PSB2000 Brain Behavior Exam 4 Study Guide Chapter 8 1 8 3 Movement 3 Types of Muscles control the digestive system and other organs located in the controls the movement of the body in relation to the o Smooth Muscles intestines and other organs o Skeletal Striated Muscles environment located attached to bones muscles located in the heart o Cardiac Muscles heart muscles that have properties of skeletal and smooth Neuromuscular Junction A synapse between a motor neuron axon and a muscle fiber o In skeletal muscles every axon releases acetylcholine at the neuromuscular junction and acetylcholine always excites the muscle to contract o Axon innervates 1 Eye muscles 1 Axon 3 fibers Biceps 1 Axon 100 fibers Each muscle makes just one movement contraction It relaxes in the absence of excitation but it never moves actively in the opposite direction o Ex The ability to bend straighten your arm is due to opposing sets of antagonistic muscles flexor and extensor muscles Antagonistic Muscles pairs of muscles that move a limb in the opposite direction appendage Flexor Muscles muscle that flexes a limb flexes or raises an Extensor Muscles muscle that extends a limb extends an appendage or straightens it Proprioceptors receptors that detect the stretch and tension of a muscle and send messages that enable the spinal cord to adjust its signals when the muscle is stretched the spinal cord sends a reflexive signal to contract it o Golgi Tendon Organs type of proprioceptor that responds to increases in muscles tension located in the tendons at opposite ends of a muscle they act as a brake against an excessively vigorous contraction vigorous contraction inhibits further contraction Responds to increase in muscle tension during a contraction sends message to Spinal Cord inhibition of motor neurons via interneurons another proprioceptor parallel to the muscles that responds to a o Muscle Spindle stretch Muscle stretches receptor stretches sends messages to Spinal Cord receives message back to muscle fiber to contract Ex knee jerk reflex Slow Twitch Fibers are aerobic and require oxygen during movement and therefore do not fatigue Fast Twitch Fibers resulting in fatigue o Non strenuous activities utilize slow twitch and intermediate fibers are anaerobic and use reactions that do not require oxygen o Behaviors requiring quick movements utilize fast twitch fibers What are some reflexes that are present in children but inhibited in adults grasps objects placed in hand extends big toe and fans others when the sole of the foot is o Grasp Reflex o Babinski Reflex stroked o Rooting Reflex turns head and sucks when cheek is stimulated 3 Areas of the Cortical Motor Areas that actively prepare for movements sending information to primary motor cortex instigates the movement o Premotor Cortex o Prefrontal Cortex responds to lights noises and other sensory signals also plans active during preparations for a movement and during movements according to their probable outcomes movement itself receives information about the target to which the body is directing its movement as well as information about the body s current position and posture most active just before rapid series of movements important for planning and organizing a rapid sequence of movements in a particular order becomes active during the second or two prior to a movement o Supplementary Cortex 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 The Cerebellum Basal Ganglia in Movement o The Cerebellum is a structure in the brain often associated with balance and coordination More neurons in the cerebellum than in all other brain areas combined 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 The cerebellum also seems critical for certain aspects of attention such as the ability to shift attention and attend to visual stimuli Damage to the cerebellum causes trouble with rapid movements requiring aim timing Ex Clapping hands speaking writing etc o Cerebellar Structure Pathways Cerebellar Cortex Purkinje Cells to one another Parallel Fibers planes of the Purkinje cells the surface of the cerebellum flat two dimensional cells in sequential planes parallel are axons parallel to one another and perpendicular to the Action potentials in parallel fibers excite one Purkinje cell after another Each Purkinje cell then transmits an inhibitory message to cells in the nuclei of the cerebellum clusters of cell bodies in the interior of the cerebellum and the vestibular nuclei n in the brainstem which in turn send information to the midbrain and the thalamus o The Basal Ganglia a group of large subcortical structures in the forebrain responsible for initiating an action not guided by a stimulus selects a movement by ceasing to inhibit it this circuit is particularly important for self initiated behaviors feedback for later control Comprised of the following structures Caudate Nucleus Putamen Globus Pallidus Input comes to the caudate nucleus and putamen mostly from the cerebral cortex Output from the caudate nucleus and putamen goes to the Globus Pallidus and from there mainly to the thalamus which relays it to the cerebral cortex especially its motor areas and the prefrontal cortex Problems with regions of basal ganglia movement disturbances cognitive emotional disturbances Movement Disorders o Myasthenia Gravis Immune system attacks acetylcholine receptors at NMJs Autoimmune disease Rapid muscle fatigue Begins in face Eventually can affect muscles used for breathing Treated with immune suppressants or acetylcholinesterase inhibitors o Parkinson s Disease Loss of dopaminergic cells in substantia nigra Rigidity muscle tremors slow movement difficulty initiating physical or mental activity impaired at initiating spontaneous movements in the absence of
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