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outline 9

Comparative Physiology- Renner Lecture 9

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
Created by: rusulali97



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