BINGHAMTON PSYC 362 EXAM 2

T/F Both taste cells and olfactory cells are neurons

False

T/F The greater the intensity of a tasting stimulus, the greater the depolarization of a taste cell will be

True

T/F All five sensory systems undergo the same transduction process, using similar types of sensory receptors

False

T/F Each taste bud is specialized to respond to a specific taste quality (i.e. salty)

False

T/F Different type of papillae are localized to specific regions on the tongue

False

T/F Certain receptors specialized to convey temperature information also contribute to our perception of taste

True

T/F Labeled line theory is the most up-to-date theory on how taste information is processed

False

T/F Anosmia can be the cause of psychopathological states

True

T/F Like most neurons, olfactory receptor cells are not supplied by postnatal neurogenesis

False

T/F Taste receptor cells use action potentials to transmit their messages to the next neuron

False

T/F All olfactory receptors mediate an EPSP through the same biochemical mechanism

True

T/F Taste receptor cells transduce all tastants information through the same receptor mechanisms

False

What process involves converting sensory stimuli unto an electrical message used by the nervous system?

A. Transduction

B. Reception

C. Transmission

D. Perception

A. Transduction

Which of the following is not a type of response that a sensory cell can have to sensory input?

A. EPSP

B. IPSP

C. Action Potential

D. Threshold potential

D. Threshold potential

What information does temporal coding provide?

A. Whether a stimulus is present

B. How much of a stimulus is present

C. What type of stimulus is present

D. All of the above

C. What type of stimulus is present

Which of the following best describes a property of tastants?

A. They are all molecules that the body can taste

B. They are chemicals that are biologically important

C. They are chemicals that interact with specific receptors

D. All of the above

D. All of the above

Which of the following taste qualities acts at an ion channel?

A. Sour

B. Sweet

C. Bitter

D. Umami

A. Sour

Olfactory receptor cell bodies are embodied in which of the following tissues:

A. Olfactory epithelium

B. Cribriform plate

C. Glomeruli

D. Olfactory bulbs

A. Olfactory epithelium

In which structure do we find a fully segregated topographical map?

A. Glomeruli

B. Olfactory epithelium

C. Papillae of the tongue

D. Taste buds

A. Glomeruli

The location of the primary olfactory region in the cerebral cortex is the _______________.

A. Insular cortex

B. Nucleus of the solitary tract

C. Piriform cortex

D. Gustatory bulb

C. Piriform cortex

Which of the following is not true of the olfactory bulbs?

A. They house the primary olfactory cortex

B. They contain glomeruli

C. They send olfactory information to the brain

D. They are topographically organized

A. They house the primary olfactory cortex

Which of the following may occur with damage to the piriform cortex?

A. You would no longer be able to identify the source of the smell

B. You would no longer be able to tell if a smell is good or bad

C. You would no longer be able to tell if a food is salty

D. You would lose all sense of smell

A. You would not longer be able to identify the source of a smell

Which of the following underlies depolarization by a sweet taste quality?

A. Sugar binds to a receptor, activating the G-protein and leading to production of cAMP to close potassium channels

B. Sugar binds to a receptor, activating the G-protein and leading to activation of phospholipase C to increase calcium levels

C. Sugar binds to the receptor which opens a sodium channel, allowing sodium to flow into the cell

Sugar binds to the receptor which blocks a potassium channel, blocking potassium efflux

A. Sugar binds to a receptor, activating the G-protein and leading to production of cAMP to close potassium channels

The T2 family of receptors is responsible for which type of information?

A. Bitter taste

B. Sweet taste

C. Temperature-related taste information

D. Toxic airborne chemicals

A. Bitter taste

Which of the following differentiates supertasters from the rest of the population?

A. They have more taste buds and receptors

B. They have more papillae that are specific to sweet taste qualities

C. They are more sensitive to sour tastes

D. They are picky eaters and are therefore less healthy

A. They have more taste buds and receptors

Which of the following is dysosmia not a symptom of?

A. Major Depressive Disorder

B. Alzheimer's Disease

C. Parkinson's Disease

D. Schizophrenia

A. Major Depressive Disorder

Which of the following is a difference between the gustatory and olfactory systems?

A. One responds to chemical stimuli, the other does not

B. One can be disrupted by damage to the sense organ, in the other the sense organ cannot be damaged directly

C. One transmits information directly to the primary sensory cortex, the other does not

D. One has receptor cells that respond to only one stimulus, the other has receptor cells that respond to multiple stimuli

D. One has receptor cells that respond to only one stimulus, the other has receptor cells that respond to multiple stimuli

T/F Drugs that increase inhibitory synaptic activity or ones that increase excitatory signaling can both be detrimental to effective brain function.

True

T/F The NMDA glutamate receptor allows multiple types of ions to flow into the cell.

True

T/F Removing or blocking AMPA receptors within the visual cortex will likely result in total loss of sight.

True

T/F The brain undergoes the most rapid growth early in development, and then continues to grow throughout the whole lifespan

False

T/F The PNS forms from neural crest cells

True

T/F Synaptic pruning occurs only during gestation

False: Throughout adolescence into adulthood

Cells that represent the ancestors of neurons in the CNS are found in the:

A. Ectoderm

B. Mesoderm

C. Endoderm

D. Echinoderm

A. Ectoderm

Which of the following describes the ventricular zone?

A. It follows a genetic code to determine the size of our nervous system

B. It is the space that will later become the ventricles of the brain

C. It releases sonic hedgehog

D. Neurons follow radial glia and the VZ tells them where to stop migrating

A. It follows a genetic code to determine the size of our nervous system

Which of the following is the correct order of neural development?

A. Neurogenesis > Migration > Differentiation > Synaptogenesis

B. Differentiation > Migration > Neurogenesis > Synaptogenesis

C. Synaptogenesis > Differentiation > Neurogenesis > Migration

D. Neurogenesis > Differentiation > Synaptogenesis > Migration

A. Neurogenesis > Migration > Differentiation > Synaptogenesis

Axon formation and growth occur at which developmental stage?

A. Synaptogenesis

B. Neurogenesis

C. Differentiation

D. Axogenesis

A. Synaptogenesis

Which of the following is not true about development of the nervous system?

A. Once the nervous system is formed, it remains unchanged throughout the rest of the lifetime

B. The brain changes in size throughout the lifetime

C. The genetic code determines only part of how the brain develops

D. Chemical signaling plays a role in how the brain develops

A. Once the nervous system is formed, it remains unchanged throughout the rest of the lifetime

Which of the following is not true of asymmetrical cell division?

A. It occurs after the ventricular zone has reached its full size

B. It produces neurons that migrate to the marginal zone

C. Some cells produced are no longer capable of cell division

D. It begins shortly after birth

D. It begins shortly after birth

Somatosensory system

Transduce mechanical stimulation of the skin, injury to the skin and/or changed in temperature into neural impulses

cell traduces stimulation --> CNS (where it is understood)

Mechanosensation

- Touch

- Pressure

- Vibration

Nociception

Can damage tissue

- Pain

- Temperatuer

- Itch/ injuries

Sensory Structures

Specialized neurons in skin for different stimuli

- Free nerve endings

- Hair follicle Receptors

MOST IMPORTANT ONES*

- Merkel's disc

- Meissner's corpuscle

- Pacinian corpuscle

- Rufinni's ending

Receptive field

- Every neuron (skin + CNS) has a receptive field

- The set of stimuli that are sufficient to trigger the response (action potential) of a sensory receptor

- Include 1) WHAT stimulus is detected and 2) WHERE that stimulus must occur to be detected

Olfactory receptor neuron? One particle in the air

Taste cell? Particular tasting quality (present/ absence of salt)

Vibration

Non damaging= Mechanosensation

1. Pacinian corpuscles (deep within skin)

2. Receptive fields are large (covering large portions of skin)

3. Fast adapting

- Sensory cell fires, continued --> stop tracking, only marks beginning and end of a stimulus (we don't care about continuous contact like clothes on our skin or sitting in a chair- sensory habituation)

-Regular frequency contacts to the skin

- Tiny process w large receptive field - vibrations travel through matter

-MVP --> APs (threshold)

- Sensory receptor end is onion like (series of membranes surrounded by fluids)

- Mechanical displacement PHYSICALLY OPENS Na+ channels, depolarized --> AP if threshold is reached

TRANSDUCTION: Propagates down axon, nerves, dorsal root ganglia, CNS

- A-BETA FIBERS (medium sized, myelinated - saltatory conduction) to dorsal root ganglion and spinal cord

Pacinian corpuscles

- Specialized organ w microscopic processes

- Nerve fiber w direct connection to CNS

- Depolarized when vibration is present to their receptive field

- Cell bodies are found in dorsal root ganglia (somatic, just outside spinal cord)

-Unipolar cell spilt axon: one end towards corpuscle structure and the other into dorsal spinal cord

Series of ganglia from right or left (lateralized pathway, everything is on the same side) --> cervical, sacral

Skin --> spinal cord connection

Sensory adaptation

Slow adapting = more continuous

Rate of AP changes: ** Degree of increased rate is proportional to intensity

Meissner's Corpuscle

Light touch, adapt quickly/fire slowly, larger receptive fields (cannot distinguish braille)

Merkel's disc

Adapt slowly and fire continuously

discriminatory touch (discreet fine contact), tiny receptive field (microscopic), detected in overlying skin, can tell stimuli apart very well

Ruffini's ending

- respond to STRETCH of skin of large area overlying skin (where limbs are in space - proprioception)

- adapt slowly to stretch

- do not provide complete representation of form

Non-damaging pathway

DORSAL COLUMN SYSTEM:

-Unipolar neurons (dorsal root ganglion) receive input from the skin and send axons into the spinal cord

- Join dorsal columns and ascend dorsal column nuclei in MEDULLA (FIRST SYNAPSE)

- Crossover joining MEDIA LEMNISCUS and synapse within the ventral posterior and ventral lateral nuclei of THALAMUS - SECOND SYNAPSE

-Thalamic cells RELAY info to post-central gyrus in region of PARIETAL LOBE called SOMATOSENSORY CORTEX

Nerve, dorsal root ganglion, dorsal column, medulla CROSS OVER, brain stem, dorsal column nuclei?

Topographic maps

Cervical, thoracic, lumbar, sacral - each segment has pair of dorsal root ganglia (left and right)

DRG --> connected by nerves to particular part of skin (dermatomes) --> reflect levels of segments in spinal cord --> can help identify injuries

Lumbar 1- Axia

Lumbar 5/6 - Lateral leg, plantar foot

Somatosensory cortex is similar across all people

HOMUNCULUS MAP - funny looking person showing importance of location dedication of neurons/location

Plasticity

Nervous system changes function based on experience

- neighbors (thumb - eyes and digit two)

Lose limb? Section of somatosensory cortex changes - experience induced change

Piano players? --> Fingers hold larger section of somatosensory cortex --> neurons are relocated to fingers area

Limits of plasticity

Phantom limb: Never lose sense of limb being there, can perceive intense pain

Pain sensation

- The perception of pain is generated when mechanical pressure on the skin is sufficient to cause tissue damage (bleeding, swelling, tissue damage, high temp/burns, chemical damage, itch)

Chemicals activate neurons --> sensory response = healing

Nociceptors

- FREE NERVE ENDINGS in the skin detect pain

- Detect painful stimuli and transmit them to nervous system

Damage: cells that have been damaged can SEROTONIN, PROSTAGLANDINS AND LEUKOTRIENES that act on receptor on free nerve ending

NSAIDs (Asprin, ibuprofen) are inhibitors of the synthesis of these molecules

C/A delta fibers (C fibers have a small diameter and are non myleinated)

Chemical activation is perceived as pain

histamine and itch

Histamine, a protein released during an allergic reaction.

The sites activated in the brain when we itch are very similar to those switched on when we're in pain.

Cold/ Hot sensing

Pain/ temp system

C and A -beta fibers

Pain Pathway

- Dorsal root ganglion cells carry pain info and release GLUTAMATE AND SUBSTANCE P onto dorsal horn neurons

- Dorsal root neurons send an axon that crosses to the other side and head toward brain via SPINOTHALAMIC TRACT

-Axons w/I spinothalamic tract ascend to synapse on thalamic neurons within the ventral posterior nucleus of the thalamus

-Thalamic neurons project up into somatosensory cortex

Difference in non damaging and pain pathway

Same start and stop

Same number of stops

Different switchover (Decussation)

Brown-Swquard Syndrome

Loss of mechanosensation on the same side as the injury, loss of pain opposite side of the injury

Olfaction

Detection of chemicals that have been aerosolized in air chemicals we can smell = odorants: interact w/ olfactory receptor

-hyposmia, anosmia, dysosmia

-bypasses thalamus, no clear cross because there is no true left and right side of nose

Hyposmia

Compromised sensitivity of smell, often accompanied with lowered ability to taste

- Caused by upper respiratory infection

Can be triggered by head injury

Anosmia

Absence of smell

- can be a cause of affective disturbances (anxiety and depression- why? - smells have affective component)

Can be triggered by head injury

Dysosmia

- Symptom/ consequence of neurological/psychiatric disease

- Response to odorants are atypical, perception is dysfunctional

- Parkinsons, Alzheimers, Schizophrenia

Olfactory system (transduction to perception)

1. Sense organ within nasal cavity - designed to enhance chances of air hitting receptor neuron

2. Olfactory receptor neurons = TRANSDUCTION

- Inhalation brings chemicals in air in contact with OLFACTORY EPITHELIUM

Olfactory receptor neurons (ORNs)

- ORNs within olfactory mucosa can send processes out into the olfactory space that express receptors sensitive to aromatic substances

- Constantly replaces in normal human individual (ADULT NEUROGENESIS: ongoing to restore function)

-ORNs are fragile cells exposed to the environment and must be replaced

- Born from neurogenesis in the skull, migrate from brain along nerve through cribriform plate into olfactory mucosa (differentiation) --> becomes ORN --> synaptogenesis (axons can be broken from whiplash = hyposmia)

Site of TRANSDUCTION: have receptor to which odorant binds

Olfactory mucosa: only soma fits so dendrites hang to collect odorants from the air

Have receptor to which odorant binds

Olfactory receptor genes

- The receptor is a protein in the dendrites of the ORN (Metabotropic, Ligand = odorant)

- About 1000 genes encode olfactory receptors (Each belong to 1/4 subfamilies, only 400 are function - this is because a large of the genome is for sense of smell)

-Each ORN expresses only one type of olfactory receptor gene

* 1 odorant = 1 gene, 1 odorant doesn't equal 1 "smell"

-Each ORN has one receptor

More receptors = higher acuity (ability to differentiate/discriminate smells)

Number of transcribed olfactory receptor genes

Elephants have best sense of smell

Humans have about 396 ORGs

Whales (CETECEANS) do not smell, only taste - very low # of ORGs

Olfactory receptor signaling

- G-protein coupled, metabotropic receptors

- Odorants activate the receptors --> activate production of cAMP --> triggers [inward] Na+ and [outward] Cl- channels to open --> depolarization

- Action potentials (rate codes)

- Odorant binding = EPSP

- DO have threshold potential (EPSP always makes it to the end)

Olfactory bulb

- Axons of ORN travel through bone to SYNAPSE on cells in the GLOMERULI (end of ORNSs) of the OLFACTORY BULB

-When active, they release neurotransmitter onto cells mitral cell dendrites in the glomeruli

Left and right olfactory bulbs just above bone into brain

Semi- segregated localization of olfactory receptors in the epithelium

(Green, yellow, blue, white diagram)

-ORN expresses 1/400 odorants

Rose vs. smoke - can predict what odorant by where ORN is

Segregation of olfactory receptor projections to glomeruli

- Each ORN expresses one type of receptor

- Each glomerulus receives input from groups of ORN that express the same receptor

- The inputs related to one odor are divided up in the olfactory bulb

Each glomerulus is specialized for a particular odorant and ignores the other 399, fully segregated

Each odorant activated a distinct representation in glomeruli

"fingerprint" is unique indicator of smell

- glomeruli activity map notes each signature

Segregation of representation continues into the cerebral cortex

Labeled line theory

- Channels when olfactory epithelium is open and information is present --> olfactory bulb --> olfactory cortex

Segregation never goes away

IMPORTANT PRINCIPLE: Topographic principle of information in the nervous system

- Information is mapped out where location of ORN predict function

- Different glomeruli have different odorant responses

odorant detection os topographically organized

Piriform cortex

(temporal lobe)

- Perception of olfaction is processes here

- higher level of perception sense of smell

- lose this, only basic responses to smell, not higher order memory characteristics

Brain damage

- Damage to the olfactory epithelium, olfactory bulbs, olfactory nerve can produce severe sensory loss (hyposmia or anosmia)

-Damage to "higher" structures, produces PERCEPTUAL ABNORMALITIES (dysosmia), including problems with discriminating between similar orders, recognizing complex orders, understanding order "quality"

Sensation vs. Perception

Sensation = "Mechanical nature": Detecting features of our environment (stimuli) - light sound waves, pressure - lower level process

Perception = "understand": interpreting or understanding the stimuli in the environment

Basic Principle of sensory neurons

Sensory neurons are designated to detect the presence (or absence) of an environmental stimulus, response to that stimulus with a change in membrane potential activity and then transmit that information to the CNS

Processing and perception

- (potentially many) sensory cells TRANSDUCE experience into neural code (transduction = presence/ absence of stimulus, neural code, shift in MVP)

- They relay that information onto the next neuron in the circuit. which relays it onto the next neuron ect.

- Processing typically starts in the sense organ and ends in the cerebral cortex, following a defined pathway

-Sensation --> perception

Rate code

- Within ONE CELL

- Rate of AP activity increases with increased stimuli, reflect the magnitude of stimulus, each line represents firing AP - summated into receptor potential and stimulus strength

*Once cell is responsible for sensory experience, focus on single level

Temporal code

- Within ONE CELL

- Fires more at larger hills

- Microstructure: temporal nature with changing rate

- Temporal nature = code

*Once cell is responsible for sensory experience, focus on single level

Chemical senses are a form of inter-cellular communication:

1. Endocrine function

2. Synaptic transmission (neurocrine function)

3. Autocrine function

4. Paracrine function

5. Pheromone function

6. Allomone function

Chemical sensation

Evolutionarily, one of the earliest senses was the ability to detect chemicals in the world around you

- Detection/assessment of food

- Detection of electrolytes

- Mate location

- Toxin/ poison avoidance

- Predator avoidance

Sensation and transduction

- The ability of an organism to detect environmental conditions (chemicals, light, sounds, etc.)

- Requires a sense organ containing neurons that are receptive to the stimulus

- Sensory neurons undertake transduction (process of converting sensory experience into a neural code that involves action potentials)

Transduction and representation in all 5 systems

- Each sensory neuron expresses receptor whose ligand is a specific chemical found in the environment (like a chemical nutrient of a pheromone from a mate)

- Binding of that chemical to the receptor changes the action potential activity of the sensory neuron= TRANSDUCTION

-Presence of the chemical in the environment, therefore, is represented in the nervous system by the change in firing of the sensory neuron

Transduction leaves to representation of ...

- Not just whether any stimulus is present/absent

- understand quality of stimuli (what chemicals are present [often many at once])

- Intensity ("strength" of stimulus, how salty/sweet)

- Duration of stimulus

Taste

- Tastants are the molecules that we can taste when introduced to our mouths

- Detection of chemicals, that mix w our saliva and change membrane potential in taste cells (NOT neurotransmitters)

- Modulate the activity of sensory cells on tongue that express receptors for tastings

- Only detectable if tasting is needed or needed to avoid

- We only detect tastants because they are of biological importance aid in avoidance of toxins

5 tastes = 5 receptors...

1. Sour

2. Salty

3. Sweet

4. Bitter

5. Umami

-Hot (spicy) and cold (minty)

-Water

Papillae

- Taste buds are within the taste pores within papillae (in grooves)

Papillae > taste buds> taste cells> receptors

Specific papillae are not specialized for specific tastants ...

Front = Fungiform papillae

middle = foliate papillae

back = circumvallate papillae

all have uniform detection, found on different parts of the tongue- different sized

Taste cells

-Each taste bud contains many taste cells

- Taste cells have receptors for tastants

- transduction: exhibit graded potential responses (EPSPs) to tastants

- Release neurotransmitter onto "dendrites" of neurons that relay information to brain steam

- Taste cells do NOT have threshold, so no Ads

Binding --> transduction (taste cell) --> change in membrane potential --> depolarization/EPSP no AP! --> release NT on nerve ending --> info propagated into CNS

Salty

- Na+ (or Ca++, Mg++, K+, mono cations) can move through channels in the taste cell membranes, causing depolarization of the taste cells

- These are graded potentials (no AP)

- Then release Its onto cranial nerve fibers

Transduction --> depolarization (EPSP) --> release NT --> info into CNS

Sour

- Acidic [high concentration of H+]

- H+ affect ion channels, including block K+ channels, preventing leak of the cation from taste cells (OR ELSE K+ leaves --> hyperpolarization)

- The result is depolarization (graded) and NT release onto nerve fibers

Why may neurons show an increased response?

1. Some other neuron excited them

2/ Some other neuron stops inhibiting them (disinhibition)

-Induction of excitation or release of inhibition often have similar effects in the nervous system

sweet

Most important biological system in body

- Sugars bind to G protein couples (metabotropic-like) receptors called T1R2 and T1R3 (t = taste, t1= carbohydrate)

- these receptors join together - dimerize (otherwise nonfunctional)

- Tasting binding to receptor --> activation of G protein --> activation of adenylate cyclase (ATP --> cAMP) which produces cAMP --> closure of K+ channels --> EPSP --> NT release

Sucrose and artificial flavoring: can trick and bind as ligand, "sweet" but cannot produce energy

Bitter

Second most important (to sweet)

- T2R (t2= bitter): G-protein couples metabotropic-like receptors [~30 members expressed in combinations to perceive the wide array of bitter flavors]

- Tasting binding to receptor --> activation of G protein --> activation of phospholipase C which produces IP3 --> efflux of Ca++ into cytoplasm --> EPSP --> NT release

More bitter receptors than sweet receptors- harmful chemicals (wide array)

Umami

"meaty"

- amino acid receptor (mostly activated by L-glutamate and monosodium glutamate)

- G-protein coupled metabotropic-like receptor; heterodimer of T1R1 and T1R3

- Tasting binding to receptor --> activation of G-protein --> activation of adenylate cyclase that produces ATP --> influx of Ca++ into cytoplasm --> EPSP --> NT release

Capsaicin

Tricks tongue into thinking environment is hot with spicy foods

Chemical in peppers

Acts as ligand to spicy receptor