Module B: Sensory Systems Flashcards
Processing centres of sensory systems are found in the
spinal cord, thalamus, brainstem, and cerebral cortex
Common features of senses are
- they require a physical stimulus
- events transform stimulus into nerve impulses
- response of signal gives rise to perception of sensation
Definition of sensation is
the detection of a physical stimulus
Definition of perception is
the interpretation modified by experience
Some senses that we do not posses are
fish - pressure (mechanoreceptors) magnetic electrical fields and electrosensory systems
insects: hearing organs on legs
What is involved in modality?
signal transduction, action potential, receptor specificity
neurons from specific receptors are modality specific
Classes of receptors in humans
mechanoreceptors, chemoreceptors, thermoreceptors, photoreceptors
Intensity of stimulus is determined by
Stimulus amplitude. This is coded by the number of activated neurons and the frequency of impulses
How many taste receptors in one taste bud?
50-150
How many taste buds are in the tongue?
2000-5000
At what concentrations are papillae most selective?
low concentrations, they lose selectivity at higher concentrations
Taste receptors/cells synapse with…
gustatory afferant axons at basal end
Activation of taste receptor leads to…
hyperpolarisation or depolarisation
which leads to an increase in neurotransmitter or decrease in activity
allows two or more taste stimuli to be responded to by a single receptor cell
Describe transduction mechanisms of bitterness, sweetness, and umami
- Specific G-protein receptors
- Activate Phospholipase C & 2nd messenger IP3
- Na channels open, depolarisation
- Voltage gated calcium channels release internal calcium stores
- Neurotransmitter release (serotonin, ATP, glutamate)
Receptors for bitterness are..
T2R
30 types
Can’t distinguish bitter compounds
Receptors for sweetness are..
T1R
Need two types (T1R2 and T1R3) together
Receptors for amino acids/umami are…
T1R
Need two types (T1R1 and T1R3)
Detects only some amino acids (i.e. in protein such as glutamate and aspartate)
Receptors for saltiness are…
Amiloride-sensitve sodium channels are used, causing depolarisation and calcium release
ENaC
Receptors for sourness are…
Protons are transported through amiloride-sensitive sodium channels, inhibiting potaassium influx.
Nerves associated with taste are:
7: Facial, majority of tongue
9: Glossopharyngeal, back of tongue
5: Vagus, start of throat
Taste nerves go to
the nucleus of the solitary tract/gustatory nucleus
all information is then carried to the ventral posterior medial nucleus of the thalamus before moving to the bustatory cortex (both insula and frontal operculum)
Mucous secreted by the oflactory glands contain…
- Mucopolysaccharides
- Antibodies
- Odorant binding proteins
Oflactory cells are created from basal stem cells every…
4-8 weeks
Olfactory receptors when activated…
- Activate adenylyl cyclase
- Increase cAMP levels
- Activates Ca/Na channels
- Chloride leaves cell through Ca gated Cl channels
- Calcium can also leave the cell through Na/Ca exchangers
- Membrane depolarisation
Olfactory receptors are specific to…
One or a few types of odorant molecules
Vomeronasal organ has….
V1R and V2R genes
