Neuroendo Flashcards
What does ‘anorexigenic’ mean?
Inhibiting food intake
What does ‘orexigenic’ mean?
Driving food intake
What are neurohormones?
Hormones produced and secreted by neurones
What is neurosecretion?
Neuronal release of chemical agents into the circulation
What is the difference between neuro-secretory cells and neurones?
Neuro-secretory cells…
- Require more mitochondria
- Peptidergic; peptide is synthesised in the cell body as an inactive precursor
Where are neuro-secretory cells found?
Neurohypophysis
Infundibular system
What is excitation/ secretion coupling?
Depolarisation via action potentials at the neurosecretory terminals -> hormone secretion
How do we know whether potassium or calcium is most important for neurosecretion?
Potassium:
Stick pituitary gland in a potassium bath -> depolarisation -> vasopressin release
Calcium:
Treatments that raise calcium influx cause hormone release
Agents blocking calcium influx interfere with secretion
greater extracellular calcium stimulates vasopressin release.
What are the stages of neuroendocrine transduction?
- Action potential
- Depolarise axonal terminal
- Increase intracellular calcium
- Vesicular fusion
- Exocytosis of granular contents
- Amplitude of release is proportional to frequency of action potentials.
What is a neuronal reflex?
Unbreakable pathway where a particular stimulus always results in a particular action.
What are examples of 3-tier neuroendocrine systems?
HPG
HPT
HPA
What are examples of 2 tier neuroendocrine systems?
Growth hormone
Prolactin
Describe the blood supply of the pituitary gland
Superior hypophyseal artery - median eminence and pituitary stalk
Inferior hypophyseal artery - posterior lobe and anterior lobe
These arteries are connected by the trabecular artery.
Describe the venous drainage of the pituitary system
The arteries drain into the venous sinuses which carry stuff from both lobes out into the body
What are hypophyseal hormones?
Hypothalamic hormones controlling the pituitary
What is oxytocin?
Small hormone consisting of nine amino acid peptides and one internal disulphide bridge.
Where does oxytocin come from?
Posterior pituitary
- Synthesised as a pro-hormone (in neuronal cell bodies) in magnocellular neurones.
- Packaged into neurosecretory granules and transported down neurones where it’s released into the blood from specialised terminals.
What are ‘neurophysins’?
Carrier proteins within neuronal secretory vesicles that have no biological effects in circulation.
What are the specialised terminals that release oxytocin?
Neurohypophysis
Neural lobe
Pars nervosa
How is oxytocin stored?
Within the dendrites of magnocellular neurones
What are the endocrine (peripheral) actions of oxytocin?
Milk ejection in lactating animals
Uterine contraction during parturition
Oxytocin endocrine actions in males
What are the central/ neuromodulator (behavioural) actions of oxytocin in mammals?
Post-partum maternal behaviour
Pair bonding in monogamous social species
Social interactions
What are the arguments in favour of oxytocin as a ‘morality drug’?
- Correlates with level of perceived trust (measured via monetary games)
- Increases trust and generosity in donors within a trust experiment
- Increases perception of attractiveness and trustworthiness
What are the arguments against oxytocin being a ‘morality drug’?
- Plasma oxytocin isn’t always properly tested or corrected for (overestimated or mistaken for similar molecules)
- Oxytocin is normally undetectable and it remains unknown how secretion is triggered.
- Monetary games can measure risk more than trust
- No evidence that intranasal administration increases intra-cerebral concentration.
- How do you accurately measure morality?