The thalamus and Internal Capsule

what are the adult derivatives of the embryologic prosencephalon

telencephalon and diencephalon

overview of the diencephalon

• large mass of gray matter deeply situated in the brain

• essentially the center of the brain

what separates the right and left side of the diencephalon

the 3rd ventricle

4 parts of the diencephalon 

• hypothalamus

• epithalamus

• subthalamus

• thalamus 

• Hint: think all things thalamus 

hypothalamus location relative to thalamus

inferior to anterior portion of thalamus

hypothalamus location relative to pituitary gland 

superior 

hypothalamus location relative to midbrain

anterior

hypothalamus location relative to optic chiasm

posterior

major features of hypothalamus

hypothalamic nuclei, mamillary bodies, and infundibular stalk 

what is the only part of the diencephalon that can be seen on an intact brain 

hypothalamus 

what is the major control center of the autonomic nervous system

hypothalamus

epithalamus location

posterior to the thalamus

primary structures of the epithalamus

pineal gland, habelunar nuclei

pineal glad def

midline, unpaired endocrine gland, but also partof the nervous system 

neural inputs in pineal gland

midline, unpaired endocrine gland, but also part of the nervous system 

neural outputs of pineal gland 

no known neural outputs, only hormonal 

sleep-wake cycles in pineal gland 

displays a cricadian rhythm to light with respect to its release of hormones (i.e. melatonin) 

3 results of tumor in pineal gland 

1. hydrocephalus due to compression of cerebral aqueduct

2. deficits in eye movementdue to compression of midbrain where oculomotor ond trochlear CN nuclei are located 

3. Changes in sexual development 

habenula purpose

assings reward value to stimuli or how much a person enjoyed a stimulus 

what does lack of habenular activity result in 

depression 

subthalamus location

• inferior to the thalamus

• lateral to the hypothalamus

• medial to the midbrain 

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pineal gland

what is the subthalamus an extension of

midbrain tegmentum

subthalamus function

part of neural circuit that helps control movement

what is the largest component of the diencephalon

the thalamus

thalamus composition

egg-shaped collection of nuclei

thalamus location

inferior to the body of the lateral ventricles; esentially the center of the cerebrum 

thalamus structure

composed of a variety of thalamic nuclei divided into three major regions which are separated by the y-shaped internal medullary lamina 

what do the anterior and medial regions of the thalamus deal with

memory and emotions

what does the lateral region of the thalamus deal with

sensory and motor functions

Ventral posterolateral nucleus function

relay sensory information from the body to cortex

VPL damage

lose of sensation of contralateral side of body 

ventral posteromedial nucleus (VPM) 

relays sensory information from the head to the cortex 

VPM damage 

loss of sensation on contralateral side of head 

lateral geniculate nucleus (LGN) function

relays visual information

LGN damage

cortical blindness

Medial geniculate nucleus (MGN) function

relays auditory information

MGN damage

cortical deafness of hyper/hypo sensitivity to sound

2 main functions of thalamus

relay and decide info

relay function of thalamus 

gateway for information going to the cortex 

thalamus receives input from

the cortex, brainstem, limbic system, basal nuclie, cerebellum, and all sensory systems except the olfactory system

spam blocker role of thalamus

it decides which information is sent to the cortex for further processing 

thalamic inputs

axons bringing information into the thalamus

specific thalamus inputs

(minority): those conveying information that a given thatlmic nucleus may pass on accurately to the cortex 

regulatory thalamus inputs 

(majority): those that contribute to decsions aobut the form in which information leaves a given thalamic nucleus 

how are thalamic nuclie grouped

into categories based on inputs and outputs

relay thalamic nuclei

receive specific inputs and project to particular functional areas of cortex

assoication thalamic nuclei 

project to association areas of cortex (namely the prefrontal cortex and the parietal-occipital-temporal association area) and are important in the distribution and gating of info between cortical areas 

what type of neurons are thalamic neurons

projection neurons

stroke and thalamus

• thalamic damage occurs most often as a result of a stroke

• due to the important fucntions of the thalamus, small lesions can produce large, debilitating symptoms

thalamic pain results from

a stroke

what is thalamic syndrome 

lesion to thalamus that results in alteration of sensory perception 

3 main symptoms of thalamic syndrome 

• thalamic pain

• hemianesthesia

• sensory ataxia 

thalamic pain

painful burning sesnation of affected body/head parts 

hemianesthesia

loss of sensation on one side of the body

sensory ataxia

loss of proprioception leads to uncoordinated movements 

sensory processing disorder

• some persons hypersensitive to sensations from environment

• others cannot receive adequate sensory stimulation from environment

• atypical fucntion of the thalamus

capsule def 

bundle of axons in the CNS 

location of internal capsule

lateral to the thalamus

what fibers are in the internal capsule 

compact bundle of axons (white matter) 

what do fibers in the internal capsule connect 

cortex and subcortical structures 

corona radiata 

internal capsule fibers fan out into the corona radiata just superior to the internal capsule