Exam 4 Study Guide

• Free nerve ending


  A neuron that has a dendrite, with dendrites embedded in receiving tissue - pain and temperature receptors in the dermis
• Encapsulated ending


  A neuron that has an encapsulated ending in which the sensory nerve endings are encapsulated in connective tissue (enhances their sensitivity) - lamellated corpuscles in the dermis respond to pressure and touch
• Specialized receptor cell


  A neuron that has distinct structural components that interpret a specific type of stimulus - photoreceptors in retina that respond to light stimuli
• Locational classifications of receptors

  • Exteroceptors - provide information about the external environment
  • Proprioceptors - report the positions of skeletal muscles and joints (position of moving tissue)
  • Interoceptors - monitor visceral organs and functions
• Stimuli and receptor that detects it

  • Nociceptors - chemicals from tissue damage
  • Thermoreceptors - above (heat) or below (cold) normal body temperature
  • Mechanoreceptors - physical distortion: pressure, vibration, sound, and body position (balance)
  • Chemoreceptors - chemical concentration ex. taste or smell
  • Osmoreceptors - solute concentration
• Filiform papilla


  Doesn't contain taste buds but functions to move food around
• Gustatory cells are sensitive to the chemicals contained within foods that are ingested, and they release neurotransmitters based on the amount of the chemical in the food - signals are sent in 3 cranial nerves


  • Facial nerve (CN VII)
  • Vagus nerve (CN X)
  • Glossopharyngeal nerve (CN IX)
• Salty


  Perception of Na+ in the saliva
• Sour


  Perception of H+ concentration in saliva/food
• Sweet


  Glucose and other monosaccharides dissolved in saliva transduction through g-protein coupled receptors
• Bitter


  Alkaloids contain nitrogen and are commonly found in coffee, hops, tannins, teas, aspirin; can hyperpolarize or depolarize gustatory cells depending on which molecule binds to the receptor
• Umami/savory


  Receptor is activated by amino acid L-glutamate, so perceived by eating protein-rich foods
• Olfactory epithelium


  An area of the superior nasal cavity containing bipolar sensory neurons
• Odorant


  Molecules that bind to proteins that keep them dissolved in the mucus as we breath in; from there they are transported to the olfactory dendrites
• Smell is the only sensory information that reaches the cortex directly (others go through the thalamus)


  Smells can trigger profound emotional and behavioral responses, as well as memories due to the fact that olfactory information is also distributed to the limbic system and hypothalamus
• Olfactory neurons


  Regularly replaced within the nasal epithelium, after which the axons of the new neurons must find their appropriate connections in the olfactory bulb. These new axons grow along the axons that are already in place in the cranial nerve (Olfactory CN I)
• Eustacian Tube


  Normally closed, but during swallowing and yawning will open to help equalize pressure in the middle ear cavity
• Otitis media


  Middle ear infections that can occur when the Eustacian Tube allows microorganisms to travel from the nasopharynx into the middle ear
• Order the 3 bones in ear from ear drum to oval window

  • malleus
  • incus
  • stapes
• Organs of Corti


  Cochlear duct houses the mechanoreceptors called hair cells and a tectorial membrane
• Chambers of the cochlea


  • Scala vestibula
  • Scala tympani
• Movements of the oval window


  Cause fluid-pressure waves in the scala vestibula
• Pressure waves travel through the cochlea towards the round window


  Deform the walls of the scala vestibula and the scala tympani, collectively causing the basilar membrane to move
• Tectorial membrane


  Vibrations of the basilar membrane cause the hair cells (hair-like stereocilia extending from the cell's apical surfaces) to move against the tectorial membrane
• Vestibulocochlear (CN VIII) nerve


  Carries the nerve impulse generated by the bending of the hair cells against the tectorial membrane to the CNS
• Vestibule


  A central, egg-shaped cavity that houses receptors for static equilibrium or linear movements such as acceleration, deceleration and head position relative to gravity
• Utricle


  A slightly larger duct located at the top of the vestibule
• Saccule


  A small duct located at the bottom of the vestibule
• Maculae


  Hair cells of the saccule and utricles are clustered in oval structures called the maculae (Hair cells possess 80-100 stereocilia)
• Otoliths


  Densely packed calcium carbonate crystals in the gelatinous mass overlying the hair cells in the saccule and utricle
• Otolithic membrane


  The whole complex of the gelatinous mass and otoliths
• Semicircular Canals/ducts


  Three ring-like extensions of the vestibule that contain the receptors for dynamic equilibrium or the rotational movements of the head
• Ampulla


  Contains the receptors for dynamic equilibrium at the base of the anterior, posterior, and lateral semicircular canals
• Crista


  Tuft of hair cells in the ampulla whose microvilli are embedded in the gelatinous cupula
• Semicircular ducts and the rotational movements they detect


  • Horizontal/lateral - horizontal rotation, as in shaking the head "no"
  • Anterior - nodding the head "yes"
  • Posterior/superior - tilting your head side to side
• Direction each eye muscle moves the eyes


  • Lateral rectus - abduction
  • Medial rectus - adduction
  • Superior rectus - UP and IN
  • Inferior oblique - UP and OUT
  • Inferior rectus - DOWN and IN
  • Superior oblique - DOWN and OUT
• Nerves that innervate each eye muscle


  • Abducens nerve (CN VI) - Lateral rectus
  • Trochlear nerve (CN IV) - Superior oblique
  • Oculomotor Nerve (CN III) - Inferior rectus, Inferior Oblique, Medial Rectus
• Order the flow of information through the cells of the retina

  • Photoreceptors (rods/cones) - change membrane potential when stimulated by light energy
  • Bipolar cells - connect to the retinal ganglion cell (in the inner synaptic layer)
  • Amacrine cells - contribute to retinal processing before AP is produced by the RGC
  • Retinal Ganglion cell - axons lie at the innermost layer of the retina and collect at the optic disc, leaving the eye as the Optic (CN II) nerve
• Inner segment


  Contains the nucleus and other common organelles of a photoreceptor cell
• Rhodopsin


  Photosensitive pigment contained in the stacked membrane-bound discs of rod photoreceptors