Hearing - 12.3 Flashcards
Why is hearing considered our most important sense?
Can warn us of danger and can trigger strong emotional response
What do sensory receptors in the ear and muscles provide?
Provides constant information on the body’s orientation in space
What are mechanoreceptors?
Specialized sensory receptors for hearing and balance.
What do mechanoreceptors in the inner ear do?
They convert the energy of sound waves into electrochemical energy that the brain perceives as sound.
What are the three main divisions of the ear?
The outer, middle, and inner ear
What does the outer ear consist of?
The pinna and the auditory canal.
What is the pinna?
Outside flap of the ear - made of skin and cartilage - shaped in a way that enhances sound vibration and focuses them into the ear
What is the auditory canal?
2.5cm long tube - leads to ear drum in the middle ear - amplifies sound waves making them louder
What is the middle ear?
Air filled space - boarded on one side by the Tympanum (ear drum)
What is the Tympanum?
round, elastic structure - vibrates in response to sound waves
What are the ossicles?
Three, tiny interconnected bones in the middle ear (smallest bones in the body)
Vibrations are amplified - act as a lever for the next bone
What three bones does the ossicles consist of?
Malleus - hammer
Incus - anvil
Staples - stirrup
What do the staples specifically do?
Concentrate the vibrations into the membrane covered opening of the inner ear - the oval window
How is the middle ear connected to the throat?
With the Eustachian Tube
What does the inner ear consist of?
The semicircular canals, the vestibule, and the cochlea
What does the semicircular canal and the vestibule contain?
Sensors for balance
What is the cochlea and why is it important?
It is used for hearing
Where mechanical energy of sound is converted into electrochemical energy that is transmitted into the brain
What must the vibrations in the oval window be converted to?
Pressure waves - fluid filled
What does the middle area of the cochlea contain?
The Organ of Corti - organ of hearing
Describe the organ of Corti?
Along the base of organ of corti (basilar membrane) - sensory receptors known as hair cells are attached
Hair cells have thin projections - stereocilia - stick out at the top of the cells
Stereocilia are embedded within the tectorial membrane
What are the thin projections that come out of hair cells?
Stereocilia
Where are the stereocilia embedded in?
The tectorial membrane
What are the hair cells of the organ Corti able to distinguish?
Both frequency (pitch) and amplitude (intensity)
What is frequency?
number of waves that pass through a specific point every second (measured in Hertz)
What do high frequencies stimulate?
Stimulates hair cells close to the oval window
What do low frequencies stimulate?
Stimulates hair cells that are farthest from the oval window
What happens in the cochlea if the noise is louder?
The more pressure the fluid in the cochlea puts on the cells of the basilar membrane
What is noise measured in?
Decibels - any noise over 80dB can be damaging
How is sensory information sent in the brain (the path)?
Sensory neurons carry information through the auditory nerve - to brain stem - to thalamus - then to temporal lobes of cerebrum
What are the three major structures in the inner ear that help us to stand upright and and move without losing our balance?
Semicircular canals, utricle, and saccule
- Help us stand upright and move without losing our balance (equilibrium)
What kind of receptors does the semicircular canals contain?
mechanoreceptors that detect head and body rotation (rotational equilibrium)
Describe the ends of the semicircular canals.
Ends in a buldge - inside each buldge - stereocilia of the hair cells stick to a jelly covering (cupula)
When head moves - fluid moves/bends stereocilia - hair cells send rotational information to brain
What is gravitational equilibrium?
The balance required when moving the head back and forth.
What does gravitational equilibrium depend on?
It depends on the utricle and saccule (together make up the fluid filled vestibule in the inner ear)
What do the saccules and utricles contain?
They contain calcium carbonate granules (otoliths)
Where does otoliths lie?
Otoliths lie in a copula over a layer of hair cells
What happens when the head dips forwards and backwards?
Gravity pulls on the otoliths - puts pressure on the hair cells - they send impulse to brain indicating the position of the brain
What did the ability to distinguish different foods develop as?
An adaptation
What are the four basic tastes?
Sweet, sour, salty, and bitter
What do poisonous plants consist of?
Bitter tasting molecules made of - alkaloid compound
What are the sensory receptors in the bumps on the tounge?
Papillae
How does an impulse travel from tongue to brain?
Taste buds - areas on brainstem - to thalamus - to gustatory Centre of the parietal love
Why do they think that we can distinguish lots of smells (lock and key)?
The odour particles fit like a lock and key on specific chemoreceptors
What are the chemoreceptors in the nose called and where are they located?
Olfactory cells - lining the upper nasal cavity
What is the process of smelling something?
Particles bind with olfactory cells - ion membrane channels open - generates action potential in olfactory cell - directly linked to olfactory bulb opening in brain
From here - impulse is sent to emotional centres of brain (limbic system) and frontal lobe where the perception of smell occurs
How is taste linked to smell?
Molecules from food travel through the nose passages and passages in throat - trigger chemoreceptors - trigger olfactory sensory neuron
What are pheromones?
Substance that aids in the recognition and attraction of a mate
What are pheromones detected by?
Vomeronasal organ
When does Pain occur?
When specialized sensors of nerve endings in the skin are activated by mechanical pressure or chemical signals
If skin is damaged - nerve cells (nociceptors) release chemicals that trigger pain receptors to send stimulus to brain
