EC

anatomy lecture apr 22

Exteroceptors

  • Definition: Detect external stimuli from the environment.
  • Examples:
    • Touch receptors on skin.
    • Temperature receptors on skin.
    • Special senses including vision, hearing, taste, and smell.

Interoceptors

  • Definition: Monitor internal conditions of the body.
  • Functions: Measure gas levels (O2, CO2), blood glucose, and other variables in blood.
  • Location: Found within the body, often related to the internal environment.

Proprioceptors

  • Definition: Sense body position and movement in space.
  • Examples:
    • Muscle spindles detect stretch.
    • Golgi tendon organs monitor tension in tendons.

Classification Based on Stimulus Type

  • Mechanoreceptors: Respond to mechanical pressure or distortion (pressure, vibration).
  • Thermoreceptors: Sense temperature changes.
    • Divided into cold receptors (active under 50°F) and warm receptors (active above 50°F).
  • Nociceptors: Pain receptors, always free nerve endings.
  • Photoreceptors: Located in the retina (rods and cones), respond to light.
  • Chemoreceptors: Respond to chemical stimuli (e.g., taste, smell).
  • Osmoreceptors: Monitor osmolarity (particle concentration) in blood.

Taste (Gustation)

  • Definition: Chemical sense of taste.
  • Taste Buds: Four types of papillae contain gustatory cells (taste receptors).
    • Circumvallate papillae: Bitter taste at the back of the tongue.
    • Fungiform papillae: Sweet & salty taste at the front of the tongue.
    • Foliate papillae: Sour taste on the sides.
  • Innervation:
    • Anterior 2/3: Cranial Nerve VII (Facial Nerve).
    • Posterior 1/3: Cranial Nerve IX (Glossopharyngeal Nerve).
    • Epiglottis and pharynx: Cranial Nerve X (Vagus Nerve).
  • Flavor vs. Taste: Flavor is a combination of taste, smell, and tactile sensations.

Olfactory System (Smell)

  • Olfactory Receptors: Bipolar neurons with cilia (olfactory hairs).
  • Chemoreceptors: Respond to odorant molecules.
  • Pathway: Odorant molecules -> olfactory receptors -> olfactory bulb -> olfactory tract -> temporal lobe (primary olfactory cortex).
  • Emotional Response: Smell can elicit memories and emotions through connections with the limbic system.

Auditory System (Hearing)

  • Division of Ear:
    • External Ear: Pinna (auricle) to tympanic membrane.
    • Middle Ear: Contains ossicles - malleus, incus, stapes, and Eustachian tube.
    • Inner Ear: Cochlea and vestibule involved in hearing and balance.
  • Hearing Pathway:
    • Sound waves -> Tympanic membrane vibrations -> Ossicles amplify vibrations -> Cochlea converts vibrations to electrical signals.
    • Pathway to brain via cochlear nerve -> superior olivary nucleus -> inferior colliculus -> thalamus -> auditory cortex (temporal lobe).
  • Audible Range: 20 Hz to 20,000