Neuroendocrinology Flashcards
Talk about the historical origins of neuroendocrine interactions?
Neuroendocrinology passed through several phases
1. Ancient foundations
2. Discovery of Hormonal secretion
3. Birth of endocrinology
4. Emergence of neuroendocrinology
5. Modern advances
Mention some notable figures in the history and progressive study of neuroendocrine interactions?
- Hippocrates
- Galen
- Thomas Wharton
- Arnold berthold
- Claude Bernard
- Charles Brown-sequard
- Bayliss & starling
- Geoffrey Harris
- Roger guillemin & Andrew schally
Why do blind girls show pubertal changes later than girls with sight?
Let’s understand some basics first.
The pineal gland produces melatonin which modulates sleep cycle. Light exposure suppresses melatonin production. While darkness stimulates it.
Melatonin is found to be higher In individuals with total blindness.
Melatonin has been shown to influence the hypothalamic-pituitary-gonadal (HPG) axis, which controls the release of hormones involved in puberty.
Melatonin can inhibit the release of gonadotropin-releasing hormone (GnRH), which is essential for the initiation of puberty.
List some examples of neuroendocrine interactions.
- Adrenal secretion from Adrenal medulla
- Influence of temperature regulation
- Release of posterior pituitary hormones
- Release of Renin
- Servo mechanisms(positive and negative feedbacks)
- Bruce effect
Talk about the hypothalamus
The hypothalamus is a diencephalic structure alongside the thalamus and pineal gland. It is situated in the ventral diencephalon, just below the thalamus .
The hypothalamus is formed by several nuclei scattered in the walls and floor of the 3rd ventricle, extending from the optic chiasma to the mamillary body.
Mention the Nuclei of the hypothalamus
- Preoptic
- Supraoptic
- Para ventricular nucleus
- Suprachiasmatic nucleus
- Arcuate nucleus
- Ventromedial nucleus
- Dorsomedial nucleus
- Posterior nucleus
- Mammillary bodies
What are the functions of the Preoptic nucleus of the hypothalamus?
- Regulates body temperature
- Involved in sleep-wake cycles
- Secretes GnRH, essential for reproductive function.
What are the functions of the Supraoptic nucleus of the hypothalamus?
- Produces ADH
- Lesions can cause diabetes insipidus
What are the functions of the Paraventricular nucleus of the hypothalamus?
- Produces oxytocin and ADH
- Secretes Corticotropin-releasing hormone (CRH), which regulates HPA axis and stress response.
- Regulates appetite and autonomic functions.
What are the functions of the Suprachiasmatic nucleus of the hypothalamus?
- Master Circadian clock, received light input from the retina to regulate the sleep-wake cycle.
- Controls release of melatonin from pineal gland
What are the functions of the Arcuate nucleus of the hypothalamus?
- Controls appetite via Leptin (Satiety) and Ghrelin (hunger) signalling
- Produces dopamine, which inhibits prolactin release
- Secretes GnRH
What are the functions of the Ventromedial nucleus of the hypothalamus?
- Regulates Satiety, lesions cause Hyperphagia (excessive eating and hence obesity)
- It is also involved in sexual behaviour.
What are the functions of the Dorsomedial nucleus of the hypothalamus?
- Regulates feeding, body weight and autonomic functions
- Involved in aggression and stress response
What are the functions of the Posterior nucleus of the hypothalamus?
- Controls heat conservation(shivering, Vasoconstriction)
- Lessons can cause poikilothermia (loss of temperature regulation)
What are the functions of the Mammillary bodies of the hypothalamus?
- Important for memory consolidation, and part of the limbic system.
- Lessons can cause Wernicke-korsakoff syndrome
The hypothalamus is connected to the posterior pituitary through??
Hypothalamo-hypophyseal tract
The hypothalamus is connected to the anterior pituitary through?
Hypothalamo-hypophyseal portal system
What are some features of portal vessels?
- Absence of blood brain barrier
- Large diameter of blood vessels and presence of fenestrations for effective communication.
- Presence of other centres which perform functions, such as; Osmoreceptors, BP sensors, Thermo receptors.
Which nuclei of the hypothalamus contains the releasing/inhibiting factors?
Arcuate nucleus.
These releasing factors are sent to the pituitary through a tract called Tuberoinfundibular tract to the median eminence of the pituitary
The releasing/inhibiting factors are also known as?
Hypophysiotrophic hormones
Talk about the pituitary gland
Pituitary gland, also called Hypophysis is a small endocrine gland located in the sella turcica of the sphenoid bone.
It has 2 parts
The 2 parts of the pituitary gland?
- Anterior pituitary
- Posterior pituitary
The anterior pituitary has 3 sub parts, namely?
- Pars tuberalis
- Pars intermedia
- Pars digitalis
There are 6 hormones from the anterior pituitary.
Name them
- ACTH
- LH
- FSH
- TSH
- Somatotropin
- Prolactin
The first 4 are often called tropic hormones, because they stimulate other endocrine glands
Explain the action of Somatotropin
Somatotropin also called growth hormone, acts through somatomedin secreted by the liver to cause growth.
Sometimes, inspite of normal secretion of growth hormone, dwarfism still occurs due to deficiency of somatomedin.
There are 2 types of somatomedin, explain?
- IGF -I : acts on bones and protein metabolism through cyclic AMP
- IGF -I : plays a vital role in fetal growth
Growth hormone is regulated by?
- GHRH/GHRP
- Hypoglycemia
- Fasting/Starvation
- Exercise
- Stress
- Trauma
- Initial stages of sleep
Oversecretion and under secretion of growth hormone cause?
Over secretion of growth hormone caused Gigantism
Under secretion leads to Acromegaly
Talk about the hormone Prolactin
Prolactin is necessary for milk secretion and growth of mammary glands during pregnancy.
Prolactin is inhibited by prolactin inhibiting hormone secreted from the hypothalamus.
Talk about the hormone FSH
FSH meaning follicle stimulating hormone. Is released from basophilic cells of the anterior pituitary based on simulation by GnRH. It’s receptors are fine in the testis and ovaries.
What is the action of FSH
In males, then in females
FSH acts to
1. initiated spermatogenesis
2. Regulates estrogen secretion in females
(Estrogen regulated FSH & GNRH in negative feedback)
Talk about Luteinising hormone (LH)
LH is also released from the basophilic cells of the anterior pituitary by stimuli from GnRH from hypothalamus. It’s receptors are also in the gonads.
Functions of Luteinising hormone?
- Simulate leydig cells to release testosterone in males
- LH causes ovulation and activated corpus luteum which secretes progesterone.
Talk about ACTH?
ACTH means Adrenocorticotropin hormone, secreted by basophilic cells of the Anterior pituitary.
ACTH regulates glucocorticoids
What are the functions of ACTH?
- Plays major role in cortisol production, which plays vital role in stress, emotion, trauma and a little influence of circadian rhythm
- Regulates glucocorticoids
The release of ACTH is regulated by Corticotropin releasing hormone from the hypothalamus.
Talk about TSH?
TSH means thyroid stimulating hormone, secreted by basophilic cells of the anterior pituitary.
TSH receptors are found in the thyroid gland, and it is regulated by thyrotropin Releasing hormone (TRH)
Functions of TSH?
- Synthesis and release of thyroid hormones (T3 and T4)
These hormones are vital for homeostasis and they regulate metabolism
Talk about the Neurohypophysis?
It has 3 parts;
1. Pars nervosa
2. Neural stalk
3. Median eminence
The hormones from the the posterior pituitary are?
- ADH
- Oxytocin
Explain ADH
Also called Vasopressin, ADH is a polypeptide hormone secreted mainly by the Supraoptic nucleus of the hypothalamus.
It acts on the kidneys by increasing the facultative reabsorption of water from the distance convoluted tubule and collecting duct in the kidneys.
ADH also causes constriction of arteries hence causing increased blood pressure.
I’m the absence of ADH, the distal convoluted tubule and collecting duct are?
Completely impermeable to water,
Leading to excretion of large amounts of water in urine.
This condition is called diabetes insipidus
Talk about oxytocin
Oxytocin is secreted by the para ventricular nucleus of the hypothalamus
Oxytocin uses a positive feedback system
Effects of Oxytocin?
In females,
1. Milk ejection from breast
2. It plays a role in parturition and labour(causes contractions)
3. In non pregnant females, Oxytocin is believed to facilitate the transport of sperm through female genital tract to fallopian tube.
- In males, it is believed that oxytocin facilitates the release of sperm into the urethra and even out during ejaculation.
- Oxytocin is also hypothesised to aid bonding in both males and females(love hormone)
Talk about the historical origins of neuro endocrine interactions
The study of neuroendocrine interactions has been progressive through different eras
1. Ancient foundations
2. Discovery of hormonal secretion
3. Birth of endocrinology
4. Emergence of neuroendocrinology
5. Modern advances
Mention some notable figures that contributed to the history and progressive study on neuroendocrine interactions
Ancient foundations
1. Hippocrates
2. Galen
3. Thomas Wharton
4. Arnold Berthold
5. Claude Bernard
6. Charles Brown-sequard
7. Bayliss & starling
8. Geoffrey Harris
9. Roger guillemin & Andrew schally
Why do blind girls show pubertal changes later than girls with sight?
List endocrine organs you know
- Pituitary gland
- Adrenal gland
- Gonads ( testis, ovaries)
- Pancreas
- Parathyroid gland
- Pineal gland
The pituitary gland is also called?
Master gland
Mention endocrine organs that regulate themselves independent of the pituitary gland?
- Pancreas
- Parathyroid gland
