Lec 14 Flashcards
Olfactory system
Uses free nerve ending
From air to brain
Olfactory neuron—cilia(dendrite) receptors
Olfactory bulb— synapses are find
Olfactory tract—#2 neuron axon goes to olfactory cortex
Bone between nose and brain
Ethmoid Bone
Cilia(dendrite like)
Cilia project downward into mucous layer
Cilia have odorant receptor proteins GPCRS
Supporting cell
1- stem cell
2- can replace olfactory sensory neurons
Mucous layer
-Odorant must dissolve into this layer
-Odorant must bind to specific odorant receptors(GPCR)
How many different Odorant receptor in human?
400 different odorant receptors
ALL ARE GPCRS
combination of activated receptors and neurons allow us to smell 5000 odors
Signal transduction in olfactory
1-Odor bind to G protein-coupled receptor
2-Activated G protein activate adenylyl cyclase
3-Adenylyl cyclase convert ATP to cAMP(secondary messenger)
4-cAMP open cyclic-nucleotide gated Na channels
5-Sufficient Receptor potential
6-Produce AP at axon hillock
Specialized G protein for olfactory tranduction
Golf
Olfactory sensory pathway
1- olfactory neurons
2- cranial nerve I
3- olfactory bulb
4- olfactory tract
5- olfactory cortex
6.1- limbic system
6.2- cerebral cortex
Olfactory connection with limbic system
Smell is linked to emotion and memory
——— are similar and hand to hand with olfactory
Taste sensors
Each taste buds is ——— taste cells
50-150
Taste cells are
Non-neural
Each taste cell is
Sensitive to particular tastant ligand
Polarized:
—receptor at apical membrane
—1 sensory neuron communication at basal membrane
Intracellular signaling pathway is ——— for each taste cell
Different
Different tastes
Sweet
Umami
Bitter
sour
*different GOCR for each one
Type I support cells
May sense salt when Na enters channel
ENAC
Receptor cells (type II)
Sweet/umami/bitter
Release ATP as messenger
Presynaptic cell (III)
Feels sour
Activate by H(+)
Release serotonin as messanger
Primary sensory neurons
Two different kind
—Sensitive to ATP
—Sensitive to serotonin
Type II pathway
Different GOCR for each taste
Release if Calcium ion
Calcium triggers ATP release
Type III pathway
Ph drop
H(+) enters the cell
Ca rushes in from ECF
Serotonin production
What is sound
Sound is perception and interpretation of air waves
Pressure wave
Sinusoidally varying density of air molecules
Volume/Loudness
Amplitude of a sound wave
Measured in dB
Pitch
Frequency of sound wave
Measured in Hz
External ear
pinna :direct sound waves into ear
Ear canal: air filled space
Boundary of external and middle ear
Tympanic membrane
Tympanic membrane
Drum vibrate
Convert sound wave to mechanical stress
Middle ear
Air filled space
bones from external to internal
Malleus
Incus
Stapes
Boundary middle and inner ear
Oval window
Round window
separate air field from fluid field
Convert mechanical energy to fluid wave energy
Inner ear
Fluid filled
Cochlea + nerves
Cochlea function
Balance
Hearing
Equilibrium
How AP fires?
1- fluid wave created in cochlea by oval window
2- fluid waves push on cochlear duct membrane
3- hair cells bend and ion channels open
4-create electrical signals
5- release neurotransmitters
6- neurotransmitters on sensory cell create AP
Ap travel from sensory neuron to brain by
Cochlear duct
Energy wave moves from ———
cochlear duct to tympanic duct and go back to middle ear from round window
Cochlear duct name
Endolymph
high in K
Vestibular and tympanic duct name
Perilymph
**connected together **
Organ of corti function
Signal transduction
Graded potential
Endolymph composition is similar to
ICF
How hair cells release neurotransmitters
1- Basilar membrane on bottom
2- Ridge of epithelial cell above that(support cells + hair cells)
3- Cilia of hair cells embedded in tactorial membrane
4- fluid wave move tactorial membrane which moves cilia
5- cilia is mechanically gated channels
Which will open by tactorial movement
6-opening cause release of neurotransmitters
Tip link
Cilias are connected together by tip link
Which if you pull on cilia, all cilia will move
Which ion flow when mechanically gated channels open on sterocilia
Ca and K
Excitation and inhibition of cilia cells
When hair cells bend in one direction, cell depolarizes, which increase AP frequency
When hair cells bend in opposite direction, ion channel close and cell hyperpolarize
Sterocilia excitation will produce
Receptor potential which is made by K go inside the cell
as basilar membrane moves further from oval window, it gets
Wider, thinner, more flexible
Which increase the sensitivity to low frequencies
Regional differences
High frequency is sensed in closer distance to oval window
Lower frequency further from oval window
Labeled line coding from basilar membrane
Different pathway
Different input
Different frequencies
Brain can differentiate
Auditory pathway
Sound waves goes to
1- cochlea (left/right)
2- brainstem cross over happens
3- thalamus
4- auditory cortex (left/right)
