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