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outline 9
Comparative Physiology- Renner Lecture 9
| Question | Answer |
|---|---|
| what is the primary role of the nervous system? | take info from environment and internal structures, process info and relay messages for the appropriate response |
| _____________ detect initial signals | receptors |
| what are the three major categories of receptors ? | 1. mechanoreceptors 2. radioreceptors 3. chemoreceptors |
| what do mechano-receptors detect? | touch, pressure, low frequency vibrations (sound) |
| what do radio-receptors detect? | high frequency vibrations, heat, light. ex: eye, pit organ of rattlesnake (heat) |
| what do chemo-receptors detect? | chemical agents. olfactory epithelium, taste buds |
| how do sensory receptors respond to a stimulus? | by an increase in membrane permeability to Na+, resulting in local depolarization |
| receptor potentials are generated by_____________ | isolated receptors; which are receptors that are separate from the sensory neuron |
| T/F: response in receptors cannot be summed in magnitude | FALSE. unlike in AP, it can be summed |
| response to stimulus is graded with respect to _____________ | stimulus strength |
| what is meant by afferent? | signal sent to the CNS |
| response to stimulus impact ______________fiber and it occurs through chemical ___________________ | sensory afferent, neurotransmission |
| what do signals do? | activate voltage gated channels at terminal of an afferent sensory fiber or can generate AP at the terminal |
| signals activate ______________ at terminal of an/a ____________fiber or it can generate ____________at the terminal | voltage gated channels, afferent sensory, AP |
| dull sensation of pain after a cut is due to ___________ | c fiber |
| some sensory receptors can adapt if sensory exposure is________________that is termed ________________ | prolonged, sensory adaptation |
| there are two degrees of receptor adaptation what are they? how do they work? | tonic and phasic. Tonic receptors either don't adapt or adapt slowly. Phasic receptors adapt rapidly and function to convey info about changes in stimulus intensity |
| what receptor informs of glasses being put on? | phasic, adapts slowly |
| vertebrate eye is covered by an outerwall that consists of how many layers? what are they? | 3 layers. From outside to inside it is: 1. outer: fibrous layer or tunic 2. middle: vascular or uvea 3. inner: retina |
| tunic is divided into two regions ___________ and ______________ that have distinct _____________origin | sclera, cornea, embryological |
| what is the sclera made up of? where is it found? | made up of white fibrous connective tissue. Found in the posterior region of the eye (back 2/3 of eye) |
| the sclera is derived from the ____________ | mesoderm |
| what part of the eye withstands intraocular pressure? | the sclera |
| the _____________ receives extrinsic eye muscle insertions | sclera |
| the optic nerve enters the posterior ____________ | sclera |
| what gives shape to the eyeball and protects inner part? | sclera |
| T/F: the cornea is white fibrous layer | FALSE. it is transparent |
| what does the cornea provide? | interface between the environment and the internal structures of the eye |
| the cornea is derived from ______________ | skin ectoderm |
| how does the cornea provide protection from external environment in terrestrial organisms? | it protects from dust by maintaining a moist surface, lacrimal glands provide fluid source, and eyelashes in mammals trap particles. In reptiles, there is nictitating membrane |
| what is meant by nictitating membrane ? | a membrane that flicks laterally (left-right) across the eye |
| what does the outer layer of the cornea consist of? | epithelial cell layer that is continuous with epithelial cells of the conjunctiva |
| what is the conjunctiva? | clear, epithelial cell layer that covers the sclera, also lines eyelids |
| conjunctiva lines the __________ as well as cover the ____________ | eyelids, sclera |
| functions of the conjunctiva? | mediates immune response, associated with mucus production- conjunctivitis (pink eye) is inflammation of conjunctiva |
| what is the scientific name for pink eye? what is it? | conjunctivitis. pink eye is inflammation of the conjunctiva which lines the eyelids and covers the sclera |
| what provides light reflection in vertebrates? | cornea |
| what happens if the light hits the surface of another medium that is perpendicular to the light rays? | rays remain parallel but slow down, if density of medium is thicker than air |
| what happens if the light hits an angulated surface ? | some rays reach surface before others, the rays will bend perpendicular to the angle of the surface. and slow down if density of medium is thicker than air |
| what speed do light rays strike the surface of the medium at? | speed of light 186,000 mi/s |
| what is meant by refractive index? | the ratio of light velocity in vacuum versus light velocity in a given medium |
| velocity decreases in any medium, but what does that depend on? | nature of medium and wavelength of light |
| how does the refractive index of a terrestrial vertebrate's cornea compare to the air's? | there is a marked difference in refractive index of cornea relative to air |
| cornea in terrestrial vertebrates is what shape? does that help or deter light refraction? | it is curved which will help slow and bend light rays, cornea provides 2/3 light refraction in terrestrial vertebrates. |
| how is water different from air? | 1. dissolved suspended material block light limiting vision 2. light intensity goes down as depth increases wavelengths selectively absorbed @ lower depths 3. refractive index of water is similar to the cornea's |
| what is the order of wavelengths of light disappearing as you go deeper in water? | first UV, red, orange, yellow, green, last blue |
| why is the cornea not important (has a minor role ) in light refraction in aquatic vertebrates? | because refractive index of the cornea is similar to the refractive index of water |
| why is the cornea flat? | to decrease resistance to movement in water |
| what refracts light in aquatic vertebrates? | large, spherical lens |
| what is the uvea composed of? | vascular layer composed of 3 regions: the choroid layer, the ciliary body, and the iris |
| what is the choroid layer? what does it line? | thin, dark brown membrane that lines surface of the sclera |
| what is the function of the choroid layer in diurnal vertebrates? | absorbs light and prevents refraction back out the eye |
| what is the function of the choroid layer in nocturnal vertebrates? | improve light detection; tapetum lucidum |
| light reflects off of deer's _____________________ when headlights point towards the deer | tapetum lucidum |
| what provides vascular supply for the retina? | the choroid layer |
| what is the ciliary body? | vascular tunic that contains ciliary muscle |
| what is the function of the ciliary muscle? | alter lens shape so lens can fine focus |
| where is the iris located? | between the lens and cornea |
| the iris is located between the ____________ and the _________________ it is connected to the __________________ | lens, cornea, ciliary body |
| the center opening of the iris forms the _____________ which allows ___________ | pupil, light to enter the eye |
| how does light enter the eye? how is the amount regulated? | through the pupil. the iris regulate the amount of light entering the eye by regulating pupillary aperture |
| how is pupillary aperture achieved? | iris does it by using 2 types of muscles; radial and circular |
| pupils constricting is controlled by the _____________ system it uses _______ muscles in the iris. It uses NT(s) ________ | parasympathetic, smooth circular, acetylcholine |
| what causes pupils to constrict? | bright conditions, to limit light entering into aperture |
| pupils dilating is controlled by the _____________ system it uses _______ muscles in the iris. It uses NT(s) ________ | sympathetic, smooth radial, epinephrine/norepinephrine (fight flight,flee-dilate) |
| what causes pupils to dilate? | dark conditions, to enhance light gathering capability |
| how many layers does the retina contain? what are their features? | 2 layers, outer layer is pigmented and non neurons, inner contains 2 zones of neurons |
| retina contains photoreceptors ____________ and _____________ | cones, rods |
| each photopigment consists of a protein called _______ and a chromophobe called ____________ | opsin, retinene |
| which part of a photopigment differs for the four pigments? | opsin |
| what is rhodopsin? | opsin found in rods that is sensitive to light/dark |
| what pigments can cones have? for what colors? | 1. erythrolabe-red range 2. chlorolabe-green range 3. cyanolabe-blue range |
| what are the components of the neuronal layer of the retina? | bipolar neurons, amacrine cells, horizontal cells, ganglion cells, optic disc, fovea |
| what pathway are bipolar neurons? | vertical pathway |
| what neurons transport input from the photosensitive cells to ganglion cells? | bipolar neurons |
| what cels shape the image by exciting or inhibiting adjacent cells? | amacrine. inhibit/excite amacrine and bipolar |
| what pathway are amacrine cells? | horizontal pathway |
| what pathway are horizontal cells? | lateral pathway |
| what is the function of horizontal cells? | contact other horizontal or bipolar cells |
| what cells receive net response and if excited, generate AP to CNS? | Ganglion cells |
| what forms the optic nerve? | axons of ganglion cells |
| retina is often thought of as an ___________ | extension of the brain-optic nerve is axon ganglion |
| the light hits ____________ and ____________ before ever reaching the photoreceptors | ganglion cells, bipolar cells |
| what is the region where the optic nerve exits the retina? | optic disc |
| optic disc is also termed __________ due to absence of ___________ and ____________ | blind spot, rods, cones |
| what happens to the image at the blind spot? | brain fills in the info due to the spot being devoid of rods and cones |
| what is the region of the retina that is devoid of rod but highly packed with cones? | fovea |
| blood in the fovea is displaced to one side, why so? | so light can hit cones |
| T/F: fovea is a region of low visual acuity due to less rods. | FALSE. it is a region of high visual acuity |
| some species lack a fovea, they have a _______________ instead | visual streak |
| what is a visual streak? in what animals is it found? | contains cones and ganglion cells, provides visual acuity over horizon, found in dogs, wolves |
| the lens lie just behind the__________ and the_____________ | iris, pupil |
| what is the lens made up of? | layers of transparent protein |
| what is the lens held in place by? | suspensory ligaments called zonal fibers |
| lens function to _____ and _______ light on the ___________ | retract, focus, retina |
| focal point is point where light _______ | converges |
| what is focal length? | distance from lens to focal point in meters |
| what is diopter? | reciprocal of focal length |
| lens separate the ___________ and ____________ | anterior cavity, posterior cavity |
| which chamber of the eye contains aqueous humor? | anterior cavity |
| what is aqueous humor? | fluid similar to CSF even in function |
| aqueous humor flows through anterior chamber out through ______________ circulation system | venous |
| _________________ humor is continuously produced unlike _______________ humor | aqueous, vitreous |
| what fluid in the eye aids in producing intra-ocular pressure? | aqueous humor |
| what fluid in the eye functions in waste removal? | aqueous humor |
| what fluid in the eye functions in maintaining eye shape? | vitreous humor |
| which chamber of the eye contains vitreous humor? | posterior chamber |
| the jelly like fluid in the posterior cavity is _________________ | vitreous humor |
| what lens is used to correct myopia ? | concave lens |
| focal point is formed ______________ to retina in myopia, in hyperopia it is formed ______________ to retina | anterior(infront), posterior (behind) |
| myopia is ________ sightedness while hyperopia is ___________ sightedness | short, far |
| what lens is used to correct hyperopia? | convex lens |
| what causes presbyopia? | loss of elasticity of the lens as a person ages |
| what is used to correct presbyopia? | bifocals |
| what is the primary mechanism for fine image detection in mammals? what stimulates that response? what is it induced by? | altering shape of the lens. it happens in response to blurred images, it is induced by smooth muscle contraction ~0.5 secs |
| What is altering shape of lens in response to blurry images in reptiles and birds induced by? | it's much faster than humans, induced by striated muscles |
| for near images, we __________ lens curvature, to _________ refraction power of the lens | increase, increase |
| lens is ___________ when we try to look far ahead | flat |
| when the ciliary muscle is relaxed, _________________ stretch the lens. the shape of the lens then is _________- | zonal fibers, flat |
| for close vision, ciliary muscle contracts, pulling the ___________ and _____________ towards the ___________ that releases tension on zonal fibers | choroid, ciliary body, cornea |
| what is the primary mechanism for light refraction in aquatic vertebrates? | large spherical lens |
| focus in aquatic vertebrates depends on ___________, they have _________________ which moves lens backwards and forwards. This is similar to how a camera works to get clear image | lens position, retractor muscle |
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