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
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 

51. 26. Distinguish between fast and slow muscle fibers.
Duration of muscle contraction is controlled by how long the Ca2+ concentration in the cytoplasm remains elevated
Slow  have longer-lasting twitches because Ca2+ remains in the cytoplasm longer (used for posture)
Fast  have short duration twitches and are used for rapid, powerful contractions
- able to sustain long periods of repeated contractions without fatiguing 

52. 27. Discuss cardiac and smooth muscle.
Cardiac  found only in the heart
- is striated; muscle cells are branched and the junction between cells contain intercalated discs that electrically couple all heart muscle cells, allowing coordinated action
- cells can generate action potentials
Smooth  lack striations
- generate less tension, but can contract over a greater range of lengths
- contractions are slow but have greater control
- found in the walls of blood vessels and digestive tract organs 