Studied by 6 people
what is sensation?
the capacity to detect a particular physical or chemical stimulus
(involves the sensory organs and afferent nerves)
what is perception?
the conscious experience and interpretation of sensory information
(involves neurons in the central nervous system)
what is a stimulus?
a thing or event that evokes a specific functional reaction in an organ or tissue (stimuli can be physical or chemical)
what are some physical stimuli?
sound
visible light
heat
magnetic field
UV light
what are some chemical stimuli?
taste
odour
flavour
pheromone
what is stimulus transduction?
converting the stimulus into the nervous system ālanguageā i.e. neuronal activity
(each sensory organ deploys a specific mechanism to transform chemical or physical attributes of stimuli to neuronal activity)
which organ(s) and stimuli and related to somatosensation?
organ: skin and other tissues
stimuli: pressure, warmth, cold, pain
which organ(s) and stimulus and related to sight?
organ: eyes
stimulus: light
which organ(s) and stimulus and related to hearing?
organ: ears
stimulus: air vibration
which organ(s) and stimulus and related to smell?
organ: nose
stimulus: volatile chemicals
which organ(s) and stimulus and related to taste?
organ: mouth
stimulus: soluble chemicals
how do pigeons use magnetoreception?
they use the magnetic field of the earth to navigate and find the direction they want to go
what do elephants (and other animals) use infrasound?
infrasounds are sounds that humans canāt hear because the frequency is too low (they can also travel ling distances)
they use it to communicate with each other and about things that are happening
how do bats use ultrasounds?
ultrasounds are sounds humans canāt hear because the frequency is too high
they use it to navigate and localise everything that is around them including prey
how do fish (e.g. elephant fish) use electrolocation?
they can detect the electrical fields around them
if the electrical field is disrupted they know an object is there
they use electrical signals to communicate with each other
how does vision differ in humans and bees?
humans have cones that detect blue, green and red
bees have cones that can detect blue, green and ultraviolet
describe how asymmetric vision in the cockeyed squid works
the large eye looking upwards detects predators against the dim sunlight
the small eye looking downward detects preyās bioluminescent signals
what are sensory receptors?
cells that specialise in converting external stimuli (physical or chemical) into neural (electrical) activity
types:
photoreceptors
mechanoreceptors
chemoreceptors
nociceptors
what do photoreceptors do?
detect light (vision)
what do mechanoreceptors do?
detect movement (sound, texture, blood pressure, muscle stretch)
what do chemoreceptors do?
detect chemical compounds (smell. taste)
what do nociceptors do?
detect tissue damage (pain)
how do photoreceptors differ?
each photoreceptor points to a unique direction, sensing the light present in this two dimensional space
how do mechanoreceptors vary in the ear?
each inner hair cell responds to specific sound frequencies
how do odorant receptors differ?
each one detects only one chemical attribute
how are receptors distributed in sensory organs?
receptor distribution is not always homogenous (e.g. in the retina, tongue)
why does receptor sensitivity vary?
receptors have different thresholds (i.e. the minimum stimulus intensity that is detected)
what do neural relays do?
all senses connect to the cortex through a series of neural relays
sensory info is modified at each relay, allowing for the construction of different aspects of the sensory experience
they also allow for sensory systems to interact (e.g. visual modification of sound - the McGurk effect)
why is perception more complex than sensation?
the context, emotional state or memories can affect how we perceive the same sensory experience
why is the visual system important for our daily lives?
through seeing and perceiving the world around us we assess reality but can also produce adaptive behaviours
what is visible light?
the section of the electromagnetic spectrum that the human eye can detect
(light can enter the eye from a source of light, or after bouncing on an object)
anatomy of the human eye
what are the two types of photoreceptors contained in the retina?
cones (detect colour)
rods (detect light)
what type of photoreceptor is the fovea mainly covered in?
cones (actute vision during daylight)
what type of photoreceptor covers the periphery?
rods (which are more sensitive to light than cones)
how does light affect the release of glutamate in photoreceptors?
they are depolarised in the dark, releasing glutamate
light makes them hyperpolarise, reducing glutamate
what is a bipolar cell?
one of the main retinal interneurons and provide the main pathways from photoreceptors to ganglion cells
what affects the probability of neurotransmitter release?
photoreceptors and bipolar cells changing their membrane potential (they do not fire action potentials)
what are the two types of bipolar cells (in vertebrate retinas)?
on and off
how many photoreceptors doe bipolar cells connect to in the fovea and the peripheral retina?
fovea: one bipolar cell connects to one photoreceptor
peripheral retina: one bipolar cell connects with several photoreceptors
where is visual information from each side of the visual field analysed?
right side: left hemisphere
left side: right hemisphere
what are the three neural routes to the visual brain?
retinohypothalamic tract
geniculostriate pathway
tectopulvinar pathway
what is the retinohypothalamic tract involved in?
regulating the circadian rhythm
controls pupillary reflex that expands or contracts the pupil to regulate the amount of light reaching the retina
what is the geniculostriate pathway involved in?
the conscious experience of vision
contains:
dorsal stream: analyses how; guides movement to relative objects
ventral system: analyse the what: object identification
what is the tectopulvinar pathway involved in?
analyses spatial information of objects
from ganglion cells from retina periphery, with no colour info
explains the visual ability of patients with blindsight
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