The senses and eye NS:

• Sclera = outer/fibrous layer, white and merges with the cornea.
• Uvea = middle/vascular layer with 3 regions - choroid, iris and ciliary body.
• Inner eye layer = retina is light sensitive using photoreceptors to the optical nerve.
• Field of vision = 270 degrees.
• Tapetum lucidum = reflector layer behind the retina.
• Pinna = outer layer of the ear, picks up sound waves to the auditory canal.
• Tympanic membrane = eardrum, end of the external auditory canal and vibrates sound waves.
• Tympanic cavity = middle ear, 3 bones which conduct sound vibration through the eardum.
• Inner ear = fluid passages which take the sound waves processed on the auditory nerves - sense of balance.
• Smell = olfaction.
• Olfactory membrane registers smell.
• Vomeronasal organ = hollow, tube-like structure with a mucous membrane beneath the nasal passage.
• Flehmen response = forces air in and curls the lip.
• Taste = sweet, savoury, bitter and sour.
• Tactile sensitivity to = pressure, pain, temperature and chemicals.
• Afferent = receive - sensory.
• Efferent = sends out - motor.
• Nociceptors = pain.
• Thermoreceptors = temperature.
• Mechanoreceptors = touch/sound.
• Chemoreceptors = chemicals.
• Proprioceptors = movement.
• -70mV = resting potential.
• Resting/polarised = positive K+ and negative anions, K+ leaks out which removes positive charge and makes the cell negative.
• Depolarisation = membrane becomes permeable to Na+ and becomes positive again.
• Na+ increases with impulses.
• Propagation = action potential is conducted along an axon.
• Synaptic transmission = release of NT, pre to post SK, generate electrical impulse and NT binds to receptors.
• Synaptic transmission order = 1. AP arrives, 2. Ca2+ enters the pre SK, 3. synaptic vesicles fuse with the presynaptic membrane, 4. acetylcholine diffuses into the cleft, 5. acetylcholine binds to receptors in the post SK, 6. Na+ enters the post SK and 7. AP is generated.
• Hearing = pinna, 180 degrees movement in both directions for communication.
• Auditory ossicles = malleus (hammer), incus (anvil) and stapes (stirrup).
• Eustachian tubes = maintenance of air press.
• Cochlea = converts sounds waves to nerve impulses.
• Semi-circular canals = endolymph with otoliths to inform movement.
• 25,000 taste buds.
• Muzzle is the most touch sensitive - whiskers.
• Excessive skin stimulus results in numbness.
• 300 degrees of vision.
• Sclera = tough layer protecting the eyeball.
• Cornea = transparent to let light in and is curved to reflect light.