The brain and special senses Flashcards
What is the difference between sensation and perception?
Sensations are arriving information whereas perception is conscious awareness of a sensation
What are the general senses?
Temperature, pain, touch, pressure, vibration and proprioception
What are the special senses?
Smell (olfaction), taste (gustation), vision, hearing and balance
What are the olfactory organs?
They consist of epithelium which contain supporting and receptor cells with cilia. Glands that secrete mucus that cover the epithelium for protection in the nasal cavity
What is the process of smelling?
- When breathing in air swirls within the nasal cavity
- Upon reaching the olfactory organs lipid- & water-soluble chemicals diffuse into the mucus before stimulating olfactory receptors
- Dissolved chemicals interact with receptors – odorant binding proteins – on the cilia surfaces
- Binding of odorants (any chemical that stimulates olfactory receptors) changes permeability of receptor membrane → action potentials
- Info relayed to CNS and smell is interpreted
What are the olfactory pathways?
Bundles of axons penetrate the cribriform plate of the ethmoid bone reaching the olfactory bulb they then travel along the olfactory tract to the olfactory cortex of the cerebrum and potentially the hypothalamus and portions of the limbic system
What is the anatomy of the taste organs?
Sensory organs on the superior surface of the tongue and adajet pharynx and larynx
Taste buds - are found along the sides of the epithelial projections - papillae
Filiform - no taste buds
Fungiform - 5
Circumvallate - 100 - near the back
Taste pores
Each taste bud contains sensory receptors called the gustatory cells and supporting cells microvilli extend into the taste pore
What are the 5/6 sensations?
Sweet, salty, sour, bitter umami, water receptors
What is the taste mechanism?
Dissolved chemicals contact the receptors on the microvilli which changes the membrane potential of the taste cell leading to an action potential
What is the taste pathway?
Monitored by the facial, glossopharyngeal and vagus nerve
Synapse in the medulla oblongata, axons of the post synaptic neurons synapse in the thalamus make their way to the gustatory cortex in the temporal lobe
What is the anatomy of the eye?
Receptors are located in the eye
Located in the orbit with - extrinsic eye muscles, lacrimal gland, cranial nerves, blood vessels and fat
Cornea outer most layer - transparent - water based
Light moves through the pupil surrounded by the iris then into the lens with multiple layers
Then into the posterior cavity
Encassed by the retina - receptor cells are located
What are the mechanisms of vision?
Refracted (bending of light) at the cornea and lens
Retina contains multiple layers of cells - cones(colour) and rods - synapse with bipolar and then ganglion cells
Fovea contains the cones in the central, rods in periphery
Outline the process of seeing
Light interacts with photopigments
Consists of rhodopsin made of opsin and retinal
Rhodopsin is split generates the action potential passed from the bipolar cells to the ganglion cells and then the optic nerve
What is the visual pathway?
2 optic nerves reach the diencephalon at the optic chiasm - half of the nerve fibres from each eye cross over to reach the thalamus on the opposite site
Nuclei in the thalamus relay visual info to reflex centres in brain stem as well as the visual cortex of the cerebrum
What is the anatomy of the external ear?
Auricle and external acoustic canal
What is the anatomy of the middle ear?
Tympanic membrane separates the external ear canal from the middle ear
- Air filled cavity - contains the malleus, incus and the stapes - connected to the throat via the auditory tube
What is the anatomy of the inner ear?
completely encassed by bone - cochlea inside is 3 fluid filled different ducts - Vestibular duct- perilymph, cochlear duct - receptors for hearing, endolymph , and tympanic duct perilymph
Dense bone except from 2 areas with membrane - round window base of tympanic duct and oval window base of vestibular duct
What are the organ of the corti?
Contains receptor cells that contain minute hair cells sterocilia of hair cells in contact with the tectorial membrane
What is the sense of hearing?
- Sound waves arrive at tympanic membrane
- Movement of this causes displacement of the auditory ossicles
- Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct
- The pressure waves distort the basilar membrane on their way to the round window
- Vibration of the basilar membrane causes vibration of hair cells against the tectorial membrane
- Info about the region and the intensity of stimulation is relayed to the CNS
What is the sensory pathway of hearing?
Sensory neurons in the spiral ganglion monitor the cochlear hair cells
Afferent fibres from cochlear branch of vestibulocochlear nerve
Axons of CN VIII enter the medulla oblongata and synapse at the cochlear nucleus inferior colliculus synapse in thalamus auditory cortex of temporal
What is the anatomy of the ear within balance?
Hair cells in the vestibular apparatus - semi circular canals and otoliths - semi circular canals detect movement of fluid as hair cells in the ampulla move and A.P generated - otoliths - raised structures - info for accelerations of the body
Crista raised structure in the ampulla
Stereocilia embedded in the cupula
What are the Otoliths?
Utricle - horizontal linear accelerations
Saccule - vertical linear acceleration
What is the sensory pathway for balance?
- Integrate sensory information arriving from each side of the head
- Relay information to cerebellum
- Relay information to cerebral cortex
- Send commands to motor nuclei in brain stem and spinal cord
