Anatomy of neuroendo system Flashcards
(25 cards)
What does rostral and caudal mean in humans and mice?
Rostral
H: towards nose
M: towards nose
Caudal
H: towards feet
M: towards tail
Name and explain each of the modes of communication between cells (6)
1) Intracrine: communicating within cells
2) Autocrine: molecules released from cell to act on itself
3) Paracrine: communicating b/w cells - hormone/substance released from one cell + acting on adjacent/target cell
4) Neurocrine: same as paracrine but in brain
5) Endocrine: hormones released from one part of body (travels through bloodstream) to target cells in another part
6) Neuroendocrine: released by neurons into blood vessels to usually act adjacently (e.g. pituitary gland)
2 facts about the Neurosecretory
neuron (2)
- Project over long distances including into the posterior pituitary (hypo -> pituitary)
- Release hormones into the brain (neuromodulation) or peripheral circulation e.g. portal vessels of the anterior pituitary -> stimulates hormone release
Explain the hypothalamus to Anterior
Pituitary cells to rlease of hormones pathway (5)
1) hypo. projects to superior hypophyseal artery
2) Hypothalamic releasing hormone released into axon terminals into capillary plexus of pituitary
3) hormones released e.g. GnRH
4) Hormones act on secretory cells of the pituitary gland
5) hormones secreted
2 facts of Posterior pituitary
(neurohypophysis)
- Not glandular (doe not contain local populations of secretory cells)
- Contains the terminals of neurosecretory (magnocellular) neurons which project from the brain (hypo) and secrete neurons into the pituitary capillaries which then join the general circulation = not specific glands
Tanycytes (glial cells) explained (5)
- Specialist ependymal cells lining the 3rd ventricle
- Part of brain-cerebrospinal fluid(CSF) barrier and blood-brain barrier (ARC/ME)
- Send projections into hypothalamic nuclei
- Capable of nutrient and hormone sensing
- Form part of neurogenic niche (new neurons and glia)
Summary 1 (4)
- Neurosecretory neurons project over long distances release neuropeptides and regulate hormone release
- Anterior pituitary cells secrete hormones in response to tropic factors released by
neurosecretory neurons - Terminals of neurosecretory neurons in the posterior pituitary secrete peptides into the circulation
- Tanycytes are specialist ependymal cells lining the 3rd ventricle
Blood brain barrier (BBB) explained (4)
The entry and exit of substances from the brain is tightly regulated vis BBB
- Endothelial-glia barrier that protects the brain
- Tight junctions & specific transporter controls entry of substances into the brain
- Protects the brain from fluctuations in the periphery
Circumventricular
organs (CVOs) definition
CVO’s are areas of the brain with fenestrated capillaries (no tight junctions)
Tanycytes monitor cerebrospinal fluid composition and pass this information to the circumventricular organ
General features of CVO’s (4)
- Typically located at the midline of the brain
- Close to ventricles within the brain but separated from the cerebrospinal fluid
- Linked to ventricles via tanycyte processes which stretch into the brain
- Most are highly vascularised with fenestrated capillaries
Explain the 2 types of CVO classes (5)
Sensory + Secretory
Sensory:
* Detect circulating factors in the blood e.g. nutrients, hormones, ions
- Express high levels of (hormone and other) receptors
- Have high levels of neural output
- Area postrema (AP)
- Subfornical organ (SFO)
- Organum vasculosum of the lamina terminalis (OVLT)
Secretory:
* Mediate the release of lipophobic hormones into the blood and/or cerebrospinal fluid
- Receive high levels of neural input
- Median eminence (ME)
- Pituitary gland (neurohypophysis = posterior lobe)
- Pineal gland
Localisation of CVO’s (7)
images
Rostral
- SFO + OVLT (sens)
- ME (sec)
- Intermediate pituitary (sec)
- Posterior pituitary + Pineal gland (sec)
- Area Postrema (sens)
Caudal
SFO explained (6)
- Located in the rostral wall of the 3rd ventricle
- Extensive neuronal connectivity with other CVOs (OVLT) + hypothalamic nuclei
- Senses osmolarity (e.g. ions) and hormones (e.g. angiotensin)
- Transmits information from periphery to the autonomic regulatory centres
- Important for regulation of fluid balance and cardiovascular function.
- Also implicated in regulating reproduction (with OVLT) and energy homeostasis (with AP)
OVLT explained (4)
- Located in the anterior wall of the 3rd ventricle
- Extensive neuronal connectivity with other CVOs (SFO) and hypothalamic nuclei
- Contains osmosensors and hormone receptors e.g. GnRH, oxytocin, prolactin
- Integrates information on reproductive status/function as well as fluid homeostasis
Area postrema
(AP) explained (7)
- Located on the dorsal surface of the medulla oblongata (brain stem) proximal to 4th ventricle
- Receives direct neural input from the periphery (vagus and carotid sinus nerves)
- Contains metabolic hormone receptors e.g. leptin, ghrelin, adiponectin
- Also responds to nutrients and noxious stimuli
- Transmits information from periphery to the autonomic regulatory centres
- Important for regulation of energy homeostasis
- Also cardiovascular regulation (with SFO)
Median Eminence
(ME) explained (4)
- Located in the basal hypothalamus at the base of the 3rd ventricle b/w the brain + pituitary gland
- Contains terminals of neurosecretory neurons
- Secrete neuropeptide hormones into the capillaries which supply the pituitary gland
- GnRH
-GHRH
-Dopamine
-TRH
-CRH - ME also contains receptors for hormones and nutrients (can also act as a ‘sensory’ CVO)
Summary 2 :
Circumventricular
organs (5)
- Two broad types: Sensory & secretory
- All are multifunctional: receptors for multiple hormones, transporters (glucose and ions)
- Each CVO mediates multiple aspects of physiology: e.g. SFO is important for regulation of fluid homeostasis, metabolism and reproduction
- Mediate communication between brain and periphery via circulating factors
- Extensive mono- and poly-synaptic connectivity with other brain regions including other CVOs
What is the hypothalamic nuclei made up of? (13)
–> AN: arcuate nucleus (ARC)
–> VMN: ventromedial nucleus
DMN: dorsomedial nucleus
–> PVN: paraventricular nucleus
DHA: dorsal hypothalamic area
PFA: perifornical area
LHA: lateral hypothalamic area
–> SCN: suprachiasmatic nucleus
SON: supraoptic nucleus
POA: preoptic area
MB: mammillary bodies
ME: median eminence
III-V: third ventricle
ARC explained (4)
- Located in the medial basal portion of the hypothalamus proximal to the ME and 3V
- Sends projections to a variety of hypothalamic and extra-hypothalamic brain regions
- Best known for its role in regulating feeding behaviour
- Also contains tuberoinfundibular neurons (Dopamine neurons that regulate prolactin from the pituitary)
VMN or VMH explained (4)
- Located proximal to the ARC and DMH
- Sends projections to a variety of hypothalamic and extra-hypothalamic brain regions
- Best known for its role in regulating glucose homeostasis, female sexual behaviour and male social aggression
- Neuropeptide identity of neurons less well characterised
- BDNF
-Glucose - excited neurons - Glucose- inhibited neurons
- Extensive hormone r’s expression (Leptin, Oestrogen, insulin)
SCN explained (4)
- Located basally above the optic chiasm rostrally in the hypothalamus
- Receives projections from the eye and sends projections to a variety of hypothalamic sites(encoding information about timing and seasonality) and pineal gland (melatonin production)
- Best known for its role in regulating circadian rhythm
- Contains neurons expressing:
- Vasoactive intestinal peptide (VIP)
- Gastrin releasing peptide (GRP
- Vasopressin
PVN or PVH explained (4)
- Located proximal to the at the top of the third ventricle within the hypothalamus
- Sends projections to the posterior pituitary and ME. Receives projections from brainstem, ARC, SCN, limbic system (some of which are reciprocal)
- Contains neurosecretory neurons:
- Magnocellular (nerve terminals residing in posterior pituitary)
– Oxytocin
–Vasopressin - Parvocellular or parvicellular (nerve terminals residing in the ME)
–Corticotrophin-releasing hormone (CRH)
–Vasopressin
–Oxytocin - Also contains (parvocellular) interneurons that project to other brain regions
What effect/s do Neurosecretory neurons have on hormone release? (2)
direct release from pituitary
e.g. Direct synapses between magnocellular neurons and cells of the posterior pituitary
+
indirect effect on release of hormones from pituitary
e.g. Terminals of parvocellular neurons in the ME release neuropeptides into the portal vessels supplying the anterior pituitary
what does hypothalamic-pituitary connectivity regulate? (9)
Hypothalamic-pituitary connectivity regulates multiple aspects of physiology:
- SON
- PVN
- GH
- ACTH
- TSH
- LH
- FSH
- PRL
- MSH
