Central Nervous System Flashcards
How does the position of the orbit vary in carnivores and herbivores?
Carnivores- positioned rostrally
Herbivores- laterally
How does orbit construction vary between carnivores and herbivores and why?
Herbivores orbit is enclosed
Domestic carnivores it is open to allow wider jaw opening
What bones make up a dogs orbit?
Frontal Lacrimal Zygomatic Sphenoid Palatine bones Completed by orbital ligament
How does enclosed orbits structure vary?
The frontal process of the zygomatic bone and zygomatic process of the frontal bone meet and complete orbit
What are the foramina in a dogs eye for?
Ophthalmic artery/vein
Cranial nerves- II, III, IV, VI
What lines the orbit?
Orbital fascia, three layers
What are the three layers of orbital fascia?
Outer periorbita (encloses eyeball and associated muscles, nerves and vessels) Fascia bulbi (surrounds globe itself) Fascial sheaths (continuous bulbi)
What are all the extra ocular muscles?
Dorsal rectus Dorsal oblique Ventral rectus Ventral oblique Lateral rectus Medial rectus Retractor bulbi
What is the innervation and action of the dorsal rectus?
Rotate eye upwards
Innervated by III
What is the innervation and action of the dorsal oblique?
Rotate dorsal globe medially and ventrally
Innervated by IV Trochlear
What is the innervation and action of the ventral rectus?
Rotate eye downwards
Innervated by III
What is the innervation and action of the ventral oblique?
Rotate globe medially and ventrally
Innervated by III- oculomotor
What is the innervation and action of the medial rectus?
Rotate globe medially
Innervated by III
What is the innervation and action of the lateral rectus?
Rotates globe laterally
Innervated by VI abducens
What is the innervation and action of the retractor bulbi?
Retracts globe into orbit
Innervated by VI- abducens
What species do not possess a retractor bulbi?
Birds and snakes
What is the name for the dysfunction of one or more extra ocular muscle?
Strabismus
What is the name for a strabismus when eyes are pointing to the side, rotated, cross eyed?
Ventrolateral strabisimus- pointing to side
Extorsional strabismus- rotated
Medial strabismus- cross eyes
What are the functions of the eyelids?
Protect the eyeball
Spread the tear film
Help to remove foreign material
Close to exclude light
What is the name for when they eyelid opens after being born?
Palpebral fissure
What are the eyelids made up of?
Thin folded skin
Haired skin on the outside and mucous membrane on the inside
What is the lid margin of the eyelid?
Transition between skin and conjunctiva
Hairless, upper part posses cilia
What support the lid margins?
Tarsal plate
Where do the upper and lower eyelids meet?
Medial and lateral canthus
How are the medial and lateral canthus secured to the bone?
Canthal/palpebral ligaments
In dogs retractor angli oculi replaces lateral ligament
What muscle causes the closure of the eyelids?
Circular orbicularis oculi muscle - facial nerve
What muscles lifts the upper eye lid?
Medial levator anguli oculi
Levator palpebrae superiosis- occulomotor
What is the sclera?
Whites of the eyes
What sensory innervates the eyelids?
Trigeminal
Opthalmic- upper and medial lower
Maxillary lower
Why are brachycephalic breeds prone to exposure keratitis?
Unable to close eyes properly
What is entropion and ectropion?
Entropion- inward rolling of the eyelids
Ectropion- outward rolling making tear spreading ineffective
What is the conjunctiva of the eye?
Thin highly vascular translucent muscled membrane which lines the inside of the eyelids
What are the different regions of the conjunctiva and what do they form?
Palpebral conjunctiva
Nicitating conjunctiva
Bulbar conjunctiva
Forms conjunctival sac
What part of the tear film does the conjunctiva produces and with what cells?
Contains lots of goblet cells which produce mucus portion of tear film
What is underneath the stratified squamous of conjunctiva?
CALT
Conjunctiva associated lymphoid tissue
What is the nicitating membrane?
Relfection of the conjunctiva containing T shaped cartilage
What part of the tear film does the nicitating membrane produce?
Produces a lot of the aqueous portion of the tear film
Where do tears empty on the bulbar aspect?
Conjunctival sac
What lines the conjunctival sac?
The preocular tear film
What are the three portions of the tear film?
Lipid, mucin and aqueous
What produces the lipid portion of the tear film?
Meiobomian glands- reduces evaporation
What produces the mucin portion of the tear film?
Goblet cells- stabilises
What produces the aqueous portion of the tear film?
Lacrimal gland and third eyelid- lube protection and nutrition
What controls tear secretion?
Autonomic control of lacrimal nerve (ophthalmic)
How is the tear film distributed?
Blinking
How do tears drain?
most drain into nasolacrimal system
Excess collect in lower conjunctival sac and blinking pumps them towards lacrimal punctate
Where are lacrimal punctate present?
Upper and lower eyelids
How d the lacrimal punctate pump tears into lacrimal sac?
Muscle encircles them which constrict the canaliculi during blinking- pumping into lacrimal canaliculi and lacrimal sac, empties into nasolacrimal duct
What are the three layers of the globe itself?
fibrous layer
Uvea
Neural
What is the function of the fibrous layer?
Supports the eyeball shape
What is the function of the Uvea?
Provides nutrition to the structures of the eye and acts to alter light transmission
How is the globe internally divided?
Anterior and posterior segments by position of the lens
How is the anterior segment divided?
Anterior/posterior by the iris
What is at the back of the anterior segment of the anterior segment?
The lens
What is the cornea?
Curved rostral surface of the eyeball which transmits and refracts light
What makes up the cornea?
Anterior epithelium which is squamous at the outside and columnar at base, linked to middle stroma by fine fibrils
What is the stroma and what is it made up of?
Main body of the cornea- consists of carefully arranged collagen fibrils with some keratocytes and a a ground substance of proteoglycans and GAGs
How is the cornea clear?
The arrangements of fibrils with the lack of corneal blood vessels give the cornea its clarity
What underlies the stroma?
The descemets membrane produced by the endothelium
What is the name for where the sclera meets the cornea?
Corneoscleral limbus
What is the name of the perforated zone where the optic nerve exits the eyeball?
Lamina cribosa
Why can the sclera sometimes appear blue and yellow?
Blue- where the sclera is thin
Yellow- hyperbillirubinaemia
How does the sclera receive blood?
The sclera has a superficial vascular plexus which anatomises with the anterior ciliary arteries and drains through the venous plexus in the mid sclera
What us the outer layer of the sclera called?
The episclera is a highly vascular fibroelastic tissue
What is on top of the episclera?
The bulbar conjunctiva
How is corneal injury repaired?
Stem cells in the limbus are recruited
What does the uvea consist of?
The iris the ciliary body forming the anterior urea and the choroid forming the posterior uvea
What is the most rostral part of the uvea?
The iris which forms a ring (the pupil)
What is the iris and what does it do?
A sphincter which constricts and dilates to vary the amount of light
What are the two zones of the iris?
The centrally papillary zone and the peripheral ciliary zone separated by the collarette
What kind of muscle constricts the iris and what innervates it?
The constrictor muscle is smooth muscle sphincter- oculomotor nerve
What kind of muscle dilates the iris?
Single smooth muscle layer extending from the sphincter to the periphery of the iris
What is posterior to the iris?
The ciliary body
What is the ciliary body made up of?
The ciliary process, the ciliary body angle, and forms part of the iridocorneal angle
What is the function of the ciliary body?
Produces aqueous humour, involved in its drainage, anchors the zonnular fibres which anchor the lens
What covers the ciliary body?
Two layers of epithelium, inner non-pigmented and outer pigmented
What forms the blood: aqueous barrier and how?
The non-pigmented epithelium via tight junctions between the cells
How is the ciliary body divided?
Pars plicate and posterior pars plana
What is the pars plicata made up of?
Consists of many ciliary processes which increase the SA for aqueous production
What suspends the lens?
The zonular fibres
What is the most anterior part of the ciliary body?
Iridocorneal angle
What is the iridocorneal angle made up of?
Where the root of the iris, the anterior ciliary body and the corneoscleral junction meet
What happens at the iridocorneal angle
Main site of aqueous humour
What is the choroid?
The uveal layer between the sclera and retina
Heavily vascular and pigmented and consists of several layers
What are the layers of the choroid?
Suprachoroidea, large vessel layer, medium vessel later, choriocapillaris
What are the functions of the different layers of the choroid?
Suprachoroidea- transition between sclera and choroid
Large vessel layer- contains venous plexus, mainly consisting of veins, cools the eye
Medium vessel layer- contains tapetum lucidum (cats eye) increases night vision
Choriocapillaris- innermost later, supply the retina
What is the corneal response to injury and the end result?
The keratocytes are capable of transforming fibroblasts to replace collagen in an injury, the resulting scar tissue lacks the organisation and hence the clarity
What does the anterior segment contain?
Aqueous humour
What is aqueous humour?
An ultra filtrate of plasma which is produced by the ciliary body
What is the function of the aqueous humour?
Provides nutritional needs of the lens and cornea
How does the contents of aqueous humour vary?
Varies on the needs and substances in the blood
Why is the aqueous humour so important?
For the lens and cornea and necessary for intraocular pressure
What happens is production of aqueous humour is in excess of drainage?
Glaucoma
What are the three processes aqueous humour is produced?
Diffusion
Ultrafiltration- hydrostatic pressure
Active secretion- active transport by non-pigmented ciliary epithelium
How does bicarbonate enter the aqueous humour?
Via carbonic anhydrase reaction in the ciliary body
How can bicarbonate provide a treatment of glaucoma?
Affects Na movement and therefore water transport
Describe the circulation of aqueous humour
Circulates from the posterior chamber to the anterior and circulates within anterior due to temperature differences, drains out anterior chamber via the iridocorneal angle
What in the iridocorneal angle does humour drain out of?
Pectinate ligament and ciliary cleft
What is vitreous humour and what does it do?
Hydrogel that transmits light, fills the posterior segment of the globe, and gives support
Provides storage of nutrients and waste products for the retina
What sits on the the anterior face of the vitreous?
The lens
What sites behind the iris?
The lens
Describe the structure of the lens?
An acellular capsule, a cortex of lens fibres and a central nucleus
Where do zonular fibres run from and to?
From the ciliary process to the lens capsule
What is nuclear sclerosis?
The central nucleus of the lens becoming larger, denser and stiffer with age
How does the lens obtain nutrients and remove waste products?
Aqueous humour
What are cataracts?
Deposition of lens protein or accumulation of vacuoles due to changes in aqueous humour
What is the fundus?
The posterior segment which is viewed with an ophthalmoscope
What are the visible structures of the fundus?
Optic disc, the retina, RPE, choroids and sometimes the sclera
What is the outermost layer of the retina and what is the innermost made of?
Outermost is the RPE
Innermost is aeons of the ganglion cells
When do the axons from the retina become myelinated?
After the optical disc
What are Cone and rod photoreceptors for?
Cone- enable colour and sharp activity
Rod-enable shape and motion
Where are cones most numerous in the retina?
Centralis
What is the function of the retinal pigment?
Phagocytoses spent photoreceptor segments
Plays key role in vitamin A metabolism
Moves metabolites in and out the retina
What is a tapetal and where is it found?
Shiny coloured region or pigmented
Found in fundus
What is the name for a retina which receives direct blood flow?
Holangiotic
What is a merangiotic retina and what species have one?
Blood vessels and myelinated course medially and laterally from the optical disc
Rabbits
What is a neurotransmitter?
A chemical that diffuses from the presynaptic from the pre-synaptic membrane to post synaptic membrane
What is the general effect of the following neurotransmitters: Monoamines, Serotonin, Dopamine?
Monoamines- stress
Happiness- Serotonin
Movement- Dopamine
What triggers exocytosis of neurotransmitter?
Influx of calcium ions in the presynaptic membrane
What are the types of calcium channels in the pre-synaptic membrane?
L-type (long acting)
T-type (transient, low threshold, short period)
N-type
How are neurotransmitters inactivated?
Enzyme breakdown and/or reuptake into synapse or glia
Describe how acetyl choline functions as a neurotransmitter and removed?
Vesicles contain acetyl choline Fuse with presynaptic membrane Acts on ion channels in post synaptic membrane Acetyl choline esterase breaks it down Moves back into presynaptic membrane Re-produced and packaged into vesicles
What blocks acetyl choline?
Neostigmine
What are the three main monoamines?
Dopamine, Noradrenaline, adrenaline
How are monoamines produced?
Tyrosine convertes to L-DOPA, precursor for domaine, noradrenaline and adrenaline
What is tryptophan?
Precursor for serotonin
How do monoamines function as neurotransmitters?
Binds to receptors on post-synaptic membrane
Monoamine uptake transporters moves them back into presynaptic membrane
Oxidises then repackaged and reformed in vesicle
What are the main exitatory and inhibitory neurotransmitters of the brain?
Glutamate is exitatory
GABA in inhibitor
What is the action of an inhibitory neurotransmitter?
Reduces the chance of threshold
What is the difference between inotropic and metabotropic receptors?
Inotropic- fast ligand gated receptors
Metabotropic- slower G-protein coupled
How can transmitters be inotropic and G-protein coupled receptors?
Can be exitatory for one and inhibitory for another
What is the action of a neuropeptide?
Produced at the top of the neutron and transported all the way down to the presynaptic membrane
What is the fastest type of synapse?
Electrical synapse
What are the two types of summation?
Temporal- time summation- several impulses from one neurone
Spatial- two neurons fire to reach threshold
What is negative summation?
One neurone and neurotransmitter cancels the other
What are astrocytes?
‘Clean up’ neurotransmitters, take them up and ‘detoxify them’ mainly GABA and glutamate
What is nociception?
Pain
What is a polynomial nociceptor?
A bare nerve ending that detects pain
How are polynomial nociceptors activated?
Mechanical ion channels with movement
Chemical ion channels with chemicals
What are TRP channels?
Transient receptor potential channels
What stimuli do TRP channels detect?
Acid, hot, cold, bumps, inflammation
What is the definition of nociception?
Sensing a stimulus which would be expected to invoke pain
Order the nerve fibres from fastest to slowest: C-fibres, A-delta, A, alpha, A beta?
A alpha
A beta
A delta
C-fibres- unmylinated
What is unusual about primary nociceptor afferents?
Often superficial
Lighter myelination
Thinner
Different NaV channels
What is the pain gate?
When pain can be prevented in fight and flight
What are the two ascending pain pathways?
Ventrolateral and Spinocervicular
What are the two pathways which make up the ventrolateral ascending pathway?
Spinothalamic tract
Spinoreticular tract
Describe the pathway of the spinothelmic tract and what pain does it detect?
Spine directly to thalamus- pin prick and thermal stimuli
What is the overall spinoreticular tract and what type of pain does it detect?
Spine to reticular formation (then thalamus)
Detects true pain
Which ascending pathway has a direct contact with the vomit centre?
Spinoreticular
What does the spinocervical tract detect, describe its pathway?
Detects touch, pin prick, fleas
Tract ascends in lateral funiculus
At C2 it synapses, crosses spinal cord to thalamus sub nuclei
Passes through medial lemniscus in the midbrain
What is the triple lewis response?
Pain oedema and flare from several branches of the sensory nerve and one action potential causing several responses
What is an example of referred pain?
Heart attack in the arm
Where is the cerebellum found?
Sits caudal to the cerebral hemispheres and dorsal to the brain stem
What does arbor vitae mean?
Tree of life
What is the main over all function of the cerebellum?
Compares intended movement with the movement which actually overs and minimises the difference
What is immediately ventral to the cerebellum?
The 4th ventricle
What are the three lobes of the cerebellum?
Rostral (anterior), Caudal (posterior) and flucculonodular
What is found in between the two lateral hemispheres of the cerebellum?
A narrow central vermis
Describe the structure of the grey and white matter in the cerebellum
Grey folded into many folia
White forms a tree appearance
What does the white matter of the cerebellum consist of?
Purkinje cell axons which synapse on deep cerebellar nuclei of grey matter
Describe the pathway of grey matter
Grey matter communicates with other CNS structures bilaterally with three stalks of white matter called peduncles
How many peduncles are there and what are they called?
6 in total 3 each side
Rostral, middle, caudal
What structure do the cerebellar peduncles contribute to?
Form the roof of the 4th ventricle
What do the caudal cerebral peduncles contain?
Afferent fibres carrying sensory information from vestibular organs and proprioceptors to the cerebellum
What do the middle cerebral peduncles contain?
Afferent fibres brining information on intended movements originating in the motor cortex and travelling via the pontine nuclei to the cerebellum
What do the rostral cerebral peduncles contain?
Efferent fibres, cross to form an X at the caudal colliculus to run it the contralateral red nucleus in the midbrain and the thalamus from the cerebellum
What is the generic function of the rostral, middle and caudal peduncle?
Middle- shared information about where the whole body is
Rostral- plans movements
Causal- share information about balance and proprioception
What does the size and shape of the cerebellum correlate too?
The type of movement and posture of the animal
What movements do animals with a well developed spin-cerebellum and small cerebral hemispheres rely on?
Animals who rely on axial muscles and symmetrical or absent limb movements
What do animals with tails have present on their cerebellums?
A large lobule on the rostral end of the cerebellar called the lingula
What is the function of the cerebellum?
Coordination, refinement and correction of movement
What are the two main sets of afferent axons in the cerebellum?
Mossy and climbing fibres
How do the afferent axons travel?
Via the caudal and missile cerebellar peduncles
What do most fibres carry input from?
Motor nuclei in in the pons
What do climbing fibres carry input from?
Vestibular organs and proprioceptor
What do both fibres cause in the cerebellum?
They exited the cerebellar cortex and deep nuclei
How do deep nuclei increase motor function?
Deep nuclei have excitatory output from the upper motor neurone tracts
How is output of the cerebellum modulated?
Modulated by the inhibition from the purkinje cell axons from the cerebellar cortex
Where do corrective signals of the cerebellum travel?
Via the thalamus and brain stem upper motor neurone nuclei
What does the flucculondular coordinate?
Coordinates balance and eye movements in response to vestibular and visual systems
Where does the output of the fluccondular go and what does it influence?
Goes directly to vestibular nuclei in the brain stem
Influences the vestibulospinal tract- motor nuclei for CN III, IV, VI for extraocular muscles and CN XI for neck
Where is the spinocerecellum?
Medial cerebellum extensors into vermis
What does the spinocerebellum coordinate, where does the output go?
Coordinates muscle tone and movement in response to vestibular, visual, auditory and proprioceptive input
Output via deep cerebellar nuclei to upper motor neurone nuclei
What does the cerebrocerebrum coordinate and what is its output?
Coordinates planning of limb movements
Input from motor and somatosensory cortices via the corticopontine cerebellar system
Output to motor cortex via thalamus
What is ataxia and what would cause it?
Ataxia is an uncoordinated gait and poor balance
Inability of the vestibulo and spinocerebellum to coordinate balance and movement
What would a lesion in the vestibulocerebellum cause?
Swaying and falling to the side
How does a neonates brain develop?
The number of neurones doesn’t increase but myelination increases and dendrites increase in number and number of synapses increase
What is developmental learning?
Development of synapses due to the external environment
What processes are involved in brain maturation?
Mitosis, apoptosis of neurones, development and pruning of synapses
What are sensitive periods of development?
Certain times during development in which the nervous system is affected by developmental learning
These periods vary in species
What is an example of a sensitive period of development?
Socialisation periods- if first contact occurs after this the animal will respond with fear
What is fully developed after sexual maturity?
The sensory and motor cortices are fully developed
What is the definition of learning?
The acquisition of abilities or knowledge and is displayed in change in behaviour which occurs as a consequence of experience
What is required to translate learning into a change in performance?
Motivation
What are the two types of memories?
Declarative (facts), Procedural (how to)
What are the two stages of memory?
Short and long term memory
How long does short term memory last if not consolidated to LTM?
Seconds to hours
How long does LTM last?
Days to years
What does memory formation require?
Neural changes called memory traces
What is the difference between STM and LTM?
STM memory traces are electrical only
LTM involves a physical change- formation of new synapses, growth of dendrites
Which regions of the brain are needed for memory traces?
Hippocampus- consolidation of LTM
Cerebellum- storage of procedure
How is a LTM made?
Formation of a memory if attention is paid to the sensory experience leading to a STM
If STM is practiced it leads to LTM
Why is forgetting a LTM described as transient?
Sometimes the brain doesn’t find it (spongebob movie)
What orchestrates the comparison of current sensory data and stored knowledge?
Prefrontal cortex
What are the two types of non-associative learning?
Habituation and sensitisation
How do habitation and sensitisation differ?
Habitations natural response to stimuli reduces over time
Sensitisation of the natural response to stimuli increases over time
What causes either habitation or sensitisation to occur?
Depends on the context and the physiological and emotional state of the animal
What are the two types of associative learning?
Operant conditioning and classical conditioning
How does associative learning differ to non-associative?
Associative is more complex and require STM processing before learning is stored in LTM
How does operant and classical conditioning differ?
Operant- animal learns to associate behaviour with outcome
Classical- animal learns to associate two stimuli that produce a desirable behaviour
What is an example of operant and classical conditioning?
Operant- result of ones actions- barking for biscuits
Classical- pairs a conditioned stimulus such as a clicker with unconditioned stimulus treat
What is cognitive dysfunction syndrome?
The loss of cognition- ability to think and process information, manipulating knowledge through learning memory and planning
What are the signs of cognitive dysfunction syndrome?
DISHA
Disorientation, interaction and social behaviour changes, sleep wake cycle alterations, house soiling and activity level changes
What are the neuropathological changes of CCD?
Brain atrophy, senile plaques, oxidative damage, neurofibrillary tangles
What happens from brain atrophy?
Widening of sulci, thinning of gyri, dilation of ventricles
What are senile plaques?
Abnormal accumulation of proteins with and around neurones, impairs synaptic function
What is oxidative damage?
Oxidative damage to proteins, lipids and nucleotides in neurones affect their functions
What is a common sign of CCD?
An aggressive animal that was previously non-aggressive
Where is the hypothalamus found?
Sits in the diencephalon
What is the hypothalamus vaigly made of?
Collection of nucleuses
What are the key functions of the hypothalamus?
Regulation of hormones Fight or flight response Arousal Sleep-wake cycle- circadian rhythm Regulation of blood volume and thirst Regulation of appetite
What nuceli are found in the middle/caudal region of the hypothalamus?
Lateral hypothalamic area (LHA) Dorsomedial hypothalamus (DMH) Ventromedial hypothalamus (VMH) Arcuate nucleus (ARC)
What nuclei are found in the rostral hypothalamus?
Paraventricular nucleus (PVN) Superoptic nucleus (SON) Superchiasmatic nucleus SCN)
What is the function of the LHA, DMH, VMH, ARC?
LHA- feeding, drinking, arousal, fight or flight, circadian
DMH- Feeding, cardiovascular control
VMH- Feeding, drinking, activity
ARC- feeding
What is the function of the PVN, SON, SCN?
PVN- Feeding, drinking, parturition, cardiovascular control
SON- Drinking
SCN- circadian rhythm
What releases hypothalamus hormones?
Posterior pituitary
How is the hypothalamus involved in the fight or flight response?
Cardiovascular control- changes in blood volume, osmolarity, temperature
How is the hypothalamus involved in the sleep response?
Superchiasmatic nucleus- eye had ganglion in SCN- sends a wake sleep signal, releases melatonin from the pineal gland
What disease is caused if the SCN is compromised?
Narcolepsy
How is an animal woken up?
The SCN sends a neuropeptide signal to dorsal hypothalamus which relates hypocretin to wake up
What does the hypothalamus cause if temp rises and falls?
Temp down- thermogenesis, shivering, adipocyte thermogenesis
Temp up- Switch off thermogenesis, vasodilation, sweating, panting
How is osmolarity regulated by the hypothalamus?
Super optic nucleus releases vasopressin from posterior causing water retention
What nucleus of the hypothalamus is associates with regulation of feeding?
Paraventricular nucleus
What is satiety and appetite?
Satiety- eaten enough
Appetite- needs to eat
What hormones affect which centres and cause appetite and anorexia?
Leptin to satiety centre
Ghrelin goes to appetite centre
What is leptin, where is it produced, what does it cause?
Leptin is a cytokine produced by the obese gene in fat cells, acts on hypothalamus to regulate eating- decreases fat tissue
How does leptin cause inhibit of feeding behaviour?
Induces pro-opiomelanocortin and release of melanocyte stimulating hormone, binds to melanocortin, inhibits feeding behaviour
Leptin acts on the ARC which either stimulates of inhibits feeding via the LHA and PVN
What is the lipostat theory?
Leptin regulation of long term control of appetite
What is the glucostat theory?
Short term appetite regulation- glucose rises, hunger falls and opposite
Detected in PVN
