THE MUSCULAR SYSTEM

 To understand the structure of muscle.  To explain the components and significance of the sarcomere.  To identify the parts of the neuromuscular junction  To explain how muscle contracts. OBJECTIVES

MUSCULAR MOVEMENT  skeletal muscles come in antagonistic pairs  flexor vs. extensor  They contract (shorten) when activated  Tendons (t=two!)  connect bone to muscle  ligaments  connect bone to bone

 Composed of skeletal muscle tissue, nervous tissue, blood, and connective tissues. SKELETAL MUSCLE

 Fascia: layers of fibrous connective tissue that separate an individual muscle from adjacent muscles.  Epimysium: tissue closely surrounding muscle  Perimysium: separates muscle tissue into small compartments.  Fascicles: bundles of skeletal muscle fibers  Endomysium: surrounds each fiber within a fascicle. CONNECTIVE TISSUE COVERINGS

STRUCTURE OF STRIATED SKELETAL MUSCLE  Muscle Fiber  muscle cell  divided into sections = sarcomeres  Sarcomere  functional unit of muscle contraction  alternating bands of thin (actin) & thick (myosin) protein filaments

THICK & THIN FILAMENTS  Myosin tails aligned together & heads pointed away from center of sarcomere

THIN FILAMENTS: ACTIN  Complex of proteins  braid of actin molecules & tropomyosin fibers  tropomyosin fibers secured with troponin molecules which block the spot where the myosin fiber will attach. (this must be moved in order for the muscle to contract)

SLIDING FILAMENT THEORY  Sliding filament theory  Thin filaments of sarcomere slide toward M line after the myosin crossbridges form  The width of the A band remains the same  Z lines move closer together

WHAT AM I?

 Place where a motor neuron meets a muscle cell  Action potential travels down neuron, stimulates release of acetylcholine from vesicles, received by receptors on muscle cell, action potential is propogated and stimulates contraction. NEUROMUSCULAR JUNCTION

STEPS OF CONTRACTION 1. A. Upon stimulation, Ca 2+ binds to receptor on troponin molecule. B. The troponin–tropomyosin complex changes, exposing the active site of actin. 2. The myosin head attaches to actin, forming a cross-bridge.

STEPS OF CONTRACTION 3. The attached myosin head bends/pivots towards the sarcomere, and ADP and P are released. 4. The cross- bridges detach when the myosin head binds another ATP molecule. 5. The detached myosin head is reactivated as ATPase splits the ATP and captures the released energy.

MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

Put it all together… 1 ATP

DO NOW  Read the article and answer the questions.

OBJECTIVES  To understand how muscles “grow” and explain the benefits of resistance workouts.  To identify the parts of a myogram and explain the different graphs used to depict muscle contraction.  To build on prior knowledge from Biology to explain muscular fatigue.

TENSION PRODUCTION  The all-or-none principle  As a whole, a muscle fiber either contracts completely or does not contract at all

NUMBER OF MUSCLE FIBERS ACTIVATED  Recruitment (multiple motor unit summation)  In a whole muscle or group of muscles, increasing tension is produced by slowly increasing the size or number of motor units stimulated

MOTOR UNITS Figure 7-8

NUMBER OF MUSCLE FIBERS ACTIVATED  Muscle tone  The normal tension and firmness of a muscle at rest  Muscle units actively maintain body position, without motion  Increasing muscle tone increases metabolic energy used, even at rest

MUSCLE CONTRACTION  A muscle fiber will contract after threshold stimulus has been reached.  Once stimulated, the entire fiber completely contracts which is called the all-or-none response.  *the extent of shortening depends on resistance.

MYOGRAM  Twitch= single muscle contraction  Latent period: time between stimulation and response  Period of contraction: muscle is contracted  Relaxation: fiber returns to former length

TYPES OF GRAPHS  Twitch- full contraction  Summation- force of each twitch combines  Incomplete tetanus- minimal amt. of relaxation after each stimulus  Complete tetanus- no relaxation, continuous calcium ion deposit

ATP AND MUSCLE CONTRACTION  Sustained muscle contraction uses a lot of ATP energy  Muscles store enough energy to start contraction  Muscle fibers must manufacture more ATP as needed

MUSCLE FATIGUE  Cells undergo both aerobic and anaerobic respiration to supply ample atp (lactic acid fermentation)  Lactic acid creates an oxygen debt because the liver cells must now use oxygen to break down the lactic acid (can take several hours)  Lactic acid lowers the ph, which diminishes the muscle fibers response to stimulation  More exercise = more glycolytic enzymes = increased capacity for glycolysis= increased capacity for aerobic respiration!! … start working out

HYPERTROPHY VS. ATROPHY  Hypertrophy- muscles respond to exercise and enlarge  Slow twitch fibers activated by low intensity exercise such as swimming or running, develop more mitochondria and capillaries, prolonging fatigue  Fast twitch fibers activated by weight lifting can produce new myofilaments & enlarge the muscle (they are still fatigable)  Atrophy- when regular exercise stops, capillary networks shrink, mitochondria decrease, actin & myosin decrease, and muscle shrinks.

TETANUS  Caused by Clostridium bacteria present in soil  Bacteria produces a neurotoxin which blocks the release of inhibitory neurotransmitters.

ISOMETRIC VS. ISOTONIC  Isometric- no change in muscle length  Isotonic- muscle length changes

MUSCLES OF THE FACE