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cns Flashcards

1
Q

CNS basics

A

CNS = brain + spinal cord
* protected by bony structures (vertebrae) + 3 layers membranes = meninges
* receive afferent from PNS, analyse, sompare w past, + integrate to gen motor output to PNS

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2
Q

brain regions

A

forebrain = cerebrum + diencephalon w pit gland, limbic sys + olfactory bulb
midbrain = midbrain
hindbrain = pons + medulla oblongata + cerebellum

cerebrum has longitudinal fissure => L + R hemispheres

gyri = ridges, sulci = furrows
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3
Q

spinal cord

A

out brain @ foramen magnum, down vertebral canal
* each spinal seg gives off pair segmental spinal nerves to supply diff region of bod
* at caudal end canal cord peters out + spinal nerves for caudal structures form cauda equine

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4
Q

timeline brain development

A
  1. dorsal ectoderm thickens form neural plate
  2. other development processes overlap + continue well into adulthood
human timeline but same idea
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5
Q

neurulation

A
  1. notochord = cylinder mesodermal cells + secr chem signals inc prot sonic hedgehog induce formation neural plate
  2. chem signals also stim other mesodermal cells develop -> vertebral bods + intervertebral discs of spinal column (form protective structures)
  3. plate indented along midline = neural groove
  4. groove deepens + ectodermal walls thicken @ dorsal lips = neural folds
  5. folds fuse to close tube, starting cervical region + moving both rostral + caudal
  6. rostral/caudal neuropore = pt closed to (hole) - get smaller + smaller + close last
  7. dorsally either side superficial ectoderm proliferates -> cells -> pinch off + form neural crest
notocord incorped into vertebral column
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6
Q

which parts from neurulation form what

A

CNS from neural tube
PNS from tube + neural crest

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7
Q

what happens after neurulation

A

rostral neural tube forms vesicles bc its hollow
* first 3 primary vesicles develop
* these differentiate into secondary vesicles
* these develop to adult brain structures

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8
Q

which mols control patterning which parts CNS

A
  • patterning ventral structures controlled by sonic hedgehog prot from notochord
  • patterning dorsal structures controlled morphogenetic prot signals frojm superficial ectoderm
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9
Q

names of diff vesicle structures + development path

A

all early in gestation

differential growth means diff outpockets form

lateral view
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10
Q

brain flexures at vesicle stage

A

important to orient structures

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11
Q

cerebrospinal fluid is + why

A

bathes inside (w/in tube) + out (its in meninges) of CNS for nourishment, waste removal, protect brain

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12
Q

spina bifida occulta

A

incomplete rostral or caudal fusion of neural folds = tube open = vertebral arches can’t form + fuse = neural v close outside world
* caudally common tailless breeds

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13
Q

grey matter + white matter

A

grey = cell bodies, dendrites + synapses
white = axons - white bc of fat in myelin

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14
Q

glial cells

A

supporting cells in CNS

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15
Q

nuclei + tracts w/in contect CNS

A

nuclei = clusters of cell bodies in CNS (ganglia in PNS)

tracts = bundles of axins in CNS (nerves in PNS)

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16
Q

decussation of tracts

A

many CNS functions cross over bet 2 hemispheres cerebrum
== info from/output to R side bod handled by L side brain

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17
Q

cross section spinal cord vs cerebrum

A

spinal cord = grey matter inside, white out

cerebrum = white + basal nuclei in deep parts w grey formed over

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18
Q

corpus callosum

A

white matter tract connecting cerebrum hemispheres, allowing exchange info

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19
Q

corpus striatum

A

basal nuclei in cerebrum interwoven w white matter tracts = stripy appearance
* involved planning + executing (esp habitual) movements (motor function)
* input from motor cortex + integrate w other inputs (thalamus, limbic sys)
* important animals, e.g. birds, w/o developed cerebral cortex (instead of motor cortex)

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20
Q

lining neural tube

A

initially pseudostratified columnar then diffs 3 layers:
1. inner ventricular zone = germinal = ependymal = gen new cells (divide into)
2. mantle = neuroblasts migrated here + diff into neurones/glia (+ mitotic in interphase)
3. marginal = axons of neurones w cell bods in mantle = white matter

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21
Q

diagram cell types lining neural tube life cycle

A

lining -> ciliated to move CSF

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22
Q

surface cerebellum compared cerebrum

A

cerebellum = smaller folds tiss called folia (as opposed sulci/gyri)

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23
Q

important sulci/gyri to remember

A
  1. cruciate sulcus crosses longitudinal fissure at right angle w motor cortex controlling movement sat there
  2. sylvian gyrus involved in processing auditory info (looks like ear)
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24
Q

brain lobes

A

named after bone section sits under (ish)

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25
Q

what does frontal lobe control

A
  • thinking
  • speaking
  • memory
  • movement

== personality

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26
Q

what does parietal lobe do

A
  • language
  • touch
  • taste
  • smell
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27
Q

what does occipital lobe do

A
  • vision
  • colour
  • letters
  • L/R
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28
Q

what does temporal lobe do

A
  • hearing
  • learning
  • feelings
  • fear
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29
Q

cortexes: where + what

A
  1. motor cortex just rostral cruciate sulcus = conscious movement
  2. somato-sensory cortex just caudal = conscious sensation
  3. visual = caudal occ lobe (sight)
  4. auditory = ventral to cruciate sulcus, dorsal temp lobe (hearing)
  5. association cortex = rest, linking together, e.g. memory
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30
Q

developing cerebrum

A
  • internal cavity telencephalic forms lateral ventricles
  • cell bods form from mantle layer
  • SHH + BMP drive arrangement of regions

interconnected ventricles comm w central canal (remnants central cavity) in spinal cord

lat ventr comms rest of tube via 4th ventr

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31
Q

how are brain ventricles connected

A

lat ventr in each hemisphere, CSF flows thru interventricukar foramen in to 3rd ventr, thru mesencephalic aqueduct -> 4th ventr -> central canal

CSF is circulating around interconnected spaces then down canal

Only thin medullary vela seps lumen 4th from subarachnoid space
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32
Q

holoprosencephaly

A

failure in patterning vesicles as prosencephalon (forebrain) fails divide = single-lobed brain + single central eye
* can be caused by corn lily ingestion (cyclopamine toxin) - interferes w SHH signal recog

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33
Q

rhinencephalon is?

A

= olfactory bulb + olfactory tracts + olfactory peduncle + piriform lobe + hippocampus + fornix ==> olfaction for survival
* comms w higher centres affect emotion, behaviour, comms
* size reflects importance olfaction to species

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34
Q

how does rhinencephalon work

A
  1. olfactory bulb receives nerve fibres of olfactory nerve as run thru nasal cavity (via cribriform plate)
  2. down olfactory tracts
  3. **piriform lobe ** is part cerebral cortex where olfactory info processed
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35
Q

development brain stem general

A

midbrain from mesencephalon
pons from metencephalon
medulla oblongata from myelencephalon

mantle layers diff parts organise into dorsolateral alar plates + ventrolateral basal plates
* sepped by central roof + floor plates (no cont neuroblasts)

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36
Q

development myelencephalon/metencephalon

A
  1. alar mantle lamina stretches + move laterally over roof (made ependymal cells) to flatten
  2. form rhimbic lips that join in middle form cerebellum
  3. thickening develops ventrally form pons + medulla oblongata
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37
Q

cerebellum structure

A
  • central vermis
  • 3 peduncles either side connects it to brainstem
  • v folded cortex (-> folia) w central nuclei = grey matter
  • white matter branches = arbor vitae
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38
Q

cerebrllum development

A

2 lateral hemispheres formed from rhombic lips metencephalon
* joining of lips forms narrow central vermis

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39
Q

what is frontal cortex involved w

A
  • decision-making
  • planning
  • motivation
  • judgement
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40
Q

pre-frontal cortex

A

most rostral cerebrum
* personality + social behaviour

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41
Q

what does cerebral cortex do

A

allows conscious perception sensory input, movement muscs + conscious thought

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42
Q

limbic sys

A

series tracts + nuclei deep w/in cerebrum key to emotion, learning + memory
* species driven by instincts w less control over emotions + behaviours have relatively larger

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43
Q

thalamus

A

sensory info to brain synapses here b4 going -> cerebral cortex (except olfactory)
* also involved sleep + wakefulness

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44
Q

hypothalamus

A

connects endocrine + nervous sys + forms part limbic sys (= role in behaviour)

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45
Q

function brain stem

A
  1. cont key CV, resp, GI control centres
  2. cont nuclei for cranial nerves except I + II
  3. route comms bet higher structures + spinal cord
  4. tectum in midbrain involved orienting head + body in response sights + sounds
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46
Q

cerebellum functions

A
  1. organises + refines motor activity
  2. coordinates gait, control musc tone + voluntary musc activity
  3. compares intended movement w outcome = integrating sensory inputs
  4. balance + coordination - dysfunction = loss inhibitory component = loss coord

cant initiate musc contraction, can only refine

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47
Q

how does degree folding cerebral cortex vary

A

varies bet species mainly depending on how much space available in skull (also correlation w intelligence but less important)

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48
Q

how does association cortex vary bet species

A

amount incr w complexity of species + degree to which use prior experiences + memories to govern functions

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49
Q

layers meninges

A
  1. dura mater (outside)
  2. arachnoid mater
  3. pia mater
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50
Q

functions of meninges

A
  • physical protection central nervous tiss
  • facilitate flow cerebrospinal fluid (CSF)
  • provide framework for bvs supplying CN tiss
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51
Q

dura mater

A
  • thick fibrous layer made collagen + elastic fibres
  • only CN tiss that’s pain sensitive (trigem innerv)
  • own blood supply

2 layers: outer periosteal + inner meningeal - usually indistinguishable except seps as goes into 2 fissures, forming venous sinuses:
1. falx cerebri in longitudinal fissure
2. tentorium cerebelli in transverse fissure

fused to endosteum

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52
Q

where is transverse fissure

A

bet cerebellum + cerebral hemispheres

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53
Q

arachnoid mater

A

thin transparent mem w fibres forming web structure in subarachnoid space
* avascular, v lil innerv

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54
Q

subdural space

A

potential space = dura + arachnoid mater v closely associated, not much space, just a lil lymph-like fluid

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55
Q

subarachnoid space

A

true space, criss-crossed by fine collagen trabeculae + filaments (connect mems)
* conts CSF + bvs (supply nervous tiss)

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56
Q

pia mater

A

thin mem
* v vascular w dense innerv
* v adherent underlying tiss to nurture
* follows bvs into tiss + merges w tunica adventitia

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57
Q

denticulate ligaments

A

given off by pia mater, extend across subarach space + arach mater to join w dura mater
* act as sling to support spinal cord so no vibrate, bounce (= protect it)

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58
Q

how do meninges develop

A

from mesenchymal tiss around meninges
1. axial mesoderm -> mesenchyme -> ectomeninx -> dura mater (= pachymeninx)
2. neural crest cells from ectoderm -> mesenchyme -> endomeninx -> arach + pia mater (= leptomeninges)
3. spaces in mesenchyme coalesce -> subarach space

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59
Q

epidural space

A

dura seps from vertebrae w/in vertebral canal, creating epidural space
* -> filled w fat + CT = extra protection

=> dura mater only of spinal cord only attached to bone at foramen magnum + caudal end

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60
Q

filum terminale

A

beyond end spinal cord dura mater narrows form cord-like ligament that inserts on vertebra

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61
Q

cuff zones

A

formed from meninges around roots cranial + spinal nerves
* => grape-like structures where arach coming to end

dura mater most perm drugs, arach resistant but arach ending = more perm so these regions allow drugs to more easily enter CNS

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62
Q

cererbrospinal fluid (CSF) composition

A
  1. cell-free
  2. prot-free
  3. low aas (bc they function as NTs in CNS)
  4. low stable K+ (or would affect elec activity neurones)
  5. lower gluc than plasma
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63
Q

function CSF

A
  • physical protection CNS tiss
  • circulate nutrients + NTs to CNS tiss
  • make stable environ for neurones so random a pots no triggered
  • vol buffer - can decr to accomodate small CNS swelling

all works bc comms w ISF of neural tiss freely thru pia mater + ventr lining

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64
Q

how keep CSF stable

A

caps in CNS low permeability = blood brain barrier (BBB)
* tight junctions bet endothelial cells
* thick basement mem
* specialised connecting glial cells (astrocytes) have foot processes that decr permeability

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65
Q

where find CSF

A

circs subarach space, brain ventrs + central spinal canal
* constant prod + drainage = press grad, helps circ
* ventr + canal lined ependymal cells w cilia = help circ + joined loose desmosones = CSF can exchange w ISF of neural tiss

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66
Q

where do ventricles develop from

A
  1. laterals = telencephalic vesicles
  2. 3rd = central cavity of telencephalon + diencephalon
  3. mesencephalic aqueduct = mesencephalic vesicle
  4. 4th = rhombencephalon
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67
Q

where is CSF proded

A

mostly choroid plexi + small amount = ultrafiltrate pial bvs
1. bet lateral + 3rd ventr, pumping into ventr
2. in roof 4th - pumping into ventr + subarachnoid space

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68
Q

how is CSF proded

A
  1. transporting ependymal cells covering choroid plexi pump solutes (inc Na+) -> CSF
  2. draws water in by osmosis
  3. lipid soluble substances pass readily into CSF, e.g. O2, CO2
  4. cells + large mols like aas can’t pass across
  5. water soluble mats have be actively transported in, e.g. gluc

varies abt drugs passing in - some diseases affect perm of BBB

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69
Q

where does CSF drain

A
  1. out small holes in 4th ventr = bilateral apertures -> subarach space
  2. arach mat extensions arachnoid granulation/villi push thru dura into sinus -> venous circ

also via veins + lymph vessels around roots spinal nerves

press grad = flow 1 way, but can’t flow other even if press grad flipped

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70
Q

how does pia mater adhere underlying tiss

A
  • choroid plexi
  • reticular + elastic fibres
  • cytoplasmic process of astrocytes in neural tiss
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71
Q

what is choroid plexus

A

tiss tufts v vascular w network bvs in covered transporting ependymal cells in ventr

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72
Q

how do choroid plexi develop

A
  1. grooves form in ventromedial cerebral hemispheres = choroid fissures + pia mater covering it invags into lat ventrs
  2. tela choroidea = region pia mater that adheres underlying ependyma (neuroepithelial lining) invaginates in fold into roof 4th ventr in myelencephalon + trapped
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73
Q

how sample CSF

A

from subarach space:
1. where enlarged form cerebellomedullary cistern @ atlanto-occipital junction
2. where widens beyond end spinal cord form lumbar cistern (L5-6 space)

via cisternal puncture

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74
Q

atlas

A

C1 bone

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75
Q

why sample CSF

A

give idea of health - does it have prots in, less gluc than plasma etc

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76
Q

arterial supply CNS

A

centred round cerebral arterial circle on ventral aspect surrounding hypothalamus
* basilar + internal carotid arteries supply circle
* rostral/middle/caudal cerebral + rostral/caudal cerebellar arteries move to cerebral hemispheres + cerebellum

forebrain receives more than other areas

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77
Q

parenchyma

A

functional tiss of organ (distinguished from CT + supporting tiss)

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78
Q

possible arterial sources to circle

A

combo internal carotid, basilar, maxillary + vertebral
* varies bet species - important for humane slaughter to lose lots blood + lose consciousness quick = minimal pain (position of animal has effect)

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79
Q

circle arterial supply horse/dog

A

from internal carotid + basilar arteries

horse
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80
Q

circle arterial supply cow

A

maxillary + vertebral artery via 2 retia (net small vessels)
* decr press b4 brain + blood cooled down

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81
Q

circle arterial supply sheep/cat

A

mainly maxillary artery via rete mirabile
* internal carotids obliterated after birth
* basilar flows caudal so only blood -> caudal medulla oblong

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82
Q

collateral circ in brain

A

v few interarterial anastomoses = v lil collat circ = lots functional end arteries = occlusion/rupture => ischaemia + infarction of tiss supplies

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83
Q

brain venous drainage

A

low press sys = accoms changes in blod vol to maintain preload

slow, bidirectional, intermittent bloodflow w thin walls = potential seeding tumour or infection

variation bet species

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84
Q

what part does dorsal sagittal sinus drain

A

veins of cerebral hemispheres (dorsal part brain)

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85
Q

what part do cavernous sinuses drain

A

rostral forebrain, nasal cavity, orbit face = easy for infection -> blood supply

internal carotids traverse sinuses = cool blood in species w/o rete

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86
Q

spinal cord blood supply

A

branches aorta (caudal) + vertebral artery (cranial)

aorta enters thru intervertebral foramina -> 2 branches
1. small dorsal branch
2. ventral spinal art from coalescing large ventral branches

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87
Q

venous drainage spinal cord

A

bilateral venous plexi in epidural space w loads anastomoses -> segemntal vertebral veins at intervertebral foramina
-> vertebral vein/azygous vein/cranial caudal vena cava depending where in bod

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88
Q

eye =?

A
  • organ of sight - turns light -> a pots in retina (so need light -> there unhindered), optic nerve takes a pots -> visual cortex
  • develops from optic cup of embryonic diencephalon
  • in bony orbit surrounding supporting soft tiss structures (= adnexa)
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89
Q

eyeball layers

A
  1. outer fibrous sclera
  2. middle vascular uvea
  3. inner neural retina

shape layers maintained by internal support from humours

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90
Q

eye anatomy

A

canine/feline

anterior + posterior chambers both cont aqueous humour (= aqueous compartment split)
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91
Q

aqueous humour

A
  • transparent, colourless, water-like ~ low-prot plasma
  • proded ciliary process (constant w constant drainage)
  • maintains intraocular press (= HP) to maintain spherical eyeball
  • provides nutrients to avascular structures (cornea + lens)
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92
Q

vitreous humour

A

transparent, colourless hydrogel to maintain retina against choroid (support globe) + provide nutrients
* lamellar arrangement prot fibrils maintains transparency (trap hyaluronic acid)
* cont phagocytes to remove unwanted cellular debris
* cont hyalocytes to turn over hyaluronic acid
* attached caudal lens capsule, ciliary body + periphery optic disc

same over lifetime so old = more fluidy, affecting vision

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93
Q

fibrous tunic

A

opaque sclera caudally + transparent cornea rostrally
* junction bet them = limbus = drainage pt for aqueous humour of anterior chamber
* support + structure globe

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94
Q

cornea general

A

rostral 1/4, avascular
* transmits + refracts light = has be transparent + smooth (also nutrition)
* v sensitive w nerve endings - opthalmic branch trigem => corneal reflex (touch + blink)

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95
Q

layers cornea

A
  1. epithelium (squamous outer -> columnar) - protect stroma + decr water entry
  2. Bowman’s mem - thick, organised collagen fibres keep transparent, supporting keratocytes
  3. stroma
  4. Descemet’s mem - proded endothel to sep from stroma, thicker as older bc prod constant
  5. endothelium - actively pumps water from stroma to maintain transparent (can’t replicate = thins as cells spread to cover damage)

fluorescein stains stroma, not Descemet’s mem - know level of ulcer

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96
Q

sclera

A

dense fibrous CT + elastic fibres
* protects internal eye structures + maintains globe shape
* vascular w attachment extrinsic muscs
* axons from retina pass thru at lamina cribrosa to form optic nerve

dull white colour

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97
Q

uvea

A

== choroid (posterior uvea) + ciliary bod + iris (anterior) + suspensory ligament

vascular + pigmented to stop light out back eye
* firmly attached sclera at exit of optic nerve, less firm elsewhere

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98
Q

iris

A

sphincter w dilator + constrictor muscs to alter size pupil (= opening in centre)
* radial + circular sm musc fibres
* pigmented cells give range colours (lack pigment = light blue)
* ANS occulomotor n. - symp dil (= mydriasis), para constr (= miosis)
* seps anterior + posterior chambers

regs amount light entering eye

rostral continuation ciliary bod

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99
Q

choroid

A

eye lining (all of uvea behind lens, 2/3)
* vascular: bvs to all internal eyeball structures
* darkly pigmented to prevent light rays escaping out back eyeball

bet sclera + retina

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100
Q

tapetum lucidum

A

triangular yellow-green iridescent area light-reflecting cells w/in choroid dorsal to where optic nerve leaves
* reflects light back to photoreceptor cells = pass thru again = improve night vision

well developed carnis, present most mammals but humans + pigs

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101
Q

ciliary body

A

thickened continuation of choroid
1. ciliary musc = sm fibres to control thickness + shape lens
2. ciliary process secr aqueous humour into posterior chamber

also anchors lens

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102
Q

pathway outflow aqueous humour

A

posterior chamber, thru pupil + drained @ iridocorneal angle = venous plexus so humour can return circ
-> via trabecular meshwork -> Schlemm’s canal -> episcleral veins

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103
Q

iridocorneal angle

A

junction bet corneal limbus, root iris + anterior ciliary bod

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104
Q

glaucoma

A

iridocorneal angle blocked = drainage stopped = intraocular press builds up = red eye

serious

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105
Q

suspensory ligament of uvea

A

continuation of ciliary bod, forming circular support round lens perimeter (zonular fibres)
* connect bod (musc) to lens, all around lens’ circumference

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106
Q

lens

A

transparent biconcave disc sepping aqueous + vitreous compartments
* suspended by ciliary bod
* cont outer capsule, regular arrangement lens fibres (from around equator to meet anteriorly + posteriorly) + central nucleus
* concentric layers allow eye to focus

contr/relax ciliary musc w suspensory ligs alter shape + change depth of focus = lens accomodation

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107
Q

distance vs close focus

A

distance = relax musc, tight lig = lens stretched, longer, thinner, less refraction light

close = contr musc, slack lig = lens thicker + refracts light more

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108
Q

cataract

A

lens opacity due disruption arrangement lens fibres

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109
Q

retina

A

innermost eye layer of caudal wall
1. light focused onto photoreceptors (light sensitive) by lens
2. converts light -> a pots -> brain by optic nerve

nutrition from choroidal bvs externally + retinal bvs internally (run from optic disc)

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110
Q

layers retina

A

from closest to choroid (where light hits last)
1. retinal pigment epithelium (no pigment over tapetum lucidum)
2. photoreceptor cells (rods + cones)
3. bipolar neurons
4. multipolar ganglion cells

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111
Q

pigmented layer retina

A

prevent light leaking out eyeball, augmenting effect pigment cells in choroid (work together)

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112
Q

photoreceptor cells

A
  1. rods - sensitive low light levels but not colour = black + white + night vision
  2. cones - sensitive bright light, provide colour vision

dogs + cats = 95% cones = light + shade but colour poorly developed

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113
Q

bipolar neurons of retina

A

gather info from rods/cones + transmit to next layer

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114
Q

ganglion cells of retina

A

axons run across surface retina -> leave at optic disc form optic n.
* unmyelinated so light thru -> photoreceptors
* at optic nerve attachment no rods or cones = blind spot

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115
Q

ocular fundus

A

structures of posterior eye visible on opthalmic exam
* optic disc
* retina w pigmented epithelium
* retinal bvs
* choroid inc tapetum - where visible = tapetal fundus (rest = non-tapetal fundus)
* sometimes sclera

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116
Q

how are dog + cat fundus diff

A

dogs = white bc nerves becoming myelinated b4 leave eye

cats = no myelinated until leave eye => black

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117
Q

how is rabbit fundus diff

A

bvs only medial + lateral + band not circle of myelination

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118
Q

how is horse fundus diff

A

dots of vessels thru choroid layer (= stars of Winslow)
* abnormal other species that have large clear retinal bvs from optic disc

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119
Q

how does field of vision vary

A
  1. predatory species, e.g. cat = eyes pt forward, wide area binocular vision (fields of eyes overlap) = pinpt position accurately
  2. prey = eyes side head, mostly monocular/uniocular vision - less detail but greater field view to be able see where is to run away
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120
Q

cilia on eyelids

A

angled away from eye for further protection entry foreign mat

resemble human eyelashes

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121
Q

palpebral ligaments

A

give palpebral fissure its shape + hold canthi in place
* medial + lateral ligs

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122
Q

conjunctiva

A

v vascular mucous mem lining inside eyelid front eye except cornea
1. on eyelid = palpebral
2. on globe = bulbar

  • lots lymphoid tiss to protect against infection
  • conts goblet cells prod mucin component tear film (stabilise it)

covers nictitating mem

fornix = loose conjunctiva bet palpebral + bulbar
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123
Q

tears

A

keep corneal surface moist bc dry = cornea damaged = loss vision; cont:
1. mucin stabilise tears + keep tear film on eye surface (de goblet cells conjunctiva)
2. lipid reduce evap tears (de Meibomian/tarsal glands)
3. aqueous component = hydrating for eye health (de lacrimal gland + gland of 3rd eyelid @ base)

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124
Q

Meibomian glands

A

== tarsal glands
* sebaceous, in eyelids, proding oily (lipid) secr so tear film no evap from cornea

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125
Q

Harderian gland

A

under 3rd eyelid, proding 1/3 aqueous component tear film
* cherry eye = enlarged + protrudes from under nic mem (brachycephalics common) - surgery push back behind

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126
Q

cranial nerves to eye

A
  1. optic = sensory, transmit visual info retina -> brain
  2. trigem - mixed, inc sensory to structures surrounding eye + intraocular surfaces
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127
Q

diffs bet species w eyelid

A

cat = eyelids well atached to outside eye (narrow palperal fissure)

rabbit = structures looser = less good at moving tear film over eye

horse = prominent lacrimal caruncle (corner eye w oil/sweat glands)

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128
Q

lacrimal puncta

A

opening that pumps tears out eyes
* most have dorsal + ventral, rabbit just ventral

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129
Q

species diffs w cornea

A
  1. ungulates = horizontal oval shaped
  2. rabbits retain ability replicate corneal endothelium into adulthood
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130
Q

species diffs iris + pupil

A

cat constr = slit, dil = circle
dog/pig = circular pupil
ungular = horizontal oval shape for max. horizontal field vision (constricts on horizontal plane)

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131
Q

where do optic nerve + retina develop from

A

outgrowth of wall of wall of diencephalon (optic cup)

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132
Q

fovea

A

notch in retina w bipolar + ganglion cells displaced so easier for light thru
* 1:1 synaptic contact
* area greatest visual clarity
* only cones then rods round outside of eye

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133
Q

photopigment in rods

A

rhodopsin
* converts light E -> electrical E to interpret as vision

== opsin prot + small mol ‘retinal’ (~vit A)

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134
Q

why does vit A deficiency cause night blindness

A

vit A has be converted -> retinal to make rhodopsin (all animals can do)
* night vision = most sensitive = lost 1st
* dogs/apes/horses can convert β-carotene -> retinol but cats can’t = need consume vit A in diet

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135
Q

photopigments in cones

A

diff opsins in diff colour cones as tuned pick up diff colours
1. ‘blue rhodopsin’ = opsin S + retinal
2. ‘green rhodopsin’ = opsin M + retinal
3. ‘red rhodopsin’ = opsin L + retinal

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136
Q

trichromats

A

= have 3 diff opsin containing cones - most primates, most other animals can’t see in 3 colours

other mammals inc ungulates, cats = 2 diff opsin-cont cones = dichromats
birds = tetrachromats as have UV asw

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137
Q

night vision

A

rods more sensitive light than cones so deer have more cones = better light sensitivity = better night vision

just diff adaptations: colour, night vision etc

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138
Q

photoreceptor signal transduction in darkness

A

high cyclic GMP (cGMP) = special Na+ channs open = Na+ thru -> cell = photoreceptor cells active = release glutamate (NT)

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139
Q

cellular anatomy photoreceptor

A

lamina of discs stacked to pick up as much light as poss w/in mem
* light detecting prot (e.g. rhodopsin in rods) + cGMP-gated Na+ chann embedded in disc mem together
* transducins (G prots) embedded in disc mem too

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140
Q

what happens when light falls on photopigment

A
  1. light E ‘trapped’ by cis-retinal => changes conformation -> trans-retinal
  2. no longer fits in large opsin = ‘falls out’ = opsin undergoes conform change = active
  3. active opsin causes α subunit of transducin to activate cGMP phosphodiesterase
  4. cleaves cGMP = decr cGMP conc (incr GMP) = Na+ channs close = cell hyperpolarises = no release glutamate

== photoreceptors deactivates by light == no glutamate

analagous to NT acting via G-prot receptor

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141
Q

role of glutamate in photoreceptor signal transduction

A

have ‘on’ + ‘off’ bipolar cells where glutamate inhibitory/excitatory so turned on/off by light
1. ‘on’ activates ganglion cell w light
2. ‘off’ activates ganglion cell in darkness

then axons of ganglion cells form optic nerve so having ‘on’ + ‘off’ means more info to brain to work out what image is

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142
Q

other retinal neurones

A

horizontal + amacrine cells involved in processing image

143
Q

visual pathway

A
  • some neurones cross to other side brain, some don’t = partial decussation

lateral geniculate nucleus = lateral part thalamus for more visual processing
* some neurones peel off b4 here -> hypothalamus for reg day/night syscle
* some neurones peel off b4 here to travel to colliculus = involved visual reflexes

144
Q

pupillary light reflex

A

circular muscs of iris constr pupil
radial muscs of iris dil pupil

consensual constr if healthy = light in one but both constr

145
Q

visual cortex

A

vision processed hierarchically = processed at incr complex levels as go thru

146
Q

amblyopia

A

blindness w good eyes = nowt wrong w eye but can’t see
* if hide eye young animal then at 4mo expose - brain parts to eye never developed

==> early stim v important

also if covered adult eye for long time

147
Q

role spinal cord

A
  1. sensory = pass signals from sense receptors round bod -> brain
  2. motor = pass signals brain -> diff parts bod
  3. coord local reflexes for quick response to outside stim

basically coord bet barin + bod

148
Q

important spinal cord structures

A

intumescences = thickened regions leading brachial + lumbar plexi to supply FL + HL
* thick bc FL/HL have more to control = more neurones + neural tiss needed

vertebral column longer than spinal cord

149
Q

positioning foramen magnum

A

diff depending standing/walking position head relative to neck + bod

150
Q

conus medullaris

A

region at terminal end spinal cord = naturally tapers (cone shape)
* caudal to lumbosacral intumescence

151
Q

filum terminale

A

fine filament neural tiss (glial + ependymal cells)
* attaches to caudal vertebrae = hold cord in place

152
Q

spinal nerve

A

root + ganglia
* covered CT to protect

153
Q

internal anatomy spinal cord

A

grey matter divided horns
white matter divided funiculi (regions) w fasciculi w/in

stained
154
Q

grey matter horns

A

profiles of columns of cell bodies
1. sensory info from spinal nerve feeds into dorsal horn
2. motor info going to ventral root of spinal nerve originates ventral horn
3. lateral horn conts cell bods of symp NS + interneurons - only in thoracolumbar spinal segs

155
Q

development spinal cord

A
  • mantle seps -> alar + basal plates (symmetrical halves) -> dorsal + ventral horns (grey matter)
  • marginal -> white matter
156
Q

development PNS

A
  1. neuroblasts in basal plate -> lower motor neurones w axons growing out thru marginal layer -> vertebral canal
  2. neuroblasts in neural crest -> spinal ganglia -> sensory neurones as cytoplasmic process grows into alar plate
  3. neural crest cells AND preganglionic fibres from kateral horn -> autonomic ganglia
157
Q

structure spinal cord segment

A

repeat going down cord

158
Q

spinal cord segs arrangement down cord

A

at top nerves come out laterally, but as move down go caudal in column b4 leave laterally

named similarly to vertebrae
* but 8 cervical bc 1st 7 come out foramina cranial vertebra, then C8-> foramina caudal (7 C vertebra)
* segs + vertebrae start aligned but C3-T2 shorter = less, then after T3 longer = end of thoracic aligned again. lumbar = getting shorter bc less structures to supply + all rest segs w/in lumbar region vertebral column

159
Q

how does cauda equina form

A
  • late embryonic period = spinal cord + vert column same length all align + nerves emerge next to originating location
  • vertebral column grows faster than spinal cord, pulling nerves w = cauda aquina
160
Q

functional regions spinal cord

as opposed anatomical

A

grping based region supply not anatomical origin
* see where issue is in bod, match = see where lesion is

  1. cervical (neck) = C1-C5
  2. cervical intumescence: FL = C6-T2
  3. thoracolumbar (thorax + abdom) = T3-L3
  4. lumbosac intum (pelvic cavity, limb + perineum) = L4-S3
  5. caudal (tail) = Cd1-Cd5
161
Q

dermatomes

A

skin zones in belts round bod (+ longitudinally in extremities) each sending sensory signals to 1 spinal cord seg
-> injury to spinal nerve associated characteristic pattern numbing of skin w/in zone - feeling stops then starts again as move caudal

useful to localise lesion

162
Q

plexi

A

dorsal + ventral branches of spinal nerves connect w neighbours = form continuous dorsal + ventral networks
1. C6-T2 = brachial plexus
2. L4-S3 = lumbosacral plexus

163
Q

what does larger ventral horns mean

A

more motor cell bods bc more neurones = more muscs needing innerv

164
Q

ascending vs descending tracts

A

asc = sensory tracts from skin + musculoskeletal sys -> cerebral cortex
desc = motor tracts from cerebral cortex -> sk muscs

165
Q

funiculi

A

funiculus = region cont diff bundles nerve fibres/axons
1. dorsal = sensory tracts
2. ventral = mixed sense + motor
3. lateral: lateral part sensory, rest mixed

166
Q

fasciculi

A

fasciculus = bundle of same anatomical nerve fibres/axons

funiculus conts many fasciculi

167
Q

fasciculi of dorsal funiculus

A
  1. fasciculus gracilis + fasciculus cuneatus involved awareness where bod parts are
  2. fasciculus proprius involved response to vibration
168
Q

spinal reflex

A

local reflexes not requiring input or output from brain

169
Q

components motor sys

A
  • motor cortex - learn specific voluntary movements
  • basal nuclei
  • thalamus - decision making
  • red nucleus (midbrain) - motor coord
  • substantia nigra (midbrain) - maintain contact w rewarding stimuli = eye movement, planning movement
  • nuclei in pons + med oblong
  • spinal cord
  • cranial + spinal nerves
  • NMJ to integrate nerve + musc
  • sk musc
170
Q

integration motor sys

A
  1. cortex decides do movement
  2. -> brainstem -> bod to do it
  3. also -> pons -> cerebellum so knows what intended
  4. sensory from bod of what happened -> pons -> cerebellum
  5. cerebellum compares - need refine movement?
  6. sends that -> thalamus -> cortex

== feedback mech

171
Q

structure somatic NS

A
172
Q

upper motor neuron (UMN)

A
  • exist wholly w/in CNS
  • cell bods in brain + synapse on LMNs (directly or via interneurons
  • initiate, reg, modify, terminate LMN activity (control them)

required voluntary movement sk musc

most go down spinal cord + synapse w LMN that leaves spinal cord
1. -> LMNs supplying flexor muscs travel in lateral funiculi
2. -> LMNs supplying extensor muscs travel in ventral funiculi

173
Q

lower motor neurons (LMNs)

A
  • cell bod in CNS + axon in PNS
  • run via spinal or cranial nerves to innerv sk musc (from intumescences)
  • a pot causes musc contraction
  • can be influenced by >1 UMN

can fire w/o UMN input (reflexes)

174
Q

normal sitch w LMNs

A

conscious = constant sub-threshold depol -> ACh -> musc tone + trophic support, e.g. help posture

175
Q

what happens if damage LMN

A

muscs flaccid + atrophy w/in few days = lose reflexes, can’t contract
* same signs for damage anywhere on motor unit

176
Q

what happens if damage UMN

A

extensor muscs dominant to maintain posture, tempered by inhibitory UMNs (most are inhib)
* they dampen signal so damage those to flexors = extensors take over = spasticity (legs stuck long etc) - voluntary control to flexors gone

reflexes + tone normal/incr bc no longer inhib, atrophy only mild due disuse, coordination/control decr but strength normal

damage spinal cord = signs UMN damage anything caudal to that pt

177
Q

motor unit

A

LMN + NMJ + sk musc fibres
* small = few musc fibres per neuron = easier control, fine movement, e.g. muscs eyes, low force movements
* large = for more force bc more fibres contracting together

178
Q

under what circumstance can musc not contract

A

as long as intact LMN can contract
* so intact sensory = can do reflex (damage UMN = reflex exaggerated bc inhib)

179
Q

reflex defn

A

functional unit of NS
* innate reaction to stim present from birth
* sensory -> motor w/o influence higher centres (no UMN input)

would usually have sensory component -> brain so aware what’s happening

180
Q

reflex vs response

A

innate vs learned behaviour
* no higher centre vs higher centre

e.g. of response = poke eye + blink - baby won’t do bc hasn’t learned it hurts

181
Q

monosynaptic vs polysynaptic

A

mono = sensory neuron directly synapses w motor
poly = interneuron connects them

somatic reflexes one or other

182
Q

ipsilateral vs contralateral

A

ipsi = sensory input + motor output same side
contra = opp sides

somatic reflexes one or other

183
Q

intrasegmental vs intersegmental

A

intra = all sensory motor w/in same spinal seg
inter = crossing >1 seg

some somatic reflexes have components of both

184
Q

flexor withdrawal reflex

== withdrawal reflex == nociceptive flexion reflex

A

noxious stimulus -> sensory neuron -> interneuron -> motor (polysynaptic) -> inhibit quads (extensor), stim hamstring (flexor)
* decussation -> other side so extensor muscs contract + can bearweight (no fall over)

185
Q

nociception

A

pain b4 reaches forebrain + interped = neural signals
* caused noxious stimulus

186
Q

musc spindle

A

stretch receptors - detect change in length of musc
* intrafusal musc fibres inside w sensory nerve fibres around to feedback

187
Q

how make sure musc spindle still functions if musc shorter

A

shorter (e.g. musc contracted) = slackened = won’t detect stretch but need be active regardless to detect stretch
* **gamma motor nerve fibres **cause just intrafusal musc fibres still contract = keep spindle + nerves taut = can detect stretch

188
Q

golgi tendon organ

A

at interface bet musc + tendon w extrafusal musc fibres running thru it
* detect contraction as tendon no move, musc does, golg shortens
* => dampens contr so musc no overcontract - no want pull musc off tendon

189
Q

patella reflex

A
  1. strike patella tendon = stretches lil bit, picked up by musc spindles w/in quadriceps musc = sensory (1a afferent fibre) -> dorsal horn direct synapse (monosynaptic) -> motor (α motor neuron) in ventral horn -> musc contract (extrafusal fibres) + extend stifle joint
  2. 1a afferent also stims gamma motor neuron = contraction intrafusal fibres so spindle can still detect stretch
  3. musc contracts = stims golgi tendon organ, sends sensory (1b afferent) -> spinal cord dorsal horn -> inhibit α motor neuron to prevent overcontracting
  4. also causes motor neuron antagonistic musc inhibited so relaxes (hamstring) = intersegmental + via interneurons
190
Q

path of neurons etc for voluntary movement + why

A

UMN -> γLMN -> intrafusal fibres contract -> activate musc spindle -> 1a afferent signal -> αLMN -> extrafusal fibres contract

==> amplification of signal

γ = gamma; == ‘γ-1a-α activation’

191
Q

corticospinal tract

A

fine motor skills

== corticonuclear tract from cortex to cranial nerve nuclei

= cortex -> spinal cord, nerves nearly always decuss

UMN tract

192
Q

rubrospinal tract

A

for skilled movements
* cortical input so can serve similar function to corticospinal tract in non-primates

red nucleus in midbrain -> spinal cord

UMN tract

deep to tectospinal tract
193
Q

tectospinal tract

A

orients head + eyes in response sight, sounds

tectum (root midbrain) -> spinal cord

UMN tract

194
Q

vestibulospinal tract

A

for maintenance posture/balance

vestibular nuclei in med oblong -> spinal cord

UMN tract

195
Q

reticulospinal tract

A

stabilises bod against gravity

reticular formation in med oblong -> spinal cord

UMN tract

196
Q

pyramidal + extrapyramidal tracts

A

corticospinal runs caudally in ventral medulla + tracts form triangular shape (transverse section) = the pyramidal tract (fine voluntray movement)

all other UMN tracts extrapyramidal (all originate brainstem)
* mainly control posture + subconscious rhythmic movement
* but rubrospinal gens fine skilled movements in non-primates

197
Q

species diffs in pyramidal vs extrapyramidal

A

horse = mostly big coarse movements, only fine in head, e.g. move lips

cat = fine mostly important FL + head + lil bit elsewhere

thickness shows how much need it, + shows extent UMN continues down spinal cord
198
Q

somatosensory

A

= things you’re aware of (as opposed autonomic)
* touch, pain (superficial + true), temp, proprioception, kinesthesia

199
Q

special senses

A
  • vision
  • olfaction
  • gustation
  • audition (hearing)
  • vestibulation (balance)
200
Q

proprioception

A

understanding where part of bod is at any given time
* subconscious but can feel

201
Q

kinesthesia

A

ability to tell if part bod moving

202
Q

generalised organisation sensory sys

A

sensory receptor -> primary afferent -> spinal ganglion -> spinal cord -> synapse in thalamus -> interpreted as somatic sensory in cortex
1. touch decusses at midbrain (red)
2. pain decusses as enters spinal cord segment (purple)

203
Q

general organisation motor sys

A

cortex -> (maybe synapse in brain stem if extrapyramidal tract) -> ventral root -> musc
* decusses at midbrain

204
Q

modality of sense

A

what type of sense is it

also have modality of stimulus

205
Q

types receptor

A
  1. mechanoreceptor - touch, proprioception, kinesthesia, pinprick/deep nociception
  2. chemical - pinprick/deep nociception
  3. heat - temp, pinprick/deep nociception
  4. cold - temp, pinprick/deep nociception

~mechanical, chem, temp

206
Q

types mechanoreceptor

A
  1. Meissner
  2. Pacinian
  3. Merkel cell
  4. Ruffini endings
  5. free nerve ending (completely diff structure)
207
Q

Meissner mechanoreceptor

A
  • axon loops w non-neuronal support cells
  • at superficial epidermal/dermal boundary (smooth skin)
  • perceive flutter
  • small receptive field
  • rapidly adapting

neurone then structure

208
Q

Pacinian corpuscle

A

typical mechanoreceptor (touch) of skin
* single neurone in w non-neuronal capsule (CT, layers prot)
* so bigger area that if touched will activate neurone = large receptive field
* rapidly adapting
* deep under all skin types (dermis + subcut)
* perceive vibration

209
Q

merkel cell

A
  • shallow in smooth + hairy skin
  • slowly adapting
  • small receptive field
  • perceive press
single neurone in + structure
210
Q

ruffini ending

A
  • lie deep in all skin types
  • detect stretch - like golg tension organ not attached musc (means frequency continuous range)
  • slowly adapting
  • large receptive field
211
Q

slowly vs rapidly adapting

A

slow = receptor registers steady state + then stims a pot, not whilst starting apply force

rapid = registers when stretching or relaxing (force is changing) - then rapid fires a pots

together bod always knows if force incr (stretching), decr (relaxing) or stable

212
Q

receptive field sizes

A

size area 1 sensory receptor picks up from
* generally hairy skin + viscera big field, smooth (glabrous) skin small
* determines how well can distinguish bet diff pts on skin, pinpt exactly where feel

213
Q

really basic how do receptors work

A

mechanical = ion channs open w movement + open stims a pot

chemical = ion channs open w chems, e.g. free nerve endings

214
Q

free nerve endings

A

polymodal pain receptors = pick up range stimuli (pain, temp)
* can act as mechanoreceptors, chem receptors, etc

215
Q

main somatosensory nerve fibres

A

Aα (I) = musc sensory, fastest, myelinated (72-120m/s)
Aβ (II) = mechanosensors (36-72m/s)
Aδ (III) = nociceptors/temp for ordinary pain, small, lightly myelinated (4-36m/s)
C-fibres (IV) = nociception (exclusively for pain, mainly inflammatory), small unmyelinated (0.4-2m/s)

216
Q

ascending pathways

A
  1. dorsal column
  2. ventrolateral
  3. spinocerebellar
  4. spinocervical
217
Q

dorsal column

A

== medial lemniscal pathway
for touch + proprioception
* esp touch discrimination

  1. synapses in gracile + cuneate nuclei in medulla
  2. then cross in medulla
  3. through medial lemniscus region in brainstem
  4. to thalamus
218
Q

ventrolateral pathway

= anteriolateral

A

inc spinothalamic tract + spinoreticular tract for all modalities except proprioception, esp PAIN

spinothalamic = spine -> thalamus direct via medial lemniscus - pinprick + thermal stimuli

spinoreticular = spine -> reticular formation in medulla -> thalamus - true pain

cross in cord

spinothalamic is underdeveloped in non-primates

219
Q

why is spinoreticular slower

A

synapses - okay bc pain supposed to be slow evolutionarily so can run away (+ also just no benefit to feeling it fast)

220
Q

spinocerebellar

A

musc + joint proprioceptors -> synapse in dorsal horn -> cerebellum

for balance + movement, e.g. postural reflexes
* proprioception + kinesthesia

ipsolateral = no cross
occassionally cross twice

221
Q

spinocervical

A

sep innerv sys for whiskers + fur where individual axon wraps round (= lanceolate ending) -> Aβ primary afferent -> through lateral funiculus -> lateral cervical nuclei in CR -> cross here -> medial lemniscus -> thalamus

for touch, pinprick, fleas

humans no have

222
Q

sensotopic arrangement of sensory cortex

A

sensory to tail at top, head bottom bc structural arrangement w/in cortex

223
Q

how is gait coordinated

A

pattern gened in spinal cord - each limb has central pattern generator (CPG)
* input from higher centres to refine but not necessary for basic function

faster gait = less overall contact time w floor

224
Q

span defn

A

distance bod moves whilst foot stays on floor

225
Q

stride defn

A

distance bet where same foot lands 2 consecutive times

226
Q

pace gait

A

2 beat
LF + LH together, then RF + RH together

227
Q

what do proprioceptors sense

A
  • body position
  • strength + speed of movement

all to ensure posture appropriate

228
Q

diff proprioceptors

A
  1. musc spindles
  2. golgi tension organs
  3. joint receptors for angle + press joints
  4. mechanoreceptors
  5. vestibular sys hair cells for orientation of head
229
Q

difference bet having + demonstrating normal proprioception

A

may have it but w/o normal motor function can’t move legs = can’t correct it = can’t illustrate the awareness

230
Q

types proprioception

A

conscious + subconscious

can be hard distinguish, most neurological tests testing both

231
Q

subconscious proprioception

A

rhythmic movements - sitting, standing, breathing, chewing, scratching, basic locomotion, postural platform

proprioceptor -> neuron 1 -> synapse spinal cord grey matter -> spinocerebellar tract (neuron 2) -> ipsilateral cerebellum

input from head (CN V + VIII)

2 neurone sys, using input from somatic reflex arcs

232
Q

what is postural platform

A

bod well balanced in correct position for x

233
Q

deficit in subconscious proprioception

A

==> ataxia (loss of coordination)
alteration in rate, range, force movements
1. bod swaying - can’t find postural platform
2. base wide/narrow stance
3. non-intention tremor

bog obvious changes, but distinguish from weakness (test reflexes)

234
Q

conscious proprioception

A

for complex voluntary movement, not needed basic locomotion

proprioceptor -> neuron 1 (dorsal column) -> cross in medulla -> neuron 2 -> thalamus -> neuron 3 (thalamocortical tract) -> contralateral somatosensory cortex (for perception what’s going on)

3 neurone sys

235
Q

deficit conscious proprioception

A
  • stumbling
  • knuckling - turn their paw, they don’t turn it back
  • intention tremor

more subtle than subconscious

236
Q

spinal tracts of proprioception

A

conscious = dorsal column
subconscious = spinocerebellar

larger + on outside = more vulnerable damage
heavily myelinated

237
Q

proprioception vs kinesthesia

A

sense vs awareness + ability perceive extent + refine
(of position + movement of bod)

same way that nociception is sense + pain is perception

238
Q

functional regions cerebellum

A
  1. vestibulocerebellum coords balance + eye movements
  2. spinocerebellum coords musc tone + movement
  3. cerebrocerebellum for planning movements (in hemis)
239
Q

anatomy mammalian ear label

A
240
Q

overview how we hear

A
  1. sound = vibrating air steered in by pinna
  2. travels down auditory canal + vibrates tympanic mem
  3. oscillates malleus, incus + stapes
  4. sets up amplified vibration of littler oval window
  5. causes vibration in fluid-filled cochlea
241
Q

anatomy of cochlea

A
242
Q

what happens when cochlea vibrates

A

fluid (perilymph) in scala vestibuli vibrates as oval window vibrates, causing standard wave in basement mem as vibrations pass to round window for press release (allow more in at top)

demonstration of uncoiled cochlea
243
Q

endolymph + perilymph compositions

A

perilymph = normal extracellular fluid

endolymph = v high in potassium

244
Q

what happens once basement mem in cochlea vibrates

A
  1. sensory hair cells fixed bet basement + tectorial mems bend as b mem vibrates
  2. ;sensory hairs’ cont ion channs opened by movement
  3. causes depol of hair cells = activation of current
this together = organ of Corti
245
Q

how is frequency determined

A
  • thinner parts b mem vib more easily at higher frequs (highest detected cells round thinnest part b mem in base cochlea)
  • so each afferent nerve along cochlea has own characteristic frequ (CF) = frequ fire most readily at
  • low frequ = neurones phase lock at same frequ as incoming souond wave + fire a pots at same frequ (bc can’t have b mem thick enough to have CF low)
  • v high frequ = not poss so brain just detects which part basilar mem is vibrating + therefore pitch of sound = tonotopy
246
Q

why can smaller animals hear higher frequs

A

smaller = faster vibrations = some neurones have higher characteristic frequs = can hear higher frequencies

247
Q

frequency =?

equ + meaning of that

A

1/wavelength

incr frequ means decr wavelength

248
Q

brainstem auditory evoked responses

A

make sound w electrodes over part brain that should do hearing then record electrical responses in brainstem
* used to test hearing, diagnose deafness etc

249
Q

conductive deafness

A

sound cannot pass into ear due tumour, perforation ear drum, infec outer/middle ear, wax in ear canal, ear mites

may be reversible by treating root cause

250
Q

nerve deafness

A

bc nerves associated w ear don’t function properly due:
* genetics, e.g. dalmations
* inner ear infec
* drug toxicity
* noise trauma
* age-related degeneration

means permanent deafness

251
Q

innerv organ of Corti

A

most sensory sound info carried by type I afferents w axons making up auditory nerve from ‘hearing’ inner hair cells

outer hair cells = dampen + amplify frequs to filter sound (hence have afferents + efferents)

fewer inner hair cells but they have tonnes innerv

252
Q

otoacoustic sounds

A

play pure tone into ear + slightly motile outer hair cells constr + relax, causing b mem wobble = nearly inaudible sound echoes back into middle ear

253
Q

auditory pathway

A

cochlea -> medial geniculate nucleus in thalamus -> caudal colliculus in midbrain -> auditory cortex in cerebrum

all via auditory nerve (CN VIII)

254
Q

how does animal determine location of sound

A
  1. time delay since arrive at 1 ear before other
  2. volume difference due shielding by head so sound louder on closer side
255
Q

vestibular sys does what

A
  1. senses equilibrium (dynamic + static) = conscious perception of balance
  2. informs other syss abt changes in bod orientation relative to gravity + acceleration/deceleration of head
  3. used maintain balance thru reflexes
256
Q

path of vestibular sys

A

sensory receptors w/in labyrinth of inner ear then sensory afferent info via vestibular portion of vestibulocochlear n (CN VIII)

257
Q

labyrinth of inner ear structures

A
  1. crista ampullaris
  2. otolith organs (= maculae)
258
Q

crista ampullaris

A

in ampulla of semicircular canals
cupula (attached roof ampulla) = gel capsule w hair cells attached mem at base

move head = endolymph in inner ear moves = cupula moves = hairs bend, movement sensed by hair cells = signal down CN VIII

detect rotary movement for input for dynamic balance
* only input during acceleration or deceleration, not if rotation continuous

DETECT HEAD MOVEMENT

259
Q

otolith organ

A

gelatinous mass w calcium carbonate crystals (== otolith stones) in over hair cells on mem semicircular canals
1. hair cells oriented horizontal = utricle
2. hair cells oriented vertical = saccule

move head = gravity drags heavy stones = hairs bend, movement sensed by hair cells = signal down CN VIII

detect linear accel/decel + tilt of head for input for static balance

DETECT HEAD POSITION

260
Q

how are hair cells sensory

A

hair cells have longer cilium at one end - hairs can move towards or away from it
1. towards = depol mem = incr frequency a pots of neuron
2. away = hyperpol mem = decr frequ a pots of neuron

allows work out orientation of head

261
Q

pathway nerves in vestibular pathway

A

vestibular sys input down CN VIII -> synapse in medulla oblongata + pons (vestibular nuclei) -> decuss then:
1. up via thalamus to vestibular area in cerebral cortex for perception of balance
2. to occulomotor, trochlear + abducent nerves for occular muscs, => eyes to correct position when moving head in reflexes
3. -> accessory nerve nucleus for orientating head + neck in reflexes
4. down UMN vestibulospinal tract for orienting bod + limbs correct position
5. tracts to cerebellum to refine movement then back to nuclei in feedback loop

several diff pathways

262
Q

reflex defn

A

automatic, unconscious, unlearned response to stim

263
Q

postural reflexes

A
  1. vestibular reflex
  2. tonic neck reflex
  3. righting reflex
  4. vestibulo-ocular reflex to maintain stable image (keep eyes still so no blurry)
264
Q

vestibular reflex

A

vestibular organs detect change in head angle relative to gravity => limb movements to reduce angle of tilt + keep head stable

uses vestibulospinal tract

down hill = need make head higher so not parallel to slope = extend FL, flex HL
265
Q

tonic neck reflex

A

musc spindles in neck detect change in head:neck angle => limb movements to maintain horizontal head angle

neck muscs have higher density musc spindles than any other muscs

down hill = extend FL, flex HL to keep head up
266
Q

how can animal stand still + move its head

A

lift head whilst stood still = vestibular reflex sys + tonic neck reflex sys counteract => can move head around + stand still

267
Q

righting reflex

A

uses vestibular + tonic neck reflex pathways + skin press sensors
1. vestibular organs correct head position relative to gravity (= facing down)
2. rest body adjusted to align w head
3. otolith organs detect acceleration towards ground => limbs extend

mostly in cats

268
Q

vestibulo-ocular reflex

A

fixes image on retina during head rotations
vestibular sensory input + motor out via CN III, IV + VI
* slow drift eyes in opp direction to rotation as head moves then quick flick in same direction

prolonged rotation => post-rotatory nystagmus in opp direction due movement endolymph

269
Q

physiological nystagmus

A

flickering of eye

pathological nystagmus seen in vestibular disease

270
Q

what causes motion sickness

A

visual info used w vestibular input to determine head position + conflict bet 2 causes motion sickness as vestibular neurones synapse on vomiting centre in medulla oblongata

271
Q

vestibular disease

A
  1. peripheral resulting from disease or damage to sensory organs (utricle, saccule, semicircular canal, CNVIII)
  2. central resulting disease or damage to vestibular nuclei/central connections (brainstem, cerebellum)
272
Q

clinical signs vestibular disease

A
  • ataxia
  • head tilt
  • circling
  • nystagmus
  • vestibular strabismus - eye in wrong position
  • wide-based stance (bc unsteady)
  • vomming + salivation
273
Q

general concept of olfaction

A

odour mols = gases or dissolved in vapour droplets, then sensed by chemoreceptors
* odour detected at lower conc than taste

274
Q

olfactory organ adaptations

A
  • 2 pairs nares - external nostrils + internal nasopharynx
  • extensive network turbs => massive SA for sensory epithelium olfactory cells
  • mucosa v vascularised
275
Q

species variation in olfactory centre

A

rhinecephalon huge in most mammals except whales, primates, birds (birds from middle earth acc still big)

276
Q

how is dog sense smell useful to humans

A
  • rescue, e.g. find ppl in snow
  • watch dogs, even in silent dark
  • sniff out drugs + explosives
  • medical detection dogs, e.g. falls in blood sugar for diabetics
  • truffle pigs
  • pest control
277
Q

odour receptors

A
  • in olfactory cell in nasal epithelium
  • receptors G-prot coupled
  • individual smells have diff receptors w diff G-prots w diff 2nd messenger enzs
278
Q

noseblind

A

become desesitised to specific smell whilst all others work fine
* no happen for taste or vision bc 1 taste affects others

279
Q

how do olfactory receptors transduce signal

A

chem -> electrical (-> a pot) by 1 of 2 2nd messenger syss:
1. G prot activates adenylyl cyclase, then via cAMP opens ion chann => depol => a pot
2. G prot activates phospholipase C pathway to open Ca2+ chann => depol => a pot

280
Q

structure + arrangement olfactory cells

A

they are the primary afferent sensory neurones
* dendrite ends enlarged w cilia
* cilia cont receptor prots + are embedded in mucous on mem
* axons of cells come together form CN I

surrounded basal stem cells to gen new olfactory cells when damage = can grow back fairly high degree + have short lifetime as replaced by mitosis

281
Q

olfactory pathway

A

olfactory neurons unmyelinated axons -> CN I -> thru foramen in cribriform plate -> into olfactory bulb -> synapse w mitral/tufted cells -> olfactory pathway -> olfactory tubercle then:
1. -> olfactory cortex in temporal lobe -> organise olfactory reflexes + -> limbic centre hence emotional response w/o having noticed smell
2. -> frontal cortex (bypassing thalamus) -> conscious perception of smell

each mitral cell receives input from cells containing 1 receptor type

282
Q

Schwann cells

A

2 types surrounding neurons
1. around Aα neurons, laying down myelin
2. around other neurons holding together + making sure continue right direction, no prod myelin

found only PNS, not CNS

283
Q

olfactory ensheathing cells

A

cells same structure as Schwann cells type 2 surrounding olfactory cells - it’s these that give ability to regen
* experiments to see if can use this property to repair spinal cord damage

284
Q

anosmia

A

loss of sense of smell

285
Q

olfactory eversion test

A

something v strong under nose + look for visible response to see if CN I working

286
Q

vomeronasal organ

VNO

A

sep structure associated w olfactory bulb ventrally in nose to detect pheromones
* important in sexual behaviour

in dogs the anal glands prod pheromones

287
Q

role of pheromones

A

important for repro
1. mating calls + signals (Flehmen to promote stim of VNO by lip up + wrinkling nose to aspirate fluid into it)
2. maternal bonding w offspring so bitches known own young

also alongside normal odour detection + visual behaviour for social interactions bet animals

288
Q

potential human uses pheromones

A
  1. separation anxiety
  2. noise phobias - dog appeasing pheromone (DAP) (or use proper training, CDs to cancel out sound)
  3. performance - equine appeasing pheromone

not proven, esp since subjective but no objective improvements reported

289
Q

why did animals develop taste

A
  • eat food + use taste determine if safe to ingest or spit out
  • find nutrients required (e.g. fruit, salt) yummy so meet corporeal needs
290
Q

taste cell structure

A

taste cells clustered into taste buds, sat in pits (taste pores) in papillae on surface tongue
* have microvilli cont receptors
* taste cells synapse onto axon (no have own)
* surrounded basal cells to regen + replace damaged/killed cells

291
Q

taste buds of catfish

A

has loads bc muddy water + can’t see so everything in, taste what nutritious + should swallow
* carnis less bc eating less variety (more visually selective)

292
Q

flavours of taste cell receptor

A
  1. salt = ENac for any inorganic salt (via Na+ chann)
  2. sweet = T1R2 + T1R3 7 domain for non-ionised organics
  3. sour = H+ for acids
  4. bitter = T2R - often plant toxins
  5. others asw

each has specific transduction pathway

293
Q

species diffs in taste cell receptors

A
  • rumis like sweet, not artificial
  • cats have mutant sweet receptor gene = indifferent to sweet, like aas
294
Q

taste cell transduction

A
  1. 2nd messenger sys via adenylyl cyclase using cAMP/via phospholipase C to cause depol
  2. direct ion chann coupling to cause depol

either way depol => a pot -> Ca influx -> NT local release -> excite primary sensory neurones

295
Q

taste pathway

A
  1. primary afferent -> Nucleus tractus solitaris (NTS) thalamus -> cortex -> integration
  2. primary afferent -> NTS -> brainstem -> reflexes -> dribble
  3. primary afferent -> NTS -> limbic sys -> emotional response

CN VII, IX + X involved

296
Q

how is sensory smell + taste different/same

A
  • odour detected at lower conc than taste
  • 1 taste affects others as overall constructed varying components but individual smells diff receptors = no affect each other
  • can become desensitised specific smell whilst all others work fine, not for taste
  • taste cells synapse onto axon (olfactory cells have own)
  • both have stem cells alongside to replace damaged/killed cells
  • taste cells have microvilli as opposed cilia olfactory
  • taste cell transduction via 2nd messenger sys or direct ion chann coupling, olfcatory only by 2nd messenger sys
  • taste pathway = CN VII, XI, X involved; smell = just CN I
297
Q

classifications of memory

A
  1. declarative - knowing, e.g. spatial memory in animals (maps - migrating birds)
  2. non-declarative - knowing how (esp prevalent early life)
298
Q

types of memory

A
  1. development - esp bc memory can involve formation synapses (cats)
  2. conditioned so something becomes reflex response (Pavlov’s dogs)
  3. habitualisation = no longer does instinctive reaction bc thing happened enough w no neg effect that desensitised
  4. long term potentiation
299
Q

what is memory

A

changing a neuronal process in brain

300
Q

stages of memory

A
  1. short term = change in a pot firing
  2. intermediate = changes to prot synth
  3. long term = growing new synapses + connections (actual structural changes)

a process from 1 to next

301
Q

why not all short term mems become long term

A

filtering bc if remembered everything would have no capacity remember useful stuff
* vast majority stuff immediately forgotten

302
Q

types amnesia

A

retrograde = forget memories from past
anterograde = can’t remember anything new

303
Q

what is long term potentiation + where

A

process by which synaptic connections bet neurons become stronger by more frequent activation
* allows brain change in response experience
* same size stim gives bigger post syn pot every time (if stim same part brain)

1st discovered in hippocampus

304
Q

how does long term potentiation work

A
  1. low level glutamate release activates AMPA receptor on post syn mem
  2. NMDA glutamate receptor not activated at low levels bc Mg2+ blocking it
  3. frequent a pots + AMPA activation causes pos ions move in => mem depol => Mg2+ moves out NMDA = unblocked
  4. => Ca2+ can move in through NMDA ion channs
  5. => prot synth more AMPA receptors (CREBs involved in this)
  6. => post syn neuron more sensitive glutamate so bigger depol at each subsequent activation

pos feedback loop = Hebbian learning

305
Q

what are CREBs

A

family of prot transcription factors involved memory consolidation

306
Q

how can you see LTP has occurred

A

spines on dendrites = neurite growth due LTP w excitatory receptors
* during repetitive activity see new spines

307
Q

> 1 synapse on 1 neuron

A

stronger impact on post syn mem
* primary reinforcer = stimulus biologically important to organism, e.g. food, water => involuntary response, e.g. drooling
* conditioned (2nd) reinforcer, e.g. clicker, hence why this makes training work better

easier learn + remember response so eventually only need primary cue

308
Q

where do neurone structural changes for memory take place

A

hippocampus in medial temporal lobe
* used to form new memories
* spatial learning tasks but not ‘skills’ tasks

ventral part not visible in coronal cross-section all species
309
Q

where do memories then go for storage

A
  1. factual = -> cortex for long term storage (v long term = temporal lobes)
  2. skills -> basal ganglia, cerebellum + cortex
310
Q

cognitive dysfunction

A

alzheimer’s in animals - canine or feline
-> start pooping in house
-> get stuck in corners

BACE enz causes incr β-amyloid prot = incr phosphorylation of Tau prot = decr memory:
1. neurofibrillary tangles w/in neurons
2. amyloid plaques

311
Q

comparison alzheimer’s humans + dogs

A
  • β-amyloid placques in both
  • neurofibrillary tangles not always in dogs
  • acetylcholine dysfunction in both
  • tau may not be part of it in dogs
312
Q

where are nuclei of CNs generally

A

all in brainstem, except I + II

313
Q

CN I

A

olfactory - sensory only (smell)
* originates olfactory bulbs of forebrain

then:
-> contralateral olf bulb
->contralat piriform lobe
-> piriform lobe
-> limbic sys, hypothalamus + reticular formation

314
Q

CN II

A

optic - sensory only
* from optic chiasm region

-> visual cortices
-> pretectal nuclei for reflex eye movement => CN III + contralat CN III

315
Q

CN III

A

occulomotor - motor only
* somatic to extraocular muscs + levator palpebrae superioris
* autonomic (parasymp) to constrictor musc of iris

optic n. + vestibular nuclei -> midbrain nuclei -> periaqueductal grey matter
* also contralat motor cortex input to grey matt for conscious control

nuclei in midbrain
316
Q

CN IV

A

trochlear - somatic motor only
* to dorsal oblique extraocular

motor cortex + vestibular nuclei => trochlear nucleus
* = conscious control + reflexes for balance

317
Q

CN V

A

trigem
* facial sensation
* motor -> mastication muscs + extensor tympani of ear

contralateral motor cortex -> motor nucleus -> mandib branch (conscious control)

sensory nuclear complex -> motor nucleus of VII (for facial expression) + -> contralat somatosensory cortex (for awareness)

motor nucleus bet pons + cerebellum
318
Q

CN VI

A

abducens - motor only
* somatic motor -> lateral rectus + retractor bulbi

contralat motor cortex + vestibular nuclei -> rostral medulla oblong (nuclei)

319
Q

CN VII

A

facial
* taste rostral 2/3 tongue
* touch of medial pinna
* autonom visceral motor -> salivary glands
* somatic motor ro muscs facial expression + buccinator + caudal 1/2 digastricus

320
Q

pathways of CN VII

A

trigem sensory nuclei + nucleus of solitary tract (for taste) ->
1. contralateral somatosensory cortex for conscious perception
2. reticular formation w autonomic nuclei, cause salivation (also has input from CN V)

contralateral motor cortex + CN V + CN VIII -> rostral med oblong for motor output

321
Q

CN VIII

A

vestibulocochlear = sensory only

2 sets nuclei:
1. spiral ganglion -> cochlear nuclei in med oblong -> pons (olivary complex) + midbrain (caudal colliculus) -> auditory cortex for awareness (L = sequential pattern, e.g. speech; R = tonality)
2. vestibular ganglion -> vestibular nuclei ventral to cerebellum ->
* spinal tracts
* CN nuclei for reflexes, e.g. air movement
* cerebellum to refine motor movement
* contralateral somatosensory cortex for perception of balance
* vomiting centre

322
Q

CN IX

A

glossopharyngeal
* taste caudal 1/3 tongue
* pharyngeal + middle ear sensation
* bp info from baroreceptors at carotid sinus
* visceral efferent to salivary glands
* somatic motor to pharyngeal + laryngeal muscs - swallowing

IX, X + XI exit in same bundle
323
Q

pathways CN IX

A

nucleus of solitary tract (taste component)
-> contralat somatosensory cortex for perception
-> nucleus ambiguus (w contralat mmotor cortex input) for motor reflexes
-> motor + autonomic nuclei of other CNs for reflexes
-> lateral brainstem w autonomic nuclei for salivation in response taste

324
Q

CN X

A

vagus
* taste from root tongue
* sensation from viscera, external ear canal, pharynx, larynx
* motor autonom (parasymp) -> viscera
* somatic motor -> pharyngeal, laryngeal + oesophageal muscs

325
Q

pathways CN X

A

nucleus of solitary tract
-> contrtalat somatosensory cortex
-> motor + autonom nuclei other CNs for reflexes
-> nucleus ambiguus (w input contralat motor cortex bc conscious movement) for motor
-> lateral to 4th ventr where autonomic nuclei sit

326
Q

CN XI

A

accessory - motor only
* to larynx + muscs of thoracic girdle

nucleus ambiguus -> CN X AND -> C7 for neck/shoulder muscs

327
Q

CN XII

A

hypoglossal - motor only to tongue muscs

contralat motor cortex AND other CNs for reflexes (e.g. withdrawal) –> caudal medulla oblongata

nucleus in caudal med oblong
328
Q

generally where do diff nuclei types sit

A

motor nuclei = ventral
autonomic efferent = lateral
sensory = dorsal

329
Q

when do we not do CSF tap

A

if risk of high press in brain, e.g. oedema w lesion
* stick needle in = release press = risk herniation into brainstem

330
Q

stages of neurological exam

A
  1. mentation (general being, behaviour)
  2. posture
  3. gait
  4. postural reactions
  5. spinal reflexes
  6. cranial nerve assessment
  7. palpation
  8. nociception - pain responses

1st 3 hands off bc once start pain etc general stuff will change

331
Q

how do we test conscious proprioception

A

paw replacement test for paw righting reflex
* = lift paw, place on dorsal surface, should move it back
* don’t lift too far or lose balance + testing subconscious proprioception

332
Q

testing subconscious proprioception

A
  1. paper under paw + drag it outwards - dog should bring foot back to retain postural frame
  2. hopping test = 1 leg held up + pull bod to other side - even hopping both ways? (also lil bit conscious bc moving -> 1 side = paw slightly rolling -> 1 side
  3. wheelbarrow test (subtle deficits) - testing strength asw (don’t if spinal injury poss bc damage)
333
Q

jumping on + off box test

A

needs coordination + balance + strength etc - looking for subtle deficits

334
Q

testing withdrawal reflex

A

pinch paw + should withdraw leg - testing sensory + motor

335
Q

cutaneous trunci reflex

A

using dermatomes - gentle pinching caudal -> cranial - shld cause cut trunc musc under skin contract lil bit

336
Q

perineal reflex

A

gently irritate perineal region -> musc contraction + twitching tail
* no = damage S1 - S3

perineum = region bet genitals + anus

337
Q

menace reflex

A

poke in eye/waft air towards eye -> close eyelids
* cortical nerve from telencephalon

338
Q

testing vestibular function

A

move head side to side + look for normal physiological nystagmus (vestibulocochlear input)

339
Q

once localised lesion, next steps?

A
  1. bloods: haemotology (testing bcs), endocrine testing (hormones), serology (for antibodies), toxicology (for toxins)
  2. urine
  3. ultrasound of abdom if non-CNS or eye for retina, rostral optic nerve + retrobulbar area
  4. radiography - plain, e.g. look for osteoarthritis as cld affect results/contrast die in subarach space + highlight lesions
  5. fluoroscopy = lots radiographs for moving image - see dye moving thru = see blockage
  6. computed tomography = lots radiographs together from diff angles
  7. MRI - more detail of lesion, but more spenny
  8. CSF sampling
  9. pharmacological testing, e.g. myesthenia gravis w acetylcholinesterase - if temp fixes then diagnosed
  10. electrical testing

to identify disease process

340
Q

why CSF tap b4 contrast study radiography

A

otherwise just get sample of dye

341
Q

types electrical testing

A
  1. electroretinogram - check if eye visual behind cataract b4 surgery to fix
  2. electromyography - direct stim musc to see if motor working (if get response)
  3. test hearing
342
Q

what structures make up limbic sys

A

hippocampus, amygdala, hypothalamus, cingulate gyrus

343
Q

amygdala does?

A

involved in fear responses

344
Q

label

A
345
Q

neurons

A

receipt, generation, conduction + transmission of stimuli as electric signals (waves of depol)
* large nucleus w prominent nucleolus
* soma/perikarion w prominent RER
* multiple dendrites receiving info from adjacent or distant neurons
* single axon projecting signal from soma -> effector cell

346
Q

astrocytes

A
  • create + maintain BBB
  • uptake + recycle NTs
  • maintain extracellular pH + osmotic press (by uptake K+)
  • support metabolic demands of neurons
  • support neuron migration during neurogenesis

protoplasmic in grey matter + fibrillar in white matter

347
Q

oligodendrocytes

A

small cells w round picnotic nucleus responsible production myelin in CNS
* long + complex mem projections compose myelin sheaths + isolate axons

in H&E appear surrounded by clear halo (lipids)

348
Q

microglia

A

macrophage-like cells in CNS for active immune surveillance
* resting = ramified morphology then -> ameboid after activation (rod cells)

349
Q

neuropil

A

space bet neuronal + glial cell bods made dendrites, axons, synapses, glial cell processes + microvasculature

350
Q

label

A
stain => white matter dark blue
351
Q

label

A

middle of gyrus = darker pink = white matter full myelin

352
Q

label

A
353
Q

lateral ventricle lining?

A

ependymal cells

354
Q

spinal cord histology

A

NSF (22 decks)

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