Lecture 38 Flashcards
Give the term that refers to “a specialized epithelium that covers certain parts of the body in order to sense” and give 3 examples of places you may find this type of tissue
Sensory epithelia
nose, ears, and eyes
_____ ____ present in the epithelium act as transducers. explain what this means (fill in the blank and answer the question)
sensory cells
transducers convert signals from the environment into an electrical form that can be interpreted by the CNS
State the corresponding sensory cells type for the following body parts.
Eyes:
Ears:
Nose:
identify which of these 2 types of sensory cells is able to be replenished.
Eyes: photoreceptors (NSI not super important)
Ears: auditory hair cells (NSI)
Nose: olfactory sensory neurons
olfactory sensory neurons are able to be replaced nearly every month
All sensory cells are either neurons or ___ _____.
neuron like
Describe the apical end and basal end of a sensory cell
the apical end has a specialized structure the detects an external stimulus and converts it to a change in membrane potential
The basal end makes a synapse with neurons that relay the sensory information to specific sites of the brain
describe where exactly olfactory sensory neurons can be found. what does this type of tissue need in order to function?
the olfactory epithelium of the nasal cavity
the sensory surfaces of epithelium must be kept moist and protected by a layer of mucus
Describe the type of neuron olfactory sensory neurons in terms of the direction they face and the path their neurons transmit electrical signals along.
olfactory sensory cells are bipolar neurons
with a dendrite facing the extracellular environment and
an axon that travels along the olfactory nerve to the olfactory bulb in the brain
Where are supporting cells for olfactory neurons found? what is their main function?
between neurons
they hold the neurons in place and separate them from one another
basal cells in the epithelium are in contact with what?
the basal lamina
What is an important structural feature of the dendrites of olfactory sensory neurons? what is present on these?(include what type it is)
many tiny hair-like cilia that protrude from the dendrite
the free surfaces of cilia have “odorant receptor proteins” (olfactory receptors) which are “g protein coupled receptors”
True or False: each olfactory neuron can only smell a single odor. explain
False
each neuron only expresses one of these g protein coupled receptor genes, so they can only recognize ONE CLASS of odorant molecules (may include a variety of odor molecules)
(this affinity is variable depending on how well the ligand binds to the receptor)
by what mechanism do olfactory neurons respond to an odor in order to identify it? State what exact characteristic of an odor molecule is recognized by the g protein coupled receptor on an olfactory sensory neuron.
all olfactory neurons respond by a “common mechanism”
the “structural features” of odorant molecules is what is recognized by the g protein coupled receptor on an olfactory sensory neuron
Describe in detail the mechanism by which an olfactory receptor binds to, recognizes, and sends a signal from a single odorant molecule (start with activated olfactory receptor and end with production of action potential)
an activated olfactory receptor activates an intracellular G-protein (Golf)
This activated Golf then activates “Adenylate Cyclase” to produce cAMP
the cAMP opens ion channels in the plasma membrane to cause an influx of Sodium and Calcium into the cell
This influx of positive ions causes the neuron to depolarize, generating an action potential
Describe where an action potential travels after it is generated in an olfactory sensory neuron
they go to relay stations in the brain called “glomeruli” which are located in the “olfactory bulbs” of the brain
although olfactory neurons expressing the same odorant receptor are located in different places in the olfactory epithelium, their axons will converge on the same glomerulus (bc they are all expressing the same odorant)
describe the arrangement (wiring) of olfactory neurons with respect to the glomeruli they may reach and how their specific odorant molecule they receive can influence that.
although olfactory neurons expressing the same odorant receptor are located in different places in the olfactory epithelium, their axons will converge on the same glomerulus (bc they are all expressing the same odorant)
(there are many glomeruli for each type of odorant molecule)
Compare and contrast “neural stem cells” in the process of the regeneration of olfactory neurons. (include how their position affects their function)
neural stem cells reside among the basal cells in the olfactory epithelium and generate replacement neurons for ones that are lost (each olfactory neuron survives 1 month)
these are basal stem cells that are in contact with the basal lamina while they are a stem cell, however once they lose contact with the basal lamina, they will differentiate into an olfactory neuron (cant go back)
Describe what odorant receptor proteins have to do with the development of an olfactory neuron’s axon.
Odorant receptor proteins help in axonal guidance to the correct glomerulus in the olfactory bulb (by guiding the migration of the growth cone)
State one of the few instances of adult neurogensis
regeneration of the olfactory receptor cells in the CNS
this is the topic of much research that could help with nervous tissue issues in pt’s
Cultures established from self-renewing regions of the brain and fetal brain tissue show ____, or clusters of neural stem cells, neural cells and glial cells. State the types of cells that these neurospheres can differentiate into.
neurospheres
neurospheres can differentiate into both neurons and/or glial cells
What did we learn from planaria freshwater flat worms in terms of stem cell characteristics? (NSI)
20% of their cells are neoblasts (stem cells) that basically work to adjust the number of cells the organism has, based on it’s environment
it shrinks via “cell canaballism” where neighboring cells phagocytose apoptosed cells
x rays will destroy the stem cell regenerative abilities
Describe the characteristics of the stem cells in the hippocampus (cognitive and molecular)
they are involved in learning and memory formation
There is a continuous turnover of cells in the hippocampus
What is the plasticity of the adult brain associated with?
The plasticity of the adult brain is associated with the turnover of a specific subset of neurons in the hippocampus
About how many fresh neurons are generated every day in a human?
1400
1.75% of the entire population of neurons is replaced per year
describe the mechanism that give hope for many applications of stem cells to treat conditions
Neural stem cells can be grafted into the adult brain where they can adjust their behavior to the new location
(stem cells from the hippocampus ,when implanted into the olfactory bulb, give rise to neurons that become correctly incorporated into the olfactory bulb)
