NEURO: Neurohormones Flashcards

Question

As a recap, describe oxytocin.

Answer 1

Normally, it's undetectable, but its levels are elevated during parturition, lactation and mating. It is released in response to peripheral stimuli of the cervical stretch receptors and suckling at the breast. It may also be involved in responses to stroking, caressing, grooming, etc. It regulates the contraction of smooth muscles (e.g. uterus during labour, myoepithelial cells lining the mammary duct, contraction of reproductive tract during sperm ejaculation).

Answer 2

During labour: 1) Baby is pushing against the uterus, and the uterus stretches, stimulating neurones 2) Neurones send a signal to magnocellular neurones to start releasing oxytocin 3) Oxytocin is released into the blood circulation and will act on oxytocin receptors in the uterus to cause uterine smooth muscle contractions 4) Baby is pushed forwards, causing more stretching, and causing more oxytocin release via a positive feedback mechanism 5) This stops when the baby is delivered as there is no more stretching of the uterus

Answer 3

There are also oxytocinergic projections from hypothalamus to other brain regions e.g. olfactory region, amygdala, nucleus accumbens and septum etc. which have no peripheral effects and only social effects found in animals that monogamy is due to high oxytocin receptors located in reward centres, confirming that oxytocin is extremely important for paired bonding behaviour and is seen as a pro-social hormone

Answer 4

- antidepressant - anitpsychotic - social cognition - induces trust - anti-OCD - treatment of autism - anxiolytic (reduces anxiety) - hypnotic

Answer 5

because it is important as a pro-social hormone, it has potential to be used as a psychoactive drug in behavioural treatments

Answer 6

The kidneys secrete renin (in response to low BP, etc.). The renin converts angiotensinogen to angiotensin I. Angiotensin I is converted to angiotensin II. Angiotensin II is detected by the subfornical organ in the brain. The subfornical organ projects to vasopressin cells and neurons in the lateral hypothalamus. The vasopressin then goes to affect the kidneys and cause them to retain more water.

Answer 7

>Bind to cell surface receptors leads to dimerization of the receptors, subsequently recruiting tyrosine kinases (e.g. JAK2 or MAPK) which phosphorylate target protein (e.g. STAT) to induce biological responses. Mutations in the growth hormone receptor gene can result in defective hormone binding or reduced efficiency of receptor dimerization, causing growth hormone resistance (Laron syndrome).

Answer 8

G-protein coupled receptor/adenylate cyclase pathway (Gi & Gs): -stimulation of adenylate cyclases increases intracellular cAMP, that activates PKA which phosphorylate target proteins (e.g. CREB) to initiate specific gene expressions and biological responses Activating mutations of TSH receptor cause thyroid adenomas (constitutive ON) Inactivating mutations of TSH receptor cause resistance to TSH

Answer 9

G-protein coupled receptor (Gq) - PhospholipaseC converted to PIP2 - PIP2 converted to IP3 and DAG - IP3 stimulates Ca2+ release from intracellular stores (ER) - DAG activates PKC, which stimulates phosphorylation of protein and alters enzyme activities to initiate a biological response *loss-of-function mutations in GnRH causes sex hormone deficiency and delayed puberty (hypogonadotropic hypogonadism) Loss-of-function mutations in GnRHR can lead to sex hormone deficiencies and delayed puberty (hypogonadotrophic hypogonadism).

Answer 10

Cytoplasmic/Nuclear Receptors - diffuse across the plasma membrane of target cells and bind to intracellular receptors in the cytoplasm or the nucleus - these receptors function as hormone-regulated transcription factors, controlling gene expression - nuclear receptors commonly share a transcriptional activation domain (AF1), a Zn2+ finger DNA binding domain and a ligand (hormone) binding/dimerization domain

Answer 11

- Loss of visual field (pressure on optic nerve) - Too much growth hormone, causing gigantism and acromegaly - Hypogonadism and infertility - Hypopituitarism (reduced pituitary function) - Too much ACTH secretion, causing excess cortisol secretion (Cushing's syndrome) - Too much PRL (hyperprolactinaemia)

Answer 12

Cause: >Hashimoto’s disease, an autoimmune disease in which the immune system makes antibodies to the thyroid >Seen more often in women and those with a family history of thyroid disease Signs and Symptoms >Induces decreased basal metabolic rate, increasing weight, bradycardia >In terms of behaviour, induces cretinism, cognitive deficits, lethargy and depression >In older people, it may follow radioactive iodine treatment, thyroid surgery or pituitary dysfunction Complications >goitre, heart failure, depression and slowed mental functioning, myxedema, birth defects >Babies may be stillborn or premature with lower IQ later in life >If left untreated can cause mental retardation, slow growth, cold hands and feet, and lack of energy among other things

Answer 13

Hypersecretion occurs if there is too much thyroid hormone. This is known as hyperthyroidism or Grave's Disease. CAUSE: Grave's diseases is also an autoimmune disease. Antibodies attack the thyroid gland and mimic TSH so the gland makes too much thyroid hormone. It often occurs in women (20-50; with a family history of the disease). SIGNS AND SYMPTOMS: - goitre (enlarged thyroid gland) - difficulty breathing - anxiety, irritability - difficulty sleeping, fatigue - rapid or irregular heartbeat - trembling fingers - excess perspiration, heat sensitivity - weight loss despite normal food intake COMPLICATIONS: heart failure - osteoporosis - pregnant women with uncontrolled Grave's disease are at greater risk of a miscarriage, premature birth and babies with low birth weight - Grave's opthalmopathy (occurs if untreated, bulging eyes, relatively rare).

Answer 14

Adrenal insufficiency (AI) is also known as Addison's disease. It occurs when the adrenals do not secrete enough steroids. CAUSE: The most common cause of primary AI is autoimmune. SYMPTOMS: - fatigue - muscle weakness - decreased appetite and weight loss - nausea and vomiting and diarrhoea - muscle and joint pain - low BP, dizziness - low blood glucose - sweating - darkened skin on the face, neck, and back of hands - irregular menstruation

Answer 15

Cause >Excess cortisol secretion >Exogenous Cushing’s syndrome occurs in patients taking cortisol-like medications such as prednisone for the treatment of inflammatory disorders e.g. asthma and rheumatoid arthritis or after an organ transplant >Cushing’s Disease is when a pituitary tumour produces too much ACTH SIGNS AND SYMPTOMS: - weight gain - rounded face and extra fat on the upper back and above the clavicles - diabetes, hypertension - osteoporosis - muscle loss and weakness - thin, fragile skin that bruises easily - purple-red stretch marks - facial hair in women - irregular menstruation