NROSCI 0080 1st Edition Exam 2 Study Guide Control of Movement Many brain and spinal regions are involved ALL skeletal motor neurons o Have their cell bodies in the CNS Brainstem spinal cord ventral horn o Axon projects to the periphery o Axon terminal is on the muscle fiber Neuromuscular Junction NMJ ACh Somatic Skeletal Voluntary Facial nerves are located in the medulla and are cranial nerves Signaling at the NMJ ACh Depolarization EPSP Contraction o This is the opposite in cardiac muscle Stimulation of the Vagus Nerve releases ACh causing hyperpolarization IPSP leading to slowing down of the heart Excess ACh is removed from the NMJ via enzymatic degradation o AChE Drugs Chemicals can influence motor control o Agonists mimic NTs Snake venoms black widow spider venom Cause tonic contraction o Antagonists block reduce effects of NT Curare botulism Cause tonic relaxation Motor neurons still release ACh but it can t bind because the toxin is already at the receptive sites Simple Motor Reflexes Stretch Reflex patellar tendon is stretched causing the quadriceps muscle to contract kicking the lower leg outward o Monosynaptic Pain Withdrawal Reflex nociceptive stimulation causes you to remove the area in the noxious stimulus before you re consciously aware of any pain o Polysynaptic involved interneurons The antagonizing muscle is also contacted via an inhibitory neuron to complete the movement of opposing contraction relaxation o Can also be very complex when in the leg because you have to maintain postural balance while quickly withdrawing the leg Neural Control of Movement Motor pathways are descending convergent hierarchical circuits Frontal Lobe Pre Central Gyrus primary motor cortex Brainstem Spinal Cord Skeletal Muscles Primary Motor Cortex o Pyramidal neurons synapse with cells in the medulla face mouth neck or ventral horn all other muscles o Contains a motor homunculus Cerebellum o Extra processing center for more sophisticated movements o Parallel processing o Receives proprioceptive feedback from muscles o Overall effect smoothing movement Alcohol targets the cerebellum so when intoxicated movements aren t smooth or accurately executed Field sobriety tests o Maintains skilled coordinated movements that are voluntarily initiated but reflexively maintained Motor Programs o Damage Decomposition of Movement Syndrome o Prism glasses experiment Animals with damage to the premotor cortex can t put motor sequences together Lecture 9 Basal Ganglia collection of subcortical nuclei within the forebrain receives constant input concerning the state of activity of the motor cortex o Striatum o Caudate putamen globus pallidus o Initiating and terminating voluntary movements o Cortex Basal Ganglia Cortex via Thalamus o Direct Inhibitory Pathway leads to amplified force of movement o Indirect Excitatory Pathway leads to reduced force of movement o Receives input from the Substantia Nigra Substantia Nigra o Releases dopamine via the nigrostriatal projection Excitatory Parkinson s Disease loss of dopaminergic neurons in the substantia nigra o Positive symptoms Rigidity Resting tremors Involuntary movements o Negative Symptoms Poor balance Akinesia Bradykinesia no slow movement Struggle to initiate movements Speech problems o Bad batch of heroin in the 80 s MPTP highly toxic to dopaminergic neurons in substantia nigra o Treatment L DOPA precursor that has the ability to cross the blood brain barrier physical therapy deep brain stimulation Lecture 10 Sensation and Perception Sensation uses divergent ascending hierarchical pathways Local circuit neurons provide additional levels of processing at each level Information from each sensory receptor remains segregated from other senses throughout the entire perception process Events must pass through four levels of our nervous system o Stimulus detector units Physical events chemical cellular signals Sensory Transduction Each sense has a different SDU The retina for vision is the only SDU that s a part of the CNS Encode for time intensity and location of stimulus o Initial receiving centers In the visual system the retina is also the initial receiving center For somatosensation the receiving center is somewhere in the spinal cord or medulla depending on the original location of stimulus Olfactory bulb for sense of smell Medulla for everywhere else o Integrating centers Integration of different modalities of sensation to help form an entire picture Thalamus EXCEPT OLFACTION goes directly to limbic cortex o Perception Conscious awareness Primary sensory cortex Vision occipital lobe Hearing temporal lobe Touch parietal lobe Taste temporal lobe Olfaction temporal lobe Balance only reaches conscious awareness when it is disrupted There is also a sensory homunculus in the parietal lobe Receptive field region of space in which a stimulus will alter the firing of that neuron Lecture 11 Pain Nociception Nociceptive information crosses over to the contralateral side of the spinal cord before ascending to the brain Nociceptors are subsets of mechanical chemical and thermoreceptors Unmyelinated Referred pain pain in the viscera is perceived to be coming from elsewhere o Visceral afferents synapse onto the nociceptive fibers from a nearby somatic area Nociceptors become increasingly sensitive with continued stimulation o Due to presence of prostaglandins o Light touch to a sunburn vs unaffected skin Congenital Insensitivity to Pain born without nociceptors o Can still feel touch just not pain o Evolutionary disadvantage high risk of infection burns etc Nociceptors enter the spinal cord and divide into 3 branches which each synapse onto different afferents o Important for pain withdrawal reflex o Fast pain Pain location and intensity o Slow pain Emotional component via hypothalamus limbic system prefrontal association cortex They ALL release Substance P which is distinctive from all other receptors The Gate Control Theory Non pain signals can effectively blunt the perception of pain o You hit your head so you rub around it Closing a spinal gate Inhibitory interneurons o Release endorphin endorphins make people happy Endorphin agonists block emotional pain reactions Endorphin antagonists enhance emotional pain reactions Endorphins can also be released by neurons in higher brain centers that can also affect pain transmission Endorphins do not influence the fast pathway o Evolutionary advantage we need to know when our bodies are in danger Acupuncture induces the