Neuro 6: Thalamus + Hypothalamus Flashcards
What is the organization of the thalamus?
- divided in 2 by 3rd ventricle
- collection of individual nuclei w separate functions
- sits ventral to the lateral ventricles
What is the function of the thalamus?
- it is a key relay centre to cortical sensory areas
- involved in most sensory systems (except olfactory)
- enhances / restricts signals
Describe the different classification of the thalamic nuclei.
- classification = bases on connection of nuclei with the cortex
SARI
explain each classification of the thalamic nuclei
SARI nuclei
S = specific
–> connected to primary cortical areas
A = association
–> connected to association cortex
R = reticular
–> NOT connected to the cortex
I = Intralaminar
–> connected to ALL cortical areas
(in Specific nuclei) What are the 2 diff nuclei that relays sensory info from different parts of the body?
BELOW THE NECK:
- ventral posterolateral
HEAD:
- ventral posteromedial
Describe the different divisions of the functional cortical areas
Intraluminar + Reticular nuclei are both part of the ____ _____ _____ which is the system that maintains consciousness
Intraluminar + Reticular nuclei are both part of the RETICULAR ACTIVATING SYSTEM which is the system that maintains consciousness
Why is intrathalamic connection important for the reticular nucleus?
- due to intrathalamic connection
- it is able to influence flow of information through the other nuclei –> to the cortex
- it gets activated by projections (from the brainstem)
- and increases activity going through the other nuclei.
(indirect method of influencing activity of cortex)
core of grey matter through brainstem =
core of grey matter through brainstem = reticular formation
Describe the function of the reticular formation
- reticular formation projects up to the thalamus
- then intralaminar nuclei modulates activity of the cortex (level of consciousness/awareness)
(more projection, more activity of cortex)
_______ lies below the thalamus
hypothalamus
hypothalamus is divided through the middle by the ___ ventricle
The _____ _____ + _____ _____ = seen just infront of the hypothalamus
3rd ventricle
note: organization of hypothalamus + thalamus = same
-
What is the function of the hypothalamus
- The hypothalamus = involved in homeostasis
- and it coordinates mechanisms that provide homeostasis
- such as ANS, Endocrine System, Behaviours
- has direct connections with ANS
- has connections with endocrine systems
- and has control over behavior e.g feeding behavior
4F’s
- fighting
- fleeing
- feeding
- mating
What are the 2 systems that has close connection with the forebrain?
- Olfactory System
- Limbic System
Give examples of what is meant by behavioral control:
Give examples of what is meant by behavioral control:
- eating/ drinking
- expressing emotion (e.g pale when scared –> ANS)
- sexual behavior
- circadian rhythm (suprachiasmatic nucleus)
- memory
How is our behavior directed towards homeostatic goals?
- hypothalamus + limbic system have a motivational process
- when homeostasis is achieved, activity of pleasure centre in the limbic system increases
- helps to reinforce beneficial behavior
Note: but also bad e.g addiction
What are some presenting symptoms of hypothalamic tumor?
- polydipsia
- polyuria
- absent menses
What are advanced symptoms of hypothalamic tumor?
- labile emotions
- age
- memory lapses
- temp fluctuation
- decrease in thyroid, adrenal cortex + gonadal function
- hyperphagia
What is the intralaminar nuclei?
- it projects to various medial temporal lobe structures
- comprises of mostly glutamatergic neurones
(loss of neurons in this region = associated with progressive supra nuclear palsy / parkinson’s)
What is the reticular nucleus ?
- forms outer covering of thalamus
- most neurones = GABAergoc
- DONT connect with distal regions but with other thalamic nuclei
- receives input from collaterals of their axons from thalamic nuclei
–> so reticular nucleus acts to modulate thalamic activity through -ve feed back
What is the function of the reticular formation?
- set of interconnected pathways in the brainstem
- involved in consciousness / arousal
- both intralaminar + reticular nucleus receive inputs from ARAS
hypothalamus = has direct/indirect connections with ANS
direct
how does hypothalamus exert effects on the endocrine system?
hypothalamus –> pituitary gland –> different hormones secreted
