Sem 2 Module 4 - Special Senses Flashcards
(73 cards)
1
Q
What cell is responsible for smell?
A
Olfactory
The olfactory epithelium can identify many primary sensations of smell
2
Q
Where are the receptors of the olfactory cells located?
A
In the nasal epithelium lining of the nasal cavity, with the cell bodies of olfactory cells lying between supporting cells of the epithelium
3
Q
What kind of receptor is olfactory cells?
A
Chemoreceptors - Which respond to chemical in water solution
- Water on the surface of the epithelium dissolves substances which are carried into the nose in air
4
Q
In order to be smelled, what must a substance be capable of doing?
A
In order to be smelled, substances must be able to convert to a gaseous state in order to reach the nasal cavity in the first place, and also to be water soluble to stimulate olfactory cells
5
Q
What do chemicals in solution bind to? and what happens?
A
Chemicals in solution may bind to protein receptors on olfactory cells,
This alters the permeability of the cell membrane.
With a rise in membrane potential
6
Q
What happens if depolarization is sufficiently large?
A
- If depolarization is sufficiently large (threshold or greater) an action potential will be triggered
- Olfactory cells are very sensitive, in many cases responding to a few molecules of a substance.
- Axons leaving the olfactory cells penetrate the cribriform plate (ethmoid bone) of the skull.
- Their impulses are transmitted to other neurons the fibres of which travel to the brain in the olfactory nerve (CN I)
- Sensations of smell are experienced when impulses reach the olfactory cortex in the temporal bone
7
Q
What cells are responsible for taste?
A
Gustatory cell
8
Q
Where are the cells located that are responsible for taste?
A
Located in taste buds, mainly on the surface of the tongue, in the projections called papillae
9
Q
Describe a taste bud.
A
Each taste bud is otherwise hollow, with a narrow opening to the surface, a taste pore
- From each gustatory cell within the taste bud extend fine projection (microvilli): these function as the actual taste receptors
10
Q
What does stimulation of the gustatory cell require?
A
Stimulation of the gustatory cells requires substances to be in solution in saliva so they can enter taste pores
11
Q
What else about taste buds?
A
- Associated with epithelial projections (Lingual papillae on superior surface of the tongue
12
Q
What are three types of Lingual papillae?
A
Filiform papillae
Fungiform papillae
Circumvallate papillae
13
Q
What do Filiform papillae do and contain?
A
Provide friction
Do not contain taste buds
14
Q
What do fungiform papillae contain?
A
Contain five taste buds each
15
Q
What do circumvallate papillae contain?
A
Contain 100 taste buds each
16
Q
What are the four primary taste sensations?
A
Sweet - stimulated by sugars, saccharin
Sour - Stimulated by H+ (acids)
Salt - Stimulated by metallic salts, e.g. Na+, K+
Bitter - Stimulated by alkaloids, e.g. quinine, nicotine, morphine
17
Q
Where are each taste detected on the tongue?
A
Tip —> Sweet, salty
Sides —> Sour
Back —-> Bitter
18
Q
What are other additional human taste sensations?
A
Umami
- Characteristic of beef/chicken broths and parmesan cheese
- Receptors sensitive to amino acids, small peptides, and nucleotides
Water
- Detected by water receptors in the pharynx
19
Q
What cranial nerves do taste receptors travel into the medulla in?
A
CN VII (Facial) CN IX (Glossopharyngeal)
Whilst a few taste buds in the epiglottis are conducted primary by CN X (Vagus)
and are relayed to the somatosensory (gustatory) cortex
- Fibres also project to the limbic system and hypothalamus
- The sense of taste and smell have combined effect when interpreted in the cerebral cortex: much of we taste is actually smelled.
20
Q
What is the structure of the ear?
A
- The ear contains various structures involved in hearing and maintaining equilibrium
- It includes the
External (outer ear)
Middle ear and,
Internal /Inner ear - All these portion function in hearing, but the internal ear also helps maintain balance and equilibrium
21
Q
What does the external ear contain?
A
- Pinna (auricle
- External auditory meatus (canal)
- Tympanic membrane (eardrum)
22
Q
What kind of pressure is on the outside of the eardrum?
A
Atmospheric pressure
23
Q
What does the middle ear contain?
A
Bones (ossicles)
- malleus
- Incus
- Stapes
Eustachian (auditory) tube
24
Q
What is the air pressure on the inside of the ear?
A
Atmospheric pressure, as the air-filled cavity of the middle ear is connected through the Eustachian tube with the throat
25
What does the internal ear contain?
The components of the inner ear are located in the temporal bone
There are cochlea, vestibule, and the semicircular canals
These are all linked, and organised as series of interconnecting membranous tubes (membrane labyrinth), housed within bony tunnels (bony labyrinth)
The membranous labyrinth is filled with a fluid, endolymph: the space between the membranous labyrinth and the walls of the bony labyrinth is filled with perilymph
26
What is recall?
- Air in a compressible gas
- A vibrating object causes alternating compression and rarefaction: each compression causes a slight increase in pressure and each rarefaction causes a slight decrease in pressure
- A graphical representation of pressure against time gives a wave pattern, hence we speech of sound waves. The height of waves (amplitude) is detected as intensity or loudness
- The number of waves in any given time (frequency, expressed in Hertz) is detected as pitch
27
What do sound waves cause?
Sound waves cause the tympanic membrane to vibrate
- The malleus, incus and stapes transmit vibration from tympanic membrane to the membrane of the oval window
- Vibration of the membrane of the oval window sets up oscillations in the fluid within the cochlea (perilymph); these travel around the cochlea to the round window
- Oscillations in the perilymph cause vibration of the membranes in the cochlea (these form the cochlear part of the membranous labyrinth of the inner ear)
28
What is within the membranous tube of the cochlea?
Within the membranous tube of the cochlea is a membranous "sandwich" (the organ of Corti). The "filling" of this "sandwich" consist of hair cells, which are the actual auditory receptors; the top layer of the sandwich rests on the fine projections (hairs) of these cells
29
What kind of receptors are hair cells?
Thus, hair cells - auditory receptors - are in fact highly specialised mechanoreceptors
30
How are impulses generated in hair cells transmitted?
Impulses are generated in hair cells are transmitted to the fibres of sensory neurons which underlie the hair cells.
- The cell bodies of these neurons are located in a sensory ganglion nearby
31
What nerve do sensory neurons from the cochlear branch off?
- The sensory neurons form the cochlear branch of the Vestibuloccoclear nerve
32
What are impulses originating in the cochlea carried on?
Impulses originating in the cochlea are carried along sensory fibres in to the brain at the medulla,
- cross to the opposite side, and are an transmitted to the auditory cortex in the temporal lobe.
- Here they are finally interpreted as sound
33
What is Static equilibrium?
Evaluating the position of the head relative to gravity (up/down). It is required when the head is motionless, or moving in a straight line
34
What is Dynamic equilibrium?
Required when the head is rotating, or moving in an angular direction
35
What organs are located in the vestibule of the bony labyrinth?
Balance organs are located in the vestibule of the bony labyrinth
- Within the vestibule, the membranous labyrinth is divided into the sac-like utricle and saccule
- Each contain a path of jelly, macula, lying over hair cells (as in the organ of Corti) so that the hairs are embedded in the jelly
- A mass of calcium carbonate grains, otoliths, lie embedded in the surface of the jelly. When the head position is changed, gravity pulls on the otoliths and distorts the jelly and the hair cells
36
What is distortion of cells a stimulus for?
Distortion of the hair cells is the stimulus for their depolarization, and the transmission of the impulses to their underlying sensory neurons.
The arrangement of the hairs is such that the generated impulses indicate the direction of movement from the equilibrium position.
37
Where do impulses travel via (which nerve) and where to?
Impulses travel via the Vestibuloccoclear nerve to the medulla and cerebellum of the brain, rather than the cortex.
38
What are the accessory structures of the eye?
Eyebrow --> With sebaceous gland, protect the eye from perspiration and direct sunlight
Orbits --> Cone shaped bony sockets, surround much of the eye and incorporate fatty cushions to protect against impact.
Eyelids (Palpebrae) -->
- Muscular folds of facial skin fringed with hair
- The inner eyelid surface secretes the oily lubricant responsible for keeping the eyes open
Conjunctions -->
- Delicate mucous membrane lining the eyelids and white of the eye
- Produce lubricating fluid
- Infection and inflammation of this membrane is conjunctivitis
39
What does the lacrimal (tear) apparatus of each eye consists of?
```
Lacrimal gland
Lacrimal ducts
Lacrimal canals
Lacrimal sac
Nasolacrimal duct
```
40
What is the Lacrimal gland?
A lacrimal gland, which lies in the upper lateral position, and secretes a continual flow of salt solution, tears
41
What do lacrimal ducts do?
Lacrimal ducts, which carry tears from the lacrimal gland to the surface of the eye
42
What do lacrimal canals do?
Paired lacrimal canals, in the medial angle to receive tears which have flowed towards them
43
What is the lacrimal sac?
A lacrimal sac, which collects tears and directs them into a nasolacrimal ducts
44
What does the nasolacrimal duct do?
A nasolacrimal duct, which empties into the nasal cavity
45
What do tears contain?
Tears contain mucus, antibodies and lysozyme
46
What do tears do?
- Cleanse, moisten and protect the eye surface
47
How do our eyes move?
- Six extrinsic eye muscles allow movement of each eyeball
| - These muscles originate form the walls of the orbits and insert into the outer surface of the eyeball
48
What do these muscles enable the eye to do?
- They enable the eyes to be fixed on stationary or moving objects and keep both eyes fixed on the same object at the one time
49
What is the structure of the eye?
- Anterior cavity
- Posterior cavity
- Lens
- Tunics of the eye
50
What is the anterior cavity? what does it contain?
- Anterior chamber and posterior chamber
- Contains fluid, aqueous humour
- Pathological increase in fluid pressure: glaucoma, this is a common disease, which can lead to blindness if not treated
51
What is the posterior cavity? what does it contain?
- Vitreous chamber
| - Contains vitreous humour
52
What are the tunics of the eye?
1. Fibrous tunic
2. Vascular tunic
3. Retina
53
What two regions are in the fibrous tunic?
Sclera
| Cornea
54
Where is the sclera of the fibrous tunic?
Over most of the eye
55
Where is the cornea?
Transparent region at front of eye
56
What is the vascular tunic?
Middle layer, consisting of three layers
57
What are the three layers of the vascular tunic?
- Choroid
- Ciliary body
- Iris
58
What is the choroid layer?
highly vascular
59
What is the Ciliary body layer?
Forms muscular ring around lens
60
What is the iris?
- Adjustable diaphragm that controls diameter
61
What is the retina?
```
Inner nervous layer
Cell types - photoreceptors (rods and cones)
- ganglion cells
- fovea centralis
- Optic disc
```
62
What are the photoreceptors?
Rods and cones of the retina are the light=-detecting cells of the eye
63
What do rods detect?
Receptors for dim light
64
What do cones detect?
Receptors for bright light, colour and visual acuity
65
What are the three types of cones? What happens when they are stimulated?
Blue cones
Green cones
Red cones
- Colour vision results from various mixes of stimulation of the three types of cones
- If all types of cones are stimulated, the colour white is sensed, if none, the colour black is sensed
- Colour blindness occurs when there is a deficit or absence of one of the colour detecting cones
66
How are imaged formed on the retina?
- Image formation
- Light rays passing from one transparent medium to another change direction according to the density of the substance ---- this is called refraction
Focusing light on the retina
- The pathway of light in the eye involves for such changes of medium
1. Air to cornea
2. Cornea to aqueous fluid in anterior cavity
3. Aqueous fluid to lens (controlled by iris)
4. Lens to vitreous body in posterior eye cavity
67
Where are visual pigments found?
Visual pigments (photo pigments) are found in rods and cones
68
What do rods contain?
Rods contain rhodopsin, which is very sensitive to light
69
What does light promote of rhodopsin?
- Light promotes the breakdown of rhodopsin into its constituents and, when this occurs, the rod cell membrane is depolarised and an action potential is produced
- Rhodopsin Is then regenerated from its components, preparing the rod for its next stimulus
- In bright light, the rhodopsin in rods is largely broken down
- When moving from a bright to a dark area, sometime must be allowed for adaption of the eye: this corresponds s to the period required for rhodopsin regeneration
- The visual pigments of cones operate in simular fashion
70
Retinal processing?
The retina contains millions of receptor cells
- On-centre fields
- Stimulated by light hitting the centre of the field
- Inhibited by light hitting the periphery of the field
- Off-centre fields have the opposite effects
- Theses responses are due to different receptor types
71
Processing with the thalamus?
- Nuclei of the thalamus
- Relay information on movement
- Segregate the retinal axons in preparation for depth perception
- Emphasize visual inputs from regions of high cone density
- Sharpen contrast information
72
Cortical processing?
- Two areas in the visual cortex
- Primary visual cortex
- Processes contrast information and object orientation
- Visual association areas
- Processes form, colour, and motion from p.v.c .
73
Cross overs at the Optic chiasma?
- The two optic nerves cross at the optic chiasma
which involves some fibres from each side passing to the opposite side while others remain uncrossed
- Fibres terminate in the visual areas which are located in the cortex of the occipital lobes of the cerebrum
- Half of the fibres from each retina cross sides on their way to the occipital lobes so:
- Impulses fro the right half of each retina travel to the right visual cortex
- Impulses from the left half of each retina travel to the left visual cortex
The right half of each retina registers the left visual field and vice versa
