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5050 > NEUROHORMONES > Flashcards

NEUROHORMONES Flashcards

1
Q

What are the two interconnected systems in the body?

A

The neuroendocrine system and the central nervous system (CNS).

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2
Q

What are the major components of the neuroendocrine system?

A

The hypothalamus, pituitary gland, adrenal glands, thyroid gland, and gonads.

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3
Q

What is the physiological significance of the neuroendocrine system?

A

Regulation of Hormonal Balance, Integration of Nervous and Endocrine Systems, Response to Stress.

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4
Q

What is the central nervous system (CNS) composed of?

A

The brain and spinal cord.

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5
Q

What are the functions of the CNS?

A

Information Processing, Motor Control, Cognition and Emotion, Homeostatic Regulation.

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6
Q

How does communication in the neuroendocrine system differ from the CNS?

A

The neuroendocrine system communicates through chemical messengers (hormones) released into the bloodstream, while the CNS communicates through electrical signals transmitted along neurons.

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7
Q

What are the key regulators of hormone secretion in the neuroendocrine system?

A

The hypothalamus and pituitary gland.

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8
Q

What is the location and function of the supraoptic nucleus (SON)?

A

The SON is located in the anterior hypothalamus and synthesizes and releases vasopressin (ADH), which regulates water balance and blood pressure by acting on the kidneys.

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9
Q

What hormones are synthesized and released by the paraventricular nucleus (PVN)?

A

The PVN synthesizes and releases oxytocin, involved in uterine contractions and milk ejection, and corticotropin-releasing hormone (CRH), which regulates ACTH secretion from the anterior pituitary, leading to cortisol release from the adrenal glands in response to stress.

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10
Q

Where is the arcuate nucleus (ARC) located, and what hormones does it produce?

A

The ARC is situated at the base of the hypothalamus and produces growth hormone-releasing hormone (GHRH), stimulating GH release from the anterior pituitary, and thyrotropin-releasing hormone (TRH), stimulating TSH release to regulate thyroid hormone secretion.

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11
Q

What is the significance of the median eminence?

A

The median eminence is a specialized area at the base of the hypothalamus, serving as the site of hormone release into the hypophyseal portal system.

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12
Q

How do hormones from hypothalamic nuclei reach the anterior pituitary?

A

Hormones such as TRH, GHRH, and dopamine travel via the hypophyseal portal system to the anterior pituitary, where they regulate the secretion of pituitary hormones.

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13
Q

How does TRH from the PVN regulate pituitary hormone secretion?

A

TRH stimulates the anterior pituitary to release TSH, which in turn stimulates the thyroid gland to secrete thyroid hormones (T3 and T4), regulating metabolism and other physiological processes.

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14
Q

What is the role of GHRH from the ARC in pituitary hormone secretion?

A

GHRH stimulates the anterior pituitary to release GH, which promotes growth and metabolism, regulating various physiological processes such as cell reproduction and regeneration.

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15
Q

How does dopamine from hypothalamic nuclei influence pituitary hormone secretion?

A

Dopamine inhibits the secretion of prolactin from the anterior pituitary, helping maintain appropriate levels of prolactin involved in lactation and reproduction.

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16
Q

What role does the paraventricular nucleus (PVN) play in the HPA axis?

A

The PVN of the hypothalamus initiates the HPA axis response to stress by releasing corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) into the hypophyseal portal system when stress is perceived.

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17
Q

How do CRH and AVP from the hypothalamus affect the anterior pituitary?

A

CRH and AVP stimulate the anterior pituitary gland to release adrenocorticotropic hormone (ACTH) into the bloodstream, initiating the secretion of glucocorticoids from the adrenal glands in response to stress.

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18
Q

What is the primary role of cortisol in the HPA axis response?

A

Cortisol, the primary glucocorticoid released from the adrenal glands in response to ACTH stimulation, exerts widespread effects on the body, including increasing blood glucose levels, suppressing the immune system, and modulating metabolism and energy balance.

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19
Q

How does cortisol contribute to the regulation of the HPA axis?

A

Cortisol provides negative feedback to the hypothalamus and pituitary gland, inhibiting further release of CRH and ACTH, thereby regulating the stress response and maintaining homeostasis.

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20
Q

What hormone does the hypothalamus produce in the HPT axis?

A

The hypothalamus produces thyrotropin-releasing hormone (TRH) in the paraventricular nucleus (PVN) and the periventricular nucleus, releasing it into the hypophyseal portal system in response to low levels of thyroid hormones (T3 and T4) or other stimuli.

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21
Q

What is the role of TRH in the HPT axis?

A

TRH stimulates the anterior pituitary gland to release thyroid-stimulating hormone (TSH) into the bloodstream, initiating the synthesis and secretion of thyroid hormones (T3 and T4) from the thyroid gland in response to low thyroid hormone levels.

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22
Q

How does TSH affect the thyroid gland in the HPT axis?

A

TSH acts on the thyroid gland to stimulate the synthesis and secretion of thyroid hormones, primarily triiodothyronine (T3) and thyroxine (T4), which are essential for regulating metabolism, growth, and development throughout the body.

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23
Q

What role do thyroid hormones play in the HPT axis?

A

Thyroid hormones (T3 and T4) exert negative feedback on the hypothalamus and pituitary gland, inhibiting further release of TRH and TSH when thyroid hormone levels are adequate, thereby regulating the synthesis and secretion of thyroid hormones to maintain homeostasis.

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24
Q

How do glucocorticoids influence the HPT axis?

A

Glucocorticoids, such as cortisol, can modulate the hypothalamic-pituitary-thyroid (HPT) axis by affecting the synthesis, secretion, and metabolism of thyroid hormones, thereby influencing thyroid hormone levels and activity.

25
Q

What effect do thyroid hormones have on the HPA axis?

A

Thyroid hormones can affect the sensitivity of the hypothalamic-pituitary-adrenal (HPA) axis to stressors and influence the regulation of cortisol secretion, potentially modulating the body’s response to stress and its ability to maintain homeostasis in challenging situations.

26
Q

How do interactions between the HPA and HPT axes occur?

A

The HPA and HPT axes interact bidirectionally, with glucocorticoids influencing the HPT axis and thyroid hormones affecting the HPA axis. Dysregulation of either axis can impact the function of the other, leading to disorders such as hypothyroidism, hyperthyroidism, or dysregulated stress responses.

27
Q

What is the chemical structure of oxytocin?

A

Oxytocin is a nonapeptide hormone composed of nine amino acids. Its chemical structure is: Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly.

28
Q

What contributes to the stability and biological activity of oxytocin?

A

Oxytocin contains a disulfide bond between two cysteine residues, which contributes to its stability and biological activity.

29
Q

What is the chemical structure of vasopressin?

A

Vasopressin, also known as antidiuretic hormone (ADH), is a nonapeptide hormone composed of nine amino acids. Its chemical structure is: Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly.

30
Q

How does the chemical structure of vasopressin resemble that of oxytocin?

A

Like oxytocin, vasopressin contains a disulfide bond between two cysteine residues.

31
Q

What are the primary functions of oxytocin?

A

Oxytocin is primarily known for its role in stimulating uterine contractions during childbirth and facilitating milk ejection during breastfeeding. It also plays a role in promoting bonding, trust, and social behavior, earning it the nickname “love hormone” or “bonding hormone.” Additionally, oxytocin may modulate stress responses and contribute to maternal behavior and pair bonding in monogamous species.

32
Q

What are the primary functions of vasopressin?

A

Vasopressin regulates water balance and blood pressure by acting on the kidneys to promote water reabsorption and vasoconstriction. It helps regulate osmolarity and electrolyte balance in the body, particularly in response to changes in blood volume or osmotic pressure. Vasopressin also plays a role in social behavior, aggression, and memory formation, and it may be involved in modulating stress responses.

33
Q

Regulation of oxytocin and vasopressin secretion

A

Oxytocin: Regulated by neural signals (hypothalamus), influenced by uterine stretching, nipple suckling, and positive social interactions. Vasopressin: Regulated by neural and hormonal signals, influenced by blood osmolarity, volume, dehydration, low blood pressure, and stress.

34
Q

Where are neurohormones synthesized within the body?

A

Within specific neurons in the brain, notably in regions like the hypothalamus and posterior pituitary gland.

35
Q

How are neurohormones stored before their release?

A

In secretory vesicles within the neuron’s axon terminals.

36
Q

What triggers the release of neurohormones into the body?

A

Signals like neural input or changes in physiological conditions prompt the fusion of secretory vesicles.

37
Q

How do neurohormones exert their effects on target cells?

A

By binding to specific receptors on the cell membrane of target cells.

38
Q

What types of receptors do neurohormones typically bind to?

A

G-protein coupled receptors (GPCRs) or ligand-gated ion channels.

39
Q

What happens when neurohormones bind to their receptors?

A

They initiate intracellular signal transduction pathways.

40
Q

What are the main second messengers involved in GPCR signaling?

A

Cyclic adenosine monophosphate (cAMP), inositol trisphosphate (IP3), and calcium ions.

41
Q

How is neurohormone secretion regulated to maintain homeostasis?

A

Through negative feedback loops involving the hypothalamus, pituitary gland, and target endocrine glands.

42
Q

What effect do elevated levels of circulating hormones often have on further hormone secretion?

A

They inhibit further hormone secretion via feedback inhibition.

43
Q

What are some physiological effects of neurohormones?

A

Regulation of metabolism, growth, reproduction, stress responses, circadian rhythms, mood, and behavior.

44
Q

What can result from damage or dysfunction of the hypothalamus?

A

Disruption of the synthesis and release of neurohormones, leading to hormonal imbalances.

45
Q

What are some symptoms of hypothalamic dysfunction?

A

Disruptions in body temperature regulation, thirst and fluid balance, hunger and satiety signals, sleep-wake cycles, and stress responses.

46
Q

What disorders can arise from hypothalamic dysfunction?

A

Central diabetes insipidus (due to deficient vasopressin secretion), hypothalamic obesity (due to disruptions in appetite regulation), and hypothalamic hypothyroidism (due to impaired TRH secretion).

47
Q

What are pituitary adenomas?

A

Benign tumors of the pituitary gland that disrupt hormone production and secretion.

48
Q

What symptoms may arise from pituitary adenomas?

A

Symptoms depend on the hormone affected; examples include gigantism, acromegaly, amenorrhea, galactorrhea, and infertility.

49
Q

What are some examples of pituitary disorders?

A

Cushing’s disease, Nelson’s syndrome, and hypopituitarism.

50
Q

What is hyperthyroidism?

A

Excess production of thyroid hormones (T3 and T4) resulting from conditions like Graves’ disease or toxic nodular goiter.

51
Q

What causes hypothyroidism?

A

Insufficient production of thyroid hormones due to conditions like autoimmune thyroiditis (Hashimoto’s disease) or iodine deficiency.

52
Q

What are some symptoms of hyperthyroidism?

A

Weight loss, palpitations, heat intolerance, tremors, and exophthalmos (in Graves’ disease).

53
Q

What are some symptoms of hypothyroidism?

A

Fatigue, weight gain, cold intolerance, constipation, and cognitive impairment.

54
Q

What is Cushing’s syndrome?

A

Excess cortisol production leading to symptoms such as central obesity, moon face, hypertension, and insulin resistance.

55
Q

What is Addison’s disease?

A

Insufficient production of cortisol and aldosterone resulting in symptoms like fatigue, weight loss, hypotension, and hyperpigmentation.

56
Q

What characterizes central diabetes insipidus (DI)?

A

Insufficient secretion of vasopressin (ADH) from the posterior pituitary or impaired renal response to ADH.

57
Q

What characterizes nephrogenic DI?

A

Impaired renal response to ADH due to renal tubular defects, leading to symptoms similar to central DI but resistant to exogenous ADH therapy.

58
Q

What are neuroendocrine tumors?

A

Tumors arising from neuroendocrine cells producing excessive hormones, causing various endocrine-related symptoms.

59
Q

What are some examples of neuroendocrine tumors?

A

Carcinoid syndrome (serotonin-secreting tumors) and pheochromocytoma (catecholamine-secreting tumors), with symptoms like flushing and hypertension.

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