Brain and senses

winniesmith's version from 2016-11-09 18:41

Section 1

Question Answer
where are the taste/gustatory receptorslocated over the superior surface of the tongue & adjacent pharynx & larynx. Taste receptors & specialised epithelial cells form sensory structures – taste bud.
what are the 5 different tasteSour, sweet, salt, bitter, water, umami
what are the epithelial projections on the tongue calledpapillae
what are the different types of papillaeFiliform (no taste buds). Fungiform ( 5). Circumvallate (100).
what is the structure of a taste bud?Each taste bud contains slender sensory receptors - gustatory cells - plus supporting cells. Each gustatory cell extends slender microvilli into surrounding fluids through a taste pore.
how do we taste?Dissolved chemicals contacting taste hairs stimulate a change in the membrane potential of the taste cell. Resulting in an action potential in the sensory neuron. Pathways: Taste buds are monitored by 3 Cranial Nerves: Facial (CN VII), Glossopharyngeal (CN IX), Vagus (CN X).
what is the taste pathwaySensory fibres synapse in the Medulla oblongata- axons of the postsynaptic neurons synapse in thalamus- gustatory cortex in cerebrum
Why are sense of smell and taste linked?Gustatory cortex is near the olfactory cortex in the brain so they can effect each other.

Section 2

Question Answer
Anatomy of the eyevirtually spherical. Located in the orbit along with extrinsic eye muscles, lacrimal gland, cranial nerves, blood vessels & fat
what is refraction and where does it happenRefraction = the alteration, or bending, of light when it travels from one medium to another. Refracted at the cornea and lens.
How is light absorbedAbsorbed at the retina by the photoreceptors (rods and cones).
What do photoreceptor rods do?Rods predominate in the periphery. Provide info on the presence or absence of light and shapes.
What do photoreceptor cones do?Cones predominate in central vision. Operate in daylight hours and provide info on colour. (sharpest vision)
What is the process of seeingLight interacts with light-sensitive molecules – photopigments – in the photoreceptors. Photopigments consist of Rhodopsin, made of Opsin and retinal (derivation of vitamin A-can be created from beta caotene). In the presence of light, rhodopsin splits, altering the flow of electrical current.
What is the visual pathway from the eyes to the brainTwo optic nerves reach the diencephalon at the optic chiasm. Here, half of the nerve fibres from each eye cross over to reach the thalamus on the opposite side of the brain Nuclei in the thalamus relay visual information to reflex centres in the brain stem as well as to the visual cortex of the cerebrum.
What part of the cerebrum is involved with site?Visual association area, occipital lobe and visual cortex.

Section 3

Question Answer
Where are the senses/receptors for hearing?Inner ear. Receptors (hair cells) are mechanoreceptors. External and middle are air filled, inner ear is fluid filled.
Anatomy of the Middle EarAir-filled cavity. No bone, just membrane,can vibrate. Separated from the ear canal by the tympanic membrane. Contains auditory ossicles: Malleus, Incus & Stapes. Auditory tube, linked to the throat. Stapes connected to fleshy part of inner ear.
Anatomy of the Inner EarVestibule, three semicircular cannals and Cochlea. Bony labyrinth closely follows contours of the membranous labyrinth (interconnected network of fluid filled tubes- receptors found in these tubes.
What are the fluids within the membranous labyrinthBetween the bony and the membranous labyrinth flows perilymph (similar to crebrospinal fluid) and Endolymph, in the membranous labyrinth, a fluid with electrolyte concentrations differing from typical body fluids.
Where is the cochlear ductWithin the bony cochlea. sandwiched between a pair of perilymph filled chambers.
Name the 2 places where the bony labyrinth walls are NOT dense boneRound window (base of tympanic duct- under cochlear duct). Oval window (base of vestibular duct- above cochlear duct).
Where are the hair cells locatedin the Organ of Corti, sits above basilar membrane. Stereocilia of hair calls in contact with tectorial membrane.
Where is the organ of cortinext to cochlear duct, between vestibular and tectoral membrane.
Describe the process of hearing1) Sound waves arrive at tympanic membrane.
2) Movement of tympanic membrane causes displacement of the auditory ossicles.
3) Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
4) The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
5) Vibration of the basilar membrane causes hair cells to vibrate against the tectorial membrane.
6) Information about the region and intensity of stimulation is relayed to the CNS over the cochlear branch of the vestibularocular nerve
How does the vibration of hair cells cause depolarization?Vibration of the affected region of the basilar membrane moves hair cells against the tectorial membrane. This movement leads to the displacement of the steriocilia. This opens ion channels in the plasma membranes of hair cells, causing an inrush of ions which depolarize the hair cells. This causes neurotransmitters to be released that stimulate sensory neurons.
Where are the sensory neurons located?Cell bodies of bipolar sensory neurons that monitor the cochlear hair cells are located in the spiral ganglion- center of the bony cochlea. From there info is carried to the cochlear branch of the vestibulochochlear nerve.
Pathway from cochlear branch of N V111 to brain part.Axons of the CN VIII enter the medulla oblongata & synapse at cochlear nucleus (in pons)--> inferior colliculus (midbrain)---> synapse in thalamus --> Auditory cortex of temporal lobe.

Section 4