BSN PHYSIOLOGY: SPECIAL SENSES PART 2

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The two sensory modalities , we have discussed in previous post, now here is elaboration of the next two sensory modalities i.e sense of hearing, audition and chemical sense(sense of taste) gustation 
Note: Somatosensation is not the part of the curriculum 
Section 2 Chapter#8
Short questions:  
  • Passage of sound waves?
  • Transmission of sound waves in the cochlea?
  • Attenuation reflex?
  • Function of the basilar membrane
  • functions of the bony labyrinth and membranous labyrinth. 
  • Describe the functions of hair cells in the semicircular ducts, utricle, and saccule?
  • Describe the sensory receptors of the internal ear.
  • Function of the spiral organ(organ of corti)?
  • Primary sensations of taste?
  • (sour,salty,bitter,sweet,umami)?
  • Functions of taste buds?
  • Mechanism of stimulation of taste buds?
  • Name the five taste modalities. Name the three types of papillaes that have taste buds.
  • Auditory nervous pathway?
  • Hearing abnormalities?
  • Ear infections(otitis media,labyrinthitis)
  • How the direction of sound can be detected?
  • Describe the physiology of balance?
  • Clinical Module: Describe age-related disorders of gustation, equilibrium, and hearing.? 
IMPORTANT FIGURES:
Fig#8.1,fig#8.2,fig#8.3,fig#8.4,fig#8.5,fig#8.6,fig#8.7(Ross&Wilson)
Fig52-1,2,3,4,7,8,10,fig#53-1,2(Guyton)

Physiology of sound processing & reception:
Steps in the generation of sensory impulses from the ear 
 1. Sound waves enter the external auditory meatus . 
 2. Waves of changing pressure causes the tympanic membrane to vibrate. . 
 3. Auditory ossicles amplify and transmit vibrations to the end of the stapes . 
 4. Movement of the stapes at the oval window transmit vibrations to the perilymph in the scala vestibule . 
 5. Vibrations pass through the vestibular membrane and enter the endolymph of the cochlear duct . 
 6. Different frequencies of vibration in endolymph move specific regions of the basilar membrane , thus stimulating specific sets of receptors cells (hair cells). 
 7. As receptor cell becomes depolarized ; its membrane become more permeable to Ca++ ions . 
 8. In the presence of Ca++ ions , vesicles at the base of receptors cell release neurotransmitter . 
 9. Neurotransmitter stimulates the ends of nearby sensory neurons . 
 10. sensory impulses are triggered on fibers of the cochlear branch of the vestibulocochlear nerve . 
 11. Auditory impulses travel into medulla oblongata , midbrain , and thalamus , and are interpreted in the temporal lobes of the cerebrum.
Equilibrium maintainance:
1) 3 semicircular canals , which 
respond to rotational acceleration , in head motion ( dynamic balance). 
 Vestibular apparatus 
2) saccule and utricle (macular organs) , which Respond to head tilting and linear acceleration (static balance).
Attenuation Reflex:A reflex after a latent period of only 40 to 80 msec to cause contraction of stapedius muscles and to lesser extent to tensor Tympani muscle.
Functions:To protect the cochlea from damaging vibrations caused by excessive loudness
To mask low frequency sounds in a loud environment.
Determine the direction of sound:
                                     A person determine the direction of sound by two principal means 1-Time Lag between the entry of sound into one ear and its entry into the opposite ear I.e if the right ear is closer to the sound than the left ear is, the sound signals from the right ear enter the brain ahead of those from the left ear. 2-Difference between the intensities of the sounds in the two ears.

Auditory Nervous Pathway Flow chart: Cochlea-----Auditory Nerve-------CochlearNucleus -----Superior olivary Nucleus --------Inferior colliculus-----------Medial Geniculate body-------Primary auditory cortex located in the superior gyrus of the temporal lobe.


Papillaes :
1.Fungiform papillae
2.Filiform papillae
3.Vallate papillae
4.Foliate papillae




GUSTATORY PATHWAY:
Afferent fifibers carrying taste information from the tongue are
found primarily in two cranial nerve pairs. a branch of the facial nerve (VII), the chorda tympani,transmits impulses from taste receptors in the anterior two
thirds of the tongue. The lingual branch of the glossopharyngeal nerve (IX) services the posterior third and the pharynx just behind. Taste impulses from the few taste buds in the epiglottis
and the lower pharynx are conducted primarily by the vagus nerve (X). These afferent fifibers synapse in the solitary nucleus of the medulla, and from there impulses stream to the thalamus
and ultimately to the gustatory cortex in the insula.
CLINICAL Considerations:
Taste abnormalities:Aguesia(absence of taste), hypoguesia(Partial loss) , dysguesia(proversion, distortion of taste) , paraguesia(unpleasant perception) etc. 
Follow the UHS past papers for your preps it will help a lot to understand which type of questions can come in the final proff.then distinguish the questions you would have learnt for making concepts and those questions ,you should have to prepare for exams. 
So this is all about special senses! encompasses all the contents and important topics! 
Stay Consistent stay motivated!!!!!!! 
@MahnoorButt

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