Behavioral Neuroscience test 2

Transduction

conversion of one signal to another

somatasensory system transducts

mechanical stimulation of skin

injury to skin

changes in temperature

mechanosensation

touch, pressure, vibration

nociception

pain, temperature

epidermis

free nerve endings

dermis

merkels disc, hair folllicles, meissner’s corpuscle

merkel’s disc

fine touch, like very small bumps, sharp corners, (reading braille)

hair follicles

touch, receptor is around root of hair

hypodermis

parinian corpuscle, ruffini’s ending

parininian corpuscle

vibrations, higher pressure

Ruffini’s ending

stretch of skin when its being pulled, grabbed, pinched

transduction pathway for parinian corpuscle

1. mechanical stimulus stretches corpuscle membrane

2. opens up sodium channels letting Na+ in, causing it to depolarize,

3. threshold potenial reached, causing a receptor potential to form

how to distinguish between stimuli

number of receptors activated, number of action potentials, pattern of action potentials

adaption

progressive loss of response to stimuli, allows detection of change

pacinian corpuscle speed

fast adapting

meissnerrs corpuscle speed

fast adapting

merkels disc speed

slow adapting

ruffinis ending speed

slow adapting

receptive fields

area where a stimulus will alter a single neuron activity

somatosensory pathway to the brain (PNS stimuli)

goes to spinal cord, brain stem, crosses over to other side of medulla, thalamus, primary somatosensory cortex

somatosensory pathway to the brain (CNS stimuli)

cranial nerves, pons, medulla, spinal cord, than back up

plasticity

receptive fields are plastic

pain

generated when the skin tissue is damage

damaged cells

release substances that activate nerve free endings

pain signals

serotonin, K+, prostaglandin, leukatrienes

pain meds

inhibit synthesis of prostaglandines

c fibers

are unmeliynated, there are cold and warm c fibers

a fibers

are myelinated

inflammation

action potentials can also excite blood vessels and other cells to cause this

dorsal root signals

axon hillock away from cell body, signal bypasses cell body in dorsal root ganglia

spinothalamic tract (nociception pathway)

once it reaches spinal cord, results in synapse, axon splits into 2; one sends motor signal back out, other signal switches sides of spinal cord and sends signal up

neuropathic/chronic pain

may be due to inappropriate signaling of pain by neurons, microglia at injury site release chemicals, dorsal horn at neuron can become hyper excitable, 

amplitude

sound pressure, loudness

Frequency

Hertz(Hz) pitch, 20-20,000 hz range for humans

pinna

funnels soundwaves into ear canal, enhances certain frequencies

canal

soundwaves propogate down to the ear drum

tymphanic, ear drum

vibrations cause 3 ossicles to move, amplifies pressure

3 ossicles

(malleus, incus, and stapes)

tensor tympani, stapedius

controlls contact between ossicles, protects from loud sounds and mute self made sounds

stapes

contacts oval window, transfer vibrations to 3 fluid filled canals in cochlea

cochlea

small and coiled,  A fluid-filled, coiled structure where transduction occurs

basilar membrane

Runs the length of the cochlea, vibrates different areas sensitive to specific frequencies,

• high frequencies at narrow, stiff bases

• low frequencies, at wide floppy apex to tip

tectorial

between vestibular and middle canals

organ of corti

inside of cochlea, The sensory organ sitting on the basilar membrane

• contains inner and outer hair cells

IHC (inner hair cells)

detect sound, The primary sensory receptors. Bending of their stereocilia opens ion channels (K⁺, Ca²⁺), leading to depolarization and neurotransmitter release onto the auditory nerve (Cranial Nerve VIII)

OHC (outer hair cells)

helps discriminate between similar frequencies, Act as cochlear amplifiers; they contract and elongate to sharpen the frequency tuning of the basilar membrane

hair cells (auditory)

transduce sound waves into electrical activity

each hair cell has 50-200 stereocilla (hair cell)

relay electrical information to auditory nerve fibers

hair cell transduction (auditory)

• vibration and stereocilla

• tip links open ion channels

• Ca 2+, K+ depolarize IHC

• release neurotransmitters onto auditory nerve (mainly glutamate)

tonotropic map of frequency

hearing version of homunculus, lowest threshold on tuning curve is frequency auditory neuron responds best to

pathway to brain from hair cells (auditory)

Cochlea → Vestibulocochlear Nerve (VIII) → Cochlear Nucleus (brainstem) → Superior Olivary Nucleus (sound localization) → Inferior Colliculus (midbrain) → Medial Geniculate Nucleus (Thalamus) → Auditory Cortex (temporal lobe)

• The tonotopic map is maintained at all levels

• vestibulocochlear nerve (8th)

synapses onto cochlear nuclei in brainstem

superior olivary nuclei

info travels to both olivary nuclei, to midbrain,

inferior colliculus

primary auditory centers of midbrain, gets info from both olivary nuclei for sound localization

thalamus (vocalization role)

auditory cortex identifies complex sounds that have many subparts

olfaction

smell, humans can dsicriminate over 1 trillion oderants, any 2 people can differ in odor receptors by 30%, rodents olfactory bulbs are larger than humans

olfactory epithelium

olfactory receptor neurons, supporting cells, basal cells

adult neurogenesis

olfactory neurons regenerated from basal cells

Olfactory neurons have

Cilia extending from the dendritic
knob into the olfactory mucosa
→ Unmyelinated axon to olfactory bulb
→ Metabotropic receptors on cilia and knob

olfactory receptor types

each receptor belongs to one of four types of subfamilies

how many different types of olfactory receptors do humans have

400

olfactory transduction

• odorant binds metabotropic receptor

• g-protein activated

• adenylyl cyclase activated and makes cAMP (2nd messenger)

• camp causes Ca2+, Na+, channels to open

• voltage gated Cl- channels open to further depolarize cell

• action potential in axon

glomeruli

cluster of mitral cells

mitral cells

• Olfactory neuron axons synapse on these in the olfactory bulb,

receives input from olfactory
neurons with same receptor type
→ separated by function in olfactory bulb

Olfactory pathway

 Olfactory Receptor Neurons → Olfactory Bulb → Piriform Cortex (Primary Olfactory Cortex). This pathway bypasses the thalamus!

5 Tastants

5 Receptors (salty, sour, sweet, bitter,
umami)

Taste receptor cells

(50-150) are clustered into taste buds

taste bud location

located on sides of taste pores between papillae (bumps)

papillae

bumps that taste buds are on the side of, are not specified for taste, have all five tastants in different ratios on each bud

Circumvallate papillae

located in the back

Foliate papillae

located along the sides

Fungiform papillae

located in the front of the
tongue

TASTE CELLS

replaced every 10-14 days

taste cell transduction

Receptors on cilia are bound by tastants
→ Receptor activation produces receptor
potentials
→ Receptor potential directly causes
neurotransmitter release onto cranial nerves
→ Thalamus, then cortex

gustatory map

homunculus for taste

salty taste

Na+ ions flow through open ion channels
in the taste cell membrane, causing
depolarization

SOUR

We perceive acidic solutions as sour
→ Acid = high concentration of H+
▪ Acid-gated K+ ion channels are blocked,
preventing K+ leaving the cell and leading
to depolarization

SWEET

Sugars bind to T1R2 and T1R3 receptors, causing them to join (dimerize)
▪ Tastant binding to receptor → activation of G-
protein → second messengers → Ca+2 flow into
cell → receptor potential → neurotransmitter
release

umami

• Amino acid receptor (mostly activated by L-
  glutamate and monosodium glutamate)
  ▪ G-protein coupled metabotropic-like receptor;
  heterodimer of T1R1 and T1R3
  ▪ Tastant binding to receptor → activation of G-
  protein → second messengers → Ca+2 flow into
  cell → receptor potential → neurotransmitter release

BITTER

▪ T2R receptors: G-protein coupled metabotropic-
like receptors
→ 30 types, so can perceive many bitter flavors
▪ Tastant binding to receptor → activation of G-
protein → second messengers → Ca+2 flow into
cell → receptor potential → neurotransmitter
release

human vision vs dog vision

dogs cant see red

human vs snake vision

difference in infrared spectrum

human vs. bird vision

difference in ultraviolet range for vision

human vs. mantis shrimp

humans can detect 3 colors, mantis see 12

PHYSICS OF LIGHT

a prism will seperate light into colors on the spectrum. a rainbow is water vapor breaking apart wavelengths. each color of the rainbow accounts for different wavelengths of the electromagnetic spectrum

photons

packets of energy which are both particles and waves

brightness

Number of photons emitted by source

color

Frequency of photon waves

Cornea

refracts light entering the eye to retina

retina

light transferred here, inverted top-bottom and reversed left-right

Pupil

(opening in the iris) controls how much
light enters
→ brightness
→ optometrist dilates pupil by blocking
acetylcholine transmission in iris muscles

Lens

focuses image on retina by changing
shape

Ciliary muscles

Accommodation = focus by changing shape of lens

Photoreceptor cells

rods and cones in retina

rods

scotopic, Very high sensitivity
→ respond in low light conditions,
and saturated in bright light,light, 1 photoreceptor, 100 million, More common in peripheral parts of retina, Wavelength insensitive (gray)

cones

Low sensitivity → only active under brighter condition,s3 photoreceptors, 4 million, More common in fovea (center of the retina), Wavelength sensitive (colors)

Fovea

center of retina (more cones)

number of cervical receptive fields

8

number of thoracic receptive fields

12

number of lumbar receptive fields

5

number of sacral receptive fields

5