominis—flexes trunk Respiratory muscles  Intercostal muscles  Diaphragm

25 Muscle Lecture-BIO 006 Handout25 Muscles that move the lower extremities  Iliopsoas—flexes thigh  Gluteus maximus—extends thigh  Hamstring muscles—flex lower leg  Semimembranosus  Semitendinosus  Biceps femoris

26 Muscle Lecture-BIO 006 Handout26 Muscles that move the lower extremities  Quadriceps femoris group—extend lower leg  Rectus femoris  3 Vastus muscles  Tibialis anterior—dorsiflexes foot  Gastrocnemius—plantar flexes foot


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