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VetMed Year 1 > NEU 6 > Flashcards

NEU 6 Flashcards

1
Q

What are the different types of epileptic seizures?

A
  • Focal (partial) epileptic seizure
  • Generalised epileptic seizures (previously called primary generalised seizure)
  • Focal seizure with secondary generalisation
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2
Q

Describe the sibdivisions of focal seizures

A
  • Simple: animal usually alert and aware of its surroundings

- Complex: consciousness is altered, fly catching, aggression, running, resonant vocal sounds, crouching or hiding

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3
Q

What is meant by a focal seizure?

A

A seizure that presents with focal motor, autonomic or behavioural signs alone or in combination

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4
Q

Describe the stages of epileptic seizures in the dog.

A
  • Prodome: subtle changes in behaviour (often overlooked, hours or days)
  • Aura or preictus: anxiety, excitability, barking (seconds to minutes)
  • Icuts or seizure stage: convulsions (clonic/tonic), loss of consciousness, urination, defecation, salivation (seconds to minutes)
  • Postictus: exhaustion, also aggression or increasing appetite (minutes - days)
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5
Q

Describe the mechanisms by which anticonvulsants work

A
  • Decrease excitation or increase inhibition
  • Alter intinsic membrane properties (mostly Na+ channels)
  • Increase inhibitory transmitter function (mostly GABA system)
  • Decrease excitatoy transmitter function (glutamate system)
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6
Q

What drugs are primarily used in veterinary medicine to treat seizures?

A
  • Benzodiazepines
  • Barbiturates
  • Imepitoin (pexion)
  • Bromide
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7
Q

Describe how inhibitory function can be increased to treat seizures

A
  • GABA receptor-Cl- channel complex binding sites, potentiates endogenous GABA (benzodiazepines, barbiturates)
  • GABA transaminase inhibition, GABA build up
  • Triggered GABA release from presynaptic terminal
  • Ion competition with chloride for passage through Cl- channel, increased hyperpolarisation
  • Partial agonists at GABA-A receptors (imepitoin)
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8
Q

Describe the mechanism of action of barbiturates

A
  • Bind to GABA receptor Cl- channel complex
  • Potentiate GABA
  • Metabolised by liver, enzyme induction
  • Long half life
  • Phenobarbital is drug of choice in cats and dogs, less toxic than benzodiazepine
  • Bind to sam receptor but different site as BZD do not need GABA, open channel, influx of Cl-
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9
Q

Describe the mechanism of action of benzodiazepines

A
  • Bind to GABA-A receptors, facilitate endogenous GABA effects
  • Also used for sedative-hypnotic, anxiolytic, muscle relaxant and appetite stimulant effects
  • Metabolised by liver
  • Can be quitte toxic in cats
  • Diazepam
  • Bind to binding site, agonist effect, facilitate effect and increase frequency of Cl- travel through channel = hyperpolarisation and inhibitory postsynaptic potential
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10
Q

Describe the mechanism of action of bromide as an anticonvulsant

A
  • Competes with Cl- in Cl- channel
  • Has more of a hyperpolarising effect than Cl-
  • Distributed through body like Cl-
  • Very long half life (2-3 months to steady state)
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11
Q

Describe the mechanism of action of imepitoin (pexion)

A
  • Partial agonist
  • Potentiates amplitude of GABA - evoked currents by acting at the benzodiazepines recognition site of the GABA-A receptor
  • Low affinity partial agonist with low intrinsic activity
  • Binds to same site and receptor as a BZD but is not one
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12
Q

List the drugs that can be used to treat anxiety behaviours

A
  • Benzodiazepines
  • Tricyclic antidepressants
  • Selective Serotonin Uptake Inhibitors (SSRIs)
  • Monoamine oxidase inhibitors (MAOIs, not first choice as anxiolytic drug)
  • Azapirones
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13
Q

Describe the mechanism of action of benzodiazepines as an anxiolytic drug

A
  • Activate specific benzodiazepine receptor that facilitates inhibitory GABAergic
    transmission
  • Amygdala has BZD receptors
  • Reduce anxiety and agression
  • Some memory impairment
  • Dependence is a problem (need to reduce dose slowly)
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14
Q

Describe the mechanism of tricyclic antidepressants as anxiolytic drugs

A
  • Enhance functioanl acitivity of norepinephrine and serotonin
  • Block reuptake of both NTs
  • Treat separation anxiety
  • Increase availability of serotonin and NE
  • Serotonin associated with mood, NE associated with activity
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15
Q

Describe the mechanism of action of selective serotonin reuptake inhibitors (SSRIs) as anxiolytic drugs

A
  • Block reuptake of serotonin
  • So increases its functional activity
  • Adaptive changes in pre- and postsynaptic receptors (1-4 weeks for benefit), postsynaptic side more receptors and higher affinity for serotonin
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16
Q

Describe the mechanism of action of monoamine oxidase inhibitors as anxiolytic drugs

A
  • Not first choice as anxiolytic drugs
  • Enhance functional activity of norepinephrine, serotonin, dopamine
  • Inhibit degredation of NTs by monoamine oxidase
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17
Q

Describe the mechanism of action of azapirones as anxiolytic drugs

A
  • Activate a specific serotonin receptor
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18
Q

What is canine cognitive disorder?

A
  • Similar to Alzheimer’s

- Can be summarised by DISH: disorientation, interaction changes, sleep changes, house soiling

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19
Q

Which drug can be used to treat canine cognitive disorder and give its mechanism of action?

A
  • Segeline
  • MAOI
  • Irreversibe
  • Greater affinity for MAO-B (dopamine is the substrate) than MAO-A
  • Selectivity not absolute
  • Species variations in dopamine metabolism
  • Allows more dopamine to be available for release
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20
Q

List some common side effects of anxiolytic drugs

A
  • Sedation
  • Appetite changes
  • Diarrhoea
  • Vomiting
  • Anorexia
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21
Q

List the common side effects of selegiline

A
  • Restlessness
  • Agitation
  • Vomiting
  • Disorientation
  • Diarrhoea
  • Nausea
  • Diminished hearing
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22
Q

List the common side effects of anticonvulsants

A
  • Sedation
  • Nystagmus
  • Ataxia
  • Polydipsia
  • Polyphagia
  • CV and respiratory depression
  • Gastric irritation
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23
Q

What does ARAS stand for?

A

Ascending activating reticular system

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24
Q

Describe the reticular formation

A
  • Consists of network of grey and white matter
  • Deep thoruhgout brainstem thoruhg pons, midbrain and diencephalon
  • Continuous with similar system in spinal cord located deeply around grey matter
  • Phylogenetically older region of the brain
  • Can be divided into 2 functional divisions: ascending and descending
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25
Q

Describe the descending reticular formation

A

Linked to sensory and motor nerves and the cerebellum

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26
Q

Describe the ascending reticular formation

A

Relays impulses to higher centres for arousal (ARAS)

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27
Q

What are the inputs into the reticular formation?

A
  • Spinoreticular tracts from spinal cord

- Collateral neurons from sensory/afferent neurons travelling to diencephalon

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28
Q

What are the outputs of the reticular formation

A
  • Reticulospinal tracts to spinal level

- Intralaminar nuclei of thalamus and on to cerebral cortex

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29
Q

Describe the role of the reticular formation in the transmission of pain

A
  • Pain information transmitted via spinoreticular tract and ascending reticular formation to thalamus and ultimately cerebral cortex
  • Projects to cortex via diffuse thalamic projections
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30
Q

Describe the role of the reticular system in arousal

A
  • ARAS sensitises cerebral cortex to particular sensory modalities
  • Keeps cortex active during wakefulness
  • Reduced activity results in sleep
  • Severe lesion usually leasd to coma
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31
Q

Describe the mechanism of sleep

A
  • Main sleep centre believed to be in hypothalamus
  • Balance occur between activities of ARAS and sleep centre
  • ARAS is main brain structure that maintains wakefulness and arousal
  • Is a flip flop system - hypothalamus and ARAS inhibit each other
  • Oxinergic neurons in lateral hypothalamus triggers switching between the 2
  • Orexin produced - stimulates activity and food intake
  • Peptides have receptors on reticular formation and activate it
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32
Q

What is the role of the vlPOA in sleep regulation?

A

vlPOA = ventrolateral preoptic area

  • is the main sleep centre
  • Accumulation of adenosine (result of metabolic activity) turns sleep centre on
  • Caffeine is an antagonist of adenosine so keeps you awake
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33
Q

What are the inputs into the orexinergic neurons?

A
  • Biological clock (suprachiasmatic nucleus)
  • Hunger signlas activate system
  • Satiety signals inhibit system
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34
Q

What are the 2 types of sleep?

A
  • Slow wave (deep) sleep
  • Rapid eye movement sleep (dreaming, atonia, fluctuating blood pressure, heart rate, respiration)
  • They follow each other cyclically during sleep periods
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35
Q

What is orexins mechanism of action?

A

Inhibits the inhibition of lower motor neurons causing wakefulness

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36
Q

Describe the external ear

A
  • 2 to echolocate
  • Cartilages lining the ear help direct the sound
  • Pinna (auricle) is vertical canal
  • Moved by 5 sets of muscles innervated by VII (rostral, dorsal, caudal, ventral, intrinsic)
  • Horizontal part of external acoustic meatus
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37
Q

Describe the pinna

A
  • Receives sound waves
  • Reflected and amplified down the canal
  • Very directional, heance ear movement helos locate source
  • Consducts sound waves to tympanic membrane
  • Fine hairs - tragi
  • Themoregulatory and behavioural roles
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38
Q

Describe the external acoustic meatus

A
  • Long and curved
  • Cartilaginous part (long)
  • Osseus part next to bulla (short, longer with age)
  • Lined with stratified squamous epithelium
  • Contains sebaceous glands producing earwax (cerumen)
  • Epithelial cells migrate outwards
  • Sliding conveyor for debris etc trapped in cerumen
  • Hence vertical canal may be dirty while horizontal canal is clean
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39
Q

Describe the development of the middle and inner ear

A
  • Develops as otic placode of ectoderm lateral to developing rhombencephalon
  • Otic placode invaginates to form otic vesicle
  • Otic vesicle produces inner ear
  • Utricle - semicircular canals
  • Saccule - cochlea
  • Ossicles form from mesoderm of 1st and 2nd pharyngeal arches
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40
Q

What is the middle ear made up of?

A
  • Tympanic cavity within tympanic bulla
  • Auditory ossicles
  • Auditory tube (Eustachian tube)
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41
Q

Describe the temporal bone

A
  • Made up of 3 bones
  • Squamous - extends into zygomatic arch
  • Petrosal - very dense bone, no air chambers, contains inner ear, does not resonate
  • Tympanic - resonant cavity, dorsal part contains auditory ossicles
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42
Q

Describe the tympanic cavity

A
  • Normally air filled
  • Has epithelial mucosal lining
  • Is within tympanic part of petrosal bone
  • Contains dorsally the auricular ossicles in the epitympanic recess
  • Middle part includes tympanic membrane in lateral wall of cavity and opens into auditory tube
  • ventral part is tympanic bulla (enhances hearing at low and high frequencies)
  • 2 windows into medial wall: oval vestibular window covered by the stapes and the cochear window closed by the secondary tympanic membrane
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43
Q

Describe the tympanic membrane

A
  • Separates external from middle ear
  • 3 layers
  • External epithelial lining (ectoderm)
  • Connective tissue with collagen and elastic fibres, fibrocartilaginous ring (mesoderm) and inner mucous membrane towards tympanic cavity (endoderm)
  • Insertion of malleus (hammer)
  • Transmission of sound waves from air onto auditory ossicles
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44
Q

Describe the development of the auditory ossicles

A
  • Incus and malleus develop from 1st pharyngeal arch mesoderm (mammals) from ancient parts of jaw bonw
  • Stapes develops from 2nd pharyngeal arch mesoderm
  • Mandible derived from 1st arch as well as incus and malleus to make commplex jaw bone in reptiles
  • Definind feature of mammals is the presence of 3 ear ossicles
  • During evolition, bones of jaw becomes ossicles of ear
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45
Q

Describe the structure of the middle ear

A
  • 2 striated muscles
  • Stapedius muscle attached to stapes
  • Tensor tympani muscle attached to malleus
  • Reflective contraction in response to loud sounds => protects inner ear from damage
46
Q

Describe the function of the auditory ossicles

A
  • Transmit vibrations for the tympanic membrane across the tympanic cavity to the inner ear
  • Air-bone coupling
  • Bone - liquid coupling
  • Reduction of sound reflection
  • Initiation of wave in perilymph of inner ear
  • 2 muscles involved in attenutation of vibrations
  • Tensor tympani (V3 since from 1st pharyngeal arch)
  • Stapedius (facial nerve, from 2nd pharyngeal arch)
47
Q

What is the importance of the Eustachian tube in the ear?

A
  • Connection between nasophayrnx and middle ear for air pressure equalisation
  • Important in perissodactyls (guttural pouch)
48
Q

What nerves are present in the middle ear?

A
  • Facial nerve

- Tympanic nerve (from cr. n. IX - glossopharyngeal)

49
Q

Describe the roleof cr. n. VII in the middle ear

A
  • Runs thoruhg facial canal, open to tympanic cavity
  • Innervates stapedius via stapedial nerve
  • Gives off chorda tympani (tast to rostral 2/3 of tonge, heat and mechanoreceptors), joins lingual branch of V3 nerve
50
Q

Describe the tympanic nerve function

A
  • Branch of cr. n. IX
  • PSNS supply for parotid and zygomatic salivary glands
  • Postganglionic sympathetic fibres from cranial cervical ganglion join ophthalmic nerve nerve for sympathetic supply of the eye
  • Damage leads to facial nerve paralysis (Horner’s syndrome)
51
Q

Describe the vestibulocochlear organ

A
  • Located inside petrosal part of temporal bone
  • Fluid is present within the cochlea
  • Ducts sit inside the canals
  • Ducts contain endolymph
  • Perilymph is almost like CSF
  • Vibrations through the ossicles, through fluid then out through cochlear window
  • Set sup vibrations in coiled tube
  • The osseus larbyrinth contains the membranous labyrinth
52
Q

What are the 3 parts of the cochlea

A
  • Scala vestibularis
  • Scala media
  • Scala tympani
53
Q

Describe the scala media

A
  • Can also be called cochlear duct
  • Only part that can bend is Reissner’s membrane which does not resist mechanical changes
  • Basilar membrane changes in stiffness
  • Reissner’s membrane is an electrolyt pump and does not resist transmission of energy into endolymph
54
Q

Desribe the hair cells of the scala vestibuli

A
  • Inner and outer hair cells
  • Stereocilia: very stiff, bend at the bottom and together
  • Lenfht of cell changes going through cochlea
  • Fibres of VIII are efferent to outer hair cells
  • Inner hair cells have afferent connections
  • IHCs are not embedded in tectorial membrane
  • Afferents give infomation to brain then information comes back down to the OHCs
55
Q

Describe the innervation of the inner hair cells by the cochlear root of VIII

A
  • Afferent
  • 1 IHC: 10 axons
  • Myelinated
  • Form radial afferents
  • To cochlear nuclei in medulla
  • Efferent innervation from ipsilateral olivary nuclei
56
Q

Describe the innervation of the outer hair cells by the cochlear root of VIII

A
  • Efferent innervation
  • 10 OHC: 1 axon
  • From both sides of olivary nucleus
  • Form spiral nonmyelinated axons
57
Q

Describe the role of OHCs

A
  • Amplify local vibrations

- contractile cells

58
Q

Describe mechanotransduction in the hair cells

A
  • Scala vestibuli and cochlear duct (scala media) behave as single hydraulic tube
  • Sound pressure cause resonance at certain distances from oval window
  • Basilar membrane vibrates, bends stereocilia on OHCs
  • K+ enters the OHC and they depolarise
  • OHCs contract which amplifies the initial vibration (reverse transduction)
  • IHC are excited (vibrate, K+ enters) and afferent axons are stimulated, send signal centrally
59
Q

Give the most basic explanation of reverse transduction in the hair cells of the cochlear duct

A
  • OHCs vibrated
  • K+ enters
  • Vibrate more
  • Amplify initial vibration in endolymph
  • Moves IHCs more
  • Afferent signal sent to brain
  • Efferent fibres send signal to OHCs and ACh hyperpolarises them, preventing further contraction
60
Q

Explain how frequency recognition occurs

A
  • Basilar membrane is narrow and stiff near round window
  • Vibrates at high frequencies
  • Close to helicotrema membrane is wide and flexible
  • Vibrates at low frequencies
  • Tonotopic arrangement of frequency
  • Response: each small part of membrane vibrates at a particular frequency
61
Q

Explain why the coiled cochlea is useful compared to an uncoiled cochlea

A
  • Increases sensitivity to hearing
  • Energy cannot leak out as easily into areas that are not cochlea
  • Only coiled in mammals
  • Non-mammal is straight
62
Q

Explain what BAER stands for and how it works and what it is used for

A
  • Brainstem Auditory Evoked Response
  • Each ear stimulated by separate click stimuli
  • Accumulated action potential from cochlea via cochlear nerve can be measured as auditory evoked potential
  • Responses recorded for each ear separately
  • 5 possible peaks
  • Sedation or anaesthesia needed to avoid artefacts
  • Can be used to determine brain health in coma
63
Q

What is peak one of BAER

A
  • Stimulation of cochlea and cochlear nerve to the brain stem
64
Q

Explain how directional hearing works

A
  • Arrival time difference between both ears
  • Sound shadow of head
  • Sound modulation by auricles
  • Works best with mid to high frequencies
65
Q

What are the central glial cells

A
  • Astrocytes, oligodendrocytes, microglia
66
Q

What is the difference between oligodendrocytes and Schwann cells

A
  • Oligodendrocytes can myelinate multiple axons, Schwann cells can only myeline one
  • Oligodendrocytes are found in the CNS and Schwann cells are found in the PNS
67
Q

Briefly describe the structure of the neocortex

A
  • 6 layers - no segregation between layers
  • Neurones have very prominent nuclei
  • Many capillaries to supply nutrition to the brain
68
Q

Describe the white matter in the cerebrum

A
  • Tightly packed axons
  • Wrapped in myelin sheaths and oligodendrocytes
  • Fibres run parallel mostly
  • Very little space so oligodendrocytes sit in rows
  • See rows of blue dots = oligodendrocytes
  • Only present in white matter
69
Q

Briefly describe the grey matter in the cerebellum

A
  • Some neurones in molecular ayer
  • Mostly dendrites from Purkinje cells
  • Grey matter in cerebellum reduces excitatory actions (Purkinje cells are inhibitory)
70
Q

Describe the histological appearance of the dorsal nerve root in the spinal cord

A
  • Looser

- Peripheral nerves

71
Q

Describe the histological appearance of autonomic nerves

A
  • Neurones sit in clusters (look like squid - oblong, nucleus, some fibres leaving)
  • Blue dots are satellite cells
72
Q

Explain how several cranial nerves can be affected by pathology

A
  • Many leave from same place (medulla oblongata) so pathology here would affect many nerves
  • Some have same exit sites from the skull (jugular foramen for example) so pathology over foramina can affect multiple cells
  • Multiple tumours coud be present
  • Infection (encephalopathy) affecting multiple cranial nerves
  • Parasite
  • Oedema due to hypertension
73
Q

Compare the olfactory and optic lobes of birds and reptiles

A
  • Reptiles have prominent olfactory bulbs

- Birds have large optic lobes and forebrains

74
Q

Explain why fish forebrain enlargement is necessary

A
  • Olfaction
  • Complex behaviour (schooling)
  • Muscle control
75
Q

Describe the spinal cord and peripheral nerves of reptiles

A
  • Functional autotomy locomotor centres
  • No cauda equine (spinal cord goes all the way down the vertebrae)
  • Relfexes not established for neuro exm
76
Q

Describe the spinal cord and peripheral nerves of birds

A
  • No cauda equina
  • Enlarge brachial or lumbosacral plexus
  • Brachial plexus in flying birds, lumbosacral plexus in running birds. Near kidney
  • Glycogen body
  • Mass of glycogen containing astrocytes
  • On dorsal surface of LS plexus
  • Function unknown
77
Q

Describe the meninges of fish, reptiles and birds

A

Fish: meninx, single layer

  • Reptiles: 2 layers, dura mater and meninx (fused pia-arachnoid), no subarachnoid space
  • Birds: all 3 layers, epidural space with gelatinous tissue
78
Q

How many cranial nerves in fish, amphibians, reptiles and birds?

A
  • Fish and amphibians = 10 + lateral line nerves

- Reptiles and birds: 12

79
Q

Describe the lateral line system

A
  • Present in fish and truly aquatic amphibians
  • Sensitive to tiny local displacement of water
  • Receptors for touch at a distance
  • Prevent contact between organisms
  • Primary organ is neuromast organ
  • 3 neuromast organs
  • Sense hairs project into cupula
  • Cupula bends when water moves across it, bends hairs and gives signal to sensory cells
  • Most fish also have lateral line canals - secondary specialisation
  • Series of neuromasts
  • Allows sensing of different pressures along the body
  • Recognition of strength of water movement
80
Q

Describe and explain the infrared sensors in some snakes

A
  • Heat pits detect temp of prey
  • Bilaterally symmetrical
  • Nostril, pit hole and eye closely related
  • Heat sensitive membrane inside pit organ
  • Locate prey via triangulation
  • Can turn head to identify exact location
81
Q

What is a pineal complex?

A
  • Epithalamus can invaginate and forms up to 4 structures
  • Does not usually do all 4
  • Paraphysis, dorsal sac, parietal organ, epiphysis
  • Pineal complex is when 2 or more are present
82
Q

Describe the parietal organ

A
  • Parapineal organ, parietal eye
  • Photoreceptive organ
  • +/- cornea, lens, photoreceptive does
  • Does not form an image, just detects presence of light
83
Q

Describe the epiphysis

A
  • Pineal organ/pineal gland
  • Dorsal evagination of midbrain
  • Under skin or within cranium
  • Secretes melatonin
  • Cyclic activities (daily and seasonal)
  • Photic stimuli -> neuroendocrine messages
  • variable within classes of vertebrates
84
Q

Describe the epiphysis and parietal organ of bonyy fish, amphibians, reptiles, birds and mammals

A
  • Fish: prominent epiphysis, rudimentary parietal organ
  • Amphibians: epiphysis, parietal organ
  • Reptiles: epipysis and parietal organ (third eye in lizards)
  • Birds and mammals: no parietal organ, epiphysis has endocrine function only aka pineal gland
85
Q

Compare the location of photoreceptors and endogenous pacemakers of non-mammals, birds and mammals

A
  • Non-mammals: photoreceptors and endogenous pacemaker within pineal organ
  • Birds: pacemakers in other parts of CNS
  • Mammals: photoreceptors in retina, endogenous oscillators in SCN of hypothalamus
86
Q

Describe prgans of olfaction in fish, amphibians, reptiles and birds

A
  • Fish: ends in nasal sacs, water carries chemicals in, choana
  • Amphibians: nasal sac, vomeronasal organ, nasolabial grooves move chemicals into vomeronasal organ
  • Reptiles: vestibule (receives air, anterior), nasal chamber is posterior, may or may not have conchae or turbinals, nasophayngeal duct
  • Birds: olfactory bulb size relative to lifestyle, smallest in seed eaters, larger in aquatic birds
87
Q

Describe the vomeronasal (Jacobson’s) organ

A
  • Present in amphibians, lizards, snakes and many domestic species and non-domestic mammals
  • Responds to chemosensroy stimuli including social or reproductive behaviour
  • Not present in fish, birds or chelonians
  • Accessory olfactory organ (paired)
  • Sits on roof of oral cavity
  • Linked to vomeronasal nerve
88
Q

Describe the location of the vomeronasal organ in amphibians, snakes, lizards and mammals

A
  • Amphibians: recessed area of main nasal cavity
  • Snakes and lizards: separate pit in oral cavity, tongue and oral membrane deliver chemicals
  • Mammals: nasal cavity, isolated area of olfactory membrane and connects to mouth via nasopalatine duct
89
Q

Describe the external ear of fish, amphibians, birds and mammals

A
  • Fish and amphibias have no external ear
  • Reptiles sometimes have an external acoustic meatus
  • Birds and mammals have elongated external auditory meatuses
90
Q

Describe hearing in reptiles

A
  • Tympanic membrane level with skin (not snakes or chameleons)
  • 1 middle ear bone - stapes (connects tympanic membrane to inner ear)
  • Vibrations from air or ground go tympanic membrane -> stapes -> perilymphatic fluid (inner ear)
91
Q

Describe hearing in snakes

A
  • No tympanic membrane
  • Stapes connect quadrate bone with cochlea
    Quadrate -> stapes -> oval window
  • Hear low frequencies
92
Q

Describe hearing in birds

A
  • Short external acoustic meatus = tympanum
  • Songbirds have 2 tympanic membranes
  • No pinna, special feathers instead
  • Single auditory ossicle = stapes
  • Regenerate damaged hair cells (mammals do not)
93
Q

Describe the Eustachian tubes in reptiles and birds

A
  • Connects middle ear to oropharynx
  • Not closed
  • Adjustment to high altitudes facilitated
  • Pathogens can easily ascend into tympanic cavity and inflammatory debris can enter pharynx
94
Q

Describe the facial feathers of the owl

A
  • Auricular feathers are acoustically transparent
  • Reflector feathers are densly ramified and able to direct sound to ear
  • Tightly packed rim of facial feathers
  • Sound -> external auditory meatus
95
Q

Describe and explainn owl ear asymmetry

A
  • Left and right external acoustic meatuses are different size and shape
  • Helps localise sound by the intensity and timing of sounds
  • Can hear in horizontal and vertical planes
96
Q

Describe fish eye anatomy

A
  • Bulbous eye - dome shaped cornea, rigid iris, lens protrudes
  • Difficult to adjust to light changes - pupil fixed, position of photoreceptors
  • Focus: change lens position instead of lens shape
  • Rods:cones ratio varies
  • Can see in colour and UV
97
Q

Describe amphibian eye anatomy

A
  • Move lens to accomodate
  • Iris - striated muscle (voluntary) so cannot evaluate PLR
  • Vision is by pattern recognition
  • Retina processes most visual info
98
Q

Describe avian eye anatomy

A
  • Large compared to head and brain
  • Larger, sharper images
  • Nictitating membrane (striated msucles, rapid sweeps to clean cornea)
  • Lacrimal and Harderian glands - in many lacrimal reduced, Harderian gland is on posterior aspect of orbit and associated with base of nictitating membrane
  • Composition of secretions from HG unknown
99
Q

Describe the scleral ossicles in birds

A
  • Forms ring around eye
  • Reinforces scleral junction
  • Extra support for eye
100
Q

Explain how visual acuity is improved in birds

A
  • Avascular retina - less light scatter from blood vessels, higher visual acuity
  • Pecten - highly vascularised, thin, highly folded, nutritional role
101
Q

Describe the role of the fovea in improving visual acuity

A
  • High concentration of rods and cones
  • Sharpen vision
  • Present in fish, reptiles, birds and primates
  • Usually 2 fovea in diurnal species especially raptors
102
Q

Describe rods and cones in birds

A
  • Double cone
  • Principle and accessory cone
  • Diurnal birds have more cones, nocturnal more rods
  • Colour vision varies in birds
  • Some diurnal can see UV
103
Q

Describe the structure of bird cones

A
  • Have oil droplets on cones
  • Light through droplet first
  • Lipids and carotenoid pigments in oil
  • UV light shield
  • Focuses light
  • Allows perception of UV light
  • UV is used for signalling in birds (feather reflecting UV, food reflecting UV differently)
104
Q

Describe accomodation in avian vision

A
  • Lens shape - softer so more rapid changes
  • Corneal curvature
  • Each eye is independent
  • Iris sphincter is made up of striateed muscle and so is under voluntary control
105
Q

Describe reptile eye anatomy

A
  • Eyelids - lower lid is mobile
  • Scleral ossicles
  • Nictitating membranes
  • Lacrimal and Harderian glands
  • Harderian gland provides enzymes facilitating vomerolfaction in reptiles
106
Q

Describe the spectacles in snakes and some lizards

A
  • Fused eyelids, transparent
  • Dry horny scale
  • Insensitive
  • Subspectacular space
  • Shed during ecdysis (colour change)
107
Q

Describe accomodation in reptile vision

A
  • Muscles of ciliary body to change curvature of lens (lizards, chelonians)
  • Iris sphincter - striated muscles (chelonians, snakes), under voluntary control
108
Q

Describe the retina of reptiles

A
  • Avascular
  • Conus papillaris may or may not be present (lizards, some snakes)
  • Choroidal blood vessels
  • Rods and cones
  • Fovea centralis - lizards (diurnal)
109
Q

Describe the relationship between memory and emotions

A
  • Learning can be based on repetition
  • Can also occur wihout it, particularly following events that cause a strong emotional response
  • Anxiety for example can be a conditioned emotional response that occurs when a neutral stimulus is followed by an aversive stimulus
110
Q

Describe counterconditioning

A
  • Can learn new responses to something that previously elicited a different response
  • ## Can use respondent or operant counter conditioning
111
Q

Describe desensitisation

A

Reducing the response to a stimulus through repetitive neutral exposure

VetMed Year 1 (13 decks)

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