Neural Integration: Sensory/Motor Pathways; and Olfaction and Gustation Nestor T. Hilvano, M.D., M.P.H.

Learning Objectives 1.Identify the sensory receptors and basis of classifications. 2.Identify the major sensory and motor pathways that originate in different areas of the body. 3.Describe the sensory organ of smell and trace the olfactory pathway. 4.Discuss the physiological basis of olfactory discrimination. 5.Describe the sensory organ of taste and trace the gustatory pathway. 6.Explain the physiological basis of gustatory discrimination.

Sensory Receptors Specialized cells, which passes information to the CNS General senses - pain (nociceptors) - temperature (thermoreceptors) - touch - pressure mechanoreceptors - vibration - proprioception (proprioceptors) Special senses - smell and taste (chemoreceptors) - hearing - equilibrium - vision

Classification of Sensory Receptors Exteroceptors provide information about the external environment Interoceptors monitor visceral organs and functions Proprioceptors report the positions of skeletal muscles and joints

Referred Pain Visceral pain perceived as involving specific regions of the body surface innervated by the same spinal segment.

Motor Pathways Upper motor neuron (UMN) - in CNS a) Pyramidal tracts (UMN) - Corticospinal tracts - Corticobulbar tracts b) Extrapyramidal tracts - Vestibulospinal tract - Tectospinal tract - Reticulospinal tract - Rubrospinal tract Lower motor neuron (LMN) - in nucleus of brainstem or spinal cord Decorticate rigidity- lesion at cerebral hemispheres, above the red nucleus of midbrain; arms flexed, legs extended Decerebrate rigidity- lesion at brainstem; arms and legs extended

Smell ____________ is the sense of smell. Olfactory mucosa contains the receptor –highly sensitive; up to 10,000 odors –found on ____________________. a.Inferior nasal conchaeb. superior nasal conchae c. middle nasal conchae d. a and c only

Olfactory Epithelial Cells Olfactory cells –bind odor molecules –axons pass through the cribriform plate. –distinct sensitivity; survive 60 days Supporting cells Basal cells Olfactory glands What is the receptor cell of smell? a. bipolar cell b. sustentacular cell c. basal cell d. hair cells

Physiology of Smell Molecules bind to receptor on olfactory hair Activate G protein and cAMP system Opens ion channels for Na + or Ca 2+ –creates a receptor potential Action potential travels to brain Receptors adapt quickly What are the effects of aging process on ability to detect odors? __________

Olfactory Pathway Axons of Olfactory cells synapse in olfactory bulb. Output from bulb forms olfactory tract. end in primary olfactory cortex, called the Uncus. travel to hypothalamus and parts of limbic system related to ______, ___________, and ___________.

Taste ________ - is the sense of taste. ________ - receptors on tongue, parts of pharynx and larynx. Lingual papillae – filiform (for texture/friction), fungiform (at tips and sides), and circumvallate (at rear) of tongue

Physiology of Taste Molecules must dissolve in saliva 4 Primary taste sensations 1.Sweet = _______________. 2.Salty = ________________. 3.Sour = ________________. 4.Bitter = _______________. 5.Umami - taste of amino acids (MSG), beef/chicken broth Influenced by food texture, aroma, temperature, and appearance Hot pepper stimulates free nerve endings Aging (age 50)results to ______________.

Gustatory Pathway Innervation of taste buds - ant. 2/3’s of tongue = VII CN - post. 1/3 = IX CN - palate, pharynx, epiglottis = X CN To solitary nucleus in medulla To thalamus Then sensory cortex (area 43) * hypothalamus and amygdala - activate autonomic reflexes e.g. salivation, gagging and vomiting

Homework (Self-Review) 1.Define key terminologies: homunculus, olfaction, gustation, adaptation, nociceptor, proprioceptor, referred pain, decorticate rigidity, decerebrate rigidity, uncus, and bowman’s gland. 2.Identify receptor of: a) gustation, b) olfaction, c) angular movement, d) linear acceleration 3.Identify the function of: a) dorsal column (fasciculus gracilis and fasciculus cuneatus) pathway, b) spinocerebellar tracts, c) lateral spinothalamic tract, d) anterior spinothalamic tract 4.Identify the function/s of the following tracts: lateral and anterior spinothalamic, fasciculus gracilis and fasciculus cuneatus, and corticospinal tract. 5.Trace the pathway of smell from olfactory bulb to cortex. 6.Trace the pathway of taste from the taste buds to cortex.