6 - 1 © 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Lectures # 6 & 7 Biology of Behaviour Sensory I

6 - 2 © 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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

6 - 3 © 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation The Brain Stem and Cerebellum F 4.30

6 - 4 © 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Glandular Structures involved in behaviour F 4.31

6 - 5 © 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 1.Vision 2.Audition 3.Gustation 4.Oflaction 5.The Somatosenses

6 - 6 © 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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

6 - 7 © 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Principles of sensory information: Basics of signal transduction spinal cord F 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

6 - 8 © 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Organization of the Cerebral Cortex F 4.24

6 - 9 © 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Structures within the Hemispheres F 4.33

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Sensory Processing  Transduction  Psychophysics

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Transduction Location of Sense Organ Environmental Stimuli Energy Transduced EyeLightRadiant Energy EarSoundMechanical Energy Vestibular SystemTilt and RotationMechanical Energy TongueTasteRecognition of Molecular Shape NoseOdourRecognition of Molecular Shape Skin, Internal Organs TouchMechanical Energy TemperatureThermal Energy VibrationMechanical Energy PainChemical Reaction StretchMechanical Energy T 6.1

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Vision  Light  The Eye and Its Functions  Transduction of Light  Eye Movements  Colour Vision

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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?

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Light F nanometre = 1 billionth a metre (10 -9 metres) 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?

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation The Eye and Its Functions F 6.8 cornea: 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

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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 synapses in the thalamus.

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Transduction of Light by Photoreceptors F 6.13

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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.

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Colour Vision F 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

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Colour Vision F 6.15 Rods become more important Cones become more important

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Audition  Sound  The Ear and its Functions  Detection and Localizing Sounds

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Sound F 6.22

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation The Ear and Its Functions F 6.23

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation The Ear and Its Functions F 6.24

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation The Ear and Its Functions F 6.25

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Gustation  Receptors and the Sensory Pathway  The Four Qualities of Taste

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation The Four Qualities of Taste F 6.30

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Receptors and the Sensory Pathway F 6.29

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Olfaction  Anatomy of the Olfactory System

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Anatomy of the Olfactory System F 6.31

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation The Somatosenses  The Skin Senses

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Compartmentalisation of Function F 4.28

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation The Skin Senses F 6.32

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation The Skin Senses F 6.33

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation 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

© 2000 Pearson Education Canada Inc.,Toronto, Ontario Sensation Psychophysics F 6.2