Neuroanatomy Flashcards
What do the neural tube and neural crest become?
Neural tube = CNS
Neural crest = PNS & DRG (dorsal root ganglia)
What are the 3 layers of the neural tube?
Ectoderm
Mesoderm
Endoderm
(Embryonic germ layers)
What does the notochord do?
Induces the formation of the neural plate
Stimulates mesoderm cells
Stimulates vertebral bodies and intervertebral disks
What are the 3 layers in the CLOSED neural tube?
Ventricular (ependymal)
Mantle
Marginal
What does the Sulcus Limitans do?
Divides alar and basal plates
What are alar and basal plates?
Alar plate - dorsal horns (grey matter)
Basal plate - ventral horns
What’s in the white matter (neurone wise)?
Myelinated axons and Funculi
What’s in the grey matter (neurone wise)?
Cell bodies, unmyelinated axons
What’s in the Funculi (dorsal and lateral)?
Dorsal - sensory fibres
Gracile (hindlimb)
Cuneate (forelimb)
Lateral - mixed sensory and motor
Where will you find SHH and BMPs (sonic hedgehog and bone morphogenic proteins)?
Ventral and dorsal neural tubes respectively
SHH secreted from notochord & floor plate
BMP secreted from superficial ectoderm and roof plate
Which neurones are received in the dorsal horn?
Somatic and visceral sensory (afferent) neurones
Which neurones are in the lateral horn?
Preganglionic cell bodies Autonomic motor (visceral efferent)
Which neurones are in the ventral horn?
Cell bodies of somatic motor (efferent) neurones
Are the telencephalon and diencephalon forebrain or hindbrain?
Forebrain (prosencephalon)
What is the proper name for the midbrain?
Mesencephalon
What is in the Rhombencephalon (hindbrain)?
Metencephalon and myelencephalon
Which part of the brain has deep nuclei, controls initiation of movement (basal ganglia) and establishes memory and emotion (limbic system)?
The cerebrum which is also the largest part if the brain
Where is the cerebellum?
What does it do?
Dorsal surface of pons (it’s highly folded)
It refines movement and coordination
What is found in the cerebral cortex?
Thalamus
Hypothalamus
White and grey matter
(Many ridges gyri & sulci)
What separates the primary motor cortex from the primary sensory cortex?
Cruciate sulcus
What is the Sylvian Gyrus?
Auditory receiving area
What is the path of blood through the head?
Arteries –> meninges –> capillaries/neuronal extracellular fluid & CSF –> used blood to venous sinuses –> veins –> heart
What vessels supply the Circle of Willis
- Internal carotid arteries x2
- External carotid then maxillary x2 (anastamosing ramus)
- Vertebral arteries, rate mirabilis, internal carotid
- Vertebral & spinal through basilar artery direct
5 blood supplies from the Circle of Willis?
Rostral cerebral Middle cerebral Caudal cerebral Rostral cerebellar Caudal cerebellar
Which animals is rete mirabilia present in?
Sheep Goat Of Pig Ruminants Dogs (cavernous sinus) Cats (extracranially)
In which animal is Circle of Willis mainly supplied by maxillary artery?
Cats
The internal carotid becomes vestigial.
(Sheep, cows & pigs also lose internal carotid)
Which animals supply CoW mainly through internal carotid and basilar arteries?
Dog
Man
Which animal has mixed blood in entire brain (from maxillary and vertebral)
The ox
(As both vessels supply the Circle of Willis
Which blood vessels are in the spinal cord?
Ventral spinal artery (on ventral superficial surface)
Dorsal spinal arteries (dorsolateral surface)
Linked by anastamosing arteries
Which molecules are actively transported across the blood brain barrier?
Glucose
Ketone bodies
H20 (aquaporins)
What do astrocytes do?
Regulate the blood brain barrier.
Astrocyte feet surround the brain capillaries and contribute to formation and maintenance of bbb complex.
What are the 3 layers of meninges?
Dura mater (outer) - thick, tough, wraps brain and spine. 2 layers, in the gap = venous sinuses
Arachnoid - thinner, underlying “subarachnoid space” filled with CSF, expanded regions = cisterns
Pia - thin, delicate, follows brain surface, highly vascularised
What is CSF?
Saline containing very few cells and a little protein.
It is derived from blood in choroid plexuses of ventricles.
How does CSF drain?
Arachnoid villi
Absorption by venules in pia/spinal veins/lymphatics
Direct drainage from subarachnoid and venous sinuses
What are signs of disease in CSF?
Increased protein –> nonspecific CNS disease
Decreased glucose –> bacterial/fungal meningitis
Abnormal cell count (above 0) –> pleocytosis
Main sinuses?
Dorsal sagittal sinus
Transverse sinus
Sigmoid sinus
Important veins
Int. cerebral
Vertebral
Int. jugular
Int. maxillary
3 types of neurone (_____polar)?
Bipolar
Multipolar
Pseudo-unipolar
What are Glial cells?
Neuronal support cells
What do oligodendrocytes do?
Produce myelin
Neuronal guidance
What are microglia?
The brain’s macrophages
They are 20% of cellular volume
What do Ependymal cells do?
Line the ventricles
What are the 2 modes of exocytosis?
Recycling
Kiss and run
What does Ionotrophic mean?
What does metabotrophic mean?
Fast, ligand-gated (0.1ms delay)
Slower, G-protein coupled (10ms delay)
What should you do in the event of epilepsy?
Depress synaptic activity
Increase GABA release or effectiveness
Decrease glutamate release or effectiveness
Decrease GABA uptake
Intro analogues of GABA
What is decussation?
Nerve tract crossing from one side of the animal to the other
Define nociception
Sensing a stimulus that is meant to evoke pain
Where are primary sensory neurone cells bodies found?
Dorsal root ganglion (just outside the cord)
What is referred pain?
Pain felt in a different place to the actual injury.
Visceral pain typically felt in skin/muscle
What does the Spinothalamic tract do?
It transmits information to the thalamus about pain, temperature, itch and crude touch.
Explain referred pain
Visceral and dorsal horns = very close to ascending pain fibres or SHARE some ascending fibres.
Therefore, the brain cannot distinguish the 2 sources
Where do pain and temperature ascending pathways cross?
Spinal cord
What are the 3 ascending pathways (somatosensory system)?
Dorsal column
Ventrolateral
Spinocerebellar
Where do touch and proprioception ascending pathways cross?
Medulla
What is the dorsal column famous for?
Touch discrimination
Which tracts does the Ventrolateral ascending pathway contain?
Spinothalamic - Pinprick & thermal pain
Spinoreticular - True pain
(Spinothalamic means spine to thalamus direct via medial lemniscus)
(Spinoreticular means spine to reticular formation then thalamus)
What modalities does the Ventrolateral pathway accept?
All except proprioception
ESPECIALLY PAIN.
What is the spinocerebellar tract for?
Postural reflexes
Muscle and joint proprioceptors
Steps in an ordinary conscious response starting with stimulus?
Stimulus Transmission to brain Integration (thinking) Motor response selection Movement (transmission of response)
Segmental reflex sequence of events?
Stimulus
Processed locally in spinal cord segment
Response evoked without brain
Intersegmental reflex
Stimulus Transmission to brain stem (or another segment) Integration in brain stem/other segment Motor response selection Transmission to limbs Response
Examples of segmental/short loop reflexes
Patellar reflex
Withdrawal reflex
Examples of intersegmental reflexes
Long loop
Tonic neck reflex
Scratching left ear with hind paw
What is proprioception?
Ability to sense position, location and orientation of body and it’s parts
What are mechanoreceptors used for?
Touch
Proprioception
Kinaesthesia
Details of Meissner corpuscle
Perception: Flutter
Small receptive field
Rapidly adapting
Found in superficial epidermal/dermal boundary
Details of Pacinian corpuscle
Perception: Vibration
Large receptive field
Rapidly adapting
Found deep in smooth skin (dermis & subcutaneous)
Details of Merkel disk
Perception: Pressure
Slowly adapting
Small receptive field
Epidermis of smooth & hairy skin
Details of Ruffini organ
Perception: Stretch
Large receptive field
Slowly adapting
Found in deep skin
What do orthodromic and antidromic mean?
Impulse travelling in normal direction and reverse direction respectively
Why is pain from inflammation increased?
Lewis’ Triple Response
Antidromic neurotransmission
List the 12 cranial nerves in order
OOOTTAFVGVAH
Olfactory Optic Occulomotor Trochlear Trigeminal Abducens Facial Vestibular Glossopharyngeal Vagus Accessory Hypoglossal
What is the olfactory nerve responsible for?
Autonomic sensory smell
What is the optic nerve responsible for?
Autonomic sensory vision
What is the occulomotor nerve responsible for?
Autonomic motor iris
Somatic motor eye & lid
What is the trochlear nerve responsible for?
Somatic motor eye
What sis the trigeminal nerve responsible for?
Somatic sensory face
Special chew
What is the abducens nerve responsible for?
Somatic motor eye
What is the facial nerve responsible for?
Autonomic sensory tip-taste
Somatic motor ear
Special smile
What is the vestibular nerve responsible for?
Aka auditory
Autonomic sensory hear & balance
What is the glossopharyngeal nerve responsible for?
Autonomic sensory back-taste Blood pressure Autonomic motor saliva Somatic motor neck Special neck
What is the vagus nerve responsible for?
Autonomic sensory visceral pain
Autonomic motor viscera
Somatic motor throat
Special throat
What is the accessory nerve responsible for?
Somatic motor neck/throat
Special neck
What is the hypoglossal nerve responsible for?
Somatic motor tongue
Reflex to test cranial nerve I, olfactory?
Aversion
Something smelly under nose –> reaction
Reflex to test cranial nerve II, optic?
Menace
Does animal blink as hand approaches
Reflex to test cranial nerve III, occulomotor?
Pupil constriction
What causes a strabismus?
Damage to cranial nerve III, IV, VI
Which cranial nerve is responsible for droopy jaw?
V, trigeminal
Reflex to test cranial nerve VI, trigeminal?
Touch palpebral, blink
What is the labyrinth?
Vestibular apparatus
What does the labyrinth do?
Detects movement and angle of head with respect to gravity
What are the 2 components of the labyrinth?
Semicircular canals - with ampullae containing hair cells to detect rotation
Otoliths - with utricles and sacculi (also contain hair cells) detect head acceleration with respect to gravity
How do hair cells in the labyrinth work?
Have stereocilia which make contact with endolymph solution
They are depolarised and hyperpolarised by movement
What is Nystagmus?
Involuntary eye movements
3 tunics in the eye?
Inside - Out
Retina
Vascular (uvea)
Fibrous
What are retinal neuroepithelial cells?
Rods and cones
What forms the optic nerve?
Axons of retinal ganglion cells
What happens when the choroid fissure doesn’t fuse properly?
Haemorrhage, blindness.
E.g. Collie eye anomaly
Where do the eyes develop from?
Neural tube region containing retinas - optic cups
Ectoderm of forebrain
Neural tube closes
Optic vesicles grow towards surface ectoderm & thicken –> lens placodes.
What does the outer optic cup layer become?
Pigmented retina & inner nervous retina
What is the cornea derived from?
Mesoderm and surface ectoderm
What are the layers of the retina?
Pigment layer - epithelial cells
Nervous layer - 3 layers inc light sensitive cells
What is the path of visual data processing?
Pigmented epithelial cells Photoreceptors cells Bipolar cells Ganglion cells (Opposite way = path of light through retina)
What is the Fovea?
Where is it?
Area of greatest visual clarity
1:1 synaptic contact
Bipolar ganglion cells displaced (easy for light to pass through)
Only cones
Fovea is found straight behind the lens with high density cones and no blood vessels
Blind spot
Axons from optic nerve II at the optic disk
Where ganglion cells leave retina (no sensory cells)
What is the choroid?
Vascular layer
Vessels branches/offshoots to supply photoreceptor layer of retina
It is heavily pigmented
What do central vessels supply in the eye?
Bipolar and ganglion layers of the retina
What do choroid vessels in the eye supply?
Photoreceptor layer of retina
What is the Tapetum Lucidium?
Cells containing crystals lying between pigment layer and choroid
It is a triangular area of greenish yellow light reflecting iridescent cells lying dorsal to the point where the optic nerve leaves the eye
What is found in the vitreous chamber?
Vitreous humour
Characteristics of the sclera
Characteristics of the cornea
White, highly fibrous, elastic
Continuous with sclera
What is the ora serrata?
Where photoreceptors end
What happens in the lens for distance vision?
Relaxed ciliary body
Lens fibres taut
Lens flat
What happens in the lens for close vision?
Ciliary body contracted
Fibres slack
Spherical lens
Formation and drainage of aqueous humour in the eye
It is formed by filtration of blood plasma by ciliary processes
Fluid leaks through the pupil from posterior to anterior chamber
Fluid returns to the circulation via venous plexus at the transition between cornea and sclera
What is a cataract?
Lens becomes cloudy due to age genetics or diabetes
Can be accompanied by displacement. Of lens from normal into anterior chamber (lens luxation)
What is glaucoma?
Raised intraocular pressure
Aqueous humour drainage blocked & production continues
Blindness - pressure impedes circulation killing off retinal cells & can compress and damage optic nerve
Treat with drugs diffused into the eye to decrease humour secretion
Cell types in cornea?
Conjunctival epithelium Limbus Anterior epithelium of cornea Corneal fibrocyte Substantia propria
Describe the anterior epithelium
Moderately thin, Stratified, Non keratinised, Squamous epithelium
Describe substantia propria
Thick, dense, collagen in thin layers
What is keratoconjunctivitis sicca?
Dry eye
Autoimmune failure of tear production
Treat with immunosuppressant & artificial tears
How would you treat corneal ulceration?
Conjunctival pedicel graft
What is conjunctivitis?
Inflammation of conjuntival membranes
Viral & bacterial infection
What is cerumen?
Ear wax
What is otitis externa?
Inflammation of the ear canal
Caused by mites or bacterial/fungal infection
What does the middle ear do?
Transmits sound waves from the outer ear to the inner ear
What does the ear drum do?
Convey’s sound vibrations from ear canal to ossicles
What is the Tympanic Bulla
Air filled cavity
What does the auditory tube do?
Connects nasopharynx to middle ear & equalises pressure on both sides of drum
What are ossicles?
What is their function?
The stirrup, anvil and hammer
Tiny flexible chain connecting drum to oval window
Convert middle ear vibration to electrochemical signals
(Balance, sensing position of head in space)
What is in the bony labyrinth?
Vestibule
Semicircular canals
Cochlea
What is in the membranous labyrinth (which is inside the bony labyrinth)
Utricles and saccules (inside vestibule) - balance Semicircular ducts (inside canals) - balance Cochlear duct (in cochlea) - hearing
Where is the Organ of Corti?
What does it do?
It is found In the round window
It transducers pressure waves to action potentials
