Skeletal muscle Flashcards
What is muscle?
soft tissue composed of myocytes (muscle cells/fibres) which contracts to produce force and motions.
-By transforming chemical energy in the form of ATP into to mechanical energy
What else can a muscle be used to refer to ?
to an organ , containing muscle tissue and other tissue.
What is muscle responsible for ?
- Many tasks such as:
1. Locomotion
2. Posture (muscle tone)
3. Generating heat (shivering)
4. Retaining heat (hair follicles)
5. Nutrition – propelling substances (peristalsis)
6. Respiration (breathing)
7. Circulation (pumping blood)
8. Regulating sight and hearing
9. Facial expression
What are the 3 types of muscle tissue?
- Skeletal
- Cardiac
- Smooth
Where is the location of the 3 muscle tissues ?
- Skeletal- inside skeletal muscles- attached to bones or skin-
- Cardiac- within the heart-
- Smooth-walls of hollow organs-
What is the morphology of the 3 muscle tissues?
skeletal and cardiac tissue is striated
smooth muscle is non striated
What is the physiology of the 3 muscle tissues?
Voluntary(somatic)- Skeletal
Involuntary(autonomic)- cardiac and smooth
What does a generalised cell contain ?- cellular anatomy
- Plasma membrane: a selectively permeable outer boundary
- Cytoskeleton: series of filaments and tubules for cell structure and motion
- Cytoplasm: intracellular fluid packed with specialised organelles –
1. Nucleus: controls cellular activity. Typically located near the centre.
2. Mitochondria: the powerhouse of the cell (source of ATP)
3. Rough endoplasmic reticulum: catalytic enzymes for protein synthesis
4. Smooth endoplasmic reticulum: catalytic enzymes for other processes (incl. calcium storage and release)
What is the cytoskeleton like in the myocyte ?
-Cytoskeleton: densely packed with myofilaments of actin, myosin, & titin–packed full of contractile proteins and those are the proteins that a re specialised for causing motion
What is the plasma membrane like in a myocyte ?
it is -called Sarcolemma
What is the cytoplasm like in a myocyte?
-called Sarcoplasm, particularly rich in mitochondria- convert chemical energy into motion (mehcnical energy)
What is the nucleus like in the myocyte?
-Multinucleated (up to 100).
As densely packed with my-filaments the Nuclei pushed out to the periphery
called Sarcosome, unusually large
What is the smooth endoplasmic reticulum in the generalised cell called in a myocyte?
-called Sarcoplasmic reticulum, unusually large & full of calcium
What is the size of the myocte ?
Diameter : 10-40um
Length: 1-40mm
What is the skeletal tissue composed of?
4 tissues
- Muscle tissue
- connective tissue
- blood vessels
- nerve tissue
What are each skeletal muscle ?
a discrete organ, attached to bone
What is the muscle tissue of the skeletal muscle?
-each skeletal muscle is composed of multiple fascicles
What is each fascicle composed of?
bundle of multiple fibres
what do fascicles look like?
bundle of sticks
what are MYOcytes known as?
fibres because they are elongated in one direction ion
What does a muscle contain ?
1000s of densely packed fibres
What does each myocyte contain?
multiple myofibrils
What is the connective tissue of skeletal muscle?
What is holding everything together is:
-Tendons- which attach muscle to bone
What are the 3 types of sheath that compartmentalise the muscle and transmit blood(separate the muscle in different compartments and transmit blood around the muscle) in the connective tissue of skeletal muscle?
- Epimysium- wraps the muscle as a whole
- Perimysium- wraps each fascicle
- Endomysium - extends between individual myocytes
What is the blood vessel tissue of a skeletal muscle?
- Muscle tissue is well vascularised with abundant blood vessels - artery and vein supplying muscle
- A lot of blood is required to as job of ,muscle is to convert chemical energy via ATP to mechanical energy and that requires oxygen and takes a ,lot of nutrients to metabolise hence good blood flow for this and need to take away metabolic waste .
What is the nerve tissue of a skeletal muscle?
each skeletal myocyte is innervated by a single motor axon
- The same axon may alsoinnervateother fibres in the same motor unit (one-to-many).
- Many nerve fibres target muscle. Muscles are the effectors of most of our behaviours.
What is the most prominent feature of skeletal muscle ?
their striations
What are striations ?
are a property of individual myofibrils. (They are visible in skeletal myocytes as a whole since each fibril is precisely aligned
When muscle tissue is viewed longistudinally- can see the striations
What is muscle made of?
Many fascicles which contain myocytes which contain myofibrils which contain myofilaments
What are the 3 types of myofilametns the myofibrils contain?
- thick (myosin
- thin (Actin)
- elastic (titin)
What is the structure of myosin?
- Myosin is an elongated protein molecule composed of a heavy ‘tail’ and 2 light ‘heads’
- The junction of the heads and tail can be regarded as a ‘hinge’
- The heads form part of the ‘cross bridges’ that can attach to actin
- thick (myosin) filament is made up of many individual myosin molecules
What is the size of myosin?
15nm in diameter
What is the structure of actin?
Made up of 3 components:
A helix of two strands of globular actin (a multi-functional protein containing ‘active sites’)
Thin rod like tropomyosin molecules in a helix which lie in the groove formed by twisted actin (cover ‘active’ sites in resting state)
Troponin at regular intervals along tropomyosin – complex of three proteins one of which has a high affinity for calcium ions
What is the size of actin?
7n in diameter
What is then structure of titin?
- are composed of titin (aka ‘connectin’): a large springy protein
- They run through the core of each thick filament, anchoring it in place. It aids in preventing overstretching of the thick filament, allow recoiling like a spring whenever a muscle is stretched
What is a sarcomere ?
Groups of thick (myosin), thin (actin), and elastic (titin) myofilaments are arranged together