Topic 7 Flashcards
Functions of muscular tissue
Producing body movements
Stabilizing body positions
Moving substances within the body
Generating heat
Excitability
Ability to respond to stimuli
Contractility
Ability to contract forcefully when stimulated
Extensibility
Ability to stretch without being damaged
Elasticity
Ability to return to an original length
Striated
Alternating light and dark bands
Voluntary
Activity is consciously controlled
Myocyte
Mature muscle cell AKA muscle fibre (set before birth and last a lifetime)
Hypertrophy
An enlargement existing muscle fibres (muscle growth)
Satellite cells
Quiescent cells located next to a muscle fibre and become active when regeneration or repair is necessary
Inside a myocyte
Surrounded by a cell membrane called sarcolemma and contains sarcoplasm and cell organelles, including myofibrils, nuclei, mitochondria, and T tubules
Inside myofibrils
Contractile filaments called actin and myosin
CT components
Fascia
Tendon
Aponeurosis
Fascia
Dense sheet or broad band of irregular CT that surrounds muscles
Epimysium, perimysium, endomysium
Tendon
Cord that attaches a muscle to bone
Aponeurosis
Broad, flattened tendon
A muscle
Fascicles
Blood vessels
Nerves
Epimysium
Fascicle
Muscle fibres
Blood vessels
Nerves
Perimysium
Muscle fibre
Myofibrils Sarcolemma Sarcoplasm Mitochondria Multi nuclei Endomysium
Myofibril
Thin filaments (actin) Thick filaments (myosin) Sarcomeres
Somatic motor neurons
Neurons that stimulate skeletal muscle to contract
Neuromuscular junction
The synapse between the end of a somatic motor neuron and the muscle fibre
Acetylcholine (ACh)
Neurotransmitter released into the synaptic cleft. Binds to receptors on the muscle fibre plasma membrane, causing depolarization of the cell membrane
Neuromuscular junction
1) AP travels along pre-synaptic neuron
2) AP stimulates release of ACh from vesicle into synaptic cleft
3) ions travel across muscle cell membrane which changes charge
4) sarcoplasm continues to depolarize and
5) AP spreads throughout T tubule system
6) stimulates release of calcium into sarcoplasm
7) reuptake of calcium to end contraction
If a muscle contraction occurs for more than a few seconds this will take place
Cellular respiration
Metabolizing
Créatine phosphate - 15 seconds of energy
Anaerobic glycolysis
Converts glucose into ATP - 2 minutes of energy
Aerobic respiration
Converts glucose into ATP as well as going through a number of reactions that require oxygen to produce a lot ATP - minutes to hours of energy
Muscle fatigue
Inability of muscle to maintain force of contraction after prolonged activitiy
Factors that contribute to muscle fatigue
Inadequate release of calcium ions from the SR
Depletion of creatine phosphate
Insufficient oxygen
Depletion of glycogen and other nutrients
Buildup of lactic acid and ADP
Failure of the motor neuron to release enough acetylcholine
Red muscle fibres
Have a high myoglobin content Appear darker Contain more mitochondria Supplied by more blood capillaries Produce slow and weak contractions
White muscle fibres
Have a low content of myoglobin
Appear lighter
Produce fast and strong contractions
Muscle tone
A small amount of tension in the muscle due to weak contractions of motor units
Small groups of motor units are alternatively active
and inactive in a constantly shifting pattern to sustain muscle tone
Muscle tone keeps skeletal muscles firm
Cardiac muscle tissue
Found only in the walls of the heart
Striated like skeletal muscle, mononucleated
Cardiac muscle cells do not regenerate quickly, most often scar tissue forms
Heart contraction
Involuntary
Smooth muscle tissue
Located in the walls of hollow internal organs, blood, vessels, and airways. Also found in the eyes and the
arrector pili muscle of the hair follicles.
Lacks the striations of skeletal and cardiac muscle tissue
Usually involuntary
Contraction lasts longer than skeletal muscles and hence able to sustain long-term muscle tone
Regenerates most easily of all the muscle tissue types
