CNS Flashcards
What is grey matter made of?
cell bodies, dendrites and meninges.
What is white matter made of?
axons
What are glial cells?
supporting cells in the CNS
What are ganglia?
clusters of cell bodies in the PNS.
What are tracts?
bundles of axons in the CNS
What are nerves?
bundles of axons in the PNS
What is decusation?
where the right side of the body is handles by the left side of the brain
What is the function of the CNS?
afferent information from and efferent output to the PNS
What are the two basic regions of the brain?
cerebrum and cerebellum
What are the ridges and furrows called on the cerebrum?
ridges- gyri (gyrus) and furrows- sulci (sulcus)
What is the function of the rhinencephalon?
Olfaction (smell), behaviour and communication
Where is the white and grey matter in the cerebellum?
grey matter forms folia, white matter branches
grey on outside, white on inside
What are the major regions on the CNS?
cortical region, deep cerebral region, brain stem and cerebellum
What are the main functions of the cortical region of the CNS?
motor, somatosensory, auditory, visual and olfactory functions
frontal cortex- planning, decision making, motivation and personality
some areas of association cortex to integrate experiences with memory and emotion
What is the main components of the deep cerebral region of the CNS?
limbic system
basal nuclei
thalamus
hypothalamus
What is the function of the limbic system?
emotion, learning and memory
What is the function of the basal nuclei (from the corpus striatum)?
planning and executing movement
What is the function of the thalamus?
relay point for sensory information coming into the brain (except olfactory input), involves in sleep and wakefulness
What is the function of the hypothalamus?
connects endocrine and nervous system, importance in behaviour through the limbi system
what is the brain stem composed of?
midbrain, pons and medulla
what is the brain stem the key control centre for?
cardiovascular, respiratory and gastrointestinal function
Where are the nuclei for most cranial nerves?
in the brain stem
What is the function of the tectum in the midbrain?
orientation of the head and body in response to sight and sound
What are the main functions of the cerebellum?
organises and refines motor activity, compares intended movements with the outcome, balance and coordination
What are meninges?
three thin layers of tissue that cover and protect the brain and spinal cord
What are the three layers of meninges?
Outer to inner- dura mater, arachnoid mater, pia mater
What is the function of the meninges?
protect the brain and spinal cord, facilitate the flow of CSF, provide a framework for blood vessels to supply CNS tissues.
Describe the dura mater
2 layers of endosteal and meningeal
pain sensitive through CN V innervation
has its own blood supply
Describe the arachnoid mater
Avascular, closely associated with the dura mater, subarachnoid space contains CSF and blood vessels.
Describe the pia mater
Highly vascular and delicate, tightly adhers to the underlying tissue, follows blood vessels into tissues and merges with tunica adventitia
What are cuffs?
Formed by the layers of meninges around the roots of cranial and spinal nerves as they penetrate the membranes.
What is the composition of CSF?
no cells, no proteins, low amino acid content, low and stable potassium ion content, low glucose content
How is CSF produced?
Ependymal cells pump solutes into the CSF to draw water in by osmosis.
Lipid soluble substances pass into the CSF. Water soluble materials must be actively transported into the CSF (glucose)
What is the function of CSF?
provides nutrition to CNS tissues, acts as a cushion and lends to CNS physical support, acts as a volume buffer, maintains a stable environment for neurones, helps movement of neurotransmitters around the CNS
Where is CSF made?
Choroid plexi
Where is CSF drained?
reabsorbed into the circulation at arachnoid villi
Describe the circulation of CSF
Circulates through subarachnoid space, ventricles of brain and central spinal canal. Ventricles and central canals lined by ependymal cells which possess cilia
What is the source of blood for the cerebral arterial circle in dogs and horses?
internal carotid rostrally and basilar artery caudally
What is the source of blood for the cerebral arterial circle in sheep and cat?
majority from maxillary artery via a rete mirabile
What is the source of blood for the cerebral arterial circle in ox?
maxillary artery and vertebral artery via 2 retia
What are the clinically important species differences in the arterial supply of the CNS?
Sheep lose consciousness almost immediately after having their jugular and carotid veins in a throat slashing for slaughter, whereas a cow can take up to 85 seconds to lose consciousness and the brain is still being supplied blood by the vertebral artery.
What is special about the venous flow in the CNS?
blood flow in either way, can be intermittent, can accommodate changes in blood volume to maintain cardiac preload and provide alternate drainage channels if there is jugular compression
What are the three layers of the eye?
fibrous, vascular and neural
what is the interior of the globe of the eye divided into?
anterior and posterior segments
what contains aqueous humour?
the anterior segment of the eye
what contains vitreous humour?
the posterior segment of the eye
what is the function of the eyelids?
protect the eye, produce the lipid component of the tear film and spread and move tears over the eye surface, remove foreign material from the eye, close to exclude light
what is the gap between the eyelids called?
the palpebral fissure
what are the corners of the eye called and what ligaments hold these points?
canthi- held by medial and lateral ligaments
which cranial nerve controls movement of the eyelids?
facial nerve (CN VII)
what is the function of the conjunctiva (eye)?
covers inside of lids and front of eye except the cornea, contains goblet cells that produce the mucin component of tear film
where is the nictitating membrane found?
at the ventromedial canthus
what does the nictitating membrane do?
closes when the eyeball retracts
what supports and covers the nictitating membrane?
supported by cartilage and covered in conjunctiva
what does the gland in the base of the nictitating membrane do?
produces some of the aqueous components of the tear film
what are the three components of tears?
mucin, lipid and aqueous
what drains tears?
drained via lacrimal punctae and nasolacrimal duct into nasal cavity
what is the sclera made of?
tough fibrous tissue
where are the sclera and the cornea, and where do they meet?
opaque sclera caudally and transparent cornea rostrally
meet at the limbus
where do the axons from the retina go?
they pass through the sclera at the lamina cribosa and form the optic nerve (CN II)
what is the cornea?
the transparent, curved, rostral surface of the eye
what does the cornea do?
refracts and transmits light
where is the vascular tunic?
what is another term for the vascular tunic?
sits between the fibrous tunic and neural layer in the caudal part of the eye
termed the uvea
what is the anterior uvea made of?
iris and ciliary body
what is the posterior uvea?
the choroid
what is the iris?
a sphincter with constrictor and dilator muscles that alter the size of the pupil to vary the amount of light entering the eye
is constriction of the pupil under sympathetic or parasympathetic control?
what is another term for pupil constriction?
parasympathetic
miosis
is dilation of the pupil under sympathetic or parasympathetic control?
what is another term for pupil dilation?
sympathetic
mydriasis
what are the functions of the ciliary body?
production of aqueous humour from the ciliary processed, drainage of aqueous humour via a venous plexus, anchors the lens via zonular fibres, changes the size and shape of the lens to alter depth perception via action of the ciliary body movement
what controls depth perception?
ciliary body
what is the function of the choroid (posterior uvea)?
provides blood supply to deep layers of the retina, has several layers including the tapetum lucidum
where is the choroid (posterior uvea)?
lies between the sclera and retina
what does the tapetum lucidum do?
reflects light to give improved night vision
where is the lens attached?
attached to the ciliary processes by zonular fibres
what does the lens do?
refracts light and can change depth of focus
what is it called when the lens becomes opaque instead of transparent?
cataract
what does the retina do?
converts light into action potentials
what are the four layers of the retina?
- retinal pigment epithelium (RPE)- non pigmented, over tapetum lucidum
- photoreceptor cells (rods and cones)
- bipolar ganglion cells
- multipolar ganglion cells
ganglion cell axons are unmyelinated and come together at the optic disc to form the optic nerve
how is an image made in the brain?
pupil constricts/dilates to alter light entry into the eye
cornea and lens refract light
light projects onto retinal photoreceptors
image focussed on retina is inverted (brain corrects)
what does the aqueous humour do?
provides nutrition for posterior cornea and anterior lens
what is aqueous humour made of?
ultrafiltrate of plasma
where is aqueous humour produced and drained?
produced- ciliary processes of ciliary body
drained- iridocorneal angle
what happens if there is disrupted drainage of aqueous humour?
intraocular pressure increases, called glaucoma (emergency)
what is vitreous humour made of?
hydrogel, containing protein fibrils and hyaluronic acid
how is transparency of vitreous humour maintained?
lamellar arrangement of fibrils
where is the vitreous humour attached?
caudal lens capsule, ciliary body and periphery of optic disc
what can disruption/dislocation of vitreous humour lead to?
retinal detachment
what are the major species differences regarding the eye?
field of vision
adnexa (shape of the eye etc)
cornea (ungulates (hooved herbivores) have horizontal cornea compared to round cornea of carnivores)
iris and pupil (slit pupil of cat vs round pupil of dog)
What is integuement?
skin
what are the main functions of integuement?
thermoregulation, secretion, sensory input, pigmentation, vitamin D metabolism
