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The Nervous System

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The Nervous System - including Veterinary case studies
The eye, ear, skin, cranial nerves, nervous systems

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The Nervous System

  1. 1. THE NERVOUS SYSTEM Veterinary Physiology
  2. 2. The Skin The skin is the largest organ in the body and performs regulatory functions, such as thermoregulation, as well as providing protection against: • Surface wear and tear • Invasion against microorganisms • Drying out of the body (desiccation) The skin has three distinct layers… 1. Epidermis 2. Dermis 3. Hypodermis Throughout the epidermis and dermis layers there are hair follicles and oil and sweat glands.
  3. 3. The Epidermis The epidermis is the ‘tough’ outer layer, composed of stratified squamous epithelium. Epidermis Cells • Karatinocytes: produce keratin. Keratin is tough, fibrous and waterproof giving the skin its strength and resiliency • Melanocytes: produces the skins pigment/colour • Merkel Cells: associated with the sensory organs • Langerhans Cells: these cells are macrophage specific to the epidermis and are involved in the immune response
  4. 4. Dermis This is the second, deeper layer of the skin. It is highly fibrous and composed of… • Dense connective tissue • Collagen • Elastin fibres • Hair follicles • Nerve endings • Sebaceous and sweat glands • Smooth muscles • Blood vessels to bring nutrients and remove waste • Nerves and sensory nerves to feel touch and pain This helps support the skin and binds the epidermis to underlying tissues.
  5. 5. Hypodermis • Composed of loose connective tissue and adipose tissue • It is a thermoinsulator and mechanical shock absorber • It is rich in adipose cells, blood and lymphatic vessels and nerves • A reservoir for fluids, electrolytes and energy • Without this layer, the skin would be at risk of tearing as it moves over bone and muscle
  6. 6. Pruritus – the Atopic Dog Pruritus is an unpleasant sensation of the skin, provoking the desire to itch – it is often caused by a parasitic infestation or allergic reactions. Atopic means hypersensitivity to environmental allergies that have either been inhaled or in contact with the skin. Canine Atopic Dermatitis This is a common pruritic skin disease, typically seen in young dogs. Commonly, it affects the face, ears, feet, ventrum or perineum. Usually, such cases result in otitis externa (discussed later) and secondary bacterial and yeast infections.
  7. 7. The Ear Malleus (hammer) Incus (anvil) Staples (stirrup) (Organ of Corti) (Tympanic Membrane)
  8. 8. How Does an Animal Hear? Sound waves are channelled towards the auditory canal by the pinnae The waves pass through the tympanic membrane and across the middle ear via the auditory ossicles The waves, now in the inner ear, move through the endolymph in the cochlea to be detected by the organ of Corti The sensory hairs in the organ of Corti react to different frequencies, dictating the nerve impulses sent to the brain The nerve impulses are sent via the auditory nerve to the temporal lobe in the brain for translation as sound
  9. 9. Aural Haematoma Cause Pathogenesis Treatment This is commonly seen in dogs and is secondary to trauma or head shaking due to otitis. • The skin and cartilage separate • The cartilage layers separate • The perichondrium and cartilage separate Vessels rupture and bleed until pressure builds up, ceasing haemorrhage. Cartilage around the haematoma degenerates and granulation tissue fills the defects. The pinna thickens and distorts in shape during healing. • Aspiration  inserting a syringe to draw out all of the fluid • Lancing • Surgery
  10. 10. Ear Disease Ear disease is classed as a skin disease! Otitis is any inflammation of the ear canal and becomes chronic when the primary cause cannot be identified. Otitis can be externa, media, interna – it usually starts as otitis externa then tracks down into otitis media then otitis interna. Primary Causes • Foreign Body • Fungal Disease • Parasites Predisposing Factors • Conformation • Moisture • Over Grooming • Systemic Disease • Obstructions • Breed – bassets, spaniels, shar- peis Perpetuating Factors • Bacterial infection • Fungal infection • Chronic inflammation • Middle ear infection
  11. 11. Ear Disease - Pathogenesis Otitis initially starts with the inflammation of the auditory canal, followed by hyperplasia of the epidermis and ceruminous glands.This leads to excess production of cerumen (ear wax) and accumulation of discharge.This has created a favourable environment for commensal organisms, Malassezia and Staphylococcus so ulcers occur resulting in a secondary bacterial infection.The diameter of the ear canal then decreases so the skin and cartilage ossify, rupturing the tympanic membrane (ear drum). It is diagnosed mainly by conducting an otoscopic exam but checking for parasites, diagnostic imaging and cytology are also very helpful.
  12. 12. Ear Disease Otitis Externa Clinical Signs Otitis Media & Interna Clinical Signs • Head shaking • Ear scratching • Malodour • Crusting • Pain • Aural heamatoma • Stenosis • Scaling • Exudation • Deafness • Pain on opening mouth • Head tilt • Vomiting • Facial nerve damage • Ruptured ear drum • Vestibular defects • Tonsillitis • Discharge Treatment: • Allergy trials • Cleansing solutions • Ear flushing • Systemic medication • Topical medication • Client education • Surgery: - Lateral Wall Resection  improves ear canal drainage - Total Ear Canal Ablation  Excises the entire ear canal
  13. 13. Neonatal Hearing Neonates are born deaf as their ears are sealed (so are their eyes) so they rely on vibration and scent but are able to balance.Their ear canal opens around 2-4 weeks of age so it as at this stage they begin to recognise sounds. Congenital Deafness Congenital deafness can either be acquired or inherited. It is common amongst certain breeds such as BullTerriers, Dalmatians, Cocker Spaniels, white cats with blue eyes, merle and spotted coats. It can often go undetected until the animal is older as neonates use other sensory cues to aid with feeding, elimination and locomotion.The best outcome for dogs suffering from congenital deafness is client counselling and education. Although, the Dalmatian Club of America has an official petition calling for the euthanasia of deaf puppies.
  14. 14. The Eye Pupil Upper Eyelid Iris Limbus Medial Canthus Third EyelidConjunctiva Lower Eyelid Lateral Canthus
  15. 15. The Eye
  16. 16. The Eye – Important Structures • Orbit • Eyelids • Conjunctiva • Lacrimal System • The Globe
  17. 17. Important Structures The Orbit Eyelids Conjunctiva • Bony fossa • Separates eye from cranial skull cavity • Important for protection of they eye and provides attachment • Contains: Eye, Extraocular Muscles,Optic Nerve, Lacrimal Gland • Dorsal and ventral folds of skin lined with the palpebral conjunctiva • Meet at the lateral and medial canthus, rest against the ocular surface • Cilia close to eyelid margin • Third eyelid: nictitating membrane and gland, aqueous portion of tear film • Lacrimal gland: aqueous portion of tear film • Meibomian glands: liquid part of tear film • Mucous membrane • Lines eyelids and sclera • Palpebral, bulbar, nictitans • Contains: Goblet cells, lymphoid tissue, connective tissue, blood vessels and nerves • Prevents corneal desiccation • Increases eyelid mobility • Acts as a protective barrier
  18. 18. Lacrimal System The Globe Cornea Sclera • Tears needed for it to be able to function properly • pH 6.8-8 • Maintains optimal surface • Removes any foreign bodies • Antibacterial • Lets oxygen and nutrients pass • Drained into nasolacrimal duct • Blinking spreads the film • Skin can become stained if not functioning correctly (epiphora – typically seen in white dogs) • Outer: Cornea and sclera to support and maintain shape. Clear to assist with passage of light • Middle: Uvea to provide nutrition and modify entering light • Inner: Retina and optic nerve to converse the light impulse to electrical impulses for processing • Clear • Avascular • Eye’s outermost lens • Functions like a window that controls and focuses the entry of light into the eye • Thick fibrous outer layer • Joins cornea at the limbus • Contains blood vessels • Appears white in colour
  19. 19. The UvealTract Iris Ciliary Body Choroid • Visible coloured layer • Hole in the centre – the pupil • Movement of iris controls light quality entering the eye • Iris muscles circle the pupil in the dog and criss-cross above and below in the cat • Sometimes pupil size can be uneven (aniscoria) • Located behind the iris between the lens and the choroid • Secretes aqueous humour which flows from the posterior chamber to the anterior chamber, causing intraocular pressure • Raise pressure = glaucoma • Lowered pressure = hypotony • Lies between the sclera and retina • Contains a mirror like layer responsible for the shine seen from cats and dogs eyes • Assists in re-stimulating the retinal photoreceptors when light is reflected back from it • Increases visual sensitivity with low light vision
  20. 20. The Lens The Retina • Biconcave structure • Avascular • No pigments so light can enter • Central portion of the lens is termed the nucleus • Hardening of portion seen in older animals is known as nuclear sclerosis • Inner most layer at the back of the eye • Contains the photoreceptor cells: Rods – function in dim light, animals have a large amount of these Cones – function in bright light, animals only have some colour detection
  21. 21. Formation of an Image The pupil allows entrance of light into the eye. Inside the glove, there are 3 chambers filled with jelly like substances: • Anterior Chamber - Aqueous Humour • Posterior Chamber - Aqueous Humour • Vitreous Chamber -Vitreous Chamber Functions • Provide nutrients • Remove waste products • Maintain shape and maintain pressure of globe to allow persistent light refraction
  22. 22. How do Animals See? The amount of light that is allowed into the eye is determined by the size of the pupil which is controlled by muscles of the iris. Creation of an Image • Light enters the eye and travels through the transparent cornea, through the aqueous and vitreous humours then through the lens • The lens changes shape by contraction or relaxation of the muscular ciliary body • Light stimulates photoreceptors in the retina so impulses are sent along the optic nerve.There are two types of photoreceptor: rods (white and black vision) and cones (colour vision). In dogs and cats, only a few cones are present, it is mainly rods. So, they have dichromatic vision and can struggle to distinguish between subtle shade differences. • The optic nerve from each eye crosses at the optic chiasm and enters the cerebral cortex via the midbrain
  23. 23. HumanVs. CatVision
  24. 24. SpeciesAdaptations • Location of the eyes • Field of vision • Colour perception
  25. 25. Corneal Ulcers REMEMBER: it is the outer portion of the globe that is clear, avascular and acts as the eyes outermost lens. The cornea consists of… • Superficial epithelium • Basement membrane (Bowman’s layer) • Stroma • Descemet’s membrane • Endothelium
  26. 26. Corneal Ulcers An ulcer occurs when there is inflammation of the cornea (keratitis). It can be the result of… • Self trauma • Foreign body • Chemical irritation • Scratches from another animal • Plants, thorns, bushes Clinical Signs • Squinty eyes • Hypersensitivity • Rubbing the eye • The eye can actually appear normal! Diagnosis can be made through fluorescein staining.The cornea should allow the liquid to run off the eye but trauma causes an indentation and disrupts the cells so the stain sticks.The ulcer can then be seen.
  27. 27. Corneal Ulcers Sometimes treatment is not needed as the ulcer can heal on its own but it is dependent on the severity. It is most important to control the initiating factor and reduce inflammation and pain, usually through antibiotics.The patient will likely need buster collar too! Complications can occur and this include: • Complicated ulcer • Melting ulcer • Indolent ulcer The ulcer may only cause minor changes in vision… • Entry of light disrupted • Focussing power altered • Blurry image
  28. 28. Hyperthyroidism & Secondary Retinal Detachment Hyperthyroidism is when the thyroid gland produces too much of the thyroid hormone thereby increasing the metabolic rate of the animal. In turn, this increases the heart rate which could lead to hypertension (high blood pressure). Should the blood pressure become too high, the retina could haemorrhage or detach, possibly living the animal blind.
  29. 29. Proptosis Proptosis is the acute prolapse of the eye as a result of trauma – it is most common in exophthalmic breeds, especially hamsters, but can be seen commonly in cats following a RTA for example. It is a medical emergency:Traction on optic nerve and fractures of the orbit and jaw can occur secondary, as well as the eyelids behind the globe going into spasm. It is also important to keep the eye lubricated. It needs replacing if possible asap and if this is not an option, they eye would have to be removed (enucleation). What is affected when the eye prolapses? • Medial, lateral, dorsal and ventral rectus muscles • Retractor oculi muscle • Dorsal and ventral oblique muscles
  30. 30. Proptosis Risks? • The eye itself may be severely damaged • The structures surrounding the eye may be damaged (orbit, surrounding bone, eyelids, lacrimal apparatus) • Palpebral muscles (muscles of the eyelid) may be damaged • 80% of animals with proptosis may lose sight or ability to keep the eye in normal position
  31. 31. Entropion Entropion is the abnormality of the position of the eyelid (inversion of the eyelids), commonly due to loose skin. It is a painful condition which particularly Shar-Pei dogs are predisposed to. To rectify this, the Holtz-Celsus procedure is carried out – this consists of the eyelids being everted and stitched down then a small area of tissue being removed to pull the eyelid out and open.
  32. 32. The Nervous System The Central Nervous System (CNS) • Brain • Spinal Cord The Peripheral Nervous System • Cranial Nerves • Spinal Nerves Sensory System Somatic Motor System Autonomic System
  33. 33. The Brain Cerebellum, pons, medulla oblongata Cerebrum, olfactory bulbs, hypothalamus, thalamus The brain controls and coordinates and is protected by the skull. The cerebral hemisphere is divides into lobes… • Occipital • Parietal • Frontal • Temporal • Olfactory
  34. 34. Part of the Brain Location Function Thalamus Deep within the posterior part of the forebrain Processing information from the sense organs and relaying this to the cerebral cortex Hypothalamus Ventral to the thalamus Links nervous and endocrine system as it secretes hormones. Influences the control of the autonomic nervous system by controlling a range of involuntary actions. Huge role in homeostasis! Regulates body temperature, hunger, thirst and osmotic balance of bodily fluids. Midbrain Lies between the fore and hindbrain. Overhung by cerebral hemispheres Pathway for fibres running from hind to forebrain. Carries sense of hearing and sight Cerebellum Dorsal surface of hindbrain Controls balance and coordination – divided into outer cortex (grey matter) and inner layer (white matter) Pons Ventral to the cerebellum Contains centres that control respiration Medulla Oblongata Extends from the pons Contains centres for respiration and blood pressure
  35. 35. The Spinal Cord
  36. 36. Cranial Nerves There are 12 pairs of cranial nerves. An easy way to remember them is… OLd OPie OCcasionally Tries TRIGonometry And Feels VEry GLOomy VAGue And HYPOactive
  37. 37. Spinal Nerves The pectoral limb (forelimb) is supplied by the brachial plexus. Nerves in the forelimb… • Radial Nerve  Supplies extensors of the elbow, carpal and digital joints • Median Nerve  Innervates flexors of the paw • Ulnar Nerve  Innervates flexors of the paw The pelvic limb (hindlimb) is supplied by the lumbosacral plexus. Nerves in the hindlimb… • Femoral Nerve  innervates the quadriceps muscle and is therefore the extensor of the stifle and flexor of the hip • Sciatic Nerve  supplies innervation to the hamstring group
  38. 38. Intervertebral Disc Disease (IVDD) 15% of disc prolapses occur in the cervical segment of the spine with the most common clinical sign being neck pain. The remaining 85% occur in the thoracolumbar region and the clinical signs are usually ataxia and pelvic limb paresis (weakness). Disc disease can be classified… • HansenType 1  Extrusion • HansenType 2  Protrusion In general, a prolapsed disc results in either compression or concussion of the spinal cord.
  39. 39. The Anatomy of a Normal Disc Gel like, acts as a shock absorber Intervertebral discs form cartilaginous joints between the vertebrae
  40. 40. Classifying Disc Disease:Type 1, Extrusion An analogy to help us understand the meaning of extrusion and protrusion is by comparing the disc to a jam doughnut! If we were to stand on a jam doughnut, the jam explodes out. In terms of the intervertebral disc, the jam would be the nucleus pulposus extruding through the annulus fibrosus into the spinal cord. It is common in chondrodystrophic breeds such as Daschunds or Bassett Hounds. Clinical Signs… • Non ambulatory • Pelvic limb para paresis • Poor proprioception • Absent or abnormal withdrawal reflexes • Absence of deep pain perception
  41. 41. Classifying Disc Disease:Type 2, Protrusion Pressing down on the jam doughnut with the palm of our hand lightly does not create enough pressure for the jam to come out. However, it does mean that the doughnuts circumference expands. In terms of the intervertebral disc, this means that as the nucleus pulposus degenerates, the annulus fibrosis protrudes so the disc bulges. It is common in larger breeds of dogs, such as GSDs. Clinical Signs… • Yelping in pain • Reluctance to jump or climb • Low head carriage and arched back • Reluctance to move head and neck • Restlessness and panting
  42. 42. IVDDTreatment Diagnosis of IVDD is made through obtaining a clinical history and diagnostic imaging (x-ray, MRI, CT). Mild cases can be medically managed using good analgesia such as NSAIDs, opioids and/or muscle relaxants or acupuncture.Whichever route is taken, strict rest is key!! For more moderate and severe cases, surgical intervention may likely be necessary.The surgery carried out can either be: • Ventral Slot  opening created ventrally through the IVD and vertebral endplates • Hemilaminectomy  removal of one half of the vertebral arch • Dorsal Laminectomy
  43. 43. Nursing a PatientWith IVDD • Padded bed to reduce the risk of pressure sores • Sternal recumbency for good bilateral lung expansion • Offer food and water little and often and place bowls close to patient • Assist with urination and defaecation, could place urinary catheter or express bladder • Keep bedding clean to avoid urinary/faecal scolding • Environmental enrichment (e.g. play music, toys, put patient in busy area of the ward) • Analgesia under theVS’ instructions • Turn every 2-4 hours if in lateral recumbency • Physiotherapy – massage, warm package joints • Grooming, owner visits
  44. 44. Obturator Nerve Paralysis This nerve originates from the lumbosacral plexus and leaves the pelvic cavity through the obturator foramen. It sits very close to the medial aspect of the shaft of the ilium, supplying motor innervation to the adductor muscles of the hind limb. The nerve is likely to be damaged during parturition, as it passes along the inside of the bovine pelvis.Therefore, prolonged or excessive traction on the calf can in turn put pressure on this nerve, damaging it. Clinical Signs • Wide base stance • Recumbency • Hind limbs extended forward Treatment • If spotted early enough, the cow should be moved to prevent complications involving the adductor muscles • Good footing • Shackle hind limbs • Deep bed • Analgesia • Food/water near patient
  45. 45. Performing a Neurological Examination Neurological examinations are commonly undertaken for investigation into abnormal gait.To begin with, assessment of the animal’s behaviour and visual clues can be indicators of where the issues lie. Individual limbs need to be assessed and can be done by flexing and extending the limb to determine how the muscles respond to manipulation, the tone of the muscles and the symmetry of the muscles. The next stage of the tests is dynamic testing and this is broken down into three phases… • Proprioception • Local Reflexes • Sensation
  46. 46. Proprioception –The 6 BasicTests • Knuckling • Paper SlideTest • Placing • Hopping • Wheelbarrowing • Extensor PosturalThrust
  47. 47. Proprioception Test Knuckling Paper SlideTest Placing Normal The animal will sense the foot is in the wrong position and reposition is instantly The animal will return their leg to the normal position The animal should see or feel the table is there and bring their front paws up and place them on the table Abnormal The paw will remain in that position The leg goes beyond 10 degrees from the vertical and the dog is unaware Limbs are not placed
  48. 48. Proprioception Test Hopping Wheelbarrowing Extensor PosturalThrust Normal Senses when to hop Moves forward evenly on both forelimbs As the animal approaches the ground, they should extend their hind limbs and take a couple of steps back upon landing Abnormal Does not hop, the leg may drag May stumble or knuckle over as they walk Hind limbs don’t extend, no steps are taken
  49. 49. Local Reflexes Test Myotatic Reflex – Patellar Reflex Withdrawal Reflex – Pedal Reflex HowTo Gently percuss (tap) the patellar ligament Pinching in-between digits, usually hindlimb Normal Involuntary contraction of the quadriceps muscle group causing reflex extension of the stifle Flexion or withdrawal of the limb Abnormal Absence of the reflex Limb is not withdrawn. Absence of deep pain sensation
  50. 50. Physiology of the PedalWithdrawal Reflex A reflex arc is a fixed response to stimuli which is a rapid and automatic response done unconsciously. It uses only nerve pathways in the spinal cord. Examples include: pedal, anal, patellar, panniculus, palpebral. The pedal reflex arc is a polysynaptic reflex. Pain stimuli aggravates nociceptors (sensory nerve fibres) in the skin of the foot.These fibres then form excitatory synapses with interneurons in the spinal cord.The impulse is therefore transmitted from nociceptors, through interneurons and to motor neurons.The motor neurons cause rapid contraction of relevant muscles to retract the legs but inhibitory neurons prevent antagonistic muscles. This can be used during anaesthesia to evaluate the depth of the GA.
  51. 51. Sensation Panniculus Reflex This is tested by a quick pin prick or gently running artery forceps in the thoracolumbar area. Normally, this will result in a quick twitch of the subcutaneous muscle along the back.
  52. 52. Neurological Examination: the Cranial Nerves Nerve Function How toTest Normal Abnormal Olfactory Smell Ability to find food or react to non-irritating chemicals Will find food or have a negative reaction Unable to find food or doesn’t respond to chemical Optic Vision Tracking: drop a cotton wool ball and the animal should watch it fall Menace: make a threatening gesture towards each eye to stimulate a blink Pupillary Light Reflex: shine a bright focal light, the pupil should constrict Should follow the cotton wool. Blink reflex should be present – wont work in rabbits or animals under 3 months. Make sure to not waft air into the eye Both pupils should constrict (indirect response) Dysfunction of the optic nerve will cause lack of vision and a decreased pupillary light reflex on the affected side
  53. 53. Nerve Function How toTest Normal Abnormal Oculomotor Eye Movements – innervates the constrictor muscles of the pupils Pupillary Light Reflex Observation of the eyes position Both pupils should constrict Lack of pupillary light reflex because of lack of innervation to the constrictor muscles to the pupils Trochlear Eye Movements Observation of the eyes position Eye looks straight forward Eye doesn’t look straight forward, in an abnormal position Abducent Eye Movement Observation of the eyes position Eye deviation Vestibulocochlear Hearing and Balance See animals response to a loud noise A loud noise evokes a response No response evoked
  54. 54. Nerve Function How toTest Normal Abnormal Trigeminal Facial Sensation Supplies the masticatory muscles/jaw muscle tone and movement Facial Sensation: Touch the philtrum of the nose with a pen and the dog should turn their head away Palpebral: gently touch the medial and lateral canthus of the eye, should blink JawTone: palpate masticatory muscles Move their head away Blink reflex Good jaw tone No response to facial sensation Reduced jaw tone and maybe atrophy of the muscles of mastication Facial Innervate muscles of facial expression Blink Symmetry of the face Perform menace response and palpebral reflex to see if the animal can blink Normal symmetry and good blink reflex Asymmetry, inability to blink
  55. 55. Nerve Function How to Test Normal Abnormal Glossopharyngeal Swallowing (gag reflex) Stimulate the back of the throat – can externally pinch just above the larynx (only if dog isn’t aggressive!) Gag reflex is stimulated Gag reflex is not stimulated Vagus Laryngeal Function (bark) See if the dog can bark normally! Can’t bark, abnormal noises Accessory Neck Position & Musculature Palpate the muscles of the neck Weakness and atrophy of the muscles Hypoglossal Tongue Movement & Position Observe tongue for muscular control when lapping water and licking Good use of the tongue, can lap water efficiently The tongue may deviate from its normal position (hang out the side of the mouth for example)
  56. 56. Peripheral Nervous System - Divisions Peripheral Nervous System Sensory System Autonomic SystemSomatic Motor System Transmits information to the CNS Parasympathetic and sympathetic divisions which control glands, heart and smooth muscles Controls Skeletal Muscles
  57. 57. Autonomic Nervous System This nervous system supplies the cardiac muscle, smooth muscle and glandular tissue and can be divided into: • Parasympathetic – rest & digest • Sympathetic – fight or flight Nerves for the parasympathetic system arise from the brain and sacral region. Nerves for the sympathetic system arise from the thoracolumbar region
  58. 58. Neuron Direction of impulse
  59. 59. How a Nerve Impulse isTransmitted The nerve impulse begins in the dendrites and moves to the Dendron into the cell body.The impulse leaves via the axon hillock, down the axon and once it reaches the axon terminals stimulates calcium channels to open.Vesicles have already begun to drift towards the presynaptic membrane and the calcium stimulates the release of neurotransmitters so acetylcholine is released into the synaptic cleft.The acetylcholine molecules combine with the post synaptic membrane, exciting the membrane so nerve impulses can be transmitted across the gap. Once at the postsynaptic membrane, cholinesterase is released.
  60. 60. Seizuring Seizuring is caused by paroxysmal discharges from groups of neurons, which arise as a result of excessive excitation or loss of inhibition. 3 Stages of Seizuring 1. Pre Ictal 2. Ictal 3. Post Ictal
  61. 61. Seizuring Seizure Classification: • Intracranial  structural/functional (brain tumour, idiopathic epilepsy) • Extracranial  reactive (toxins, metabolic disorders, infectious diseases) o Generalised (‘grand mal’) Seizure)  a seizure affecting the entire body, electrical activity affecting all/most of the brain, a loss of consciousness, tonic-clonic, mastication, salivation, urination/defaecation, nystagmus o Partial/Focal Seizure  a seizure affecting a single area of the body, electrical activity affects one small part of the brain, no loss of consciousness, twitching, repetitive movement, possible mastication, salivation
  62. 62. Major Spinal Nerves Pectoral Limb Pelvic Limb • Radial nerve • Median nerve • Ulnar nerve • Supplied by nerves from the brachial plexus • Formed from C6-C8 andT1-T2 • Femoral nerve • Tibial nerve • Saphenous nerve • Sciatic nerve • Supplied by nerves from the lumbosacral plexus • Formed from L3-L7 and S1-S2
  63. 63. Radial Nerve Paralysis The radial nerve: • Innervates extensor muscles of the elbow • Innervates extensors of the carpus and digits • Carries sensation from dorsal forepaw and proximal forelimb Therefore, if the radial nerve is damaged, these functions cannot be carried out. Clinical Signs • Monoparesis (weakness of one limb) • Knuckling • Delayed or absent proprioception • Cannot weight bear or extend forelimb • Skin sensation of dorsal metacarpus and phalanges reduced • Muscle atrophy • Proximal radial paralysis  elbow drops, limb is usually dragged
  64. 64. Radial Nerve Paralysis Causes • Trauma, e.g. RTA • Overstretching • Prolonged recumbency in heavy animals • Fractures • Nerve lesions • Damage or inflammation to the nerve prevents impulses being sent through the motor neurons to the muscle fibres Treatment • Physiotherapy • Medication – NSAIDs • Time • Amputation if none of the above work
  65. 65. Equine Post Anaesthesia Neuropathy Pathophysiology The ischaemic muscle starts to swell due to capillary damage and fluid leakage, increasing hydrostatic pressure.The vessel collapses which affects other muscle groups and the nervous tissues also become hypoxic. Prevention • Proper positioning to minimise pressure • Sufficient padding • Removal of head collars • Symptomatic treatment