Midterm Study Guide

9 Pages

Biological Basis of Behavior
Course Code
BIBB 109
Felicity Paxon

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Exam 2: Answer key 1) State TRUE or FALSE for the following. If FALSE, write a sentence with the correct answer (5 points) a) The layer of photoreceptors, bipolar cells and ganglion cells is uniform throughout the retina, even in areas of high visual acuity. False, in the fovea light hits photoreceptors directly because the layer of bipolar and ganglion cells is thinner. b) Photoreceptors are absent from the optic disk, but are abundant in the fovea True c) Glutamate activates ON bipolar cells by binding to AMPA receptors in the light False. Photoreceptors release GLU in the dark and ON bipolar cells are activated in the light when GLU does not bind to mGLU keeping K+ channels closed. d) A one-to-one connection exists between photoreceptors and bipolar cells in all areas except the fovea False: One to one connections are only present in the fovea e) The mechanism of dark adaptation is produced by pupil dilation and increased concentration of Ca. True 2) Complete the following table comparing Rods and Cones using the following terms: High, Low (8 points) Rods Cones Total number High Low Total number in fovea Low High Ability to distinguish two Low High nearby points Photoreceptor/Ganglion ratio High Low 3) Determine the appropriate response for each of the following scenarios (6 points): a. Which cells synapse on layer one of the left LGN i. P ganglion cells of the right eye ii. P ganglion cells of the left eye iii. NonM-NonP cells of the left eye iv. M ganglion cells of the right eye v. M ganglion cells of the left eye b. Which of the following statements is correct about blob cells in V1? Select all that apply i. The cells are binocular ii. The cells are monocular iii. The cells are direction and orientation selective iv. The cells display color opponency v. Blob cells have circular (center/surround) receptive fields 4) For the following cases, describe which component of the visual system is likely to be damaged (9 points) a) An elderly woman complains of headaches, nausea, and worsening peripheral vision in both of her eyes. Her neurologist suspects a brain tumor compressing which region of the visual system? Explain your reasoning with a sentence. Optic chiasm...this is the point where the crossing fibers from the nasal retina of each eye could be damaged, leading to loss of peripheral vision. b) Upon careful examination of the patient, the neurologist finds out that her peripheral vision is ONLY poor in her left eye. The ophthalmologist also suspects that her problem is happening at the level of the retina? What eye and portion of the retina may have been damaged in this patient? Nasal retina, left eye (ipsilateral) c) After checking the retina the ophtalmologist concludes that he was wrong because the cells in the eye are healthy. What might be his next suspicion to explain the woman’s lack of peripheral vision in the left eye? Left optic nerve is damaged causing the loss of the peripheral vision on the left side. 5) Which of the following stimuli will show A) the greatest and B) the lowest response in a G+/R- P-type ganglion cell? Explain your answer in EACH case. (7 points) i. completely green circle ii. a completely red circle iii. a green center and red surround iv. a red center and white surround v. a green center and white surround A) Greatest Response:________________ (v) Since green and red have significant overlap in their wavelengths, any green in the surround will negatively activate the surround (R-) and inhibit the center from firing. B) Lowest Response__________________ (ii) Although there is some green in the red center, this is not the optimal stimulus for the center and, in addition, it will be inhibited by the red surround. 6) In your rush to get to your BBB109 lecture the other day you banged your elbow against your bedroom door. (8 points, 2 points each) a. You feel an initial sharp pain right after you hit the door, then a longer lasting dull ache as you walk down the hall. What nerve fibers carry each feeling (sharp pain vs. long lasting ache)? Sharp = A gamma fibers & Long = C fibers b. You find that a larger portion of your arm hurts than the small part of your elbow that hit the door. What is the name of this phenomenon and what produces it? (in your answer include at least 2 chemicals that lead to this process) Hyperalgesia. This is produced by the swelling of neighboring tissue and hyperexcitability of nocicetors due to the diffusion of chemicals such as bradykinin, Substance P and prostaglandins c. Which of the following ions or chemicals activate nociceptors? Circle ALL that apply: i. potassium ii.histamine iii. calcium iv. ATP v.Adrenaline vi. blood accumulation d. You realize you’re gently rubbing your elbow and it’s helping to ease the pain. What is happening in the afferent axon to regulate your elbow pain? The activation of touch mechanoreceptors by your rubbing sends an additional signal along the afferent axon that activates an interneuron in the dorsal horn. The interneuron inhibits the firing of a projection neuron that was activated by pain signals. This reduces the sensation of pain. 7) The plot below shows how the membrane potential of a hair cell changes in the presence of a sound stimulus. (8 points) i.Point to where receptor ion channels are i) opened, ii) closed and iii) at rest Vm ^Stimulus Onset Time ( i. peak, ii. trough, iii. dotted line) ii. The peak of the receptor depolarization coincides with which of the following? a. Trough of the sound wave and trough of the basilar membrane wave b. Peak of the sound wave and trough of the basilar membrane wave c. Trough of the sound wave and peak of the basilar membrane wave d. Peak of sound wave and peak of the basilar membrane wave iii. In one sentence, describe the ionic conditions that enable hair cells depolarization through this channel. The endolymph bathing stereocilia has a higher K+ concentration
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