topics 2 + 3 musculoskeletal system Flashcards
explain bundles
muscle cells are held together in bundles. Many bundles of cells make up one muscle
explain Perimysium
a sheath of connective tissue that surrounds each bundle
what does the perimysium allow?
-allows each bundle to function as an individual unit
-allows adjacent bundles to slide over one another
-blood vessels run through the CT to supply the muscle
how do tendons form
the sheaths of CT join at the ends of bundles
why is there a gradual decrease in muscular strength?
the amount of connective tissue increases with age
and CT cannot contract making them lose the ability to produce powerful contractions
each muscle cell/fibre is:
- an elongated cylinder with many nuclei
- has a plasma membrane= Sacrolemma
-has cytoplasm= sarcoplasm - and contains many smaller fibres within it= myofibrils
what are Myofibrils?
each muscle cell in a bundle is made up of smaller, parallel fibres
what is the name of the tubular network surrounding the myofibrils and what does it do?
- sarcoplasmic reticulum
-storage site for CA2+ions, which are released during contraction of muscles.
what are myofilaments?
they are the tiny protein structures that make up myofibrils
whats the two types of myofilament?
Myosin= thick filaments
Actin= thin filaments
actin filaments slide over the mysoin filaments to create movement.
why do muscles look striated?
due to the arrangement of thick and thin filaments within the myofibrils. The gaps between the Thick filaments gives the striated look.
I band =
actin filaments only
A band=
Myosin filaments overlapping actin
H zone=
myosin filaments only
what does the Sliding Theory state?
when muscles contract, the sarcomeres shorten because the actin and myosin filaments slide over one another.
BUT
will only happen when a muscle fibre is:
supplied with sufficient energy and is activated by an electrical impulse.
SLIDING FILAMENT THEORY 1.
electrical impulses arrive at the relaxed muscle via the CNS and calcium in released from the sarcoplasmic reticulum
SLIDING FILAMENT THOERY 2.
actin is normally covered in a type of protein called tropomyosin. Calcium changes the shape of tropomyosin, so that myosin cross bridges can bind to the actin
SLIDING FILAMENT THOERY 3.
myosin cross bridges bind to actin
SLIDING FILAMENT THEORY 4.
ATP is broken down to ADP, releasing energy. this enables the myosin to pull the actin filaments inwards, shortening the muscle. this occurs along the entire length of every myofibril in the muscle cell.
SLIDING FILAMENT THEORY 5.
each myosin head can bind repeatedly bind to ATP, break it down and use the energy to pull on actin. hence muscle shortens/contracts more.
when does the sliding filament theory stop?
until nerve impulses stop, muscle runs out of ATP or it runs out of calcium
