Bio 222
Terms
undefined, object
copy deck
- Mechanoreceptors: Percentage of hand covered
- Pascinian Corpuscle: 10-15% Ruffini's Ending: 20% Meissener's Corpuscle: 40% Merkel's Disk: 25%
- Mechanoreceptors: Smallest and Largest
- Merkel's Disk: smallest Pascinian Corpuscle: Largest
- Mechanoreceptors: sensitivity
- Pascinian Corpuscle: high frequency vibration Ruffini's Endings: skin stretch Meissner's Corpuscle: low frequency vibration Merkel's Disk: edges, points, curvature
- Mechanoreceptors: spacial acuity
- Pascinian Corpuscle: low Ruffini's Endings: low Meissner's Corpuscle: intermediate Merkel's Disk: high
- Receptive Field
- area of skin that significantly changes action potential firing rate when stimulated
- Mechanoreceptors: adaptation speed
- Pascinian Corpuscle: rapid Ruffini's Endings: slow Meissner's Corpuscles: rapid Merkel's Disk: slow
- Pascinian Corpuscle Receptor Function
- 1) mechanical deformation of membrane at onset/offset 2) mechanosensitive cation channels open 3) generator potential depolarizes axon 4) if threshold is reached, AP Onion-like corpuscle confers sensitivity to high-frequency vibration but not steady pressure
- Divisions of Spinal Cord and number of segments in each
- Cervical: 8 Thoracic: 12 Lumbar: 5 Sacral: 5
- Dermatome
- skin innervated by right and left dorsal roots for a single spinal segment
- Pathway which conveys touch info from body to cortex Kind of sensory axons used
- Dorsal Column-Medial Lemniscal Pathway; Abeta fibers
- Where do DCML 1st order neurons enter spinal cord, where do they go from there?
- Dorsal roots, ascend via ipsilateral dorsal column
- Topographic organization of dorsal columns
- Lower Body: fasciculus gracilis, medial Upper Body: fasciculus cuneatus, lateral
- Where do DCML 1st order neurons synapse?
- Dorsal Column Nuclei of Medulla -nucleus gracilis and nucleus cuneatus
- What is the 2nd order tract conveying touch info from body axons axons ascend via?
- Medial lemniscus
- Where do DCML 2nd order neurons synapse?
- Ventral posterior nucleus of thalamus
- What tract do 3rd order DCML neurons use to ascend to the cortex?
- Internal capsule
- Pathway for touch info from face to cortex?
- Trigeminal Nerve Pathway, cranial nerve 5
- Peripheral branches of cranial nerve which carries touch info from face to cortex?
- opthalamic, maxillary, mandibular
- Location of cell bodies in trigeminal nerve pathway (touch)
- trigeminal ganglion, mid-pons
- trigeminal nerve pathway: location of 1st order neuron synapse
- ipsilateral trigeminal nucleus
- Trigeminal nerve pathway: location of crossover
- 2nd order neurons crossover, forming trigeminal lemniscus
- Trigeminal 2nd order neurons projection tract
- trigeminal lemniscus
- Trigeminal Nerve Pathway: location of 2nd order neuron synapse
- VPM of thalamus
- Location of Somatosensory Cortex
- Parietal lobe of cerebral cortex
- S1 Columnar Organization
- Cortex has 3-6 layers Laver IV has stellate cells
- Layer of Thalamic Inputs to cortex
- IV stellate cells
- Cortical Columns
- neurons sharing inputs and responses stack vertically
- Features of Somatotopic Map
- -Not necessarily continuous -Body parts overrepresented -Density of sensory receptors -Smallest receptive fields -Importance of sensory input
- Cranial Nerve(s): olfactory
- I
- Cranial Nerve(s): vestibulo-ocular reflex
- III, IV, VI
- Cranial Nerve(s): touch system
- V
- Cranial Nerve(s): Pain/Temperature
- V
- Cranial Nerve(s): Vestibular System
- VIII
- Cranial Nerve(s): Gustatory
- VII, IX, X
- Vestibular Labyrinth
- organ of balance, vestibular portion of cranial nerve VIII
- Cochlea
- organ of hearing; auditory portion of cranial nerve VIII
- Endolymph
- fills membranous sacs within bony structure of vestibular labyrinth high [K+], low [Na+] similar to cytoplasm
- Two types of structures in vestibular labyrinth
- Two otolith organs Three semicircular canals Each has a sensory epithelium containing hair cells
- Hair Cells
- sensory cells for movement, have lots of cilia
- Kinocilium
- longest cilium of a hair cell
- Organization of Sensory Epithelium
- Polarized: groups of hair cells have their kinocilia oriented in the same direction; deflection of the cilia towards the kinocilium causes depolarization
- Otolith Organ, function, epithelium, and two features
- Detect head tilt and linear accelerations Epithelium: Macula Utricle and Saccule
- Utricle
- Macula oriented parallel to ground, connected to semicircular canals, sensitive to horizontal motion
- Saccule
- Macula oriented perpendicular to ground, connected to cochlea; sensitive to vertical movement
- Macula Orientation in Otolith Organs
- Kinocilia oriented in multiple directions; symmetrically represented
- Semicircular Canals: function, epithelium, and three parts
- Detection of angular accelerations (rotations) Sensory Epithelium is the Crista Three canals: superior, posterior, and lateral
- Structure of Semicircular Canals
- Each canal joins the utricle at an enlargement called the ampulla that houses the crista and cupula
- Ampulla
- Part of Semicircular Canal Contains: crista, hair bundle, cupula
- Crista
- Sensory epithelium of semicircular canals
- Hair Bundle
- cilia of hair cells
- Cupula
- gelatinous mass extending across ampulla
- Crista Orientation in Semicircular Canals
- Kinocilia are oriented in the same direction
- Deflection of Hair Cells
- Towards Kinocilia: depolarizing deflection --> increased transmitter release --> increased firing in vestibular ganglion cell Deflection away from kinocilia: hyperpolarizing deflection --> decreased transmitter release --> decreased firing in vestibular ganglion cell
- Signal Transduction in Hair Cells
- 1) Stretch activated cation channels open when cilia are deflected towards kinocilia 2) Membrane depolarizes 3) Voltage-gated Ca+2 channels open 4) NT released at synapse with vestibular ganglion cell
- Structure of the Macula
- Hair cells of macula are covered by a gelatinous layer and a membrane embedded with otoliths
- Tilt and Acceleration
- Backward sustained tilt and foward acceleration (no tilt) --> similar cilia bending
- Hair cell bending in crista
- when a canal moves, endolymph lags and pulls on cupula, which then moves towards/away from kinocilia depolarizing/hyperpolarizing hair cells and increasing/decreasing vestibular axon firing
- Activation of Semicircular Canals During Head Rotation
- Increased firing during acceleration, adaptation in firing rate during constant velocity, and decreased firing during decelleration
- Location of Vestibular Nuclei
- Brainstem
- Vestibular axon projection (cranial nerve)
- Cranial nerve VIII Cerebellum and Lateral Vestibular Nucleus (otolith) and Medial Vestibular Nucleus (semicircular)
- Otolith Projection
- Lateral Vestibular Nucleus --> Limb motor neurons (maintains posture)
- Semicircular Canal Projection
- Medial Vestibular Nucleus --> Neck motor neurons (orient heat), Extraocular Motor Nuclei (III, IV, VI)
- Vestibulo-Ocular Reflex
- Maintains focus of vision during head motion Left semicircular canal hair cells excited --> excite muscles that move eyes rightward + inhibit muscles that move eyes leftward Opposite side inhibited, will not excite muscles
- Pain
- Does not require activation of nociceptors, subjective
- Nociception
- not necessarily percieved as painful
- Thermoreceptor Activation
- Do not increase firing rate when stimuli become noxious
- Nociceptor Activation
- Starts responding when stimuli becomes noxious
- Nociceptors
- Free nerve endings of A delta and unmyelinated C fibers Most polymodal
- A delta and C receptors
- Smallest diameter, least myelin A delta, pain and temp C fibers: temp, pain, itch
- Chemicals that activate Nociceptors
- Bradykinin: made by enzyme released from damaged cells, directly activates via depolarization through GPC receptors ATP: made by enzyme released from damaged cells, directly activates P2X receptors K+: released from nociceptors, depolarizes nociceptors
- Hyperalgesia
- following injury, injury site and surrounding area have increased perception of pain
- Sensitization
- exposure of nociceptors to products of tissue damage increases their activity and their sensitivity to stimuli
- Chemicals that Sensitize Nociceptors
- Bradykinin: increases sensitivity of ion channels like TRPV1 Prostaglandins: made by enzyme released from damaged cells Substance P: released from nociceptors, causes vasodilation, and release of histamine from mast cells
- First Pain vs Second Pain
- First Pain: Adelta fiber, fast and sharp Second Pain: C fibers, long-lasting and dull