The Diencephalon

midline nuclear complex

-A thin layer of cells cover the medial surface of the thalamus and fuse in the interthalmic adhesion. -It is thought that this nuclear complex receives information from the brainstem reticular formation and is important in visceral function

parasympathetic response

-Although there tends to be overlap hypothalamic sites associated with the parasympathetic responses tend to be located anteriorly. -The Parasympathetic system tends in general to enhance energy storage. -Activation of parasympathetic nerves causes: decreased cardiac output and blood pressure; increased peristalsis in salivation and the gut; pupil and bladder constriction

input and output to the hypothalamus

1) Interconnections with the prefrontal areas of the brain especially with the limbic system convey information relevant to the role of the hypothalamus in mediating many of the autonomic and somatic aspects of affective states. 2) Interconnections with various viscera and somatic sensory nuclei, sensory of the brainstem and the spinal cord.

intralaminar nuclei

A complex of nuclei in the core of the internal medullary lamina. This system modulates the excitability and overall function of the cortex and the basal ganglia related to both sensory and to cognitive function. Remember that one of the primary loops from the BG is to these structures. The intralaminar nuclei can evoke cortical responses from the frontal, parietal, cingulate and orbital areas of the association cortices.

sympathetic response

Hypothalamic sites associated with the sympathetic responses tend to be located posteriorly. Activation of sympathetic system: increases heart rate; decreases peristalsis and diverts blood from the gut to the skeletal muscle; dilates pupils.

functional properties of the hypothalamus

In most cases, fragments of behavior patterns elicited by stimulating a hypothalamic location can be elicited by stimulating a brainstem site. Thus, hypothalamic sites may function as triggers stimulating neural activity in other parts of the CNS. The hypothalamus is small, so discrete lesions affecting individual functional area of the human hypothalamus are quite rare and have to be bilateral in order to completely disrupt function.

general rule of thumb

Limbic is medial to motor and sensory is inferior to cognitive.

where are the habenular nuclei?

On either side of the base of the stalk that attaches the pineal gland to the diencephalon

hypothalamus

The hypothalamus is located beneath the thalamus and is functionally a part of the autonomic nervous system

nuclear complex that serves as the relay center for specific sensory and motor information

Ventral Tier Sensory-Motor Nucleus

primary thalamic functions

a) Channels sensory information through specific nuclei associated with pain, taste, temperature, audition, and vision to the primary sensory cortex b) Integrates sensory/motor information from the basal ganglia and the cerebellum and then transmits it to the primary and premotor cortex. c) it regulates functions of the associational cortex and mediates speech, language and cognition.

Anteriorly the internal medullary lamina splits to enclose an anterior group of nuclei referred to as a group as the _________

anterior nucleus

sites in the hypothalamus associated with parasympathetic responses are located where?

anteriorly

They hypothalamus is an important junction in pathways associated with:

autonomic, endocrine, emotional, and somatic functions

intrinsic sensory neurons

directly responsive to physical stimuli. example: cells that measure the temp of blood are found in the the hypothalamus

two tiers of the lateral nuclear cortex

dorsal tier, ventral tier

single large nucleus in the medial tier of the thalamus

dorsomedial nucleus

what is the ventral anterior nucleus involved in?

facilitation of skilled movements and initiating voluntary movements

what structure's functions does the subthalamus inhibit?

globus pallidus

tumors/lesions in the thalamus cause what

hemiballism

visible parts of diencephalon on the intact brain

inferior surface of the hypothalamus (mammillary bodies, infundibular stalk with pituitary gland)

"other thalamic structures"

intralaminar nuclei, midline nuclear complex, reticular nucleus

contributions of the pulvinar nucleus

language formulation and processing, lexical properties, reading, writing and other language functions

three nuclei of the dorsal tier "cognitive" thalamus

lateral dorsal nucleus, lateral posterior nucleus, pulvinar... (?)

what is the hypothalamus designed to do?

maintain homeostasis (our internal environment) within an acceptable physiologic range (governing the endocrine system & secretions of the endocrine glands maintenance functions such as: heart rate digestion response to stress body temperature water balance and thirst hunger and satiety reproductive behavior)

three tiers of nuclei in the thalamus

medial, lateral, anterior

what do the intralaminar nuclei do?

modulate the excitability and overall function of the cortex and the basal ganglia related to both sensory and to cognitive function

hemiballism

motor disorder resulting in involuntary, violent, flinging movements that appear while awake but disappear with sleep

blood supply to the hypothalamus

penetrating branches from the Circle of Willis

blood is supplied to the thalamus by the

posterior cerebral artery

sites in the hypothalamus associated with sympathetic responses are located where?

posteriorly

two areas of the ventral posterior nucleus

posterolateral (processing of primitive and distinctive somatosensory sensation from the body), posteriormedial (somatosensory sensation from the face)

involvement of mammillary bodies

processing of recognition memories and are thought to add the element of smell to memory

what is the ventral lateral nucleus involved in?

regulation of volitional movements

what divides the thalamus into medial and lateral groups of nuclei?

the internal medullary lamina

what does the epithalamus include?

the pineal gland & the habenular nucleus

lateral geniculate body

the thalamic relay center for the sensation of vision

The hypothalamus forms the floor and lateral walls of what...

the third ventricle!

what is the lateral dorsal nucleus probably involved in?

visceral-sensory integration

destruction of the limbic thalamus (anterior + medial nuclei) results in...

-lowering the threshold for rage -memory loss in patients with Korsakoff's syndrome

subthalamus

-The subthalamus is ventral to the thalamus and wedged between the thalamus and hypothalamus. It is an important component of the basal ganglia. -Tumors/lesions in this area cause hemiballism, a motor disorder resulting in involuntary, violent, flinging movements that appear while awake but disappear with sleep. -The subthalamus inhibits the functions of the globus pallidus.

reticular nucleus

-This nucleus consist of a thin almost invisible layer of nerve cells located between the external medullary lamina of the thalamus and the internal capsule. -It consists of neurons similar to those in the brainstem reticular formation and probably integrates and regulates thalamic neuronal activity.

role of the pineal body

An endocrine gland that secretes melatonin. Rates of production are highest during darkness, suggesting a role in circadian rhythms and sleep induction. Increasing periods of daylight causes a decrease in melatonin. Melatonin suppresses gonadal function. The effect upon some species with seasonal reproductive cycles is much more pronounced than others.

thalamus

Blood is supplied by the Posterior Cerebral Artery Each nuclei in the thalamus has fibers to specific cortical areas. Every area of the cerebral cortex has a reciprocal relationship with some part of the thalamus. Much of the internal capsule is made up of these cortico-thalamic connections.

role of dorsomedial nucleus

Has numerous connections with other thalamic nuclei and the prefrontal cortex. It is important in emotional and personality development and integrates visceral information with emotions, affect, thought processes and judgment.

role of anterior nucleus

Mediates visceral and emotional information. Electrical stimulation and its ablation induce changes in blood pressure and emotional drives.

the habenular nuclei

Part of the epithalamus. Each nucleus has one major input, the stria medullaris thalami from basal forebrain regions (septum, basal nucleus, lateral preoptic nucleus). The lateral habenular nucleus receives an additional projection from the medial segment of the globus pallidus.

four parts of the diencephalon

subthalamus, epithalamus, hypothalamus, thalamus

medial geniculate center

thalamic relay for audition