Muscles

Question 1

Functions of Muscles

Answer 1

• Producing movement
  – Through external environment
  – Propulsion of items in body
• Maintaining posture
• Stabilizing skeleton
• Generating heat

Question 2

Characteristics of Muscles

Answer 2

• Excitability
  – Respond to stimulus
• Contractility
  – Use ATP to shorten forcibly
• Extensibility
• Elasticity

Question 3

Note

Answer 3

make and study a types of muscle table

Question 4

Skeletal Muscle

Answer 4

• Muscle Fiber
  – Long
  
  • Length of muscle
    – Diameter; 5-100 μm
    – Multinucleate
    – Sarcolemma
    – Sarcoplasm
    – Myofibrils; parallel units in
    fiber
  • Sarcomeres; repeated contractile units in
    series within myofibril

Question 5

Sarcomere

Answer 5

functional unit of
striated muscle

Question 6

Myofilaments

Answer 6

• Thin filaments
  – Actin
  – Z disk – bounds each sarcomere; α-actinin
  
  • Thin filaments arise out of this structure
• Thick filaments
  – Myosin
  – Cross bridge with actin

Question 7

Sarcomeres

Answer 7

• A band – Interdigitated actin and myosin
  – Each myosin surrounded by 6 actin filaments
  – Includes H zone
• I band – Portion with only actin (thin)
• H zone – Area with only myosin (thick)
  – Also includes M line
• M Line – Keeps myosin together

Question 8

Myofilaments Substructure

Answer 8

• THIN filaments structure – 3 proteins
  – F-actin = Double stranded helix of G-actin
  
  • G-Actin- globular protein monomer
  • Spherical protein with myosin binding site
    – Tropomyosin = double stranded protein
  • Lie end to end along actin spiral
  • Cover myosin binding sites
    – Troponin Complex (three polypeptides)
  • TnI – Binds to actin; inhibitory subunit
  • TnT – Binds to Tropomyosin; positions it on
    actin
  • TnC – Binds calcium ions

Question 9

Myofilament Substructure

Answer 9

• Thick filaments
  – Myosin protein
  – Two regions
  
  • Entwined tail
  • Globular heads
• Heads form cross
  bridges
  – Flexible
  – Actin Binding Site
  – Myosin ATPase

Question 10

Sacroplasmic Reticulum

Answer 10

• Modified endoplasmic reticulum
  – System of tubules and cisternae that surround
  myofibrils
  – Calcium pump; removes Ca++ ions from the
  sarcoplasm and stores it.
  * Concentrates Ca++ by 2000 times
• T Tubules
  – Part of surface membrane of muscle fiber that
  dips into fiber at junction of A and I bands

Question 11

Depolarization of T-Tubule

Answer 11

depolarizing signal goes down T-tubule to release calcium

Question 12

Sliding Filament Model

Answer 12

• Contractions
• Sarcomeres change length
  – A-band stays constant
  – I-band gets narrower
  – H-zone gets narrower/disappears
• Length-tension relationship: relates amount of
  actin-myosin overlap to tension

Question 13

Length-tension relationship

Answer 13

• Total tension depends on
  – Active component- actin/myosin interaction
  – Passive component- elastic component

Question 14

Length-tension relationship cont

Answer 14

• If interactions between myosin and actin
  are important for contraction, when should
  active component of tension be greatest?
  – Where the overlap between actin and
  myosin heads in the greatest
  – Active tension decreases as muscle
  stretches beyond overlap of actin and
  myosin
  – Active tension decreases as actin bands
  collide and begin to overlap

Question 15

Cross Bridge Cycle

Answer 15

• Cross Bridge attachment (4)
  – Myosin heads undergo conformational change,
  bending the head towards the actin filament
• The Power Stroke (5,6,1)
  – Provides the power to “slide” the actin filament
  
  • P released and power stroke is triggered
  • ADP released but myosin head remains bound in
    rigor
• Cross Bridge detachment (2)
  – ATP binds to head and detaches it from actin
• “Cocking” the myosin head (3)
  – ATPase cleaves ATP and provides energy for
  conformational change of head, “cocking” it.

Question 16

Factors Influencing Strength of Contraction

Answer 16

• Number of muscle fibers contracting within a
  muscle
  – Recruitment related to strength of motor
  stimulus
• Tension developed by each contracting fiber
  – length of fiber at onset of contraction (physical
  limitation)
  – amount of fatigue (physical limitation)
  – thickness of fiber (physical limitation)
• Frequency of stimulation (voluntary control)
  – Summation

Question 17

Treppe Effect

Answer 17

individual stimula with developed to max amount of tension.
Total tension train for humans, wildlife dies if they don’t have high tenstion summation.

Question 18

Summation

Answer 18

Frequency of stimulation- 1, twitch 2, wave summation 3, unfused tetanus 4, fused tetanus
If you can’t move something, muscle tension required is higher than maximum amount someone can resist.