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89 Cards in this Set
- Front
- Back
Which color has the shortest wavelength? The longest?
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Blue, around 400. Red, around 750.
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What are some of the main parts of the eye?
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Retina, Fovea, Optic Nerve, Cornea, Pupil, Lens
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The Retina
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Lines the back of the eye
Light is converted to neural signals to be sent to the brain. 3 layers - photoreceptor layer, bipolar cell layer, ganglion cell layer |
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Retinal Pigment Epithelium
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These pigmented cells form a layer behind the retina.
Stops light from bouncing back out/ being reflected Some animals have a more reflective layer to see better in the dark |
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What are the 3 layers of the retina?
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1) Photoreceptor Layer
2) Bipolar Cell Layer 3) Ganglion Cell Layer |
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Photoreceptor Layer
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Contains photoreceptors, rods, cones
By the back of the eye |
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Bipolar Cell Layer
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Contains Bipolar Cells
Connects photoreceptors to the third layer The horizontal cells are like an octopus reaching across multiple photoreceptors |
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Ganglion Cell Layer
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Contains ganglion cells
Sends axons to the brain - Form optic nerve Light comes into the ganglion layer and is sent back |
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Optic Disk
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Blind spot
No photoreceptors, just axons |
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Optic Nerve
AKA Cranial Nerve |
Very back of eye, where info is sent
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Cornea
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Light bends here
(Coming in from the top goes to the bottom back) |
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Rods and Cones
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Photo pigments are in the outer segments of the rod
Sensitive to light Transmitters released from base of rods |
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Cones
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Most prevalent in central retina, found in fovea
Sensitive to moderate to high levels of light Provide info about hue Provide excellent acuity |
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Rods
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Most prevalent in the peripheral retina, not found in the fovea
Sensitive to low levels of light Provide only monochromatic info Provide poor acuity |
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Fovea
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Central focus of vision (center of retina)
contains only cones, no rods central vision (all other is peripheral, where rods are) |
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Fovea
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The blind spot- 1 eye fills in the blind spot of the other
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Wavelength Examples
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Blue or short wavelength cones - almost 550
Rods - A little over 600 Green or medium wavelength cones - 650 Red or long wavelength cones - about 675 |
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Phototransduction
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Light is converted into electrical signals in the retina
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Phototransduction - Receptor Responses in Darkness
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1) photopigment phodopsin consists of retinal and opsin bound together
2) Retinal is in 11-cis form 3) Photoreceptor cell produces cGMP 4) cGMP causes sodium channels to open 5) Protoreceptor cell is depolarized 6) Increased release of glutamate (rod in depolarized state - glutamate released) |
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Phototransduction - Receptor Responses When Light is Absorbed
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1) Retinal absorbs a photon
2) Retinal changes to all-trans form. Rhodopsin molecule breaks apart 3) Enzymes are released, which break down cGMP 4) Sodium channels close (no cGMP) 5) Photoreceptor becomes hyperpolarized. (The more light absorbed, the more hyperpolarized) 6) Decreased release of glutamate |
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Graded Potentials - Action Potentials
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Photoreceptor - hyperpolarizing membrane potential
Bipolar Cell - depolarizing membrane potential Ganglion Cell (to the brain) - Recording of action potentials AP in 3rd step |
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Cones and Bipolar Cells
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On-Center/Off-Surround Receptive Field (when light hits the center, it turns on, hits the surrounding, turns off)
Light hits the cones and starts process of sending AP's Surrounding area of cones inhibit the gang. cells (send fewer AP's) |
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On- and Off-center ganglion cells
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When there's no illumination @ all, gang.'s continue to fire (still watching, waiting, alive)
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Mach bands - Hermann Grids
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When it looks like there is a darker line between two shades (when there isn't)
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Visual Processing Pathways
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Contains Suprachiasmatic Nucleus, Lateral Geniculate Nucleus, Superior Colliculus
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Suprachiasmatic Nucleus
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Circadian Rhythms
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Superior Colliculus
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Sensory- info
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Lateral Geniculate Nucleus (LGN)
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3 parts
1) Magnocellular Layer 2) Parvocellular Layer 3) Koniocellular Sublayer |
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Magnocellular Layer
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Transmits info from the rods
bigger cells two inner layers; form, movement, depth, and small differences in brightness |
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Parvocellular Layer
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Color info from cones
Smaller cells Four outer layers; color and fine details (red and green) |
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Koniocellular Layer
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sublayers between the magno. and parvo.
transmits info from short wavelength (blue) cones to the primary cortex |
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Occipital Lobe
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V1 = Primary visual cortex (layer 4)
V1 - V2 - segregated to different pathways V4 = Colors, Motion = MT V3 = Form (shapes, textures, edges) |
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Simple Cortical Cells
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Related to lines
Tested on monkeys |
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Complex Cortical Cells
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Larger receptive fields
No off regions Sensitive to movement |
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Ocular Dominance Columns
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Method = computer to control stimulus and record and process data from camera
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Orientation Columns
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Method = computer to produce different stimulus orientations and process data from camera
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Trichromacy Theory
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3 color processes account for all the colors we're able to distinguish
Red, blue & green are the primary colors |
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Young & Helmholtz
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From Trichromacy Theory, we have 3 types of photoreceptors
We have 3 types of cones Light of different wavelengths will stimulate these cones by different amounts The system must compare activity in all 3 to determine which wavelengths of light you're seeing |
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Opponent Process Theory
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Attempts to explain color vision in terms of opposing neural processes (& fill in gaps Trichromacy Theory leaves)
Includes afterimages & Complementary colors |
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Afterimage
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If we view colored stimuli for an extended period of time, we will see an afterimage in a complementary color
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Complementary Colors
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colors that cancel each other out to produce a neutral gray or white
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Hering (Opponent Process Theory)
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We have 2 types of color opponent cells:
red-green opponent cells blue-yellow opponent cells |
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Color Vision
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Today, based on Trichromatic & Opponent Process Theory
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Retinotopic Map
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in the visual cortex
adjacent retinal receptors activate adjacent cells in the visual cortex |
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Form Vision
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The detection of an object's boundaries and features (such as texture)
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What & Where Pathways
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Where = Dorsal stream
What = Ventral Stream |
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Parahippocampal Place Area (PPA)
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Strong category-selective region that responds to houses, landmarks, & indoor/outdoor scenes
Responds weakly to other types of stimuli, like faces, bodies, etc |
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Germ Layers
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Formed w/in the first week of contraception
3 layers: Ectoderm - Top layer (skin & nervous tissue) Mesoderm - Muscles, bones Endoderm - Bottom layer (internal organs) |
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Neural Tube
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Retained in mature brain as the ventricle system & central canal of spinal cord
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Neural Development
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Cell Proliferation
Migration (as cells divide, they migrate out) Differentiation (once they get to the right spot) Circuit Formation (Synaptogenesis) (Connections formed with near & far neighbors, Form synapses with other neurons) Neuron Death (Apoptosis) Rearrangement of connections (Circuit Pruning & refinement of synapses) |
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Cell Proliferation
(Neurogenesis) |
New cells born
Cells divide & multiply & multiply New neural cells formed in ventricular zone Symmetrical & Asymmetrical Division |
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Migration
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Once the daughter cell migrate from the progenitor
Neurons just work their way up the radial glia |
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Differentiation
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Daughter cells differentiate into neurons or glia
Neural Tube differentiate in 2 directions: 1) along the rostral-caudal axis 2) between the dorsal & ventral halves Many different genes & chemicals responsible |
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Circuit Formation
(Synaptogenesis) |
Start connecting to neighbors through use of growth cones
Growth cones respond to chemical & physical properties of the extracellular environment to reach their destinations - extend our in different directions, find a partner & influence other neurons to form a synapse) Once axons & dendrites are in place, both pre- & postsynaptic structures influence synaptic development The cell's major neurotransmitter is influenced by the postsynaptic neuron |
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Rearrangement of Connections
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Because so many & extra were formed
Those getting used are strengthened, while the others die away |
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Symmetrical Division
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lateral (getting bigger and farther away)
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Asymmetrical Division
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1 cell stays as a progenitor cell, the other becomes something in the nervous system
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Radial Glia
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Special glia with fibers that grow radially outward from the ventricular zone to the surface of the cortex
Provide guidance for neurons migrating outward during brain development Doesn't just push another up, it goes through the layer & forms a new one above it (so 6th formed first, then 5th...) @ any 1 time, a billion neurons working up the glia |
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Growth Cone
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Just sorta move & feel around
A molecule is released that attracts the growth cone Other release those that repulse the cone |
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Apoptosis
(Cell Death) |
Neurons compete for nerve growth factors, & those that fail to obtain this stimulus die
Caspases (synapses follow same thing, called pruning) |
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Caspases
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suicide/grim reaper
Exists in all neurons @ all times |
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NGF
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Nerve Growth Factor
Keeps neurons alive & happy |
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Visual Synapses
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Peak at 1 year of age
Pruning - NGF comes from postsynaptic side, send NGF back & sent up the terminal |
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Myelination
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Occurs from spinal cord rostrally towards the forebrain
Sensory systems myelinated before motor systems Most occurs early on, but continues till about 20 years old |
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Critical Windows
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Ability to rearrange synapses can only occur during this time (others can continue throughout lifespan)
Examples : Imprinting (ducklings) Vision (develop ability to see with both eyes & each aspect of vision involves competition) Language (even if learn a new one later, you'll never sound like a native) |
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Input organizes the LGN
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right and left eyes provide different inputs - start off as overlapping, but eventually are segregated
can put a patch on strong eye while young to improve the weak one |
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End of Critical Periods
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Multiple hypotheses:
axon growth ends synapses mature the presence of absence of neurotrophins influence plasticity |
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Aging Nervous System
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The human brain is considered mature at 20 yrs
Brain weight begins to decrease at 45 yrs People with college degrees have better preserved circuits (use it or lose it) |
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Alzheimer's
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Begins with mild memory loss, then progresses to loss of language, social skills and problem solving.
Eventually, it's fatal Typically doesn't occur until around 70 yrs APOE4 gene is correlated with it No current meds reverse it, but some can slow it down |
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Emotion
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•Emotions are subjective experiences that arise spontaneously and unconsciously in response to internal and external events.
•Emotions have different components: –Physical •Behavioral (facial expressions, body language) •Autonomic (rapid heartbeat, etc.) •Hormonal (adrenaline, stress hormones) –Cognitive - conscious experience or feeling –Valence (positive or negative) |
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Purpose of emotion
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•Arousal
•Approach/avoidance •Communication |
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James-Lange Theory
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specific pattern of autonomic arousal leads to specific emotions
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Biological Connection to Emotions
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The Autonomic Nervous System
–Flight or fight response –ANS produces different patterns of arousal during different emotional states based on valence |
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The Amygdala
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Imaging studies show more activity in the amygdala when viewing expressions of fear.
•Klüver-Bucy syndrome reduces fear. •Human damage to the amygdala produces difficulty identifying fear and anger. •The amygdala contains many benzodiazepine receptors. |
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The Cortex & Emotion
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•Hemisphere lateralization
for emotion –Left hemisphere damage results in depression –Dichotic listening tasks |
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Affective Blindsight
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–The ability of a person who cannot see objects in his or her blind field to accurately identify facial expressions of emotion while remaining unconscious of perceiving them; caused by damage to the visual cortex.
–The subcortical input (from the superior colliculus and the pulvinar, a large nucleus in the posterior thalamus) appears to provide the most important information for this task |
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Different Emotions Produce Patterns of Brain Activation
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Fear – amygdala; Disgust - insula
•Feeling excluded from a game produced activity in the cingulate gyrus, an area that responds to physical pain. |
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Types of Muscle
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•Smooth muscles:
•Digestive tract •Arteries •Reproductive system •Striated muscles: •Skeletal muscles •Cardiac muscles of the heart |
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Muscle Fibers
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•Sarcomere: single segment of a myofibril.
•Z line: boundary of each sarcomere. •Thin filaments are made of actin •Thick filaments are made of myosin |
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Muscle Fiber Contraction
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•In the resting muscle, troponin prevents interactions between actin and myosin.
•The arrival of an action potential leads to an internal release of calcium. •Calcium binds with troponin and allows actin and myosin to interact. •The myosin filaments slide past the actin filaments, shortening the sarcomeres and contracting the fiber. •Calcium is taken up again into internal organelles, troponin prevents actin and myosin interaction, and the fiber relaxes. |
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Muscles
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Can only contract
Additional muscles allow joints to rotate |
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Alpha Motor Neurons
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produce muscle contraction through their activity at the neuromuscular junction
The gray matter of the spinal cord is larger in segments serving the arms and legs due to large numbers of alpha motor neurons. |
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The Motor Unit
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consists of an alpha motor neuron and all the fibers it controls
•Size of a motor unit corresponds to its function. –Neurons serving slow twitch fibers have small cell bodies, innervate few fibers and produce little force. –Neurons serving fast twitch fibers have larger cell bodies, innervate more fibers and produce greater force. |
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Control of Muscle Contraction
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•A single action potential may be sufficient to produce contraction.
•Varying amounts of force may be supplied by: - varying the firing rate of alpha motor neurons. - recruitment (activating more motor units as more load is placed on a muscle). |
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Control of Alpha Motor Nuerons
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•Alpha motor neurons receive input from:
–Muscle spindles –Golgi tendon organs –Brainstem and motor cortex neurons –Spinal interneurons |
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Circadian Rhythm
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•Any rhythmic change that continues at close to a 24-hour cycle in the absence of 24-hour cues
–body temperature –cortisol secretion –sleep and wakefulness •In the absence of time cues, the cycle period will become somewhat longer than 24 hours |
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Zeitgebers
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environmental event that resets and entrains rhythm
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Biological Rhythms
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Rhythm, Time Frame, Example
Circadian, Daily, Sleep-wake cycle Ultradian, More than once a day, Eating Cycles Circannual, Yearly, Migration |
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Consequences of shift in clock
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•Shift work
–more accidents, psychological problems, less sleep •Jet Lag – phase delays easier than advances |