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Muscle tissue Flashcards

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1
Q

what are the types of muscle?

A

-skeletal
-cardiac
-smooth

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2
Q

what do skeletal and cardiac muscle have in common?

A

-both have somatic innervation

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3
Q

what type of innervation does smooth muscles have?

A

-autonomic innervation

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4
Q

how does muscular tissue contribute to homeostasis?

A

by:
-producing body movements
-stabilising body position
-moving fluid and substances

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5
Q

what are the properties that enable muscles to function and contribute to homeostasis?

A

-excitability
-contractility
-extensibility
-elasticity

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6
Q

what does the skeletal muscle pump do?

A

-aid the heart in venous return
-relies on the presence of valves in veins

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7
Q

how does the skeletal muscle pump rely on the presence of valves in veins?

A

-at rest both valves open
-there is contraction of skeletal leg muscles-this pushes blood through the proximal valve and closes the distal valve
-skeletal muscles relax-the proximal valve closes and the distal valve opens

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8
Q

what is the appearance of skeletal muscles like?

A

-they have a long cylindrical fibre with many peripherally located nuclei, striated

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9
Q

where is the location of skeletal muscles?

A

-it is most commonly found attached by tendons in bones

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10
Q

what is the appearance of cardiac muscles like?

A

-they are branched cylindrical fibres with one centrally located nucleus
-intercalated discs join neighbouring fibres,striated

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11
Q

where is the location of cardiac muscles?

A

heart

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12
Q

what is the appearance of smooth muscles like?

A

-the fiber is thickert in the middle, tapered at each end and has on centrally positioned nucleus, it is not striated

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13
Q

where is the location of smooth muscles?

A

-walls of hollow viscera, airways,blood vessels, iris and ciliary body of the eye,arrector pili muscles of hair follicles

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14
Q

what is the fiber diameter of each type of muscular tissue?

A

-skeletal-very large (10-100um)
-cardiac-large (10-20um)
-smooth-small (3-8um)

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15
Q

what is the fascia?

A

-a dense sheet or broad band of irregular connective tissue that surrounds muscles and other organs of the body e.g
-epimysium
-perimysium
-endomysium

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16
Q

what is the tendon?

A

-a cord that attaches muscle to a bone

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17
Q

what do somatic motor neurons do?

A

-stimulate skeletal muscles to contract
-they branch many times,each branch extending to a different skeletal muscle fiber
-each muscle fiber is in close contact with one or more capillaries

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18
Q

what are within myofibrils?

A

-filaments and sacormeres

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19
Q

what are filaments and sacormeres?

A

-filaments are thick and thin structures
-sarcomeres are compartment of arranged filaments and they are the basic functional unit of a myofibril

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20
Q

what are z-discs?

A

they separate one sarcomere from the next

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21
Q

what is the A band?

A

-darker,middle part of the sarcomere and the thick and thin filaments overlap

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22
Q

what is the I-band?

A

-lighter part and contains only thin filaments,Z discs pass through the centre of each I band

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23
Q

what is the H-zone?

A

-the centre of each A band which contains only thick filaments

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24
Q

what is the M-line?

A

-it supports proteins that hold the thick filaments together in the H zone

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25
what three kinds of proteins are myofibrils built from?
-contractile proteins -regulatory proteins -structural proteins
26
what are contractile proteins like?
-they have myosin-thick filaments -they convert ATP to energy of motion (chemical to mechanical energy) -they have actin-thin filaments that is the site where a myosin head attaches
27
what are regulatory proteins like?
-consist of troponin and tropomyosin -in relaxed muscle myosin is blocked from binding to actin -calcium ion binding to troponin moves tropomyosin away from myosin this allows muscle contraction
28
what ate examples of structural proteins?
-titin -α-actinin -Myomesin
29
what is the sliding filament mechanism?
-with exposure of the myosin binding sites on actin (the thin filament) in the presence of Ca2+ and ATP the thick and thin filaments slide on one another and the sarcomere is shortened
30
why is calcium key to muscle contraction?
in the SR,the calcium binding protein(calsequestrin) binds to Ca2+ and this enable more Ca2+ to be taken up into the SR
31
what are the 4 steps of the contraction/the cross bridge cycle
-ATP hydrolysis -Formation of cross-bridges -Power stroke -Detachment of myosin from actin
32
what happens during ATP hydrolysis?
-myosin heads hydrolyse ATP and become reoriented and energised
33
what happens during the formation of cross bridges?
myosin binds to actin forming cross bridges
34
what happens during a power stroke?
-myosin cross bridges rotate towards the centre of the sarcomere
35
what happens during the detachment of myosin from actin?
as the myosin heads bind to ATP,the cross bridges detach from the actin
36
what are the two processes that permit skeletal muscle contraction?
-ACh is being broken down by acetylcholinesterase (AChE) -Ca2+ active transport pumps
37
what happens as Ca2+ levels drop?
tropomyosin-troponin complexes slide back over the myosin binding sites on actin and this prevent cross-formation
38
what is maximum muscle tension (force) dependent on?
-Rate of nerve impulses at NMJ-frequency of stimulation -Amount of stretch before contraction -Nutrient and O2 availability -Number of muscle fibres that are contracting i.e the size of the motor unit
39
what is the length-tension relationship?
when a muscle fibre develops its greatest tension when there is an optimal overlap between the thick and thin filaments
40
what is a motor unit?
-it consists of a somatic motor neuron and all the skeletal muscle fibres it stimulates
41
how many motor units are there for voice control,eyemovement and limbs?
-voice control=2-3 muscle fibres/motor units -eye movement-10-20 muscle fibres/motor units -limbs=2000-3000 muscle fibres/motr units
42
what is twitch contraction?
a brief contraction in response to a single action potential
43
what is the refractory period?
-a period of lost excitability,muscle cannot be excited again during this time
44
what is the refractory period for skeletal and cardiac muscles?
-skeletal-about 5ms -cardiac-about 30ms
45
what is wave summation?
the phenomenon in which stimuli arrive at different times causing larger contractions
46
when does wave summation occur?
-when additional Ca2+ is released fromSR and levels of sarcoplasmic Ca2+ are still high from previous stimulus
47
what are the types of contraction?
-isotonic contraction -isometric contraction
48
what is isotonic contraction?
-contraction for body movements and tension remains constant while the muscle changes length
49
what are the two types of isotonic contraction?
-concentric isotonic contraction -eccentric isotonic contraction
50
what happens in concentric isotonic contraction?
-the muscle shortens to produce movement
51
what happens in eccentric isotonic contraction?
the muscle lengthens to produce movement
52
what is isometric contraction?
-contraction for posture where the tension is not enough for the object to be moved and the muscle does not change its length
53
what are the types of skeletal muscles fibres?
-red muscle fibres -white muscle fibres
54
what do red muscle fibres have?
-high myoglobin content -high numbers of mitochondria -supplied by more blood capillaries
55
what do white muscle fibres have?
-low content of myoglobin
56
what are the three main types muscle fibres are classified into?
-slow oxidative fibres -fast oxidative glycolytic fibres -fast glycolytic fibers
57
what type of muscle fibres do postural muscles of the neck,back and legs have?
-a high proportion of slow oxidative fibres
58
what type of muscle fibres do muscles of the shoulders and arms have?
-a high proportion of fast glycolytic fibres
59
what type of muscle fibres to leg muscles have?
-have large numbers of both slow oxidative fibres and fast oxidative glycolytic fibres
60
what does aerobic exercise do to some FG fibres?
transforms them into FOG fibres
61
what is hypertrophy?
where exercises that require short bursts of strength produce and increase in the size of FG fibres
62
what is the cardiac muscle?
-the principle tissue in the heart wall -contains connexions that allow action potentials to spread from one cardiac cell to the next -it allows the entire myocardium of atria or ventricles to contract as a single coordinated unit
63
what is the structure of the cardiac muscle?
-the muscle has the same arrangement of actin and myosin as skeletal muscle fibres -the mitochondria are large and numerous (25% of cytosolic space) -contractions lasts longer than a skeletal muscle twitch (up to 15times)
64
what is the smooth muscles?
-muscle that are activated involuntarily -there are two types:visceral(single unit) and multi unit smooth muscles
65
where are visceral smooth muscles found?
-walls of small arteries, veins ans hollow organs like the stomach, bladder,intestines and uterus -walls of large arteries, airways and muscle that attach hair follicles and muscles of the iris and ciliary body
66
where are multi-unit smooth muscles found?
-walls of large arteries,airways and muscles that attach to hair follicles and muscles of the iris and ciliary body
67
what is the anatomy of smooth muscles?
-filaments are not arranged in orderly sarcomeres, not striated -they attach to dense bodies and stretch from one dense body to another -the dense bodies function like z-discs -there is only a small number of SR -there are no T-tubules only caveolae (pouch like invaginations) which contain Ca2+
68
what is the contraction of smooth muscles like?
-the contractions are slower and last much longer than skeletal or cardiac -smooth muscles can shorten and stretch to a greater extent than other muscle types
69
what do most smooth muscle fibres contract or relax in response to?
-Action potentials from the autonomic nervous system -Stretching -Changes in pH,oxygen and carbon dioxide - Hormones-epinephrine causes relaxation of smooth muscle in the air ways and in some blood vessel walls

cells to systems (14 decks)

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