Brain and Special Senses

Question 1

special senses

Answer 1

smell (olfaction)
taste (gustation)
vision
hearing
balance (equilibrium)
receptors are concentrated within special structure- sense organs

Question 2

senses

Answer 2

sensory information is picked up by sensory receptors- simple ones are dendrites of sensory neurons
branching tips- free nerve endings
sensory info arrives at the CNS in the form of action potentials
arriving info is called sensation and conscious awareness of this is a perception
1% of information reaches conscious awareness

Question 3

general senses

Answer 3

temperature
pain
touch
pressure
vibration
proprioception ( body position)
receptors for these are located throughout the body

Question 4

smell- olfaction

Answer 4

provided by olfactory organs
located in nasal cavity in either side of nasal septum- inferior to cribifrom plate of ethmoid bone
organs consists of olfactory epithelium and glands

Question 5

process of olfaction

Answer 5

1- when you breathe in, air swirls within nasal cavity
2-air reaches olfactory organs and lipid and water soluble chemicals diffuse into the mucus before stimulating olfactory receptors
glands secrete mucus
(mucus protect receptors + dissolve lipid and water soluble chemicals)
cillia attaches to each receptor cell and extends to surrounding mucus
3- dissolved chemicals interact with receptors- oderant binding proteins (AP)- on cillia surfaces
odorants- chemicals that stimulate olfactory receptors
4- binding of odorents changes permeability of receptor membrane leading to action potentials
5-information is relayed to CNS
10-20 million olfactory receptor cells in area of 5cm2

Question 6

olfactory pathways

Answer 6

bundles of axons penetrate cribifrom plate of ethmoid bone to reach olfactory bulb
axons leaving each olfactory bulb travel along olfactory tract to olfactory cortex of cerbrum, hypothalamus and portions of limbic system (temporal lobe)

Question 7

taste (gustatory)

Answer 7

tongue- sensory organ
receptors are located over superior surface of tongue -adjacent to pharynx and larynx
taste receptors and specialised epithelial cells form sensory structures called taste buds

Question 8

taste buds

Answer 8

taste buds lie along side of epithelial projection- papillae
each taste bud contains slender sensory receptors- gustatory cells- plus supporting cells
each gustatory cell extends slender microvilli into surrounding fluids through taste pore

Question 9

taste sensations

Answer 9

sweet, salt, sour, bitter
umami and water

Question 10

taste mechanisms

Answer 10

dissolved chemicals contacting taste hairs stimulate a change in the membrane potential of the taste cell
resulting in action potential in sensory neuron
monitored by 3 cranial nerves- facial, vagus and glossopharyngeal

Question 11

taste pathways

Answer 11

sensory fibres of the different nerves synapse within a nucleus in the medulla oblongata
axons of postsynaptic neurons synapse in the thalamus
travel to gustatory cortex in temporal lobe

Question 12

vision- eye anatomy

Answer 12

eye is virtually spherical
eyes are located in the orbit of the skull

Question 13

mechanisms of vision

Answer 13

light enters eye and is refracted at the cornea and lens
refraction- alteration or bending of light when it travels from one medium to another
light is absorbed at retina by photoreceptors (rods and cones)
cones- central vision (fovea) - colour
rods- periphery of retina - presence of light

Question 14

process of seeing

Answer 14

light interacts with light sensitive molecules- photopigments- in photorecptors
pigments- rhodopsin= retinal + opsin
in presence of light; rhodopsin splits altering flow of electric current

Question 15

visual pathways

Answer 15

two 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 side of the brain
nuclei in the thalamus relay visual info to reflex centres in the brain stem aswell as visual cortex of cerebrum

Question 16

hearing

Answer 16

senses of hearing and equilibrium (balance) are provided by the inner ear- receptor complex in temporal bone
receptor mechanism for both of these senses is the same
simple mechanoreceptors

Question 17

ear anatomy

Answer 17

external ear, middle ear and inner ear
middle ear- air filled cavity- separated from ear canal by tympanic membrane
contains auditory ossicles- malleus, incus and stapes (small bones)
inner ear-receptors for hearing and balance in bony cochlear- in membranous labyrinth (tubes) containing fluid- endolymph (cochlear duct) and perilymph
cochlear duct is sandwiched between a pair of perilymph filled chambers
hair cells of cochlear duct located in organ of corti- where receptors are found- sits above basilar membrane (look at process)
movement of hair cells= AP

Question 18

process of hearing

Answer 18

1-sound waves arrive at tympanic membrane
2-movement of tympanic membrane causes displacement of auditory ossicles
3-movement of the stapes at the oval window establishes pressure waves in perilymph of vestibular duct
4-pressure waves distort basilar membrane on their way to the round window of tympanic duct
5-vibration of basilar membrane causes vibration of hair cells against tectoral membrane
6-information about the region and intensity of stimulation is relayed to CNS over the cochlear branch of cranial nerve 8

Question 19

auditory pathways

Answer 19

sensory neruons located in spiral ganglion monitor cochlear hair cells
afferent fibres form cochlear branch of vestibucochlear nerve
auditory complex of temporal lobe

Question 20

equilibrium

Answer 20

equilibrium sensations provided by hair cells of vestirbular apparatus:
semi circular canals- rotational movements
otoliths- accelerations

Question 21

semi circular canals

Answer 21

fluid filled chambers- central one formed of endolymph
rotation causes movement of fluid in SCC, fluid presses against cupula and causes movement of hair cells which generates action potential

Question 22

otoliths

Answer 22

contain receptors in gelatnious material
movement of fluid is detected by hair cells
trigger action potential
utricle- horizontal linear accelerations
saccule- vertical linear accelerations/ gravity

Question 23

equilibrium pathways

Answer 23

sensory neuron monitor hair cells of otoliths and SCC
afferent fibres form vestibular branch of vestibulocochlear nerve
fibres synapse on neurons in vestibular nuclei

Question 24

roles of vestibular nuclei

Answer 24

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 (to skeletal muscles)

Question 25

olfactory nerve

Answer 25

olfactory bulbs sends info here
nose

Question 26

oculomotor

Answer 26

movement of eye
innovates skeletal muscles in eye

Question 27

optic

Answer 27

passes visual info

Question 28

trochlear

Answer 28

movement of eyeball downwards and laterally

Question 29

trigeminal

Answer 29

feeling of face
input and actions for chewing

Question 30

abducens

Answer 30

movement of eye

Question 31

facial

Answer 31

taste receptors
skeletal muscles for facial expressions, salivary and tear glands

Question 32

vestibulocochlear

Answer 32

balance and hearing
transmitting info from cochlear to pons

Question 33

glossopharyngeal

Answer 33

taste receptors
innovating muscles for swallowing

Question 34

vagus

Answer 34

exhibit responses on organs
cardiovascular and respiratory

Question 35

accessory

Answer 35

motor nuclei of neck + upper back
innervate skeletal muscle

Question 36

hypoglossal

Answer 36

control of intrinsic muscles of tongue