muscle dr. ayisha qureshi assistant professor mbbs, mphil
TRANSCRIPT
![Page 1: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/1.jpg)
MUSCLE
DR. AYISHA QURESHI ASSISTANT PROFESSOR
MBBS, MPhil
![Page 2: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/2.jpg)
MUSCLE (1) purposeful movement of the whole body or parts of the body (such as walking or waving your hand),(2) manipulation of external objects (such as driving a car or moving a piece of furniture),(3) propulsion of contents through various hollow internal organs (such as circulation of blood or movement of a meal through the digestive tract), and (4) emptying the contents of certain organs to the external environment (such as urination or giving birth).
![Page 3: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/3.jpg)
MUSCLE: Chemical energy
↓Muscle Mechanical energy
Muscle forms about 50% of the total body weight: 40% skeletal muscle 10% smooth & cardiac muscleSimply put, Muscles perform the following functions: They contract…They generate heatThey generate motionThey generate forceThey provide support
![Page 4: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/4.jpg)
TYPES of MUSCLE (According to appearance or movement)
![Page 5: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/5.jpg)
Types of Muscle
![Page 6: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/6.jpg)
SKELETAL MUSCLE:
![Page 7: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/7.jpg)
Characteristics of Skeletal Muscles:
Attach to the bone
Move appendages
Support the body
Antagonistic pairs: Flexors & extensors
![Page 8: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/8.jpg)
SKELETAL MUSCLE ANATOMY:
![Page 9: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/9.jpg)
SKELETAL MUSCLE CELL STRUCTURE
A single skeletal muscle cell is also called a MUSCLE FIBER b/c of its greater length than width.
•LENGTH: upto 75,000 µm or 2.5 feet.•DIAMETER: from 10 to 100 micrometers.•SHAPE: elongated & cylindrical.•OUTER MEMBRANE: called sarcolemma.•Nucleus & Organelles: present. Mitochondria, microsomes & ER
What is the chemical composition of the muscle? Proteins (20%) (either as enzymes or for muscle Cont.)Lactic Acid (in muscle that has undergone fatigue) ATP, ADPMyoglobin (stores O2 & gives colour to the muscle)
![Page 10: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/10.jpg)
Skeletal Muscle Organization
Whole Muscle (an organ)↓
Muscle Fiber (a single cell)↓
Myofibrils (a specialized structure)↓
Thick & Thin filaments ↓
Myosin & Actin (protein molecules)
![Page 11: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/11.jpg)
Skeletal Muscle Organization
![Page 12: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/12.jpg)
![Page 13: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/13.jpg)
A single muscle fiber
![Page 14: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/14.jpg)
LAYERS COVERING A MUSCLE:
The skeletal muscle has the following layers covering it: •Epimysium•Perimysium•Endomysium
![Page 15: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/15.jpg)
PROTEINS OF MUSCLE:
![Page 16: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/16.jpg)
ACTIN & THIN FILAMENTS G-actin is the monomer which will form the thin filament. It is a protein with a molecular weight of 43,000. It has a prominent site for cross-linkage with myosin.
G-actin↓
F-actin (6-7 nm long polymerized G-
actin, double stranded in structure)
↓Thin filaments
![Page 17: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/17.jpg)
Regulatory Proteins of the Muscles
TROPOMYOSIN• Rod-like protein• Mol. Weight: 70,000• 2 chains: alpha & beta
chains• Under resting conditions, it
covers the site for myosin attachment on F-actin molecule.
• Forms part of Thin filaments
TROPONIN• Globular protein complex
made of 3 polypeptides • Forms part of thin filaments
![Page 18: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/18.jpg)
![Page 19: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/19.jpg)
THIN FILAMENTS:• Length: 1 µm• Diameter: 5-8 nm • No. of G-Actin mol: 300-400• Other Proteins:
- Nebulin: provides elasticity to the sarcomere. - Titin: is the largest known protein in the body. It connects the Z-line to the M-line in the sarcomere & contributes to the contraction of skeletal muscle.
![Page 20: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/20.jpg)
![Page 21: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/21.jpg)
MYOSIN & THICK FILAMENTS:
Thick filaments consist of 2 symmetrical halves that are mirror images of each other. •Chief constituent is MYOSIN, with a mol. weight of 480,000.•Its molecule has 2 ends, a globular end having 2 heads & a rod-like tail.•It has 6 peptide chains: - 2 identical heavy chains (200,000 each) - 4 light chains ( 20,000 each)
![Page 22: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/22.jpg)
Binding sites on Myosin molecule: The myosin molecule has 2 binding sites: 1.Binding site for ACTIN2.ATPase sit e
![Page 23: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/23.jpg)
![Page 24: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/24.jpg)
![Page 25: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/25.jpg)
A SARCOMERE:
![Page 26: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/26.jpg)
• A myofibril displays alternating dark & light bands.
![Page 27: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/27.jpg)
![Page 28: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/28.jpg)
A sarcomere model:
![Page 29: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/29.jpg)
A SARCOMERE
The area between 2 consecutive Z discs/ lines is called A Sarcomere. It is the functional unit of a muscle.
It has a length of 2.3 µm. It has the following important features:• Z-disc• M-line• I-band• A-band• H-zone• Titin• Nebulin
![Page 30: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/30.jpg)
Sarcomere: Organization of Fibers
• Z disks• I band• A band• H Zone• M line• Titin• Nebulin
Figure 12-5: The two- and three-dimensional organization of a sarcomere
![Page 31: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/31.jpg)
![Page 32: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/32.jpg)
• Z-disc: are dense thin membranes made up of special lattice-like proteins present transversely.
• Dark or A-band: Thick filaments present overlapped by the thin filaments at the ends only.
• Light or I band: area present b/w the ends of the 2 thick filaments. It consists of thin filaments only.
• H-Zone: The lighter area in the middle of the A-band, where the thin filaments do not reach. It consists of thick filaments only.
• M-Line: A line that extends vertically down the middle of the A-band in the center of the H-zone.
• Pseudo H-zone: M-line+ H-zone.
![Page 33: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/33.jpg)
THE SARCOTUBULAR SYSTEM
![Page 34: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/34.jpg)
Sarcotubular System
The sarcoplasm of the myofibril is filled with a system of membranes, vesicles and tubules
which are collectively termed as The Sarcotubular system.
It is made up of:
T-Tubules Sarcoplasmic Reticulum
![Page 35: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/35.jpg)
![Page 36: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/36.jpg)
SARCOTUBULAR SYSTEM Sarcoplasmic Reticulum
(SR)• It is a fine network of
interconnected compartments which run in the longitudinal axis of a myofibril embedded in the I and A bands, & surround them.
• They are surrounded by the sarcoplasm & are NOT connected to the outside of the cell.
• At their both ends they show dilated ends called as Terminal cisterns or sacs.
• They contain a protein called as Calsequestrin, which binds and holds CALCIUM.
Transverse System of Tubules (T-Tubules)
• It is a system of tubules that runs transverse to the long axis of the muscle.
• They enter the myofibrils at the junction b/w the A and I bands.
• The T-tubules open onto the sarcolemma. It is an invagination of the cell membrane & thus communicates with the ECF.
• It functions to rapidly transmit the AP from the sarcolemma to all the myofibrils.
![Page 37: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/37.jpg)
THE TRIAD
• The cisterns of the SR & the central portion of the T-tubules give rise to a characteristic pattern called the TRIAD.
• Each TRIAD consists of 2 terminal sacs of SR & 1 central t-tubule.
• There is no physical communication between each component of the triad.
• In the triad, the cisterns of the SR have the Ryanodine receptors which are complimentary to the Dihydropyridine receptors on the t-tubule. They are both involved in excitation-contraction coupling.
![Page 38: MUSCLE DR. AYISHA QURESHI ASSISTANT PROFESSOR MBBS, MPhil](https://reader035.vdocuments.us/reader035/viewer/2022062320/56649d975503460f94a813c8/html5/thumbnails/38.jpg)