Flashcards in Muscle_BTED Deck (47):
What is the function of the muscle?
1) Allow you to stand upright (oppose gravity)
2) Allow movement
3) Allow digestion, control waste removal
4) Affect blood flow
5) Help to maintain normal body temperature
What does the muscle cell contain?
Myofibre - elongated and highly differentiated cell
What is a muscle fibre consisted of?
Bundle of myofibres
What is a fascicles?
Bundle of muscle fibres
What is a muscle?
Bundle of fascicle
What do myofibres contain?
Cytoplasmic filaments - actin and myosin
What ar the organelles in a muscle?
- Cytoplasm = Sarcoplasm
- Smooth ER = Sarcoplasmic Reticulum
- Cell membrane (plasmalemma) = sarcolemma
Name the three different types of muscle
1) Skeletal Muscle
2) Cardiac Muscle
3) Smooth Muscle
What is the most common and characteristic type of muscle?
What is the skeletal muscle used for?
Movement of skeleton (hard tissue)
Movement of organ (soft tissue)
What are the properties of skeletal muscle?
2) Striated (striped)
Why is the skeletal muscle striated?
Arrangement of contractile proteins
What does the Cardiac muscle do?
Forms muscle in heart (myocardium)
What are the properties of cardiac muscle?
3) Rich blood supply
Where is the smooth muscle found?
In walls of blood vessels, and in internal organs (e.g. stomach, bladder, intestines)
What are the properties of smooth muscle?
2) No striations
3) Fusiform small cells
4) Central single nucleus
What is the physiology of skeletal muscle?
- Each myofibril receives neural input from one motor neuron at the neuromuscular junction
- Simultaneous contraction of all muscle fibres in a unit
What is found in the histology of skeletal muscle?
Consists of long, cylindrical, multinucleated myofibrils (muscle fibres/cells)
How long and how thick are the muscle fibres in the skeletal muscle?
Up to 100 micrometer in diameter
Several cm in length
What are myofibrils?
Orderly arrangement of contractile myofilaments actin + myosin
What does the myofibril structure look like?
- Highly regular banding pattern
- Myofibrils pack the full cell volume, pushing organelles to periphery
What does Myosin do?
Forms thick filaments attached to M - line
What does Actin do?
Forms thin filament attached to Z - line
What do the myofibril structure striations contain?
Striations are alternating
- A bands (Anisotropic - refers to behaviour of polarised light)
- I bands (Isotropic)
- Z bands (Bisect I bands)
What do Z bands do?
Divide each myofibril into numerous contractile units - sarcomeres - arranged end to end
What is Actin?
What is Myosin?
2 heads, hinged tail
What happens during muscle contraction?
1) Myosin binds to actin
2) Ca2+ binding - pushes tropomyosin out of binding site
3) Myosin uses ATP as energy source to move head and release actin for another cycle
4) Resting muscle - myosin cannot bind (tropomyosin covers binding site)
What does the conducting system of skeletal muscle allow?
Permits synchronous contraction of all sarcomeres
What does the conducting system of skeletal muscle contain?
1) T tubule system
2) Sarcoplasmic Reticulum
3) Terminal Cisternae
What is the T tubule system?
Extension of Sarcolemma
What is the Sarcoplasmic reticulum?
Membranous network surrounding each myofibril
What is the Terminal cisternae?
Flattened SR beside T tubules - forms a triad
What happens in the Conducting system of skeletal muscle?
1) When a nerve stimulates a myofibre, signal is transmitted by T tubules, causing release of Ca2+ into sarcoplasm from SR
2) The Ca2+ ions activate the sliding filament mechanism - muscle contraction
Where are the Ca2+ ions specifically concentrated in the conducting system?
Ca2+ ions - concentrated within the sarcoplasmic reticulum
What do myocytes look like?
Long, cylindrical cells (1 nucleus)
How are the cells arranged in cardiac muscle?
Cells are in branching alignment
Where do the ends connect to in cardiac muscle?
Ends connect to adjacent cells at intercalated discs
Where are the nuclei located in the cardiac myocytes?
What do the intercalated discs do?
Allow intercommunicating network of cells - contract in synchrony to pump blood
What is the basic organisation of the cardiac myocytes?
Same basic organisation as skeletal muscle - myofibrils, myofilaments and cross - striations
What is located at intercalated discs?
Desmosomes and Gap Junctions
What do the Desmosomes do in intercalated discs?
Provide mechanical stability
What do the Gap Junctions in the Intercalated discs do?
Allow transmission of chemical/electrical signals between cells
What is the smooth muscle for?
Specialised for continuous contractions of relatively low force
What happens during a smooth muscle contraction?
1) No longitudinal organisation of proteins
2) Bundles criss-cross the cell, insert into anchoring points (focal densities) in cytoplasm, cel membrane