smooth,skeletal cardiac muscle

Question 1

what are muscle tissues made from and what their main function

Answer 1

made from mesoderm and differentiate.
Function = contractibility

Question 2

Main muscle tissues and how they look

Answer 2

smooth - are elongated, fusiform (spindle shape) and nuclei are longitudinal in centre. doesnt hv straiations and for involuntary contractions. can contract PHYSICALLY (rapid)/ TONICALLY ( slow)

skeletal - long multinucleated cells with cross striations. Nuclei located at peripherally UNDER THE SARCOLEMMA. voluntary contractions.

cardiac - cross striations and cells are fork shaped with single centre nuclei. cells are joined together by intercalated discs. contractions involuntary and rhythmic.

Question 3

how does contractions work

Answer 3

sliding thick myosin filaments along thin actin filaments due to force on weak interactions in the ridges between actin +mysoin.

• sarcoplasm, sarcoplasmic reticulam, sarcolemma (wall)

Question 4

Skeletal muscle imp structures

Answer 4

• formed of myocytes (muscle fibres) they multinucleated.
• Muscle fibres made of myofibrils, made of actin and myosin. Repeated in sarcomeres
• 2 reglatory proteins: TROPOMYOSIN (blocks the actin myosin binding site) + TROPONIN (Ca2+ bind to this which changes its shape and moves tropomyosin and expose site)
• skeletal muscle covered in sheath = epimysium

found in tongue, diaphr,eyes, upper oesophagus

Question 5

Smooth muscle imp bits

Answer 5

• doesn’t hv myofilaments
• myocytes can tense and relax, so has greater elasticity and function than striated muscle
  *2 SUB UNITS:
  Single unit - within single-unit cells, the whole bundle /sheet contracts, eg contraction in the gastrointestinal tract and bladder. Has lots of of gap junctions to allow electrical connections between cells.
  Multiunit - innervates individual cells, allowing each cell to work independently, eg vascular system where the muscle in each cell is independently innervated
• At cell surface are numerous small plasmalemma invaginations which compartmentalize various signalling components. (caveolae)
• made of myosin ll class, contains heavy chains and light chains (for contraction and relaxation of the) muscle.
• uses calmodulin and MLCK not tropomyosin/troponin to make contract

found in Blood vessels, digestive and
respiratory tracts, uterus, bladder glandular epithelium

Question 6

Cardiac muscle imp bits

Answer 6

• BUNDLE OF HIS (pale cells)
• presence of transverse lines that cross the fibers at irregular intervals where the myocardial cells join.
• many desmosomes and fascia adherens junctions, which provide strong intercellular adhesion during the cells t contractile activity
• Gap junctions + intercalated disks which allow continuity between cells (electrical synapses)
• mitochondria takes 40% of cell vol
  *Secretory granules found
  near atrial muscle nuclei + release the peptide hormone atrial natriuretic factor (ANF) which acts on target cells in kidney to affect Na+
  excretion and water balance. The contractile cells of the heart’s atria serves an endocrine function