Thalamus and Hypothalamus Flashcards
Where is the thalamus found within the brain?
It is right in the middle the brain just under the posterior half of the corpus callosum and lateral ventricles
What separates the two halves of the thalamus?
3rd ventricle
Some people have a bridge connecting the two halves
Describe the connections of the thalamus with the forebrain.
Each half of the thalamus has ipsilateral connections with the forebrain
What is the main function of the thalamus?
It is a relay centre between the cerebral cortex and the rest of the CNS
What is the only function that is not represented within the thalamus?
Olfaction
Describe how thalamic nuclei are named.
They are named based on their location within the thalamus
What is the classification of thalamic nuclei based on and what are the four different classes?
The classification is based on the connections of the thalamic nuclei with the cortex
SPECIFIC – connected to primary cortical areas
ASSOCIATION – connected to association cortex
INTRALAMINAR – connected to ALL cortical areas (mostly glutamatergic nuclei) Loss of neurones here causes progressive nuclear palsy
RETICULAR –not connected to the cortex (mostly GABA-ergic nuclei) Project to other thalamic nuclei
Which nuclei connect with the motor cortex (primary, premotor and supplementary)?
Ventral lateral
Ventral anterior
Which nuclei relay sensory information from different parts of the body?
Head – Ventral posteromedial
Below the neck – Ventral posterolateral
Which nucleus is connected to the primary visual cortex?
Lateral geniculate nucleus
Which nucleus is connected to the primary auditory cortex?
Medial geniculate nucleus
The association cortex can be divided into three areas based on thalamic function. What are these three areas?
Prefrontal Cortex
Parieto-tempero-occipital Cortex
Cingulate Cortex
What do the anterior, lateral dorsal and dorsomedial nuclei connect with?
Prefrontal and Cingulate Cortex
What do the lateral posterior and pulvinar nucleus connect with?
Prefrontal
Parieto-tempero-occipital Cortex
What important system are the intralaminar and reticular nuclei a part of?
Reticular activating system (RAS) – involved in maintaining consciousness
Describe how the reticular nuclei affect cortical activity.
The reticular nuclei don’t have any direct connections with the cortex, but they do have widespread intrathalamic connections with all other thalamic nuclei, so it can influence the flow of information from the othernuclei to the cortex
What is the core of grey matter that runs through the brainstem involved in the reticular activating system?
Reticular formation (Reticular formation + Intralaminar nuclei + Reticular nuclei = RAS)
How do the intralaminar nuclei modulate the activity of the cortex?
The reticular formation projects up to the thalamus to the intralaminar nuclei and the intralaminar nuclei, because of their diffuse cortical projections, can modulate the activity of the cortex
What is thalamic syndrome?
Syndrome that develops after thalamic stroke
The symptoms depend on which part of the thalamus has been affected
What three main changes occur in thalamic syndrome?
CHANGE IN SENSATION – reduced, exaggerated, altered
PAIN – central, non-localised (not easily treated because normal analgesics have no effect – may need to use opioids or anti-convulsants/anti-depressants)
EMOTIONAL DISTURBANCE – the nuclei that transmit information to and from the association cortex are associated with the limbic system
Describe the location and structure of the hypothalamus.
The hypothalamus is just below the thalamus and is divided by the 3rd ventricle
It also has ipsilateral connections with the forebrain
How is the hypothalamus involved in maintaining homeostasis?
It coordinates these different mechanisms to maintain homeostasis:
Autonomic nervous system
Behaviour
Endocrine system
What does the behavioural control exerted by the hypothalamus include?
Eating and drinking Expression of emotion Sexual behaviour Circadian rhythm Memory
State some forebrain structures that the hypothalamus has very close connections with.
Olfactory system
Limbic system
