Musculoskeletal system Flashcards
Skeletal muscle
voluntary physical activities, attached to bones
(movement and posture)
Cardiac muscle
heart muscle
Smooth muscle
internal organs, involuntary
Extensibility
Ability to be stretched
Elasticity
ability to return to original length
Tendons
fibrous connective tissue that attaches muscles to bones
Belly
fleshy portion of the muscle
Antagonistic pairs
Muscles can only contract to pull a bone, they can not push it away. So muscles that move bones are always grouped in pairs know as antagonistic pairs.
eg. biceps and triceps work together to move humerus
Origin
The end of the muscle attached to the stationary bone
Insertion
the end of the muscle attached to the moveable bone
Agonist
muscle that causes desired action
Antagonist
the muscle that relaxes while the agonist contracts
Synergists
muscles that help indirectly in steadying a joint during a particular movement.
Fixator
When a synergist immobilises a joint
Muscle tone
when skeletal muscles maintain partial contraction
How are muscle cells held together
in bundles that are held together by a layer of CT
Sarcolemma
The cell membrane that surrounds a muscle fibre
Sarcoplasm
The cytoplasm in the sarcolemma
Transverse tubules
narrow tubes that are continuous with sarcolemma and extend at right angles into the sarcoplasm.
Sarcoplasmic reticulum
membrane similar to endoplasmic reticulum. Forms a tubular network around each Myofibril. Releases Calcium ions in muscle contraction.
Structure of skeletal muscles (5 things)
muscle
muscle fibre bundle
muscle fibre
myofibrils
myofilaments
Z lines
The boundary between adjacent sarcomerers
Sarcomeres
the contractile units of skeletal muscle
Actin
thin myofilaments
Myosin
thick myofilaments
Thin filaments consist of:
-twisted strands of molecules of actin
-Strands of tropomyosin – double-stranded proteins that cover the active sites and prevent actin-myosin interaction
-A troponin –
Thick filaments consist of:
-myosin molecules.
Contraction of a skeletal muscle summary
- A nerve impulse reaches the muscle
- Calcium ions are released and bind to tropomyosin-troponin complex -> which makes active site available
- Myosin head attaches to active site on actin (forms cross-bridge)
- Myosin springs forwards in power stroke which pulls on actin fibres
- As actin and myosin slide across each other the individual sarcomeres shorten bringing the Z-lines closer together
- As many sarcomeres shorten -> muscle fibres shorten -> muscle contraction
6 functions of skeleton
-support
-attachment
-movement
-protection
-storage
-red blood cell production
4 types of bones
-long bone eg. all limb bones so humerus, femur
-short bone, cube shaped eg. carpals, tarpals
-flat bone eg. cranium, sternum, ribs
-irregular eg. vertebrae and coccyx
Ossification
The process of forming bone
Epiphyseal lines
bone growth areas in children
Osteon
The structural unit of compact bone
Trabeculae
The thin bony plates that make up spongy bone
Where does bone growth occur?
the diaphysis and in the two epiphyses.
The 4 main steps in bone formation
-The cartilage undergoes calcification through the
deposition of calcium salts.
-The cartilage cells die and are replaced with OSTEOBLASTS which promote more deposition of calcium salts.
-Osteoblasts mature into OSTEOCYTES.
-Bone formation continues until only a small band of cartilage remains. The remnants of this area are known as the EPIPHYSEAL LINES when the bone stops growing.
Osteoblasts
form bone by promoting deposition of calcium salts into matrix
Osteoclasts
cells that reabsorb bone by secreting enzymes that dissolve the matrix, which release the stored minerals.
Osteoporosis is caused by …
Osteoclasts removing calcium salts faster than osteoblasts deposit them, causes bone to weaken leading to Osteoporosis.
3 types of cartilage
Hyaline
Elastic
Fibrocartilage
Structure and function of hyaline cartilage
Collagenous fibres are thin and tightly packed
Function: provides support and flexibility, makes up rings of trachea and bronchi and found at the end of bones
Structure and function of elastic cartilage
Has elastic fibres as well as collagenous fibres, but they are more spread out.
Function: provides shape and support to places such as ears and nose
Structure and function of fibrocartilage
Has thick, coarse collagenous fibres that are arranged in parallel bundles. fibres are less compacted than hyaline and so is able to be compressed slightly.
Function: acts as a cushion between bones such as between the vertebrae and in the miniscus of the knee joint
