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CNS Y1 Flashcards

1
Q

Describe the development of fore/mid/hind brain.

A
  • Procencephalon
    • Telencephalon - cerebral hemispheres
    • Diencephalon - Thalamus/hypothalamus and optic cups
  • Mesencephalon - Midbrain and brain stems
  • Rhombencephalon
    • Metencephalon - Pons & cerebellum
    • Myelencephalon - Medulla Oblongata
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2
Q

How is the neural tube formed?

A
  1. Thickened neural plate - thickened ectoderm, stimulated by mesodermal notochord
  2. Invagination of the NT forming the neural groove and crest cells overlying notochord
  3. Pinching off of the neural crest cells
  4. Closing off of the neural tube
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3
Q

Spina Bifida

A

Failure of the neural tube to close at the caudal end. Characterised by a clump of hairy skin.

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4
Q

Draw and describe the anatomy of the neural tube.

What factors are secreted by the roof and floor plate?

A

Roof plate - TGF B cascade - BMF

Marginal layer - forms the white matter

Mantle layer - forms the grey matter - Alar and basal plate

Floor plate - SHH sonic hedgehog

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5
Q

What do the factors secreted by the roof and floor plate cause for the dorsal and ventral region of the neural tube?

A
  1. BMP - dorsal region - sensory neuron differentiation (PAX)
  2. SHH - ventral region - motor neuron differentiation (NKX)
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6
Q

Name the embryological flexures of the brain and describe how they partition the brain.

A

Cephalic - Mid brain

Pontine - Near mesencephalin and spinal cord

Cervical - at the developing pons - remember that this fold is less pronounced in quadripeds

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7
Q

How does the brain fold during lateral brain development?

How does cyclopia develop in the embryo?

A

The forebrain differenciates into telencephalon and diencephalon. The telencephalon folds dorsally and elongates, it then folds caudally and progresses around to fold ventrally and rostrally.

Cyclopia develops if the forebrain fails to subdivide. It can be caused by toxins such as cornlily or by faulty genes.

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8
Q

Name and describe the three menigial layers.

A
  1. Dura - thick connective and elastic tissue fuses with periosteum apart from at the faux cerebrum and tentorium cerebelli and diaphragm sellae
  2. Arachoid - Fine, avascular membrane. The subarachoid space exists below this and contails trabeculaeand fills with CSF
  3. Pia - the most fragile, highly vascularised layer. Fuses with the adventitia of BVs. Contains denticulate ligaments which act as sling supporting the spinal cord.
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9
Q

What are the functions of the CSF?

What are the characteristic features?

Where is it produced?

A
  1. Nutrition, support and volume buffer
  2. Low aa, k+ and glucose, acellular - highly regulated
  3. Choroid plexi of the ventricles - consists of modified ependymal cells - found between the lateral and third ventricles of the brain
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10
Q

Draw the arterial circulation of the brain. (x7)

A
  1. Rostral cerebral
  2. Cerebral arterial circle
  3. Internal carotids
  4. Middle cerebral
  5. Caudal cerebral
  6. Basilar
  7. Caudal cerebellar

This varies between species.

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11
Q

What are the rete miriable and what are their function?

A

They are highly folded vessel complexes which exist in the brain to reduce pulsation and heat the blood before it enters the brain.

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12
Q

Name the epithelial cells of the spinal cord.

A

Ependymal

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13
Q

Compare the visual field of the herbiovore and carnivore.

A
  1. Carnivore - frontal position = large central binocular vision - greater depth of vision.
  2. Herbivore - lateral position = wide monocular vision - weak depth of vision.
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14
Q

How does the pupillary light reflex differ at low and high light intensity?

What CN is this power by?

A
  1. Low light - Radial muscle contracts = pupil dilates
  2. High light - Sphincter muscle contracts = pupil constricts
  3. Sensory = CNII, Motor = CNIII
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15
Q

If there is more decussation of CNII at the optic chiasm is there a greater or lesser depth of vision?

A

greater

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16
Q

Differenciate between the endo and exomeninx.

A

Endomeninx - mesodermal origin - form the pachymeninges (dura)

Exomeninx - neural crest cells - form the leptomeninges (arachnoid and pia mata)

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17
Q

The rostral colliculus is also known as what? What is its function?

A

The optic tectum

Its function is to direct behaviours towards particular areas in space containing visual stimuli

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18
Q

Dysfunction of which cranial nerves results in a) ventrolateral, b) extorsional and c) medial strabismus?

What effect do these dysfunctions have on eye movement?

A

a) Ventrolateral - CNIII - ptosis accompanies
b) Extorsional - CNIV - outer dorsal rotation (via dorsal oblique)
c) Medial - CNVI - crossed eyes, medial rotation (via lateral rectus)

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19
Q

Outline the three visual processing pathways relevant to NSF.

A
  1. Vision > eye > CNII > optic tract > Lateral geniculate nucleus > optic radiation > visual cortex
  2. PLR > eye > CNII > optic tract > Midbrain CNIII > Iris
  3. Spatial Orientation > eye > CNII > optic tract > Rostral colliculus > Midbrain > Extraoccular muscles
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20
Q

Name the main anatomical features of the eye and briefly describe them.

(x9)

A
  1. Choroid - vascular layer which supplies retinal layers
  2. Iris
  3. Ciliary body - Alters lens shape and alter vision focus
  4. Vitreous chamber - Vitreous humour holds retina against the choroid
  5. Cornea - Avascular transparant front of the eye
  6. Sclera - White fibrous layer
  7. Lens - accomodation and focusing of light
  8. Aqueous humour -
  9. Retina - ora serrata - light-sensitive layer of tissue
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21
Q

The medial right eye is supplied by which side of the brain?

A

Left side (decussates at the optic chiasm)

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22
Q

How is the aqueous humour produced and where is it released to?

Describe its circulation.

What happens if aqueous humour fails to drain?

A
  • Ciliary processes pump ions in to the posterior chamber > causes an osmotic gradient > water moves in > pressure causes fluid to move from posterior to anterior chamber.
  • Drained by the venous plexus of the anterior chamber.
  • Glaucoma - raised intraoccular pressure, impeding circulation and leading to cell death
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23
Q

Draw and label the spinal cord and vertebrae cross section.

A
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24
Q

Draw and label the spinal cord, labelling the intumesences, conus medullaris, lumbar cistern and cauda equina.

Briefly describe each structure.

A
  1. Intumesences - thickenings shoing origination of fore and hindlimb plexi
  2. CM - The tapering out of the lower spinal cord around L1/2
  3. LC - Contains the nerve roots of the cauda equina
  4. CE - The bundle of spinal nerve which occur ones the spinal cord tapers off
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25
Q

What are the spinal cord segements called and how many nerves are contained within each in the dog?

A
  1. Cervical - C1-5
  2. Thoracic - C6-T2
  3. Lumbar - T3-L3
  4. Sacral - L4-S3
  5. Caudal - Cd1-Cd5
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26
Q

What is a dermatome?

A

A band of skin around the animal which corresponse to a single spinal nerve

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27
Q

Name the basal ganglia and describe the function of the BG.

A

Caudate, putamen and globus pallidus

Planning of complex movement, links motivation and emotion with movement and performance of automated response.

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28
Q

Discuss the sensory and motor tracts of the brain and their function.

A
  1. Sensory
    1. Dorsal column - touch tract, decussates a the brain stem
    2. Spinothalamic - pain tract, decussates in the spinal cord after emerging from the ganglion
  2. Sensory
    1. ​Pyramidal - 2 neurone system, decussates at the brain stem
    2. Extrapyramidal - 3 nerurone system, decussates at the brainstem
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29
Q

Extensor LMNs are important regulators of what?

A

Stift extension - maintaining balance/ posture

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30
Q

“Loss of reflexes, atrophy and tonal loss”

This statement characterises lesions to UMNs or LMNs? How is the other characterised?

A

LMN

UMN lesions are characterised by exaggerated movements

31
Q

Name and draw an example of a monosynaptic and polysynaptic reflex.

A
  1. Monosynaptic - One connection between afferent and efferent fibres - Patellar
  2. Polysynaptic - Communicates with higher centres - Withdrawal
32
Q

Describe the patellar reflex.

(include a diagram)

A

Stretch receptors of the patellar ligament stimulate the femoral nerve –> L4-S3 through dorsal horn –LMN–> Ventral horn (stimulates stifle extensors)

Also intersegmental nerves are stimulated which inhibit stifle flexors.

33
Q

Describe the withdrawal reflex.

A

Nociceptors detect noxious stimulus. Forebrain detects pain, decussation causes other leg to weight bear. Interneuron causes LMN extensors to be inhibited and LMN flexors to be stimulated.

34
Q

A muscle spindle is an example of what type of muscle fibre? Draw one.

It is therefore innervated by which type of LMN?

A

Intrafusal muscle (extrafusal are gross muscle cells)

They are innervated by gamma LMS’s

35
Q

Muscle spindle stretch reflex

What is the role of the gamma LMN in this process?

A
  1. Muscle and spindle are stretched
  2. 1A afferent sends signal to brain about stretch.
  3. Causes contraction of the muscle in question via alpha LMN’s

Gamma motor neurons maintain the tautness of the muscle spindle stretch receptors

36
Q

What is the role of the golgi tendon organ ?

Which type of afferent neurons are involved in this reflex?

A

Found within the tendon, the GTO detects stretch of the tendon. Its goal is to prevent damage/ evulsion of the tendon.

Muscle stretches > **1b afferent neuron **> Interneurons cause contraction of muscle and inhibition of antagonistic muscle via alpha LMN’s

37
Q

What type of movement are pyramidal and extrapyramidal tracts involved in?

How does their degree of development differ between species?

A
  1. Pyramidal = fine planned movement - particularly in distal limbs of primates or lips of horses
  2. Extrapyramidal = automated rhythmic movements - continuous throughout the spinal cord.
38
Q

Name and describe the five main motor tracts of the spinal cord.

(CTRVR)

A
  1. Pyramidal
    1. Corticospinal - fine/concentrated movement
    2. Tectospinal - Sight/ sound response
    3. Reticulospinal - gravity stabilisation/tone
    4. Vestibulospinal - subconscious posture/balance
  2. Extrapyramidal
    1. Rubrospinal - voluntary/skilled movement
39
Q

What is the function of UMN’s?

A

Regulation of lower motor neurons, they are mostly inhibitory to the LMNs

40
Q

What is the difference between rapidly and slowly adapting nerve fibres?

A

Rapidly adapting fibres change firing as stimuli continues, they are myelinated, ie the feeling subsides.

Slowly adapting neurons continue firing for the length of the stimuli

41
Q

Proprioception

A

The sense of body position and structures relative to position

42
Q

How could you tell a difference between a deficit in conscious and subconscious propriosception?

A

Conscious - stumbling, knuckling and intention tremors

Subconscious - ataxia, splayed limbs and swaying

43
Q

Define kinaesthesia.

What inputs contribute?

A

Knowledge of spatial orientation.

Cerebellar input & motor cortex input feed back to the cerebral cortex.

  • GTO
  • Muscle spindles
  • Tactile receptors
  • Motor cortex
44
Q

How is a receptor potential generated in the ear?

A

Ear drum vibrates > ossicles vibrate > stirrup pushes on oval window > perilymph moves > pressure waves.

Scala vestibuli > S. tympani > S. media > Basilar membrane deflects > hair bundles move (organ of corti) >> VIBRATIONS > electrochemical energy and receptor potentials.

45
Q

Label this inner ear

A
  • Ossicles - hammer, anvil, stirrup
  • Vestibule - CN VIII vestibular nerve, semilunar canals
  • Cochlear - CN VIII cochlear nerve
  • Oval and round window
  • Auditory tube
46
Q

How is the cochlear organised?

A

Oval window > scala vestibuli > scala tympani > scala media > organ of corti

47
Q

Draw and label the organ of corti.

What type of nerve cell are hair cells classified as?

A

Secondary nerve cells

48
Q

Which nucleus does the VIII communicate with in the Auditory pathway?

A

Cochlear > pons > medial geniculate nucleus

49
Q

Horner Syndrome

A

Prolonged middle ear infection leads to damage of the cervical ganglion and sympathetic chain (cranial nerves)

  • Facial paralysis
  • Displaced third eyelid
  • Ptosis - drooping of the eyelid
50
Q

Name and draw each of the vestibular organs and their basic functions.

How do each of these organs work?

A
  1. Otoliths - detect information about the vertical axis (head tilted or upside down) - movement of CaCO3 in otolith bag moves hair cells
  2. Semilunar canals - detects information about the horizontal axis (circular rotation) - cupula filled with gel
51
Q

The vestibular pathway decussates. True or false?

Information from the vestibular pathway supplies which structures of the body?

A

True (decussates and reaches the vestibular cortex of the contralateral hemisphere)

  • Muscle spindles
  • Extraoccular muscles
  • Cortex
  • Cerebellum
52
Q

What are the four reflexes of the vestibular system?

What:

  1. Are they sensed by?
  2. Do they detect?
  3. is their outcome?
A
  1. Vestibular - Sensed by the vestibular organs, detect the relationship between the body angle and the vertical. Allows balance and shift in centre of gravity
  2. Vestibulo-occular - Sensed by the vestibular organs, this detects retinal angle and works to stabilise retinal image
  3. Tonic Neck - Sensed by neck muscle spindle, detects body angle in relation to vertical when head is righted, stabilises centre of gravity
  4. Righting - sensed by v/o, m/s and pressure sensors, allows us to land the right way up when falling
53
Q

Dysfunction of which reflex causes motion sickness and why?

A

Motion stimulates the vestibular reflex but visual stimulus are static = CONFLICTING –> these centres stimulate the vomiting centres in the brainstem

54
Q

Outline the pathogenic origin of vestibular syndrome.

A

Ear infection leads to imbalances in the vestibular function of one side of the brain. Therefore the animals circle, have nystagmus and a head tilt

55
Q

Name and describe the histological features of the gustatory papillae of the tongue.

In which species are each found in the greatest number?

A
  1. Vallate - Found on the back of the tongue, extensive connective tissue, sulcus between each, mucus glands at bottom of sulcus. Ruminants
  2. Fungiform - Highly vacularised, extensive connective tissue. Carnivores
  3. Foliate - Margin of the tongue, thin papillae with mucus glands in sulcus. None in ruminants.
56
Q

Name and describe the mechanical papillae of the tongue.

What is the general function of mechanical papillae?

A
  1. Filiform - Keratinised spines, elongated and cone shaped (cats)
  2. Conical - Cone shaped at the root of the tongue, contain lymphatics in pigs
  3. Lenticular - Lens shaped, keratinised (ruminants)

Move food bolus caudally (+grooming behaviour)

57
Q

Describe the process of gustation.

(HINT: Gustatory pathway + CNs involved)

A

Tastants bind to microvilli of taste buds (secondary sensory cells), NT released at the base of the bud, transmitted by CN to the brain.

  1. Root - X
  2. Caudal 1/3 - IX
  3. Rostral 2/3 - VII

The gustatory pathways travel via the gustatory nucleus to the gustatory cortex (synapsing in the thalamus) + transmitted to hypothalamus and limbic system.

58
Q

What are tastants? How do they confer different tastes?

A

Chemicals which stimulate gstatory receptor cells: bitter, sweet, salty, sour, umami.

Their patterns of neuronal impulses differ and stimulate different neurones.

59
Q

Describe the histological features of the cells of the vomeronasal organs.

What is the function of the VMO?

Describe the reaction which leads to the VMO sensing these substances.

A
  1. Secondary sensory cells, microvilli, synapses on the accessory olfactory bulb
  2. Detects pheromones dissolved in liquids eg urine
  3. Flehmen reaction - stretch head forwards, curl upper lip, partial nostril blockage, opening of the VNO
60
Q

What are the functions of olfaction?

Describe the process of olfaction and the olfactory pathway.

A
  1. Prey/ predator detection, direction, sexual attraction
  2. Odourants hit mucous before being sensed by secondary sense cells, AP travels through the cribiform plate, synapse with mitral cells of the olfactory bulbs in glomerulus.
  3. CN1 Olf bulbs > Olfactory tract (in peduncles) > splits and sends axons to hypothalamus, RF, piriform lobes (olfactory cortex) & limbic system > decussates to brainstem
61
Q

How do the appendages of the secondary sensory cells of the olfactory and vomeronasal epithelium differ?

A

Olfactory = non-motile cilia, VMO = microvilli

62
Q

What is the glomerulus of the olfactory system?

A

The area of synapse between secondary sensory cells of the olfactory mucosa and the mitral cells of the olfactory bulb.

63
Q

What are the main components of the limbic system?

Describe its function.

A
  • Olfactory bulbs
  • Hippocampus - memory formation
  • Amygdala
  • Thalamus
  • Hypothalamus
  • Basal Ganglia
  • Cingulate gyrus

Coordinates survival drives - homeostasis, emotion and motivation (more space in lower species)

64
Q

This disease causes Negri Bodies to form in the hippocampus. What are the effects of this?

A

Rabies.

These inclusions cause altered levels of aggression

65
Q

The seat of aggression

A

Amygdala - Found closley associated with the hippocampus

66
Q

Functions in decision-making, planning, personality and problem solving.

A

Frontal Lobe

67
Q

Functions in memory formation

A

Hippocampus

68
Q

Spontaneous discharge of activity from hippocampal neurones

A

seisures

69
Q

Storage of information in the nervous system.

Describe the three different types of this characteristic.

A

Memory

  1. Short-term - electrical activity in neurones
  2. Long-term - change in physical and chemical nature of cells
  3. Working - information required to make decision
70
Q

Changes in behaviour due to experience.

Describe the three different types of this characteristic.

A

Learning

  1. Habitual - suppressed stimuli through habit
  2. Sensitisation - enhancing natural reaction to stimuli
  3. Conditioning - operant (trial & error), classical
71
Q

Functions in endocrine regulation.

What are the effects of lesions to this area?

A

Hypothalamus

  • Abnormal appetite
  • Abnormal water intake
  • Odd temperature control
  • Hemi-neglect
72
Q

Functions to stimulate arousal and motivation.

Abnormalities to proteins or receptors involved results in narcolepsy.

A

Orexin

73
Q

Describe the ascending reticular activating system.

A

A collection of nuclei which function in regulating vegetative function - determines arousal levels (focus) and sleep-wake cycles.

Uses information from sensory organs and sends projections to the outer cortex.

74
Q
A

NSF (14 decks)

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