50-54 Flashcards
CONCEPT: Sensory receptors transduce stimulus energy and transmit signals to the central nervous system
(pp. 1085–1090) - Sensory receptors - sensory transduction - transmission - Mechanoreceptors - Chemoreceptors - Electromagnetic receptors - thermoreceptors - nociceptors
Sensory receptors
are usually specialized neurons or epithelial cells that detect external or internal stimuli
sensory transduction
The detection of a stimulus by sensory cells precedes sensory transduction, the change in the membrane potential of a sensory receptor in response to a stimulus
transmission
The resulting receptor potential controls transmission of action potentials to the CNS, where sensory information is integrated to generate perceptions
stimulus strength.
The frequency of action potentials in an axon and the number of axons activated determine stimulus strength
five basic types of sensory receptors
Mechanoreceptors: respond to stimuli such as pressure, touch, stretch, motion, and sound. Chemoreceptors: detect either total solute concentrations or specific molecules. Electromagnetic receptors: detect different forms of electromagnetic radiation. Thermoreceptors signal: surface and core temperatures of the body Nociceptors: Pain is detected by a group of nociceptors that respond to excess heat, pressure, or specific classes of chemicals
CONCEPT: The mechanoreceptors responsible for hearing and equilibrium detect moving fluid or settling particles
(pp. 1090–1094) • Most invertebrates sense their orientation with respect to gravityby means of statocysts. Specialized hair cells form thebasis for hearing and balance in mammals and for detection of water movement in fishes and aquatic amphibians. In mammals, the tympanic membrane (eardrum) transmits sound waves to three small bones of the middle ear, which transmit the waves through the oval window to the fluid in the coiled cochlea of the inner ear. Pressure waves in the fluid vibrate the basilar membrane, depolarizing hair cells and triggering action potentials that travel via the auditory nerve to the brain. 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. Receptors in the inner ear function in balance and equilibrium.
Statocysts.
Most invertebrates sense their orientation with respect to gravity by means of statocysts. Specialized hair cells form the basis for hearing and balance in mammals and for detection of water movement in fishes and aquatic amphibians
Tympanic membrane
In mammals, the tympanic membrane (eardrum) transmits sound waves to three small bones of the middle ear, which transmit the waves through the oval window to the fluid in the coiled cochlea of the inner ear.
basilar membrane
Pressure waves in the fluid vibrate the basilar membrane, depolarizing hair cells and triggering action potentials that travel via the auditory nerve to the brain. 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. Receptors in the inner ear function in balance and equilibrium.
CONCEPT Visual receptors in diverse animals depend on light-absorbing pigments
(pp. 1095–1101) • Invertebrates have varied light detectors, including simple lightsensitive eyespots, image-forming compound eyes, and singlelens eyes. In the vertebrate eye, a single lens is used to focus light on photoreceptors in the retina. Both rods and cones contain a pigment, retinal, bonded to a protein (opsin). Absorption of light by retinal triggers a signal transduction pathway that hyperpolarizes the photoreceptors, causing them to release less neurotransmitter. Synapses transmit information from photoreceptors to cells that integrate information and convey it to the brain along axons that form the optic nerve.
CONCEPT The senses of taste and smell rely on similar sets of sensory receptors
(pp. 1101–1103) Both taste (gustation) and smell (olfaction) depend on the stimulation of chemoreceptors by small dissolved molecules that bind to proteins on the plasma membrane. In humans, sensory cells within taste buds express a single receptor type specific for one of the five taste perceptions—sweet, sour, salty, bitter, and umami (elicited by glutamate). Olfactory receptor cells line the upper part of the nasal cavity and extend axons to the olfactory bulb of the brain. More than 1,000 genes code for membrane proteins that bind to specific classes of odorants, and each receptor cell appears to express only one of those genes.
CONCEPT The physical interaction of protein filaments is required for muscle function
(pp. 1103–1110) The muscle cells (fibers) of vertebrate skeletal muscle contain myofibrils composed of thin filaments of (mostly) actin and thick filaments of myosin. Motor neurons release acetylcholine, triggering action potentials that penetrate the muscle fiber along the T tubules and stimulate the release of Ca2 from the sarcoplasmic reticulum. When the Ca2 binds the troponin complex, tropomyosin repositions on the thin filaments, exposing the myosin-binding sites on actin and thus initiating cross-bridge formation. A motor unit consists of a motor neuron and the muscle fibers it controls. Recruiting multiple motor units results in stronger contractions. A twitch results from a single action potential in a motor neuron. Cardiac muscle, found only in the heart, consists of striated cells that are electrically connected by intercalated disks and that can generate action potentials without input from neurons.
CONCEPT Skeletal systems transform muscle contraction into locomotion
(pp. 1110–1115) Skeletal muscles, often in antagonistic pairs, bring about movement by contracting and pulling against the skeleton. Skeletons may be hydrostatic and maintained by fluid pressure, as in worms; hardened into exoskeletons, as in insects; or in the form of endoskeletons, as in vertebrates. • Each form of locomotion—swimming, movement on land, or flying—presents a particular challenge. For example, swimmers need to overcome friction, but face less of a challenge from gravity than do animals that move on land or fly. Animals specialized for swimming expend less energy per distance traveled than similarly sized animals specialized for flying or running. For any of the three major modes of locomotion, larger animals are more efficient than smaller ones.
50:1 test Which of the following sensory receptors is incorrectly paired with its category? a. hair cell—mechanoreceptor b. muscle spindle—mechanoreceptor c. taste receptor—chemoreceptor d. rod—electromagnetic receptor e. olfactory receptor—electromagnetic receptor
e
50:1 test The middle ear converts a. air pressure waves to fluid pressure waves. b. fluid pressure waves to air pressure waves. c. air pressure waves to nerve impulses. d. fluid pressure waves to nerve impulses. e. pressure waves to hair cell movements.
a
50:1 test During the contraction of a vertebrate skeletal muscle fiber, calcium ions a. break cross-bridges by acting as a cofactor in the hydrolysis of ATP. b. bind with troponin, changing its shape so that the myosin-binding sites on actin are exposed. c. transmit action potentials from the motor neuron to the muscle fiber. d. spread action potentials through the T tubules. e. re-establish the polarization of the plasma membrane following an action potential.
b
50:2 test Which sensory distinction is not encoded by a difference in neuron identity? a. white and red d. salty and sweet b. red and green e. spicy and cool c. loud and faint
c
50:2 test The transduction of sound waves into action potentials takes place: a. within the tectorial membrane as it is stimulated by the hair cells. b. when hair cells are bent against the tectorial membrane, causing them to depolarize and release neurotransmitter that stimulates sensory neurons. c. as the basilar membrane becomes more permeable to sodium ions and depolarizes, initiating an action potential in a sensory neuron. d. as the basilar membrane vibrates at different frequencies in response to the varying volume of sounds. e. within the middle ear as the vibrations are amplified by the malleus, incus, and stapes.
b
50:3 test Although some sharks close their eyes just before they bite, their bites are on target. Researchers have noted that sharks often misdirect their bites at metal objects and that they can find batteries buried under sand. This evidence suggests that sharks keep track of their prey during the split second before they bite in the same way that: a. a rattlesnake finds a mouse in its burrow. b. a male silkworm moth locates a mate. c. a bat finds moths in the dark. d. a platypus locates its prey in a muddy river. e. a flatworm avoids light places.
d
CONCEPT Earth’s climate varies by latitude and season and is changing rapidly
(pp. 1144–1150) • Global climate patterns are largely determined by the input of solar energy and Earth’s revolution around the sun. • The changing angle of the sun over the year, bodies of water, and mountains exert seasonal, regional, and local effects on macroclimate. •Fine-scale differences in abiotic (nonliving) factors, such as sunlight and temperature, determine microclimate. • Increasing greenhouse gas concentrations in the air are warming Earth and altering the distributions of many species. Some species will not be able to shift their ranges quickly enough to reach suitable habitat in the future.
climate
Global climate patterns are largely determined by the input of solar energy and Earth’s revolution around the sun.
macroclimate.
changing angle of the sun over the year, bodies of water, and mountains exert seasonal, regional, and local effects
abiotic
abiotic (nonliving) factors. Fine-scale differences in abiotic (nonliving) factors, such as sunlight and temperature, determine microclimate.


