skeletal and muscular physiology Flashcards
functions of the muscular system
locomotion,
external mechanical work,
structural support,
movement through vessels,
heat production (shivering)
what are the 3 muscle types and which of these is involuntary
skeletal - voluntary,
cardiac - involuntary,
smooth - involuntary
which of the 3 muscles are unstriated
smooth is unstriated
cardiac and skeletal are both striated
what is the structure of a striated muscle
muscle fibres (single cell) are grouped into bundles of muscle fibre called myofibril (has striation)
myofibrils are bundled in to muscle fibre
what are sarcomeres
interlocking thick myosin and thin actin filaments
what is at the start and end of each adjacent sarcomere
Z line
what are the thin filaments made up of
monomeric units of globular actin (G-actin) polymerised to form actin helix (F-actin)
the actin helix is wrapped by 2 types of molecules, what are they and what is their shape
tropomyosin - filamentous protein
troponin - globular short comlplexes
what are the thick filaments made up of
3 types of myosin protein
2 coiled myosin heavy chains
2 myosin light chains and regulatory light chains associated with the heads
what is the name for the mechanism that allows muscle to contract
sliding filament mechanism
which areas of the muscle shorten during contraction
H zone and I band
what is the cross-bridge theory
cyclic attachment and detachment of actin and myosin
what is the role of calcium in the sliding filament mechanism
calcium binds to inhibitory influence (troponin) and moves it to allow actin to bind
what are the limiting factors to trigger contraction
calcium and ATP in cytoplasm
what controls the amount of calcium in muscle cells
sarcoplasmic reticulum
what 2 receptors are responsible for triggering calcium release
dihydropyridine and ryanodine receptors
what are the stages of exciting muscle
- motor neuron action potential stimulates acetylcholine, triggering action potential in muscle fibre
- action potential moves through T tubules and triggers release of calcium from sarcoplasmic reticulum
- calcium binds to thin filaments and tropomyosin moves away from myosin binding site
- myosin-actin cross bridge forms
- ATP driven power stroke and filament sliding
- cross bridge detaches and cycle repeats if calcium is still present
- when action potentials stop, calcium is sequestered by sarcoplasmic reticulum, tropomyosin returns to block myosin binding sites and muscle fibres relax
functions of the skeletal system:
locomotion and mechanical work,
structural support,
protection,
blood cell production,
mineral storage
what animals have an exoskeleton
most invertebrates
what does an endoskeleton develop from
mesodermal tissue
what is an exoskeleton made of
proteins, carbohydrates or minerals
does an exoskeleton or endoskeleton have a blood supply
endoskeleton does, exoskeleton does not
4 types of bone cell
osteocytes,
osteogenic,
osteoblast,
osteoclast
what is the role of osteocytes
maintain bone tissue
what is the role of osteoblasts
form bone matrix
what is the role of an osteogenic cell
stem cell
what is the role of an osteoclast
reabsorb bone
what do osteoblasts secrete
osteoid to replace bone
what regulates osteoclast activity and how (what chemicals)
osteoblasts and precursors regulate
RANK ligand promotes osteoclast activity
OPG reduces osteoclast activity, by binding to RANKK ligand
what do osteoblasts secrete
hydrochloric acid and enzymes
how much calcium is stored in bone and what is it stored as
stores 99% of bodies calcium
as hydroxyapatite
what 2 hormones are important in regulating calcium levels
parathyroid hormone (PTH) and calcitonin
what does parathyroid hormone do
promote calcium transfer from bone fluid to plasma to counter hypocalcemia
how is calcium rapidly exchanged
calcium ATP pumps
what hormone is mainly used in mammals
parathyroid hormone (PTH)
what animals use calcitonin
fish
where does parathyroid hormone act
on kidneys to reabsorb more calcium and eliminate more phosphate
what else does parathyroid hormone increase
vitamin D activation
what type of feedback regulates parathyroid hormone release
negative
