Muscle Structure And Function Flashcards
A muscle is a…
Group of specialised, elastic tissues.
Muscle is made up from…
Water (75%), Proteins (20%), Fats (5%), Mineral Salts, and Glycogen
Muscle is the most abundant body tissue in the body. True or false?
True
Describe the structure of muscle tissue.
Muscle tissue bound together in bundles and contained in a sheath (fascia or epimysium), ends extend to form a tendon.
What is the main function of a muscle?
To contract and start movement in surrounding structures (tendon, ligaments, bones).
How does muscle tissue know to contract?
Contracts in reaction to a nerve stimulus sent by brain through motor nerve. Muscle shortens and becomes fatter at centre.
What are the functions of muscle?
- Contract to produce movement
- Stabilise joints
- Maintain postural tone
- Aid in temperature control
What are the three types of muscle tissue?
- Skeletal
- Smooth
- Cardiac
What is the function of Skeletal muscle?
Muscles that we consciously control to start movement.
What is the structure of Skeletal muscle?
Cylindrical cells that make up fibres.
Multinucleate cells surrounded by a sheath (sacrolemma)
Striated (actin and myosin protein filaments).
What is the sliding filament theory?
Muscle contraction = actin filament slides between myosin filament, which shortens and thickens fibres.
What is the function of Smooth muscle?
Unconscious control found in the walls of blood and lymph capillaries, in respiratory, digestive, and genito-urinary systems.
What is the structure of Smooth muscle?
Spindle-shaped cells with no distinct membrane, one nucleus.
What is the function of Cardiac muscle?
Power the pump action of the heart
What is the structure of Cardiac muscle?
Involuntary muscle tissue, striated muscle fibres, each cell has one nucleus.
What is the smallest Skeletal muscle in the body?
Stapedius (middle ear) - sends vibrations from ear drum to inner ear
What is the largest muscle in the body?
Latissimus Dorsi: flat back muscle that covers the central and lower back.
What is the strongest muscle of the body?
Gluteus Maximus (main buttock) - lifts the torso after bending down or leaning over.
What are the two forms of muscle contraction?
Isotonic & Isometric
Isometric contraction is…
Muscle contraction where the length stays the same while tension increases.
E.g., holding a glass of water still in front of you.
Isotonic muscle contraction is…
Muscle contraction where the length changes whilst the tension remains constant.
E.g., lifting a glass of water to mouth and lowering it back onto the table.
What happens during contraction?
Fibres become shorter and thicker and the parts attached to the fibres (periosteum, bone, tendon, fascia) are pulled and move.
What is the ‘all or nothing’ law?
When a muscle fibre contracts it contracts completely or not at all.
The greater number of fibres that contract … =
Greater force produced
How does movement happen?
Muscle passes over a joint to create movement.
Muscle contraction pulls one bone towards another, moving the limb.
Muscles usually work in pairs called:
Agonist (contracting muscle) and opposing Antagonist (relaxing muscle)
How do nerve stimuli cause muscle contraction?
Motor nerves enter muscle and break into many nerve endings, each one stimulating muscle fibres.
Where does a muscle get energy from?
Muscles receive nutrients and oxygen from arterial capillaries.
What is the waste product produced during muscle contraction?
Lactic acid
How is the waste products of muscle contraction removed?
Lactic acid is excreted into the venous blood system.
What are the factors that affect the ability of a muscle to contract?
- Energy availability
- Strength of stimulus from nerve
- Time muscle has been contracting
- Adequate blood supply
- Strength of inhibitory nerve supply
- Temperature of muscle
- Presence of waste products
What does the state of contraction ‘tone’ mean?
Slight degree of contraction.
Always will be some muscle fibres contracting to give normal body posture.
What problems can occur with over-contraction?
Muscle tension & muscle fatigue
Muscle tension is…
Over-stimulation of muscle fibres. More fibres contract than necessary to maintain postural tone.
Muscle fatigue occurs when…
A muscle continues to contract without enough rest, muscle runs out of oxygen and lactic acid builds up.
What is the ‘origin’ of a muscle?
Fixed end of a muscle.
End that barely moves during muscle action.
What is the ‘insertion’ of a muscle?
Moving end of a muscle.
Muscle always works from insertion towards the origin.
What is the ‘attachment’ of muscles?
At the origin or insertion attach to bone via tendons to produce movement of joints.
What is the ‘belly’ of a muscle?
Thickest part or main body of muscle. Usually middle part.
What is a tendon?
White fibrous cords with no elasticity that connect muscle to bone.
What is fascia?
White fibrous connective tissue, found all over the body.
What is the function of ‘superficial fascia’?
Facilitates the movement of the skin, medium for passage of nerves and blood vessels, helps retain body warmth, connects skin with deep fascia.
What is ‘deep’ fascia?
Dense, inelastic, stiff membrane that forms a sheath for muscles and broad surfaces for attachment:
