Chapter 10 11 Flashcards
What is Myology? How many muscles are in human body?
Myology is the study of structure, function
& Diseases of muscles.
640 muscles in human body
What are the functions of muscles?
- Movement
– Stability
– Protection
– Control of passageways, blood flow
– Heat production
– Glycemic control
What are the structural and functional differences between the three types of muscles (skeletal, smooth
and cardiac)?
What are fascia, epimysium, fascicle, perimysium, and endomysium?
Fascia- sheet of connective
tissue that separates muscles
Epimysium – dense regular
connective tissue that surrounds
the entire muscle
Perimysium – fibrous
connective tissue that surrounds
a fascicle
Endomysium – fine sheath of
reticular fibers surrounding each
muscle fiber
What are the different types of muscle fascicles and muscle shapes and how do they influence the strength
of a muscle?
Slide 4
strength of a muscle and the direction of its pull is
determined partly by the orientation of its fascicles
What are tendons, aponeurosis, and retinaculum?
Tendons – a fibrous band
- Biceps brachii, Achilles tendon
Aponeurosis— broad, flat sheet
of tendon (palmar aponeurosis)
Retinaculum— band of
connective tissue under which
tendons from different muscles
pass
What are the functional groups of muscles based on their action?
Prime mover (agonist): muscle that produces most of the force during a particular joint (in flexing elbow the prime mover is the brachialis
Synergist: a muscle that aids the prime mover
Antagonist: opposes the prime mover
Fixator: muscle that prevents movement of bone
What is compartment syndrome (Know the cause, symptoms and treatment)?
Compartment syndrome is muscle necrosis, myoglobinuria,
Treatment is fasciotomy
What are the universal properties of muscles?
Excitability
Contractility
Extensibility
Elasticity
What are intrinsic and extrinsic muscles?
Intrinsic muscles are entirely contained within
a particular region, having both its origin &
insertion there.
Extrinsic muscle acts upon a designated region
but has its origin elsewhere.
What are the innervations of a muscle?
Innervation of a muscle—nerve that stimulates it
How much blood supply is received by the muscles during rest and during exercise?
1.24 L/min of blood/min at rest, during heavy
exercise 11.6 L/min
What are the structural components of a skeletal muscle fiber?
See slide 12
Sarcolemma
* Sarcoplasm
* Myofibrils—long protein cords that
occupy the main portion of the
sarcoplasm
* Mitochondria
* SR
* Terminal cisternae
* Triad
What are different types of myofilaments? Which ones are the contractile and regulatory myofilaments?
Thick, Thin, and Elastic
Contractile proteins—myosin and actin do the work
* Regulatory proteins—tropomyosin and troponin
What is the role of elastic filaments and accessory proteins?
Elastic Filaments Flank each thick filament and anchor it to the Z disc and M
line
Accessory proteins anchor the myofilaments, regulate the length of myofilaments, keep
alignment for optimal contractile effectiveness
– Genetic defects in dystrophin produce disabling disease muscular
dystrophy
What is the cause for muscular dystrophy?
genetic effects in the dystrophin is the cause
What is a sarcomere? What are A band, I band, H band, M line, Z disc? What is the sliding theory for
muscle contraction?
See diagram on slide
Sarcomere— Functional contractile unit of muscle fiber
A band: dark; A stands for anisotropic
I Band light due to thin filament and no overlap; I stands for
isotropic
H band: middle of A band; thick filaments only; no overlap
M line: middle of H band; darker due to the presence of the protein
desmin
Z disc: provides anchorage for thin filaments and elastic filaments, Z
discs are pulled closer as the thin filaments slide over thick filaments
Sliding theory for muscle contraction is that thin filaments slide over the thick one
What are the sequential events that occur during muscle contraction?
See Slide 20
1. Myosin cross-bridge attaches to the actin myofilament
2. Working Stroke- the myosin head pivots and bends as it pulls on the actin filament sliding it towards the M line
3. As new ATP attaches to the myosin head, the cross bridge detaches
4. As ATP is split into ADP and Pi, cocking of the myosin head occurs
What is a motor unit? What is the effect of a small and a large motor unit?
Motor unit—one nerve fiber and all
the muscle fibers innervated by it
small motor unit= used when fine control is needed (small sensitive neurons)
large motor unit= used when strength is more important (larger less sensitive neurons)
What are the structural components of a neuromuscular junction?
See slide 23
Motor Nerve fiber, Myelin, Schwann cell, Synaptic knob, basal lamina, synaptic vessels (contains ACh), Sarcolemma Synaptic clef, ACh receptor, junctional folds, mitochondria,
What are the phases of contraction and relaxation? Know the physiological events that occur during each phase
Four major phases are Excitation, Excitation-contraction coupling, Contraction, Relaxation
Excitation- Arrival of the nerve signal, Acetylcholine (ACh) release
Excitation-contraction coupling- Action potentials propagated down T tubules, calcium released from terminal cisternae, binding of calcium to troponin, shifting of tropomyosin
Contraction- hydrolysis of ATP to ADP +Pi; activation and cocking of myosin head (recovery stroke), formation of myosin-actin cross-bridge, power stroke (sliding of thin filament over thick filament), binding of new ATP; breaking of cross-bridge
Relaxation- Cessation of nervous stimulation and ACh release, ACh breakdown by acetylcholinesterase (AChE), reabsorption of calcium ions by sarcoplasmic reticulum
RMP, depolarization, repolarization, action potential and ATP uses?
RMP= resting membrane potentional
Depolarization- shift in electrical potential across a plasma membrane to a value less negative than the resting membrane potential (happens in excitation of a nerve-muscle)
Repolarization- reattainment of the resting membrane potential after a nerve or muscle cell has depolarized
Action potential- rapid voltage change in which a plasma membrane briefly reverses electrical polarity
ATP in Contraction- Myosin head needs an ATP molecule bound to it to initiate contraction
What is spastic paralysis and flaccid paralysis? What is the effect of various neuromuscular toxins-
pesticides, tetanus toxin, curare, botulism?
Spastic paralysis: a state of continual contraction of the muscles; possible
suffocation
Flaccid paralysis—a state in which the muscles are limp and cannot contract
Some pesticides contain cholinesterase inhibitors that prevent Ach degradation
Tetanus toxin blocks glycine release in the spinal cord and causes
overstimulation and spastic paralysis of the muscles
Curare: compete with ACh for receptor sites, but do not stimulate the
muscles
Botulism—type of food poisoning caused by a neuromuscular toxin secreted
by the bacterium Clostridium botulinum
What is the relation between muscle length and muscle tone?
slide 33
if a fiber was extremely contracted, thick filaments would be too close to Z disc thus the thick filaments wouldn’t be able to contract much farther until hitting the z discs
If a muscle fiber was extremely stretched there would be little overlap of the thick and thin filaments
What are the requirements for the regulation of skeletal muscle contraction?
Requirements for the regulation of skeletal muscle contraction are
ATP, calcium, proximity of actin and myosin head
What are isometric and isotonic contractions?
Isometric muscle contraction
– develops tension without changing length
Isotonic muscle contraction
– tension while shortening = concentric
– tension while lengthening = eccentric
What are the uses of ATP?
- Breaking the Old Cross Bridge
- Energy for the Power stroke
- Energy for Calcium Pump in Sarcoplasmic
Reticulum - Energy for Na/K ATPase
What are the modes of ATP synthesis during immediate, short term and long-term exercise?
immediate- oxygen need is supplied by
myoglobin
short- muscles transition to anaerobic fermentation to generate ATP by glycosis
long- Aerobic respiration
* 36 ATP from glucose
What happens during fatigue?
Potassium accumulation- K+ released during
action potential
* ADP/P accumulation- hydrolysis of ATP
What happens during myasthenia gravis?
Autoimmune disease - antibodies
attack NMJ and bind ACh receptors
in clusters
What is the cause for hernias and what are the main type of hernias?
Hernia—any condition in which the
viscera protrudes through a weak
point in the muscular wall of the
abdominopelvic cavity
inguinal Hernia, Hiatal hernia, Umbilical hernia
What are the two main types of smooth muscles and how do they differ?
Single unit and multiunit smooth musles
