Breaks down the ach attached to the receptors on the

Info icon This preview shows pages 47–59. Sign up to view the full content.

View Full Document Right Arrow Icon
Acetylcholinesterase breaks down the ACh attached to the receptors on the motor end plate so the muscle action potential will cease and the muscle cell will relax.
Image of page 47

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Pharmacology of the NMJ Botulinum toxin blocks release of neurotransmitter at the NMJ so muscle contraction can not occur bacteria found in improperly canned food death occurs from paralysis of the diaphragm Curare (plant poison from poison arrows) causes muscle paralysis by blocking the ACh receptors used to relax muscle during surgery Neostigmine (anticholinesterase agent) blocks removal of ACh from receptors so strengthens weak muscle contractions of myasthenia gravis also an antidote for curare after surgery is finished
Image of page 48
Twitch Contraction Brief contraction of all fibers in a motor unit in response to single action potential in its motor neuron electrical stimulation of the neuron or muscle fibers Myogram - graph of a twitch contraction the action potential lasts 1-2 msec the twitch contraction lasts from 20 to 200 msec
Image of page 49

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
SINGLE MUSCLE FIBER PHYSIOLOGY
Image of page 50
Myogram of a Twitch Contraction
Image of page 51

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
10_15
Image of page 52
Parts of a Twitch Contraction Latent Period - 2msec Ca+2 is being released from SR slack is being removed from elastic components Contraction Period 10 to 100 msec filaments slide past each other Relaxation Period 10 to 100 msec active transport of Ca+2 into SR Refractory Period muscle can not respond and has lost its excitability 5 msec for skeletal & 300 msec for cardiac muscle
Image of page 53

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Motor Unit Recruitment Motor units in a whole muscle fire asynchronously some fibers are active others are relaxed delays muscle fatigue so contraction can be sustained Produces smooth muscular contraction not series of jerky movements Precise movements require smaller contractions motor units must be smaller (less fibers/nerve) Large motor units are active when large tension is needed
Image of page 54
Atrophy and Hypertrophy Atrophy wasting away of muscles caused by disuse (disuse atrophy) or severing of the nerve supply (denervation atrophy) Hypertrophy increase in the diameter of muscle fibers resulting from very forceful, repetitive muscular activity and an increase in myofibrils, SR & mitochondria
Image of page 55

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Anabolic Steroids Similar to testosterone Increases muscle size, strength, and endurance Many very serious side effects liver cancer kidney damage heart disease mood swings facial hair & voice deepening in females atrophy of testicles & baldness in males
Image of page 56
Rigor Mortis Rigor mortis is a state of muscular rigidity that begins 3-4 hours after death and lasts about 24 hours After death, Ca+2 ions leak out of the SR and allow myosin heads to bind to actin Since ATP synthesis has ceased, crossbridges cannot detach from actin until proteolytic enzymes begin to digest the decomposing cells.
Image of page 57

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Abnormal Contractions Spasm - involuntary contraction of single muscle
Image of page 58
Image of page 59
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern