Thalamus and Hypothalamus Flashcards
Where is the thalamus found within the brain?
The middle of the brain just under the posterior half of the corpus callosum + ventral to the lateral ventricles
What separates the 2 halves of the thalamus?
3rd ventricle
Some people have a bridge connecting the 2 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?
Key relay centre to cortical sensory areas
Enhances or restricts signals
What is the only sensory system not represented within the thalamus?
Olfaction
Describe how thalamic nuclei are named.
Named based on their location within the thalamus
Which nuclei connect with the motor cortex (primary, premotor and supplementary)?
Ventral lateral
Ventral anterior
Which nuclei relay sensory information from different parts of the body?
Head: Ventral posteromedial
Below the neck: Ventral posterolateral
To what medial temporal lobe structures do the intralaminar nuclei project too?
Amygdala (emotions, fear, anxiety)
Hippocampus (memory)
Basal ganglia (motor initiation/ movement)
Describe the main type of neurones found in the intralaminar nucleus
Glutamatergic
excitatory
What is loss of neurones in the intralaminar nuclei region associated with?
Progressive supranuclear palsy
Parkinson’s disease
What does the reticular nucleus form?
Outer covering of the thalamus
Describe the main type of neurones found in the reticular nucleus
GABAergic
Inhibitory
What important system are the intralaminar and reticular nuclei a part of?
Ascending Reticular activating system (ARAS)– involved in maintaining consciousness
Describe how the reticular nuclei affect cortical activity.
They have no 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
What is the set of interconnected pathways in the brainstem involved in the reticular activating system?
Reticular formation
Describe the location and structure of the hypothalamus.
Just below the thalamus
Divided in 2 by the 3rd ventricle
Collections of individual nuclei with distinct functions
Largely ipsilateral connections with other nuclei
What are the 4 F’s the hypothalamus is involved in?
Fighting
Fleeing
Feeding
Mating
State 2 forebrain structures that the hypothalamus has very close connections with
Olfactory system
Limbic system
List 4 structures of the limbic system.
Hippocampus
Amygdala
Cingulate Cortex
Septal Nuclei
How is the hypothalamus involved in maintaining homeostasis?
It coordinates these different mechanisms to maintain homeostasis:
Autonomic nervous system
Endocrine system
Behaviour
Which nucleus is involved in the circadian rhythm?
Suprachiasmatic 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 does the diencephalon consist of?
Thalamus
Hypothalamus
Subthalamic nucleus
What is a collection of cell bodies called in the CNS + PNS? What is the exception to this?
CNS: Nuclei
PNS: Ganglia
Exception: Basal ganglia in CNS
How do reticula nuclei differ to other thalamic nuclei?
They don’t connect with distal regions
They connect with other thalamic nuclei
Where does the reticular nucleus receive inputs from?
Collaterals of axons from other thalamic nuclei
Therefore, acts to modulate thalamic activity (negative feedback)
Where does the Paraventricular nucleus send projections to?
Autonomic nervous system (Vasculature, Heart, Kidney)
Posterior pituitary gland (Vasopressin and Oxytocin)
What does the suprachiasmatic nucleus control?
Sleep-wake cycles
has connections to Pineal gland which secretes melatonin
What may a lesion in the paraventricular nucleus cause?
Loss of inhibitory neurones
Hyperphagia + weight gain
What may a lesion in the suprachiasmatic nucleus cause?
A disrupted sleep cycle
