Muscular system
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Name the 3 types of muscle tissue and whether each is striated or not.
SCS • Skeletal - striated Attaches to bones by tendons • Cardiac - striated Heart wall • Smooth - not striated In walls of hollow structures, e.g. intestines
Two functions of muscle tissue
• produce body movement • Stablise body positions • Move substances within body • produce heat
List and describe the 5 properties of muscle tissue
• excitability - can respond to chemicals • conductivity - propagate electrical signals across plasma membrane • contractility - able to contract • extensibility - ability to stretch without damaging tissue • elasticity - return to original shape after stretching CCEEE
Name the connective tissue coverings on a muscle (one main one and then 3 extending from that one)
Fascia Epimysium - outer layer encircling entire muscle, dense irregular CT Perimysium - bundle large groups of muscle fibres, dense irregular CT Endomysium - separates individual muscle fibres from each other, reticular fibres
MUSCLE FIBRE CELL COMPONENTS Sacolemma
Plasma membrane
MUSCLE FIBRE CELL COMPONENTS Transverse tubule
Through sarcolemma into centre of each muscle cell
MUSCLE FIBRE CELL COMPONENTS Sarcoplasm
Cytoplasm of muscle cell Myoglobin and glycogen Release oxygen when needed by mitochondria for ATP production
MUSCLE FIBRE CELL COMPONENTS Sacroplasmic reticulum
Fluid-filled system of membraneous sacs; encircle each myofibril Stores calcium, triggers muscle contraction by releasing Ca2+
MUSCLE FIBRE CELL COMPONENTS Myofibrils + 3 types of proteins
Small, thread-like proteins in the sarcoplasm Contractile organelles • Contractile protein - generate force during contraction • regulatory protein - help switch contraction processes on and off • structural protein
MUSCLE FIBRE CELL COMPONENTS Myofilaments
Compartments
What is the contraction cycle?
Repeating sequence of events that result in contraction of muscle
Describe the 4 steps of the contraction cycle
• ATP hydrolysis - ATP hydrolysised into ADP • Cross bridges formed - attachment of myosin to actin • Power stroke - Sliding • Detachment of myosin from actin
Name the 3 ways to produce ATP for muscle contraction
Creatine phosphate - max 15 seconds (sprint) Anaerobic glycolysis - max 2 mins (200m sprint) Aerobic respiration - more than 10mins (marathon) CAA
What is a motor unit?
1 somatic motor neuron + all skeletal muscles it stimulates
What factors impact the strength of a muscle contraction?
Size of motor unit and number activated
What is a twitch contraction?
Brief contraction of all muscle fibres in a motor unit in response to a single muscle action potential
Describe what happens in the contraction and relaxation period
Contraction period: Ca2+ binds to troponin; myosin binding sites on actin are exposed and cross bridges form; peak tension develops Relaxation period: Ca2+ is actively transported back into the SR; myosin heads detach from actin; tension in muscle decreases
What is muscle tone?
Involuntary, weak contraction of a small number of motor units that are alternatively shifting between active and inactive
What happens to tension and muscle length in isometric, concentric and eccentric contractions?
Isometric: constant tension and muscle length Concentric: Shorten length, increase tension Eccentric: Lengthen and increase tension
Name 3 skeletal muscle types
Slow oxidative Fast oxidative Fast glycolytic
For each of the 3 skeletal muscle types (Slow oxidative, Fast oxidative, Fast glycolytic) describe: structure method of producing ATP primary function location
Slow oxidative: many mitochondria and capillaries; red; aerobic respiration (high); postural muscles, e.g. neck; maintain posture and aerobic endurance Fast oxidative: many mitochondria and capillaries; red-pink; aerobic respiration and anaerobic glycosis; lower limb muscles; walking/sprinting Fast glycolytic: Few mitochondria and capillaries; white (pale); anaerobic glycolysis; upper limb muscles; rapid/intense movements of short duration
What is the attachment of a muscle’s tendon to the stationary bone called?
Origin
What is the attachment of a muscle’s tendon to the moveable bone called?
insertion
What is the fleshy portion of the muscle between attachment sites called?
Belly