Lecture 12, 13, 14 - Hypothalamus Flashcards
The hypothalamus is REGIONALLY divided into: (x4)
name the nuclei contained in each region [total=12]
- preoptic region (medial & lateral preoptic nuclei)
- supraoptic region (ant. hypothalamic, supraoptic, suprachiasmic, paraventricular)
- tuberal region (Dorso & ventromedial, arcuate, infundibulum)
- mammillary region (mammillary bodies, posterior hypothalamic)
the hypothalamus is FUNCTIONALLY divided into:
- lateral
- middle
- periventricular
The fornix divides which two hypothalamic functional zones?
middle and lateral
periventricular -> middle [FORNIX] -> lateral
what are the functions of the PERIVENTRICULAR zone (x1)
- regulates release of endocrine hormones from ANTERIOR pituitary gland
What are functions of the middle zone (x3)
- regulating release of OXYTOCIN & VASOPRESSIN from POSTERIOR pituitary gland
- regulates autonomous system
- sets biological rhythm of organism
which hypothalamic nucleus regulates the organism’s biological rhythm?
suprachiasmic
What are functions of the LATERAL zone ? (x3)
- regulating sleep-wakefullness
- regulating feeding cycle
- integrates information from other hypothalamic nuclei and cortical structures engaged in emotions
The hypothalamus is supplied by which artery?
the hypothalamic branch of the posterior communicating artery
What is the Blood-brain barrier? What are its functions?`
- a semi-permeable barrier which protects the blood flow from brain extracellular fluid (BECF) that is unique to the CNS.
- made from astrocytes and endothelial cells joined by tight junctions which line the interior of CNS arteries.
- allows passage of water molecules, some gases, lipid soluble substances, amino acids and glucose.
- not present on circumventricular organs
What are circumventricular organs? (dont list them yet)
- organs which are located around the border of the ventricles,
- extensive vasculature but ‘leaky’ BBB
- alternate route for hormone secretion into bloodstream
-
List the circumventricular organs (divide into the two types)
SENSORY ORGANS: sense plasma molecules in bloodstream and convey info to other brain regions for DIRECT COMMUNICATION between ANS and systemic circulation
- subfornical organ
- area postrema
- vascular organ of lamina terminalis
SECRETORY ORGANS: secrete hormones and glycoproteins to peripheral bloodstream in repsonse to internal (brain) and external stimuli
- Pineal gland
- Neurohypophysis (post. pituitary gland)
- sub commissural organ
- intermediate lobe of pituitary gland
- median eminence
all CVO’s EXCEPT ____ feature extensive vasculature with ___ capilliaries, causing a “leaky” BBB
SCO (sub commissural organ)
fenestrated (perforated, presence of apertures)
The Sella Turcica and Diaphram Sellae are both
dural reflections which encase the pituitary gland
The hypophysis and hypothalamus together secrete a total of ___ hormones (__each), to regulate all aspects of ____(x4)
- 16
- pit = 7, hyp = 9
- growth, metabolism, development, homeostasis
the anterior pituitary gland is known as___and posterior is known as ____
- adenohypophysis
- neurohypophysis (contains neuronal axons from hypothalamus)
The adenohypophysis (distal, intermediate) is formed from___ and the neurohypophysis is formed form the ____
- ectodermal endothelium of roof of mouth
- nerve tissue of floor of diencephalon
Which lobe of the pituitary gland is PART of/DEVELOPS from the hypothalamus?
neuro/posterior (forms from floor od diencephalon aka hypothalamus)
what are hormones released by the adenohypophysis called?
tropic hormones/ tropics
What does the adenohypophysis do?
- secretes and releases tropic hormones
- regulated by hypothalamus
how does the hypothalamus regulate the secretion and release of hormones from the adenohyp.?
by releasing hypothalamic releasing/inhibiting hormones into the PRIMARY PLEXUS of the HYPOPHYSEAL PORTAL SYSTEM, which travels to the SECONDARY PLEXUS via the PORTAL VEINS, stimulating hormone release into the circulation.
how is the portal system different from normal blood flow?
NORMAL:
heart -> artery -> capillary -> vein -> heart
PORTAL SYSTEM:
heart -> artery -> capillary network -> portal vein ->2nd capilary network -> vein -> heart
what are Somatrophs?
- they are hormone secreting neurons of the adenohypophysis which secrete SOMATOTROPIN or HUMN GROWTH HORMONE (hGh).
- they are the most plentiful endocrine cell in the anterior pituitary.
Hypoglycemia increases production of ___
hyperglycemia increases production of__
- GHRH (growth hormone releasing hormone)
- GHIH
high amount of hGH (human growth hormones) increases?
blood-glucose level
describe the functions and properties of the neurohypophysis
- posterior pituitary gland
- part of hypothalamus
- does NOT secrete hormones
- STORES & RELEASES hormones
- oxytoncin, vasopressin
- contains axons from hypothalamus
The neurohypophysis recieves axons (thus hormones) from which two hypothalamic nuclei?
- paraventricular (oxytocin)
- supraoptic (vasopressin)
The adenohypophysis receives blood supply from the ___and drained by the ____.
the neurohypophysis recieves blood from the ___ and is drained by the ____.
- superior hypophyseal artery
- anterior hypophyseal vein
- inferior hyp. artery
- posterior hyp. vein
The adenohypophysis is part of the parvocellular or magnocellular neurosecretory system?
- parvocellular
the hypothalamus has 5 afferent projections. What are they and where do they originate (specifically) and which nuclei do they terminate?
- fornix (from SUBICULAR CORTEX of hippocampal formation to ANTERIOR NUCLEUS OF THALAMUS, MEDIAL HYPOTHALAMUS & MAMMILLARY BODIES)
- stria terminalis (from medial amygdala to medial hypothalamus & Bed nucleus)
- ventral amygdalofugal pathway (from basolateral amygdala to lateral hypothalamus and midbrain)
- Medial forebrain bundle (septal area)
- retinohypothalamic fibres (retina)
what are two efferent projections from the Hypothalamus?
- mammillothalamic (mammillary bodies -> anterior nucleus of thalamus, control of emotional expression part of papez circuit)
- mammillotegmental (mammillary bodies -> midbrain tegmentum, for hypothalamic control of autonomic systems)
Which three pathways allow hypothalamic control of the ANS?
- Dorsal longitudinal fasciculus
- medial forebrain bundle
- mammillotegmental pathway
Which hypothalamic nucleus gives rise to the DLF and where does this pathway innervate? what is its function?
- paraventricular nucleus
- along brainstem and all levels of spinal cord
- mediate sympathetic & parasympathetic NS
Which hypothalamic nucleus gives rise to the MFB and where does this pathway innervate? what is its function?
- paraventricular nucleus (incl. fibres from basal forebrain and septal nuclei)
- same as DLF
- mediate sympathetic & parasympathetic NS
Which hypothalamic nucleus gives rise to the Mammillotegemental tract and where does this pathway innervate? what is its function?
- mammillary bodies
- autonomic nuclei of brainstem (pontine & midbrain reticular formation)
- mediate ONLY parasympathetic NS
What are paravertebral/sympathetic chain ganglia?
- chains of ganglia of the sympathetic NS, which exist next to the spinal cord.
- fibres from the spinal cord, which enter these ganglia are called PREGANGLIONIC fibres
- fibres that exit these ganglia to innervate visceral organs are called POST-GANGLIONIC fibres.
- the existence of this chain allows for preganglionic fibres to travel vertically through the chain and innervate higher or lower levels of the spinal cord.
does the sympathetic nervous system INCREASE or DECREASE blood-sugar level?
INCREASE
what is the major difference between parasympathetic and sympathetic nervous systems?
the effects of the parasympathetic NS are LOCALISED and TEMPORARY
Which hypothalamic nucleus is the MASTER BIOLOGICAL CLOCK?
SCN - suprachiasmic nucleus
- synchronises inner clock with environmental/social clock
- follows circadian rhythm (24hrs)
the SCN always communicates with other hypothalamic nuclei via the ___
PVN
which neurotransmitter is MOST used by the SCN?
GABA
explain the concept of melatonin release during day and night
DAY:
daylight EXCITES GABAergic neurons in the SCN hence, inhibiting neurons which communicate with the PVN, leading to inhibited melatonin production.
NIGHT:
lack of light DOES NOT excite inhibitory function of GABAergic neurons in the SCN, hence excitatory neurons project to PVN which then encourage production of melatonin.
