Download MCB 163: Mammalian Neuroanatomy

MCB 163: Mammalian Neuroanatomy
Name __Key_______________________
Fall 2005 Seat #______
LAB EXAMINATION THREE
1. MEDIAL GENICULATE BODY The target of fibers from the inferior colliculus; essential for
normal hearing, including spatial localization of sound; tonotopic organization present in
isofrequency domains; has an aural representation superimposed across the tonotopic map.
2. SUBSTANTIA NIGRA A key structure in the direct striatonigrothalamic pathway for the
initiation of movement; the activation of this pathway disinhibits interneurons in VA-VL
thalamic nuclei, thus exciting premotor/supplementary motor cortex cells that in turn trigger MI
cells to initiate movement by exciting specific groups of muscles; serves analogous roles in eye
movements.
3. RED NUCLEUS A midbrain structure with ascending input to thalamic VA/VL nucleus and
hence to motor cortex through its parvocellular subdivision to permit upper motoneurons to have
rapid feedback about actual muscle state for ongoing movement; the magnocellular part
contributes to the rubrospinal system, which conveys cerebellar influence to distal flexors.
4. LATERAL GENICULATE BODY Recipient of retinal input from X- and Y-ganglion cells that
terminate, respectively in the parvo- (upper four) or magnocellular (lower two) layers before
projecting to layer IV in area 17; parvo- system is chromatic, foveal, with small receptive fields,
magno- is achromatic, extrafoveal, with large receptive fields.
5. MEDIAL LEMNISCUS Second order axons arising from gracile and cuneate nucleus neurons
and projecting in somatotopic order to the contralateral ventrobasal complex, where they
terminate with the feet laterally, the back dorsally, and the forelimb ventromedially; these fibers
are joined by main sensory nucleus of V fibers for conscious touch for the ipsilateral face to form
the first complete representation of the body.
6. VENTROBASAL COMPLEX The thalamic representation of somatic sensation receives dorsal
column (body) and trigeminothalamic (head) representation of the cutaneous (corpuscular and
receptors for touch) and muscle (Ia, Ib) senses at the conscious level; is the first center with a
complete representation of the contralateral body.
7. AMYGDALA A limbic structure and a part of Papez’s circuit, which activates the hypothalamus
and limbic cortex to control behaviors related to territoriality, aggression, and reproduction and
to integrate these with the appropriate memories for consequences (stored in the hippocampus)
prior to their execution by the hypothalamus.
8. CAUDOPUTAMEN The hub for cortical input to the basal nuclei, the interneurons and
projection cells here have a complex role in motor planning and ongoing movement; there is no
topographic map of the body or the muscles, and many cells discharge after rather than before
movement; severely damaged in Parkinsonism.
9. CINGULATE CORTEX A critical part of Papez’ circuit involved in the analysis of sensory
events in the limbic system, this structure is now known to play a key role in limbic
representation of pain, pleasure, and reinforcing or aversive consequences of behavior, with
widespread projections o subcortical sensory nuclei.
10. CORPUS CALLOSUM Fibers that interconnect the two cerebral hemispheres and which arise
mainly from cortical layer III. The connections are sufficiently powerful to allow for the
propagation of epileptic seizures in one hemisphere to homotopic points in the contralateral
cortex. Important for coordinating bilateral and symmetrical movements. Significant parts of
1
neocortex (fovea, face, hands, and feet) have sparse or no commissural connections to allow for
independence of use.
11. ANTERIOR THALAMIC NUCLEI These nuclei are related to the limbic system and receive
projections from the amygdala, and in turn project to the frontal lobes and especially the lateral
prefrontal cortex. This circuit appears to be important for modulating emotionality and for
socially acceptable behavior. Severing these fibers in prefrontal leucotomy could provide relief
from otherwise devastating anxiety.
12. THALAMIC RETICULAR NUCLEUS A nucleus of GABAergic neurons which project to the
lateral and medial geniculate bodies and the ventrobasal complex; the searchlight hypothesis
proposes that the cortex directs attention by suppressing thalamocortical transmission via TRN in
modalities that are irrelevant, thus enhancing information flow in the preferred modality.
13. PARAVENTRICULAR HYPOTHALAMIC NUCLEUS A pair of nuclei containing dark-staining
groups of neurons that reside on the dorsolateral hypothalamus. They are the principal source for
a multitude of hormones and releasing factors which specifically influence the posterior pituitary
(neurohypophysis) . Two of the principal influences are from magnocellular vasopressinsecreting neurons which influence vasoconstriction (and thereby help to control water use and
loss) and the resorption of water by the kidney. In contrast, oxytocin influences uterine
contractions (in parturition) and the milk ejection reflexes in nursing behavior.
14. LATERAL HYPOTHALAMIC AREA Concerned with feeding behavior, this region inhibits te
satiety center of the ventromedial hypothalamus to initiate food ingestion; damage has the
opposite effect of stimulation; has extensive reciprocal connections with hypothalamus for the
finer control of feeding.
15. SEPTAL NUCLEI A target of hippocampal projections, these rostral limbic nuclei reciprocate
the latter projection; they are involved in the control of response inhibition (septally-damaged
animals cannot check behaviorally inappropriate response) and in fluid ingestion.
16. SUPRACHIASMATIC NUCLEUS A target of retinal collateral axonal input this tiny center has a
critical role in the establishment and maintenance of circadian and ultradian rhythms that depend
on seasonal and light-dependent input to coordinate their operations; especially important in
migratory birds and may be involved in seasonal affective disorders.
17. ANTERIOR COMMISSURE The route by which olfactory and basal telencephalic commissural
projections between the orbital and amygdaloid cortex reaches the contralateral hemisphere;
especially well-developed in macrosmatic species and in genera such as marsupials that are
acallosal.
18. SI Six-layered neocortex which has multiple representations of the body map including
separate subregions for cutaneous and deep muscle receptors (areas 3a, 3b) and which is
essential for epicritic discrimination of fine touch from the contralateral body (via dorsal
columns) and head (via trigeminal) inputs.
19. SUPERIOR COLLICULUS The optic tectum in nonmammalian vertebrates, this structure
consists of three layers: the dorsal third receives retinal input from Y- and W-ganglion cells, the
intermediate part is polysensory, and the deep one-third is the source of the tectospinal tract;
important in visual reflexes and following moving objects; maps are aligned vertically.
20. INFERIOR COLLICULUS A key midbrain structure integrating monaural and binaural auditory
information, also involved in spatial orienting reflexes and to the localization of auditory objects
in space. As a target of the lateral lemniscus, lesions result in complete contralateral deafness
and partial ipsilateral hearing loss.
2