Thalamus and Hypothalamus Flashcards
What structures make up the diencephalon?
- Thalamus
- Subthalamus - what is that?
- Hypothalamus
Where is the thalamus found within the brain - saggital?
- In the middle of the brain
- Just under the posterior half of the corpus callosum
Where is the thalamus found within the brain - coronal?
- Sits ventral to the lateral ventricles
- Divided into two by the 3rd ventricle
- Organised into discrete (separate) nuclei
NOTE: In neuroanatomy, nuclei are clusters of neurons (groups of cell bodies) with a similar functions and connections
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?
- Relay site for numerous inputs and outputs within the CNS
- Relays signals to cortical areas
- Key relay centre to sensory cortical areas
- Involved in almost all sensory systems
- EXCEPT olfactory
- Involved in almost all sensory systems
- Modulates signals - enhances or restricts signals
NOTE: Main in bold
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 RETICULAR – not connected to the cortex
Which nuclei connect with the motor cortex (primary, premotorand 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 and Parieto-tempero-occipital Cortex
What important system are the intralaminar and reticular nuclei a part of?
Reticular activating system – 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 and is involved in the reticular activating system?
Reticular formation
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 Endocrine system Behaviour
State some forebrain structures that the hypothalamus has very close connections with
Olfactory system Limbic system
List some structures of the limbic system.
Hippocampus Amygdala Cingulate Cortex Septal Nuclei
What does the behavioural control exerted by the hypothalamus include?
Eating and drinking Expression of emotion Sexual behaviour Circadian rhythm Memory
Which nucleus is involved in the circadian rhythm?
Subrachiasmatic nucleus
How is our behaviour directed towards homeostatic goals?
There is a pleasure centre within the limbic system, which, whenever you’ve achieved homeostasis (e.g. eating food when you’re hungry), the activity of the pleasure centre increases
What are the presenting symptoms of hypothalamic tumour?
Polydipsia Polyuria Absent menses
What are some later symptoms of hypothalamic tumour?
Labile emotions, rage Inappropriate sexual behaviour Memory lapses Temperature fluctuation Thyroid, adrenal cortex and gonadal function decreases Hyperphagia
