NEU 4 Flashcards
Outline what is meant by a spinal segment and how this can be used to localise a lesion.
- Spinal cord segments do not line up with the segments of the vertebrae
- The nerve apears caudal to segment, as has to get through the intervertebral foramen
- e.g. L7 is attached to the L7 segment of SC
- This can be used to localise a lesion as there will usually be pain over lesion
- Can work out which muscles have atrophied and what their roots are, this can then show the approximate location of the lesion
Which spinal nerves supply the forelimb?
C6 - T2
Which spinal nerves supply the hindlimb?
L4 - S3
What clinical signs will be seen if there is damage in the T3 - L3 region in the grey matter?
- UMN symptoms only in the hindlimb
Describe the structure and function of the cranial cavity.
- Lined by periosteum and dura mater (fused in cranial cavity)
- Cranial vault separated into 3 compartments by dura fold: falx cerebri, tenorium cerebelli, diaphragmasellae
- 9 main foramina - all bar one are for nerves (carotid canal is for carotid artery)
- Tentorium cerebelli separates cranial and caudal fossa
- Hypophyseal fossa for pituitary gland
Describe the strcutre of the wall of the skull
- Outer and inner cortical layer of bone
- Middle layer has reduced spongiosa
- Called diploe (weight saving)
- Surface covered by periosteum
List the foramina of the skull in order, rostral to caudal
- Cribriform plate
- Optic canal
- Orbital fissure
- Foramen rotundum
- Oval foramen
- Carotid canal
- Internal acoustic meatus
- Jugular foramen
- Hypoglossal canal
Explain the difference between vomiting and regurgitation.
- Regurgitation: food has never reached stomach
- Vomiting: forceful expulsion of the stomach contents through the oesophagus and through the mouth
Explain the clinical signs associated with feline dysautonomia with reference to the ANS
- Key-Gaskell syndrome
- Raised temperature, low heart rate, dry crusty nose, no PLR, dry mucous membranes, normal CRT, hard faeces in colon, full distended bladder
- Marked reduction in number of neurones in autonomic ganglia, brainstem and cranial nerves
Describe ways of treating cats with feline dysautonomia
- IV fluids
- Antibiotics
- Paraffin enemas to releive consipaation
- Empty bladder (cystocentesis)
- Metoclopramide (improve gastric motility)
- Pilocarpine for eyes
Describe ways in which the autonomic nervous system can be manipulated pharmacologically and the physiological consequences of these manipulations
- Administration of epinephrine - agonsit to alpha and beta receptors so increases heart rate, contractility and vasoconstriction
- Parasympathetic agonsits to inrease gut motility, watery secretions, decrease heart rate, stimulate vasodilation
- Anticholinesterases: increase ACh levels in a synapse which then compete with a blocker (e.g. neostigmine)
- Parasympathetic antagonist (atropine) acts to increase heart rate by reversing heart blodk caused by increased tone in the vagus nerve
At what points may the ANS be manipulated by the use of drugs?
- Synaptically: prevent break down and reuptake of NT or increase the break down and reuptake of an NT before can reach the other side
- Postsynaptic membrane: prevent binding with receptors by using a blocker, or increase binding by increasing NT available, or blocking enzymes that break down NT to maintain action potential propagation for longer
Give examples of TSEs
- Scrapie: sheep
- BSE: bovine spongiform encephalitis
- Kreutzfeld-Jakob syndrome: humans
Discuss the role of prions in the development of TSEs.
- Prions are derived from normal, native glycoproteins = PrPc
- PrPSc = the abnormal scrapie prion protein
- The PrPc is required for the development of TSEs
- There are species barriers because of this - different species do not always share the same glycoproteins
- Different strains can develop
- The species barrier can be overcome
Describe the clinical signs caused by TSEs
- Abnormal behaviour
- Aggression
- Hypersensitivity to touch, sound, visual stimulation
- Abnormal locomotion (ataxia)
- BSE specific: high stepping, excessive nose licking, reduced milk yield, weight loss, downer cow
- Scratching in scrapie
Describe the pathology of TSE and the current diagnostic procedures
- Primary site for pathogenic prions is in the obex
- Vacuolarisation in infected brain tissue (white gaps where there shouldn’t be any)
- Definitive diagnosis can only be made by demonstrating the presence of prion protein
- Can be done by transfer of brain extract to permissive experimental animal (ethical issue, long incubation period before diagnosis, costly)
- Specific identification of the PrPSc (disease specific protein)
- Rapid screening test: protease treatment prior to tests and then PrPSc purified and detected by ELISA
- Western blotting: detect PrPSc protein by molecular weight and rection to antibodies
Explain the economic impact of TSEs in the UK
- Stock restrictions if TSE detected. Suscpetible stock must be culled (all goats, sheep with susceptible genotype)
- Slaughtered stock may or may not be able to enter the food chain depending on genotype
- Tests can be costly
Explain how TSEs can be transmitted
- Ingestion of PrPSc contaminated feeds (previously meat and bone meal prepared from slaugher offal - now banned)
- Horizontal transmission during perinatal period (milk has high level of infectivity, placental material from scrapie infected ewes may play important role, not seen musch in cattle)
- Superficial abrasions
- Environmental factors (last a long time in the environment, but not a prathway for infection in cattle)
Explain how PrPScs may get to the brain
- 3 proposed pathways (but pooly understood)
- Parasympathetic fibres of the vagus: bypasses spinal cord, innervates viscera of head, neck, thorac, abdomen, originates in medulla oblongata
- Splanchnic nerve sympathetic trunk: enteric plexus -> prevertebral ganglia -> splanchnic nerves -> sympathetic trunk -> spinal cord -> brain
- Sympathetic and vagosympathetic trunk: sympathetic trunk -> cervicothoracic ganglion -> ansa subclavia -> vagosympathetic trunk -> brain
Discuss the transmission risk of TSE in the context of public health
- Can be spread by puncture contact or ingestion
- Long survival time in soil
- Ban on feeding mammalian meat and bone meal
- Prevent risk of material entering food chain (suspect animals and their products
Describe the pattern of the development of the cerebellum
- Upward growth of alar lamina of hindbrain
- All neurones association in type - no efferent motor neurones
- Initllay has the mantle zone (cellular) which is deep and grey matter and the marginal zone fibrous) which is superficial and white matter
- Later some mantle zone migrates to surface becoming cerebellar cortex - becomes white matter
- Remainder stays deep forming cerebellar nuclei
- Paired upgrowth from the future pons part of the hindbrain
- fuses into single cerebellum
Describe the general anatomy of the cerebellum
- Cerebellar cortex: fissures on surface divide into lobules and further subdivison into folia
- White matter: fibres running to/from cortex (arbor vitae)
- Cerebellar nuclei: 3 on each side, from lateral to medial: dentate, interpositus and fastigial
- All of it is grey matter except the arbor vitae
- Rostal, caudal and flocculonodular lobes
Describe the relations of the cerebellum to other parts of the brain
- Sits dorsal to pons, medulla oblongata and 4th ventricle
- Attached to the brainstem by peduncles
- 3 pairs: rostral (to midbrain), middle (to pons) and caudal (to medulla oblongata)
Describe the afferent fibres found in the cerebellar cortex
- Mossy and Climbing
- Mossy synapse to granular cells and on way to crotex synapse with deep cerebellar nuclei
- Climbing connect to Purkinje cells in molecular layer and also connect to deep cerebellar nuclei (output)
Describe the location function of the Purkinje cells in terms of the cerebellum
- Are the only efferent cells of the cerebellum
- Project to the deep cerebellar nuclei and from there to other parts of the CNS as final target outside teh cerebellum
- Are inhibitory
- EXCEPTION: connection from cerebellum to vestibular system is a direct connection, does not require nuclei
Describe the topography and main subdivisions of the diencephalon
- Midline part of forebrain
- Rostral to midbrain
- Medial to cerebal hemispheres
- Subdivisons: epithalamus, thalamus and hypothalamus
Describe the structure and function of the epithalamus
- Most dorsal portion of diencephalon
- Contains some small nuclei and their connections
- Contains the pineal gland - endocrine function
Describe the structure and function of the thalamus
- Largest part of diencephalon
- Wakefulness
- Right and left thalami project medially to come together and form the interthalamic adhesion
- General and special sensory information relays through appropriate groups of thalamic nuclei
- Special through geniculate nuclei
- Feedback from cortex to the rest of the brain
- Have specific and non-specific nuclei
- Specific: well defined sensory and motor functions, highly organised point-to-point connection with sensory and motor regions of cerebral cortex
- Non-specific: receive less functionally distinct afferent input, connect with wider area of cortex, including associative and limbic regions
List the specific nuclei of the thalamus and where they go
- Lateral geniculate nucleus: from eye to primary visual cortex
- Medial geniculate nucleus: from inner ear to primary auditory cortex
- Ventrolateral: from cerebellum to primary motor cortex
List the non-specific nuclei of the thalamus and where they go
- Intralaminar: diffuse projections to much of the cortex
- Midline
Describe the structure and function of the hypothalamus
- Lies below thalamus and forms ventral part of diencephalon
- Exposed on ventral surface of brain
- Largely used for survival
- Optic chiasm gives attachment to optic nerve
- Tuber cinereum gives attachment to infundibulum of the pituitary gland
- Mamillary bodies receive inputs from hippocampus via fornix, relay via mammillothalamic tract to thalamus, function uncertain but usually grouped within limbic system
Describe the location and general function of the pineal gland
- In epithalamus
- Just above the interthalamic adhesion and behind the third ventricle
- Endocrine gland
- Produces melatonin and plays a role in circadian and seasonal rhythms
Describe the location and main parts of the pituitary gland and their main functions
- Just under the hypothalamus in the pituitary fossa
- Has an anterior, posterior and intermediate section
- The posterior lobe: ADH, oxytocin, uterine smooth muscle, mammary gland smooth muscle
- Intermediate lobe: melanocyte stimulating hormone
- Anterior: FSH, LH, ACTH, TSH, GH, prolactin
Give the hypothalamic nuclei.
Paraventricular, supraoptic, suprachiasmatic, lateral, ventromedial, arcuate, mammillary
What is the function of the paraventricular and supraoptic nuclei?
Control oxytocin and ADH production and secretion
What is the function of the suprachiasmatic nucleus?
- Biological clock
- Circadian rhythm
What is the function of the lateral nucleus?
- Arousal/feeding (excitatory, stimulates feeding)
What is the function of the ventromedial nucleus?
- Feeding (inhibitory, reduces feeding)
What is the function of the arcuate nucleus?
Controls energy homeostasis (insulin)
What is the function of the mammillary nucleus?
Wakefulness via histamine
Explain the law of specific nerve energies
- Brain assumes a set of connections with outside world
- Stimulation arriving at the brain si referenced to an internal group
- Accidental stimulation of anerve is interpreted as being due to an external event
- e.g. pressing eyeball to distort retina produces visual flash as brain assumes information in the optic nerve is due to light hitting the retina
Describe the skin mechanoreceptors and their different functions
- Use A-beta nerve fibres
- Ruffini’s end organs detect tension deep in skin
- Meissner’s corpuscles detect changes in texture
- Pacinian corpuscles detect rapid vibrations
- Merkel’s discs detect sustained touch and pressure
- End bulbs of Krause detect slow movement
- Hair follicle receptors detect movement but not sustained pressure
- Each receptor connect to one axon
- Axons are fixed type (A-beta)
- Intensity transmitted by frequency of action potentials
Describe how proprioception is detected
- Use A-alpha nerve fibres
- Joint position - stretch receptors within joint capsule and ligaments
- Tendon tension - golgi tendon organs, stretch receptors
- Muscle tension - muscle spindles, sense rate of change and length, use A-alpha and A-beta
- Feed forward - awareness of where a joint will or should be in advnce of actually attaining the position
Describe pain receptor density
- Specialised nociceptors - not just over stimulation of touch
- Superficial somatic: skin, high density of pain receptors, well localised, rapid sensation
- Deep somatic: tendon, ligament, bone, fascia, low density, dull, poorly localised
- Visceral: guts, can be sharp, tends to be dull, cramping, referral of pain to an area of skin is common
Describe pain transmission
- Fast and slow pain nerve fibres
- A-detla = sharp initial pain
- C fibres = slow, delayed burning sensation (after-pain)
Describe the general pathway of neurones for general somatic afferent information
- Sensory neuron from receptor to CNS. Cell body in dorsal root ganglion
- Neuron inside CNS (SC or MO) transmits information to thalamus
- Neuron in thalamus trnamsits information to somatosensory cortex in telencephalon
Describe the functions of the 3 funiculi in the spinal cord
- Project afferent fibres centrally
- Dorsal: primary afferent axons
- Lateral and ventral: secondary axons from neurons in spinal grey matter
Describe the 3 funiculus options available to afferent fibres
- Primary afferent to dorsal funiculus and out
- Primary afferent synapsing with secondary afferent to lateral funiculus
- Primary afferent synapsing with secondary afferent to ventral funiculus
Describe the function of teh trigeminothalamic tract
- 3 nerves enter brain directly as a single root
- Sensory for head region
- GSA and GPA
- Ophthalmic, maxillary and mandibular divisions
Which tracts are present in the dorsal funiculus?
- Cuneat
- Gracile
Describe the function and position of the cuneate tract inrelative detail
- Sits most laterally in the dorsal funiculus
- Transmits touch and kinaesthetic information from forelimb
- Contains axons which make up spinocuneocerebellar tract
Describe the function and position of the gracile tract in relative detail
- Most medial tract in the forsal funiculus
- Touch and some kinaesthetic information from hindlimb
List the tracts present in teh lateral funiculus and give their function
- Spinothalamic: touch, nociception, temperature
- Spinocervicothalamic: dominant nociceptive tract in carnivores
- Dorsal spinocerebellar: muscle spindles, tendon organs, joint receptors, skin
- Spinomedullary: muscle spindles, tendon organs, joints caudal o thoracic limb, axons go to nucleus Z
- Ventral spinocerebellar: conveys information about motor neuron state directly to cerebellum
List the tracts inteh ventral funiculus and give their functions
- Spinoreticular: nociception, mechanoreception, involved in motivation and awareness
- Spinovestibular: proprioception from cervical region
- Spinomesencephalic: nociception, mechanoreception projection to midbrain
- Spinoolivary axons: sensory feedback from olivary nucleus to cerebellum, fibres travel in several other tracts
Describe the role and location of the somatosensory cortex.
- Site of perception of the general senses
- Parietal lobe, caudoventral to coronal sulcus
- Information relayed contralaterally
- Arrangement within general sensory cortex is highly organised
Outline how conscious sensation occurs and is transmitted.
- Projections from thalamus to telencephalon for awareness of various sensations
- Also fibres from cerebellum to thalamus to coordinate motor responses to sensory input
- Cerebellum takes over to control repetitive motor tasks
Describe the structure of motivated behaviour
- 3 phases
- Orientation, oriented, consumption
- Is a feedback loop (positive or negative depending on stimulus)
- e.g. if an animal is looking for food and continues to find low quality food, the motivation to look for better food will increase
Describe the state-space concept of motivation
- Combined physiological and perceptual state as represented in the brain
- Called motivational state of animal
- Relationship between motivational state and behaviour is not direct as in traditional view
- Combine assumptions of homeostatic models with an explicitly functional approach to mechanisms
Describe the 4 phases of appetitive behaviour
- Phase I: no evidence of stimulus e.g. prey, food (non directed)
- Phase II: stimulus detected (e.g. smell, sight of prey, food) eventually chasing and capturing prey/finding food (directed)
- Phase III: sonsummatory (killing pre, eating)
- Phase IV: satiation
Describe ingestive behaviour in terms of glucostatic and lipostatic theories.
- Homesostatic, negative feedback system regulating feeding
- 2 set points being regulated: blood glucose (short term regulation) and body fat (long term regulation)
- Settling point is a stable state caused by a balance of opposing forces
- ## feeding centre and satiety centre
What are the feeding and satiety centres of the brain, and what happens if there is a lesion in these areas?
- Feeding centre is lateral hypothalamus, lesion leads to starvation
- Satiety centre if in ventromedial hypothalamus, lesion leads to obesity
Where can rete mirabile be found in the blood supply to the brain, what is their function and what are species differences?
- Is an anastomosing ramus
- In sheep and cats - pair of maxillary rete mirabile
- In cattle - maxillary and ventral pairs
- None in dogs and humans
- Cool blood and reduce fluctuations due to pulsatile flow
Where are the ventricles of the brain located
- Lateral: cerebral hemispheres
- 3rd: around interthalamic adhesion
- 4th: in metencephalon under medulla
Between which structures is the interventricular foramen?
3rd and lateral ventricles
What are the functions of CSF?
- Nutrition
- Support
- Protection
- Removing waste
- Preventing ischaemia
What are the modes of cell communication?
- Contact dependent (touching)
- Synaptic (close)
- Autocrine, paracrine, endocrine (widespread/far away)
Briefly outline contact dependent cell signalling.
- Communicate via cytoplasmic bridges
- Allow signalling molecules to pass between cells
- If something is wrong with one cell, will be passed onto another
- Known as gap junctions
- Ions, metabolites and more complex molecules (cAMP)
- Slow transmission across an organ (can only communicate with adjacent cells)
Briefly outline synaptic transmission, including the advantages and disadvantages
- Communication between neurons involving a chemical messenger across a short synaptic cleft
- No dilution in general circulation, system can be reactivated very quickly
- Specific, hardwiring is expensive, possibly vulnerable
What is meant by autocrine, paracrine and endocrine cell signalling?
Autocrine: self signalling
Paracrine: signalling to cell nearby
Endocrine: signalling to a distant cell
Describe the difference between endocrine and exocrine secretion
- Endocrine is into the body interior (directly into blood or tissues)
- Exocrine is into exterior or gut (via a duct)
Describe the regulation of the pineal gland
- Regulated by circadian and seasonal cycle
- Activity inhibited by light
- Activity stimulated by darkness - melatonin release, inhibited gonads and other endorcrine functions
Describe the location of the pituitary gland in relation to the hypothalamus
- From median eminence
- Ventral aspect of hypothalamus from which portal vessels arise
- Is outside BBB
Describe the general structure of the pituitary gland
- Anterior, intermediate and posterior lobe
- Intermediate lobe is made from oral ectoderm derivatives
- Anterior pituitary has few nerves, mainly portal system
- Network of vessels in plexuses increases surgace area increasing transport of hormones
Where are ADH and oxytocin produced?
Produced in hypothalamus (hypothalamus also produces other peptide hormones)
Describe the production and secretion of hormons produced in the hypothalamus (e.g. ADH)
- Peptides synthesised in nerve cell bodies
- Prohormones
- In supraoptic and paraventricular nuclei
- Via axons into posterior lobe (using neurophysins as carrier proteins)
- Stored in nerve endings in the posterior lobe (Herring bodies)
- Action P induce hormone release
- Exocytosed into the blood
Describe the development, structure and function of the posterior pituitary lobe
- Neuroectoderm derivative, downward growth of diencephalon (infundibulum)
- Is part of nervous system and has a neural connection to the hypothalamus
- No hormone producing cells - stores and secretes the hormones produced by the hypothalamus
- Mainly ADH and oxytocin secretion
What is the function of ADH?
- Used in the control of fluid balance
- Increases water retention
- It is released in increased osmolarity of ECF and a fall in ECF volume
- Increases water absoption from the distal tubule and the collecting duct in the kidneys
- Reduces volume and increases concentration of urine
- Interference leads to pooly constituted urine
- If high blood loss, ADH released, retains water, dilutes blood but volume increases
Describe the function of oxytocin
- Important in contraction of uterine smooth muscle (parturition)
- Stimulates mammary gland smooth muscle (milk let down)
Describe the development, structure and function of the anterior pituitary gland
- Develops from anterior wall of Rathke’s pouch
- Has vascular connection to hypothalamus
- Hormones produced in anterior pituitary
- Under hypothalamic control, secreted into portal circulation
- Releasing and inhibitory factors
- Produces: FSH, LH, ACTH, TSH, GH, prolactin
Describe the gross anatomical strucures of the eye of dogs, cats, horses, sheep, snakes and birds
- Dogs: round pupil, upper eyelashes only
- Cats: no lashes, modified guard hairs, vertical slit pupil
- Horse: upper eyelashes, prominent vibrissae, horizontal oval pupil
- Sheep: upper lashes, horizontal oval pupil
- Snake: fused eyelids (spectacle), vertical slit pupil/variable
- Birds: filoplumes (modified feathers as eyelashes), round pupil
Describe the 3 ocular layers of the eye
- Outer: fibrous, provides protection and imparts rigidity to eye, white of eye (sclera) and cornea, cornea is a continuation of the sclera
- Middle layer: vascular, nutrition, uveal tract, choroid, ciliary body, iris
- Inner layer: neural, allows vision, retina and optic nerve
What is the limbus?
The junction between cornea and sclera/conjunctiva
Briefly outline the embyrology of the eye
- Develops from the forebrain
- Develops from 3 tissue types: neuroectoderm, surface ectoderm (becomes internalised in the eye as the lens) and mesoderm
Describe the orbit of the eye
- The cavity within the skull that encloses the eye
- Protection and separating the eye from the cranial cavity
- Foramina within walls of orbit are pathways for blood vessels and nerves to reach the eye
What are the 2 types of orbit present in domestic species
- Open/incomplete
- Closes/complete
Describe open/incomplete orbits and what species they are found in
- Lateral wall is soft tissue not bone
- Facilitates wide opening of the jaw (to catch prey)
- Carnivores (dog, cat) and pigs
Describe complete/closed orbits and what species they are found in
- Lateral wall is bony
- Protection for fighting
- Herbivores (horse, cow, sheep, goat)
Describe the difference in visual fields of predators vs prey
- Predators have frontal orbits - smaller field of vision but more accurate at gauging depth
- Prey have lateral orbits - larger field of vision so can see predators approaching. Almost 360 degree vision
Describe the walls of the orbit
- Medial wall: very thin, underlying ethmoturbinates
- Floor: part bone, part soft tissue, masticatory muscles
- Rostral margin/orbital rim: made up of frontal, lacrimal and zygomatic bones
- Lateral wall in closed: fusion of zygomatic and frontal bones
- Lateral wall in open: lateralorbital ligament - palpate as taut band in live animal
Describe the relationship between the ramus of the mandible and the eye
- When jaw is open, back of jaw can press on the eye
- If have a problem (e.g. tumour) in this area then will be very painful
Describe the foramina of the orbit
- Pathways for nerves and blood vessels to reach orbit from cranial cavity
- 8 different foramina
- Interspecies variation
Name the important orbital foramina
- Optic foramen (CN II and internal ophthalmic artery)
- Orbital fissure (CN III, IV, VI, V ophthalmic branch)
- Round foramen (V maxillary)
- Supraorbital (supraorbital vessels and nerve)
- Ethmodal foramina (ehtmoidal vessels and nerve)
- Rostral alar foramen (V maxillary and maxillary artery)
Describe the arterial supply to the eye
- Main supply for eye is external ophthalmic artery
- External ophth artery arises from internal maxillary artery and external carotid artery
- Optic nerve and retina are supplied from internal ophthalmic artery
- Arises from internal carotid
Describe the venous drainage of the eye
- 2 routes from orbit into orbital plexus: dorsomedial region of eye and ventrolateral region of eye
- 2 routes from orbital plexus: intracranial route and extracranial route
Describe the intracranial route of venous drainage from the eye
- Orbital vein via orbital fissure
- Into cavernous sinus on base of skull
Describe the extracranial route of venous drainage from the eye
- Internal maxillary vein and external jugular vein via facial vein
List the ocular muscles
- Dorsal rectus
- Ventral rectus
- Medial rectus
- Lateral rectus
- Dorsal oblique
- Ventral oblique
- Retractor bulbi
Which extraocular muscles are innervated by cranial nerve III
- Dorsal, medial and ventral rectus and ventral oblique
Which extraocular muscle is innervated by cranial nerve IV
Dorsal oblique
Which extraocular muscles are innervated by cranial nerve VI
- Lateral rectus
- Retractor bulbi
