Neuroendocrinology Flashcards
What is the definition of a hormone?
→ a cell secretes a hormone
→ not targeted
→ has an effect on target cells depending on whether they have the receptor or not
How do neurotransmitters work?
→ nerve cell secretes NTs
→ across a spatially restricted area
→ acts on an effector cell
What is paracrine secretions?
→ secreted from cells
→ exerts effects at local interstitial fluid
What is autocrine signalling?
→ The cell has receptors for a hormone that it secretes
What are neuroendocrine cells?
→ neurosecretory cells that release signal molecules from their synaptic terminals into the blood
What are neuroendocrine cells controlled by?
→ synaptic transmission from presynaptic neurons
What are 3 examples of neuroendocrine cells?
→ chromaffin cells of adrenal medulla
→ hypothalamic magnocellular neurons
→ hypothalamic parvocellular neurons
How does neuroendocrine transmission work?
→ Nerve cell releases NT
→ NT acts on a neuroendocrine cell
→ Releases a signalling molecule from axonal end
→ it doesn’t synapse
→ terminals target capillaries
→ substance diffuses and acts as a hormone
What is the pituitary made from?
→ 2 independent structures
How does the pituitary form in the embryo?
→ Evagination of the floor of 3rd ventricle
→ Evagination of oral ectoderm
→ Rathkes pouch pinched off
What is the posterior lobe of the pituitary an extension of?
→ The hypothalamus
What are the two nuclei of the hypothalamus?
→ Parvocellular nuclei
→ Magnocellular nuclei
Where do the parvocellular nuclei project to?
→ small neurons with small axons → project to the median emininence → release hormones to the capillary network → carried by hypophyseal portal veins → to anterior pituitary
What is the posterior pituitary supplied and drained by?
→ Inferior hypophyseal artery
→ Inferior hypophyseal vein
What is the anterior pituitary supplied and drained by?
→ Superior hypophyseal artery
→ forms a network at the base of the hypothalamus
→ Portal veins - a second capillary network
Where do the magnocellular nuclei project ?
→ Project to the posterior pituitary
→ release capillaries supplied by inferior hypophyseal artery
What is the pathway of ADH?
→ Synthesized in the magnocellular nuclei
→ packaged into vesicles and transported along the axons
→ stored in axon terminals
→ released into the hypophyseal capillaries
What kind of hormones do the parvocellular nuclei release?
→ Trophic hormones
→ Hormone releasing hormones
What hormones does the posterior pituitary release?
→ Oxytocin
→ ADH
What hormones does the anterior pituitary release?
→ TSH → ACTH → FSH + LH → Growth hormone → Prolactin → Endorphins
How does ADH get regulated?
→ Sensory neurons in the hypothalamus detect changes in ECF osmolality
→ passed on to magnocellular neurons (supraoptic)
→ increase or decrease in firing of magnocellular neurons
→ + or - in the release of ADH into the posterior pituitary
Describe the cascade of TRH
→ Hypothalamic hormone TRH
→ changed into TSH in the anterior pituitary
→ stimulates thyroid
→ thyroid produces thyroid hormones
Where are the parvocellular and magnocellular nuclei found?
→ in the hypothalamus
What is the brain dependent on?
→ obligatory dependent on glucose
In the absence of circulating glucose where does glucose come from?
→ glycogen stores
When glycogen runs out where does glucose come from?
→ Gluconeogenesis
What does growth hormone stimulate?
→ Lipolysis
→ Promotes release of fatty acids
→ so tissues use fat
→ glucose can be used in the brain
What are the 7 factors that stimulate growth hormone?
→ GHRH → Ghrelin → Hypoglycaemia → Decreased fatty acids → Fasting → Excercise, sleep → stress
What is ghrelin and where is it released from ?
→ Hunger hormone
→ Released by endocrine cells of the stomach
What are the 5 factors that inhibit growth hormone?
→ Somatostatin → GH → Hyperglycemia → Increased fatty acids → IGF-1
What are somatotropes?
→ endocrine cells in the anterior pituitary that secrete GH
How does IGF get produced?
→ GH released from somatotropes
→ GH acts on liver and increases gluconeogenesis
→ Increases IGF
What does IGF from the liver promote?
→ Increase somatic cell growth
→ Increase chondrocyte function (cartilage in bones)
→ Increase bone modelling
What does GH do in the muscle?
→ Increases protein synthesis
What does GH do in adipose tissue?
→ Promotes lipolysis
What are GH concentrations like during life?
→ birth is low
→ increases and stays constant at childhood
→ Increases dramatically during puberty
→ decline during adult life and old age
What does GH deficiency during childhood result in?
→ dwarfism
What is the condition with excess hormone called?
→ Acromegaly
What is acromegaly caused by?
→ pituitary adenoma
What are metabolic effects of acromegaly?
→ Insulin resistance
→ Impaired glucose tolerance and hyperinsulinemia
