Neuro 6: Thalamus and hypothalamus Flashcards
List the 3 parts of the diencephalon
Thalamus, hypothalamus and subthalamus
What intersects the thalamus
3rd ventricle
Locate the thalamus
Ventral to the lateral ventricle
Which 2 thalamic neurons associated with the resticular activating system
RETICULAR nucleus (all around the outside of the thalamus)… does not project to cortex, provides negative feedback to the thalamus
and
INTRALAMINAR… projects to all other areas of cortex including medial temporal lobe structures (amygdala, hippocampus and basal ganglia)
State the function of the thalamus
Key relay centre to cortical sensory areas
Involved in almost all sensory systems (not olfactory)
Enhance or restricts signals
Which sense does not travel through the thalamus
Olfactory
The thalamus only enhances signals t/f
F it can restrict too
Which thalamic nucleus is responsible for transmitting fine touch
Ventral posterior lateral nucleus
What are intalaminar nuclei
Give the functions of the areas it projects to
Thalamic nucleus: Project to MEDIAL temporal lobe structures like amygdala, hippocampus and basal ganglia
Amygdala= fear, emotions, anxiety
Hippocampus= memory and learning
Basal ganglia= movement
What type of neurons exist in the intralaminar neuclei
Glutamaterigic
Loss of intralaminar nucleus neurons asociated with parkinsons and supranuclear palsy (=rare brain disorder causing problems with walking and balance)
What nucleus forms the outer covering of the thalamus +
what type of neurons here
Reticular nucleus (thalamic)- doesn’t connect with distal regions, but instead all other thalamic nuclei
GABAergic (compared to glutamatergic in intralaminar)
Function of reticular nucleus
Mostly inhibitory on thalamic nuclei
Where do reticular nuclei receive inputs from
receives sensory information from thalamic neurons via COLLATERALS of their axons
Modulates thalamic activity -ve feedback depending on this input
Where is the reticular formation found and what is it involved in
Area of grey matter in brainstem, set of interconnected pathways
Send ascending projections to forebrain nuclei via ascending reticular activating system (ARAS)
Conscioussness and arousal. Degree of wakefullness dependent on ARAS (increased activity of ARAS –> increased wakefullness)
Intralaminar and reticular nuclei receive input from ARAS
What is ascending reticular activating system
Consciousness and arousal- degrees of wakefullness proportional to activity of ARAS Intralaminar and reticular nucleus receive input from the ARAS
How can the RAS increase activity in the cortex
DIRECT: can increase stimulation of intralaminar nuclei, so this directly increases activity of cortical areas
INDIRECT: can cause the reticular nucleus to increase activity of thalamic nuclei (by depressing the reticular nuclei), which would then lead to increase in cortical activity too
the greater the level of activity coming through the reticular formation into the thalamus, the more activated and stimulated the cortex becomes
Hypothalamus has 4 functions
Feeding, mating, fleeing and fighting
- Connections with autonomic NS (PVN neurons project to pre-autonomic neurons in spinal cord)
- Endocrine connections
- Behaviour control (feeding behaviour)
How does hypothalamus perform the four functions
Hypothalamic nuclei such as PARAVENTRICULAR NUCLEI:
Send projections to ANS and to posterior pituitary gland
Can impact on CVS function and renal function within ANS
https://en.wikipedia.org/wiki/Paraventricular_nucleus_of_hypothalamus#Neurons
Magnocellular release oxytocin and vasopressin
Parvocellular travel dwon to the spinal cord and also release hormones into the hypophysial system to influence ant. pituitary function
State other function of hypothalamus,
Role in feeding as it has many receptors for hormones produced in the gut…. also to do with PARAVENTRICULAR NUCLEUS
State the 3 types of paraventricular
Parvocellular neurosecretory neurons
magnocellular neuronsecretory neurons
centrally projecting neurons (another type of parvocellular)
Where do the centrally projecting parvocellular neurons travel
Travel down the spinal cord and synapse onto preganglionic sympathetic nerves–> changing heart rate, constriction, renal etc
Function of magnocellular neurons
Extend to post. pit to stimulate vasopressin or oxytocin release which then impact on water reabsorption (ADH) and uterine contraction (uterine)
Effect of activating and inhibiting PVN on food,
Activating leads to fullness and inhibition leads to feeding
What is the suprachiasmatic
Involved in sleep/wake cycles, reponsive to light.
Light sensitive retinal ganglion cells are connected to hypothalamic suprachiasmatic nuclei, particularly blue light (which activate the suprachiasmatic nuclei)
How does suprachiasmatic nucleus influence sleep and wake cycles
SC nuclei neurons synapse with paraventricular nuclei which travel down to the spinal cord, impact on the intermediolateral column then up the cervical spinal cord, synapse on the superior cervical ganglion and then travel to the pineal gland which regulates melatonin release
What would lesions of the SCN cause
Sleep disturbances, which is a symptom of schizophrenia
What do the following control:
Amygdala
Basal Ganglia
Hippocampus
A: fear, emotion, anxiety
BG: movement
HC: memory
Loss of neurons from the intralaminar nuclei are associated with what problems
Parkinson’s and progressive supranuclear palsy (PSP)
THINK- it goes to BG so going to affect movement e.g. like in parkinsons
T/F hypothalamus usually has contralateral connections with other nuclei
F: mostly ipsilateral
Outline the area of cortex associated with each of the following specific thalamic nuclei: Ventral lateral Ventral anterior Ventroposterolateral Ventroposteromedial Laterial geniculate Medial geniculate
Ventral lateral and ventral anterior - motor cortices (primary, premotor and supplemetnary)
Ventroposterolateral- somatosensory (body) (you know it’s lateral cos the body goes more lateral than the head!)
Ventroposteromedial- somatosensory (head)… so receives fibers from the solitary tract and trigeminal nerve to the post central gyrus
Laterial geniculate- visual (thin L for Light)
Medial geniculate- auditory (think M for Music)
State the different types of thalamic nuclei
Speicifc- going to primary cortical areas
Association- connected to association cortex
Reticular- not connected to cortex, connected to other thalamic nuclei
Intralaminar- connected to all cortical areas
Outline the type of association cortex linked to the following thalamic nuclei:
Anterior, lateral dorsal and dorsomedial
Lateral posterior and pulvinar
Anterior, lateral dorsal and dorsomedial: Mamillary bodies (ant), hypothalamus (lat dorsal) and cingulate and prefrontal
Lateral posterior and pulvinar: parieto-temporo-occipital and prefrontal
Examples of hypothalamic structural damage
Craniopharyngioma, other tumours (glioma, meningioma etc), sarcoidosis and langerhans cell histiocytosis
T/f hypothalamus has largely ipsilateral connections with other nuclei
T
Which area of the cortex is the hypothalamus associated with
Olfactor system and limbic system
How does hypothalamus control behaviour
We already said it contros 4 Fs using paraventricular nucleus etc.
Behavioural control includes; Eating and drinking Expression of emotion Sexual behaviour Circadian rhythm Memory
Hypothalamus and limbic system have a motivational process.. there is a pleasure centre in the limbic system… i.e. eating when you are hungry achieves pleasure… reinforces benefical behaviour.
Goes wrong in addiction
Hypothalamic tumour presenting symptoms
Polydipsia, plyuria, absent menses
Other thing sthan hypothalamic tumour can lead to
Laile emotions, inapproproaute sexual behaviour, memory lapse, temp fluctaution, thryoid/adrenal/gonadal dysfunction, hyperphagia
Where do association nuclei of the thalamus (i.e. those which relate to association cortex) get their major input from
From the cortex.
E.g. pulvinar, the largest association nucleus, receives information from the superior colliculus and also the association cortex. is receives afferent projections from the superior colliculus as well as from the association cortex. It projects to secondary visual areas and to association areas in the parietotemporal region. This contributes to visual perception and eye movements
