6 - 1 © 2000 pearson education canada inc.,toronto, ontario sensation lectures # 6 & 7 biology...
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Sensation 6 - 1 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Lectures # 6 & 7Biology of Behaviour Sensory I
Sensation 6 - 2 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Control of Internal Functions and Automatic
Behaviour
The Brain Stem: controls automatic behaviours (breathing, blood pressure etc)
The Cerebellum: coordinates and learns movement
Structures within the Cerebral Hemispheres: involved in cognition, sensations and reactions to them
Sensation 6 - 3 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
The Brain Stem and Cerebellum
F 4.30
Sensation 6 - 4 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Glandular Structures involved in behaviour
F 4.31
Sensation 6 - 5 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Sensation
1. Vision2. Audition3. Gustation4. Oflaction5. The Somatosenses
Sensation 6 - 6 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Basic Principles of Sensory information Processing•A signal (light, odour, movement etc) from the environment is transformed by a sensory organ into action potential.
•Usually a graded stimulus is encoded by the brain…. varying the number and frequency of action potentials (APs).
•The APs travel in anatomically distinct nerve pathways that define the nature of the sensation
Most sensory information (APs) is relayed through a large brain area called the thalamus which is then passed on to the appropriate area in the cerebral cortex
Sensation 6 - 7 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Principles of sensory information: Basics of signal transduction spinal
cordF 4.13
Sensory information relayed by the spinal cord travels discreet anatomically defined nerve tracks (columns) that are specific the type of information (pain, touch position sense) The APs traverse the spinal cord and travel in the opposite side from which the information was received
Once in the brain the signals arrive in anatomically discreet regions of the thalamus
The thalamus then relays the information to anatomically discreet regions of the cortex
Sensation 6 - 8 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Organization of the Cerebral CortexF 4.24
Sensation 6 - 9 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Structures within the HemispheresF 4.33
Sensation 6 - 10 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Sensory Processing
Transduction
Psychophysics
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TransductionLocation of Sense Organ
Environmental Stimuli
Energy Transduced
Eye Light Radiant Energy
Ear Sound Mechanical Energy
Vestibular System Tilt and Rotation Mechanical Energy
Tongue Taste Recognition of Molecular Shape
Nose Odour Recognition of Molecular Shape
Skin, Internal Organs
Touch Mechanical Energy
Temperature Thermal Energy
Vibration Mechanical Energy
Pain Chemical Reaction
Stretch Mechanical Energy
T 6.1
Sensation 6 - 12 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Vision
Light The Eye and Its Functions Transduction of Light Eye Movements Colour Vision
Sensation 6 - 13 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Basic Wave Physics (What is light?) F 6.6
Waves come in many sizes and frequencies but all are rhythmic fluctuations electromagnetism
They travel at the speed of “light” which is 298,000 km/sec
This is constant so if the frequency is 88.5 MHz (Mega = 1,000,000)
Then the wavelength is: 298,000,000(metres/sec)
88,500,000 (cycles /sec)
= 3.38 metres/cycle
These are radio waves what happens as the wavelength shortens?
Sensation 6 - 14 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Light
F 6.7
1 nanometre = 1 billionth a metre (10-9metres)
So visible light has a wavelength of about 400 nm (violet) to 750 nm (red)
So how do our eyes work to see this electromagnetic radiation?
Sensation 6 - 15 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
The Eye and Its FunctionsF 6.8cornea: transparent
tissue that covers the front of the eye
iris: a formation of muscle that forms a circle with a hole in middle ; it controls the amount of light that enters the lens
lens: is transparent flexible tissue that focussed the light entering the on retina
retina: layer of tissue at the back of the eyeball that contains specialized cells that can sense the light
Sensation 6 - 16 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
The Eye and Its Functions
F 6.12
Organisation of the retina
There are many different types of cells (all basically neurones) that make up the retina
Photoreceptors: convert light into chemical energy that releases neurotransmitter onto bipolar cell.
Bipolar cell fire action potentials to release neurotransmitter that excite ganglion cell.
Ganglion cells axons make-up the optic tract that then make synapsesin the thalamus.
Sensation 6 - 17 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Basic Light Sensory Physiology
Light is transformed into chemical energy by receptors (analogous to neurotransmitter receptors) on two types of cells either a cone (colour vision) or a rod (high sensitivity but colour blind)
The bipolar cells are excited by the reduction in inhibitory neurotransmitter than is constantly being released.
The bipolar cells then release excitatory neurotransmitter and the ganglion cell is excited
Sensation 6 - 18 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Transduction of Light by Photoreceptors
F 6.13
Sensation 6 - 19 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Colour Vision
F 6.16
White light is can be divided into a full spectrum of colour
Our eyes detect different wavelengths and then combine this colour in our brains in order to complete our perception our surroundings
There are three different kinds of cones: red green and yellow
This means that each cone is maximally stumulated when light of certain wavelength strikes it.
Sensation 6 - 20 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Colour Vision
F 6.17
But colour vision is not like mixing paint Mixing red, green and yellow light makes a perception of white
While mixing the same colours of paint results in a dull grey or black pigment
Sensation 6 - 21 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Colour VisionF 6.18
Three kinds of responses
Two kinds of wiring
Cells that are excited by red light but inhibited by green light (and vice versa)
Cells that are excited by yellowlight but inhibited by blue light
pure red wave length pure green wavelength
Yellow stimulates both red and green cones
Sensation 6 - 22 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Colour Vision
F 6.15
Rods
become
more
important
Cones become more important
Sensation 6 - 23 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Audition
Sound
The Ear and its Functions
Detection and Localizing Sounds
Sensation 6 - 24 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Sound
F 6.21
Sounds waves are not electromagnetic phenomena but are alterations in air pressure
Nevertheless these alterations in air pressure deform the ear drum so as to mechanically stimulate actions potentials in the auditory system
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The Ear and Its Functions
F 6.23
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The Ear and Its FunctionsF 6.24
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The Ear and Its Functions
F 6.25
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Detecting and Localizing Sounds
F 6.27
Sound is less loud because air pressure changes have been blunted by head therefore we learn that direction of sound is on the same side of head where it is louder
Sensation 6 - 30 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Detecting and Localizing Sounds
F 6.28
Sound in front synaptic delay equals zero
Synaptic activation has delay that is equal to the time that it takes for sound to travel from one side of head to other this is relatively short about about 1 ms or 2 ms
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Gustation
Receptors and the Sensory Pathway
The Four Qualities of Taste
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The Four Qualities of TasteF 6.30
Sensation 6 - 33 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Receptors and the Sensory Pathway
F 6.29
Sensation 6 - 34 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Olfaction
Anatomy of the Olfactory System
Sensation 6 - 35 © 2000 Pearson Education Canada Inc.,Toronto, Ontario
Anatomy of the Olfactory System
F 6.31
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Combining gustation and olfaction gives us our sense of “taste”
Odours or flavour results from combining the activation of hundred of receptors in the olfactory tract but….
Sour sweet, bitter and salty comes from just four different receptors on the tounge
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The Somatosenses
The Skin Senses
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Compartmentalisation of Function
F 4.28
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Representation of the sensations in the cortex are not anatomically proportional
Our faces and hand make by far the most connection to the cortex while other larger areas (trunk) have only a relatively small representation