Diencephalon Flashcards
Components of diencephalon
- thalamus
- hypothalamus
- subthalamus
- epithalamus
What is the thalamus?
Collection of nuclei and associated laminae
Location of thalamus
Lies in the floor of central portion of lateral ventricles and forms the superior part of the lateral wall of third ventricle
In 70% of the population, the 2 thalami are connected by ____
Interthalamic adhesion
(Transverses third ventricle)
What forms the roof of the third ventricle?
Ependymal lining of 3rd ventricle reflected from one side to the other along stria medullaris thalami
Lateral surface of the 3rd ventricle is covered by the ____
External medullary lamina
Internally, the thalamus is divided by a vertical sheet of white matter called ____
Internal medullary lamina
Functions of thalamus
- receives info about sensation, vision, hearing
- mediates motor info from cerebellum and basal ganglia to the motor cortex
- involved in autonomic maintenance of consciousness
Name the nuclear groups of the thalamus
- anterior
- medial
- ventral anterior
- ventral lateral
- ventral posterior medial
- ventral posterior lateral
- pulvinar
- medial geniculate body
- lateral geniculate body
- Lateral dorsal
- lateral posterior
- reticular
- intralaminar
- midline
Name the ventrolateral nuclei of the thalamus
- lateral dorsal
- lateral posterior
- ventral anterior
- ventral lateral
- ventral posterior medial
- ventral posterior lateral
Anterior nucleus receives ____ information from the _____
Limbic system information from mammillary bodies
(Via mammillothalamic tract)
Anterior nucleus projects to the…
Cingulate gyrus and frontal cortex
Function of anterior nucleus of the thalamus
Memory & emotions
What causes Korsakoff’s psychosis/syndrome?
- Chronic severe alcoholism (thiamine deficiency)
—> lesions typically around the 3rd ventricle, especially medial & anterior thalamic nuclei, mammillary bodies and/or connections between them
What are the symptoms of Korsakoff’s psychosis/syndrome?
- Short term memory loss
- patient attempts to compensate by confabulating (inserting remote past memories, blatantly untrue stories to fill in gaps)
Medial group of nuclei of the thalamus receives information from…
Basal ganglia
Amygdala
Midbrain
Some spinothalamic fibers
Medial group of nuclei of the thalamus project to the ____
Prefrontal lobe
Function of medial group of nuclei of the thalamus
Memory & behaviour
Ablation of medial group of nuclei of the thalamus results in…
Symptoms that parallel those of prefrontal lobotomy (also affected in Korsakoff’s)
Ventral anterior & ventral lateral nuclei of the thalamus receive information from…
Basal ganglia & dentate nucleus
Ventral anterior & ventral lateral nuclei of the thalamus project to…
Motor & premotor cortices
Function of ventral anterior & ventral lateral nuclei of the thalamus
Motor integration & maintenance of consciousness
Stimulation of ventral anterior and ventral lateral nuclei of the thalamus causes…
Increase in Parkinsonian rigidity and tremor
Ablation of ventral anterior & ventral lateral nuclei of the thalamus has been shown to….
Ameliorate Parkinsonian symptoms
All sensation except olfaction reaches consciousness in the ____, is integrated and sent to the sensory cortex
Ventral posterior nucleus of the thalamus
Ventral posterior medial nucleus of the thalamus
All sensory information from the head & face reaches consciousness and is integrated
Ventral posterior lateral nucleus of the thalamus
All sensory info from the body reaches consciousness and is integrated
Lesion of ventral posterior nucleus of the thalamus
Anesthesia (loss of sensation) or thalamic syndrome (hypersensitivity)
medial geniculate body receives information from…
Inferior brachium and therefore from inferior colliculus
Medial geniculate body projects to…
Auditory cortex via auditory radiation
Medial geniculate body is part of the…
Auditory pathway
Lesion of medial geniculate body results in…
Diminished hearing more pronounced contralaterally
Lateral geniculate body receives information from…
Optic tract
Lateral geniculate body projects to…
Visual cortex via optic radiation
Lateral geniculate body is part of the ____
Visual pathway
Lesion of lateral geniculate body results in…
Visual loss (contralateral homonymous hemianopsia)
Lateral dorsal nucleus has reciprocal connection with…
Limbic system areas
Function of lateral dorsal nucleus
Emotional expression
Lateral posterior nucleus has reciprocal connections with…
Sensory association cortex of parietal lobe
Function of lateral posterior nucleus
Integration of sensory information
Pulvinar receives fibers from…
Retina and superior colliculus
Pulvinar projects in the…
Parietal, occipital, & temporal lobes
Functions of pulvinar
Visual reflexes and eye movement
Reticular nucleus has reciprocal connections with…
Thalamus & cortex
Function of reticular nucleus
Modulation of thalamic activity
Intralaminar nuclei includes the ____
Centromedian nucleus
Functions of Centromedian nucleus
Functions as part of Limbic system in maintaining consciousness & alertness and in integrating emotional responses to pain
Midline nuclei form most of the ____
Interthalamic adhesion
Hypothalamus forms the…
Inferior part of lateral wall, and floor of 3rd ventricle
Mammillary bodies and tuber cinereum are part of the ____
Hypothalamus
Hypothalamus is divided by the ____ into…
Columns of Fornix
Anterior, intermediate, posterior zones
Hypothalamus is part of the ____ system
Limbic
Controls autonomic responses and is part of endocrine system
hypothalamic functions
Endocrine control
By formation of releasing & release inhibiting factors that promote production & secretion of hormones by cells of anterior pituitary
hypothalamic functions
Neurosecretion
- occurs via hypothalamohypophyseal tract
- paraventricular nucleus secretes Oxytocin
- supraoptic nucleus secretes ADH
Lesion of supraoptic nucleus causes…
Diabetes insipidus -> polydipsia, polyuria
hypothalamic functions
General autonomic effects
Different regions mediate sympathetic or parasympathetic activity
hypothalamic functions
Temperature regulation
- Anterior zone responds to increases in temperature by causing cutaneous vasodilation & sweating
- posterior zone responds to decreases in temperature by causing cutaneous vasoconstriction & shivering
hypothalamic functions
Blood pressure & osmollarity control
- Regulation of food & water intake
- contains a glucose sensitive satiety centre and a hunger & thirst centre
Lesion of glucose sensitive satiety centre causes ____
Hyperphagia
Lesion of hunger & thirst centre causes ____
Hypophagia
hypothalamic functions
- Endocrine control
- Neurosecretion
- General autonomic effects
- Temperature regulation
- Blood pressure & osmollarity control
- Sexual behaviour & reproduction
- Biological clock
- Emotion, fear, rage, aversion, pleasure, reward
hypothalamic functions
Sexual behaviour & reproduction
Controls gametogenesis, cyclic variations, maturation & maintenance of secondary sexual characteristics by means of controlling gonadotrophin production by anterior pituitary
hypothalamic functions
Biological clocks
Suprachiasmatic nucleus is involved in circadian rhythms & affects fluctuation in body temperature during the 24hrs
hypothalamic functions
emotion, fear, rage, aversion, pleasure, reward
hypothalamus, limbic system & prefrontal cortex match feelings to their appropriate emotional expression
subthalamus location
transition zone between midbrain & thalamus
subthalamus contains the ____
subthalamic nucleus
subthalamic nucleus
functional constituent of basal ganglia
lesion of subthalamus
hemiballismus: uncontrollable, violent torsonal movements
epithalamus is composed of…
habenula
stria medullaris thalami
pineal gland
posterior commissure
habenular commissure
habenula function
olfactory reflexes (limbic system)
stria medullaris thalami connects…
septal area to habenula
posterior commissure connects…
2 superior colliculi
function of posterior commissure
visual reflexes
pineal gland secretes ____
antigonadotropin & melatonin
function of antigonadotropin
inhibits gonadotropic of anterior pituitary
pineal growth results in…
delayed puberty
pineal destruction results in…
precocious puberty
