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Y2 - NMH > Thalamus and Hypothalamus > Flashcards

Thalamus and Hypothalamus Flashcards

1
Q

Constituent parts of the diencephalon?

A

Thalamus + Hypothalamus + Subthalamus

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2
Q

Describe the anatomical location of the thalamus

A
  • Sits just inferior to the posterior half of the corpus callosum
  • Sits ventral to the lateral ventricles
  • Sits lateral to the 3rd ventricle on either side (divided in 2 by the 3rd ventricle)
  • There may be a vestigeal connection connecting each side of the thalamus, but not in most people
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3
Q

Describe the anatomical location of the hypothalamus, in relation to the thalamus and otherwise

A
  • Hypothalamus is just inferior to the thalamus and superior to the midbrain and infundibulum (pituitary stalk)
  • Anterior and posterior borders include the anterior commisure and the mammilary bodies respectively
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4
Q

How does the thalamus organise itself..

1) In relation fo the forebrain?
2) Functionally?

A

1) Ipsilateral connections with the forebrain - the part of the thalamus on RHS will connect with the RHS forebrain
2) Discrete nuclei with separate functions

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5
Q

1) General function principles of the thalamus (i.e. what does it do overall, basically)?
2) Thalamic functions in regards to the sensory system, and one exception?

A

1)

  • Relay centre between the cerebral cortex and the rest of the CNS
  • Integration and modification of information as it goes through the thalamus

2)

  • Key relay centre to cortical sensory areas
  • Enhances / restricts signals
  • Exception: olfaction / olfactory function not represented
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6
Q

What are the 4 classifications of thalamic nuclei?

A
  • SARI
    1. SPECIFIC
  • Connected to primary cortical areas
    2. ASSOCIATION
  • Connected to association cortex
    3. RETICULAR
  • Not connected to cortex
    4. INTRALAMINAR
  • Connected to ALL cortical areas
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7
Q

Function of the following thalamic nuclei…

1) Lateral Geniculate?
2) Medial Geniculate?

A

1)

  • Relay information from the retina to the primary visual cortex

2)

  • Relay information from the inner ear to the primary auditory cortex
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8
Q

Which 2 thalamic nuclei relay sensory information (in regards vibration, proprioception and touch, not like hearing or visual) - somatosensory function, and from which parts of the body?

A

1)

  • Ventral posterolateral - somatosensory (body)

2)

  • Ventral posteromedial - somatosensory (head)
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9
Q

Which 2 thalamic nuclei relay motor information, and what do they relay with in order to fulfill this function?

A
  • Ventral lateral + ventral anterior
  • Relay information with:
  • Primary motor cortex
  • Premotor cortex (association cortex)
  • Supplementary cortex (association cortex)
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10
Q

Outline the somatosensory pathway step-wise, beginning with initial detection of the stimulus

A
  1. Vibration, proprioception and touch are detected by receptors - stimulates neurone
  2. Transmission along neurone that travels via dorsal root ganglion along into dorsal column tract of the spine - this is the primary sensory neurone
  3. The primary sensory neurone terminates at either the gracile or cuneate nuclei at the level of the medulla. The sensory decussation is also at this level, and decussation also occurs past here
  4. Secondary sensory neurone synapses with primary sensory neurones at the gracile / cuneate nuclei
  5. Secondary sensory neurone travels up, then terminates at the thalamus, where dependent on the source of the initial stimulation (body or head), either the ventral posterolateral or ventral posteromedial nuclei respectively relays this sensory information to the primary somatosensory cortex
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11
Q

What are association cortices?

A

Parts of the cortex which are not primary cortical areas which aid the function of these primary cortical areas

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12
Q

What are the 3 thalamic divisions of the association cortices and describe what / where they are?

A
  1. Prefrontal cortex - most of the frontal lobe except for the primary motor cortex and some other motor cortical areas
  2. Parieto-tempero-occipital cortex - consists of all of the cortex in the parietal, temporal and occipital lobes except for the primary cortical areas
  3. Cingulate cortex - follows the line of the corpus callosum (can be viewed when looking at the medial surface of the cerebral hemisphere)
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13
Q

Which thalamic nuclei function to relay information with the following association cortices?

1) Cingulate + prefrontal
2) Parieto-temporo-occipital + prefrontal

A

1)

  • Anterior
  • Lateral dorsal
  • Dorsomedial

2)

  • Lateral posterior
  • Pulvinar
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14
Q

Which 2 types of nuclei are involved in the reticular activating system (RAS)?

A
  1. Intralaminar
  2. Reticular
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15
Q

What are intralaminar thalamic nuclei - i.e. the general principle?

A

A classification of thalamic nuclei that connect to all cortical areas - diffuse cortical projections

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16
Q

1) Where do intralaminar nuclei project to especially?
2) What type of neurones are these that project through these areas, mostly?
3) Loss of neurones in this region is associated with which diseases - 2 examples?

A

1)

  • Various medial temporal lobe structures
  • Amygdala - emotions, fear, anxiety
  • Hippocampus - memory
  • Basal ganglia - movement

2)

  • Glutamatergic neurones (i.e. excitatory)

3)

  1. Progressive supranuclear palsy
  2. Parkinson’s disease
17
Q

1) Where does reticular thalamic nucleus connect to?
2) How do they receive their input?
3) What type of neurons are in the reticular nucleus?
4) What is the function of the reticular nucleus?
5) Where is the reticular nucleus found?

A

1)

  • Intrathalamic projections - connect with other thalamic nuclei

2)

  • Recieve their inputs from collaterals of their axons from thalamic nuclei

3)

  • GABAergic - inhibitory

4)

  • Modulates thalamic activity (negative feedback)

5)

  • Forms the outer covering of the thalamus
18
Q

What is the reticular formation?

A

Set of interconnected pathways in the brainstem which send ascending projections to forebrain nuclei - thalamic nuclei

19
Q

Describe the ARAS (ascending reticular activating system) to bring about wakefulness and arousal

A
  1. Activation of reticular formation - reticular formation projects to the thalamic nuclei
  2. Activation of intralaminar nuclei - which projects to cortical areas
  3. Intralaminar nuclei activate cortex to modulate wakefulness and arousal via their cortical projections
  • Therefore the greater the activation through the reticular formation, the greater the wakefulness and arousal
  • Also, reticular fomation synapses with the reticular nuclei which in turn modulates the thalamic ouput including the the intralaminar cortical projections therefore there is an indirect pathway by this mechanism
20
Q

Describe the ARAS (ascending reticular activating system) to reduce wakefulness and arousal

A
  1. Activation of reticular formation - reticular formation projects to the reticular nucleus
  2. Activation of reticular nucleus - which projects to other thalamic nuclei and are inhibitory (GABAergic)
  3. Therefore inhibition of intralaminar nuclei so less stimulation of cortices so less wakefulness and arousal
21
Q

How does the hypothalamus organise itself..

1) In relation fo the forebrain?
2) Functionally?

A

1) Largely ipsilateral connections with the forebrain - the part of the hypothalamus on RHS will connect with the RHS forebrain
2) Discrete nuclei with separate functions

22
Q

What are the 4 F’s that the hypothalamus are involved in?

A
  1. Fighting
  2. Fleeing
  3. Feeding
  4. Mating (f**king)
23
Q

3 homeostatic functions and connections of the hypothalamus?

A
  1. ANS connections
  2. Endocrine connections - e.g. hypothalamic-pituitary axis
  3. Behaviour - e.g. feeding
24
Q

List behaviours the hypothalamus is involved in

A
  1. Fighting and fleeing - limbic
  2. Feeding
  3. Sexual behaviour (f**king)
  4. Emotion
  5. Circadian rhythm
  6. Memory
25
Q

Where is the PVN (paraventricular nucleus) of the hypothalamus located?

A

Just inferior to the 3rd ventricle

26
Q

What 2 things does the PVN (paraventricular nucleus) of the hypothalamus project to, what type of neurones do these connections and how do they function?

A
  1. ANS - parvocellular neurones project down to the IML (intermediolateral) horn of the spinal cord and the preganglionic sympathetic neurones. From there it affects SNS function in 3 ways: causes vasoconstriction, positive chronotropic and inotropric effect on the heart, and kidney blood flow and output interference
  2. Posterior pituitary gland - magnocellular neurones project to here and stimulate release of VP and oxytocin
27
Q

What behaviour is the PVN of the hypothalamus involved in?

A

Feeding behaviour

28
Q

Where is the SCN (suprachiasmatic nucleus) of the hypothalamus located?

A

Just superior and posterior to the optic chiasma

29
Q

Describe the physiological process behind how the SCN is involved in wakefulness - getting tired

A
  1. Blue light hits retina
  2. Retina-hypothalamic connection and transmission
  3. SCN activation
  4. Transmission down via spinal cord
  5. Reaches pineal gland
  6. Promotes melatonin release by pineal gland
  7. TIRED
30
Q

What will lesion in the SCN cause and give one other associated pathology with SCN defect

A
  • Disrupted sleep cycle
  • Schizophrenia
31
Q

Outline TBI and the subsequent neuroinflammation and how this is visible

A
  • TBI (traumatic brain injury) → shear → severed connection → widespread diffuse axonal injury
  • Results in microglial inflammation which can be seen on the PET scans
32
Q

Give 2 ways that hypothalamic damage can occur and some symptoms that can occur as a result of it

A
  • Craniopharyngiomas
  • Chronic inflammatory conditions

Symptoms:

  • AP deficiencies
  • Diabetes Insipidus
  • Labile emotions / aggression - prefrontal cortex / ventromedial nucleus
  • Inappropriate sexual behaviour
  • Memory lapses - SCN mammilary bodies
  • Temperature regulation - preoptic area
  • Hyperphagia - infundibular and PVN damage

Y2 - NMH (12 decks)

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