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 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
RETICULAR –not connected to the cortex only other thalamic nuceli
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
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
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- parts of brain it regulates?
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
Loss of neurones in intralaminar nuclei can lead to what
Parkinson’s
Progressive supranuclear palsy
Where are reticular nucleus?
Outer covering of the thalamus
Chemical property of reticular nuclei
Mainly GAGAergic so inhibitory
Role of reticular nuclei
Relieve collaterals of other thalamic nuclei axons and have negative feedback effect
What is the reticular formation?
A set of interconnected pathways in the brain stem which have ascending projections to forebrain nuclei
Name of ascending reticular formation projections to forebrain
Ascending Reticular activating system
Role of reticular formation
Involved in conciousness and arousal
Levels wakefulness directly proportional to ARAS activity
What nuclei receive inputs from ARAS
Intralaminar and reticular
What is the hypothalamus made up of?
Large collection of individual nuclei with distinct functions
4fs function of hypothalamus
Fighting
Fleeing
Feeding
Mating
What does hypothalamus have direct connections with
ANS
Where are neurones found with direct projections to pre-autonomic neurones?
Paraventricular nuclei at the top of 3rd ventricle in wing shaped part
Where do paraventricular nucleus neurones project
Parvocellular nuclei to spinal chord for ANS
Magnocellular nuclei to PPG for vasopressin and oxytocin release
What else can have impact on feeding behaviour in PVN?
Many other hypothalamic nuclei
Role of suprachiasmaticc nuclei
Role in circadian rhythms so sleep wake cycles according to environmental light
Role of melatonin
Hormone regulating sleep wake cycles
Released by pineal gland
Pathway for melatonin release
Light enters eye and detected by melanopsin expressing retinal ganglion cells-> suprachiasmatic nuclei -> PVN-> interomediolateral column-> superior cervical ganglion-> pineal gland
Chemical properties of intralaminar neuclei
Mainly glutamergic
Function of lateral hypothalmaic nuclei
Promotes sleep
Function of preoptic nuclei
Promotes wakefulness
Basal ganglia function
Movement
Hippocampus role
Memory
Amygdala functions
Emotions
Where is hippocampus?
Floor of ventricle in temporal lobe
Where is the amygdala?
Anterior part of temporal lobe
Where do intralaminar nuclei project to?
Mainly medial temporal lobe structures -Hippocampus and amygdala
