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Unformatted text preview: cles bind to the terminal membrane, which in turn releases the Ach into the synapse.
5. Ach diffuses across synapse and binds to Ach receptors on the sarcolemma, which causes the chemically-gated sodium channels to open, allow for
a sudden influx of sodium, causing depolarization.
6. The depolarization causes an action potential to propagate along the sarcolemma by the opening of voltage-gated sodium channels.
7. The sarcolemma will then repolarize by opening potassium channels as the sodium channels close. Since more potassium leaves than is needed, a
period of hypolarization occurs, causing a relative refractory period.
8. The sodium-potassium pump will then restore the regular ion distribution.
9. As all this is going on, the Ach will detach from the receptors and either get broken down by acetylcholinesterase or recycled via the Ach re-uptake
10. As the action potential passes along the sarcolemma, it comes across T-tubules and enters them. The T-tubules run transverse to the length of the
muscle, so it is very useful for carrying the action potential to the muscle cell’s interior. T-tubules also attach to the sarcoplasmic reticulum (SR),
which stores calcium.
11. When the action potential moves down the T-tubules, it causes the SR to release calcium ions into the sarcoplasm.
12. The calcium ions in the sarcoplasm will bind to Troponin C, causing a conformation shift that moves the tropomyosin away from the active site on
13. With the active site on the actin exposed, myosin molecules eagerly binds to actin with the energy from bound ATP.
14. The myosin heads then swivel, pulling the Z-lines closer together and shortening the sarcomeres. As this occurs, ADP and Pi are released. Heat is
15. ATP is taken up by myosin heads as the crossbridges detach.
16. ATP is then hydrolyzed and energy transferred to myosin heads as they cock and reset for next stimulus.
1. Biceps brachii and triceps brachii – flexion and extension of the forearm at the elbow, respectively.
2. Quadriceps femoris and hamstrings – flexion and extension of the knee, respectively.
3. Rectus abdominus and erector spinae – flexion and extension of trunk, respectively.
4. Masseter and platysma – opens and closes the jaw, respectively.
5. Rhomboids (major and minor) and serratus anterior – retraction and protraction of the scapula, respectively.
1. Masseter and temporalis – closes the jaw
2. Supraspinatus and deltoid – abducts humerus
3. Biceps brachii and brachialis – flexion of the forearm at the elbow
4. Internal oblique and external oblique – bilateral trunk flexion
5. Adductor brevis and adductor longus – adducts and flexes the thigh
5. The pectoralis major, rhomboids, and trapezius fixates the scapula when the deltoids abduct the arm.
Soleus – fixes foot in a plantar flexed position
Brachioradialis – fixates forearm in flexed position when carrying something
Gemellus – stabilize head of femur
Gluteus medius – steadies and places thigh in walking
Spinal Tracts Assignment
1o, 2 o, 3 o with pathway (3 Sensory, 1 Motor) Information
Destination Spinocerebellar Tract (sensory) Conducts proprioception from proprioceptors such as
muscle spindles and...
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This note was uploaded on 01/29/2013 for the course BIOL 239 taught by Professor Swan during the Fall '12 term at New Mexico.
- Fall '12