Neuro Anatomy Flashcards
Functions of the Thalamus
- Major relay and integration centre for sensation-all sensory pathways except smell
- Regulation of motor activities of cerebral cortex as it recieves feedback circuits from cerebellum and basal ganglia
- Distributes information to cognitive areas of the cortex
- Alerts cortex diffusely by reticular activating system
- Limbic and hypothalmic connections
Functions of Hypothalamus
- Rostral part has homeostatic control, central parasympathetic control of apetite, thirst, osmoregulation, bladder contraction, gut motility, temperature regulation and sleep regulation
- Caudal part has sympathetic control including stress and emergency mechanisms and initiation of rage
- Controls secretion of hormones via the pituitary
Functions of Tectum
Rostral colliculi recieves input from optic tract and caudal colliculi recieves input from the cochlear nucleus.
Functions
- Control unconcious visual and auditory reflexes
- Integrate spinovisual and spinoauditory reflexes via the tectospinal tract, turning head towards visual and auditory stimulus
- Important extrapyramidal motor command centre
- Alerts cortex to visual and auditory stimuli
Functions of Tegmentum
Contains nuclei of CNIII-IV, red nucleus to do with extrapyramidal motor centre and olfactory and limbic nuclei.
Internal Structures of the Pons
Dorsal pons:
- Nucleus of trigeminal nerve
- Ascending sensory and descending extrapyramidal pathways
- Reticular formation with pneumotaxic and apneustic centres
Ventral pons:
- Descending pyramidal motor fibres
- Transverse pyramidal fibres from motor cortex passing into cerebellum
Functions of Cerebellum
- Flocculondular lobe gives balance and equilibrium
- Caudal lobe for synergy and coordination
- Rostral lobe for muscle tone and posture
Internal Features of Medulla Oblongata
- Nuclei of CN VI-XII, vestibular nuclei which is important in balance and as extrapyramidal motor centre, cochlear nucleus
- Ascending sensory and descending extrapyramidal tracts
- Dorsal and median sulcus by gracile and cuneate fasiculi, carrying concious proprioception from hind and forelimbs respectively
- Reticular formation including tracts which run in pyramids which flank ventral median fissure before decussating and merging caudally
Functions of the Reticular Formation
Ascending:
- Arousal, levels of conciousness, sleep is hypothalmic inhibition
- Transmission of deep and visceral pain as deep pain is slow, poorly localised and outlasts its stimulus. Perception via spinoreticular tract, inhibition by collaterals from cutaneous mechanoreceptors and encephalinergic pathways in descending reticular formation
Descending (Reticulospinal tract):
- Extrapyramidal motor
- Central control of ANS via reticulr spinal tract
The Meninges
- Dura Mater - dense connective tissue, fused to periosteum and in vertebral canal the epidural space separates it form the periosteum. Within cranial cavity forms folds to protect from excessive movement of brain.
- Arachnoid Mater - Thin, following contours of dura due to pressure of CSF in subarachnoid space. Web like filaments of delicate connective tissue.
- Pia Mater - Histologically similar to arachnoid mater and continuous with arachnoid mater but is ciliated to assist in flow of CSF. Both arachnoid and pia firmly attached to dura by denticulate ligaments which arise midway between each spinal nerve root.
Meninges form sleeve around cranial and spinal nerve roots. At end of spinal cord, arachnoid and pia meet. Dura continuous with periostemu of caudal vertebrae.
Spaces Associated with Meninges
- Epidural space - Only in vertebral canal, between dura mater and periosteum, extending beyond the end of the spinal cord. Contains longitudinal venous sinuses and fatty fluids which cushions spinal cord for flexibility.
- Subdural space - Narrow, between dura and arachnoid contianing a tiny amount of fluid
- Subarachnoid space - Between arachnoid and pia, wider and less uniform. Contians CSF. Arterioles and venules supplying brain and spinal cord are located in subarachnoid space. This space used for CSF collection, contrast material and spinal anaesthesia.
Ventricular System
- Lateral Ventricles - paired and lie within cerebral hemispheres, communicate via interventricular foramen with eachother and 3rd ventricle. Smalle recess to olfactory bulb
- Third Ventricle - surrounds the interthalamic adhesion. Sends small recesses into pineal and pituitary
- Mesencephalic aqueduct - in midbrain, connects third and fourth ventricles
- Fourth Ventricle - Hind brain, dorsal to medulla and pons, ventral to cerebellum. Roofed by rostral and caudal medullary velum. Comminucates with subarachnoid space via lateral apetures
- Central canal of spinal cord - continuous with 4th ventricle
Ependymal cells lined with cilia to assist with flow of CSF.
Production of CSF
Most produced at choroid plexus which is tufts of capillaries from subarachnoid space. Protrudes through pia mater into lumen of ventricle, covered in modified ependymal cells. Present in lateral ventricles, roof of third and fourth ventricles.
Also produced directly from brain via ependymal lining.
Absorption occurs at venules in subarachnoid space, arachnoid villi and lymphatics on roots of cranial and spinal nerves
Functions of CSF
- Protective against percussion and pressure
- Osmotic and chemical buffer
- Regulatory- vehicle for metabolites and transmitter substances monitored by ependymal cells
- Nutriotional as neuraxis has special requirements
Blood Brain Barrier
Endothelial cells lining capillaries that penetrate neuraxis have tight junctions, non-fenestrated basement membrane and micropinocytic vesicles.
Astrocyte feet covering much of capillary surface also contributes.
Ligaments of the Vertebral Canal
- Dorsal longitudinal ligament - continuous running over dorsal aspect of each vertebral body and attached to the annulus fibrosus of each intervertebral disc, forms floor of vertebral canal.
- Yellow ligament - between successive arches forming roof of vertebral canal
- Intercapital ligament - between heads of ribs, ventral to dorsal longitudinal ligament
Functions of the Vascular Tunic
- Vascular support of adjacent tissues by choroid
- Suspends lens and regulates its curvature
- Production of aqueous humour
- Adjust pupil size by the iris
5 layers of the Cornea
- Anterior epithelium, stratified squamous, continuous with conjunctiva
- Anterior limiting membrane called Bowman’s membrane with fine collagen fibres
- Substantia propria is thick highly organised collagen layers, continuous with sclera
- Posterior limiting membrane called Descements membrane
- Posterior epithelium of thin squamous
Refractive Media of eyeball
Cornea, aqueous humour, lens, vitreous humour
Layers of Eyelid
Skin
Middle musculofibrous layer - orbicularis oculi, striated sphincter muscle directly below skin
- levator palperbrae originates in orbit and passes over eyeball to enter and elevate eyelid
- tarsus plat like fibrous structure that stabilises edge of eyelid
- tarsal glands
Inner Mucosal Membrane
Functions of eyelid
Protect directly by removing foreign particles
Distribute tear film when blinking
Removal of visual stimuli to facilitate sleep
Nutrition and optics for cornea
Three Layers of Tear Film
Superficial oily layer by tarsal glands
Middle aqueous layer by lacrimal and superficial gland of 3rd eyelid
Glycoprotein layer thin covering of cornea by conjunctival goblet cells
Functions of Auditory (Eustachian) Tude
Equilisation of pressure on either side of tympanic membrane and drainage of secretion of glands lining tympanic cavity to escape.
Structure of the Cochlea
Central bony core (modiolus) contains cochlear nerve.
Spiral bony canal of cochlea divided into 3 channels upper chanel is scala vestibuli, middles is scala media (cochlear duct) and lower is scala tympani.
Dorsal wall of cochlear duct is vestibular membrane single celled layer with highly vascularised wall and stratified squamous epithelium, responsible for maintaining ion composition of endolymph.
Ventral wall, basilar membrane, separating scala tympani and scala media composed of fibrous CT that supports organ of corti.
Branches of Spinal Nerves
- Minute variable meningeal branches
- Communicating rami to sympathetic chain in thoracolumbar region
- Dorsal br to epaxial muscles and skin
- Ventral br to hypaxial muscles, skin of trunk and large plexuses in regions of fore and hind limbs
Brachial and Lumbosacral Plexus Origins
Brachial plexus branches from C6-T2
Lumbosacral branches from L4-S3
Differences Between Pyramidal and Extrapyramidal Systems
Flow of Aqueous Humour
See Notes
Histology of Retina
See Notes
Histology of Macula Utriculi and Crista Ampullaris
See Notes
Histology of the Organ of Corti
See notes
Diagram of Spinal Reflex
See notes
Functions of the Lobes of the Brain
Arterial Circle Supply in Cats, Pigs and Ruminants
Major input into arterial circle is by anastomoses of vertebral and maxillary arteries with the distal stem of the internal carotid.
Structures Associated with Upper Eyelids
Eyelashes/cilia
Pila supra orbitals (eyebrows)
Sebaceous glands and ciliary glands opening into hair follicles
