muscle structure, function and development Flashcards
where are skeletal muscles located?
-attached to bones, or facial muscles to skin
what is the cell shape and appearance of skeletal muscles?
-simple
-very long
-cylindrical
-multinucleate cells with very obvious stritations
where are cardiac muscles located?
-walls of the heart
what is the cell shape and appearance of cardiac muscles?
-branching chains of cells
-uninucleate
-striatiations
-intercalculated discs
where are smooth muscles located?
-walls of hollow organs (other than the heart)
what is the cell shape and appearance of smooth muscles?
-single
-fusiform
-uninucleate
-no striations
muscle structure
muscle function
-produce movement
-maintain posture and body position
-stabilize joints
-generate heat
sarcomere
-contractile unit of muscle fibre
-thick filaments contain ATPase enzymes split ATP to release energy for muscle contractions
-myosin heads (cross bridges) link thick and thin filaments during contraction
-sarcoplasmic reticulum (SR) releases calcium to trigger contraction
special functional properties of skeletal muscles
-irritability
-contractility
-extensibility
-elasticity
irritability
ability to receive and respond to a stimulus
contractility
-ability to forcibly shorten when adequate stimulus is received
extensibility
-ability of muscle cells to be stretched
elasticity
-ability to recoil and resume resting length after stretching
what are skeletal muscles stimulated by?
-motor neurons (nerve cells) to contract
what are motor units?
-one motor neuron
-all the skeletal muscle cells stimulated by that neuron
neuromuscular junction
energy for muscle contraction
-direct phosphorylation
-aerobic pathway
-anaerobic pathway
direct phosphorylation
-coupled reaction of creatine phosphate and ADP
what is the energy source for direct phosphorylation
creatine phosphate
does direct phosphorylation use oxygen?
no
what are the products of direct phosphorylation?
1 ATP per CP, creatine
what is the duration of energy provision for direct phosphorylation?
15 seconds
aerobic pathway
aerobic cellular respiration
what is the energy source for aerobic pathway?
-glucose
-pryruvic acid
-free fatty acids from adipose tissue
-amino acids from protein catabolism
does aerobic pathway use oxygen?
yes
what are the products of aerobic pathway?
-32 ATP per glucose
-CO2
-H20
what is the duration of energy provision for aerobic pathway?
hours
anaerobic pathway
-glycolysis and lactic acid formation
what is the energy source for anaerobic pathway
glucose
does anaerobic pathway use oxygen?
no
what are the products of anaerobic pathway?
-2 ATP per glucose
-lactic acid
what is the duration of energy provision for anaerobic pathway?
40 seconds, or slightly more
types of muscle contractions
-isotonic contractions
-isometric contractions
-muscle tone
isotonic contractions
-myofilaments are able to slide past each other during contractions
-the muscle shortens, and movement occurs
-example: bending the knee, lifting weights, smiling
isometric contractions
-muscle filaments are trying t slide, but the msucle is pitted against and immovable object
-tension increases, but muscles do not shorten
-example: pushing your palms together in front of you
muscle tone
-state of continuous partial contractions
-result of different motor units being stimulated in a systematic way
-muscles remain firm, healthy, and constantly ready for action
development of the muscular system
-without exercise, muscles atrophy
-with extremely vigorous exercise, muscle hypertrophy
-as we age, muscle mass decreases, and muscles become weaker
