Neuroanatomy Flashcards
Components of GSA system (2)
all spinal nerves
CNV
Components of SSA (2)
Vision CNII
Hearing CNVIII
Components of GVA (2)
spinal nerves (splanchnic branches)
CN VII, IX, X
Components of SVA (2)
taste: CN VII, IX, X
smell: CN I
Components of GP (general proprioceptive) system (2)
all spinal nerves
CN V
Components of SP (special proprioceptive) system (1)
vestibular system (CN VII)
Components of GSE system (2)
all spinal nerves
CN III, IV, V, VI, VII, IX, X, XI, XII
Components of GVE system (3)
sympathetic: spinal nerves, splanchnic nerves
parasympathetic: sacral spinal nerves
CN III, VII, IX, X
Where is the dendritic zone of the SA system located?
on or near the surface of the body derived from the somatopleura, where it receives the various stimuli from the external environment.
Where is the dendritic zone of the VA system located?
in the wall of the various viscera of the body. This tissue is derived mostly from splanchnopleura and is stimulated by changes in the internal environment.
Where is the dendritic zone of the general proprioceptive (GP) system located?
in receptor organs located in muscles, tendons, and joints deep to the body surface. This system is distributed widely throughout all the spinal nerves and the fifth cranial nerve.
Where is the dendritic zone of the special proprioceptive (SP) system located?
receptors specialized to respond to positions and movements of the head. They are located in a portion of the membranous labyrinth of the inner ear.
Where is the telodendron of the GSE system located?
voluntary striated skeletal muscle through the entire body
Where is the telodendron of the GVE system located?
in involuntary smooth muscle of viscera derived from splanchnic mesoderm as well as blood vessels, cardiac muscle, and glands. This system is the lower motor neuron of the autonomic nervous system
What is the meningovertebral ligament?
In some locations along the spinal cord, there is a robust attachment of the ventral dura mater to the periosteum on the midline of the dorsal surface of the vertebral body within the vertebral foramen
Name the 3 meninges
1) Dura mater - pachimeninx
2) Arachnoid mater
3) Pia mater
pia + dura = leptomeninges
Real spaces associated with the meninges? (2)
1) epidural (only spinal cord)
2) subarachnoid
Potential (pathologic) spaces associated with the meninges? (2)
1) Subdural
2) epidural in brain
Three intracranial dural folds?
1) falx cerebri (a)
2) tentorium cerebelli (b)
3) diaphragma sellae turcice (c)
What are subarachnoid cisterns and name 4
wider separations of the arachnoid and pia membranes
1) cerebellomedullary
2) lumbar
3) quadrigeminal
4) intercrural (between crux cerebri)
Functions of the pia mater (2)
1) suspension of neural tissue
2) pathway for blood vessels into parenchyma
Pia mater ligaments that suspend the spinal cord (2)
1) denticulate ligaments (laterally)
2) filum terminale (caudally)
Where does the internal carotid artery enter the subarachnoid space to form the arterial circle?
between the optic chiasm and hypophysis
Three (3) divisions of the internal carotid artery?
rostral cerebral a.
middle cerebral a.
caudal communicating a.
Which main arteries form the arterial circle (circle of Willis)?
basilar a. (caudal)
L and R internal carotid a. (rostral)
Which artery do the internal ethmoidal and ophtalmic arteries arise from?
the initial portion of the rostral cerebral a.
What is supplied by the middle cerebral arteries?
the entire lateral surface of the respecting hemisphere
What is supplied by the rostral cerebral arteries?
the rostral gyri on the medial side of the cerebral hemispheres
What is supplied by the striate arteries/branches?
- basal nuclei
- rostral thalamus
- adjacant deep white matter tracts
From which arteries does the caudal cerebral artery arise?
the caudal communicating arteries
What is supplied by the caudal cerebral arteries (3) ?
1) the medial surface of the caudal portion of the cerebral hemispheres
2) diencephalon
3) rostral mesencephalon
Which species has the blood supply to the arterial circle via the internal carotid and basilar arteries?
dogs, horses (and humans)
Which species have blood supply of the brain through the maxillary artery?
cats
ruminants
What is the rete mirabile?
a plexus like vascular structure that lies extracranially and communicates with brain arterial circle through the orbital fissure
Which blood vessel forms the rete mirabile
the maxillary artery
Which strutcures are supplied by the internal carotid artery? (3)
1) brain
2) retina
3) inner ear
Where are the dural sinuses located?
between the periostal and meningeal layer of the dura mater
Where are the ventral internal vertebral venous plexus located (in respect to meninges)?
epidural connective tissue
Two most important large vein systems of the brain?
1) Dorsal system: drains the cortex of the cerebrum, the cortex of the cerebellum, the deeper telencephalon, part of the diencephalon, and the tectum of the midbrain
2) ventral (basilar) system: drains the bulk of the brainstem
Which species has a partially divided dorsal sagittal sinus?
horse
Two most important sinuses of the dorsal aspect of the brain?
dorsal saggital sinus
straight sinus
Most important venous sinuses of the ventral part of the brain
the cavernous sinuses
Name the unpaired bones of the neurocranium (4)
etmoidal bone
sphenoid bone
occipital bone
interparietal bone
Name the paired bones of the neurocranium (3)
parietal bones
temporal bones
frontal bones
The roof of the neurocranium is formed by which 3 bones?
temporal bones
parietal bones
interparietal bone
Which bone forms the lateral view of the neurocranium?
the temporal bone
Which bones form the floor of the neurocranium? (2)
- sphenoid bone
- basilar part of occipital bone
Which bone forms the nuchal wall of the neurocranium?
Occipital bone (lateral part and squamous part)
Which bone forms the nasal wall of the neurocranium?
the ethmoidal bone
Name 2 parts of the sphenoid bone
presphenoid
basisphenoid
Which bone houses the optic canal?
presphenoid bone
Which bones (3) form the tentorium osseum cerebelli in carnivors and horse?
- interparietal bone (processus tentoricus)
- temporal bone (processus tentoricus)
- occipital bone (processus tentoricus)
Which bone houses the middle and inner ear?
Petrosal bone
1) pars petrosa (inner ear)
2) pars timpanica (middle ear)
Which nerve exits thru the stylomastoid foramen, and which bone is this foramen located in?
Facial nerve
Temporal bone (pars squamosa)
Which cranial nerves pass thru the jugular foramen?
CN IX, X, XI
What foramen does the CN XII pass thru?
hypoglossal foramen
Which nerve exits thru the oval foramen?
CN V (mandibular branch)
Which foramen does the internal carotid a. enter the neurocranium?
carotid foramen
What is shown in the image?
fossa of the lacrimal sack (connects to the nasolacrimal canal)
What is shown in the image?
maxillary foramen (entrance of the maxillary nerve)
What is shown in the image?
entrance: maxillary foramen
end: infraorbital foramen (here the maxillary nerve becomes the infraorbital nerve)
What is shown?
Sphenopalatine and caudal palatine foramina
What is shown?
optic foramen
What is shown?
orbital fissure
What is shown?
rostral alar cannal
What is shown?
the alar canal (rostral and caudal alar foramina) (maxillary a. + v.)
What is shown?
oval foramen (CN V - mandibullar branch)
What is shown?
Stylomastoid foramen (CN VII)
What is shown?
the mastoid foramen (caudal meningeal a.)
What is shown?
the jugular foramen (CN IX, X, XI)
Name at least 5 sulci of the brain
marginal
ectomarginal
suprasylvian
ectosylvian
pseudosylvian
rostral lateral
caudal lateral rhinal
ansate
coronal
cruciate
presylvian
Name at least 5 gyri of the brain
marginal
ectomarginal
suprasylvian
ectosylvian
sylvian
postcruciate
precrutiate
prprean
Name the lobes (areas) of the brain
frontal
parietal
temporal
occipital
piriform
Function areas of the frontal lobe
motor cortex
somatosensory cortex
Function areas of the parietal lobe
cognition
motor cortex
somatosensory cortex
Function areas of the temporal lobe
memory
audition
vestibular
taste
Function areas of the occipital lobe
vision
Function areas of the piriform lobe
olfaction
Which sulcus is the border between the frontal and parietal lobes?
cruciate sulcus
Name the structures
Ventral view of brain, cranial nerves, and brainstem.
1, Olfactory bulb;
2, olfactory peduncle;
3, medial olfactory tract;
4, rostral perforated substance; 5, lateral olfactory tract;
6, lateral olfactory gyrus;
7, rostral rhinal sulcus;
8, tuber cinereum;
9, piriform lobe;
10, mammillary bodies;
11, caudal rhinal sulcus;
12, crus cerebri;
13, pons, transverse fibers;
14, ventral paraflocculus;
15, flocculus;
16, dorsal paraflocculus;
17, ansiform lobule;
18, trapezoid body;
19, pyramids;
20, ventral median fissure;
21, decussation of pyramids;
22, caudal perforated substance in interpeduncular fossa;
23, infundibulum;
24, optic tract;
25, optic chiasm;
26, medial rhinal sulcus;
I, olfactory nerve;
II, optic nerve;
III, oculomotor nerve;
IV, trochlear nerve;
V, trigeminal nerve;
VI, abducent nerve;
VII, facial nerve;
VIII, vestibulocochlear nerve;
IX, glossopharyngeal nerve;
X, vagus nerve;
XI, accessory nerve;
XII, hypoglossal nerve;
C1, first cervical spinal nerve.
Name the structures
Dorsal view of the brainstem. 1, Stria habenularis thalami;
2, thalamus;
3, habenular commissure;
4, lateral geniculate nucleus;
5, medial geniculate nucleus;
6, rostral colliculus;
7, commissure of caudal colliculus;
8, caudal colliculus;
9, crossing of trochlear nerve fibers in rostral medullary velum;
10, middle cerebellar peduncle;
11, caudal cerebellar peduncle; 12, rostral cerebellar peduncle; 13, dorsal cochlear nucleus in acoustic stria;
14, median sulcus in fourth ventricle;
15, lateral cuneate nucleus;
16, fasciculus cuneatus;
17, nucleus gracilis;
18, spinal tract of trigeminal nerve;
19, superficial arcuate fibers; 20, left ventral cochlear nucleus;
21, brachium of caudal colliculus;
22, optic tract;
23, brachium of rostral colliculus;
24, cut internal capsule between cerebral hemisphere and brainstem;
25, pineal body;
26, stria terminalis;
II, optic nerves;
IV, trochlear nerve;
V, trigeminal nerve;
VIII, vestibulocochlear nerve.
Rostral cerebellar peduncle (location, function)
- the most medial on each side
- efferents to the brainstem and cerebrum
Middle cerebellar peduncle (location, function)
- most lateral on each side
- afferents (corticopontine) from cerebrum to cerebellum
Caudal cerebellar peduncle (location, function)
- between the rostral and caudal peduncle
- afferents (spino- and vestibulocerebellar)
Main parts of the cerebellum (3)
Vermis
Hemispheres (2)
Flocculonodular lobe
Name the lobules of the vermis
lingula
central
culmen
declive
folium
tuber
pyramis
uvula
nodulus
Which cerebellar lobules are divided by the primary fissure?
culmen and declive
Name the 3 nuclei of the cerebellum
Fastigial
Interpositial
Lateral
F.I.L.
What struture connects the cerebral hemispheres to the brainstem?
capsula interna
How is the attachment of the infundibulum of the hypophysis to the hypothalamus called?
Tuber cinereum
(image: 23 - infundibulum, 8 - tuber cinereum)
Which structure demarcates the caudal extent of the hypothalamus on the ventral surface of the brain?
The mammilary bodies (image 10)
Which 3 structures form the epithalamus?
stria habenularis
habenular nuclei
pineal body (unpaired)
Two important structures of the metathalamus?
Lateral geniculate nucleus (visual)
Medial geniculate nucleus (auditory)
Which colliculus of the midbrain connects to which geniculate nucleus?
lateral geniculate nucl. -> rostral colliculus (vision)
medial geniculate nucl. -> caudal colliculus (auditory)
Which ventricle surrounds the interthalamic adhesion?
the third ventricle
Name the structures
Diencephalon and cerebral hemispheres. The white matter is stained with iron hematoxylin and appears black in the photograph. 1, Corona radiate; 2, corpus callosum; 3, lateral ventricle; 4, crus of fornix; 5, internal capsule; 6, stria habenularis; 7, third ventricle; 8, thalamus; 9, interthalamic adhesion; 10, lentiform nucleus; 11, lateral rhinal sulcus; 12, optic tract; 13, hypothalamus; 14, amygdala; 15, piriform lobe; 16, cingulate gyrus.
From Evans HE, de Lahunta A. Guide to the Dissection of the Dog. 8th ed. St. Louis: Elsevier; 2017.
What is the crus cerebri and where is it located?
Descending tracts of projection processes that connect portions of the cerebral cortex with brainstem centers and the spinal cord course on the ventral surface of the midbrain. These are grouped together on each side as the crus cerebri. The oculomotor, or third cranial nerve, leaves the midbrain medial to the crus .
Name the structures that form the midbrain:
1) dorsal to mesencephalic aqueduct: corpora quadrigemina - 2 rostral, 2 caudal colliculi
2) mesencephalic aqueduct
3) ventral: cerebral peduncle on each side (from dorsal do ventral: tegmentum /reticular formation/, substantia nigra, crus cerebri)
Which CN exits out of the roof of the 4. ventricle, adjecent to the caudal collicullus?
CN IV (trochlear)
What is the lateral lemniscus?
auditory system axons on the lateral side of the midbrain. It courses rostrodorsally from the level of the cochlear nucleus in the medulla to the caudal colliculus and emerges medial to the middle cerebellar peduncle. Many of these fibers arise from the cochlear nucleus
Which fibers form the pons?
1) Longitudinal fibers (from crus cerebri, caudally projecting into the piramids of medulla)
2) transverse fibers cover the longitudinal ones ventrally (course laterally into the middle cerebellar peduncle)
What is the cerebropontocerebellar pathway?
Many of the axons in the crus cerebri and the longitudinal fibers of the pons and most of those in the transverse fibers of the pons. Synapse occurs in the pontine nuclei that are covered by the transverse fibers, and crossing occurs through the transverse fibers to enter the cerebellum through the contralateral middle cerebellar peduncle. Therefore impulses that arise in the left cerebral hemisphere are projected to the right cerebellar hemisphere and vice versa.
Name the structures with the longitudinal and transverse fibers in the medulla oblongata
1) longitudinal - pyramids (caudal continuation of the fibers from the longitudinal fibers of the pons)
2) transverse - trapezoid body (continue as the vestibulocohlear nerve laterally)
Where is the decussation of the pyramids?
at the level of the emerging hypoglossal nerve axons
Which spinal cord tract is formed by the continuation of the pyramidal axons?
corticospinal tract
Which CN exits the pons?
CN V (ventrally, caudolateral aspect of the transverse fibers)
Which CN exits the midbrain?
CN IV (dorsally)
Which CN exit the medulla oblongata?
CN VI - XII
Name the exit locations of each of the CN from the medulla oblongata:
CN VI, VII, VIII - trapezoid body
CN IX, X - caudal to trapezoid body, rostral to CN XI rootlets
CN XI - a few cranial rootlets emerge from the lateral side of the medulla caudal to cranial nerve X, form the internal branch, and join with the external branch to form the accessory nerve (external branch from spinal cord up to level C7)
CNXII - caudal portion of the pyramid
Name the structures
Cerebellum and myelencephalon. The white matter is stained with iron hematoxylin and appears black in the photograph. 1, Occipital lobe; 2, cerebellar vermis; 3, cerebellar hemisphere; 4, cerebellar nucleus; 5, fourth ventricle; 6, cochlear nuclei and vestibulocochlear nerve; 7, trapezoid body; 8, pyramid; 9, abducent nerve fibers; 10, descending facial nerve fibers; 11, vestibular nuclei; 12, caudal cerebellar peduncle; 13, flocculus; 14, spinal tract of trigeminal nerve.
Name the location of the communication between the ventricular system and the subarachnoid space in the brain:
lateral aperture of the 4. ventricle
Locations of CNS absorption into the venous system
1) arachnoid villi
2) where the spinal nerves leave the vertebral canal thru the foramina
3) along the olfactory and optic nerves
Where is the nucleus gracilis located?
caudal end of the 4. ventricle (proprioception to the pelvic limb)
Where is the lateral cuneate nucleus located?
continuous with the caudal cerebellar peduncle (proprioception to the thoracic limb)
Name the fasciculs on the dorsal aspect of the medulla oblongata from medial to lateral
fasciculus gracillis
fasciculus cuneatus
spinal tract of the CN V
Name the 3 types of white matter fibre types:
1) commisural
2) association
3) projection
Name the 4 commissural pathways
1) rostral: connects the paleopallium (olfactory peduncles and piriform lobes)
2) corpus callosum: connects the neopallium (cerebrum)
3) hippocampal: connects the archepallium
(4) caudal - visual reflexes) - not in de Lahunta
Name the parts of the corpus callosum (3)
genu (rostral)
corpus
splenium (caudal)
What is the septum pellucidum?
a thin vertical sheep of tissue extending between the corpus callosum and the fornix
Which structures form the hippocampal formation (3)
hippocampus
dentate gyrus
subiculum
Name the parts of the fornix (hippocampus)
from caudal to rostral:
crura, body, columns
Name the structures
Medial surface of right cerebral hemisphere and lateral surface of brainstem.
1, Ectogenual sulcus;
2, genual sulcus and gyrus;
3, genu of corpus callosum;
4, cingulate gyrus;
5, callosal sulcus;
6, cruciate sulcus;
7, body of corpus callosum;
8, ramus of splenial sulcus;
9, splenium of corpus callosum; 10, splenial sulcus and gyrus; 11, caudal horizontal ramus of splenial sulcus;
12, suprasplenial sulcus;
13, occipital gyrus;
14, cut internal capsule between cerebral hemisphere and brainstem;
15, optic tract at lateral geniculate nucleus;
16, rostral colliculus;
17, medial geniculate nucleus; 18, caudal colliculus;
19, arbor vitae cerebelli;
20, rostral cerebellar peduncle; 21, caudal cerebellar peduncle; 22, middle cerebellar peduncle; 23, fasciculus cuneatus;
24, spinal tract of trigeminal nerve;
25, lateral cuneate nucleus;
26, superficial arcuate fibers; 27, cochlear nuclei;
28, trapezoid body;
29, lateral lemniscus;
30, transverse fibers of pons; 31, brachium of caudal colliculus;
32, transverse crural tract;
33, crus cerebri;
34, left optic tract;
35, optic chiasm;
36, rostral commissure;
37, paraterminal gyrus;
38, septum pellucidum; 39, frontal gyrus; II, optic nerve; III, oculomotor nerve; IV, trochlear nerve.
Name the structures
(B) Lateral view of a brain with the left half removed except for most of the left rhinencephalon.
1, Right olfactory bulb;
2, rostral part of the rostral commissure;
3, precommissural fornix;
4, telencephalic septum;
5, medial surface of right cerebral hemisphere;
6, corpus callosum;
7, dorsal commissure of fornix;
8, alveus of hippocampus;
9, fimbria of hippocampus; 10, interthalamic adhesion; 11, column of fornix;
12, piriform lobe (from dorsal side);
13, rostral commissure;
14, caudal part of rostral commissure;
15, left olfactory bulb;
16, cerebellar medulla.
Which nucleus forms part of the wall of the lateral ventricles?
caudate nucleus
What are the anatomical parts of the caudate nuclei?
head, body, tail (tail terminates in the amygdaloid body in the piriform lobe)
Name the 2 components of the lentiform nucleus
globus pallidus (medial)
putamen (lateral)
Name the structures
Telencephalon. The white matter is stained with iron hematoxylin and appears black in the photograph.
1, Corona radiate;
2, cingulate gyrus;
3, corpus callosum;
4, lateral ventricle;
5, caudate nucleus;
6, internal capsule;
7, body of fornix;
8, interventricular foramen;
9, third ventricle;
10, lentiform nucleus;
11, rostral commissure;
12, optic nerve;
13, lateral olfactory tract.
Name the structures
Medial view of a right cerebral hemisphere with medial structures removed to show the lateral ventricle. The rostral horn of the ventricle is bounded laterally by the caudate nucleus (see 2). The distal part of the temporal horn is bounded laterally by the amygdala (see 8); elsewhere, the ventricle is bounded by white matter.
1, Olfactory bulb;
2, caudate nucleus;
3, genu of corpus callosum;
4, body of corpus callosum;
5, splenium of corpus callosum; 6, splenial sulcus;
7, internal capsule;
8, amygdaloid body;
9, piriform lobe;
10, stria terminalis;
11, rostral commissure.
Name the structures:
Lateral view of the brain, internal capsule exposed.
1, Olfactory bulbs;
2, left cerebral hemisphere;
3, internal capsule (lateral view); 4, crus cerebri;
5, acoustic radiation;
6, medial geniculate nucleus;
7, rostral colliculus;
8, brachium of caudal colliculus; 9, caudal colliculus;
10, lateral lemniscus;
11, cerebellum—arbor vitae;
12, location of dorsal nucleus of trapezoid body;
13, location of olivary nucleus; 14, pyramid;
15, trapezoid body;
16, transverse fibers of pons;
17, pyramidal and corticopontine tracts (longitudinal fibers of pons);
18, transverse crural tract;
19, piriform lobe;
20, optic tract (cut to show internal capsule);
21, optic chiasm; II, optic nerve; III, oculomotor nerve.
Name the structures
*
Name of nerve 1?: radial n.
*
Name of tract 2 (spinal cord)?: fasciculus cuneatus
*
Name of tract 3 (brainstem)?: medial lemniscus
*
Name of nucleus A?: nucleus cuneatus
*
Name of nucleus B?: thalamic
*
Name of pathway termination C?: somatosensory cortex
Vertebral formula dog/cat
C: 7
T: 13
L: 7
S: 3
C: 20+
Vertebral formula horse
C: 7
T: 18
L: 6
S: 5
C: 20
Vertebral formula bovine
C: 7
T: 13
L: 6
S: 5
C: 20
Vertebral formula swine
C: 7
T: 14-15
L: 6-7
S: 4
C: 20-23
Where do the first spinal nerves exit the vertebral canal?
lateral vertebral foramen of the dorsal arch of atlas
Where do the spinal nerves of segments C3-7 leave the vertebral canal?
IV foramina cranial to the vertebra of the same number
Where does the spinal nerve of C8 leave the vertebral canal?
IV foramen caudal to the C7 vertebral body
Where do the spinal nerves of SCS T1-S3 leave the vertebral canal?
IV foramina caudal to the vertebra of the same number
Which vertebral body holds the spinal cord segments L4-6 in the dog/cat?
the L4 vertebral body
Which vertebral body holds the SCS S1-3 in dogs/cats?
the L5 vertebral body
Which vertebral body holds the SCS Cd1-5 in dogs/cats?
the L6 vertebral body
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Which colour represents the cell bodies of GSE neurons innervating the axial, and which the appendicular muscles?
The GSE neurons innervating the axial muscles populate the medial portion of the horn. Those innervating the appendicular muscles are located laterally and cause the lateral bulge of the ventral gray horn that is evident at the cervical and lumbar intumescences
GSE neurons that innervate proximal limb muscles are located in the ventral portion of the lateral part of the ventral gray horn. Those innervating the more distal limb muscles are in the dorsal portion.
What is a nerve?
A nerve consists of a collection of axons in the PNS myelinated by Schwann cells and encased in various layers of connective tissue: the endoneurium, perineurium, and epineurium. No nerves exist in the CNS. All nerves are components of the PNS, so the word peripheral nerve is redundant.
Vertebral formula of domestic animals
Which vertebral body houses the end of the spinal cord in domestic animals and humans?
Where is the cell body of the first (preganglionic) neuron of the GVE (autonomic system) and where is the cell body of the ganglionic (postganglionic) one?
1) grey matter of the CNS
2) ganglion of PNS
Where is the sympathetic system located?
referred to as the thoracolumbar system, based on the location of the cell body of the preganglionic neuron (first neuron), which is in the lateral gray column from spinal cord segments T1 to about L4 or L5. As a general rule, the sympathetic ganglia are located fairly close to the CNS, and the ganglionic axons are fairly long.
Main neurotransmitter of the sympathetic system?
noradrenaline
Where is the parasympathetic system located?
referred to as the craniosacral system because the cell bodies of the preganglionic neurons are located either in the brainstem nuclei of cranial nerves III, VII, IX, and X or in the sacral spinal cord segments. As a general rule, the ganglia of this parasympathetic system are located in or fairly close to the effector organ, and the ganglionic axons are short.
Main neurotransmitter of the parasympathetic system?
acetylcholine
How is the UMN traditionally divided?
Pyramidal (cell bodies of neurons in the motor are of the cerebral cortex) - axons descend thru corticospinal pathway thru the pyramids -impotant in primates
Extrapyramidal - neurons originate in the cerebral cortex and descend into the brainstem directly or via basal nuclei. Axons then course from specific brainstem nuclei to ste SC without traversing the pyramids of the medulla (important in domestic animals)
Which animals have developed pyramidal systems and what does it relate to?
Primates and raccons
considerable manipulative ability in their thoracic limb digits.
What is an important contribution of the pyramidal system in the horse?
To the facial nuclei which have GSE-LMNs that innervate the lips - which suggests that these muscles of prehension perform the most highly skilled activity in this species.
What are Betz cells?
Many of these pyramidal system cell bodies are large and are referred to as giant pyramidal cells or Betz cells - located in the lamina V of the cerebral cortex and gyri that comprise the motor area
Most important “motor” gyri in carnivores
postcruciate and suoprasylvian
Name the cell layers of the cerebral cortex
Neopallium usually has 6 layers
Paleoplallium fewer layers (olfactory cortex)
Where are the neuronal cell bodies of the extrapyramidal system located?
Scattered in nuclei all over the brain, but only ones from the mesencephalon and rhombencephalon have axons that descend to the spinal cord to influence the LMNs
Name the extrapyramidal basal nuclei
Caudate nucleus
Putamen
Pallidum
Claustrum
Nucleus accumbens
Putamen + pallidum = lentiform nucleus
Corpus striatum = all of the nuclei + parts of the internal and external capsules related to them
Which talamic nucleus serves as a projection nucleus for the extrapyramidal system?
The ventral rostral thalamic nucleus
Where is the red nucleus located?
tegmentum at the level of the rostral colliculi -> axons from there decussate immediately and course caudally as the rubrispinal tract
What kind of effect on the muscles do the red nucleus neurons have?
predominantly facilitatory to motor neurons of flexor muscles and therefore function in the initiation of protraction of the limbs in gait generation (thru the components of the cervical and lumbar central pattern generators)
What is the reticular formation?
a collection of neuronal cell bodies of various sizes and a plethora of processes that form an ill-defined meshwork in the central core of the brainstem, extending from the caudal brainstem till the caudal diencephalon
What is the role (in gait formation) of the pontine reticulospinal tract?
a facilitatory influence on spinal cord GSE neurons that innervate extensor muscles by way of a reticulospinal trac
Where is the olivary nucleus located and where do most of its axons project to?
Medulla oblongata, ventral and caudal to the facial motor nucleus.
Its efferent axons project primarily to the contralateral portion of the cerebellum.
Three main functions of the UMN system
(1) initiate voluntary activity of the motor system,
(2) maintain muscle tone to support the body’s weight against gravity and to establish the posture on which the voluntary activity can be performed,
(3) control the muscular activity associated with the visceral functions: respiratory, cardiovascular, and excretory.
Two phases of gait?
(1) a postural phase and
(2) a protraction (swing) phase.
What are the central pattern generators?
The central pattern generator is the network of interconnected interneurons in the spinal cord gray matter that modulates motor neuron activity for the generation of gait. These interneurons function between the UMN and the GSE-LMN and between the spinal nerve afferents and the GSE-LMN. The role of the UMN in this gait generation is mediated through the central pattern generator. The central pattern generators located in the spinal cord intumescences are the ones most involved with gait generation.
Which SC tracts are responsible for the postural phase of the gait which depends on the activation of antigravity extensor muscles and the inhibition of the flexor muscles?
Pontine reticulospinal tract
(pontine reticular formation)
Vestibulospinal tracts (vestibular nuclei)
The initiation of protraction requires the activation of flexor muscles and the inhibition of extensor muscles to elevate the limb from the ground. Which SC tracts are important here?
Rubrospinal tract (red nucleus)
Medullary reticulospinal tracts (medulary retricular formation)
Lesions of which brain structures will produce clinically relevant gait and muscle tone abnormalities?
Pontine and medullary reticular formation
What are the circumventricular organs and name them
Unique structures characterised by abundant capillaries and lack of BBB, anatomically positioned near the ventricles.
These sites are believed to be involved in such functions as chemoreception, neurosecretion, and the control of various visceral activities. They play important roles in the communication between the parenchyma and cerebrospinal fluid and in communication with other organs via bloodborne products.
(1) Area postrema (vomiting) near the 4th ventricle
(2) the subfornical organ on the caudal surface of the columns of the fornix, where they form the rostral border of the third ventricle;
(3) the subcommissural organ that projects ventrally into the rostral mesencephalic aqueduct ventral to the caudal commissure;
(4) the pineal gland that projects caudally from the dorsal portion of the third ventricle;
(5) the hypothalamic vascular organ adjacent to the ventral portion of the third ventricle.
Where are the cell bodies of the neuroepithelial cells of the taste buds located?
- geniculate ganglion of CN VII
- distal ganglia of the glossopharyngeal and vagal nerves
Distribution of the SVA nerve fibers in the taste buds in different regions of the oral cavity/tongue?
1) palate and rostra 2/3 of the toungue -> facial SVA
2) caudal 1/3 of the tongue and rostral pharynx -> glossopharyngeal SVA
3) caudal pharynx and larynx -> vagal SVA
Structures that form the limbic system?
Telencephalon
A. Inner cortical ring
1. Amygdaloid body
2. Hippocampus
3. Fimbria-fornix: septal area hypothalamus, mamillary bodies
B. Outer cortical ring
1. Cingulate gyrus and cingulum
2. Septal area
3. Medial forebrain bundle, hypothalamus
4. Brainstem general visceral efferent, lower motor neuron
Diencephalon
A. Thalamus
1. Rostral thalamic nucleus
B. Epithalamus
1. Habenular nucleus
2. Stria habenularis thalamus
3. Habenular intercrural tract
C. Hypothalamus
1. Mamillary bodies
a. Mamillothalamic tract
b. Mamillotegmental tract, reticular formation
Mesencephalon
A. Intercrural nucleus, reticular formation
Name the basal nuclei that function in the extrapyramidal and limbic system
1) extrapyramidal system: caudate nucleus, pallidum, and putamen
2) limbic system: the amygdaloid body and septal nuclei
What is the cyngulum?
a long association tract consisting of longitudinal axons in the white matter (corona radiata) of the cingulate gyrus.
These axons course from the parahippocampal gyrus, located caudally, to the septal area and frontal lobe gyri located rostrally.
Which brain structure is most important in maintaining the awake/sleep state?
Which nuclei are important?
Reticular formation of the pons and medulla
1) Locus coeruleus (the central gray substance adjacent to the rostral portion of the fourth ventricle) - norepinephrine
2) dorsal raphe nucleus (adjacant to locus coeruleus) - serotonin
Where is the subthalamus located and what is it composed from?
between the thalamus and the substantia nigra of the mesencephalon.
It is composed of the subthalamic body and zona incerta.
What is the metathalamus composed of?
Lateral and medial geniculate nuclei
Which structures are included in the epithalamus?
the habenular nuclei and their connections and the pineal gland.
Name the thalamic nuclei groups
- Rostral thalamic group: rostral thalamic nucleus (limbic system)
- Medial thalamic group: medial dorsal nucleus
- Lateral thalamic group
Dorsal tier:
Dorsolateral nucleus
Caudolateral nucleus
Pulvinar nucleus
Ventral tier:
Ventral rostral nucleus (extrapyramidal)
Ventral lateral nucleus (cerebellum)
Ventral caudal group:
Ventral caudal medial nucleus (cranial nerves)
Ventral caudal lateral nucleus (spinal nerves) - Caudal thalamic group (metathalamus)
Medial geniculate nucleus (auditory, vestibular)
Lateral geniculate nucleus (vision) - Intralaminar (midline) thalamic group:
Central medial nucleus
Paraventricular nucleus
Functional division of the thalamus?
(1) the direct cortical projection system,
(2) the diffuse cortical projection system,
(3) the thalamic reticular system
Functions and nuclei of the direct cortical projection system of the thalamus
Conscious perception pathways for sensory systems and the thalamic relay for motor systems.
- The ventral caudal lateral nucleus receives afferents from spinothalamic tracts (general somatic afferent [GSA], general visceral afferent [GVA]), and the medial lemniscus (general proprioception) and projects efferents to the somesthetic cortex for neck, trunk, and limbs.
- The ventral caudal medial nucleus receives afferents from the quintothalamic tract (GSA, general proprioception) and solitariothalamic tract (GVA, special visceral afferent [SVA]) and projects efferents to the somesthetic cortex for the head region.
- The lateral geniculate nucleus receives afferents from the optic tract and projects efferents to the visual cortex of the occipital lobe.
- The medial geniculate nucleus receives afferents from the brachium of the caudal colliculus (special somatic afferent–auditory and special proprioception) and projects efferents to the temporal lobe.
For the motor systems, a thalamic relay occurs for the extrapyramidal system and the cerebellum in their circuitry to the telencephalon.
1. The ventral rostral nucleus receives afferents from the pallidum and red nucleus and projects efferents to the motor cortex of the frontoparietal lobe.
2. The ventral lateral nucleus receives afferents from the cerebellar nuclei via the rostral cerebellar peduncle and the red nucleus and projects efferents to the motor cortex of the frontoparietal lobes.
What is the reticular formation? What is the ARAS?
a network of neurons in the central portion or core of the brainstem from the medulla through the pons and midbrain and into the diencephalon
ARAS are the neurons of the reticular formation that project rostrally, it unctions to arouse the cerebral cortex, to awaken the brain to a conscious level, and to prepare the cortex to receive the rostrally projecting impulses from any sensory modality. It is responsible for maintaining a state of wakefulness.
Name the extensions of the ventricular system
1) olfactory recesses (extending from the lateral ventricles into the olfactory bulb)
2) infundibular recess (extending
ventrally from the third ventricle into the infundibulum)
3) lateral recesses of the fourth ventricle
4) suprapineal recess dorsally from the third ventricle (which is best detected in sagittal magnetic resonance imaging (MRI) images)
Name all the tracts (Thomson book)
A - spinospinal (propriospinal)
B - fasc. gracillis
C - cuneatus
D - dorsolateral faciculus
E - dorsal spinocerebellar
F - ventral spinocerebellar
G - spinothalamic
H- rubrospinal
I - lat. corticospinal
J - lat. tectotegmentospinal
K - medullary (lat.) reticulospinal
L - Pontine (ventral) reticulospinal
M - Lateral vestibulospinal + spinovestibular
N - tectospinal
O - ventral corticospinal
P - Medial vestibulospinal and medial
longitudinal fasciculus
Identify the basal nuclei (Thomson)
A - caudate
B - pallidum
C - internal capsule
D - putamen
E - external capsule
F - extreme capsule
G - claustrum
Lentiform nucl - putamen + pallidum
Corpus striatum = Caudate nucleus, internal capsule,
lentiform nuclei
Which nerves have the strech and pain receptors for the urinary bladder?
- Stretch receptors are innervated by afferent axons that travel through the pelvic nerve toward the sacral spinal cord segments.
- Pain receptors are innervated by afferent axons that travel in both the pelvic and hypogastric nerves, but primarily in the hypogastric nerves.
Dewey and Da Costa
Which part of the brainstem houses the micturition center?
principally located in the reticular formation of the pons, and to a lesser degree in the midbrain and medulla.
- Two distinct regions of the pons have been demonstrated to be involved in the filling and evacuation phases of the detrusor reflex, respectively.
- The dorsolateral region contains two groups of neurons involved in the micturition reflex: a medial cell group (M region) and a lateral cell group (L region).
1) Neurons of the M region (Barrington’s nucleus) project excitatory axons to the parasympathetic (muscarinic cholinergic) motor neurons in the sacral spinal cord that give rise to the pelvicnerves. Axonal processes from M region neurons also innervate inhibitory interneurons (GABA-ergic) that synapse on nicotinic cholinergic motor neurons in the sacral spinal cord that give rise to the pudendal nerves. Activation of neurons of the M region facilitates urinary bladder evacuation.
2) Axons projecting from the L region neurons have excitatory synaptic connections with nicotinic cholinergic sacral motor neurons that give rise to the pudendal nerves. Activation of L region neurons facilitates urinary bladder filling. The brainstem micturition center can be considered the UMN for normal urination.
Afferent and efferent tracts for urination, from and to the brainstem?
- Afferents (strech) thru the spinothalamic tract
- efferents: reticulospinal, tectospinal
