Contractions

Excitation- Contraction Coupling:

Electrical Impulse (Action Potential) (

) spreads across Sarcolemma

1. Electrical Impulse spreads into T-tubules

2. Ca 2+ is released from Sarcoplasmic Reticulum into Sarcoplasm

3. Ca 2+ binds to Troponin

4. Troponin moves Tropomyosin off Active Sites

5. Active sites are uncovered

6. Myosin Heads bind to Active Sites

7. Contraction begins

How is a Skeletal Muscle Fiber Stimulated to Contract?

1. Extensibility

2. Elasticity

3. Excitability

4. Contractility

Concentration Gradient

• NA+ HI outside cell

• K+ HI inside cell

Neuromuscular Junction Contains:

• Axon Terminal of Motor Neuron
  "bulb-shaped end of motor neuron
  Contains vesicles filled with ACho

• Synaptic Cleft SPACE between neuron and motor end plate

• Motor End Plate

Events at the NMJ

AP_ arrives at AXON TERMINAL.

Ca+2

1. Voltage-Gated Ca 2+ Channels OPEN and Ca 2+ ENTERS Axon Terminal.

2. Ca 2+ stimulates release of ACh ( •) into SYNAPTIC CLEFT.

3. ACh ( •) binds to Chemically-Gated Na+ Channels on MOTOR END PLATE

4. Chemically-Gated Na+ Channels OPEN and Na+ flows INTO Sarcoplasm. 9

5. DEPOLARIZATION of MOTOR END PLATE to Threshold

6. AP
   AP _ Generated in Sarcolemma spreads into T-Tubules.

Na+

ACh (e) is broken down by ACh Esterase in the synaptic cleft or by diffusion away from the synaptic cleft.

Where are they located

Voltage-Gated Ca 2+ Channels ll are located in the AXON TERMINAL.

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2. Chemically-gated Na+ Channels are located in the MOTOR END PLATE

Muscle layers

• Epimysium (outer layer) Covers entire muscle ( MUSCLE ORGAN)

• Perimysium (middle layer) Covers each fascicle ( FASCICLE)

• Endomysium (inner layer) Covers each muscle fiber ( MUSCLE FIBER)

• MYOFIBRILS

• SARCOMES

Adduction

To or towards

Abduction

Away from

Rictus

rectus

Straight

Sub

Under

Origin

Attached to fixed part of bone

Instertion

Attached to bone that will move

Agonist

Main muscles that will move

ANTagonists

Muscles that will help support main muscle to move