PY2005 Biology

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What is sensation?
Sensory receptors detect stimulus energies and convert them into neural impulses sent to brain
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Perception?
Organises input and translates it into something meaningful. Requires sensation, not precise.
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What does each sensory system have?
Anatomical structure to collect, filter and amplify info
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Where do neural pathways terminate? Apart from what?
Thalamus, apart from olfactory system
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What is the thalamus?
Dense interconnections, allows multisensory integration
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Where does the thalamus send to?
Primary and secondary cortical areas
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What are receptor properties?
receptors respond to limited range of stimuli, different for species. They show adaptation.
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What is receptor adaptation?
Reduction in receptor responsiveness to stimulus over time
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Acuity?
How well we can discriminate between stimuli.
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What determines acuity?
No. and distribution of receptors. Increase receptor density, larger cortical representation
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Energy senses?
Vision (light), Audition (sound waves) and Somatosensation (temp, pressure). Receptors respond to energy, transform stimulus energy into neural impulses
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Chemical senses?
Olfaction and gustation. They respond to chemicals, receptors that transform chemical info to Neural impulses
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Neural pathways of audition?
Sound waves: ear canal where they are amplified make ear drum vibrate. Travel through middle ear, 3 bones vibrate, causes oval window to vibrate, then travel through fluid-filled cochlea
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Cochlea?
Vibrations cause basilar membrane to vibrate, stimulates hair cells (receptors), changes to NS
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Near the oval window, the BM is stiff. What frequency is best?
Higher
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Further down oval window, BM is less stiff. What frequency is best?
Low
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How are the sound receptors arranged?
Tonotopically, orderly correspondence between location of neuron and frequency tuning
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Auditory localisation?
Can localise sound in space
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Interaural time diff?
Sound will reach one ear before the other, unless parallel to head
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Interaural intensity diff?
From superior olivary nucleus each area both ear info, so can be compared from where sound is from. IID is so small, species have adaptations to amplify, owls, ears lower.
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Somatosensation
Perception of all mechanical stimuli that affect the body
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Nociceptors?
Pain
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Proprioception
Body's position
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Somatosensory receptors, neural signals go where?
Dorsal root of spinal cord, to motor neurons, to form reflex arcs. Others to medulla, NS to other side of body, to primary somatosensory cortex.
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Somatosensory processing?
Initial receiving is PSC, to sensory homunculus.
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High density of somatosensory receptors have?
Larger representation in S1
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What does S2 have?
More complex somatosensory representations, about object texture, size
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What is phantom limb?
Somatosensory representations can be changed. Ppt touched face, felt like amputated limb was being touched. Neighbouring representation of face expanded to appropriate cortical representation of limb.
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Olfaction
Odour molecules enter nasal cavity by nose or mouth
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Process of olfaction?
Trigger olfactory receptors, NS to glomeruli, single receptor can activate many glomeruli, NS travels via olfactory nerve to ipsilateral POC, then to Second OC, thalamus, hippocampus
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One nose, 2 odours?
1 always larger, means different smells. Larger, higher airflow, sensitive to odours with high absorption rate, smaller, low airflow, sensitive to low absorption rate
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Sniffing vs. Smelling
Smelling odour vs no. odour= secondary olfactory cortex. POC important at detecting change in odour, quickly habituates, SOC identifies odour.
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Gustation?
Surface of tongue, diff types of papillae. Taste cells
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Basic tastes?
Salty, sour, sweet, bitter, unami
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Follate papillae?
Sour and bitter
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Process of gustation?
Food molecules trigger gustatory receptors in taste cells, NS through Corda tympani nerve, to facial cranial nerve, then gustatory nucleus in rostral region, caudal region tells when food gone off, to solitary tract in NS
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From solitary tract to where?
Ventral posterior medial nucleus of thalamus to PGC
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Orbitofrontal cortex?
Important in producing pleasantness and reward value of food
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Vision
Enters through pupil, regulated by Iris, passes through lens, image inverted, project on retina, each eye diff angle
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Neural pathways of vision
Photoreceptors, info translated to NS, back to front of eyeball via bipolar neurons to ganglion cells, later to horizontal cells and amacrine cells
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Where do the ganglion cells send to?
Outside retina, form a bundle called optic nerve, blind spot is the releasing of this
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Rods and cones?
Mediate different types of vision.
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Cone?
Mediated vision, photopic vision, good lighting, provides acuity coloured perception, dominate in fovea
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Rod?
Scoptic vision, poor lighting, more sensitive, don't allow colour and acuity is lower
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3 types of cones?
Blue- short wavelengths, Green- medium, Red- long
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How does it work?
NS to optic chiasma via optic nerve, then crosses H, from contralateral VF to lateral geniculate nucleu via optic tracts
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How is info seperated?
In terms of eye and type of ganglion cell. Sent to V1 via optic radiation, then sent to higher order places in cortex
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LGN:
Info from both eyes, kept in separate layers
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Parvocellular layers?
Most input from fovea, sustained response to stimuli
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Magnocellular layers?
Entire retina, fast adaptive reaction
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What is the receptive field?
Visual neuron only responds when stimulus is presented in specific region of space. Orderly rel. between neighbouring cells receptive fields.
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PVC. V1?
Higher layers are 4 and 6, simple cells. Layers 2,3,5 complex cells, no distinct inhibitory or exhibitory regions. Respond to bars of certain orientation regardless of where in receptive field.
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Hypercolums?
All info needed on a small bit of space, PVC has a lot of these so has all the info needed
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Cortical visual areas:
Dorsal and ventral, receptive fields increase across visual system. Each cortical visual areas has own retinotopic map. Each VA specialised for certain type of info.
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V4: what is it specialised for?
Colour processing
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V5: specialised for?
Motion processing
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Illusions? How does activation in early sensory areas relate to our perceptual experience?
Situations where our perception differs from sensation. Colour flicker, slowly we can differentiate, fast we see a blend of colours
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Visual field defects:
Blindness in some areas of space, blindsight, cortically blind but still appear to have restricted vision
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Achromatopsia?
Inability to see colour, damage to V4
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Akinetopsia?
Inability to see motion, V5. Bilateral is severe.
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McGurk effect?
Input from one sense, vision, influencing perception of the input from another, audition. FA AND BA.
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How does the brain do this?
Combines input from multiple senses about a stimulus, weighs reliability of each sense, then makes estimate from this info, vision is usually most reliable.
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Mutlimodal perception?
Super colliculus: response from neurons is stronger when there is input from multiple senses. Cortical areas respond better.
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How does multisensory integration happen?
1 hyp: subcortically, multisensory info sent to cortex, or specific areas surrounded by MS areas, certain areas specialised
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Perceptual reorganisation? Is there reorganisation within a modality? E.g. if you are blind does VC get used for something else?
Sadato et al. 1998: braille reading, activated P and S VC in blind ppts. Suggests reorganisation of tactile processing in VA in blind ppl
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Can we see the same for normal people blindfolded for long times?
Yes, increase in activation in VC during tactile stimulation, but then went.
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Other cards in this set

Card 2

Front

Perception?

Back

Organises input and translates it into something meaningful. Requires sensation, not precise.

Card 3

Front

What does each sensory system have?

Back

Preview of the front of card 3

Card 4

Front

Where do neural pathways terminate? Apart from what?

Back

Preview of the front of card 4

Card 5

Front

What is the thalamus?

Back

Preview of the front of card 5
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