23. Cortex, Thalamus and Hypothalamus (HT) Flashcards
What foetal structure is the hypothalamus derived from?
Diencephalon
How does the hypothalamus relate to the ventricular system?
Forms floor and ventral walls of 3rd ventricle.
Draw the position of the hypothalamus in the brain.
What are the main parts of the hypothalamus?
- Anterior -> Divided into the chiasmatic and tuberal
- Posterior
What are the main nuclei of the hypothalamus that you need to know?
- Suprachiasmatic nucleus
- Anterior hypothalamus
- Posterior hypothalamic area
- Supraoptic/paraventricular nucleus
- Median eminence/arcuate nucleus/paraventricular nucleus
- Ventromedial nucleus
- Lateral hypothalamus
- Mammillary body
EXTRA:
- Dorsomedial nucleus
- Lateral tuberal nucleus
- Medial mammillary nucleus
- Lateral mammillary nucleus
Label the hypothalamic nuclei.
Label the hypothalamic nuclei.
Summarise the physiological functions of the hypothalamus.
- Maintaining internal environment:
- Temperature control
- Reproductive functions
- Biological clock
- Control of blood flow
- Behaviour
- Memory
What are the two ways in which the hypothalamus can carry out its functions?
- Regulation of the autonomic nervous system
- Release of hormones (neuro-endocrine)
What things does the hypothalamus detect and how?
- Blood osmolarity
- Blood nutrient levels
- Blood hormone levels
- Blood temperature
It detects this directly (using neurons that are sensitive to these things) and indirectly (using input from peripheral receptors and other parts of the brain that are sensitive to these factors).
What does the hypothalamus receive input from?
[IMPORTANT]
- Sensory systems
- Retina
- Olfactory system
- Cutaneous receptors
- Visceral receptors
- Higher centres
- Hippocampal formation
- Amygdala
- Orbitofrontal cortex
- Brainstem nuclei
- Locus coeruleus
- Raphe
- Periaqueductal grey
Via what does the hypothalamus receive visceral sensory input?
[IMPORTANT]
Reticular formation and solitary tract
What parts of the brainstem does the hypothalamus receive input from?
[IMPORTANT]
- Raphe nucleus
- Periaqueductal grey
- Locus coerulus
Via what does the hypothalamus receive input from the orbitofrontal cortex?
[IMPORTANT]
Mediodorsal thalamus
What does the hypothalamus output to?
[IMPORTANT]
- Thalamus
- Anterior pituitary (via portal stream)
- Posterior pituitary (just passing through)
- Brainstem parts:
- Amygdala
- Periaqueductal grey
- Others
What are the main large fibre bundles that connect the hypothalamus? Where do they go?
[IMPORTANT]
- Fornix -> From the hippocampus to the mammillary bodies
- Stria terminalis -> From amygdala to the medial thalamus
- Mammillothalamic tract -> From the mammillary bodies to the dorsal tegmental nuclei, the ventral tegmental nuclei, and the anterior thalamic nuclei
- Medial forebrain bundle -> From anterior nuclei to the midbrain, and vice versa
Draw the position of the fornix and describe the function.
Carries information from the hippocampus to the mammillary bodies of the hypothalamus.
(Shown in red)
Draw the position of the stria terminalis and describe the function.
Carries information from amygdala to the hypothalamus, thalamus nucleus accumbens (in forebrain) and septal nuclei of the forebrain.
(Shown in green)
Draw the position of the medial forebrain bundle and describe the function.
Carries information from the anterior nuclei of the hypothalamus to the midbrain, and vice versa.
(Shown in blue)
Draw the position of the mammillothalamic tract and describe the function.
Carries information from the mammillary bodies to the dorsal tegmental nuclei, the ventral tegmental nuclei, and the anterior thalamic nuclei.
(Shown in red)
Label these bundles.
Summarise the functions of each of the hypothalamic nuclei you need to know.
- Suprachiasmatic nucleus (SCN)
- Biological clock
- Anterior hypothalamus
- Thermoregulation and Fever
- Posterior hypothalamic area
- Fear and Aggression
- Supraoptic + Paraventricular nucleus
- Posterior pituitary secretion of oxytocin & ADH
- Median eminence + Arcuate nucleus + Paraventricular nucleus
- Control of appetite
- Metabolic rate
- Anterior pituitary
- Ventromedial nucleus
- Satiety centre
- Lateral hypothalamus
- Hunger centre
- Mammillary body
- Memory
- Circumventricular organs (Organum vasculosum of lamina terminalis (OVLT) + Subfornical organ (SFO))
- Thirst + Osmoreception
What part of the hypothalamus is involved in the biological clock?
Suprachiasmatic nucleus (SCN)
What part of the hypothalamus is involved in thermoregulation?
Anterior hypothalamus
What part of the hypothalamus is involved in fear and aggression?
Posterior hypothalamic area
What part of the hypothalamus is involved in control over the posterior pituitary gland?
Supraoptic and paraventricular nuclei
What part of the hypothalamus is involved in control over appetite, metabolic rate and anterior pituitary?
- Median eminence
- Arcuate nucleus
- Paraventricular nucleus
What part of the hypothalamus is the satiety centre?
Ventromedial nucleus
What part of the hypothalamus is the hunger centre?
Lateral hypothalamus
What part of the hypothalamus is involved in memory?
Mammillary bodies
What part of the hypothalamus is involved in thirst and osmoreception?
Circumventricular organs:
- Organum vasculosum of lamina terminalis (OVLT)
- Subfornical organ (SFO)
Which part of the hypothalamus releases orexin (hypocretin)? Why?
- Lateral hypothalamus
- This makes sense because the LH is the hunger centre and orexin is involved in wakefulness and motivated behaviours (e.g. finding food)
Describe the blood supply to the hypothalamus and pituitary.
- From the internal carotid artery
- There is a capillary plexus in the median eminence
How many layers are there in the cerebral cortex and hippocampus?
- Cerebral cortex = 6
- Hippocampus = 3
Describe the connections of the layers of the cerebral cortex that you need to know.
- Thalamic afferents end on layer 4/granular cells
- Output pyramidal cells in layers 3, 5 and 6.
What are the 3 main classifications of fibres in the cerebral cortex?
- Commisural -> Connecting the two hemispheres
- Association -> Connecting areas within the same hemisphere
- Projection -> Connecting to lower parts of the brain and spinal cord
What are the different thalamic nuclei you need to know and what are their connections?
- Anterior -> Limbic
- Ventral anterior and ventral lateral -> Motor: basal ganglia, cerebellum
- Ventral posterior medial and ventral posterior lateral -> Somatosensory
- Lateral geniculate -> Visual
- Medial geniculate -> Auditory
- Pulvinar -> Visual
What do you need to know about the epithalamus?
- It contains the pineal gland
- This is controlled by postganglionic sympathetic fibres
- It produces melatonin
