BSC 2086 1st Edition Lecture 2 Outline of Last Lecture I Afferent Division II Efferent Division III Somatic Nervous System IV General Senses V Special Senses VI Interpreting Sensory Information VII Receptors for General Senses Outline of Current Lecture I Major Sensory Pathways II Somatic Motor Pathways III Olfaction IV Gustation Current Lecture I Major Sensory Pathways a Somatic Sensory Pathways i Spinothalamic pathway goes from spinal cord to thalamus 1 Lateral path 2 Conscious sensation of crude touch pressure temperature and pain 3 Very hard to locate visceral pain can feel pain in an uninjured body part when then pain is actually coming from another location 4 Why II III a Stimulated interneurons at arriving segment of spinal cord can stimulate primary sensory cortex which leads to pain in a specific body part b Referred pain heart attack pain felt in left arm ii Spinocerebellar pathway goes from spinal cord to cerebellum 1 Lateral path 2 Proprioceptive information sent to cerebellum iii Posterior column pathway Dorsal side of spinal cord 1 Sensation of fine touch pressure vibration and proprioception Somatic Motor Pathways a Somatic Nervous System SNS i Also known as somatic motor system ii Contractions of skeletal muscles iii Processing and control 1 All pathways include series of synapses which affect one another 2 Upper motor neuron damage spastic paralysis a Muscles not in relaxed state 3 Lower motor neuron damage flaccid paralysis a Wheelchair bound can t move limbs at all 4 Homeostasis is kept short term through spinal and cranial reflexes a Prevents excessive damage to the body 5 Integrative centers in brain perform elaborate processing 6 Primary motor cortex is in charge of most complex motor activities a Neurons of PMC innervate motor neurons responsible for skeletal muscle stimulation 7 Higher centers in the brain either suppress or facilitate reflexes which can affect voluntary movements iv Amytrophic Lateral Sclerosis ALS A progressive degenerative disorder that affects motor neurons found in the brains stem spinal cord and cerebral hemisphere 1 Once these neurons die skeletal muscles stop being used which causes atrophy 2 Deterioration of skeletal muscles occurs b Autonomic Motor System ANS i Also known as visceral motor system ii Controls smooth and cardiac muscles as well as glands Olfaction a Olfactory organs found in nasal cavity i Olfactory epithelium 1 Olfactory receptor cells a Detect dissolved chemicals as they interact with odorant binding proteins on its cell membrane b Amount of receptors declines with age 2 Supporting cells 3 Basal cells stem cells that make new receptor cells IV ii Lamina propria 1 Olfactory glands a Form mucus which coat organs b Olfactory Pathways i Axons leave olfactory epithelium penetrate cribriform plate olfactory bulbs in cerebrum 1st synapse ii Axons leave olfactory bulb travel olfactory tract arrive at olfactory cortex hypothalamus and some parts of limbic system 1 Information arrives at information centers without synapsing in the thalamus first c Olfactory Discrimination i Able to distinguish thousands of chemical stimuli ii Smells interpreted by CNS based on the pattern of receptor activity Gustation a Taste Receptors i Found on tongue pharynx and larynx ii Taste buds clusters of taste receptors 1 Epithelial projections known as lingual papillae are found on superior surface of the tongue a 3 types i Filiform Papillae used for friction no taste buds ii Fungiform Papillae 5 taste buds each iii Circumvallate Papillae 100 taste buds each 2 Contain a Basal cells b Gustatory cells i Taste hairs extended through taste pore b Gustatory pathways i Cranial nerves monitor ii Synapse with medulla oblongata iii Then sent to thalamus and primary sensory cortex c Gustatory Discrimination i Four primary sensations sweet salty sour bitter ii Umami savory tastes 1 Sensitive to amino acids peptides nucleotides 2 Ex Beef broth and parmesan cheese iii Water is detected by specialized water receptors iv Chemicals will contact taste hairs and bind to receptor proteins 1 Salty and sour receptors are chemically gated a Depolarization of membrane causes release of neurotransmitters 2 Sweet bitter and umami stimuli will activate G protein by binding to receptor protein a Activation of G proteins will cause release of neurotransmitters d Taste Sensitivity i 1000x more sensitive to sour tastes ii 100x more sensitive to bitter tastes iii Why 1 Toxic things may be bitter and spoiled foods can be sour defense mechanism iv Taste buds decline rapidly by age 50
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