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Bio 103
Lake Tahoe Community College
Winter Quarter
Instructor: Sue Kloss
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Chapter 50 - The Senses
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I. Intro- Sensory inputs become sensations and perceptions in the brain
A. Sensory receptor cells sense internal and external conditions/stimuli
1. Stimuli include heat, cold, electricity, touch, chemicals, light, muscle tension, sounds
2. sensory receptor cells detect stimuli and then send reports to the brain
3. reports take the form of action potentials; in sensory cells, this is called receptor potential
4. receptor’s job is finished action potential goes to cns
B. sensation = when sensory action potential reaches the brain = an awareness of sensory stimuli
1. sensations result when the brain integrates new information
2. If you have no prior experience with or memory of a sensation, it stays a sensation.
3. Brain integrates sensation with other information and forms a perception
C. Researchers using brain imaging techniques are beginning to find out what the brain actually does
1. communication among neurons arranged in complex circuitry
2. neuronal communication
II. Sensory Reception
A. Sensory receptor cells convert stimuli into electrical energy
1. Sensory organs such as your taste buds contain specialized receptor cells
2. taste bud cells detect chemicals dissolved in saliva
3. Stimulus detection
4. sensory transduction
5. molecules enter taste bud
6. molecules bind to specific protein molecules
7. binding causes ion channels in membrane to open
8. Positively charged ions flow into the cell from the surrounding fluid
9. receptor potential is the electrical signal produced by sensory transduction
10. Action potentials are all or none
B. Once a stimulus is converted to a receptor potential, the receptor potential usually results in signals entering the cns
1. each receptor cell forms a synapse with a sensory neuron
2. receptor cell similar presence of no sugar, then again transmitting action potential in
presence of a lot of sugar.
3. So transduction of stimuli by sensory receptors is converting a stimulus to electrical signals.
4. These electrical signals can trigger action potentials that go to cns for processing
5. Since action potentials are only electrical signals
6. sensory neurons for salty tastebuds synapse w/interneurons in the brain
7. Increasing frequency of action potentials are different for increasing levels of intensity of the stimulus
8. sensory adaptation
9. when receptors are stimulated repeatedly, they trigger fewer action potentials
10. sensory adaptation keeps the body from reacting to normal background stimuli
C. Specialized sensory receptors detect 5 categories of stimuli: pain, thermo, mechano, chemo and electromagnetic
receptors.
1. Our skin contains receptors for each of these types of stimuli
2. most neurons in the skin are wrapped in connective tissue
3. pain receptors - probably all animals have these;
4. thermoreceptors - detect heat or cold.
5. hypothalamus is the body’s thermostat.
6. mechanoreceptors - highly diverse. Include receptors for touch, pressure, stretching, motion, and sound.
7. as membrane changes shape, it becomes more permeable to positive ions
8. mechanoreceptors include light touch, pressure, touch (at base of hairs);
9. chemoreceptors - include sensory cells in nose and taste buds, attuned to chemicals in the external
environment.
10. Electromagnetic receptors are sensitive to energy of various wavelengths, which take form of electricity,
magnetism, light.
III. Vision = many types of light detectors have evolved in animal kingdom
A. types of Eyes
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1. Eye cup - e.g. found in planarian worms
2. Compound eyes- have lenses and form images
3. Single lens eye
B. Vertebrates have single lens eyes
1. Eyes of humans and eyes of squids (invertebrates with single lens eyes) evolved independently
2. Sclera
3. Cornea
4. thin mucus membrane called conjunctiva keeps eye moist
5. iris - formed by choroid at front of eye
6. muscles in front of eye
7. light passes through lens
8. lens focuses images onto the retina
9. photoreceptors in retina transduce images into action potentials
10. retina’s center of focus is called fovea
11. place where optic nerve passes thru back of eye is blind spot
12. chamber behind lens/ciliary body (which makes the aqueous humors) is filled with vitreous humor
13. chamber in front of lens is filled with liquid aqueous humor
14. aqueous humor circulates
15. humors act like liquid lenses to help focus light on retina
C. To focus, a lens changes shape or position
1. lens focuses light onto a retina by bending light rays
2. focusing can occur in 2 ways
D. Our photoreceptors are rods and cones
1. cones are stimulated by bright light and can see color
2. Rods extremely sensitive to light
3. Rods found at edges of retina and absent from fovea
4. Cones are densest in the fovea
5. hawks have 10x more cones in fovea than we do
6. Each rod and cone has light absorbing discs
7. Rods contain visual pigments called rhodopsin
8. Cones contain visual pigments called photopsin, absorb light of different wavelengths we see as color
9. We have 3 types of cones, each has a different type of photopsin and can detect green, blue, yellow
10. together they can absorb the range of light that is visible to humans
11. light from each color triggers a unique pattern
12. Color blindness results from deficiency
13. rodopsin and photopsin pigment cells change chemically
14. visual information is integrated both before it gets to the brain
IV. Hearing and Balance
A. Ear converts air pressure waves into action potentials that are perceived as sound
1. Ear is 2 separate organs - for hearing and balance - both operate using hair cells
2. Ear structure (
3. three regions: inner, outer and middle ear.
4. outer ear is auditory canal and pinna - flaplike structure we call our ear
5. In the inner ear are 3 small bones- hammer (malleus), anvil (incus) and stirrup (stapes)
6. inner ear - fluid filled channels in bones of skull
B. Inner ear houses our organ of balance
1. semicircular canals, utricle and saccule lie next to the cochlea
V. Taste and Smell
A. Odor and taste receptors detect categories of chemicals
1. chemoreceptors in nose and tongue
2. eg. some receptors in nose respond to chemicals that are spicy
3. same receptor cells send action potentials
4. 4 taste receptors on tongue - sweet sour salty bitter
5. Insects have taste receptors on feet
6. Receptor cells respond to a broad range of chemicals
Animal skeletons function in movement
I. Skeletal Support
A. A skeleton has many functions.
1. An animal could not move without its skeleton
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B.
II.
A.
B.
C.
D.
E.
2. Even water animals would be a formless mass
3. skeletons also provide protection
4. there are 3 main types of skeletons- hydrostatic, exoskeletons and endoskeletons.
human skeleton is a unique variation on an ancient theme
1. human skeleton supports an upright body that sits on hindquarters and walks or runs on 2 legs
2. similarities of animal skeletons
3. Moveable joints give versatility to vertebrate skeleton
Muscle Contraction and Movement
skeleton and muscles interact in movement
1. tendons - connect muscles to bones
2. biceps connects to shoulder bones by a tendon
3. antagonistic muscle groups have opposite effects
4. triceps attaches by a tendon to the elbow
5. under its own power, a muscle can only contract
Each muscle has its own contractile apparatus
1. skeletal muscle is attached to the skeleton and produces movement
2. A muscle consists of bundles of parallel muscle fibers.
3. each muscle fiber consists of many parallel, smaller myofibrils.
4. Myofibrils consist of repeating units called sarcomeres.
muscles contract when thin filaments slide across thick filaments
1. sliding filament model of muscle contraction - A.F. Huxley (1950)
2. sarcomeres contract when thin filaments slide across thick filaments
3. relaxed, contracting and contracted muscle.
4. filaments themselves don’t change shape, they over lap.
5. a whole muscle can contract to about .5 resting length
6. what makes filaments slide in muscle contraction
7. Muscle structure relates to function
Motor Neurons stimulate muscle contraction
1. Sarcomeres are stimulated to contract by motor neurons
2. typical motor neuron can stimulate more than one muscle fiber; each neuron has many branches
3. motor unit = neuron and all the muscle fibers it controls (2 or 3 in this case)
4. motor unit has dendrites and cell bodies in the cns
5. axons form synapses, called neuromuscular junctions in muscle fibers
6. when motor neuron sends out action potential, synaptic knobs release acetylcholine; it diffuses across
neuromuscular junctions to muscle fibers, making all fibers of a motor unit contract simultaneously
7. how many motor units
8. As in a synapse, an action potential carried by a change in electrical charge
9. Ca2+ is used as a “pump”
Athletic training increases strength and endurance
1. what causes fatigue in muscles? anaerobic production of ATP produces lactic acid
2. anaerobic vs. aerobic exercise
3. slow and fast twitch muscle fibers
III. Movement and Locomotion
A. Diverse means of animal locomotion have evolved
1. Animals move in place, like a sponge, or by traveling from place to place, called locomotion. Locomotion
requires animals to expend energy to overcome 2 forces - friction and gravity.
2. Swimming is not much affected by gravity,
3. Locomotion on land
4. Maintaining balance is another problem to solve for animals who live on land.
5. Crawling animals like snakes and worms must deal with considerable friction since much of the body
surface is in contact with the ground at any given time.
6. Flying animals include insects, bats, birds and reptiles. Flying reptiles died out millions of years ago,
leaving birds and bats as the only flying vertebrates.
7. Similarities in all kinds of animal movement
8. Comparing costs of locomotion
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Ch 50 Objectives
1. Differentiate between sensation and perception.
2. Describe the four general functions of receptor cells as they convert energy stimuli into changes in membrane potentials
and then transmit signals to the central nervous system.
3. Distinguish between sensory transduction and receptor potential.
4. Explain the importance of sensory adaptation.
5. List the five types of sensory receptors and explain the energy transduced by each type.
6. Compare the structures of, and processing of light by, the eyecups of Planaria, the compound eye of insects, and the
single-lens eyes of molluscs.
7. Refer to a diagram of the vertebrate eye to identify and give the function of each structure.
8. Describe the functions of the rod cells and cone cells of the vertebrate eye. Explain and compare how the rods and
cones of the retina transduce stimuli into action potentials.
9. Explain how the retina assists the cerebral cortex in the processing of visual information.
10. Describe three functions of a skeleton.
11. Describe how hydrostatic skeletons function.
12. Distinguish between an exoskeleton and an endoskeleton.
13. Explain how the structure of the arthropod exoskeleton provides both strength and flexibility.
14. Explain how a skeleton combines with an antagonistic muscle arrangement to provide a mechanism for movement.
15. Using a diagram, identify the components of a skeletal muscle cell.
16. Explain the sliding-filament model of muscle contraction.
17. Explain how muscle contraction is controlled at the molecular level and by the nervous system.
18. Explain the adaptive advantages of slow and fast muscle fibers.
19. List the advantages and disadvantages associated with moving through:
a. an aquatic environment
b. a terrestrial environment
c. air
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Study Questions
1. Explain how the skeleton of leaf cutter ants promotes diverse activity such as feeding and nesting.
2. describe the diverse methods of locomotion and the forces each must resist.
3. Describe the 3 types of skeletal systems, and advantages, disadvantages and examples of each.
4. Describe the overall arrangement of vertebrate skeletons into axial and appendicular subsystems. Include major
bones.
5. Describe 3 types of joints and give examples of each.
6. Describe some common skeletal disorders.
7. Describe the complex structure of a bone, noting major tissues that contribute to bones and their function.
8. Explain why bones break and how we can help them heal.
9. Explain how muscles relengthen once contracted.
10. Describe the structure and arrangement of filaments inside a muscle cell.
11. Explain details of how a muscle contracts.
12. Describe the structure and significance of motor units.
13. Explain how a motor neuron makes a muscle fiber contract.
14. Describe the role of Ca in a muscle contraction.
15. Explain what causes muscles to tire. Distinguish between anaerobic and aerobic exercise. Note advantages of each.
Chapter 29 Study Questions
1.
2.
3.
4.
Explain how salmon navigate from streams and back again during their lifetime.
Define and compare sensations and perceptions.
Define sensory transduction, a receptor potential, and sensory adaptation. Illustrate each with examples.
Describe the five general categories of sensory receptors found in animals. note examples of each. Identify the
receptors that are responsible for mechanical and thermal perception by the skin.
5. Describe and compare the three main types of photoreceptors found in animals, and contrast the qualities of perception
in each.
6. Describe the parts of the human eye and their function. Explain how stimuli start to be integrated directly by the eye.
7. Explain the causes and symptoms of hyperopia, myopia, presbyopia, and astigmatism.
8. Compare the structures and functions, distributions, and densities of rods and cones.
9. List and describe, in order, the structures of the ear involved in hearing. Trace a sound pattern through the auditory
pathway. Describe the possible causes hearing loss.
10. Explain how body position and movement are sensed in the inner ear.
11. Explain what causes motion sickness and what can be done to prevent it.
12. Explain how odor and taste receptors help contribute to the senses of smell and taste.
Explain the role of the central nervous system in sensory perception.
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