Thalamus and Hypothalamus Flashcards
10.10.2019
What is the diencephalon made up of?
Thalamus and Hypothalamus (and subthalamus)
Where is the Thalamus located?
- towards the back of the brain
- near the midline
- just beneath lateral ventricles
- divided in the middle by 3rd ventricle
- above hypothalamus
- associated with midbrain
Which part of the thalamus deals with touch/proprioception?
ventral posterior lateral nucleus
What are the functions of the Thalamus?
- Relay centre of the brain
- involved in almost all sensory systems (except olfactory)
- enhances or restricts signals
What are the functions of the hypothalamus?
- Collection of individual nuclei with distinct functions
- largely ipsilateral connections with other nuclei
- involved in 4Fs (fighting, fleeing, feeding, mating)
- direct connections with the ANS
- connections with the endocrine system (hypothalamic pituitary axis)
- control of behaviour (e.g. feeding behaviour)
In neuroanatomy, what are nuclei?
Clusters of neurons with a similar functions and connections.
Where does the thalamus lie in relation to the ventricles?
- Sits ventral to the lateral ventricles
- Thalamus divided in two by 3rd ventricle
Intralaminar nuclei
- Project to various medial temporal lobe structures (e.g. amygdala, hippocampus and basal ganglia)
- mostly glutamatergic neurones (excitatory)
- Loss of neurones in this region associated with progressive supranuclear palsy* and Parkinson’s disease
What is the amygdala responsible for?
fear, anxiety, emotions
What is the hippocampus responsible for?
Memories
What are the basal ganglia responsible for?
Movement
Progressive supranuclear palsy
PSP
-> rare brain disorder causing problems with walking and balance
Reticular Nucleus
- forms outer covering of the thalamus
- majority of neurones are GABAergic (inhibitory)
- don’t connect with distal regions, but with other thalamic nuclei (unlike other thalamic nuclei)
- Receive inputs from collaterals of their axons from thalamic nuclei
- acts to modulate thalamic activity (negative feedback)
Reticular formation
- Set of interconnected peathways in the brainstem,
- send ascending projections to forebrain nuclei (ARAS)
- involved in consciousness and arousal
- Both intralaminar and reticular nucleus receive inputs from ARAS
What is the ARAS responsible for?
ascending reticular activating system
-> concousness and arousal
degree of wakefulness depends on the level of ARAS activity
Hypothalamus and ANS
Neurons in hypothalamic paraventricular nucleus with direct projections to pre-autonomic neurons in spinal cord
-> hypothalamus has direct connections with the ANS
Paraventricular nucleus in the hypothalamus function
- Sends projections to autonomic nervous system and posterior pituitary gland
- also involved in feeding behavior
What is the function of the suprachiasmatic nucleus?
- responsible for controlling the circadian rhythm
- tiny region of the brain in the hypothalamus, located right above the options chasm
- lesions of SCN cause sleep disruptions
Name the association nuclei of the thalamus
- lateral dorsal nucleus
- dorsomedial nucleus
- posterior lateral nucleus and the pulvinar (belong to a single nuclear complex)
Which sensory system is the thalamus not involved in?
Olfactory
What part of the thalamus is important in the somatosensory pathway?
ventral posterior lateral nucleus
What is the function of the intralaminar nuclei?
Project to various medial temporal lobe structures (e.g. amygdala, hippocampus and basal ganglia + reticular formation)
Can be regarded as a rostral continuation of the reticular formation of the midbrain. Project widely into the cerebral cortex.
Play a role in the function and regulation of the basal ganglia, arousal, cognitive functions, and relaying of nociceptive information to the cerebral cortex.
- Amygdala = emotions, fear, anxiety
- Hippocampus = memory
- Basal ganglia = movement
- reticular formation: arousal
Mostly glutamatergic neurons (i.e. excitatory)
Loss of neurons in this region associated with progressive supranuclear palsy* and Parkinson’s disease
PSP
progressive supra nuclear palsy
-> rare brain disorder causing problems with walking and balance.
Summarise the relationship between intralaminar nuclei, reticular nucleus and the reticular formation
- The Intralaminar nuclei receive inputs from the Reticular Formation of the brainstem and project diffusely to all cortical areas.
- The reticular nucleus also receives inputs from the reticular formation but projects to the other thalamic nuclei only, regulating the flow of information through these to the cortex.
- Thus the reticular formation, intralaminar and reticular nuclei form the Reticular Activating System, which controls the level of arousal of the brain by modulating the level of activity of the cerebral cortex.
Where is the hypothalamus?
- below the thalamus
- divided into 2 by the 3rd ventricle
- collection of individual nuclei with distinct functions
- largely ipsilateral connections with other nuclei
- involved in the 4 Fs (fighting, fleeing, feeding and mating)
Hypothalamus and the endocrine system
Connections with endocrine systems
E.g. hypothalamic-pituitary axis
Hypothalamus and control of behaviour
- e.g. feeding behaviour (Paraventricular nucleus)
Where are the different components of RAS located?
- reticular formation is in the brainstem
- intralaminar and intralaminar nuclei are in the thalamus
