Lecture 38

Question 1

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

Answer 1

Sensory epithelia

nose, ears, and eyes

Question 2

_____ ____ present in the epithelium act as transducers. explain what this means (fill in the blank and answer the question)

Answer 2

sensory cells

transducers convert signals from the environment into an electrical form that can be interpreted by the CNS

Question 3

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.

Answer 3

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

Question 4

All sensory cells are either neurons or ___ _____.

Answer 4

neuron like

Question 5

Describe the apical end and basal end of a sensory cell

Answer 5

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

Question 6

describe where exactly olfactory sensory neurons can be found. what does this type of tissue need in order to function?

Answer 6

the olfactory epithelium of the nasal cavity

the sensory surfaces of epithelium must be kept moist and protected by a layer of mucus

Question 7

Describe the type of neuron olfactory sensory neurons in terms of the direction they face and the path their neurons transmit electrical signals along.

Answer 7

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

Question 8

Where are supporting cells for olfactory neurons found? what is their main function?

Answer 8

between neurons

they hold the neurons in place and separate them from one another

Question 9

basal cells in the epithelium are in contact with what?

Answer 9

the basal lamina

Question 10

What is an important structural feature of the dendrites of olfactory sensory neurons? what is present on these?(include what type it is)

Answer 10

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”

Question 11

True or False: each olfactory neuron can only smell a single odor. explain

Answer 11

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)

Question 12

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.

Answer 12

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

Question 13

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)

Answer 13

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

Question 14

Describe where an action potential travels after it is generated in an olfactory sensory neuron

Answer 14

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)

Question 15

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.

Answer 15

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)

Question 16

Compare and contrast “neural stem cells” in the process of the regeneration of olfactory neurons. (include how their position affects their function)

Answer 16

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)

Question 17

Describe what odorant receptor proteins have to do with the development of an olfactory neuron’s axon.

Answer 17

Odorant receptor proteins help in axonal guidance to the correct glomerulus in the olfactory bulb (by guiding the migration of the growth cone)

Question 18

State one of the few instances of adult neurogensis

Answer 18

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

Question 19

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.

Answer 19

neurospheres

neurospheres can differentiate into both neurons and/or glial cells

Question 20

What did we learn from planaria freshwater flat worms in terms of stem cell characteristics? (NSI)

Answer 20

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

Question 21

Describe the characteristics of the stem cells in the hippocampus (cognitive and molecular)

Answer 21

they are involved in learning and memory formation

There is a continuous turnover of cells in the hippocampus

Question 22

What is the plasticity of the adult brain associated with?

Answer 22

The plasticity of the adult brain is associated with the turnover of a specific subset of neurons in the hippocampus

Question 23

About how many fresh neurons are generated every day in a human?

Answer 23

1400

1.75% of the entire population of neurons is replaced per year

Question 24

describe the mechanism that give hope for many applications of stem cells to treat conditions

Answer 24

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)

Question 25

Cultures established from self-renewing regions of the brain and fetal brain tissue show ____, or clusters of neural stem cells. State the types of cells that these thes can differentiate into. (fill in the blank and answer the question)

Answer 25

neurospheres

neurospheres can differentiate into both neurons and/or glial cells

Question 26

Cultures established from self-renewing regions of the brain and fetal brain tissue show ____, or clusters of neural stem cells. State the types of cells that these these can differentiate into. (fill in the blank and answer the question)

Answer 26

neurospheres

neurospheres can differentiate into both neurons and/or glial cells

Question 27

Enhancment of neurogenesis, through activation of the ____ ____ ____ ____, may facilitate neuronal repair and recovery of cognitive function

Answer 27

quiescent stem cell pool

Question 28

What occurring in the adult brain during learning? what effect does this have on stem cells?

Answer 28

long-term potentiation (LTP) and in vitro depolarization (of neurons)

this potently activates quiescent stem cell proliferation

Question 29

There is a subpopulation of stem cells that is stimulated by something other than LTP and in vitro depolarization. What does this subpopulation of stem cells respond to and explain a clinical application of this mechanism

Answer 29

some stem cells are activated by norepinephrine (NE)

NE-mediated antidepressant treatment is thought to be able to alleviate depression

Question 30

List the 3 current methods of inducing neurogenesis in the adult brain. identify which one is currently used to treat many neurodegenerative diseases and psychiatric conditions

Answer 30

electrical stimulation such as deep brain stimulation and electroconvulsive shock

Learning depolarization (LTP)

NE antidepressants

deep brain stimulation and electroconvulsive shock are currently used to treat many neurodegenerative diseases and psychiatric conditions

Question 31

beginning with a therapy, such as learning depolarization (LTP), describe the mechanism by which new neurons may be made. (be specific with locations)

Answer 31

hippocampal neurons become quiescent stem cells

quiescent stem cells become proliferating precursors

the precursors become newborn neurons

Question 32

What did we learn from planaria freshwater flat worms in terms of stem cell characteristics? (NSI)

Answer 32

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 cannibalism” where neighboring cells phagocytose apoptosed cells

x rays will destroy the stem cell regenerative abilities

Question 33

What did we learn from planaria freshwater flat worms in terms of stem cell characteristics? (NSI)

Answer 33

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 cannibalism” where neighboring cells phagocytose apoptosed cells

x rays will destroy the stem cell regenerative abilities

Question 34

What is the term that describes when a non-mammilian organism can regenerate lost tissues/organs? how does this occur?

Answer 34

transformation

differentiated muscle cells near the missing tissue reenter the cell cycle, de-differentiate to become embryonic cells and the proliferate to form a limb bud (just like embryo’s do)

Question 35

State what the rods and cones in the eyes are responsible for sensing.

Answer 35

Rods = Night vision

Cones = Color detection