Principles of Neuroendocrinology Flashcards
1
Q
Neuroendocrinology
A
- Interaction between the nervous system and the endocrine system
- Hormones release can modulate neuronal function
2
Q
How are glands innervated?
A
- Innervated by autonomic nerves
- Directly control function and/or regulate blood flow
3
Q
Hypothalamus
A
- Major link between the nervous and endocrine system
- Hormones regulate other endocrine glands secretions
- Regulates function of the pituitary gland
- Located below thalamus (most ventral part of the diencephalon)
- Encapsulates ventral portion of the third ventricle
- Ends in pituitary stalk: tubular connection to pituitary gland
- In proximity to fourth and third ventricle (fluid): communication between different brain regions
- Area with no blood brain barrier (BBB): median eminence (connects hypothalamus to pituitary gland)
- Collection of neurosecretory centers or nuclei
4
Q
Paraventricular Nucleus (PVN)
A
- Contains cells that secrete pituitary releasing hormones (ex: TRH and CRH) as well as posterior pituitary hormones (ex: oxytocin and vasopressin)
5
Q
What can modulate hypothalamic function?
A
- Input from internal and external environment (homeostatic and neuroendocrine)
6
Q
Pituitary Stalk
A
- Connects hypothalamus to pituitary glands (posterior)
- Made of nerves and blood vessels
7
Q
Pituitary Glands
A
- Two subdivisions of pituitary gland are the anterior (adenohypophysis) and posterior (neurohypophysis) lobes
8
Q
Adenohypophysis (Anterior Pituitary)
A
- Pars tuberalis (portion surrounding stalk), pars distalis (majority of anterior lobe), and pars intermedia (middle)
- Hormonal control rather than neural
- Hypothalamic neurons: releasing and inhibiting hormones
- Hormones are transported to axon endings off median eminence
- Hormones secreted in hypothalamo-hypophyseal portal system and regulate secretion of the adenohypophysis
9
Q
Neurohypophysis (Posterior Pituitary)
A
- Hypothalamic neurons producing hormones, axonal processes of these neurons (neural stalk) and posterior pituitary glands
- Composed of neural tissue
- Neural control through hypothalamo-hypophyseal tract
- No myelinated fibers extend from the SON and the PVN
- Conveys two peptide hormones: ADH (antidiuretic hormone or vasopressin, SON) and oxytocin (PVN)
- Stored in posterior pituitary
- Release controlled by neuroendocrine reflexes
- Vasopressin and oxytocin are nonapeptides derived from a common ancestral gene
- Hormones are produced in the SON and PVN by magnocellular neurons
- PVN: smaller neurons co-secrete VP and CRH
- VP synthesis sites are close to osmoreceptors (sense change in electrolyte concentrations)
- Neurophysins are secreted along their respective hormones, they do not have known biological activity
- Copeptin is also released with VP
- OT and VP release is under the control of several separate signals
10
Q
Hypothalamo-Hypophyseal Portal System
A
- Portal circulation exists when a second capillary bed follows first
- Portal circulation supplies two organs
- Benefits of portal: regulate amount of hormone released (don’t need a high concentration)
- Carries hypothalamic releasing hormones to the pituitary
11
Q
What are the three portal systems within the body?
A
- Hypothalamo-Hypophyseal
- Hepatic portal
- Renal portal
12
Q
Explain the hormonal regulation of physiology and behavior.
A
- Neural hormonal stimuli affect hypothalamic secretions
- Hormones release can be pulsatile (hypothalamus and adenohypophysis)
- Message is amplified along the way
- Negative feedback loops (short and long) are present
- Anterior (trophic) hormones, in addition to stimulating distal hormone secretion, can act as growth factor for the distal gland
13
Q
What are the hypothalamic releasing hormones?
A
- Thyrotropin releasing hormone (TRH)
- Corticotropin releasing hormone (CRH)
- Growth hormone releasing hormone (GHRH)/Somatocrinin
- Gonadotropin releasing hormone (GnRH)
- Prolactin releasing hormone/inhibitory
- Somatostatin
- Dopamine
14
Q
What are the anterior pituitary hormones?
A
- TSH, LH, FSH (glycoproteins)
- Shared common alpha-subunit with different beta-subunits
- Growth hormone: two forms, one derived from all five exons and one missing part of exon III
- Prolactin: post translational modifications lead to different forms (can dimerize, aggregate, bind to different Ab)
- POMC derivatives: ACTH, alpha-MSH, beta-lipoprotein, endorphin
- Product synthesized varies based on cell (control multiple physiological functions)
15
Q
HPA Axis and Stress
A
- Hypothalamic- pituitary -adrenal axis
- Regulates stress response
- Neuroendocrine system that controls reactions to stress
- Release of cortisol
- Negative control: inhibits anterior pituitary and hypothalamus (shuts off)
16
Q
HPT Axis and Metabolism
A
- Hypothalamic- pituitary - thyroid
- Endocrine system involved in metabolism regulation
- Negative control: thyrotroph cells and hypothalamus
17
Q
HPG Axis and Reproduction
A
- Hypothalamic- pituitary- gonadal axis
- Regulates development, reproductive, and aging
- Hypothalamus (preoptic nucleus) produces gonadotropin-releasing hormone (GnRH)
- Anterior gland produces LH and FSH
- Gonads produce estrogen and testosterone
18
Q
Enteroendocrine cells
A
- Cells within the GI that can produce and secrete GI hormones or peptides
- Usually have letter names (ex: K, L, I)
- Secrete into the lamina propria to send paracrine, endocrine, and neurocrine signals
19
Q
Enterochromaffin
A
Serotonin (5-HT) producers (not letter names)
20
Q
What system within the peripheral nervous system governs the GI tract?
A
Enteric/ intrinsic nervous system
21
Q
Why do we need hormonal control mechanisms in the GI tract?
A
-GI system undergoes periods of activity (postprandial) and quiescent (intermeal)
- Macronutrient content of a meal can vary
- GI tract is long tube; proximal distal regions needs to be able to communicate and also to accessory organs (ex: pancreas)
22
Q
Explain the neural communication between the gut and the brain.
A
- Activation of vagal afferents (lamina propria)
- Monitor presence/absence of nutrients
- Trigger appropriate behavioral changes (gastric, pancreatic secretion, gastric emptying, regulation of food intake)
23
Q
How is the presence or absence of nutrients monitored?
A
- EECS cells: release peptides in response to chemical or mechanical stimuli
- Neuromodulatory lipids: endocannabinoids
- Specific afferents respond to stretch and tension
24
Q
Satiety Signals
A
- Stomach, proximal, and distal intestine
- Signal causes the sensation of fullness leading to a decrease in meal size and impairing its activity results in an increase in food intake
- Does not lead to an illness or malaise but is associated with a normal behavior and is stimulated by ingested food with a temporal profile
25
Q
Cholecystokinin (CCK)
A
- Satiety, anorexigenic peptide
- Released by I cells in the upper GI
- Presence of fatty acids and proteins
- Delays gastric emptying, stimulate gastric and pancreatic secretions
- Reduces food intake
- Acts via activation of CCK1R on vagal afferents
26
Q
What is the result of fat consumption?
A
Decrease in CCK sensitivity
