5: Thalamus and Hypothalamus Flashcards
What is the diencephalon?
Where is it located?
Diencephalon= Thalamus, Subthalamus and Hypothalamus
Sourrounds 3rd ventricle in middle of brain
What is the thalamus?
Where is is located?
Thalamus = part of the brain (diencephalon)
Located both sides of 3rd ventrcle
Explain the location of the thalamus in regards to the lateral ventricles
It sits ventral to the lateral ventricles
How is the thalamus organised?
How can it be sub-devided?
The thalamus is organised in different discrete Nuclei
–> accumulation of cells bodies with similar function and connections
What are the functions of the thalamus?
Relay centre of the brain
- e.g. for cortical sensory pathways
- –> Involved in all sensory systems (except olfactory)
Can be inhibitory and exitory
Explain the role of the thalamus in the somatosensory pathway
(And explain the whole pathway)
Somatosensory: Conveys vibration, proprioception, touch infromation to brain
- st. order neuron (in dorsal ganglion): sensory information to dorsal column of ipsilateral side
- (Same neuron) travels up to medulla
- 2nd. order neuron crosses over in medulla to contralateral side
- This neuron synapses in Ventral posterior lateral nucleus in thalamus
- 3rd. order neuron to primary somatosensory cortex
In which thalamic nucleus do neurons from the the somatosensory pathway synapse?
In the ventral posterior lateral nucles (VPL)
What is the role of the ventral posterior lateral nucleus in the thalamus?
Synapse point for the Somatosensory pahtway
What is the role of the intralaminar nuclei in the thalamus?
Project to various temporal lobe strucutres
e.g. amygdalla, hippocampus and basal ganglia
–> associated with limbic system and basal ganglia
–> usually excitory (Glutamate)
What is the function of the reticular nucleus in the thalamus?
Like capsule around thalamus (outer layering of thalamus)
–> GABA neurons (inhibitory)
Connect with othe thalamic pathways (and not with other strcutures of the brain) : interregulation of thalamus
Which role do the interalaminar nuclei play in disease?
Loss of neurons in this region associated with progressive supranuclear palsy* and Parkinson’s disease
–> Progressive degenerative diseases
What is the reticular formation?
Interconnected pathways within the brainstm
- particular anatomy of this area is not known
but it has:
- ascending projections to forebrain called
- Ascending reticular activating system (ARAS)
(also has descending fibres giving rise to the reticulspinal tracts)
What is the function of the ascending reticular activating system?
It is the system (ascenging fibres from reticular formation) that makes us concious/aroused
- Degrees of wakefulness depend on ARAS activity (increased activity = increased wakefulness
Explain relationship between intralaminar nuclei, reticular nucleus and reticular formation
•Both intralaminar and reticular nucleus receive inputs from ARAS (brainstem to thalamus input)
Where is the hypothalamus located?
(Green part) –> Forms the walls and floor of 3rd ventricle
How does the hypothalamus look like?
What is the function of the paraventricular nucleus?
Where is is located?
It is part of the hypothalamus
Two type of cells with different functions
- Parvocellular cells (small cells)
- into spinal chord
- out (via autonomic system) to vasculature, heart, kidney etc.
- Magnocellular cells (large cells)
- rather secretors
- secrete VP and Oxytocin in Neurohypophysis
- Also incolved in feeding behaviour
- leasions can cause feeding behavioral disorders
- it recieves information/ input from other cells involved in feeding bahaviour
Where is the Suprachisamatic nucleus located?
In the hypothalamus above the optic chiasm
