Special senses Flashcards
define senses:
physiological capacities within organisms that provide inputs for perception
list traditional senses:
sight, hearing, touch, smell, taste
define exteroceptive senses and eg:
specialised organs devoted to the sense
- olfaction (smell)
- gustation (taste)
- vision (sight)
- audition (hearing)
- equilibrioception (balance)
list special visceral afferents
olfaction, gustation
list special somatic afferents
vision, audition, equilibrioception
special sensory receptors: cold stimulus
- unipolar neuron
- free nerve ending of dendrites
special sensory receptors: pressure stimulus
- unipolar neuron
- encapsulated nerve ending
- protect nerve
special sensory receptors: sugar molcule
taste receptor synapses with unipolar neuron
list olfactory cells:
- olfactory receptor cells
- supporting cells
- basal cells
olfactory receptor cell features:
- bipolar neurons with cilia projecting from dendrite
- respond to chemical stimulation of odorant molecule
olfactory epithelium: supporting and basal cells features
support: support and nourishment
basal: stem cells which replace olfactory receptors
where is olfactory epithelium found:
upper nasal cavity: superior nasal conchae, upper septum
olfactory pathway:
scent -> olfactory epithelium -> dissolves -> moves upwards through ethmoid bone -> olfactory bulb -> neuron -> olfactory tract -> olf nerve -> brain -> synapse in different places (limbic system) such as memory
- frontal lobe for odour identification
gustation: traditional types of taste and features
- bitterness: contains N and alkaloids
- saltiness (Na, K, Li)
- sweet (sugars, glycols, alcohols, aldehydes, ketones, esters, some amino acids)
- umami (glutamic acid)
- sourness (acids, H)
taste buds: list epithelial cells
- gustatory receptor cells
- supporting cells
- basal cells
general features of gustatory receptor cell:
each GRC has gustatory hair, projects through taste pore (lil ditch)
list 4 types of papillae
circumvallate, foliate, fungiform, filiform
circumvallate and foliate papillae features:
circumvallate:
- in V shaped row back of tongue
- 100-300 taste buds each
foliate:
- small trenches side of tongue
- degenerate in childhood
fungifom and filiform papillae features:
fungiform:
- scattered all over
- 5 taste buds each
filiform:
- tactile receptors
- no taste buds
- hot cold sensation
gustatory pathway:
- anterior 2/3 of tongue: facial nerve (taste)
- posterior 1/3: glossopharyngeal nerve
- anterior 2/3 tongue: trigeminal (taste sensation)
components of middle ear:
- tympanic membrane
ossicles:
- malleus
- incus
- stapes
components of inner ear;
- cochlea
- round and oval window
- vestibular
components of outer ear:
- auricle
- external auditory canal
audition features:
- passage of vibrational energy from one medium (air) to another (perilymph) in cochlear
- converts mechanical energy -> electrical energy (action potentials)
- transduction: chemical/physical signal which is transmitted through a cell
- these action potentials are to be interpreted in the brain
auditory pathway:
sound stimulus -> tympanic membrane -> ossicles -> oval window: perilymph -> vibrates Organ of Corti -> tectorial membrane -> cochlear branch of vestibulocochlear -> brain -> auditory area, cerebral cortex
- for reflex to loud sound
ear muscle features:
tensor tympani muscle and stapedius muscle
- help absorb excess loud sounds -> prevent damage
equilibrioception: features
sense of balance or vestibular sense
- allows organism to sense body movement, direction, acceleration
- attain and maintain postural equilibrium and balance
vestibule: features
macula: incl saccule and utricle
- hairs cells located in maculae
- detect linear motion
static equilibrium:
- maintenance of body position relative to force of gravity
inside macula:
gravity pushes the statoconia crystals (gelatinous like) onto the hair cells -> sensory neuron
semicircular canal: features
- anterior, posterior and lateral/horizontal canal
- hair cells in crista ampullaris
- detect angular acceleration in 3 planes
crista amupullaris:
- widest bit at end of semicircular canals
- filled with endolymph
- bends cupula with hair cells inside to detect motion
- hair cell -> neurons -> nerves -> brain via vestibular portion of vestibulocochlear nerve
- also to accessory nerve (con. to trapezius for posture)
list main parts of eye and associated structures:
- accessory structures of eye
- lacrimal apparatus
- extrinsic eye muscles
- conjunctiva
- eyeball
accessory structures around eye:
- eye brow
- eyelids (palpabrae), eye lashes
- lateral commissure/ angle (outer corner)
- medial commissure (inner corner)
- lacrimal caruncle (tear duct- sebaceous and sweat glands)
lacrimal apparatus: features
lacrimal fluid:
- water, salts, mucus, lactoferrin, immunoglobulins, enzymes
flow of tears:
lacrimal gland -> excretory lacrimal ducts -> sup/inf lacrimal canal -> lacrimal sac -> nasolacrimal duct -> nasal cavity
extrinsic eye muscles:
(LR6SO4)3
- medial, lateral rectus (straight) muscle
- superior, inferior rectus muscle
- superior/inferior oblique muscle
3 layers of eyeball:
- fibrous tunic
- vascular tunic (uvea)
- retina
fibrous tunic layer:
- outer layer (white)
- sclera
- cornea
vascular tunic layer
- middle layer (blue)
- choroid
- ciliary body
- iris
- contains melanin
retina layer:
- inner layer (red)
- photoreceptors
- interprets light
iris and pupil features:
bright light:
- circular muscles contract iris (parasympathetic) -> pupil constricts (hole)
dim light:
- radial muscles contract iris (sympathetic) -> pupil dilates
ciliary body and lens: features
- lens attached to ciliary muscles via zonules (inelastic ligaments)
- ciliary muscle relax -> ligaments pull and flatten lens (see far)
- ciliary muscle contracts -> ligaments relax tension and round lens (see close up)
to see close objects:
light rays aren’t parallel -> lens needs to be round to diverge image to correct position onto retina
general parts in retina:
- optic nerve
- macula (fovea inside)
fovea: features and light pathway
most visual acuity (high conc. of colour photoreceptors)
light from cornea -> fovea where neurons are pushed aside -> light directly hits rods/cones -> optic nerve -> brain
features: rods and cones
- named after outer segment shape
outer:
- photopigments (discs)
- transduction of light energy -> receptor potentials occurs here
inner:
- nucleus
- mitochondria
- golgi complex
colour blindness eg:
- can’t distinguish btw certain colours
- due to absence of one of 3 colour cones
- most common is red-green colour blindness
visual pathway:
optic nerve -> optic chiasm (where it can either cross hemisphere or stay on same side) -> optic tract -> thalamus -> visual cortex
