week 5 Flashcards
is perception concerned with the efferent of afferent branch of the nervous system?
afferent (periphery to CNS)
special senses (5)
vision
hearing
taste
smell
balance/equilibrium
law of specific nerve energies?
given sensory receptor is specific for each modality
T of F: modalities other than the adequate stimulus may activate receptors
true, but only at relatively high energy levels
what are the characteristics of sensory transduction? (3)
- triggered by sensory stimuli
- graded potentials (“receptor/generator” potentials) [if exceeds threshold, can generate AP]
- opening/closing of ion channels
describe the structure and function of sensory receptors
- sensory receptor responds to stimulus
- changes MP and opens Ca2+ channels, triggering release of neurotransmitters
- would eventually produce AP and carry msg to CNS
diff bw slowly and rapidly adapting receptors?
a) slowly adapting: receptor potential decays slowly during stimulus; always SOME receptor potential. interested in overall magnitude of stimulus.
b) rapidly adapting: receptor potential is elicited by change in stimulus energy. interested in stimulus velocity. decays quickly and nothing happens if stimulus is constant.
what are labelled lines?
specific neural pathways transmitting information of a specific modality
2 types of coding for stimulus intensity?
- frequency coding: frequency of APs
- population coding: # of receptors activated
examples of rapidly and slowly adapting mechanoreceptors?
rapidly adapting:
a) pacinian corpuscle (deep vibration/pressure)
b) meissner’s corpuscle (light touches)
c) hair follicle receptor
slowly adapting:
a) free nerve endings
b) merkel’s disk (superficial pressure)
c) ruffini’s ending (deep pressure)
whats a free nerve ending?
somatosensory receptor types that lacks identifiable specialized structures
warm vs cold receptors?
warm receptors:
- free nerve endings
- respond to temps in range of 30–43°C
- increased frequency with increase in temperature
cold receptors:
- possible free nerve endings
- respond to temps in range of 35–20°C
- increased frequency with decrease in temperature
classes of nociceptors? (3)
- mechanical
- thermal (respond to 44°C+)
- polymodal
a) what somesthetic sensations does the dorsal column–medial lemniscal pathway include?
b) how?
a) touch and pressure, proprioception
b) (1) proprioceptors/mechanoreceptors to spinal cord TO (2) medulla (crosses over) TO (3) thalamus to somatosensory cortex
a) what somesthetic sensations does the spinothalamic tract include?
b) how?
a) pain, temperature
b) (1) nociceptors/thermoreceptors TO (2) spinal cord (crosses midline) (3) thalamus to cortex
chemicals that activate nociceptors? (5)
Potassium
Histamine
Prostaglandins
Bradykinin
Serotonin
diff bw fast pain and slow pain? (3 each)
fast:
1. A-delta fibers (thin, lightly myelinated axons)
2. sharp/pricking
3. easily located
slow:
1. C fibers (thin, unmyelinated axons)
2. dull aching
3. poorly localized
gate-control theory of pain?
- somatic signals of non-painful sources can inhibit signals of pain.
- certain neurons inhibit the second-order neurons that transmit pain info.
- ex rubbing a painful area
describe anatomy of outermost eye (2)
- sclera (white part)
- cornea (transparent, allows light to enter)
describe anatomy of middle eye (3)
- ciliary body (helps focus)
- iris (colour part, in front of lens)
- choroid (beneath sclera and contains blood vessels that nourish inner layer of the eye/photoreceptors)
describe anatomy of innermost eye (1)
- retina (where photoreceptors are)
parts of retina (3)
- fovea: central region of retina, where light from center of visual field strikes (no blood vessels/high density of photoreceptors here)
- blood vessels
- optic disk: “blind spot” where blood vessels/axons enter and exit (no photoreceptors here)
what is accommodation?
lens curvature which enables the eye to focus on objects
is there more curvature of the lens when the object is near or distant?
near
describe the mechanisms of accommodation for viewing distant objects
- ciliary muscles relax
- zonular fibers become tight
- lens becomes larger
describe the mechanisms of accommodation for viewing near objects
- ciliary muscles contract
- zonular fibers become loose
- lens becomes smaller/rounder
what is emmetropia?
normal vision
what lens is needed to correct:
a) myopia
b) hyperopia
a) concave (decreases lens refractive power)
b) convex (increases lens refractive power)
what is:
a) presbyopia
b) cataract
c) glaucoma
d) astigmatism
a) hardening of lens (cannot become spherical)
b) cloudiness of lens
c) increased volume of aqueous humor, shifts position of lens
d) irregularities of lens or cornea, causes erratic bending of light waves
parasympathetic stimulation of circular muscle =
pupillary constriction
sympathetic stimulation of radial muscle =
pupillary dilation
describe the outer/middle/inner layers of the retina
outer: cones and rods
middle: bipolar, amacrine, horizontal cells
inner: ganglion cells
what is the retinal pigment epithelium?
contains melanin which makes it inky black and allows it to absorb light
main functions of rods vs cones
rods: used in dark conditions and found in peripheral (can pick up even 1 photon of light!)
cones: used in lit conditions and found in center (imp for colour vision)
in rods in the dark:
rod is __polarized, ___ing Ca2+ channels, triggering ___ ___, which acts on ___ cells.
de
open
neurotransmitter secretion
bipolar
what colours are S, M and L cones associated with?
S = blue
M = green
L = red
in terms of neural processing in the retina, which cell is first in the pathway to generate action potentials?
ganglion cells
what do the axons of ganglion cells form?
cranial nerve II, aka optic nerve
what is lateral inhibition?
allows transmission of strong signals in some neurons while suppressing transmission of weaker signals arising in nearby neurons
two types of lateral inhibition ganglion cells?
- on-center/off-surround
- off-center/on-surround
define the 3 types of ganglionic cells:
a) optic nerve
b) optic chiasm
c) optic tract
a) pre-cross
b) crossing point
c) post-cross
note: right visual field to left cortex, and vice versa
which sensory systems do NOT have receptive fields?
olfactory and auditory
describe anatomy of outer ear (3)
- pinna
- ear canal
function = to gather sound waves and conduct them to…
- tympanic membrane/ear drum (which separates outer and middle ear)
describe anatomy of middle ear (3)
[ossicles]
- malleus
- incus
- stapes
function = amplification of sound waves
describe anatomy of inner ear (2)
- oval window (separates middle and inner ear)
- cochlea (contains receptors for hearing and is fluid-filled)
amplitude: greater difference of ___ = louder sound. measured in ___
densities
dB
high frequency sounds = ___ ____. measured in ___
high pitched
Hz
describe what happens when cilia bends towards long vs short direction
LONG:
- K+ enters cell (causing depolarization)
- Ca+ channels open (resulting in release of more transmitter)
- frequency of AP increased
SHORT:
- K+ channels close (causing hyperpolarization)
- Ca+ channels close (resulting in less transmitter release)
- frequency of AP decreased
what do louder sounds cause the cilia to do?
bend farther in either direction
dB of normal speech? dB capable of causing hearing loss?
60 dB
100 dB (for only 14 mins!)
describe the neural pathways for sound (3)
- cochlear nerve enters brainstem (synapses with 2nd-order neuron)
- 2nd-order neuron to thalamus (synapse on 3rd-order neuron)
- 3rd-order neuron to auditory cortex
describe conductive vs sensorineural vs central deafness
conductive: inadequate conduction of sound waves through external and/or middle ear.
sensorineural: inadequate transduction of sound waves to electrical signals in inner ear
central: damage to neural pathway for sound
what do we mean when discussing the ear and equillibrium?
motion of head and its tilt relative to gravity
semicircular canals detect movement of head in 3D space. what are the 3 canals?
anterior (up/down)
lateral (side/side)
posterior (up/down/side)
which 2 structures detect linear acceleration?
utricle (forward/backward)
saccule (up/down)
we have more than 10k taste buds! where are they located?
tongue, roof of mouth, pharynx
how many taste receptor cells per bud?
50-150
what do taste receptor cells respond to?
tastants
___ triggers the release of a transmitter that communicates with taste afferents. 2 examples of such transmitters include…
calcium
ATP, serotonin
what makes us perceive sour, salty, sweet, bitter, and umami tastes?
- sour = hydrogen ions
- salty = sodium ions
- sweet = resemble sucrose
- bitter = wide variety of nitrogen-containing compounds
- umami = amino acids “flavour enhancers”
what cells make up the olfactory epithelium?
- sustentacular cells provide structure support + maintain extracellular environment.
- basal cells are precursor cells for development of new receptor cells.
- olfactory receptor cells (neurons) responding to olfactory stimuli
T or F: olfactory info ends up in thalamus.
false! goes straight to amygdala and hippocampus
purpose of cilia in olfactory epithelium?
projects into mucus; bind odorant molecule; binding proteins transport to receptors
T or F: olfactory receptor cells are the only neurons in the body currently known to be replaced regularly
true!
describe process of olfactory signal transduction (4)
chem binds to receptor…
- activates G protein called G(olf)
- activates adenylate cyclase… then cAMP
- cAMP opens cation channels
- Na+ and Ca2+ enter cell = depolarization
what does specificity of binding mean for olfactory system?
specific olfactory receptor cells exist for each type of odorant-binding protein
