MOVEMENT ch8 Types of Muscles 02 28 2013 Smooth internal organs Skeletal striated voluntary muscles for body movement Cardiac heart intermediate Neuromuscular Junction Synapse where motor neuron axon meets a muscle fiber Acetylcholine in skeletal muscles excites muscles to contract Axon innervates 1 muscle fibers o Eye muscles 1 axon 3 fibers o Biceps 1 axon 100 fibers Proprioceptors Receptor that detects position or movement of a part of the body Detect stretch muscle spindle or tension Golgi tendon organ of a muscle sends signals to SC SC sends reflex signal to contract or relax the muscle Muscle Spindle Parallel to muscle Responds to stretch Muscle stretches receptor stretches didn t finish Golgi Tendon Organ In tendons at opposite ends of muscles Responds to increase in muscle tension during a contraction message to SC inhibition of motor neurons via interneurons Vigorous contraction inhibits further contraction Flexor withdrawal reflex Initiated by cutaneous receptors Tonic inhibition o Descending influences coming down from brain that damp this reflex down so that only something strong or painful and activate it Full limb involvement o Primary afferents bifurcate o Includes interneurons Modified based on location of stimulus Crossed effects Infant Reflexes Grasping Babinski o Something touches baby they grab it o Stroke the bottom of baby s foot with a bit of force its toes o Edge of babies mouth is touched they look around to look for flare out Rooting a food source Inhibited by cortex in adults Sequences of Behavior Central pattern generators o Neural mechanisms that generate rhythmic patters of motor output o Elicited by stimulus frequency determined by spinal cord cells o Flapping wings wet dog shake find movement in fish o Spinal cord Motor Program o Fixed sequence of movements o Learned or programmed Learned sports typing piano playing Programmed grooming mice yawning w stretch and inhalation exhalation pattern smiling frowning o Automatic If think about it mess it up o Spinal cord brainstem cerebellum Control of Movement by Cortex The motor homunculus o Gives most devotion to face hands feet Primary motor cortex contains upper motor neurons o Aka precentral gyrus in frontal lobe Motor control distributed over population of cells Active even when imagining movement Left side of cortex controls right side of body Corticospinal tract why one side controls opposite side for voluntary movement Mostly from primary motor cortex Most decussates crosses in medulla o Lateral CST Synapses on lower motor neurons in spinal cord ventral anterior horn Voluntary movements Motor cortex to ventral anterior horn of spinal cord Lateral CST o Terminates in Contralateral spinal cord o Controls distal limbs o Pyramidal tract What feeds into primary motor cortex Supplementary motor cortex o For sequences of movements Premotor cortex o For imitating movements mirror neurons Parietal frontal and temporal association cortices what and where from visual auditory and somatosensation perception of space in general o Another important connection primary Somatosensory cortex Body part correlates between the two cortices From motor cortex to Spinal cord o Voluntary movement CST o Central pattern generators o Modulation of reflexes Brainstem o Motor cranial nerves Cerebellum Motor control o Balance and coordination o Postural control Also important connections with basal ganglia and cerebellum o Feedback for later control o Learned motor responses and skills o Rapid ballistic movements that require accurate aim and o Ex tapping a rhythm speaking typing writing athletics timing music eye movements Cognition attention Timing sensory as well as movement Organization of cerebellum o Inputs indirect from spinal cord cortex vestibular system etc cerebellar cortex deep cerebellar nuclei output targets eventually including motor cortex Basal Ganglia Pathways from cortex through bg back to cortex to inhibit or facilitate cortical activity Cortex basal ganglia and thalamus Caudate putamen globus pallidus substantia nigra subthalamic nucleus End of result facilitation or suppression of cortical activity Problems with regions of basal ganglia movement disturbances and cognitive emotional disturbances Parkinson s Disease Occurs when the dopamine producing cells that live in substantia nigra and project to striatum are destroyed Normally dopamine in basal ganglia helps facilitate cortex and Without dopamine too much inhibition of thalamus too much Rigidity slowness difficulty initiating movement resting tremor thus movement inhibition of cortex postural instability Huntington s Disease a fatal inherited disorder that causes degeneration of the caudate chromosome 4 repeated sequences that code for glutamine nucleus and putamen more repeats earlier onset characterized by uncontrollable jerking movements and dementia not enough inhibition of thalamus so too much activity in cortex Circadian rhythms rhythms that last about a day humans last 02 28 2013 Circadian Rhythms Endogenous Rhythms around 24 2 hours o Waking and sleeping o Hormone secretion o Urine production o Eating and drinking o Sensitivity to drugs Age is important factor o People around 20 year old most likely to go to bed late and o This is not just learned rates show a similar change across wake up late the lifespan Older rats reach best performance shortly after awakening younger adolescent rats improve performance as day goes on Why To prepare for changes in environment before they occur o Sunrise sunset o Temperature changes day to night and seasonal Endogenous circannual rhythm 1 year rhythm hibernations migrations a stimulus that resets the biological clock o circadian rhythms persis without light free running but Zeitgeber light can reset them examples o temperature o exercise o noise o meals o bright light Jet Lag time Problem is that our endogenous rhythm doesn t match external Easier to travel West stay up later than normal and sleep in than East have to go to bed early and wake up early Flight attendants on long trips across several time zones for more than 5 years o Smaller than average hippocampus adjusting to jet lag is stressful and stress increases stress hormones and these can be toxic to the hippocampus especially o Some memory impairment Shift Work people who work out of synch with regular sleep wake cycle Duration of sleep depends on when go to bed sleep less if go to bed in morning or afternoon For those who work night shift try to
View Full Document
Unlocking...