Sensory systems Flashcards
What are stimuli that we are sensitive to?
Mechanical Chemical Photic Thermal Pain Kinesthia
What are most of the sense organs sensitive to ?
external stimuli
What are the 6 different receptors?
Mechanoreceptors Chemoreceptors photoreceptors thermoreceptors nociceptors proprioceptors
What are mechanoreceptors sensitive to?
touch
hearing
balance and acceleration (vestibular system)
What are the chemoreceptors sensitive to?
taste (gustation)
smell (olfaction)
What are the photoreceptors sensitive to?
vision (photoreception)
What are the thermoreceptors sensitive to?
hot/cold
What are the nocieptors sensitive to?
various things (chemical, mechanical etc)
What are the proprioceptors sensitive to?
various (muscle spindles etc)
How can we sense blood pressure?
in our arteries, we have stretch receptors/mechanoreceptors which are sensitive to the diameter of our arteries
How do we detect blood oxygen/respiration?
respiration is controlled by the levels of oxygen and carbon dioxide
Chemoreceptors are sensitive to oxygen abd co2
What are some mechanoreceptors which can sense bp?
baroreceptors
What are other receptors sensitive to?
glucose etc
What are the sensory receptors for internal stimuli?
Mechanoreceptors- e.g baroreceptos
chemoreceptors
What animals have greater stimuli/senses than humans?
Aquatic animals
Sharks
How do aquatic animals such as fish have a greater number of stimuli?
They have lateral lines which is a sense organ which senses water movement which humans dont have
What are the receptors for lateral lines?
mechanoreceptors
How are animals considered to have even greater stimuli/senses to humans?
due to the earths magentic field which is percieved by animals such as birds and fish and is used for navigation (magnetoreception)
How do sharks and duck billed platypus have greater number of stimuli?
They can sense electricity, as they can sense action potentials and the electricity given off by the heart of other animals which are trying to hide for e.g.
So they can detect fish buried in the sea bed by detecting their electric fields (electroreception)
What other sense can be compared between animals and humans?
vision - (a sense)
What can fish birds and insects see?
can see UV light - see shorter wavelengths
What can snakes and beetles sensitive to?
Infrared
What is transduction?
Take the sensory stimulus and convert it to neurobiological activity
Layout the simple sensory system?
Neuron
stimulus- causes a change in membrane permeability leading to receptor potential e.g open Na channels - causing small depolarisation-
action potential which is carried to
CNS
What is a simple sensory system?
Smell
What is the sensory system of smell?
- Sensory neurone stimulated directly by the odour molecule
- an odour/olfactory molecule (chemical) dissolves in the nasal mucus
- sensory cells (bipolar neurones) which have cilia (increasing s.a)
- On the cilia, you have protein receptors
- the molecule binds to the protein receptors on the cilia
- Opens ion channels (which go into the bipolar)
- Action potential produced in the receptor
- CNS
What is the first cranial nerve ?
which takes the info from the nose to the brain
What is different about olfactory neurons compared to others?
they regenerate as they are replaced by epithelial cells which turn into sensory neurons
How are most sense organs built?
there is a specialised receptor cell that does not generate an action potential BUT it synapses with a sensory neuron that does
What cells are the taste buds made of?
made of 60 cells
sensory cells
epithelial cells
sensory neuron on the base of receptor cell
What is a specialised receptor cell for taste buds?
gustatory receptor
What is a receptor potential
when a receptor cell produces a small depolarisation which triggers an action potential in the sensory neuron
What do most senses involve?
a specialised receptor cell.
What is the receptor cell associated with?
an accessory structure
What is an accessory structure?
something which modifies the stimulus before it hits receptor cell e.g a membrane (hearing) or hair
What are the receptors which are most likely associated with the accessory structure?
tactile receptors
How are sensory neurons associated with accessory structures?
all sensory neurons are associated with the different accessory structure
e.g root hair plexus- wrapped around the base of the hair is a sensory neurone, so what activates the sensory neurone is the movement of hair so this is the accessory structure which makes this neuron sensitive to touch
the Pacinian corpuscle has a sensory neurone wrapped around with layers of connective tissue, which that accessory structure which makes it sensitive to deep pressure
What are the receptors involved in touch?
detect movement of hair thermoreceptors low-frequency vibration deep pressure light touch
What do accessory structures do?
Determines what cell is sensitive to.
touch is a good example of that
What hearing involves?
turning sound into electrical activity in the ear which the brain can interpret (transduction)
What is sound?
the variations in air pressure
What is pure sound?
tuning fork
What is middle c?
256Hz
What are sounds made of?
combination of notes forming more complex sound known as the quality of the sound.
How is middle c produced and what does it cause?
a tuning fork which produces middle c vibrates 256 times a second and is producing area of low and high pressure 256 times a minutes
How are high and low notes produced?
higher notes produce by more frequent vibration
lower notes produced by less frequent vibration
What does the pinna of the outer ear do?
serves to channel sound into the external auditory meatus
What happens when sound hits tympanic membrane?
when waves of air pressure come in external auditory meatus it is going to hit the tympanic membrane causing it to vibrate
What is the area of the tympanic membrane?
areas of 65mm
What happens when there is high and low pressure in the tympanic membrane?
area of high pressure the tympanic membrane moves in and low-pressure tympanic membrane moves out.-
What happens to these vibrations?
the movement is transferred through the air-filled middle ear to the inner ear which causes movement of the oval window
causing movement of fluid in inner ear
now the movement of the tympanic membrane is changed to fluid
What was the beginning of the transduction in the outer ear?
due to the changing in air pressure into the movement of the tympanic membrane
What is the middle ear filled of?
air
What does fluid have?
high impedance which means resistant to movement
What is the difference between the air to fluid causing movement of membrane ?
easy to cause movement of the membrane which is in the air but hard to cause fluid movement.
What does the middle ear have and what do they do?
3 bones (malleus, incus and stapes) transfer the vibration of the tympanic membrane to the oval window
What does the eustacean tube do?
connects the middle ear to the nasopharynx
equalise pressure in the middle ear to atmospheric pressure
What else does the middle ear have?
2 muscles which attach these bones
when these muscles contract they can freeze these muscles which stops the sound from being transmitted
It happens in response to loud noises.
What causes small movement of tympanic membrane
the pressure changes in sound are small
What then causes fluid movement in the inner ear?
the movements of the tympanic membrane has to be converted to the movement of the oval window.
what is the function of the middle ear
to act as an impedance matching device which means the middle ear amplifies the sound
What are the 2 ways the middle ear amplifies the movement of the tympanic membrane (for sound)?
- the pressure of the tympanic membrane is spread over a large surface area. The area of the oval window is much smaller, concentrating the pressure.
this means that small vibrations of the tympanic membrane tunr into large vibrations of the oval window
-the middle ear ossicle (bones) act as a lever system, so that small moveemnts of the malleus are amplified (of the stampes)
Waht does the eustacean tubve?
serves to equalise pressure of the middle ear to atmospheric pressure
What happens if atmospheric pressure is less?
if atmospheric pressure less, tympanic membrane bows out
What is the valsalva manoeuvre
equalises the pressure in the middle ear and atmosphere
What does the inner ear do?
subserves both the auditory and vestibular system
What does the inner ear consist of?
bony labyrinth filled with a fluid called perilymph suspended in which is a membranous labyrinth containing a fluid called endolymph
What is labryinth?
very complicated maze-like system of tubes
What does endolymph have
lots of potassium in it
What is the inner ear divided into 3 portions of?
- coiled cochlea (hearing)
- the bony vestibule containing the membranous sacs called saccule and utricle (vestibular)
- 3 semi-circular canals orientated in the 3 planes of space (vestibular)- where they join onto the utricle you get a swelling called the ampulla.
What makes up the vestibular system?
utricle
saccule
semi-circled canals
What is the cochlea divided up by?
membranes that run the length of the cochlea
upper chamber- scala vestibule
lower chamber- scala tympani
middle chamber- scala media
Where are the upper and lower chambers joined at?
scala vestibule and scala tympani are joined at the tip of the cochlea area called the helicotrema
What happens if you have the scala vestibule and scala tympani joined?
as liquids are incompressible, when oval window pushed in you need round window which will bow out and that will work.
What is the scala vestibule and scala tympani filled with?
perilymph,
What is the central cochlear duct filled by?
endolymph
What happens when the stapes is pushed (oval window)?
causes the movement of perilymph in the scala vestibule, which is transferred to the scala tympani and causes the round window to bulge out
What does the vestibular membrane?
forms junction to scala media
What does the basement membrane do?
seperates scala media from scala tympani
What are the 3 tubes the cochlea forms?
- scala vestibule
- scala tympani
- scala media
What is the organ of corti?
sits on the basement membrane which divides the cochlear duct from the scala tympani
What does the organ of corti have?
have 4 rows of hair cells
What is the hair cell structure?
cells with cilia on the top and on the base they are linked to sensory neurons
What are the hair cells?
sensory cells
Where are the stereocilia?
embedded in the tectorial membrane which is a gelatinous membrane which is an example of an accessory structure
tectorial membrane sits ontop of the cilia
What is the hair cell?
stereocilia on top of receptor and have sensory neurons at the bottom which form the 8th cranial nerve
What is the order of the organ of corti?
Tectorial membrane
cilia
hair cell
What happens when you vibrate stapes?
a wave of movement going up the basilar membrane
going from the maximum amplitude
What happens far away from stapes?
the basement membrane is quite wide, floppy
this part responded best to low-frequency stapes vibration
What happens closer to stapes?
basement membrane much narrower responded to higher frequency vibration§
What happens at rest?
Have the organ of Corti- stereocilia of the hair cells are embedded in the tectorial membrane. They are unbent
What happens when basement membrane goes up/rises?
due to the travelling wave initiated by a sound - because of the accessory structure- the stereocilia bends because hair cells are pushed against the accessory structure.(due to the mass of the tectorial membrane) The bending of the hair cells causes receptor potential
What happens when the basement membrane falls?
the hair cells are bent the other way, you geta decrease in the firing frequenc
What happens at rest of the sensory neuron?
at rest, the sensory neurone when cilia are not bent, firing few action potential
tonically active
What happens when the stereocilia are bent one way
they depolarise and the sensory firing rate increases
increase in frequency of action potentials
What happens when the stereocilia are bent the other way?
decrease in the sensory firing rate
decrease in firing frequency
Why do we need accessory structure?
to make a shearing force on the cilia
How does bending the cilia cause depolarisation?
the stereocilia are bathed in endolymph, which is rich in K+
it opens potassium ion channels.
Potassium enters the hair cell down its electrochemical gradient and depolarises it
How does bending hair cell open K+ channels?
hair cells are bound to each other to potassium channels when you bend this structure it physically opens up ion channels.
Sum the hearing system
Outer ear- collects sound and channels to the tympanic membrane which vibrates
Middle ear- the vibration of the tympanic membrane is amplified by a lever system of bones and causes a vibration of the oval window in the inner ear
the inner ear- in cochlea the basement membrane vibrates up and down, that puts shearing forces on stereocilia opening K+ channels
high freq sound causes a vibration of the basilar membrane near stapes
Low-frequency sound causes vibration of basilar membrane far away from stapes
The brain works which hair cells being stimulated and can work out what sound it is either high frequency or low.
How do we localise sound?
Requires 2 functional ears
by:
time of arrival differences
intensity differences
What are the 3 forms of deafness?
conduction deafness- wax, middle ear inflammation, sclerosis of ossicle
sensineural deafness- damage to neural structures such as hair cell damage, damage to 8th nerve etc
tinnitus- continuous ringing/clicking sound in absence of auditory stimuli
What is the vestibular system?
it forms the basis of our sense of balance and acceleration
What does balance involve?
tactile receptors - in contact with the floor
vision
however they are not enough, you need a vestibular system.
Why is the vestibular system important?
it controls aspects of our eye movements (VOR)
What is the structure of the vestibular sensory hair cells?
- the membranous labyrinth is lined with epithelial cells
- in some areas- epithelial cells modified into sensory hair cells
- the surface of the hair cells contain cilia, one of which is at the side of the cell and is larger called Kinocilium (40um)
- The base of the hair cells joins sensory neuron
What are the hair cells of the semi-circular canal?
said to be morphologically polarised
What does morphologically mean
structurally
polarised
one side of cell different to the other
What are hair cells also?
physiologically polarised
What happens at rest in the semi-ciruclar canal of hair cells?
the afferent neuron is tonically active
What happens when the stereocilia is bent in the semi-circular canal?
bent towards kinocillium they depolarises and the afferent firing rate increases
What happens when the stereocilia are bent the other way in the semi-circular canal?
bent away from kinocilium afferent firing rate decreases
Where are hair cells found in semi-circular canals
in the ampulla
Where are the hair cells placed in the semi-circular canal?
they sit on the ridge
the hair cells are embedded in a gelatinous cupula (lump of snot)- the cupula within the ampulla
The cupula fills the whole ampulla- which contains cristae where the hairs are- all in one direction.
the whole of semicircular canal is fluid-filled of endolymph
Where are the kinocillia in the semi circular canal ampulla found?
on the side of the cell facing the vestibule, nearest to the utricle
What is the bony layrinth/skull linked to?
you move head, you move semi- circular canal
What are the hair cells in the semi-circular canals sensitive to during the head movement?
hair cells embedded in gelatinous cupula and surrounded by fluid
when you move the head to left, the semi-circular canals go to left
however, the fluid (endolymph) will relatively move in the opposite direction
(due to inertia it will stay in the same place)
the endolymph will push the cupula and bend the hair cells
What happens when the head turns to left via semi-circular canal?
hair cell points towards utricle
the kinocilia in the left semi-circular canal will be bent towards the vestibule (move to left)
endolymph move to the right
impinge on the cupula
push cupula towards the right
bend hair cells in the left semi-circular canal towards the kinocilium (excited)
bend the hair cells in the right semi-circular canal bend away from the kinocilium (inhibited)
What are the 3 pairs of semi- circular canals in the 3 planes of space?
yaw
pitch
roll
you can figure out which way the head is turning
What are the semi-ciruclar cancals sensitive to?
circular acceleration
What do the semi-circular canals respond to?
sense angular acceleration
What happens when we keep on going circular acceleration?
with constant rotation the endolymph will catch up with the bony labyrinth and hair cells will no longer be stimulated
when rotation stops we get dizzy as relative endolymph movement is reversed
Where are the areas of hair cells in the vestibule?
maculae- one in the utricle and one in the saccule
Where are the cilia?
stuck in a membrane which has calcite crystal
What membrane is the cilia of hair cells on?
embedded in the otolithic membrane
Where doe the hairs face in the semi-circular canal
the utricle
Where does the hair face in the vestibule?
point towards an imaginary line called STRIOLA
Where is the kinocila in the vestibule?
the kinocilia face the striola
What do the different direction of bending cause within the vestibule system?
it will stimulate and inhibit populations of hair cells within the different directions - some are inhibited and some excited
What causes cilia to be pushed in the vestibule system?
Linear acceleration- as the otolithic membrane is heavy so tilting the head will impart a shearing force in the macula of the utricle which therefore cause the cilia to bend
