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51 Cards in this Set
- Front
- Back
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Sensory-Motor Integration
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Knowledge of limbs in space/ position of hand/ visual info, etc. = sensory info-> spinal cord -> motor neurons send message to muscles of hand and forearm
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Sensation
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The stimulation of a sensory receptor and the generation of an action potential by the associated sensory afferent
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Perception
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The integration of sensory signals by the nervous system (really by the brain) into a representation of the world that can then be used to guide behavior
-> dependent on nature of sensory receptors |
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Stimulus localization
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the ability (or act) of determining where on the body an event happens
Cortical maps: in both the visual and touch systems, cells at all levels of the nervous system are arrange in an orderly, maplike manner -> reflects position and receptor density -more cells are allocated to the spatial representation of sensitive, densely, innervated sites like the lips or the center of the eye, than to sites that are less sensitive |
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Exteroception vs. Interoception
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Exteroception: localization to the external world, including the body surface
-> typically well localized, high resolution, and inaccessible to consciousness Interoception: localization of stimuli within the body -> poorly localized, low resolution, largely outside of consciousness |
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Receptors
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specialized cells which respond to a particular energy or substance (stimulus) which convert the stimulus to changes in membrane potential (to eventually APs)
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Transduction
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process by which the stimulus is converted to graded potentials
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Receptive fields
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the stimulus region and features that cause response of a sensory cell
(the region of the environment or stimulus quality that preferentially excites a neuron- alters its firing rate) -> 2 point discrimination (on palm = small receptive fields, arm = large receptive fields) -many small receptive fields give a high resolution representation of the environment -when a receptive field is stimulated, surrounding sensory fields are inhibited to sharpen sensation -receptive fields often overlap- they often converge on one secondary sensory neuron -if membrane is stretched, excited section and strong enough stimulus -> threshold and AP (due to Na+ influx) |
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Adaptation
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changes in sensory system activity that occur with repeated stimulation
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Labeled lines
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Dedicated neural pathways for different sensory modalities
-parallel, segregated neural pathways i.e. different lines signal sound, smell, touch, etc. Touch: Thalamus (VPL or VPM nucleus) -> Cortex (S1) Vision: Thalamus (LGN) -> cortex (V1) Hearing: Thalamus (MGN) -> cortex (BA 41/42) |
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Coding
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pattern of action potentials that represents a certain taste/smell/ stimulus
i.e. number and frequency, the rhythm in which clusters of APs occur, etc. Frequency coding = the frequency of APs is proportional to the intensity of the stimulus -neurons have a max firing Population coding = a stimulus is represented by a combination of frequency and receptor # *multiple receptor cells act in a parallel manner providing a broader range for coding the intensity of a stimulus* |
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Hapsis
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fine touch and discriminate touch
-Meissner's corpuscle (touch): fast-adapting, large receptive fields -Pacinian corpuscle (flutter, texture)- fast-responding and fast-adapting receptors -Ruffini corpuscle (vibration, strech)- slow-adapting -Merkel's receptor (steady skin indentation- finger over dot): slow adapting -Hair receptors (flutter or steady skin indentation) |
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Receptors
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-can be free nerve endings or nerve endings in sheath (connective tissue)
-> gated by pressure, chemicals, stretching, require ion channel -Nocioception: free nerve endings for pain and temperature- small diameter-> slow conduction speed -Proprioception: muscle spindles- large diameter-> fast conduction speed |
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Spinothalamic Tract/ Dorsal Column
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Somatosensory Pathway:
Info comes in via APs along axons that enter the dorsal roots of the spinal cord- axons extend up dorsal column to medulla where synapse is made and crosses the midline of the brain and up to the thalamus which then send info to primary sensory cortex -crossing = decussation |
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Somatosensory homunculus
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represents the proportion of somatosensory cortex devoted to that region of the body
-i.e. many sensory receptors/ small receptive fields on hands, face -> topographical organization *sensory maps are plastic!*- can change w/ experience |
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Post-central gyrus
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primary somatosensory cortex in the parietal love
-incoming sensory info from the thalamus comes into layer 4 (6 layers to neocortex) -neocortex also has columns- which respond to similar stimuli |
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Pain (Event-related vs. State-related)
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-multidimensional phenomenon: sensory and motivational/emotional aspects
Event-related: short-lasting, causes immediate withdrawl of effect, "sharp, bright pain" State-related: long-lasting, promote behaviors conducive to rest and recovery, "slow, burning pain"-i.e. throbbing |
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Temperature
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-slow burning pain: transient receptor proteins (TRP1), cation channels -> leads to depolarization, capsaicin-sensitive stimulates perception of thermal heat
-Fast sharp burning pain: TRP2, capsacin-insensitive, travel on fast Adelta myleinated fibers -Coolness: activity at low temps, menthol-sensitive |
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Chemical Pain
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-release of peptide- called substance P
-release of histamines -> promotes swelling -release of serotonin, prostaglandins, etc. -enters dorsal root of spinal cord and crosses immediately (contralateral), different from sensory-which travel ipsalaterally and cross in brain stem |
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Neural pathways for pain
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-pain perception depends on neural processing in the frontal cortex, esp. the cingulate gyrus -> also, the emotional aspect of pain
-somatosensory cortex- localization of pain to a body region Top-down component: -modulation of the pain signal = pain gating -descending pain modulation pathways: periaqueductal in midbrain -> raphe nucleus in medulla -> spinal cord + 5-HT releasing neuron -pain killers can gate pain signals -fine touch and pressure pathway from body receptors can gate pain pathways |
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Referred Pain
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Visceral pain:
-travels through the vagus nerve -internal organs have pain receptors, but no "high resolution" pathway of their own -> they synapse on fibers used by cutaneous pain receptors -> perceive pain on the surface of your body- i.e. heart attack feel pain on left arm and neck |
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Hapsis vs. Proprioception vs. Nociception
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Hapsis and Proprioception:
-Signal in through dorsal root and out dorsal column -Large diameter and myleinated = fast transmission -Sent to primary somatosensory cortex Nociception: -signals damage to body -many unmyleinated-slower transmission -signals in through dorsal root through anterior lateral tract and up dorsal column -sent to primary somatosensory cortex and cingulate gyrus of frontal lobe BOTH have receptors in skin and sends info to the spinal cord (sometimes brain stem) and the BOTH rely on APs |
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Chemical Senses
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-evolutionarily speaking- our oldest senses
-taste and smell indicate palatability of food and their nutritive value smell->also degree of kinship and readiness to mate -odorants and tastants = molecules which have to dissolve in a fluid and bind to receptors |
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Taste
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1. Bitter- signals toxicity
2. Sweet- signifies calories 3. Sour- ionic balance/ osmotic regulation, acidity/bascity- pH regulation, can also signify danger- too much acid in environment 4. Salty- Na+ for neural signals and water balance 5. Savory (umami)- responds to protein rich food (MSG) -Bitter/Sweet/Savory = metabotropic receptors -Pathway = taste receptor cells -> cranial nerves -> synapses in brain stem and thalamus to taste zone of cortex = labeled line signaling! |
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Smell
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-Olfactory mucosa has olfactory receptor cells that send signal to olfactory bulb/ mitral cells to cortex
Two pathways: 1. Olfactory bulb -> amygdala -> hypothalamus -> lateral posterior orbitofrontal cortex 2. Olfactory bulb -> prepyriform cortex (medial temporal lobe, primary olfactory cortex) -> medial dorsal thalamus -> orbitofrontal cortex (secondary olfactory cortex *pathway also b/w amgydala and medial dorsal and prepyriform and hypothal *smell is the only sensory modality than can synapse directly in the cortex rather than having to pass through the thalamus* |
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Vomeronasal system
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-vomeronasal organ
-close to olfactory tract, but separate system- not exactly sense of smell -detects a class of chemicals called pheromones (chemicals that signal degree of kinship and reproductive status (lap dancers) -> sends electrical signals to the accessory olfactory bulb in the brain (adjacent to the main olfactory bulb) which projects to the medial amygdala and in turn projects to the hypothalamus -> also new discovery of a class of olfactory receptors within the main olfactory epithelium that respond to pheromones instead of odorants |
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Retina
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transduction surface of the eye (contains photoreceptors)
Composed of multiple layers: -rod and cone cell layer: release neurotransmitters molecules that control the activity of bipolar cells that synapse with them. The bipolar cells in turn, connect with ganglion cells. The axons of ganglion cells form the optic nerve, which carries information to the brain -Fovea = central portion of the retina, packed with the most photoreceptors and therefore the center of our gaze -Blind spot (optic disk) = the place through which blood vessels enter the retina. Because there are no receptors in this region, light striking it cannot be seen |
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Cones vs. Rods
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Cones:
-~4 million, small receptive fields, clustered in a small area of the retina, require high intensity stimuli, 3-4 types, sparsely networked, sensitive to different wave lengths of light *responsive to bright light and responsible for color vision and our ability to see fine detail* =photopic system (operates at high levels of light and detailed neural processing, sensitivity to color, and involves cones) Rods: -~100 million, large receptive fields, highly networked, very sensitive to intensity but not sensitive to wavelength (color) *more numerous than cones and are more sensitive to dim light* -> mainly used for night vision = scotopic system (works in dim light, involves rods and highly convergent neural processing) At night... -cones not active so counterproductive to "foveate" (send light to fovea which is packed w/ cone cells)- better to look towards the side where the rods are |
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lateral inhibition
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The phenomenon by which interconnected neurons inhibit their neighbors (adjacent receptive fields), producing contrast at the edges of regions and sharpens a signal
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Outer segments of rod
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-contains photosensitive molecules
-stimulation by light leads to hyperpolarization! Allows visual system to be: -very sensitive -temporarily integrate signals -adapt to changes in stimulus intensity -release glutamate but it is a graded release -> glutamate may or may not depolarize a bipolar cell (depends on receptor type)- glutamate always depolarizes ganglion cells (which fire APs) |
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Visual Pathways
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1. Geniculostriate path: after the optic chiams, most visual info is sent to the lateral geniculate nucleus (thalamus) -> striate cortex (primary visual cortex) -> other visual cortical areas
*color sensitive, high resolution, and very accessible to consciousness* 2. Tectopulvinar system: optic chiams -> superior colliculus (part of midbrain/tectum) -> pulvinar (thalamus) -> other visual cortical areas (usually V2) *bypasses primary visual cortex!, low acuity, color insensitive (gray scale), minimally available to consiousness 3. Retinohypothalamic path: retina -> hypothalamus -circadian rhythms (sleep/ wake cycle) -not accessible to consiousness in the occipital lobe- V1-> V2 -> V3 ("dynamic form") or V4 (color and form processing) or V5 (motor processing) |
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Geniculostriate Pathways
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Parvocellular:
-layers 3-6, small cells, small receptive fields, sensitive to wavelength and less sensitive to motion Magnocellular: -layers 1+2, large cells, large receptive fields, less sensitive to wavelength and more sensitive to motion *info from both eyes comes together in the lateral geniculate nucleus* -layer 1,4,6 - contralateral eye -layers 2,3,5,- ipsalateral eye |
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Visual System Receptive Fields
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-receptive fields of retinal ganglion cells (in the LGN) are concentric
-2 types: on-center/off-surround (spot of light in center = increased firing, spot of light in surround = decreased firing) and off-center/on-surround (opposite)-> the center and its surround are always antagonistic which explains why uniform illumination of the visual field is less effective in activating a ganglion cell than is a well placed spot/ line/ edge passing through the center of the cell's receptive field *bipolar cells -> changes in polarization, ganglion cells -> APs -Cortical cells show sensitivity to orientation- i.e. cell responds strongly when stimulus is a vertical stripe -cortical cells also show sensitivity to direction of motion- i.e. cell responds strongly when stimulus moves down |
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Spatial-frequency filter model
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A model of pattern analysis in terms of lines and edges at various orientations
-i.e. twice as many bars in the same horizontal space = double the spatial frequency -applies Fourier analysis- determine which combination of waves needed to make any particular complex waveform -the visual system includes many channels tuned to different spatial frequencies -> cortical cells respond to spatial frequency grids |
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Theories of Color Vision
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1. Trichromatic Theory
- 3 photopigments color vision is based on: red, green, blue -3 major wavelengths that cones respond/are sensitive to 2. Opponent process -we need to account for yellow -4 hues: red, blue, green, and yellow exist as opposed pairs (red-green, blue-yellow, black-white) -psychologists demonstrated this by staring at one color and then looking at a white screen - these opposing pairs are produced by combination of short, medium, and long wavelengths with different types of cone sensitive to these wavelengths i.e. red = +M/-L (excited by medium. inhib. by long) green = +L/-M |
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Color Vision Pathway
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1. Cones receive visual information
2. This information is processed by neurons in the local circuits of the retina, leading to retinal ganglion cells that are excited by light of some wavelengths and inhibited by light of other wavelengths -ganglion cells send wavelength info to the LGN, mainly in the parvocellular layers -> V1 where it is relayed to other visual cortical areas |
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Dorsal vs. Ventral stream
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Dorsal stream = visual info used to locate objects in space and to guide movements ("where" and "how" stream)- heading to the parietal lobe
-V5 (motion), and V3A (form) Ventral stream = visual info used for object and color naming and object recognition ("what" stream) - heading to temporal lobe (memory) -includes V4 (perceives color), FFA (fusiform face region- recognizes faces), V3 (dynamic form) *both originate in V1* i.e. carbon monoxide posioning-> visual form agnosia- no knowledge of visual forms = problems w/ ventral stream |
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Pyramidal (Corticospinal) System
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-major output pathway for voluntary control of muscles- neurons are in layer V of the primary motor cortex and their axons, which pass through the brain stem, forming the pyramidal tract to the spinal cord
-Crosses the midline in the brainstem (decussation) and innervates contralateral spinal motor neurons: medial muscle groups located near midline and lateral muscle groups more distal from midline |
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Primary Motor Cortex (M1)
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-corticospinal tract originates here and the neurons project to the spinal cord
-executive region for the initiation of movement (activating muscle groups); primarily the precentral gyrus *large areas of M1 devoted to face/hands (due to motor homunculus) |
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Secondary (nonprimary) motor cortex
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-sequencing the movement needed to carry out plans (from prefrontal cortex)
4 Regions: -Supplementary Motor Area (SMA): very important for generating voluntary self-cued actions -Premotor area (PMA): balance and gait -Frontal Eye Field (FEF): important for visual attention and making visual saccades to targets of interest -Broca's area: produce articulate speech *the first 2 are the main regions* |
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Prefrontal cortex
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-motor association area->strategies, action plans, goals
Subcortical areas: -Basal Ganglia- generation/regulation of the force of movement, initiation of movements, motor habit learning (procedural memory), open-loop systems, BG activity is coordinated with that of M1 -Cerebellum: balance, fine movements, rapid modification of movement pattern, coordination, classical conditioning -Substantia nigra (midbrain)- dopamine release |
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Open loop vs. Closed loop
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Open loop (basal ganglia and cerebellum)
-rely on preprogrammed or habitual actions, delayed feedback- error must be anticipated, ballistic, fast i.e. throwing Closed Loop (prefrontal mediated actions): -relies on immediate external feedback, "real time", slower, but highly accurate i.e. pointing |
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Extrapyramidal Systems
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-involuntary control of posture, stance, reflex action, balance, gait
-originate largely in different places (tracts outside of the pyramids of the medulla) and descend ipsalaterally -modulate spinal reflexes -communicates to the spinal cord through 2 principal pathways: the reticulospinal and rubrospinal tracts (basal ganglia and cerebellum send commands through these tracts) |
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Parkinson's vs. Huntington's
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Parkinson's = degeneration of the substania nigra-> thus have trouble initiating movement, have a resting tremor, rigidity to face and posture = hypokinesia (slow of movement)
-usually not inherited, treatment = L-dopa b/c it can cross the blood brain barrier- not cure, but reduces symptoms Huntington's = degeneration of the striatum (caudate nucleus and the putamen), leads to hyperkinesia = excessive, poorly controlled motion, also intellectual deterioration, depression, and motor problems (b/c striatum linked to prefrontal cortex) -transmitted via a single dominant gene w/ excessive trinucleotide repeats *both = degeneration of the basal ganglia |
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Sensory Motor Integration
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1. Visual info required to locate target
2. Frontal lobe motor areas plan the reach and command the movement 3. Spinal cord carries info to hand 4. Motor neurons carry message to muscles of the hand and forearm 5. Sensory receptors on the fingers send message to the sensory cortex saying that the cup has been grasped 6. Spinal cord carries sensory info to the brain 7. Basal ganglia judge grasp forces, and cerebellum corrects movement errors 8. Sensory cortex receives the message that the cup has been grasped |
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Homeostasis
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The tendency for the internal states of an organism to be maintained within a narrow range of conditions most conducive to survival
-regulatory functions = homeostatic functions that are crucial for the survival of the individual-i.e. thermoregulation, food/energy regulation, fluid regulation |
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Thermoregulation
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Euthermia = normal body temp (36.6-37)
Hypothermia = below, core temp <32 is life threatening Hyperthermia = above, core temp >40 is life threatening -heat is generated through metabolism Behavioral thermoregulatory responses: 1. changing exposure of the body surface (huddling) 2. changing external insulation (clothing) 3. selecting a surrounding that is less thermally stressful (shade) Afferents: skin surface, body core, hypothalamus -> Neural regions: spinal cord, brainstem, hypothalamus -> Effectors: Behavioral response = shivering, heat seeking/avoiding behaviors; Autonomic responses = vasoconstriction dilation, sweating, respiration, brown-fat stimulation, thyroid hormone secretion |
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Food and Energy Regulation
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-Energy (calories): carbs = 4kcal/g, proteins = 4 kcal/g, fats = 9kcal/g, EtOH = 7 kcal/g
-Nutrients: essential fatty acids and amino acids, micronutrients- vitamins and minerals -> produce structural elements (Na+/K+ pump), enzymes, neurotransmitters, etc. |
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Body Weight Regulation
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-basal metabolic rate changes in response to over and under nutrition- thus humans resist to either losing or gaining weight
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Blood Glucose
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-blood glucose levels are closely regulated
-glucose = principle sugar used by the body for energy and it is important for fueling the brain -insulin promotes glucose uptake and storage, glucagon promotes glucose release and consumption -Stimulation of insulin release 1. Sensory stimuli from food (sight, smell, taste) evoke a conditioned release of insulin in anticipation of glucose arrival in the blood = Cephalic phase b/c regulated by the brain 2. DIgestive phase = food entering the stomach and intestines cuases them to release gut hormones, some of which stimulate the pancreas to release insulin 3. Absorptive phase- glucose enters the bloodstream and cells in the liver signal insulin release from pancreas -circulating levels of insulin and glucose contribute to hunger and satiety- but there are many other factors -Central Glucose-sensitive neurons: in the lateral HT there are neurons that are sensitive to fluctuations in blood glucose levels -> ATP-sensitive K+ channel: high glucose levels-> high ATP levels -> block of K+ channel -> depolarize neuron -> NT release |
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Regulation of feeding behavior
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Arcuate nucleus of the HT contains a highly specialized appetite controller that is governed by circulating levels of a variety of hormones:insulin, leptin (release by fat cells- long term signal for inhibition of food consumption), ghrelin (released by cells in stomach lining to stimulate appetite), obestatin (release by the stomach lining to inhibit appetite), PYY3-36 (release by the intestines to inhibit appetite)
POMC/CART neuron- stimulated by leptin/insulin, release a-MSH in lateral HT which suppresses activity of lateral HT and inhibit appetite and increase metabolism -stimulated by leptin and insulin AgRP/NPY neuron: suppress inhibition of lateral HT and inhibits ventromedial HT which stimulates appetite and reduces metabolism -inhibited by leptin, insulin, and PYY3-36, and stimulated by ghrelin |
