BIO 448 Final

Three examples of types of sensilla

Trichoid: hair like
Basiconic: peg like
Coeloconic: recessed peg like

Study: how does a nanotool mimic a moth antenna?

A new oily coating, which improves the functionality of the nanopores.

Once pheromones go through the pore, these molecules will grab them and bring them through as to prevent clogging at the pore

What is neuropil?

General term for an area devoid of cell bodies, just have fibres close together to allow for quick communication

Ways to study processing: Electroantennogram

Antenna responds to pheromone with an immediate electrical signal, which is amplified and displayed on an oscilloscope.

Doesn't give information about OSN or sensilla group, but overall response to pheromone

Ways to study processing: extracellular recording

Electrical change in the membrane and a nerve impulse that can be recorded from a microelectrode inserted into the base of the hair

What is a Macro Glomerular Complex (MGC)?

An MGC is a glomerus that responds to particularly important stimuli, and this importance is elaborated centrally.

What is the important function of the MGC in overall processing?

Increase redundancy, increase sensitivity

What is the mushroom body role in the processing pathway?

Axonal projections extend from the antennal love to higher processing centers, such as the calyces of the mushroom bodies

Where does the vomeronasal organ project to?

accessory olfactory bulb

Anterior AOB pathway?

Excitation in the AOB spreads in the anterior-posterior direction throughout the anterior AOB but does not cross into the posterior division.

Posterior AOB pathway?

Excitation in the posterior AOB appears as an oscillatory wave that does not cross into the anterior division of the AOB

What is the difference between the odourant and pheromone pathways?

- PBP vs OBP
- MOE -> MOB -> OT -> lateral amygdala (odourant)
- VNO -> AOB -> medial amygdala (pheromone)

Role of vasopressin in social order processing?

• There is evidence that vasopressin is important in brain areas where olfactory information is processed. (main and accessory olfactory bulbs, anterior olfactory nucleus)

• facilitates odor based cues

Projection neurons:

Travel from glomeruli to mushroom bodies & lateral horn
Uniglomerular or multi (if uni, active only when 1 OR type is active)
Uses ACh (& maybe histamine)

Local interneurons:

Within glomeruli
Bipolar
Mostly INH (GABA), although the input from OSNs is EXC
Projects to other OSNs (lateral INH)

Lateral INH:

Increases stimulus:noise
Increases specificity & contrast
Sharpening & huge refinement

Calyx:

Part of MB
Distinct layers that are differentiated by diff. specific sensory modalities (ex. mechano)
Contains dendrites of KCs

Kenyon cells:

Part of MB
Project to alpha, beta, gamma lobes
Axons form peduncle
Dendrites in calyx
Uses DA

Lateral horn:

Also called "dorsolateral protocerebrum"
Mostly pheromones
Coarse discrimination
Innate, acute behaviour
Non-glomerular neuropil that surround glomerular neuropil (ex. MB)

Convergence VS. Divergence VS. Lateral INH:

Convergence increases sensitivity
Divergence increases redundancy (parallel processing)
Lateral increases specificity

ORNs converge/diverge/lateral onto glomeruli of AL

Converge

PNs converge/diverge/lateral onto MB

Diverge

PNs converge/diverge/lateral onto K cells

Converge (coincidence detection)

Co-convergence:

2 kinds of receptor neurons converging on a single glomerulus
Super rare

Co-expression:

2 diff. receptors on same neuron converging onto glomerulus

G-protein cascade: (6)

1. Once odourant is bound, g-protein is activated
2. Adenylate cyclase is activated
3. ATP --> cAMP
4. cAMP opens cycle nucleotide-gated cation channels
5. Influx of Na+ & Ca2+
6. If enough channels are active, OSN responds

OSN (periphery) responses:

Frequency of APs increases as dosage increases
Odour/rate code

Rate code:

Stimulus is coded in the firing rate, not the timing
Odours that are closest to preferred odour for that particular neuron will increase Hz of firing
Amp. never changes w/in neuron (remember: AP), although amp. may differ between diff. cells

Antennal lobe (central) responses:

Temporal coding

Specialized metabotropic:

OR22A

Generalized metabotropic:

OR83B

Slow & prolonged cascade: (4)

1. Odourant binds to OR22A
2. G-protein cascade (alpha-3 subunit)
3. Influx of cations via TVVGYLG motif of OR83B
4. Depolarization

Fast & short cascade: (4)

1. Odourant binds to OR22A
2. Opens OR83B (ionotropic)
3. Cation influx
4. Depolarization

Conditioned stimuli:

Odours associated either with danger or food
Odours represented in MB by K cells
Simultaneous arrival of CS & US strengthens synapses from K cells to output neurons

Conditioned stimuli cascade: (6)

1. Coincidence detection @ K cells (CS & US arrive)
2. Rut-AC increases cAMP (if lots of Ca2+ around)
3. PKA activated
4. PKA phosphorylates proteins @ synapse
5. PKA phosphorylates K+ channels to prolong AP
6. Extinction via some antagonist

zones in epithelium

4

Zones of epithelium:

• Defined by expression of receptors

• OSNs in given epithelium zone will project to corresponding zone in olfactory bulb glomeruli (peripheral & central map)

• OSN axons expressing the same OR converge onto 1-2 glomeruli

• 1 OR type/OSN

Main olfactory bulb:

Analogous to antennal lobe
Mitral cells tuned to diff. chemical structures

Coincidence detection in OC:

• 2+ PNs synapse into 1 cortical neuron (convergence)

• AP firings for PNs are synchronized

• Temporal summation gives rise to discharge @ cortical neuron

Salamander:

• 2 molecular maps in MOB (AT28 & AT1)

• OSNs distributed across olfactory epithelium

• When animal inhales, activity depends on where neurons are placed

• Temporal sequence of events based off of zones (ie. also uses spatial)

• Ex. If OSN A region is more anterior than OSN B, OSN A --> PNA will be active before OSN B --> PNB

Salamander: periphery VS. central

Peripheral: increasing dose of stimulus = increase rate of firing
Central: complex changes in temporal firing patterns with simply increase of concentration

Vomeronasal organ:

• Many blood vessels; pumping action (dilating & constricting) makes lumen change size

• This allows for the movement of air across entire epithelium

Nautilus vs Octopus

Nautilus

• scavenger

• shell

• ancestral

• no suckers

• gas filled chambers for buoyancy

• countershading (hard for predators below to distinguish = light ventral)

Octopus

• predator / carnivorus

• no shell

• camoflague

How do nautilus detect prey?

tentacles

How do nautilus move?

jet propulsion

How do nautilus conceal themselves?

dark on top, light on the bottom, countershading

What can the nautilus eye be compared too?

pinhole camera

Why can it be compared to a pinhole camera?

- balance of resolution and brightness, tend to be a lot dimmer but with a sharper image
- there is an obstacle between the object and the screen

What are chromoatophores?

They are under nervous control
pigments: black, brown, red, orange or yellow

What are the three types of reflecting cells and what is there main role?

Reflector cells: reflect mainly blue and green
Iridophores: reflect mainly pinks, yellows, greens, blue or silver
Leucophores: responsible for white spots

How are pigments controlled?

Muscles are in control, pigment sacs will be stretched out, which will distribute the pigment

What are two examples of defense mechanisms of cephalopods?

- Ink jet, disorients any predator that is following
- Photophores are bioluminescent

Octopus defense:

Does not have shell, so needs good memory for hiding spots
Last resort is ink
Disorients visually & may have toxins
Maybe bioluminescence (photophores) for distraction

closed circulatory system:

1 systemic heart (deoxy)
2 brachial hearts (oxy)

Cuttlefish:

internalized shell (cuddle bone

lateral lines

Lateral lines:

Respond to pressure waves
Contain hair cells

____ ganglion controls chromatophores

stellate

Mimic octopus:

Changes colour, shape & behaviour
Flounder fish, lion fish, sea snake

Vampire squid:

Defensive "pumpkin posture" (exposes hooks)
Only cephalopod that can see colour (3 photopigments)
Live in VERY deep water

Intelligence of octopus:

Brain VS body weight: between fish/reptiles & birds/mammals
Need good memory to compensate for lack of protection
Problem solving ability (tool use ex. coconut shell)
Lifespan is no more than 3 years (bad)
Observational learning (ex. opening jar)
Hunting skills are partly genetic, partly self-taught
Only invert. known to play

Chemosensation on suckers:

Can tell fitness of male (~MHC)

Nautilus eye:

Pinhole opening
Sea water enters hole
Increasing the size of the hole would decrease dimness but increase bluriness
Cilia & mucus to keep away pathogens & irritants

Star-nosed mole:

Eats insects
Lives underground (likes damp)
Digs tunnels
Swims (can smell in water)
Fastest animal in terms of time difference between detecting something & determining if it's edible (need to be fast b/c of competition)
22 tentacles on nose that can move independently

Eimer's organs:

Found in SN-mole & coast mole
Organs are domed epidermal sensory structures containing Merkel cells, encapsulated corpuscles (similar to Pacinian, but smaller) & circle of free nerve endings
Not found in moles that live in a dry habitat
Depression in the centre
Also nociceptors (new research)

Merkel cells

are critical for relaying light touch, textures, and shapes to the brain

Shrews use ____ instead of EO

Vibrissae (hair cells)

Eastern mole:

Has some of the same sensory cells found in E organ, but does not have dome/central column

Primary sensory cells:

Cell body @ surface
Receives stimulus
Transmits info to a neuron via a fibre
Ex. OSN

Secondary sensory cells:

Cell body @ surface
Transmits info to dendrites of a nerve cell

NO AP generated

sensory nerve cells

sends dendrites to surface

von Frey hair

• measure pressure it takes to bend hair

• calibrated hair series

• apply to different parts of the hand

• determines thresholds and distributions of touch points

• also mechanoreceptor fields

MILD

M = modality (vision touch chemosensory)

• differences: quality (i.e pressure)

I = intensity (strength)

• firing rates of receptors

• duration of stimulus

L = location

• spatial distribution of activated receptors

D = duration

• time duration of APs

Pacinian vs Merkel

Pacinian

• fires when stimulus is applied and when its taken away

• will not fire under a constant stimulus

Merkel

• fires during the whole duration

Receptive field

• area on the skin where a stimulus is applied and the receptor still responds

• merkel = small field

→ can represent smaller patterns clearer (i.e. braille)

• pacinian = large field

Adaptation Rate

merkel = slow adapting

pacinian = fast adapting

pacinian corpuscles

• high vibrations, deep sudden pressure

Generator Potential steps

applied pressure → deformation of capsule → stretching of membrane of non-myelinated portion of sensory neuron → opening of Na channels → influx of Na → change in membrane potential → generator potential

Generator Potential 2

increases w increasing stimulus

continues stimulus application → amplitude of generator [potential decreases

if generator potential exceeds threshold → AP

vibration receptors

if accessory layers are removed depolarization persists during most of the stimulus

pressure applied - pacinian corpuscle

• deformation of nerve ending

• generator potential

• AP

continued pressure - pacinian corpuscle

• no AP

• no GP

• no nerve ending deformation

pressure removed - pacinian corpuscle

• deformation of nerve ending

• generator potential

• AP

Eimers Organ (EO)

domed epithelial sensory organ containing a central cell column, merkel cells, encapsulated corpuscles and two circles of free nerve endings, one associated with the ccc (texture) and one peripheral circle (nociception)

how does the star-nosed mole determine texture?

• by comparing neighbouring EO’s with different free nerve ending activity patterns (rough) or same free nerve ending activity (smooth)

• differentiated by central column patterns being deflected in the same direction (smooth) or opposite directions (rough)

displacement component

air molecules displaced in same direction as membrane’s movement

pressure component

molecular compression and spreading

sound pressure level (SPL)

• comparison of amplitude of sound to threshold sound of human hearing

• decibel

how to represent molecular movements comprising a sound on a graph?

smooth sinusoidal graph

period

• time required to go through one complete cycle

• 1/f

frequency

cycles/s or hertz (Hz)

wavelength

speed of sound in a given medium (m/s) / frequency (s-1)

the grater the frequency of membrane movements the greater the frequency of ______

sound pressure fluctuations

increasing membrane movement increases

the amplitude of pressure fluctuations

spherical spreading

• sound pressure must cover ever increasing area of space

• Because the intensity decreases with the square of the distance, doubling your distance from the source reduces the intensity to one-quarter (1/4) of its original power

• Because of the logarithmic nature of decibels, every time you double the distance from the sound source, the sound level drops by exactly 6 dB

atmospheric attenuation

absorption of sound by air greatest for sounds of high frequency ( > 10 or 20 Hz)

absorption or reflection

by solid objects found in the sound path; amount of reflection depends on size of object compared to wavelength

Cabbage moth and caterpillar form

• female wasp lays eggs on caterpillar to feed on it when they hatch

• caterpillars can detect wasp approaching closer than ~2m from their sensory hairs and escape

• wasp flies with wing beat frequency of 150 Hz

• displacement component

elements of a cricket song

• each syllable is a pulse (one complete wing close)

• interval between pulses determines pulse rate

• a chirp is composed of many pulses

what produces cricket song?

• protrusions called files on the underside of wings

• scraper will ratchet along all teeth in the file

female cricket ears

highly specialized receivers especially tuned to detect the direction of sound specifically at the carrier frequency of the males calling song