L9 - Hypothalamus - Strucutre and Function Flashcards
What is the major function of the hypothalamus
Maintain a stable internal envronment
Hypothalmus exterts control on what systems
Autonomic nervous system
Endocrine system
Characteristics of physical homeostasis
Body temperature Stress response Reproduction Sleep Electrolyte balance BP Energy balance
What is allostasis
The ability of the body to reset the set points throughout time
What does allostasis imply?
That cells in the hypothalamus have a life long plasticity which is important for survival
Describe how fever can arrise from hypothalamic brain circuits
Need to detect temp changes and modulate the ANS to either retain or dissipate heat
Describe how addiction can arrise from hypothalamic brain circuits
Many recreational drigs work through neural pathways involved in reward and motivated behaviour that form an important part of limbic system function
Describe how anxiety disorders can arrise from hypothalamic brain circuits
Anxiety disorders can have physiological symptoms mediated by the ANS and the limbic system
Describe how obesity can arrise from hypothalamic brain circuits
Feeding behaviour is in part controlled by the hypothalamus and interactions between limbic reward circuitry and the hypothalamus are improtant to feeding behavour
What is the hypothalamus limited by at the anterior and posteiror
ANT - optic chasm and anterior commissure
POST - mammillarybodies
What neurotransmitter is involved in … Stress response
Corticotrophin releasing hormone neruones in the PVN
SF1 neurones in the VMN
What neurotransmitter is involved in … Reproduction
GnRG neurones in ARC
DA neurones in ARC
What neurotransmitter is involved in … Sleep
GABA-ergic and hypocretin neurons in the lateral hypothalamus and zona incerta
What neurotransmitter is involved in … Electrolyte balance and blood pressure
AVP neurones in the PVN
What neurotransmitter is involved in … Energy balanc
POMC and NPPY neurones in the ARC
What neurotransmitter is involved in … Circadian cycle
Neurones in the SCN
What neurotransmitter is involved in …
Mood and agression
Trust
SF1+ neurones in the VMN
Oxytocin and neurones in the PVN
Describe the circuitry in the hypothalamus
Interlinked
One circuit can affect an other
How many classes of PVN neurones are there?
2
What are the two classes of PVN syndrome
Oxytocin
VP
Describe the projection of the PVN neuroens
Project axosn to the posterior pituaitary (neurohypothysis) and secrete into the geeneral circulation
How many classes of neurones are there that secrete regulatory hormones into local portal circulation that directly link to the anterior pituitary - describe their projection
5 classes of neurones from the PVN and ARC which project to the medial eminence
What do the PVN neurones –> posterior pituitary and the neurones from PVN –> portal circulation allow?
BRAIN:BODY communication
What structure is present in the embryonic hypothalamus
Infundibulum
What does the infundibulum split into
Medial eminence and the posterior pituitary
What are the special cells which line the third ventricle
Tanycytes
Describe the morphology og tanycytes
Radial-glia like
Describe how the tanycytes are classified
Position and projection
What do the tanycytes lie in close proximity to
Close to ARC and VMN
What is the role of the tanycytes
What do the tanycytes allow?
Act as gatekeepers - providing a direct link with the circulatory system/peripheral body
Hypothalamus is able to connect to the circulating plasma via fenestrated capillaries in the medial emminence and connects to the CSF via the 3rd ventricle
What is the tanycytes an example of?
The BODY being able to talk to the BRAIN
What 3 mechanisms of the hypothalamus make its tole analogous to servo-control systems
Recieves sensory information from external body
Compares inputs to set points
Adjusts autonomic, endocrine and behavioural responses aimed at maintaining homeostasis
