Chapter 49 Reading Quiz

1. Chapter 49 Reading Quiz • The strengthening of stimulus energy is called… • What is the processing of sensory information called? • What do thermoreceptors respond to? • Through which structure of the eye does light actually enter? • Besides the sense of hearing, what other function does the ear have?

2. 1. Define sensory reception, sensory receptors, exteroreceptors, and interoreceptors. • Sensory reception  ability of a cell to detect the energy of a stimulus • Sensory receptors  structures that transmit information about changes in an animal’s internal and external environment • Exteroreceptors  detect external stimuli, such as heat, pressure, light, and chemicals • Interoreceptors  detect internal stimuli, such as blood pressure and body position 

5. 2. Describe what happens during sensory transduction. • It is the conversion of stimulus energy into a change in the membrane potential of a receptor cell • Sensory energy changes the membrane permeability of the receptor cell and results in a graded change in the membrane potential called “receptor potential” 

6. 3. Describe what happens during amplification. • The amplification of stimulus energy that is too weak to be carried into the nervous system often occurs • It may take place in accessory structures or be a part of the transduction process Ex: sound waves are enhanced 20X before reaching inner ear Ex: an action potential can have 100,000X as much energy as the couple light photons that triggered the reaction 

7. 4. Describe what happens during transmission. • Transmission of a sensation to the CNS occurs in 2 ways: • The receptor cell doubles as a sensory neuron – in this case the intensity of the receptor potential will affect the frequency of action potentials that convey sensations to the CNS • The receptor cell transmits chemical signals (neurotransmitters) across a synapse to a second sensory neuron – in this case the receptor potential affects the amount of neurotransmitter that is released, which in turn influences the frequency of action potential generated by the sensory neuron 

8. 5. Describe the process of integration. • Receptor signals are integrated through summation of graded potentials • “Sensory adaptation” is a decrease in sensitivity during continued stimulation; a type of integration that results in selective information being sent to the CNS • The threshold for transduction by receptor cells varies with conditions resulting in a change in receptor sensitivity • Sensory information integration occurs at all levels in the nervous system 

9. 6. How are sensory receptors categorized? How many categories are there? List them. • Receptors can be grouped into five types depending on the type of energy they detect • Mechanoreceptors  physical touch • Nociceptors  pain • Thermoreceptors  temperature • Chemoreceptors  chemicals • Electromagnetic receptors  light, electricity 

10. 7. Describe the function of mechanoreceptors. • They are stimulated by physical deformation caused by pressure, touch, stretch, motion, and sound (all forms of mechanical energy) • Bending in the plasma membrane increases its permeability to Na+ and K+ resulting in a receptor potential 

12. 8. What is the function of pain receptors? • The nociceptors are a class of naked dendrites that function as pain receptors • Different groups respond to excess heat, pressure, or specific chemicals released from damaged or inflamed tissue • Prostaglandins increase pain by lowering receptor thresholds • Aspirin and ibuprofen reduce pain by inhibiting prostaglandin synthesis 

13. 9. What do thermoreceptors do? • Respond to heat or cold and help regulate body temperature • Still debate about the identity of thermoreceptors in the mammalian skin; they may be two receptors consisting of encapsulated, branched dendrites or the naked dendrites of certain sensory neurons • The interothermoreceptors in the hypothalamus function as the primary temperature control of the mammalian body 

14. 10. Describe how chemoreceptors work, and name two types. • Include  - general receptors that sense total solute concentration (osmoreceptors in brain) - receptors that respond to individual molecules - those that respond to categories of related chemicals (gustatory and olfactory receptors) 

15. 11. Describe how electromagnetic receptors work, and discuss two forms people know about. • These respond to electromagnetic radiation such as light, electricity, and magnetic fields • A great variety of light detectors has evolved in animals, from simple clusters of cells to complex organs • Molecular evidence indicates that most, if not all, photoreceptors in animals may be homologous 

18. 12. Describe how photoreceptors work, and describe the simplest type, and compound eyes. • The “eye cup” of planarians is a simple light receptor that responds to light intensity and direction without forming an image - light enters opening of cup and stimulates photoreceptors that contain light-absorbing pigments - proper direction to move is determined by the brain • The compound eye contains thousands of light receptors called ommatidia, each has its own cornea and lens - results in a mosaic image - more acute at detecting movement - insects, crustaceans, some polychaete worms 

21. 13. Briefly outline the single-lens vertebrate eye and it’s components. • The vertebrate eye consists of a tough outer layer of connective tissue (the sclera) and a thin inner pigmented layer (the choroid) - the conjunctiva covers the sclera and keeps the eye moist • The cornea is located in front and is a transparent area of the sclera that allows light to enter the eye and act as a fixed lens • The anterior choroid forms the iris, which regulates the amount of light entering the pupil • The retina is the innermost layer of the eyeball that contains photoreceptor cells which transmit signals from the optic disc, where the optic nerve attaches to the eye • Vitreous and aqueous humor help to focus light onto the retina • Rod cells  light; cone cells  color 

24. 14. Define retinal, opsin, rhodopsin, and photopsin. • Retinal  synthesized from vitamin A; light-absorbing; bonded to membrane protein opsin • Opsin  membrane protein; several classes • Rhodopsin  rods contain their own type of opsin, and when combined with retinal, make up rhodopsin • Photopsin  special types of opsin that form visual pigments 

25. 15. How does the retina work to help process visual information? • Integration of visual information begins at the retina • Rod & cone cell axons synapse with neurons called bipolar cells, which in turn synapse with ganglion cells – these convey action potentials along the optic nerve to the brain • Optic nerves from each eye meet at the optic chiasm 

29. 16. Outline the mammalian ear, and describe the function of each component. • Sound waves are collected by the outer ear and channeled to the tympanic membrane of the middle ear which vibrates • The waves are then transmitted to 3 small bones: malleus, incus, and stapes • Here the sound is amplified & transmitted to the oval window, a membrane of the cochlea surface • The middle ear opens into the Eustachian tube, a channel that helps equalize pressure on both sides of the tympanic membrane • Oval window vibrations produce pressure waves in the fluid in the cochlea of the inner ear • The pressure waves vibrate the organ of Corti which contains receptor hair cells • The bending hair causes depolarization and neurotransmitters trigger an action potential 

31. 17. What is pitch? • Pitch  a function of a sound wave’s frequency, or number of vibrations per second, expressed in Hertz (Hz) • Short, high frequency waves produce high-pitched sound • Long, low frequency waves generate low-pitched sound • Humans can hear in the 20 to 20,000 Hz range, dogs can hear up to 40,000 Hz 

33. 18. How does the inner ear also sense equilibrium? • Several organs in the inner ear detect body position and balance • Hair cells in the utricle and saccule (2 chambers behind the oval window) respond to changes in head position with respect to gravity and movement in one direction • Otoliths (made of CaCO3) settle on the hairs and create constant action potentials to indicate position of the head • Semicircular canals detect rotation of the head due to endolymph movement against the hair cells 

35. 19. Describe how the lateral line system works in fish. • Runs along both sides of the body • Mechanoreceptors called neuromasts contain hair cell clusters whose hairs are embedded in a gelatinous cap, the cupula • Water enters the system through numerous pores on the animal’s surface and flows along the tube past the neuromasts • Pressure of moving water bends the cupula causing an action potential in the hair cells • This provides information about the body’s movement, direction, and velocity of water currents; also info on predators &/or prey 

37. 20. Define statocysts and statoliths, and describe their function. • Statocysts  mechanoreceptors that function in their sense of equilibrium • Located along the bell fringe of many jellies and at the antennule bases in lobsters and crayfish • Statoliths  dense granules settle to the low point in a chamber, stimulating hair cells in that location • Function is to detect direction of gravity 

39. 21. How are taste and smell interrelated? • Taste buds are receptor cells for sweet, salty, sour and bitter, which are associated with specific molecular shapes and charges that bind to separate receptor molecules • Specific receptors respond to certain odorous molecules by depolarizing • Taste and olfaction have different receptors but do interact 

41. 22. Define taste bud, and describe what they do. • Receptor cells for taste are organized into taste buds, which are scattered in several areas of the tongue and mouth • They associate molecules as “tastes” 

42. 23. The three main types of locomotion. • Swimming  must overcome water resistance, many are streamlined • Locomotion on land  must support itself against gravity, must maintain balance • Flying  do not use skeleton for support during motion, must completely overcome gravity to become airborne, key is in the shape of the wings 

44. 24. Describe the three types of skeletons found in the animal kingdom. • Hydrostatic  consist of fluid held under pressure in a closed body compartment - found in cnidarians, flatworms, annelids 2. Exoskeletons  hard encasement deposited on the surface of the animal • Endoskeletons  hard supporting elements buried within the soft tissues of an animal - bones in vertebrates can act as levers for muscles 

46. 25. Briefly describe how vertebrate skeletal muscle contracts. (The sliding-filament theory) • Skeletal muscle  bundle of long fibers running the length of the muscle; attached to bones and responsible for their movement • Each fiber is a single cell with many nuclei; consists of bundles of smaller myofibrils arranged longitudinally • There are two kinds of myofilaments in each myofibril: 1. Thin  consist of actin 2. Thick  consist of myosin • The unit of organization of muscle is the sarcomere 

47. #25 continued… • Muscle contraction reduces the length of each sarcomere • Thin filaments ratchet across thick to shorten the sarcomere, the actin and myosin themselves do not contract • Myosin molecules attach to actin to form a cross-bridge, energy for this formation comes from the hydrolysis of ATP 