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
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 the thalamus is not involved in?
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 RETICULAR –not connected to the cortex
What important system are the intralaminar and reticular nuclei connected to?
Ascending Reticular activating system – involved in maintaining WAKEFULNESS (not awareness)
someone can be awake but not aware of his surroundings ie vegetative state
ARAS is part of reticular formation which is located throughout the brainstem. Reticular formation has connections to thalamus
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 other nuclei to the cortex ie regulatory role
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 eg feeding
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
4 Fs of life
Fighting, fleeing, feeding, fucking
Which nucleus is involved in the circadian rhythm?
Suprachiasmatic nucleus- above optic chiasm. it is part of the hypothalamus
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
Functions of hypothalamus?
- Regulate ANS: Direct connections with autonomic nervous system, neurons from paraventricular nucleus of hypothalamus can go all the way down to the spinal cord to synapse with a preganglionic neuron that then leaves the spinal cord
2.Connection with endocrine system
3. Control of behaviour ie 4 F’s of life
Fighting
Fleeing
Feeding
Fucking
Which nucleus in hypothalamus can send projections to endocrine and ANS systems ?
paraventricular nucleus (has MAGNOCELLULAR and PARVOCELLULAR neurons) - involved in feeding behaviour slide 27
