The brain and special senses

Question 1

What is the difference between sensation and perception?

Answer 1

Sensations are arriving information whereas perception is conscious awareness of a sensation

Question 2

What are the general senses?

Answer 2

Temperature, pain, touch, pressure, vibration and proprioception

Question 3

What are the special senses?

Answer 3

Smell (olfaction), taste (gustation), vision, hearing and balance

Question 4

What are the olfactory organs?

Answer 4

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

Question 5

What is the process of smelling?

Answer 5

1. When breathing in air swirls within the nasal cavity
2. Upon reaching the olfactory organs lipid- & water-soluble chemicals diffuse into the mucus before stimulating olfactory receptors
3. Dissolved chemicals interact with receptors – odorant binding proteins – on the cilia surfaces
4. Binding of odorants (any chemical that stimulates olfactory receptors) changes permeability of receptor membrane → action potentials
5. Info relayed to CNS and smell is interpreted

Question 6

What are the olfactory pathways?

Answer 6

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

Question 7

What is the anatomy of the taste organs?

Answer 7

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

Question 8

What are the 5/6 sensations?

Answer 8

Sweet, salty, sour, bitter umami, water receptors

Question 9

What is the taste mechanism?

Answer 9

Dissolved chemicals contact the receptors on the microvilli which changes the membrane potential of the taste cell leading to an action potential

Question 10

What is the taste pathway?

Answer 10

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

Question 11

What is the anatomy of the eye?

Answer 11

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

Question 12

What are the mechanisms of vision?

Answer 12

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

Question 13

Outline the process of seeing

Answer 13

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

Question 14

What is the visual pathway?

Answer 14

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

Question 15

What is the anatomy of the external ear?

Answer 15

Auricle and external acoustic canal

Question 16

What is the anatomy of the middle ear?

Answer 16

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

Question 17

What is the anatomy of the inner ear?

Answer 17

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

Question 18

What are the organ of the corti?

Answer 18

Contains receptor cells that contain minute hair cells sterocilia of hair cells in contact with the tectorial membrane

Question 19

What is the sense of hearing?

Answer 19

1. Sound waves arrive at tympanic membrane
2. Movement of this 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
5. Vibration of the basilar membrane causes vibration of hair cells against the tectorial membrane
6. Info about the region and the intensity of stimulation is relayed to the CNS

Question 20

What is the sensory pathway of hearing?

Answer 20

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

Question 21

What is the anatomy of the ear within balance?

Answer 21

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

Question 22

What are the Otoliths?

Answer 22

Utricle - horizontal linear accelerations
Saccule - vertical linear acceleration

Question 23

What is the sensory pathway for balance?

Answer 23

1. Integrate sensory information arriving from each side of the head
2. Relay information to cerebellum
3. Relay information to cerebral cortex
4. Send commands to motor nuclei in brain stem and spinal cord