Brain And Special Senses Flashcards
What are the general senses
Temp
Touch
Pain
Pressure
Vibration
Proprioception = bodies position within space
= receptores throughout body
What are the special senses
Special senses
Receptors in special sensory organs, in special structures
Smell - olfaction
Taste - gustation
Vision
Hearing
Balance - equilibrium
Outline olfaction
- provided by pairs of olfactory organs
- located in the nasal cavity, either side of the septum
- inferior to cribform plate of ethmoid bone
- the olfactory organs are the olfactory epithelium and olfactory glands
Outline the process of olfaction
1 breath in air, swirl in nasal cavity
2. Reach olfactory organs, lipid and water soluble chemicals diffuse into mucus stimulation the cilia on receptors
3. Dissolved chemicals interact with odour binding proteins in receptors
4. Binding of the odourants changes the permeability of membrane creating an action potential
5. Relayed to cns where smell interpreted
Outline olfactory pathways
- bundles of axons penetrate cribriform plate of ethrimoid bone to reach olfactory bulb
- axons leaving olfactory bulb travel to cerebrum
- olfactory cortex in temporal lobe
Outline gustatory receptors
- located over surface of tongue and adjacent larynx and pharynx
- taste receptors and specialised epithelial cells form taste buds- lie along side of epithelial papillae
- microvilli
- action potentials
What are the taste sensations
Sweet
Salt
Sour
Bitter
Ulami
Water
Outline taste pathways
- taste buds monitored by 3 cranial nerves
- sensory fibres of different nerves synapse within a nucleus in med ob
- gustatory cortex
Mechanism = dissolved chemicals change membrane potential
Outline hearing
- senses of hearing/equilibrium provided by inner ear - receptor complex in temporal bone
- receptor mechanisms for both senses is the same
- receptors are hair cells - mechanoreceptors
Outline the inner ear
- air filled cavity
- separated from ear canal by tympanic membrane
- contains auditory ossicles (bones) malleus, incus and snapes
- receptors for hearing and balance in membranous labyrinth, contains fluids endolymph and perilymph
-tympanic membrane vibrates = bones move in order - bony cochlea contains cochlea ducts
- duct sandwiched between pair of perilymph filled chambers
Outline the process of hearing
- Sound waves arrive at tympanic membrane
- Auditory ossicles move
- Movement of stakes = pressure waves in vesicular duct
- Pressure waves disrupt basilar membrane
- Hair cells vibrate
- Relay to cns
Outline auditory pathways
- sensory neurons within spinal ganglia monitor cochlea hair cells
- afferent fibres
- axons enter medulla oblongata and synapse at cochlea nucleus
Equilibrium
- all equilibrium sensations provided by hair cells of vestibular apparatus
- receptors respond to rotational movement
- utricle = horizontal
- saccule = vertical
Outline equilibrium pathways and the role of the vestibular nuclei
- sensory neurons monitor hair cells of canals
- afferent fibres form vestibular batch of vestibular nerve
- neuron in vestibular nuclei
Roles:
1. Inter grade sensory info from sides of head
2. Relay to cerebellum
3. Relay to cerebral cortex
4. Send motor command to nuclei in brain stem and spinal chord
Outline the mechanisms of vision
- rays enter and bend as cornea water based reaction
- refraction also happens at the lease
- light absorbed at retina by photoreceptors, rods and cones
- cones = predominant central vision and colour
- rods = predominate periphery vision and light presence
Outline the process of seeing
- light interacts with light sensitive molecules called photopigments in photoreceptors
- photopigments consist of rhodopsin, made of Epsom and retinal
- in presence of light, rhodopsin splits altering the flow of electrical current
= change in membrane potential creating action potential - gap in visual field = blind spot
Outline visual pathways
- 2 optic nerves reach diencephalon and optic mechanism
- here half the nerve fibres from each eye cross over to reach thalamus in opposite side of brain
- occipital lobe
