THE THALAMUS AND HYPOTHALAMUS 1. The thalamus is the largest component of the diencephalon. The function of the thalamus is to integrate sensory and motor activities. The divisions of the thalamus include anterior medial lateral interlaminar and reticular Right! No. All foils are correct. There is also a metathalamus and posterior thalamus. 2. The internal medullary lamina separates medial from lateral groups of nuclei splits to enclose the medial nuclear group splits to enclose the anterior and intralaminar nuclear groups connects thalamic nuclei with cerebral cortex Right! No. The first and third foils are correct. The internal medullary lamina interconnects one nuclear group within the thalamus with another group. 3. The anterior nuclear group of the thalamus is concerned with emotional behavior is part of the limbic system has connections with the mammillary body receives fibers from the lateral spinothalamic tract Right! No. The first three foils are correct. The anterior nuclear group connects with the mammillary body via the mammillothalamic tract. 4. The dorsomedial nucleus (part of the medial nuclear group) is connected with parietal cortex is a relay station in the motor system is concerned with affective behavior is connected with the hippocampus Very good! No. The first and third foils are correct. The dorsomedial nucleus forms reciprocal connections with the prefrontal cortex and hypothalamus. 5. The lateral nuclear group of the thalamus is divided into dorsal and ventral subgroups. The dorsal subgroup of the lateral nuclear group has input largely from other thalamic nuclei receives direct input from long ascending tracts (lateral spinothalamic, medial lemniscus) includes the pulvinar project mainly to primary sensory areas of cortex Right! No. The first and third foils are correct. The dorsal subgroup does not receive direct input from the long ascending tracts but rather, has most input from other thalamic nuclei. The output is to association areas of cortex. The pulvinar has interconnections with the medial and lateral geniculate bodies and association areas of cortex. Note: Some authors include the pulvinar in the dorsal tier of the lateral nuclear group. Others consider the pulvinar a separate subgroup. 6. The ventral subgroup of the lateral nuclear group receive direct input from some long ascending fiber tracts contains the ventral anterior nucleus contains the ventral lateral nucleus is only a sensory relay station Right!. No. The first three foils are correct. Major output of the ventral anterior nucleus is to the motor and premotor cortex. The ventral lateral nucleus is also involved in motor integration. 7. The ventral posterior nucleus belongs to the ventral subgroup of the lateral nuclear group. This nucleus receives sensory modalities from the contralateral half of the body and face receives spinothalamic tract fibers receives the medial lemniscus projects to the primary sensory cortex in the postcentral gyrus Right! No. All foils are correct. The ventral posterior nucleus is actually made up of a medial and lateral part. The lateral part (ventral posterior lateral nucleus) receives medial lemniscus and spinothalamic tracts (position vibratory, touch discrimination, and pain and temperature). The medial part receives facial sensation and taste. 8. The ventral lateral nucleus of the thalamus is the major relay for fibers originating in the limbic system basal ganglia medulla cerebellum spinal cord Very good! No, the answer is D. The ventral lateral nucleus links the cerebellum, basal ganglia and cerebral cortex and is the primary relay for cerebellar fibers. The ventral anterior nucleus is the main relay for basal ganglia input. 9. The intralaminar nuclei of the thalamus has only a few direct cortical projections is involved in the awareness of painful sensory experience receives only sensory fiber input plays a role in cortical arousal responses Right! No. The second and fourth foils are correct! The interlaminar and reticular nuclei receive sensory and motor fibers and project diffusely to cerebral cortex. 10. The metathalamus is composed of the medial and lateral geniculate nuclei (or bodies). The medial geniculate nucleus receives visual fibers from the retina auditory fibers from the inferior colliculus visual feedback fibers from the occipital lobe auditory feedback fibers from the primary auditory cortex in temporal lobe. Very good! No. The second and fourth foils are correct. The input from the inferior colliculus is via the brachium of the inferior colliculus. The outflow is via the auditory radiation in the internal capsule to the primary auditory cortex in the temporal lobe. 11. The lateral geniculate nucleus (body) is a relay nucleus in the visual system. The lateral geniculate nucleus receives fibers from ganglion cells in the retina via the optic nerve and tract receives feedback fibers from the temporal lobe projects to the occipital lobe via optic radiation in the internal capsule is a diffuse, non-laminated nucleus Very good! No. The first and third foils are correct. The output of the lateral geniculate nucleus is to the visual cortex in the occipital lobe. The lateral geniculate is a highly structured, laminated nucleus. 12. The sensory modalities perceived by the thalamus are permanently destroyed with ablation of the sensory cortex include an aching, burning pain include sharp, pricking, well localized pain are those types carried by the small, non-myelinated C-fibers Right! No. The second and fourth foils are correct. The aching, burning pain carried by the C-fibers is believed to terminate in the thalamus. 13. The area (s) of thalamus most involved with emotional behavior medial thalamus ventral posterior nuclei anterior thalamic nuclei ventral lateral nucleus Right! No. The first and third foils are correct. The ventral posterior nucleus is in the sensory pathway with output to the primary sensory cortex. The ventral lateral nucleus is involved with motor integration. The anterior thalamic nuclei make connections with the cingulate gyrus and is considered part of the limbic system. The dorsomedial nucleus of the medial nuclei is connected with prefrontal cortex and hypothalamus and is involved with behavioral responses. 14. The thalamic syndrome which follows a vascular lesion to the thalamus includes immediate loss of all sensations ipsilateral to the lesion early loss, then return of pain, temperature and crude touch lowered threshold for pain perception exaggerated and unpleasant sensations, when ellicited, on contralateral side of the body Right! No. The second and fourth foils are correct! The sensory loss is contralateral since sensory fibers have crossed by the time they reach the thalamus. After a thalamic lesion the threshold for sensation is increased (harder to produce) and is usually unpleasant. 15. Subthalamic nucleus is a sensory relay nucleus can be considered a rostral extension of the midbrain substantia nigra has a major input from the cortex damage may produce hemiballismus-involuntary flinging movements of contralateral musculature Very good! No. The second and fourth foils are correct! The subthalamic nucleus is involved with motor integration with major connections between globus pallildus and substantia nigra. 16. The hypothalamus is in the ventral part of the diencephalon. A groove in the wall of the third ventricle, hypothalamic sulcus, separates the thalamus (ventrally). It is continuous with the midbrain posteriorly. The fornix passes through the hypothalamus and divides it into medial and lateral regions. The medial division of the hypothalamus contain nuclei separated into groups, they are preoptic suprachiasmatic (supraoptic) tuberal mammillary Right! No. Allfoils are correct. 17. The suprachiasmatic (or supraoptic) region of the hypothalamus contains three nuclei; supraoptic, paraventricular and anterior nucleus. Supraoptic nucleus is located just above the optic tract project axons to the anterior lobe of the pituitary project axons which transport and store neurosecretory material elaborates oxytocin as a neurosecretory product Very good! No. The first and third foils are correct. The supraoptic nucleus produces antidiuretic hormone (ADH) which is stored in axonal swellings in the posterior lobe of the pituitary (neural lobe). 18. A lesion of the supraoptic nucleus or posterior lobe of the pituitary causes high specific gravity urine excessive water intake (polydipsia) increased absorption of water at the distal convoluted tubules of the kidney increased urinary excretion (polyuria) Very good! No. The second and fourth foils are correct. The polyuria and polydipsia following supraoptic and pituitary lesions, as well as hypophysectomy for other causes, is called diabetes insipidus. ADH output is controlled by the osmolarity of the blood that bathes the supraoptic nucleus. The early name for ADH was vasopression, which is still used occasionally. 19. The paraventricular nucleus of the hypothalamus projects fibers to the posterior (neural) hypophysis has axons that produce ADH elaborates oxytocin absence of oxytocin causes diabetes insipidus Very good! No. The first and third foils are correct. The paraventricular nuclei project axons that elaborate oxytocin and store it in the posterior (neural hypophysis). Oxytocin contracts uterine muscle. It is used in obstetrics to induce labor. 20. The tuberal region of the hypothalamus is divided into medial and lateral regions by the fornix. Bilateral lesions in the ventromedial nucleus in animals produce loss of appetite obesity excessive intake of water savage behavior Right! No. The second and fourth foils are correct. The ventromedial nucleus appears associated with satiety and the lateral hypothalamus with feeding. A lesion of the ventromedial nucleus results in a voracious appetite. Thirst is associated with the anterior hypothalamus in the suprachiasmatic (supraoptic) region. 21. The mammillary region contains the mammillary nuclei (bodies) and posterior hypothalamic nuclei. Major input to the mammillary bodies include fornix mammillothalamic fibers medial forebrain bundle trigeminal lemniscus Right! No. The first three foils are correct. The fornix is the major input to the mammillary bodies. The fornix originates in the hippocampus and follows a "c" shaped course to the mammillary bodies. Some fibers from the septa area join the fornix and enter the mammillary bodies.The medial forebrain bundle brings afferent fibers from the premotor cortex. The medial forebrain bundle brings afferent fibers from the premotor cortex. The efferent connections are mammillo- thalamic tract to the anterior nucleus of the thalamus and mammillotegmental tract to midbrain reticular nuclei. 22. The posterior hypothalamic nucleus is dorsal to the mammillary bodies. Efferent connections of the posterior and lateral hypothalamic nuclei are the main fibers projecting from hypothalamus to brain stem. These fibers descend by way of mammillothalamic tract paraventricular fiber system medial longitudinal fasciculus dorsal longitudinal fasciculus Right! No. The second and fourth foils are correct. The dorsal longitudinal fasciculus is located in the periaqueductal gray and the fibers project to autonomic and motor nuclei in the brain stem. 23. Trophic factors produced in the hypothalamus affect the production of hormones in the anterior lobe of the pituitary. These trophic factors are released into capillaries in the mammillary bodies median eminence suprachiasmatic region preoptic region Right! No, the answer is B. These trophic factors reach the anterior pituitary by way of the hypophyseal portal circulation. The trophic factors act on anterior pituitary cells to release or inhibit release of pituitary hormones such as adrenocortico- trophic (ACTH), thyroid stimulating hormone (TSH), luteinizing hormone (LH),growth hormone (GH). 24. The hypothalamus controls brain stem autonomic output. This control occurs via median forebrain bundle mammillotegmental tract fornix dorsal longitudinal fasciculus Very good! No. The second and fourth foils are correct. Note: These are the two major efferent descending pathways from the hypothalamus. The fibers of the dorsal longitudinal fasciculus mostly originate in the paraventricular nucleus; some end in the dorsal nucleus of the vagus and other fibers continue into the spinal cord (intermediolateral cell column and sacral autonomic nucleus). The mammillotegmental fasciculus are collateral branches of the fibers of the mammillo- thalamic fasciculus that turn caudally and terminate in the reticular formation (raphe nuclei) of the midbrain and pons. Impulses originating in the mammillary body reach autonomic nuclei in the brain stem and spinal cord through synaptic relays in the reticular formation. In general, the rostral hypothalamus appears concerned with parasympathetic control and caudal hypothalamus with sympathetic control. 25. When the temperature of blood increases , sweating and vasodilatation are triggered by the posterior hypothalamus mammillary bodies anterior hypothalamus lateral region of hypothalamus Right! No, the answer is C. The posterior region of the hypothalamus is sensitive to lowered body temperature and triggers the onset of shivering and vasoconstriction. 26. Lesions in the lateral hypothalamus abolish thirst hyperphagia (excessive feeding) excessive thirst-overhydration hyperthermia Very good! No, the answer is A. Hyperphagia occurs with lesions in the ventromedial nucleus. Hyperthermia occurs with anterior hypothalamic lesions and excessive thirst occurs with stimulation of the lateral hypothalamus.