Neuroendocrinology Flashcards
1
Q
Pituitary gland
A
- has an anterior and posterior lobe
- anterior lobe secretes many hormones that are regulated by regulatory neurohormones produced by parvocellular neurons of the hypothalamus
- posterior lobe releases 2 hormones that are synthesised in magnocellar cells of the supraoptic nuclei and paravetricular nuclei of the hypothalamus
2
Q
Growth hormone
A
- excess causes acromegaly in adults or gigantism in children
- low levels are associated with dwarfism
- exercise, sleep and stress increase GH release
- GH response to GHRH and the normal sleep-associated release of GH are altered in depression and anorexia nervosa
- secreted by anterior pituitary
3
Q
Prolactin
A
- release is inhibited by dopamine from the hypothalamus
- TRH may facilitate the release of prolactin
- prolactin levels are increased during pregnancy, nursing and during sleep and exercise
- antipsychotics remove the inhibitory control of dopamine by blocking D2 receptors in the tuberoinfundibular tract
- this leads to hyperprolactinaemia, gynaecomastia and galactorrhoea in females
- long standing prolactin increase may lead to osteoporosis
- anterior pituitary hormone
4
Q
Vasopressin (ADH)
A
- posterior pituitary
- vasopressin is thought to play a roe in attention, memory and learning
- vasopressin release is seen in pain, stress, exercises, morphine, nicotine and baribiturates
- alcohol decreases vasopressin release
5
Q
Oxytocin
A
- posterior pituitary
- implicated in mammalian bonding behaviour, social bonding and sexual receptivity
6
Q
Anterior pituitary hormones
A
- GH growth hormone
- LH- luteinizing hormone ( a gonadotrophin)
- FSH- follicle stimulating hormone ( a gonadotrophin)
- ACTH- adrenocorticotrophic hormone (corticotrophin)
- TSH- thyroid stimulating hormone ( thyrotropin)
- prolactin
7
Q
Posterior pituitary hormones
A
- vasopressin (ADH-antidiuretic hormone)
- Oxytocin
8
Q
Hypothalamic hormones
A
- CRH- corticotrophin releasing hormone
- GHRH- growth hormone releasing hormone
- GnRH-gonadotrophin releasing hormone
- TRH- thyrotropin releasing hormone
- SST-somatostatin (inhibits GH)
- PIF- prolactin inhibitory factor (dopamine)
9
Q
Thyroid
A
- TRH from the hypothalamus stimulates secretion of TSH from the pituitary
- TSH then stimulates the release of T4 and T3 from thyroid
- T4 is predominant but converted to T3 by target organs as well as the brain
10
Q
TRH
A
- exogenous administration of TRH briskly increases TSH concentration
- in depression there is a blunted response to TRH
- giving T3/T4 supplements to women during depression seems to help
- thought to increase serotonergic transmission with decreased 5-HT1a sensitivity and icnreased 5-HT2A sensitivity
11
Q
Nerve growth factor genes
A
-activated by T3 during early development but not in the adults brain
12
Q
Lithium
A
- lithium produces hypothyroidism
- especially common in middle aged women who are predisposed to carry antithyroid autoantibodies
13
Q
Adrenal cortex
A
- CRH from the hypothalamus stimulates ACTH release from the anterior pituitary
- ACTH in turn stimulates the release of cortisol from the adrenal cortex
- Cortisol in turn inhibits both CRH and ACTH in a negative feedback loop to maintain homeostasis- HPA axis
14
Q
HPA-axis
A
- involved in regulation of stress response
- with chronic stress the HPA feedback fails and continuous excess cortisol is produced
- this affects the hippocampus and causes hippocampal neurodegenesis with atrophy of hippocampal dendrites, resulting in shrinkage of the hippocampus
- this disrupts long term potentiation (LTP) and leads to impaired memory performance
15
Q
Hypocortisolism
A
- Addisons disease
- causes apathy, fatigue and depression
- causes anxiety, irritability, poor concentration, agitation and emotional lability
16
Q
Hypercortisolism
A
- Cushing’s syndrome
- leads to fatigue, weightgain, cold intolerance, dry skin
- can cause depression, mania, confusion and psychotic symptoms
17
Q
Cortisol
A
-diurnal variation seen- peak levels 6-7 am
18
Q
Dexamethasone suppression test (DST)
A
- dexamethason suppresses endogenous cortisol production if the HPA axis is intact
- patient is given dexamethason at night and then has cortisol levels during the morning
- if cortisol levels rise then this indicates DST non-suppression- failure of the suppression of the ACTH/CRH and continuous production of endogenous cortisol despite being given an exogenous steroid
- DST-non suppression is seen in depression and Cushings
19
Q
Pineal gland
A
- also called epiphysis
- contains pinealocytes that secrete both serotonin and melatonin
- gland also contains calcium deposits that become more prominent with age (corpora arenacea or brain sand)
- contains highest level of serotonin in the body
- melatonin is synthesised from serotonin by serotonin-N-acetylase and 5-hydroxyindole-O-methyltransferase
20
Q
Melatonin synthesis
A
- melatonin is synthesised from serotonin by serotonin-N-acetylase and 5-hydroxyindole-O-methyltransferase
- in pineal gland
- light-dark cycle regulates this
- synthesis is increased with darkness
21
Q
Regulation of pineal gland
A
-regulated by major B-adrenergic mechanisms and B-antagonists such as propranolol decrease melatonin synthesis
22
Q
Melatonin effect
A
-regulates circadian rhythms
23
Q
Start of sleep
A
-increased testosterone
24
Q
Slow wave sleep
A
- increased GH and SST; reduced cortisol
25
Q
REM sleep
A
-reduced melatonin
26
Q
Early morning sleep
A
-increased prolactin
