SKELETAL MUSCLE CHARACTERISTICS

Transcription

1 THE MUSCULAR SYSTEM

2 SKELETAL MUSCLE CHARACTERISTICS Most are attached by tendons to bones Cells are multinucleate Striated have visible banding Voluntary subject to conscious control Cells are surrounded and bundled by connective tissue = great force, but tires easily

3 SMOOTH MUSCLE CHARACTERISTICS Has no striations Spindle-shaped cells Single nucleus Involuntary no conscious control Found mainly in the walls of hollow organs Slow, sustained and tireless

4 CARDIAC MUSCLE CHARACTERISTICS Has striations Usually has a single nucleus Joined to another muscle cell at an intercalated disc Involuntary Found only in the heart Steady pace!

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

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

7 CONNECTIVE TISSUE COVERINGS 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.

8 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

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

10 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)

11 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

12 NEUROMUSCULAR JUNCTION 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.

13 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.

14 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.

15 MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

16 MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

17 MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

18 MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

19 MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

20 MOLECULAR EVENTS OF THE CONTRACTION PROCESS Figure 7-5

21 MUSCLE GROWTH

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

23 NUMBER OF MUSCLE FIBERS ACTIVATED Muscle tone The normal tension (partial contraction) 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

24 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.

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