| A | B |
|---|
| A band | region that corresponds to the length of the thick filaments of myofibrils |
| accommodation | automatic adjustment of an eye to focus on near objects |
| amacrine cell | neuron of the retina that helps integrate information before it is sent to the brain |
| amplification | strengthening of stimulus energy that is otherwise too weak to be carried into the nervous system |
| aqueous humor | Plasma-like liquid in the space between the lens and the cornea |
| bipolar cell | neuron that synapses with the axon of a rod or cone in the retina of the eye |
| cardiac muscle | forms the contractile wall of the heart cells are joined by intercalated disks that relay each heartbeat |
| chemoreceptor | transmits information about the total solute concentration in a solution or about individual kinds of molecules |
| chitin | structural polysaccharide of an amino sugar found in many fungi and in the exoskeletons of all arthropods |
| choroid | thin |
| ciliary body | portion of the vertebrate eye associated with the lens |
| cochlea | complex |
| compound eye | multifaceted eye in insects and crustaceans consisting of up to several thousand light-detecting focusing ommatidia |
| cone cell | detects color during the day |
| conjunctiva | mucous membrane that helps keep the eye moist |
| cornea | transparent frontal portion of the sclera admits light into the vertebrate eye |
| electromagnetic receptor | receptor of electromagnetic energy |
| endoskeleton | hard skeleton buried within the soft tissues of an animal |
| Eustachian tube | connects the middle ear to the pharynx |
| exoskeleton | hard encasement on the surface of an animal provides protection and points of attachment for muscles |
| exteroreceptor | sensory receptor that detects stimuli outside the body |
| eye cup | simple light-detecting organ in planarians that provides information about light intensity and direction but does not form images |
| fast muscle fibers | muscle cells used for rapid powerful contraction |
| fovea | center of focus and the place on the retina where photoreceptors are highly concentrated |
| ganglion cell | neuron in the retina that synapses with bipolar cells and transmits action potentials to the brain via axons in the optic nerve |
| gustatory receptor | taste receptor |
| hair cell | mechanoreceptor that detects sound waves and other forms of movement in air or water |
| horizontal cell | neuron of the retina that helps integrate information before it is sent to the brai |
| hydrostatic skeleton | skeletal system composed of fluid held under pressure in a closed body compartment |
| I band | area near the edge of the sarcomere where there are only thin filament |
| incus | second of the three middle ear bones a.k.a. anvil |
| inner ear | includes the cochlea organ of Corti and semicircular canals |
| integration | interpretation of sensory signals within neural processing centers of the central nervous system |
| intercalated disk | specialized junction between cardiac muscle cells that provides direct electrical coupling between cells |
| interoreceptor | sensory receptor that detects stimuli within the body |
| lateral geniculate nuclei | destination in the thalamus for most of the ganglion cell axons that form the optic nerves |
| lateral inhibition | process that sharpens the edges and enhances the contrast of a perceived image by inhibiting receptors lateral to those that have responded to light |
| lateral line system | series of pores and receptor units (neuromasts) along the sides of the body in fishes and aquatic amphibians |
| lens | structure in an eye that focuses light rays onto the retina |
| locomotion | active movement from place to place |
| malleus | first of the three middle ear bones a.k.a. hammer |
| mechanoreceptor | detects physical deformations in the body’s environment associated with pressure touch stretch motion and sound |
| middle ear | a chamber containing three small bones that convey vibrations from the eardrum to the oval window |
| motor unit | single motor neuron and all the muscle fibers it controls |
| muscle spindle | mechanoreceptor stimulated by mechanical distortion |
| myofibril | fibril collectively arranged in longitudinal bundles in muscle cells |
| myofilaments | thick and thin filaments that form the myofibrils |
| myoglobin | oxygen-storing pigmented protein in muscle cells |
| nociceptor | naked dendrites in the epidermis of the skin. |
| olfactory receptor | smell receptor |
| ommatidium | one of the facets of the compound eye of arthropods |
| opsin | membrane protein bonded to a light-absorbing pigment molecule |
| optic chiasm | nerve tracts of the eye such that the visual sensations from left are interpreted by right side of brain and visa versa |
| organ of Corti | actual hearing organ of the vertebrate ear |
| outer ear | made up of the auditory canal and the pinna |
| oval window | membrane-covered gap in the skull bone through which sound waves pass from the middle ear to the inner ea |
| pain receptor | interoreceptor that detects pain |
| perception | interpretation of sensations by the brain |
| peristalsis | movement on land produced by rhythmic waves of muscle contractions passing from front to back as in many annelids |
| photopsin | family of visual pigments in the cones of the vertebrate eye that absorb bright colored light |
| photoreceptor | electromagnetic receptor that detects the radiation known as visible light |
| pitch | function of a sound wave’s frequency or number of vibrations per second expressed in hertz |
| primary visual cortex | destination in the occipital lobe of the cerebrum for most of the axons from the lateral geniculate nuclei |
| pupil | opening in the iris admits light into the interior of the vertebrate eye |
| receptor potential | initial response of a receptor cell to a stimulus consisting of a change in voltage across the receptor membrane proportional to the stimulus strength |
| recruitment | process of progressively increasing the tension of a muscle by activating more and more of the motor neurons controlling the muscle |
| retina | innermost layer of the vertebrate eye containing photoreceptor cells |
| retinal | light-absorbing pigment in rods and cones of the vertebrate eye |
| rhodopsin | visual pigment consisting of retinal and opsin |
| rod cell | sensitive to black and white and enables night vision |
| round window | where the vibrations of the stapes create a traveling series of pressure waves in the fluid of the cochlea |
| saccule | chamber in the vestibule behind the oval window that participates in the sense of balance |
| sarcomere | repeating unit of striated muscle delimited by the Z lines |
| sarcoplasmic reticulum (SR) | specialized endoplasmic reticulum that regulates the calcium concentration in the cytosol |
| sclera | tough white outer layer of connective tissue that forms the globe of the vertebrate eye |
| semicircular canals | three-part chamber of the inner ear that functions in maintaining equilibrium |
| sensation | impulse sent to the brain from activated receptors and sensory neuron |
| sensory adaptation | tendency of sensory neurons to become less sensitive when they are stimulated repeatedly |
| sensory reception | detection of the energy of a stimulus by sensory cells |
| sensory receptor | cellular system that collects information about the physical world outside the body and inside the organism |
| sensory transduction | conversion of stimulus energy to a change in the membrane potential of a sensory receptor |
| single-lens eye | camera-like eye |
| skeletal muscle (striated muscle) | Muscle generally responsible for the voluntary movements of the body |
| sliding-filament model | theory explaining how muscle contracts |
| slow muscle fibers | muscle cells that can sustain long contractions |
| smooth muscle | muscle lacking the striations of skeletal and cardiac muscle because of the uniform distribution of myosin filaments in the cell |
| stapes | third of the three middle ear bones a.k.a. stirrup |
| statocyst | mechanoreceptor that functions in equilibrium in invertebrates through the use of statoliths which stimulate hair cells in relation to gravity |
| statolith | specialized plastid that contains dense starch grains and may play a role in detecting gravity |
| taste buds | collections of modified epithelial cells that are scattered in several areas of the tongue and mouth |
| tetanus | sustained contraction of a skeletal muscle |
| thermoreceptor | interoreceptor stimulated by either heat or cold |
| thick filament | filament composed of staggered arrays of myosin molecules |
| thin filament | myofilaments consisting of two strands of actin and two strands of regulatory protein coiled around one another |
| transmission | conduction of impulses to the central nervous system |
| transverse (T) tubules | infoldings of the plasma membrane of skeletal muscle cells |
| tropomyosin | protein that blocks the myosin-binding sites on the actin molecules |
| troponin complex | proteins that control the position of tropomyosin on the thin filament |
| tympanic membrane | Another name for the eardrum |
| utricle | chamber behind the oval window that opens into the three semicircular canals |
| vitreous humor | jellylike material that fills the posterior cavity of the vertebrate eye |
| Z lines | borders of a sarcomere |
