NS Flashcards
- What are sensory R? Types of R? Labelled line principle
Specialised epithelial/neuronal cells transducing environ stim > neural signal Types
- Mechano - Pacinian, Golgi, Baro, Hair cells (auditory and vestibular sys)
- Tactile sensations - Touch, pressue, vibration, tickle
- Proprio - static position and rate of movement
- Chemo
- Thermo
- Noci - Photo - rods and cones
LLP - Each R sensitive to 1 type of stimulus
Receptive field - area when stimulates > change firing rate (can be inhibitory or excitory)
74 Receptor Potential Adaption
RP - change in membrane potential by stimulus, can be from
- mech deform
- chem
- temp - alter permeability
- EM radiation - direct/indirect
Characteristic of RP -
- graded in size (intesity propor to RP amp)
- spead short distances
- can be summed
- threshold > AP: Absolute threshold: lowest level > causes sensation; (absolute sensitivity of the sensory systems) Differential threshold: smallest difference in two similar stimuli that a person can detect; (analyze the discrimination sensitivity of the sensory systems)
Adaption - can happen partially/ completely over time by
- physiochem properties of R changing
- accomodation - graduation inact of Na+ channel
- Rapid - detect change in stim strength - pacinian, proprio
- Slow - detect Continuous Stimulus Strength - golgi, msc spindle, chemo Noci not adapt
- Somatic sensations. General organization. The tactile and position senses.
Somatic Sensations - from skin, muscles, bones, tendons and joints - pain, temp, mecho (tacile, proprio)
General Org
- a) Mechano - mech displacement - tactile (touch pressure, vibration, tickle) and proprio (position and rate of movement)
- b) Pain
- c) Temp or
- Exteroreceptive - from surface of skin
- proprioceptive - Static position/Rate of movement sense
- Visceral - int org
- Deep sens - from deep tissues
Tactile
Mechanoreceptors (6)
- 1) Free nerve ending - temp, pain and pressure, varying density all skin and cornea
- 2) Meisnner corpuscle - light touch encode velocity, encapsulated, rapid adapt, nonhairy skin
- 3) Merkel Disk - slow adapt, continous touch, hair and non-hairy skin
- 4) Hair end organs - touch R rapid adapt, detect movement of object on surface
- 5) Ruffini ending - continous touch and pressure, found deeper tissue and joint capsule, little adaption (slow), enapsulates
- 6) Pacinian corpuscle - vibration and tapping, surround unmyelinated, skin and deeper tissues e.g. fascia
- Tactile and Proprioception
Mechanoreceptors (6)
- 1) Free nerve ending - temp, pain and pressure, varying density all skin and cornea, sense tickle and itch, rapid adapt (C, slow)
- 2) Meisnner corpuscle - upper dermis projecting into epidermis, glaborous, small well definied RF, encapsulated, rapid adapt, fine touch
- 3) Merkel Disk - upper dermis to base of dermis, hair and glaborous, small well definied RF, slow adapt, continous touch
- 4) Hair end organs - touch R rapid adapt, detect movement of object on surface
- 5) Ruffini ending - dermis, hairy and glaborous, Large RF, encpsulated, slow adapt, continous touch and pressure
- 6) Pacinian corpuscle - deeper dermis, hairy and glaborous, Large RF, encapsulated, rapid adapt, vibration and tapping (A-beta)
Propriceptors
- Golgi Tendon Organs - near muscle tendon, monitor tension
- Muscle Spindle - intrafusal fibres, degree and rate of stretch
Transmit
Most tactile receptors transmit signals over relatively large myelinated fibers A-beta (Rapid conduction)
Free nerve endings - A-delta small myelinated fibers and unmyelinated type C fibers (slow).
- Sensory pathways for transmission of somatic signals into the central nervous system. Somatic sensory cortex.
Dorsal column - fine touch, pressure, 2 point discrim, vibration, proprio
- Dorsal root > dorsal root ganglion > ipsilat fasciular cuneatus and gracilis > synapse nucleus (medulla)
- Nucleus > decuss (int arcuate fibres) > form medial lemniscus >synapse in VPL nucleus thalamus
- VPLN > post limb of int capsule > post central gyrus (broadman 3, 2, 1)
ALS/Spinothalmic tract - temp + pain (lateral), crude touch (Ventral)
- Dorsal root > dorsal root ganglion > synapse ipsilat dorsal horn (n. proprius - lamina 3-4)
- Ascend several levels (> decus/not ant white commisure > ventral spinothalmic tract > spinal lemniscus> synapse Parafasicular-cemtromeduiancomplex of intralaminar nuclei (and some to periaqueductal grey)
- brain stem anterior and lateral spinothalamic tracts combine to form the spinal lemniscus
- VPLN > internal capsule
Spinal Trigeminal - light touch, pain and temp face
- body in trigeminal ganglia >main sensory trigeminal nucleus
- trigeminal nucleus > decus and form trigeminal lemniscus > VPMN Thalamus
- VPMN thalamus > post limb of int capsule > primary somatosensory area
- some from mesencephalic trigem n (jaw muscles and joint > trigem motor > jaw jerk reflex
Unconcious proprioception from ventral spinocerebellar
- Somatic Sensations. Thermal Sensation
Somatic Sensations - from skin, muscles, bones, tendons and joints - pain, temp, mecho (tacile, proprio)
Thermal Sensations - ALS and Spinal
3 types of receptors: 1) cold 2)warm 3)pain
- cold and warm R under skin (3-10 X cold>warm)
- cold have A-delta myelinated
- Pain stim by extreme heat/cold
Spinal Trigeminal - light touch, pain and temp face
- body in trigeminal ganglia >main sensory trigeminal nucleus
- trigeminal nucleus > decus and form trigeminal lemniscus > VPMN Thalamus
- VPMN thalamus > post limb of int capsule > primary somatosensory area
Lateral spinothalmic - sharp, fast pain and temp to contralat hem
- DRG > synapse postmarg n (lamina 1) + substantia gelatinosa (lamina 2) [dorsal horn]
- Dorsal horn > decus > VPLN
- VPLN > post limb int capsule > post central gyrus
- Pain Sensation, suppresion, referred, visceral, Headache
- R are free nerve endings in skin msc and viscera
- Neurotransmitters - Substance P (inhibited by opioids)
- Activated by mech, thermal (tend to be fast) and chem stimuli (tend to be slow)
- R adapt slowly/not at all, hyper algesia for continous and greater
Types
- Fast - A-Delta (Group 3) rapid onset and offset, localised. [lateral spinothalmic tract]
- 6-30 m/sec
- Slow - C (group 4), felt after 1 sec, dull, aching, burning throbbing, poorly localised [ventral spinothalmic tract]
- 0.4-2 m/s
Suppresion
- Cerebrum > hypothalamus > activate PAQ opiate R (receive also ascending pathways)
- PAQ > n raphe magnus (5HT) and paragigantocellularis (Nadr) [medulla] > dorsalat tract >to dorsal horn enkephalin interneurons
- Enkephalin released and inhib post and pre synaptic fibres and block ALS
Can also supress by activation of rapid conducting tactile senses
Referred Pain
Usually involve visceral organs and tissues. Occurs as some synapse w/ spinal cord neurons receiving input from cutaneous areas e.g pancreas and back,
Visceral Pain
from int organs, caused by ischaemia,enlargement and chem damage
Headaches
Types of reffered pain to surface
- intracranial - from stretching of BV or dura, nerves etc e.g. migraines, memingeal inflammation (involve entire head)
- extracranial - msc spasm, irritation of nasal structures, difficulty focusing (eyestrain)
- Vestibular System
- Sensory system providing sense of balance
- Detects angular and linear acceleration and allows reflex adjustments of head, eyes and postural msc > stable image and steady posture
Consists of
- 3 perpendicular semicircular canal with semi circular duct inside (ant, post, lat). Ampulla contains crista ampullaris which is important for angular acceleration
- semicirc ducts filled with endolymph and canal w/ perilymph
- receptors - cilia embedded in cupula (gelatinous)
- Vestibule with utricle and saccule witch macula detecting linear acceleration.
- utricle has macula on floor and saccule has on wall pointing out (filled with perilymph)
- vestibule filled with endolypmpj
Kinocilium - sg long cillium
sterocilia, smaller cillia
- Vestibular sensations & Maintainence of Eqm
Maintainance of static Eqm
Acheived by relating position of kineocilium to sterocilium (hyperpolarise when bend away and depol bend towards)
Each cell have 1 kineocilium and 50-70 sterocilia. Kineocilium poisitoned to 1 side of apical surface and sterocilia shorter further away. Filaments connect cilium and allow opening of ion channel (ion enter from endolymph)
When head move, stataconia on surface of macula shift and move hair.
Hair cells groups orientated in specific directions so some inhibited when other excited
Angular acceleration
- Left rotation of head - lateral semicirc canal and attached cupula rotate left. Cupula initially move faster than endolymph therefore dragged through endolypmph > cilia bend
- If sterocilia bent towards kinocilium hair depol (+) if bent away hair hyperpol (-) > left horizontal canal excited and right inhib
- Endolymph catch up > cilia return upright > no longer depol/hyperpol
- If head suddenly stop - endolymph continue to move left > drag cilia opposite direction > hyperpol instead of depol/ vice versa
Stim of hair cells allow position identification
Vestibular ocular reflex - Nystagmus
- Nystagmus - initial rotation of head cause eyes to move in opposite direction. When limit reached eyes rapidly snap back and move slowly again
- Postorotary nystagmus - in opposite direction
- Auditory System. Ext, mid, inner ear
Sound travels from peripheral auditory system (ear) to central (cochlear nucleus in 1o auditory cortex) -converts signal and send impulses via the cochlear nerve
Ext ear - pinna directs sound waves into auditory canal
Mid ear
- Air filled, tympanic membrane transmit vibration from air to auditory ossicle (malleus, incus and stapes - amplify sound by lever action) > push stapes into oval window > displace fluid in inner ear
- tympanic membrane large and oval window small
- tensor tympani (attached to malleus) + stapedius attenuate sound
Inner ear (fluid filled)
- inc bony labyrinth (semicircular canal, cochlea, vestibule - filled w/ perilymph) and membranous labyrinth (filled with endolymph)
- cochlea inc scala vestibuli (perilymph + oval window), media (endolymph - K+ rich, basilar membrane) and tympani (perilymph, round window)
- Organ of Corti in basilar membrane of scala media
- Organ of corti - contain R cells (inner and outer hair w/ cilia protruding whilst embeded in tectorial membrane). Inner hair cells in sg rows (few), outer in parallel row (more), spiral ganglion contain cell bodies of auditory nerve
- Sound Transmission and Fct of Organ of Corti
Vibration patterns induced by different sound freq
- Ext ear - pinna directs sound waves into auditory canal > tympanic membrane
- Tympanic membrane transmit vibration from air to auditory ossicle (malleus, incus and stapes - amplify sound by lever action) > push stapes into oval window
- tensor tympani and stapedius attenuate by increasing rigidity of ossicular chain
- > displace fluid in cochlea > wave travel to basilar membrane > displace organ of corti up ot down
- Basilar membrane displace up> tectorial membrane (attached to hair cilia) move sterocilia > K+ channel open > depol > Ca2+ influx >release Neurotransmitter OR move down> hyperpol
- cochlear microphonic potential = oscialting potential
- Basilar more elastic than tectorial
Organ of corti - contain R cells (inner and outer hair w/ cilia protruding whilst embeded in tectorial membrane). Inner hair cells in sg rows (few), outer in parallel row (more), spiral ganglion contain cell bodies of auditory nerve
- Sound waves vibrate basilar membrane > excite hair cells
Sound Encoded
- Freq to activate particular hair cell depend on location of hair on basilar membrane
- Base of basilar (near oval and round window) - narrow stiff for high freq
- Apex of basilar (near helicotrema) - wide and compliant for low freq
- Auditory system and Central Auditory Pathway
Central Auditory Pathway
- 1o sensory fibres from spiral ganglion > dorsal and ventral cochlear nuclei (brainstem) > contralat (predom) and ipsilat >sup olivary nucleus
- sup olivary nucleus > fibres to lat lemniscus > inf colliculus
- Inf colliiculus > medial geniculate nucleus of thalamus
- medial geniculate nucleus > primary audiotory cortex (transverse temporal gyrus - Area41+42, secondar 22)
- tonotopic representation of freq at all levels of central (spatial representation of frq)
- Determination of sound direction
Sup olivary nucleus divided into med and lat
- lat - sound direction by detect diff in sound intensity transmitted from both ears
- med - sound direction by detec diff in time of arrival of sound from 2 ears
- Eye. Optics of Vision
- Conjuctiva - lubricates eye
- fibrous layer - cornea (ant - allow light to pass through) and sclera (post)
- Vascular layer -
- choroid - pigmented membrane absorbing reflected light ray (prevent reflection + scattering)
- iris - control pupil size (dilator pupilae -SNS and sphincter pupilae - PNS)
- cilary body - change shape of lens (ciliaris) , ciliary process (epithelial secrete aq humur) - attach to lens by suspensory ligaments
- Lens - focuses image on retina
- Sensory layer
- vitreous humor - transmit light rays and holds retina together, maintain intraocular pressure
- retina - photoreceptors > optic nerve
Optics of Vision
Accomodation - allowing focus on near object
- Need to change to covex, narrow pupil diamter and adduct both eyes
- ciliary muscle contract, suspensory lig relax > convex [PNS]
- pupil size - narrow to increase focal plane > increasesharpness
- normally - lens sph
- Presbyopia - Loss of accommodation as decrease in elastictisty of lens (less response - need bifocal)
Errors of Refraction
- Emmetropia refers to the normal eye - ciliary muscle is completely relaxed, all distant objects are in sharp focus on the retina.
- Hyperopia - light rays to focus behind the retina; this condition is corrected with a convex lens.
- Myopia - light rays to focus in front of the retina; this condition is corrected with a concave
- Astigmatism - curvature of lens not uniform, correct w/ cylindrical lens
- Cataracts - opacity that forms in a portion of the lens.
Visual Acuity: Sharpest within the Foveal Region of the Retina ( just cone photoreceptors)
- Visual System. Receptor and Neural fct of Retina
Retina - thin layer on back of eye with photoreceptors
- epithelial layer which absorb stray light to prevent scatter - melanin
- rods - detect dim light, everywhere except fovea, low acuity and high sensitivity (many rods on 1 bipolar), light sensitive rhodopsin is found in the rod outer segment [glutamate used by rods and cones]
- cones - detect colour, fovea (1.5mm), high acuity and low sensitivty (fewer cones on bipolar), color-sensitive photopsin in outer seg
- Bipolar cells - photorecep synapse here, bipol synapse on ganglion cells (transmit by graded potentials)
- Horizontal and amacrine cells - form local circuits w/ bipolar cells [GABA, glycine, dopamine, Ach, and indole amines]
- Ganglion cells - output, axons for optic nerve
10 Cellular Layers or Boundaries. 1. Pigment layer 2. Layer of rods and cones 3. Outer limiting membrane. 4. Outer nuclear layer 5. Outer plexiform layer 6. Inner nuclear layer 7. Inner plexiform layer 8. Ganglionic layer 9. Layer of optic nerve fibres 10. Inner limiting membrane
Each photoreceptor consists of (1) an outer segment, (2) an inner segment, (3) a nuclear region, and (4) the synaptic body or terminal
- Optic pathway. Organisation and fct of visual cortex
- Optic nerve ipsilat blind
- chiasm - heteronymous bitemp hemianopia
- tract > synapse Lat geniculate body - homonymous contralat hemianopia
- optic radiation (geniculocalcarine tract) > Baums loop (sup) and meyers loop (inf retina) - homonymous contralat hemianopia with macula sparing
- occipital cortex
+ retinal axons extend to other regions inc
- suprachiasmatic nucleus (control of circadian rhythms)
- pretectal nuclei (for pupillary light reflexes)
- superior colliculus (control of rapid eye movements)
- ventral lateral geniculate nucleus.
Receptive field organisation pg 41 +42
Organisation and fct of visual cortex (medially to occiptal pole)
primary visual cortex = area 17 of Brodmann
- medial surface of the hemisphere lining both walls of the calcarine sulcus near the occipital pole
- contralateral visual field
- lower visual field contained in the upper bank of the calcarine sulcus
- upper visual field located in the lower bank
- macular portion - posteriorly near the occipital pole
Secondary visual cortex= area 18 and 19 + mid temp gyrus and area 7a and 37 [surround primary]
