muscle physiology

• Motor neurons, whose axons constitute the somatic nervous system, supply skeletal muscles and bring about movement. 
• ​What is the shape of a muscle cell or fiber?

  long and cylindrical
• How developed is the sarcoplasmic reticulum in cardiac muscle?​

  ​moderately developed
• A connection involving stimulation of the nerve supply to one muscle and simultaneous inhibition of the nerves to its antagonistic muscle is known as reciprocal innervation.


  true
• An action potential in a motor neuron is propagated to the terminal button.
• What plays a key role in mediating performance of fine, discrete, voluntary movements of the hands and fingers?

  corticospinal system
• A single power stroke pulls the thin filament inward only a small percentage of the total shortening distance.
• Smooth muscle cells are interconnected by gap junctions found in intercalated discs that join cells together.

  False
• ​What are the two major types of spontaneous depolarizations displayed by self-excitable cells?


  ​pacemaker potentials and slow-wave potentials
• What are the two types of fast-twitch muscle fibers?​

  oxidative and glycolytic
• A smooth muscle cell has many T tubules and well developed sarcoplasmic reticulum.

  false
• ​If the muscle fiber is stimulated so rapidly that it does not have a chance to relax at all between stimuli, a smooth, sustained contraction of maximal strength known as tetanus occurs.
• At the outer limits of a muscle’s length, it still can achieve about 80% of its maximal contraction strength.

  false
• A neuromuscular junction is always excitatory (an EPP), whereas a synapse may be excitatory (an EPSP) or inhibitory (an IPSP).
• How long does a single action potential in a skeletal muscle fiber last?​

  1 to 2 milliseconds
• For effective control of motor output, what two types of muscle proprioceptors are needed by the CNS?

  muscle spindles and Golgi tendon organs
• Unlike skeletal muscle cells, a single smooth muscle cell extends the full length of a muscle.


  false
• In an isokinetic contraction, the load remains constant as the muscle changes length.

  false
• ​Nerve and muscle cells do not come into direct contact at a neuromuscular junction.


  true
• The agonist curare irreversibly binds to the Ach receptor-channels on the motor end plate.


  false
• ​Which molecule binds ATP in order for muscle contraction to occur?

  myosin
• A single power stroke pulls the thin filament inward only a small percentage of the total shortening distance.
• Slow and fast fibers are interconvertible.​


  false
• How many skeletal muscles are there in the body?​

  about 600
• smooth muscle fibres:

  • line hollow organs and tubes
  • single nucleus
• smooth muscle is made up of 3 types of filaments:

  • Actin
  • Myosin
  • Intermediate Filaments
• smooth muscle:

  Myosin light chain wrapped around the neck of myosin and has to be phosphorylated in order for actin to bind.
• myosin light chain -> myosin head -> Cl enters cell -> binds to calmodulin -> activates myosin light chain kinase -> phosphorylates myosin head
• Multiunit smooth muscle:

  • neurogenic
  • phasic
• Single unit smooth muscle:

  • myogenic
  • gap junctions
  • phasic or tonic
  • unstable resting membrane potential