1 / 22

Muscle Physiology

Muscle Physiology. Dr Taha Sadig Ahmed. RMP = -90 mV ( same as in nerves ) Duration of AP = 1-5 ms ( longer duration than nerve AP , which is usually about 1 ms ) . Conduction velocity (CV) in a muscle fiber ( cell) = 3-5 m/s ( slower than big nerves ). The Muscle Action Potential.

aisha
Download Presentation

Muscle Physiology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Muscle Physiology Dr TahaSadig Ahmed

  2. RMP = -90 mV ( same as in nerves ) Duration of AP = 1-5 ms ( longer duration than nerve AP , which is usually about 1 ms ) . Conduction velocity (CV) in a muscle fiber ( cell) = 3-5 m/s ( slower than big nerves ) . The Muscle Action Potential Amplitude إرتفاعه RMP= - 90 mV

  3. Muscle Contraction There are 4 important muscle proteins : A/ two contractile proteins that slide upon each other during contraction : • Actin • Myosin B/ And two regulatory proteins : • Troponin excitatory to contraction • Tropomyosin inhibitory to contraction

  4. The EPP at the motor end-plate triggers a muscle AP The muscle AP spreads down inside the muscle through the Transverse Tubules ( T-tubules ) to reach the Sarcoplasmic Reticulum (SR) . In the SR the muscle AP opens calcium channels ( in the walls of the SR)  calcium passively flows out ( by concentration gradient ) of the SR into muscle cytoplasm Ca++ combines with Troponin  Tropomyosin gets moved  Myosin heads combines with Actin

  5. Skeletal muscle is made up of many cylinderical ,multinucleated muscle cells ( fibers) • The fibers ( cell ) can be 10 to 100 ten micron in diameter , and can be hundreds of centimeters long. • & is covered by a cell-membrane called Sarcolemma. One muscle cell ( fiber ) Sarcolemma

  6. Each cell contains between few hundreds to a few thousands Myofibrils The myofibril is striated cand has dark bands  called A-bands) and light bands  called I-bands (I-bands). Each Myofibril Is made of 3000 Actin filaments And 1500 Myosin filaments .

  7. Each myofibril is striated • It is made of Sarcomeres • And each sarcomere is limited by two Z-lines (Z disk) • The sarcomere contains both the  (i) A band and (ii) I band light Z-lines

  8. A-bands consist mainly of thick filament Myosin • The ends of Actin are Z-Discs(Z-lines ). • I-bands consist of thin filament Actin. • The part of the Myofibril lying between two Z-discs is called Sarcomere .

  9. Sliding Filament Mechanism When contraction takes place Actin & Myosin slide upon each other , & the distance between two z-discs decreases This is called Sliding Filament Mechanism . Z-line come closer together I-band gets smaller , and eventually may disappear A-band does not become smaller or bigger

  10. Actin is made of globularprotein callledG-actinG-actins are attached together to form F-actin strand ( chain ) Each two strands wind togetherto form double helix called Actin Filament Tropomyosinlies in the groove between the F-actin strands to cover the active sites on actin that bind the head of myosinTroponinis attached to tropomyosin and to actin Two Actin filaments Groove between the 2 F-actin strands Tropomyosin covering active sites on Actin

  11. Attachment of Ca++ to Troponin initiates tcontractionand when is activated by Ca++ it will move the Tropomyosin away from the active sites on actinn & expose them for Myosin .> then myosin head will immediately attach to these actin active sites > when the myosin head attaches to actin it forms a “ cross-bridge”

  12. Myosin • Each 200 myosin molecules aggregate to form a myosin filament , from the sides of which project myosin heads in all directions .

  13. Myosin • Each Myosin molecule has • (1) Head • ( 2 ) Tail • (3) Hinge (joint ) • Furthermore , each myosin head contains  • (1) ATP-binding site , & • (2) ATP-ase enzyme .

  14. Sliding Filaments

  15. Attachment of Myosin to Actin activates the enzyme ATPase in the Myosin Head  • ATPasebreaks down ATP releasing energy • This energy is used in the “Power Stroke ” to move the myosin head  leading to pulling & dragging of actin  •  sliding of actin on myosin • The “ power stroke ” means tilting of the Myosin cross-bridge and dragging ( pulling ) of actin filament

  16. Then , on order to release the head of Myosin from Actin , a new ATP is needed to come and combine with the head of Myosin . A new ATP binding to Myosin head is essential for detachment of Myosin from Actin

  17. The Cross-Bridge Cycle

  18. Q: What is Rigor Mortis ? • Q: ATP is neede for 3 things : what are they ? • Q: Is muscle relaxation a passive or active process ? Why ? • Q: What happens to A-band and I-band during contraction ? • Q: Ca++ is needed in nerve & muscle : when and where ?

  19. Why do we need the ATP in contraction ? • ATP is needed for 3 things : • (1) Power stroke. • (2) Detachment of myosin from actin active sites . • (3) Pumping C++ back into the Sarcoplasmic reticulum

More Related