Brain and Nervous System Flashcards
What are the three primary divisions? And what do two of the divisions further differentiate into? (5 subdivisions)
What is the subscapular nerve? What does it innervate?
C6, C7. Subscapularis (adducts and extends shoulder joint)
Dorsally, what divides the brain into what parts?
What is the brachial plexus made up of?
Made up of mixtures of the ventral roots of spinal nerves C6- T1 (and often T2).
What is the cranial pectoral nerve? What does it innervate?
C6, C7, C8
Superficial pectoral
What is the suprascapular nerve? And what does it innervate? Why is it important?
C6, C7.
Lateral muscles of the shoulder and scapula, stabilizers, flexors, and extensors of shoulder- supraspinatus, infraspinatus
If they run into something- they can damage it. And lose support for the shoulder.
What is the musculocutaneous nerve? What does it innervate?
C6, C7, C8.
Innervates the cranial muscles of the arm. Flexors of elbow, extensors of the shoulder- biceps brachii, coracobrachialis, brachialis.
What is the axillary nerve? What does it innervate?
C7, C8. Caudal muscles of the scapula and shoulder- flexors of the shoulder- deltoideus, tere major and minor, (subscapularis)
What is the radial nerve? What does it innervate?
C7, C8, T1, (T2)
Caudal muscles of arm- extensors of elbow- triceps brachii- cranial muscles of forearm- carpal and digital extensors.
What is the median and ulnar nerve? What does it innervate?
C8, T1, (T2)
Caudal muscles of the forearm- carpal and digital flexors
What is the caudal pectoral nerve? What does it innervate?
C8, T1, (T2)
Deep pectoral
What is the thoracodorsal nerve? What does it innervate?
C8. Latissimus dorsi.
Where is the sensory innervation of the axillary nerve?
Lateral brachium and caudal scapular region.
Where is the sensory innervation of the musculocutaneous nerve?
Medial brachium and antebrachium
Where is the sensory innervation of the radial nerve?
Lateral antebrachium and manus; dorsal surface of the paw
Where is the sensory innervation of the median and ulnar nerves?
Palmar surface of the paw
What is the obturator nerve? What does it innervate? Why is this nerve important?
L4-L6
Adductor muscles: external obturator, pectineus, gracilis, adductor
Goes through the obturator foramen. Foetus’ go through pelvic canal- so it can bruise this nerve. Cannot adduct leg- cannot stand up.
Where does the lumbosacral plexus go?
Arises from the ventral branches of the caudal lumbar and sacral nerves L4 to S3.
What is the femoral nerve?
L4-L6. Hip flexors, stifle extender, iliopsoas, sartorius, quadriceps
What is the caudal gluteal nerve? What does it innervate?
L6-S2. Hip extensor. Superficial gluteal.
What is the cranial gluteal nerve? What does it innervate?
L6- S2.
Hip extensors and abductors. Middle and deep gluteal, tensor fasciae latae.
What is the sciatic nerve? What does it innervate?
L6-S2. Pelvic limb rotator (out), gemelli, quadratus femoris, internal obturator.
What is the sciatic nerve- muscular branch? What does it innervate?
L6-S2. Semimembranosus, semitendinosus, biceps femoris.
What is the common peroneal nerve- branch of the sciatic nerve? What does it innervate?
L6, L7. Cranial leg muscles- flexors of tarsus, extensors of digits, cranial tibial, long and lateral digital extensors, extensor hallicus longus, extensor digitorum brevis, peroneus longus, peroneus brevis
What is the tibial nerve- branch of the sciatic nerve? What does it innervate?
L7, S1. Caudal leg muscles- extensors of the tarsus and digital flexors. Gastrocnemius (both heads), superficial digital flexor, popliteus, superficial and deep digital flexors.
Where is the sensory innervation of the lateral cutaneous femoral (mainly L4)?
Cranial thigh.
Where is the sensory innervation of the genitofemoral (obturator in large animals)?
Inguinal region, proximal medial thigh, part of prepuce (skin on penis)
Where is the sensory innervation of the femoral- saphenous?
Medial leg (thigh to paw)
Where is the sensory innervation of the pudendal- perineal? How about the dorsal nerve of the penis/clitoris?
Pudendal- perineal: anus, perineum as far as the scrotum or labia (may mean a lot of trouble with the spinal cord if damaged)
Pudendal- dorsal nerve of the penis/clitoris- penis clitoris
Where is the sensory innervation of the caudal cutaneous femoral (S2, S3)?
Proximal, caudal half of thigh.
Why are nerves running in a wavy fashion?
So you can straight your arm without damage, for example.
Laryngeal hemiplegia. Left dorsal cricoarytenoid muscle. Left recurrent laryngeal nerve.
Wallerian Degeneration.
Injury (stretching, compressive force, laceration or fraying)–> nerve cell body swells–> Nissl granules (RER) dispersed (therefore it looks pink, instead of blue tinge)–> Nucleus is not centralized anymore–> Axon swells from injury down (axonal spheroids)–> myelin starts to retract so you get a clear halo around the axonal spheroid–> blood monocytes to macrophages (if we were in the CNS microglia)–> gitter cells (the macrophages with rubbish inside)–>Schwann cell mitosis for regeneration (provide neurotrophic factors to help the axonal ends to mend)–> “axonal sprout” one per injured axon (schwann cells, basal lamina of schwann cell and endoneurium- GUIDES axonal tip so it know where it is going)–> if the nerve cell body does not survive or if you have severed peripheral nerve and there is a gap between the end– you’ve lost the endoneurial tube to guide the schwann cells– axonal sprouting will occur and schwann cells will proliferate but it won’t connect.
Amputation Neuroma.
Regeneration following Wallerian Degeneration. Axonal sprouts with no where to go.
Amputation Neuroma.
Regeneration following Wallerian Degeneration. Axonal sprouts with no where to go.
Most likely problem
Peripheral nerve trauma of the radial nerve.
Heiffers mated with large breeds. Can be unilateral or bilateral. Compressive injury to the Obturator nerves.
To make it worse- downer cow- secondary complications. Peroneal nerves, main Sciatic nerves (caudal aspect of the thigh). AND vascular problems- gravitation pooling, venous stasis, and shear weight of the animal pressing on the nerves… ischaemia etc.
Dystocia causes tearing of femoral nerves. Often right hind leg. Can be bilateral. “Femoral nerve paralysis”
Hope for axonal sprouting and repair.
Cauda equina syndrome. Vertebral canal or foramina can be too narrow. Or acquired disease of the vertebrae or discs that narrow over time, the space for the nerve roots.
Low hind limb carriage. Pinching the nerve roots.
Two possible causes
Trauma or degenerative neuropathy.
Left recurrent laryngeal. Cricoartytenoid muscle.
* Very long nerve- long necked horses. Evidence in Wallerian degeneration in newborn foals- could be traumatic in utero.
Arthrogroposis.
Most likely cause is congenital problem with innervation of skeletal muscles.
Optic nerve hypoplasia with microphthalmia (abnormally small eyes) due to inadequate development of the optic cup from the embryonic forebrain (prosencephalon)
Congenital colonic agangliosis
Lethal white foal syndrome. Inherited as an autosomal recessive trait in white foals born to parents with spots. Ganglia are absent in the myenteric plexus of teh distal ileum, caecum, and colon–> absence of peristalsis–> segmental intestinal stenosis with proximal accumulation of meconium and gas–> colic and death usually within 48 hours of birth
Dancing Doberman Syndrome
Distal segments of long peripheral axons (Wallerian Degeneration)
Weakness, lethargy, exercise makes it worse
Can be inherited (born without enough Acetylcholine receptors) or acquired (mounting antibody attack against Acetylcholine receptors)- can be generalized or localized.
* Acquired- strong associated with thymomas. Paraneoplastic syndrome.
* Trigger in humans- bacterial infection. Antibody response attacks the bacteria but also the Acetylcholine receptors
Weakness, lethargy, exercise makes it worse
Can be inherited (born without enough Acetylcholine receptors) or acquired (mounting antibody attack against Acetylcholine receptors)- can be generalized or localized.
* Acquired- strong associated with thymomas. Paraneoplastic syndrome.
* Trigger in humans- bacterial infection. Antibody response attacks the bacteria but also the Acetylcholine receptors
Endocrine disease manifests as a peripheral neuropathy. Possibly antigens on the tumour cells themselve cause the body to mount an immune response that also attack the PNS.
e.g. Diabetes, Hyperadrenocorticism, Hypothyroidism
Guttural pouch infection or aspergillous infections (necrotising). Can spread to cranial nerves, for example.
Idiopathic polyridiculoneuritis. (referring to dorsal and ventral spinal nerve roots)– often ascending. Progressive. Inflammation of peripheral nerves, may accompany.
used to be called: Coon Hound Paralysis.
10 days after being bitten by a raccoon. Paralysis of intercostal muscles–> death.
* may thought to be autoimmune. Just a coincidence with whatever is in raccoon saliva (first recognized trigger, but now multiple known). Vaccines can induce syndrome in humans. Or previous viral infection.
Toxins that target nervous system
Ixodes holocyclus (target is the NMJ- release of AcH across the nerve endings), botulinum toxin (same pathogensis), lead (paint), chronic OP poisoning (Wallerian degeneration and inadequate regeneration)
Stringhalt.
Exaggerated flexion (unilateral or bilateral hind limbs). Peripheral nerves- esp. Peroneal and tibial nerves. are really long in the hind limbs of horses. Denervation atrophy of affected muscles– often Digital flexors or long lateral extensors of the hind limbs.
Two forms- one can occur anywhere in the world- bad prognosis. In AUS, often an outbreak in summer and early autumn (Dandelions or mallow possibly)
Grass sickness. Neurons in autonomic ganglia. UK. Degeneration and sometimes loss of autonomic ganglia. Sometimes just repeat bouts of colic. Could be clostridial botulinum toxin.
Peripheral nerve sheath tumours.
Schwann cells +/- other components. Can be benign or malignant. Even if they are malignant, they are unlikely to metastasize. However, wide surgical incision is necessary.
Peripheral nerve sheath tumours.
Schwann cells +/- other components. Can be benign or malignant. Even if they are malignant, they are unlikely to metastasize. However, wide surgical incision is necessary
* Depending on what nerve is what damage you will see.
* Cattle often get multiple peripheral nerve sheath tumours- believed to be inherited. Sometimes visceral nerves as well.
Lymphoma.
Merek’s Disease
Herpes virus induced lymphoma.
Can involve CNS, PNS (visceral, brachial plexus, sciatic nerve)
Vascular supply of the brain and spinal cord
end arterioles. Good anatamosing plexus on the outside of the brain and spinal cord. But once branches go off internally- end arteries. Prone to thrombosis or thromboembolism and ischaemic necrosis.
* Internally- small and easy to compress.
* Cervical spinal cord and thoracic spinal cord- known area of susceptibility to ischaemia. Changing of vascular supply. Changeover point.
Surprising:
** White matter is better supplied then grey matter
** Ventral part of the grey matter is most susceptible to ischaemic injury– motor portion.
** Venous infarcts are less common- good anastamoses. though arterial infarcts are common
Wallerian degeneration.
Schwann cells of the CNS
Oligodendricytes
1 oligodendricytes can myelinate 50 adjacent axons. The opposite to schwann cells in the PNS.
If there is damage, oligodendrictyes are the first to go.
* repair is much less likely in CNS
Ascending Haemorrhagic Myelomalacia (though descending is also part of it BUT ascending is the more important part because it is going towards the brain)
Due to secondary ischaemic injury- worst case event.
Couldn’t unkink the cervical vertebrae. Horse crashed on the racetrack.
Fractured vertebral body, sharp fragments have gone dorsally, didn’t severe the dura mater, squashed the spinal cord. The reason it was so difficult to straighten- it has ripped the synovial joints on the right hand side- cut through joint capsule- and the two articular facets- so complete luxation on one side.
* Died within minutes because of cervical sympathetic nervous trunk regarding vasomotor respiratory centres- so it all would have shut down.
