Class Notes - Lecture 2-12 Sensory Systems PDF

Class Notes : Lecture 2-12 : sensory systems...

Class Notes : Lecture 2-12 : sensory systems ACTION POTENTIALS are the currency of the CNS. The body surface is orderly mapped in the CNS (preserved at every level · We need sensation for perception movement control , to maintain anousal , and intemal homeostasis SPMATOTOPIC ORGANIZATION regulate : , somatic sensory System MODALITY SUBMODALITY ↳encodes sensminfobtheskinsurfa j conveyedtobrana somatication not vs cold - Ability to feel > -. ↳ pain vs. pleasure light vs Strong pressure. · properties of sensations : intensity , duration location modality(quality) , , , sub-modalityfine touch , wanth heat , · 1 Somatic sensory afferents (Ax AB-dorsal AS C-antenateral) detect stimuli ,. on skin surface and convey somatosensory info to CNS via ↓ L action potentials. contain specialized endings that detect pressure vibration temp. Changes , , convergence Lateral Inhibition cell body (metabolism Divergence ~surface ~Cspi This isnonthers e r > complex # * J The neuron that Appropagates consciously perceives q RF's is strongly activated the - precision sensory - receptor afferent (many moving pats neaker neighbours to one info disibuted many - to many ↳ coptical layers dendries Amples : ancheanice of signal neuversdampena gnal · excites (t Dorsal column Medial Lemniscal - Pathway : SKINSURFACE Anterolateral Pathway : INSIDE THE BODY used for the touch + proprioception used for paint temperature & using skin to describe where you are ↳ providing homeostatic info about what andundt you can do so nemussys. is going on inside monitor can surroundings Ist order The : cell bodies of these neurons are Ist order : cell bodies in also located in the dorsal not dorsal not ganglia, ganglion. axons of 1st order ascend trally These neurons synapse immediately in the in the dorsal columns of the spinal dorsal hom of the spinal cord. - - - cord + synapse in medulla of brainslem. 2nd order These : neurons immediately cross Inorder : In the medulla , they synapse in the to the contralateral side ofthe spinal cord, primary s Afferents we n i : ↳ nucleus gracilis - input from legs loverbody + and ascend in the antenolateral (spinothalamic ↑ diameter FAST ↳ nucleus cuneates - input from arms-upper body Many rents : tract to the thalamus. + myelin : urm,macomm * enaosanesynapor 1) enters dorsal root ↓ diameter + myelin Slow : ~ muscle spindles 1) main branch O enters white matter , 1) Ax (proprioception) 1) AS (fast pain) lateral venival hom es free enters ↓ , white matter up to 2) AB (fnetouch) goes brain + N arm 2) CGbers (slowpain) C.. legs 2st 2nd from arms ist legs 2nd (medial:lega axons from ↳ no axons · myelin-very slow · , arms , * Ap must be fast to coordination * Ap transmits in fo to be enable quick These neurons cross to contralateral side and 3rd order In the UPL (ventual posterior lateral callous that an area : of body movements the medial lemniscus to the thalamus as end as is hur+in pain (can be slow) Nucleus) , neurons project be the primary Erdorder :TheseneunensarelocatedintheV mus somatosensory conex which is specific relay nuclei that projects to a the primary somatosensory contex. Acuity Precision, not sensitivity : sensory Transduction HIGH ACUITY ① LOW ACUITY many neurons each ↓ fewer total neunens ↳ , Transformation of sensory info fremextimal i small RF and small larger RF and gaps or internal environment into opening/closing inn gaps between RF's channels on receptor cells stretches ion channels depolarization starts here , ex : Indentation within specialized - - nur ofskin propagates do un afferent axon ending in skin surface to CNS ↑ Stimulus Intensity : & f of Ap · Pressure on the skin surface is encoded as action potentials 1 sensory afferents (paltem in + frequency of pressure < Ap bring + timing Diff structures (i special endings) enable diff axons to transduce diff somatic ShmulitoCNs submodality ·.. - eachlypefending extracts one (ribrator pressure pain temp) and takes its specific Labeled Line , and ignores other) pathway to cNs : , , , ↳ This occur no matter what stimulated it perception of labeled line will be stimulated , ↳ constant pressure : Merel Cells + Ruffiniendings - adapting IIIIIIIII perceived sensations (painfully hot ↳ vibration Meissner Pacinian corpuscles adapting midly 1 II heat channels -integrate paint : + - extract diff infodbt pain + temp sensing Free newve endings. · The brain puts from many labeled lines to determine relative activation to dictate an overall perception processing together inputs Combinatorial : ↑ AP Receptive fields specific physical areas can detect shmuli and fire a specific sensory neuner h -LAP · are where a sensory receptor ↳ characterized by... 1) Size : very small on fingertips (precision/acuity + sensitively) but larger on bases (d spatial resolution) 2) Density : Machilyareas : ↑ receptors leach i smaller RF) ex : hands + lips 3) Convergence : multiple sensory neuversi overlapping RFs converge on one Ind order neuron (Nacily + sensitivity to larger shmulic many labeled lines activated simultaneously by stimuli within overlapping RFs (cold rough surface · , * For any given receptive field the type of shmulus , that will activate it depends on the type of receptor (mechano; themo-, novic.) · Each receptoris connected to a labelled line ispecific to type of shmulus) , allowing brain t dishnguish diff. sensory modalities. and leads to bring of a specific sensory neuron.  S ·cema Spinal cord · 42 48 cm long -Icm in diameter in 31 segments + 31 peripheral nemes ·. , , 5 sacral ↓ has cenical enlargement (nerves from arms), I coclygeal spinal nenes Primarysom and lumbar (nerves from legs enlargement innervaled region of the ↳ Greymatter: sellbodiesdendies systems , , body Dematome : thm dorsal roots motor neurons ne project to sicetal Iswam) spindl cord has its own circuitry in addition to being highway for Dorsal sensory · a : transmitting sensory + motor action roots. circuitry forms central responsible for rhylic movements ↳ The intrinsic paltem generators , Veniral : MOTOR I walking , scratching , etc. ) - don't have to think abtit , braintums on spinal cord circuitry dictates activation sensory-motor 1) Sympathetic > - Sightorflight (output from spinal cord gray matter Hierarchy 1) Parasympathetic - rest and digest loutput from brain stem + sacral regions conduit for info. flow Damage... "no target ↓. To one side of the 1 spinal cord causes deficits in · ipsilateral Gne touch Bec SHORT · controlateral pain +lemp below level of lesion 4 Is target ↓ loss of ipsilateral. to Rthorauc cord ex : Damage Spinal fundamental : Snelouchin R foot but normal fine touch in controlateral (1. foot I rhythm + detalls - BUT... Loss Of paint temp in L foot but normal temp in R foot. paint. contained here Je depends what the reflex is , the context of enrenment a on your your Plexes e simplest , goal-directed movements brain decides + spindl cord carries it out involuntary coordingled patters of muscle contraction + relaxation entire circuity contained in spind/cord don't need brain to carry out , (1) one discrete shmulus can produce large contraction of many muscles sensory info from I pre-synap Neurongesto many post-synaptic neunes o :. (2) extent + force of contraction & stimulus Intensity (more hand a littlers lot on flame vs store (3) reflexes are regulated + modified from higher brain areas by descending inputs stretch reflex - > maintains body position and gives limbs the ability to stay in place given load change midbrain Brainstem & ↳most like brain) conduct for info flow between brain spinal cord relaystainstors supernor + interior · involved in complex behaviour + integration pons medullalike spinal cora home of cranial Colliculi Crision + auditors newes pathways, motor control and + ↓ home to some cranial metant structures : signals to nuclei 1 Medial lemniscus + critical pontomedullary function pons travel. relay of sensory signals from medulla - thalamus Midbrain ⑧ crossing contralaterally + forming Aber tract I am am Formed of dersal column by axons · · changes shape based on location in brain (nere tract is crowded by new structures legs · Gr ↓ · cerebral aqueduct spinothalamic present (notin ventricle) cranial Nerves I have nuclei which originate in brainstem SSSUS VMS M tract o Toss Cranial Nerve Pneumonic : 8572-6 10 00 Oum Cranidi NerveNumber Sensor ? MAJOR FUNCTION , 12 order FNC 1. Olfactory sensory O Ifaction (smell) 11 Optic sensory Vision SM some on. III Oculomotor motor Eye movements : 4 of 6 eye muscles eyelids pupillary constriction Saymy. , , IV. Trochlear motor Eye movements V. Trigeminal Both cutaneous + proprioceptive sensation in face + mouth ; innervales teeth + Muscles of mastication money VI motor Touch But. Abducens Eye movements (lateral rectus - > moves eyes laterally Both EndBMO VII. Facial Muscles of facial expression ; taste sensation from tongue VIII. Vestibulocochlea Sensory Hearing equilibrium IX Both from palate. Glossopharynged swallowing , sensations and back" of tengue Girls X Vagus Both Autonomic sensory + motor fe of body. Visceral sensations of pharynx + larynx motor : medial very Brains. X motor. Spinal Accessory Trapezius and stemocleidomastoid muscles Soft Matter motor XII. Hypoglossal muscles of the tongue MOST LATERAL ! Hands More 1) special - Vestibulocochlear (VIII) : Sensory frempons 2 Somatic sensory -> Trigeminal (v) : BOTH (emallregions 3) Visceral sensory & Facial , Gossoph Vagus., (111, IX X). : rest Of BOTH , all have ANS (parasymp functions). , all in Medulla 4) not oculomotor IN CANS) 4) Visceral motor e oculomotor , facial , glossoph., vagus (111, VII, IX X),. IN all ANS (parasymp) + CNIII all over brain O , 5) Somatic motor - oculomotor trachlear abducens , , , trigeminds, ↳ cranial nerve nuclei - in brainslow faudl , glossoph., spinal accessory lall motor but X11 + receive somatosensory info and make both (trigeminal-face glosso. ( + i axons synapses coming in or out · act as origins/terminations for CN's most medial ! I part of CNS) (ANS) Parasympathic 1) motor nuclei : medial III. Oculomotor sensory nuclei lateral 3 : VII. Facial Autonomic nuclei in blup IX Glossopharyngeal :. X. Vagus. 2 Reticular Formation set of neurons involved in integrative functions - ↳ steredyped responses (Chewi smiles autonomic Mcs (MR BP) ascending anousal (sleep wake cycle motor , , , ↳ periaqueductal gray coordinates + organizes each level of fear response (defensive behaviour) part of reticular formation : , but controlled by hypo. thalamus systemstainbranstemavadicerbrconex aleness t conscious state manganusa - min · unatenter diff from what leaves goes thre thalamus e (1) Dorsal Path. - 2 (2) Ventral Path - goes directly ro conex * sensory info is transformed as it moves through each synaptic