1. Muscular System

2. Anatomy of a Muscle

3. Major Functions of the Muscular System
Produce Movement
Heat production
Maintain Posture

4. Skeletal Muscle-Voluntary Muscle
Threadlike cells that have multiple nuclei
Many cross striations (stripes)
Attached to bones to produce body movement or facial expressions
Smooth Muscle-Involuntary Muscle Elongated narrow cells with single nucleus
No cross striations
Found in the walls of hollow organs to propel food through them by peristalsis
Cardiac Muscle-Also involuntary
Found only in the heart
Branching cells joined by intercalated disks with gap junctions that allow ions to pass freely from cell to cell=rapid conduction of electrical impulse.

5. The functional unit of a muscle

6. Striated Muscle Multinucleated Striations are visible
Caused by the sarcomeres.

7. Terms Sarcomere, Sarcolemma-cell membrane Sarcoplasmic Reticulum- like
an endoplasmic reticulum of
any cell.

10. Physiology of Muscles contraction What Happens and Why?
1. A nerve impulse reaches the end of a motor neuron – releases acetylcholine
Acetylcholine diffuses across the gap of the neuromuscular junction and binds to receptors on the motor endplate of the muscle fiber.
Impulse travels along the sarcolemma, to the T tubules to sacs of the SR.

11. THEN What HAPPENS?
Ca++ is released from the SR into the sarcoplasm, where it binds to troponin mlcs in the thin myofilaments.
5. Tropomyosin mlcs in the myofilaments shift, exposing actin’s active sites.
Energized myosin cross bridges of the thick myofilaments bind to actin and pull the thin myofilaments together.
Muscles Shortens.

14. Sarcomere structure
Actin
Myosin

15. Sliding Filament Theory

17. Types of Muscle contractions
Isotonic –muscle shortens and movement occurs.
Isometric- muscle does not shorten but tension increases.

18. Twitch contraction
Threshold stimulus – electrical stimulus of sufficient intensity must be applied to the muscle.
A single brief threshold stimulus produces a quick jerk of the muscle.
2msec
25msec
15msec

19. Treppe: A Staircase phenomenon
A gradual step-like increase in the strength of contraction that can be observed in a series of twitch contractions that occur about 1 second apart.
Muscle Fatigue -
Repeated stimulation of muscle in time lessens its
excitability and contractility.

20. Tetanus Smooth sustained contractions
Stimuli comes in rapid succession the muscle does not have time to relax completely before the next contraction.
Normal skeletal muscles exhibit this most of the time.
Rapid repeated Twitch contractions
Looks like one continuous contraction

21. Muscle Tone --tonic contractions A continual partial contraction.
Maintaining posture – sitting or standing
When you pass out/faint muscle tone is lost
Muscles with Less tone are flaccid.
Muscles with More tone are spastic.
Tone is maintained by a negative feedback mechanisms centered in the nervous system (in spinal cord)

22. Muscle Problems
Cramps-painful muscle spasms (involuntary twitches) caused by any irritation or ion and water imbalance
Convulsions-uncoordinated tetanic contractions of varying groups of muscles.
May result from a disturbance in the brain or seizure. AP along motor nerve increases and becomes disorganized

23. Fibrillation – abnormal contraction in which
individual fibers contract out
of sync.(asynchronously)
instead of at the same time.

24. Muscular Disorders Sprains – Joint and ligament damage
Myalgia – Muscle pain
Contusions – bruises – localized bleeding
Poliomyelitis – Viral infection of the nerves that control skeletal muscles.
Muscular Dystrophy – A group of Genetic
Disease characterized by atrophy of skeletal muscle tissues. Some forms Fatal

25. Myasthenia Gravis – Autoimmune disease in which the immune system attacks muscle cells at the neuromuscular junction
So nerve impulses are unable to fully stimulate the affected muscle.
Hernias – Weakness of abdominal muscles can lead to protrusion of an abdominal organ.
Strangulated Hernia – Cuts off blood supply to an organ which can lead to gangrene – death of the organ or individual – Requires emergency surgery.