muscle cells Flashcards

1
Q

what are the three types of muscles?

A

-skeletal
-smooth
-cardiac

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2
Q

give three features of skeletal muscle and its 3 overall functions

A

-makes up 40% of the mass of the average human body
-usually voluntary contractions
-involves short single contractions or a long and sustained contraction

functions, posture maintenance, motion and heat production

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3
Q

explain the striated muscle that makes up skeletal muscle

A
  1. attached to bones via tendons and moves the skeleton
  2. divided into fascicles that run parallel
  3. each fascicle consists of a bundle of myofibers and this appears striated under electron microscope
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4
Q

look at the hierarchical organisation of skeletal muscle

A

ok

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5
Q

What’s a sacromere? What does it contain?

A

Sections of myofibrils that shorten in muscle contraction. They contain two Z plates 3 myosin filaments, and 4 actin filaments on either side

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6
Q

In a sacromere,
What is the I band?
What is the A band?
What is the H zone?
What happens to each of these during muscle contraction? Include z plates

A

. Sections of the sacromere of actin only
2. Sections of the sacromere where the actin and myosin overlap and myosin only
3. Sections of the sacromere if myosin only

During muscle contraction:
Z plates come together
I bands shorten as actin is pulled over the myosin
H zone shortens as actin overlaps the myosin more
A band stays the same

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7
Q

how many myofibres per motor unit in the extraocular muscles that control eye movement?

A

10-20

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8
Q

Give the steps of neural excitation at the neural muscular junction

A
  1. Binding of acetyl choline to its receptors leads to their opening as Na+channels
  2. Influx of Na+ leads to local depolarization of the sarcolemma and generation of muscle action potential 3. Depolarisation spreads via T tubules
  3. opening of voltage-gated Ca2+ channels in the sarcoplasmic reticulum(SR)
  4. massive, rapid movementof Ca2+ from SR into the sarcoplasm
  5. Simultaneous contraction of myofibrils → contraction of myofibre
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9
Q

watch videos on the sliding filament theory

A

ok

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9
Q

give the role of Ca2+ in muscle contraction

A

-the calcium ions in skeletal muscle work at actin regulated attraction by moving the troponin-tropomyosin complex off the binding sites allowing actin and myosin to interact

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10
Q

give the role of ATP in muscle contraction by detailing the cross bridge cycle

A

At the end of the power stroke the actin-myosin complex remains intact until ATP becomes available. Upon ATP binding to myosin, myosin head is displaced from actin:- ATP is required for muscle relaxation ATP hydrolysis is needed for return of the myosin head to its resting conformational state- The final product is also the first reactant - the contractile cycle

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11
Q

give the steps of electrical inactivity at the myoneural junction to allow muscle relaxation

A
  1. The sarcolemma returns to its resting electrical potential (about-60mV), as does the entire transverse tubule system and the SR membrane
  2. Removal of sarcoplasmic Ca2+ (ATP-driven Ca2+ pumps in sarcoplasmic reticulum and mitochondria
  3. contractile activity stops and a state of relaxation
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12
Q

what do myofibrils consist of?

A

-thin filament of mainly actin
-thick filament of myosin and each thick filament is surrounded by six thin filaments

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13
Q

what is tetany and how does it come about?

A

its a hypercontracted muscle caused by depletion of ATP due to prolonged period of repetitive muscle stimulation
1. raised sarcoplasmic Ca2+ because no ATP is avaliable to bring Ca2+ into the cisternae of the sarcoplasmic reticulum so Ca2+ remains bound to troponin
2. muscle is highly contracted as no ATP is available to break actomyosin cross bridges

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14
Q

give three sources of ATP in the muscle

A

-creatine phosphate
-anaerobic glycolysis
-aerobic cellular respiration

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15
Q

give three types of skeletal myofibers

A

-slow oxidative fibres. red as they have a high conc of myoglobin, many mitochondria and are very resistant to fatigue
-fast oxidative fibres. also high myoglobin conc and mitochondria and has hugh glycogen stores so generates atp aerobic and anaerobically
- fast glycolytic fibres. low conc of myoglobin and mitochondria, large amounts of glycogen and intense movements of short duration

16
Q

what is rigor mortis and how does it occur?

A

rigid state of muscles that develops shortly after death
1.loss of energy supplies means ion equilibration
2. Sarcoplasmic reticulum and extracellular Ca2+ leaks into the sarcoplasm
3. raise in Ca2+ conc to high levels
4. exposure of actin binidng sites to myosin
5. uncontrolled contractile activity hastens the total exhaustion of ATP supplies and ends with all or nearly all myosin molecules in actomyosin cross bridges

17
Q

give examples of smooth muscle contraction in humans to carry out bodily functions

A
  1. to regulate air flow in lungs
  2. to regulate arterial blood flow
  3. move food along the GI tract
  4. expel urine from bladder
  5. delivering babies
  6. iris sphincter and dilators constrict or dilate the pupils
18
Q

give three features of smooth muscle structure

A

-spindle shape
-single centrally located nucleus
-contractile apparatus due to sarcomere like structure

19
Q

give 5 properties of smooth muscle

A

-contracts involuntarliy
-able to stretch and maintain tension for a long period of time
-slow shortening velocity
-slow actomyosin atpase so slow crossbridge cycle
-high economy of energy utilization during isometric contraction

20
Q

compare smooth muscle contraction with that of skeletal muscle in
force
velocity
energy consumption

A

-force smooth 3x less than skeletal
-velocity smooth 100x less than skeletal
-energy consumption smooth 300x less than skeletal

21
Q
A