Essay questions: Chapter 4,5,6

Question 1

Explain what the resting membrane potential is and the forces involved in maintaining it. Passive and Active

Answer 1

Membrane potential is electrical charge across a cell membrane; the difference in electrical potential inside and outside of the cell b. Resting potential is membrane potential of a neuron when it is not being altered by excitatory or inhibitory post synaptic potentials. Normally about -70mV. Resting in highest concentration has a +potassium and – protein inside, with + sodium and – chloride outside giving the neuron an overall negative charge inside. c. @ 50mv you get action potential k goes in active takes energy to pump it in and Na is the opposite and cl flows Passively

Question 1

Describe the different types of postsynaptic potentials. How might similar or different types of postsynaptic potentials interact to influence the likelihood of reaching the threshold of excitation and what are these “interactions” called?

Answer 1

EPSP – Excitatory Post Synaptic Potentiali. Neuron receives slight excitement change, increase likelihood of action potential, depolarize the cell b. IPSP – Inhibitory Post Synaptic Potentiali. Decreasing the likelihood of an action potential, hyperpolarizing the cell c. Spatial Sublimation i. Different locations that add together at the same time ii. When an EPSP and IPSP simultaneously happen together, there is no effect. iii. There must be multiple EPSPs fired at the same time to create enough depolarization to reach the threshold of excitation for an action potential. d. Temporal Sublimationi. Neurons get IPSP/EPSP and before it can die off, another IPSP/EPSP is received, having an additive effect (same neuron – one connection)

Question 1

Draw a diagram of an action potential. Label the axis and all of the various components of the curve and graph.

Answer 1

a. Resting b. EPSP (threshold of excitation) c. Action Potential d. Undershoot Phase e. Resting SEE STUDY GUIDE FOR GRAPH!!!!!!!!!!!!!!!!!!

Question 1

What is an action potential? Why is it important

Answer 1

a. Action Potential – brief electrical impulse that provides the basis for conduction of information along the axon IMPORTANT BC THAT’S HOW CELLS COMMUNICATE!

Question 1

Draw a diagram of a typical synapse. Label the anatomical components

Answer 1

SEE STUDY GUIDE FOR GRAPH!!!!!!!!!!!!!!!!!!

Question 1

Describe the basic structure and functions of ionotropic and metabotropic receptors. Specifically list the similarities and differences between these two types of receptors

Answer 1

a) Ionotropic are receptors that are associated with ligand-activated ions channels. - The neurotransmitter attach to the binding site which causes the ion channel to open. B)Metabotropic are receptors associated with signal proteins and G proteins. -In metabotropic receptors, the neurotransmitter binds with the receptors which activates the G protein and causes a subunit to break away and one of two things happens: > 1) subunit binds with ion channel and opens it causing the ions to enter into the cell producing a postsynaptic potential or >2) subunit activates an enzyme which produces second messenger and that goes to the nucleus and other parts of the cell or to the ion channels which opens allowing ions in that produce a postsynaptic potential. *** Both receptors result in a postsynaptic potential. Both cause EPSP or IPSP > Ionotropic receptors are extremely fast, very short acting and the effects might die off, requiring a lot to start an action potential. >Metabotropic receptors on the other hand are slower, longer lasting, can keep channel open for a longer time, great depolarization and more permanent/ long lasting.

Question 1

Explain the seven steps in neurotransmitter action.

Answer 1

1. Neurotransmitter molecules are synthesized from precursors under the influence of enzymes 2. Neurotransmitter molecules are stored in vesicles 3. Neurotransmitter molecules that leak from their vesicles are destroyed by enzymes 4. Action potentials cause vesicles to fuse with the presynaptic membrane and release their Neurotransmitter molecules into the synapse 5. Released Neurotransmitter molecules bind with autoreceptors and inhibit subsequent Neurotransmitter molecules release 6. Released Neurotransmitter molecules bind to postsynaptic receptors 7. Released Neurotransmitter molecules are deactivated by either reuptake or enzymatic degradation

Question 1

Describe what agonistic drugs do, in general. Explain the different way that an agonistic drug may affect neurotransmission.

Answer 1

1. Agonistic Drug – facilitate the effects of a neurotransmitter a. Drug increases the synthesis of Neurotransmitter molecules (increasing the amount of precursor) b. Drug increases the number of Neurotransmitter molecules by destroying degrading enzymes c. Drug increases the release of Neurotransmitter molecules from terminal buttons d. Drug binds to autoreceptors and blocks their inhibitory effect on Neurotransmitter release e. Drug binds to postsynaptic receptors and either activated them or increases the effect on them of Neurotransmitter f. Drug blocks the deactivation of Neurotransmitter molecules by blocking degradation or reuptake

Question 1

Describe the three different approaches to neuropsychological testing. Is one of these approaches more accepted than the others? Why or why not?

Answer 1

Single-Test Approach – designed to detect presence brain damage and to help differentiate between structural brain damage and psychological brain damage; unsuccessful because there was no single test that could be developed to that would be sensitive to all the varied and complex psychological symptoms that could potentially occur in a brain damaged patient. Standardized-Test-Battery Approach – similar to single test approach but another a set of test (battery) instead of one; only marginally successful because though it could discriminate between neurological and healthy patients, it was not as good with discriminating neurological and psychiatric patients. Customized – Test-Battery Approach – Most commonly used approach; wasn’t merely use to identify brain damage but to characterize the nature of the psychological deficits of each brain-damaged patient. This is the more used approach because it is customized to each person

Question 1

Describe EEG, intracellular unit recording, multiple-unit recording, extracellular unit recording and invasive EEG recording. What are the similarities and differences between these different elecrophysiological tests.

Answer 1

a. EEG – gross electrical activity in the brain b. intracellular unit recording – movement-by-movement record of the graded fluctuations in one neuron’s membrane potential (electrical stimulation) c. multiple-unit recording - picks up signals from many neurons membrane potentials are added together d. extracellular unit recording – provides record of the firing of a neuron but no information about the membrane potential (electrical stimulation) e. invasive EEG recording – large implanted electrodes (stainless steel)

Question 1

Describe the pathway through which light wave energy will travel going form the environment to the retina. Explain the role of each anatomical structure through which the light wave passes.

Answer 1

a. Environment Cornea  Iris Muscles  Lens sclera ciliary muscle  fovea  optic disc i. Cornea: 1. Plays role in bending lightwave and focusing images Goes over the color part of your eye and pupil Fluid under cornea keeps the cornea alive (bathes and provides nutrients) ii. Iris 1. Pigmented muscle 2. Creates the pupillary opening iii. Lens 1. Flips the image from our environment 2. Helps do focusing/Accommodation iv. Sclera 1. Outer white area of eye where nerves are 2. Really tough v. Choroid 1. Absorbs lightwaves vi. Ciliary Muscle vii. Fovea viii. Optic Disc b. High light pupils constrict i. When they are constricted, the image falling on each retina is sharper and there is a greater depth of focus (a greater range of depths are simultaneously kept in focus on the retinas) c. When the level of illumination is too dull, pupils dilate to allow more light in i. Sacrifices acuity and depth of focus

Question 1

Describe the cellular arrangement of the lateral geniculate nuclei with respect to the types of cells in each layer, the types of information those cells are associated with, and the eye from which information passes through each layer.

Answer 1

a. Lateral Geniculate Nuclei = Group of cell bodies within the thalamus that receive input from the retina and projects to the primary visual cortex. Relay station for visual information • Occipital lobe 1. Projection of information from LGN to occipital lobe (initial processing) b. All signals from the left visual field reach the right primary visual cortex 1. Either ipsilaterally, From the temporal hemiretina of the right eye 2. Contralateral Via the optic chiasm from the nasal hemiretina of the left eye c. Each lateral geniculate nucleus has 6 layers: • Each layer of each nucleus receives input from all parts of the contralateral visual field (nasal hemiretina) of one eye • Three layers receive input from one eye, and three from the other d. Magnocellular Layers • One of the 2 inner layers in dorsal LGN which transmits information necessary for the perception of form, movement, depth, and small differences in brightness e. Parvocellular Layer • One of the outer 4 layers of neurons in the dorsal LGN which transmit information necessary for perception of color and fine detail f. Optic Chiasm • Information from nasal hemiretina cross over, and information from temporal hemiretina cross over

Question 3

Describe the neuroanatomical pathway through which visual information passes beginning with the optic nerve and ending at the striate cortex.

Answer 3

visual field is crossed so info from right goes to left and visa versa, optic nerve to optic chiasm, to LGN to striate cortex ex: left eye sees left nasal and right temporal

Question 4

What is a mach band? How do contrast enhancement and lateral inhibition explain the presence of mach bands?

Answer 4

.a. Nonexistent stripes of brightness and darkness running adjacent to the edges of colors—they enhance the contrast at each edge and make the edge easier to see b. Contrast Enhancement • Every edge we look at is highlighted for us by the contrast-enhancing mechanisms of our nervous systems • If a single ommatidim (receptors in horseshoe crabs eyes) is illuminated, it fires at a rate that is proportional to the intensity of the light striking it; more intense lights produce more firing • When a receptor fires, it inhibits its neighbors via the lateral neural networks c. Lateral Inhibition • The inhibition of neighbors via the lateral neural networks after a neuron fires • Spreads laterally across the array of receptors

Question 5

Explain the seven steps in neurotransmitter action.

Answer 5

1. Neurotransmitter molecules are synthesized from precursors under the influence of enzymes 2. Neurotransmitter molecules are stored in vesicles 3. Neurotransmitter molecules that leak from their vesicles are destroyed by enzymes 4. Action potentials cause vesicles to fuse with the presynaptic membrane and release their Neurotransmitter molecules into the synapse 5. Released Neurotransmitter molecules bind with autoreceptors and inhibit subsequent Neurotransmitter molecules release 6. Released Neurotransmitter molecules bind to postsynaptic receptors 7. Released Neurotransmitter molecules are deactivated by either reuptake or enzymatic degradation

Question 6

7. What is the retina-geniculate-striate system? Describe the type of receptive fields found in the different parts of this system.

Answer 6

a. Retina-Geniculate-Striate System • The major visual pathway from each retina to the striate cortex via the lateral geniculate nuclei of the thalamus • lateral geniculate nuclei, and lower layer IV neurons, four commonalities were apparent: 1. At each level, the receptive fields in the foveal area of the retina were smaller than those at the periphery a. Consistent with the fact that the fovea mediates high acuity vision 2. All the neurons had receptive fields that were circular 3. All neurons were monocular (each neuron had a receptive field of one eye, but not the other) 4. Many neurons at each of three levels of the retina-geniculate-striate system had receptive fields that comprised an excitatory area and an inhibitory area separated by a circular boundary • Neuron responded with either an “on” or “off” firing when the light hit it. • On-Center Cells 1. Responds to lights shone in central region of their receptive fields with “on” firing and to lights shone in the periphery of their receptive fields with inhibition, followed by “off” firing when the light was turned off • Off-Center Cells 1. Respond with inhibition and “off” firing in response to lights in the center of their receptive fields and with “on” firing to lights in the periphery of their receptive fields. • These both respond best to contrast 1. Most effective way to influence the firing rate is to maximize the contrast between the center and the periphery of its receptive field by illuminating either the entire center or the neither surround, while leaving the other region completely dark b. Simple Cortical Cells • Have receptive fields that can be divided into antagonistic “on” and “off” regions and are thus unresponsive to diffuse light • All monocular • Best w/ bars of light in a dark field, dark bars in a light field, or single straight edges between dark and light areas • rectangular, rather than circular c. Complex Cortical Cells • More numerous than simple cells • Rectangular receptive fields, respond best to straight-line stimuli in a specific orientation, and are unresponsive to diffuse light • Differ from simple cortical cells in 3 ways: 1. Have larger receptive fields 2. Not possible to divide the receptive fields of complex cells into static “on” and “off” regions 3. Many complex cells are binocular • Ocular Dominance 1. Most of the binocular cells in monkeys respond more robustly to stimulation of one eye than they do to the same stimulation of the

Question 7

8. Compare and contrast the “where” versus “what” theory with the “control of behavior” versus “conscious perception” theory.

Answer 7

a. “Where” versus “What” • Ventral stream is involved in the perception of “where” objects are flows from the primary vision cortex to ventral prestriate cortex (visual patter recognition) • Dorsal stream is involved with “what” the objects are flows from primary vision cortex to dorsal perstriate cortex (visual spatial perception) • Vision is that damage to some areas of cortex may abolish certain aspects of vision while leaving others unaffected • Most convincing support for this theory has come from the comparison of the specific effects of damage to the dorsal and ventral streams • Patients with damage to the posterior parietal cortex often have difficulty reaching accurately for objects that they have no difficulty describing • Patients with damage to the inferotemporal cortex often have no difficulty reaching accurately for objects that they have difficulty describing b. “Control of behavior” versus “conscious perception” theory Dorsal = visual guided behaviors Ventral = conscious visual pattern • the function of the dorsal stream is to direct behavioral interactions with objects • the function of the ventral stream is to mediate the conscious perception of objects • suggests that patients with dorsal stream damage may do poorly on tests of location and movement because most tests of location and movement involved performance measures • patients with ventral stream damage may do poorly on tests of visual recognition because most tests of visual recognition involve verbal awareness (conscious) • Confirmation of its two primary assertions: 1. That some patients with bilateral lesions to the ventral stream have no conscious experience of seeing and yet are able to interact with objects under visual guidance 2. That some patients with bilateral lesions to the dorsal stream can consciously see objects but cannot interact with them under visual guidance

Question 8

Describe the equipment and procedures you would have to employ if you were to conduct a study in

Answer 8

a. Do a scan to create your own stereotaxic Atlas/map b. Find coordinates c. Anesthetic used d. Find Bregmae. Use apparatus to secure patient f. Follow coordinates made I. Anterior/posterior ii. Medial/lateral iii. Dorsal/ventralg. Create lesion h. Repeat on opposite side i. Remove apparatus and sew back together animals head Apparatus = head holder electrode holder ( dorsal ventral, lateral medial, posterior anterior) use a knob to move it the desired direction

Question 9

Describe the different techniques for imaging the human brain. Provide a list of the similarities and differences between these techniques. >MRI >CT >PET >MEG >TMS >EEG

Answer 9

a. CT Scan looks at density of the brain region general indicator of abnormalities I. X ray – two dimensional –“Slice ”ii. Lacking detail or clarity b.MRI the person lays still don’t move picture taken of brain. (much better picture quality) i. Radio waves and magnetic field ii. Extreme detail iii. Polarize the brain iv. Provide pictures c. PET provides an indication of which area of the brain responds more during certain activities (moving right hand) i. Radioactive tracer ii. Red/orange indicate more glucose/activity iii. Activity of the brain iv. Less detailed v. Inject radioactive substanced. Functional MRI person physically moving around, great pic quality and great detail i. Metabolic/chemical changesii. More detailed iii. Combines PET and Magnetocephalogram (MEG) Gives u an idea of the role of the particular area of the brain. Transcranial Magnetic Stimulation stops u from thinking clearly. ex if magnet is placed on frontal lobe speech will be impaired -not very specific Electroencephalogram (EEG) electrical brain potential recorded by placing electrodes on the scalp (don’t forget about evoke EEG, where they make u mad and then measure ur responses.

Question 11

Describe the procedures of immunocytochemistry and in situ hybridization. Compare and contrast these two procedures.

Answer 11

a. Immunocytochemistry i. Procedure for locating particular neuroproteins in the brain by labeling their antibodies with a dye or radioactive element and then exposing slices of brain tissue to the labeled antibodies b. Situ hybridization. Hybrid RNA strands with the base sequence complementary to the mRNA that directs the synthesis of the target neuroprotein are obtained ii. Hybrid RNA labeled with dye iii. Brain slices exposed to labeled hybrid RNA, bind to mRNA strands, making the location of neurons that release the target Both Use a dye to target something (neuro Proteins) expose labeled brain slices to a labeled ligand of molecule under investigation

Question 12

Explain the cellular arrangement of the retina and the role of each type of cell. Is the distribution of the photoreceptors across the retina uniform? Provide support for your answer.

Answer 12

a. Retina converts light to neural signals, conducts them toward the CNS, and participates in the processing of signals b. Fundamental Cell Structure of Retina • Receptors, horizontal cells, bipolar cells, amacrine cells, retinal ganglion cells • Amacrine and Horizontal Cells are specialized for lateral communication (communication across the major channels of sensory input) Retinal neurons communicate both chemically via synapses and electrically via gap junctions • Bipolar Cell Layers: Transmit from photo cell layers to ganglion cell layers • Ganglion cell layer Made up of ganglian cells Axons of ganglion cells come together and go out back of eye and form the optic nerve c 3 Layers • rod and cone cell layers • Photoreceptors Sensory cells able to turn lightwaves into neural impulses d. Fovea • Highly concentrated with neurons to help us see during the day • Image lands on the fovea • Indentation specialized for high acuity (seeing fine details) e. Surface interpolation: • Visual system extracts information about edges and from it infers the appearance of large surfaces f. Cones inner layer • Photopic vision:provided high-acuity colored perceptions of the world Only a few cones converge on each retinal ganglion cell to receive input from only a few cones • More in the temporal hemiretina g. Rods outer layer • Scotopic Vision 1. In dim illumination, there is not enough light to reliably excite the cones 2. Lacks both detail and color 3. The output of several hundred rods converge on a single retinal ganglion cell 4. When a retinal ganglion cell that receives input from hundreds of rods changes its firing, the brain has no way of knowing which portion of the rods contributed to the change • More in the nasal hemiretina h. Photopic Spectral Sensitivity Curve • Sensitivity of humans can be determined by having subjects judge the relative brightness of different wavelengths of light shone on the fove i. Visual Transduction—conversion of light to neural signals y the visual receptors Not uniform because the output level of several 100 rods converge on a single ganglian cell and only a few cones converge into a single ganglion cell

Question 13

If you were a neuropsychologist and had to select 2 specific neuropsychological tests to examine a patient who had sustained a severe head trauma, which ones would you select to administer and why?

Answer 13

1. I would select the customized -Test -Battery-Approach. because I can get a more accurate diagnoses for my patients because the test was customized to them ad it will be sensitive to all complex psychological symptoms. 2. Single -Test- Approach- because this test will help differentiate between structural brain damage and psychological brain damage

Question 14

Describe, in detail, the neurobiological process responsible for transduction in a rod. Include how a rod responds in the light, and how it responds in the dark.

Answer 14

a. Rhodopsin: • Red pigment extracted from rods • When exposed to intense light, it is bleached and loses its ability to absorb light • When exposed to dark, it regains both its redness and its light-absorbing capacity • Our sensitivity to absorb wavelengths in the dim light is a direct consequence from rhodopsin’s ability to absorb them b. Dark •1. Rhodopsin molecules are inactive 2. sodium channels are kept open  3. sodium ions flow into the rods, partially depolarizing them 4. rods continuously release glutamate c. Light 1. Rhodopsin molecules are active 2.Light bleaches rhodopsin molecule as a result, sodium channels close  3. sodium ions cannot enter rods, and as a result, the rods become hyperpolarized  4. glutamate release is reduced