Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Senses
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential knowledge 3.E.2: Animals have nervous systems that detect external and internal signals, transmit and integrate information, and produce responses. – a. The neuron is the basic structure of the nervous system that reflects function. – b. Action potentials propagate impulses along neurons. – c. Transmission of information between neurons occurs across synapses. – d. Different regions of the vertebrate brain have different functions.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sensory receptors transduce stimulus energy and transmit signals (action potentials) to the central nervous system Sensations are action potentials that reach the brain via sensory neurons making us aware of sensory stimuli This information (sensations) is integrated with other information(previous experiences) and used to form a perception - a meaningful interpretation or conscious understanding of sensory data
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sensations and perceptions begin with sensory reception, the detection of stimuli by sensory receptors which are located in our sensory organs Sensory transduction occurs in the plasma membrane of the sensory receptor, when the cell converts one type of signal (the stimulus) into an electrical signal
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sensory Transduction All stimuli represent forms of energy Sensory transduction involves converting this energy into a change in the membrane potential of sensory receptors
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Amplification Amplification is the strengthening of stimulus energy by cells in sensory pathways
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Transmission After energy in a stimulus has been transduced into a receptor potential, some sensory cells generate action potentials, which are transmitted to the CNS
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Integration The integration of sensory information begins as soon as the information is received
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Another type of integration is sensory adaptation which is a decrease in responsiveness during continued stimulation When receptors become less sensitive, they trigger fewer action potentials and the brain may lose it’s awareness of a stimuli
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Types of Sensory Receptors Based on the energy they transduce, sensory receptors fall into five categories – Mechanoreceptors – Chemoreceptors – Electromagnetic receptors – Thermoreceptors – Pain receptors
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mechanoreceptors Mechanoreceptors sense physical deformation caused by stimuli such as pressure, stretch, motion, and sound (mechanical energy) The bending or stretching of the plasma membrane of a receptor cell causes the membrane to become permeable to positive ions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The mammalian sense of touch – Relies on mechanoreceptors that are the dendrites of sensory neurons
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chemoreceptors Chemoreceptors include – General receptors that transmit information about the total solute concentration of a solution – Specific receptors that respond to individual kinds of molecules (sugars, salts, acids, bases) –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Two of the most sensitive and specific chemoreceptors known are present in the antennae of the male silkworm moth, they detect pheromones or sex attractants
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Electromagnetic Receptors Electromagnetic receptors detect various forms of electromagnetic energy such as visible light, electricity, and magnetism
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some snakes have very sensitive infrared receptors that detect body heat of prey against a colder background
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many mammals appear to use the Earth’s magnetic field lines to orient themselves as they migrate
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Thermoreceptors Thermoreceptors, which respond to heat or cold –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pain Receptors In humans, pain receptors, also called nociceptors – – Respond to excess heat, pressure, or specific classes of chemicals released from damaged or inflamed tissues
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vision in Invertebrates Most invertebrates have some sort of light- detecting organ There are three types of eyes in invertebrates: 1.Eye cups 2.Compound eyes 3.Single-lens eye
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings One of the simplest is the eye cup of planarians –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Two major types of image-forming eyes have evolved in invertebrates –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Compound eyes are found in insects and crustaceans and consist of up to several thousand light detectors called ommatidia, they are especially good at detecting motion
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Single-lens eyes – Are found in some jellies, polychaetes, spiders, and many molluscs –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Vertebrate Visual System The eyes of vertebrates are camera-like, single lens eyes –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structure of the Eye The main parts of the vertebrate eye are – The sclera, which includes the clear cornea – The choroid, a pigmented layer found inside the sclera –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – The iris, which regulates the pupil – The retina, which contains photoreceptors –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Humans and other mammals – Focus light by changing the shape of the lens
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The human retina contains two types of photoreceptors (130 million) – Rods are sensitive to light but do not distinguish colors, contain visual pigment rhodopsin –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Rods occur in greatest density at outer edges of retina
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Rods contain the pigment rhodopsin – Which changes shape when it absorbs light
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Processing Visual Information When photopsin and rhodopsin change chemically, this causes a change in the membrane permeability, which stimulates a receptor potential
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In the dark, both rods and cones release their neurotransmitter into the synapses with neurons called bipolar cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In the light, rods and cones stop release of neurotransmitters
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Three other types of neurons contribute to information processing in the retina: ganglion cells, horizontal cells, and amacrine cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Signals from rods and cones travel from bipolar cells to ganglion cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Human Ear The mechanoreceptors involved with hearing and equilibrium detect settling particles or moving fluid Hearing and the perception of body equilibrium –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sensing Gravity and Sound in Invertebrates Most invertebrates have sensory organs called statocysts –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many arthropods sense sounds with body hairs that vibrate –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hearing and Equilibrium in Mammals In most terrestrial vertebrates – The sensory organs for hearing and equilibrium are closely associated in the ear
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sense of Hearing and Balance Anatomy of the Ear – – Middle ear begins at tympanic membrane and ends at oval and round windows Ossicles found between tympanic membrane and the windows Auditory tube (eustachian tube) extends from middle ear to nasopharynx – Inner ear has three areas Semicircular canals Vestibule Cochlea
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hearing Vibrating objects create percussion waves in the air that cause the tympanic membrane (eardrum) to vibrate The three bones of the middle ear transmit the vibrations to the oval window on the cochlea and help to amplify the vibrations – Hammer = malleus – Anvil = incus –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Malleus takes pressure from inner surface of tympanic membrane – Passes it to the stapes, multiplying the pressure along the way –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The organ of Corti contains hair cells (mechanoreceptors) embedded in the basilar membrane
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings These vibrations create pressure waves in the fluid in the cochlea that travel through the vestibular canal, back down the tympanic canal and ultimately strike the round window
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The pressure waves in the vestibular canal cause the basilar membrane to vibrate up and down striking the tectorial membrane, this causes its hair cells to bend
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The cochlea can distinguish pitch – Because the basilar membrane is not uniform along its length
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Each region of the basilar membrane vibrates most vigorously at a particular frequency and leads to excitation of a specific auditory area of the cerebral cortex
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Equilibrium Several of the organs of the inner ear –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sense of Balance Mechanoreceptors of rotational equilibrium are in semicircular canals – Detect rotational and/or angular movements of the head – Maintain rotational equilibrium – Mechanoreceptors of gravitational equilibrium are in the utricle and saccule – Detect straight-line movements of the head in any direction – Maintain gravitational equilibrium –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A swelling at the end of each semicircular canal called the ampulla contains a cluster of hair cells embedded in a gelatinous mass called the cupula When you move your head, the fluid in the canals moves more slowly, pressing against the cupula and bending the hair cells and generating receptor potentials
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The utricle and the saccule contain hair cells coated with a gelatinous layer that contains limestone crystals embedded in it
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Motion sickness Motion sickness may be a result of conflicting signals being sent to the brain from the equilibrium receptors in the inner ear and the visual receptors from our eyes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hearing and Equilibrium in Other Vertebrates Like other vertebrates, fishes and amphibians –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Most fishes and aquatic amphibians –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The lateral line system contains mechanoreceptors –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The senses of taste and smell are closely related in most animals The perceptions of gustation (taste) and olfaction (smell) –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The taste receptors of insects are located within sensory hairs called sensilla –
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Taste in Humans Five taste perceptions involve several signals from different classes of chemicals: Sweet, sour, salty, bitter, and umami (elicited by glutamate)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sense of Taste In humans, taste buds are located primarily on the tongue – – Have supporting cells and elongated taste cells that end in microvilli
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Transduction in taste receptors – Occurs by several mechanisms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Smell in Humans Olfactory receptor cells are neurons that line the upper portion of the nasal cavity and detect airborne chemicals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sense of Smell Sense of taste and smell – Work together to create a combined effect – Interpreted by the cerebral cortex Dependent on olfactory cells – Located within olfactory epithelium – In the roof of the nasal cavity
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings When odorant molecules bind to specific receptors – A signal transduction pathway is triggered, sending action potentials to the brain