03-21_motor - BIOLOGY 325H Motor systems March 21, 2008...

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BIOLOGY 325H Motor systems March 21, 2008 Animals interact with their environment through their behavior, and the overt manifestation of that behavior is motor activity. A motor system consists of the motor neurons of the nervous system, and the effector organs which respond to those neural signals. We will focus here on the muscular activity that results in behaviors such as locomotion, grasping, and biting. However, one should note that motor output of the nervous system can control a variety of other, more exotic effector organs such as the involuntary contraction of smooth muscles, neurally stimulated glandular secretion, changes in pigment cells, and - in species like the electric eel - the generation of powerful electric fields that can shock either predators or prey. Motor systems are remarkable for the finely tuned timing and coordination of the output. Consider the navigational skills of a bat, which uses echolocation to identify a flying moth and manages to successfully catch its prey despite the moth’s evasive tactics. Or the ability of a chameleon or frog to shoot out its tongue and precisely hit a insect a foot away. No less amazing is the ability of human athletes to hit 100 mph fastballs or to dance ballet. Any discussion of motor systems must also include the skeleton, an organ system that transmits the force of muscle contraction to the remainder of the body and whose structure shapes the movements produced by those contractions. Learning goals 1. What is the neuromuscular junction? What effect does a single EPSP have at the neuromuscular junction of a skeletal muscle fiber (= cell)? What is the effect of many, rapidly delivered action potentials in the motor neuron? In what two ways can the nervous system control the strength of a given muscles contraction? 2. What is a reflex? How are reflexes distinguished from other movements?
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03-21_motor - BIOLOGY 325H Motor systems March 21, 2008...

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