Structure and Function of muscle

Question 1

Three types of Muscle tissue

Answer 1

1. Skeletal
2. Smooth
3. Cardiac

Question 2

Skeletal muscle comp.

Answer 2

75% water
20% protein
5% salt and other substance

Question 3

Layers of CT

Answer 3

• epimysium (upon)
• perimysium (around)
• endomysium (within)

Question 4

Layers of Muscle Tissue

Answer 4

• Muscle belly (bundle of fasciculia)
• Fasciculus – Group of muscle fibers
• Muscle Fibers/Muscle Cells/Myofibers
  
  • Myofibrils
    
    • Sarcomeres – Basic functional unit of muscle

Question 5

Plasmalemma/Sarcolemma (cell membrane)

Answer 5

Fuses with tendon
Conducts action potential (electrical signal for muscle contraction)
Maintains pH
Transports nutrients; capillary interaction

Question 6

Satellite Cells

Answer 6

Involved in muscle growth and development

Aids responses to injury and training

Question 7

Nucleus

Answer 7

DNA storage

Unlike other cells, muscle fibers have multiple nuclei

Question 8

Sarcoplasm

Answer 8

Fluid portion of cell
Called cytoplasm in other cells; organelles, proteins, minerals, fats
Unlike other cells, contains large amounts of Glycogen and Myoglobin (similar to Hemoglobin)

Question 9

Transverse Tubules/T-Tubules

Answer 9

Carry action potential deeper into muscle fiber

Pathway for substances to enter and exit the cell

Question 10

Sarcoplasmic Reticulum

Answer 10

Storage site of Calcium (Ca2+)

Calcium is essential for muscle contraction

Question 11

Thick Protein Filaments

Answer 11

shows up darker under microscope
myosin
-2/3 of muscle protein
-anchored to m-line
-two protein strands twisted together 
-end folds into globular heads (myosin heads)
titin
-stabilize the myosin filaments
-Ca binds to it increasing force when stretched 
-prevents overstretching 
-extends from Z to M-line

Question 12

Thin Protein Filaments

Answer 12

lighter under microscope 
inserts into Z-line
Actin
-contains myosin-binding sites
Tropomyosin
-Covers binding site at rest
Troponin
-Moves Tropomyosin away from binding site
Nebulin
-Anchoring protein for Actin

Question 13

Motor unit

Answer 13

starts in the motor cortex
α-motor neuron and all the muscle fibers it innervates
more activated motor units=greater force

Question 14

Neuromuscular Junction

Answer 14

Synapse between α-motor neuron and muscle fiber

Communication between neuron and muscle

Question 15

Excitation-Contraction Coupling

Answer 15

1. The action potential arrives at the axon terminal, releasing acetylcholine (ACh)
2. ACh crosses the synaptic cleft and binds to ACh receptors on plasmalemma
3. The action potential travels down the T-tubules
4. The action potential triggers Calcium release from the Sarcoplasmic Reticulum
5. Calcium binds to Troponin and enables Actin-Myosin contraction

Question 16

Sliding Filament Theory

Answer 16

after power stroke

• The Myosin Head detaches from Actin
• The Myosin Head rotates back to its original position
• The Myosin Head attaches to a new site further down on Actin

Question 17

Energy for Muscle Contraction

Answer 17

ATP
ATP breaks down into ADP releasing the stored energy
Located on the Myosin head
Required to detach the myosin head from actin
ATP is needed to pump Ca back into the Sarcoplasmic Reticulum