Intro B B Exam 4 3 30 15 CHAPTER 8 STUDY HINTS 1 There are three types of muscles smooth skeletal striated and cardiac Where is each located Smooth internal organs control the digestive system and other organs Skeletal Striated voluntary muscles for body control movement of the body in relation to the environment Cardiac heart intermediate heart muscles that have properties of skeletal and smooth muscles 2 What is the neuromuscular junction What transmitter is released from the neuron onto skeletal muscles to cause contraction How many muscle fibers does a single neuron innervate and what does this mean for motion precision Neuromuscular junction a synapse where a motor neuron axon meets a muscle fiber Acetylcholine excites muscle to contract in skeletal muscles Axon innervates 1 muscle fibers Eye muscles 1 axon 3 fibers Biceps 1 axon 100 fibers 3 Remember muscles always contract or relax but never actively move in the opposite direction The ability to bend straighten your arm for example is due to opposing sets of antagonistic muscles flexor and extensor muscle Movement requires the alternating contraction of opposing sets of muscles called antagonistic muscles A flexor muscle is one that flexes or raises an appendage An extensor muscle is one that extends an appendage or straightens it 3 Define proprioception What is the Golgi tendon organ Muscle spindle Proprioception receptors that detect the position or movement of a part of the body fluidity depends on proprioception Muscle spindles are proprioceptors parallel to the muscle that responds to a stretch causes a contraction of the muscle Stretch reflex occurs when muscle proprioceptors detect the stretch and tension of a muscle and send messages to the spinal cord to contract it Golgi tendon organ type of proprioceptor in tendons at the opposite end of muscles Responds to increase in muscle tension during a contraction message to SC inhibition of motor neurons via interneuron s Vigorous contraction inhibits further contraction QuickTime and a decompressor are needed to see this picture Muscle Spindle type of proprioceptor parallel to muscle Responds to stretch muscle stretches receptor stretches message to SC message back to muscle fiber to contract Knee jerk reflex 4 What is the difference between fast twitch and slow twitch fibers Which are aerobic Anaerobic Skeletal muscle types range from Fast twitch fibers fibers produce fast contractions but fatigue rapidly Slow twitch fibers fibers produce less vigorous contraction without fatigue People have varying percentage of fast twitch and slow twitch muscles Aerobic slow twitch fibers are aerobic and require oxygen during movement and therefore do not fatigue Non strenuous activities utilize slow twitch and intermediate fibers Anaerobic fast twitch fibers are anaerobic and use reactions that do not require oxygen resulting in fatigue Behaviors requiring quick movements utilize fast twitch fibers 5 What are some reflexes that are present in children but inhibit adults Reflexes are involuntary consistent and automatic responses to stimuli Infants have several reflexes not seen in adults Grasp reflex grasps objects placed in the hand Babinski reflex extends big toe and fans others when the sole of the foot is stroked Rooting reflex turns head and sucks when cheek is stimulated 6 What 3 areas of the cortical motor areas actively prepare for movements Sending information to primary cortex instigates the movement Posterior parietal cortex o Keeps track of body relative to world o Neurons respond to stimulus response or both 1 Prefrontal cortex Responds to lights noises other sensory signals 2 Premotor cortex Active during prep for a movement and during movement itself Gets info on location of target current body position 3 Supplementary motor cortex Most active just before rapid series of movements All 3 of these areas actively prepare for movements sending information to primary motor cortex instigates the movement 7 When the motor cortex sends a signal to the periphery to cause movement it travels down the corticospinal tract AKA dorsolateral tract The cell bodies of the upper motor neurons UMN are in the motor cortex but the axon from an UMN descends via the brain stem and crosses over in the medulla to the other side of the body and then continue down the spinal cord until the UMN synapses on the lower motor neuron LMN or an interneuron in the spinal cord on the contralateral side from the motor cortex that sent the original signal This is how the motor cortex on one side controls the movements for the contralateral side of the body 8 The cerebellum and the basal ganglia among others are involved in movement How Know the sub structures of each and the role the major rolls the basal ganglia and cerebellum play in movement i e what would damage to these structures disrupt Also review the structure and design of the Purkinje cells and parallel fibers in the cerebellar cortex Basal ganglia Feedback for later control Motor cranial nerves o Brainstem o Spinal cord Voluntary movement Central pattern generators Reflexes 3 sub structures of the basal ganglia caudate nucleus putamen and globus pallidus Damage to the basal ganglia movement disturbances and cognitive emotional disturbances Cerebellum The cerebellum is a structure in the brain often associated with balance and coordination o More neurons in the cerebellum than in all other brain areas combined o Damage to the cerebellum causes trouble with rapid movements requiring aim timing o Examples clapping hands speaking writing etc o Studies suggest that the cerebellum is important for the establishment of new motor programs that allow the execution of a sequence of actions as a whole Important for tasks that require timing o The cerebellum also seems critical for certain aspects of attention such as the ability to shift attention and attend to visual stimuli Cerebellar structure and Pathways The cerebellar cortex is the surface of the cerebellum Parallel fibers Purkinje cells excite Purkinje cells transmit inhibitory messages to the cells in the nuclei of the cerebellum clusters of cell bodies in the interior of the cerebellum and the vestibular nuclei in the brain stem Messages then sent to the midbrain and the thalamus 9 We talked about several movement disorders Be able to answer questions about myasthenia gravis Parkinson s disease and Huntington s disease in terms of symptoms and treatments Myasthenia gravis autoimmune disease
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