topics 2 + 3 musculoskeletal system

Question 1

explain bundles

Answer 1

muscle cells are held together in bundles. Many bundles of cells make up one muscle

Question 2

explain Perimysium

Answer 2

a sheath of connective tissue that surrounds each bundle

Question 3

what does the perimysium allow?

Answer 3

-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

Question 4

how do tendons form

Answer 4

the sheaths of CT join at the ends of bundles

Question 5

why is there a gradual decrease in muscular strength?

Answer 5

the amount of connective tissue increases with age

and CT cannot contract making them lose the ability to produce powerful contractions

Question 6

each muscle cell/fibre is:

Answer 6

• an elongated cylinder with many nuclei
• has a plasma membrane= Sacrolemma
  -has cytoplasm= sarcoplasm
• and contains many smaller fibres within it= myofibrils

Question 7

what are Myofibrils?

Answer 7

each muscle cell in a bundle is made up of smaller, parallel fibres

Question 8

what is the name of the tubular network surrounding the myofibrils and what does it do?

Answer 8

• sarcoplasmic reticulum
  -storage site for CA2+ions, which are released during contraction of muscles.

Question 9

what are myofilaments?

Answer 9

they are the tiny protein structures that make up myofibrils

Question 10

whats the two types of myofilament?

Answer 10

Myosin= thick filaments
Actin= thin filaments
actin filaments slide over the mysoin filaments to create movement.

Question 11

why do muscles look striated?

Answer 11

due to the arrangement of thick and thin filaments within the myofibrils. The gaps between the Thick filaments gives the striated look.

Question 12

I band =

Answer 12

actin filaments only

Question 13

A band=

Answer 13

Myosin filaments overlapping actin

Question 14

H zone=

Answer 14

myosin filaments only

Question 15

what does the Sliding Theory state?

Answer 15

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.

Question 16

SLIDING FILAMENT THEORY 1.

Answer 16

electrical impulses arrive at the relaxed muscle via the CNS and calcium in released from the sarcoplasmic reticulum

Question 17

SLIDING FILAMENT THOERY 2.

Answer 17

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

Question 18

SLIDING FILAMENT THOERY 3.

Answer 18

myosin cross bridges bind to actin

Question 19

SLIDING FILAMENT THEORY 4.

Answer 19

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.

Question 20

SLIDING FILAMENT THEORY 5.

Answer 20

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.

Question 21

when does the sliding filament theory stop?

Answer 21

until nerve impulses stop, muscle runs out of ATP or it runs out of calcium