Sensory physiology- mechano and thermo sensation Flashcards
What is a TRP channel?
A transient receptor protein
What are Pacinian corpuscles?
Phasic receptors that are sensitive to vibrations
What are Merkel’s disks?
Sensitive and important for sensing light touch
What are hair follicle receptors?
Detect when a hair is stretched and are rapidly adapting phasic receptors so can detect a moving insect but not a still one
What are Ruffini’s endings?
Sensitive to skin stretching and help to determine the location of the body
Describe the external structures of the outer ear
The pinna and the auditory canal
What are the small bones called in the middle ear?
Malleus
Incus
Stapes
What is the malleus also known as?
Hammer
What is the incus also known as?
Anvil
What is the stapes also known as?
Stirrup
What do the malleus, incus and stapes do?
Transfer sound waves to the inner ear
Describe what the stapes do?
Presses the oval window membrane and transmits pressure to the inner ear
What is the second membrane in the middle ear called?
The round window
Where is the inner ear?
Embedded within the skull and consists of a series of fluid-filled membraneous sacs and canals
Where are the mechanoreceptors (hair cells) in the ear?
Located between two membranes- the basilar and tectorial membranes
What is the organ of Corti?
A structure in the cochlea of the inner ear which produces nerve impulses in response to sound vibrations
What does the organ of Corti consist of?
Hair cells and supporting cells lying between the tectorial and basilar membranes
What happens when the basilar membrane is flexed?
When the basilar membrane is flexed it bends the stereocilia embedded in the overlying tectorial membrane
How does the movements of the stereocilia affect sound movement?
The movements of the stereocilia are transduced in action potentials in the cochlear nerve
How are hair cell’s stereocilia connected?
By tip links
Where are the mechanosensitive ion channels located in the stereocilia?
Near the tips and are involved in sound transduction
Describe signal transduction in the vertebrate hair cell
Deformation of the stereocilia leads to the opening or closing of the mechanosensitive ion channels
When the ion channels open, K+ will enter the cells
Ca2+ enters then neurotransmitter is released
How are frequencies detected in the cochlea?
Pressure waves of different frequencies flex the basilar membrane at different locations
Do low or high frequencies travel further?
Low
How does the ear know abound sound frequency?
Depending on what hair cells are activated
Describe the structure of the inner ear
3 semi-circular canals arranged in planes
The base contains a swelling (ampulla) and a series of sacs including the utricle and saccule
What class of animals are the only ones with a cochlear?
Mammals
Where are the mechanoreceptors of the utricle and saccule found?
In the maculae
Where are the hair cells of each macula?
Embedded in a gelatinous matrix that is overlain with a series mineralised otoliths
What are the otoliths made of?
Calcium carbonate
What do the utricle and saccule do?
Detect gravity and are important for determining the position of the body
What do the semi-circular canals consist of?
A fluid-filled tube a swelling (ampulla) at the bottom
What is the fluid in the semi-circular canals?
Endolymph (high conc. K+)
What does ampulla contain?
A neuromast that senses pressure
Where are the hair cells in the semi-circular canals?
Embedded in a cup-shaped gelatinous mass called the cupula
What is the state of the hair cells of the neuromast at rest?
Partially depolarised
What is the state of the hair cells in the neuromast when the head is tilted?
The fluid exerts pressure in the opposite direction causing the stereocilia of the hair cells to pivot thus either depolarising or hyperpolarising depending on the orientation
Describe insect ears?
Some have tympanal membranes (eardrums) in their legs
Sound waves are transmitted through the trachea within the legs
Mechanoreceptors in the legs can discriminate sound frequencies
Describe how TRP proteins work?
They span the membrane and when open allow Na+ and Ca2+ to enter
What specialized part do thermo-TRP have?
A C-terminal domain that is responsible for thermosensation
Describe TRPA1 in snakes
Important for the infrared sense in snakes
Located in the trigeminal nerve fibres of the pit organs
What part of the brain regulated body temperature in mammals?
Hypothalamus
