Chapter 8 (Sensory Systems) Flashcards
cephalization
- the development of a well defined region of sense organs and nervous integrating centres at the anterior end of the body
- occurs with complex nervous systems
afferent neurons vs efferent neurons
- afferent neurons: internal/external stimuli sent to the brain and spinal cord
- efferent neurons: info. from CNS to the body (somatic motor division and autonomic division)
Nerves are groups of axons from neurons organized in ___.
fascicles
Describe the differences between the layers of connective tissue found in a nerve: endoneurium, perineurium, epineurium.
- endoneurium: surrounds axon + myelin sheath
- perineurium: surrounds each fascicle (bundle of axons)
- epineurium: surrounds each nerve (fascicles with blood vessels)
Afferent sensory neurons enter the spinal cord on the ___ side whereas efferent sensory neurons exit the spinal cord on the ___ side.
dorsal; ventral
Where are bipolar neurons found? What kind of potential occurs within these cells?
the olfactory system; the depolarization of olfactory receptor cells causes a generator potential
Describe the depolarization of an olfactory receptor cell.
- binding of odorant to odorant receptor causes conformational change
- G protein (Golf) is activated and moves through membrane to activate adenylate cyclase
- adenylate cyclase converts ATP to cAMP
- cAMP opens cAMP-gated ion channels; Ca2+ and Na+ enter cell and cause generator potential
- Ca2+ opens Ca2+ activated Cl- channels; Cl- leaves cell (increasing depolarization)
- generator potential opens Na+ channels, triggering AP
vomeronasal organ
detects pheromones released by an animal that can affect another animal’s behaviour
Which type of animal may have taste buds on their external body?
aquatic vertebrates
What are the 5 classes of tastes?
salty, sweet, bitter, sour, umami
Describe the process of signal transduction for salty substances.
- Na+ enters taste receptor cell
- depolarization cases Ca2+ channels to open
- inflow of Ca2+ causes neurotransmitter release
Describe the process of signal transduction for sour substances.
- H+ from sour food blocks K+ channels, preventing K+ to leave the cell (depolarization)
- depolarization opens Ca2+ channels
- inflow of Ca2+ causes neurotransmitter release
Describe the process of signal transduction for sweet substances.
- sweet substance binds to receptor, causing conformational change that activates G protein gustducin
- activated gustducin activates adenylate cyclase, converting ATP to cAMP
- cAMP activates protein kinase that phosphorylates and closes K+ channels
- K+ cannot exit = depolarization, which opens Ca2+ and stimulates neurotransmitter release
Describe the process of signal transduction for bitter substances.
- binding of bitter substance causes conformational change in G protein transducin
- transducin activates phospholipase C (PLC) which catalyzes conversion of PIP2 into second messenger IP3
- Ca2+ released from storage and triggers neurotransmitter release
baroreceptors vs tactile receptors vs proprioceptors
- they are all types of mechanoreceptors
- baroreceptors are found in blood vessel walls
- tactile receptors are found on body surfaces
- proprioceptors monitor body position
trichoid sensilla vs. campaniform sensilla
- a trichoid sensillum is associated with a hairlike projection of the cuticle
- a campaniform sensillum is associated with a dome-shaped projection of the cuticle
[sensillum=sensory receptor]
root hair plexus
- wraps around hair follicle
- stimulated when hair follicle is displaced
- phasic receptors: adapt rapidly to stimulus, response diminishes quickly)
Ruffini corpuscle
- sensitive to skin stretch and joints
Pacinian corpuscle
- composed of layers of lamellae (modified Schwann cells)
- rapidly adapting
- sensitive to both beginning and end of pressure stimulus
free nerve endings
- embedded in surface epithelium
- associated with accessory structures
Describe the process of signal transduction in a vertebrate hair cell.
- at rest, hair cell is slightly depolarized; intermediate frequency of action potentials
- if pressure signal causes stereocilia to pivot towards kinocilium: K+ channels open and K+ enters = depolarization = influx of Ca2+ = increased neurotransmitter released = increased frequency of AP
- if pressure signal causes stereocilia to shift away from kinocilium, K+ channels close = hyperpolarization, Ca2+ gates close = less neurotransmitter release = reduced frequency of AP
The K+ channels found on stereocilia are what kind of channels?
mechanically gated ion channels
What kind of channels are the Ca2+ channels in hair cells?
voltage gated ion channels
The pinna and auditory canal make up which part of the ear?
outer ear
