The Musculoskeletal system Flashcards
1
Q
Types of muscle
A
1) Cardiac
2) Smooth
3) Skeletal
- Muscle tissue is made up of cells which contract, generating a great pulling force
2
Q
Cardiac muscle (myocardium)
A
- Contracts rhythmically throughout its lifespan and doesn’t become fatigued
- Cardiac muscle contractions are myogenic - the impulses that cause the muscle fibres to contract are initiated within the heart itself rather than generated by nerve impulses
- It is under control of the autonomic nervous system
- Made up of intercalated discs - muscle fibres join other parallel fibres (striations)
3
Q
Smooth muscle
A
- Smooth muscle is often called involuntary muscle because it is not controlled consciously, it is controlled by the autonomic nervous system
- The lining of some internal organs contains smooth muscle
- Smooth muscle is particularly important in the digestive system
- Its rhythmic contractions help to move food along the digestive tract - peristalsis
4
Q
Skeletal muscle
A
- It is essential for voluntary movement but us also constantly used for maintaining posture
- It covers the skeleton and allows bones to be moved relative to one another
- The voluntary nervous system (somatic) controls the skeletal muscle by sending messages from the central nervous system to the muscle tissue
- Made up of striated muscle fibres
5
Q
Muscle terminology
A
- Origin = Proximal attachment to skeleton
- Insertion = Distal attachment to skeleton
- Action = The function of the muscle e.g flex shoulder joint
- Belly = Main part of the muscle
- Tendon = Band of strong fibrous tissue, connects muscle to bone
- Ligament - Band of fibrous tissue, connects bone to bone or cartilage
- Aponeurosis = Sheet-like tendon, broad attachment e.g. attachment of abdominal muscles
6
Q
Nervous control
A
- Skeletal muscle is under control of the somatic nervous system
- Each muscle is controlled by a motor neurone
- Motor neurones interact with muscles at neuromuscular junctions
7
Q
Muscle structure
A
- The whole muscle is enclosed in a sheath of connective tissue, the epimysium
- This contains a large number of smaller bundles, the fasciculi (fascicles)
- The fascicles are surrounded by connective tissue called perimysium
- Each fascicle consist of connective tissue called endomysium, and muscle cells known as muscle fibres
8
Q
Muscle fibre - Muscle cell
A
- Each muscle fibre is an elongated cell (myocyte) that has many nuclei
- The nuclei are oval in shape and are found at the periphery, just beneath the thin, elastic membrane sarcolemma
- Sarcolemma = cell membrane of the muscle cell
9
Q
Within each muscle cell
A
- Each muscle cell is made up of many small units called myofibrils which are within the sarcoplasm
- Each myofibril consists of repeating small contractile units called sarcomeres
- Each sarcomere is separated by a Z-line
- Sarcomeres are made up of small protein filaments called actin and myosin
- the actin filaments are attached to the Z-line
- Myofibril contains around 10,000 sarcomeres
- Myofibril gives skeletal muscle its striated appearance
- Myofibrils are made up of actin and myosin
- Actin and myosin connect together in a ratchet-like motion to cause muscle contraction
- Muscle generates movement via connection (shortening)
10
Q
Sliding filament theory
A
- This relates to the racket-like motion of actin and myosin fibres (myofibrils)
- For a muscle to contract it requires cellular energy. This comes in the form of ATP
- Calcium ions are released from the sarcoplasmic reticulum and facilitate muscle contraction
11
Q
Muscle contraction
A
- Myosin can only bind to certain parts of the actin molecule
- These are called binding sites
- When a muscle is relaxed, these binding sites are covered by the protein tropomyosin, so myosin can’t attach
12
Q
Sliding filament theory 2
A
- This sliding happens because myosin molecules can bind to actin molecules and pull themselves along the actin
- The end result is that the heads of the myosin molecule haul themselves along the actin molecule, by grabbing onto the next binding site along
- This is the molecular motor of muscle contraction
13
Q
Binding process
A
- In a resting muscle, troponin and tropomyosin are positioned in a way that tropomyosin blocks the myosin binding sites on actin
- When calcium ions are released into the muscle cell upon stimulation, calcium binds to troponin
- The binding of calcium to troponin causes a conformational change in troponin, which in turn, shifts the position of tropomyosin
- As a result of this change, tropomyosin moves away from the myosin binding site on actin, exposing those binding sites
- With the myosin binding sites being exposed, myosin heads can bind to actin, forming bridges and initiating muscle contraction
14
Q
Classification of muscles according to their action
A
- Extensor = increase angle between 2 bones
- Flexor = decreases angle between 2 bones
- Rotation = movement of a limb around the long axis
- Protract = to move a body part/limb forwards
- Retract = to move a body part/limb backwards
- Supination = palm up
- Pronation = palm down
- Agonist = movement of muscles that cause the prime movement
- Antagonist = muscle responsible for opposite action
15
Q
Bursae and Facias
A
- Bursae - a fluid filled sac located between a tendon, ligament or muscle ir reduces friction at a point of contact with bone
- Facias - formed from connective tissue and may separate, surround or connect muscles and act as a fat store
