Endocrine Physiology

Question 1

What are the main endocrine organs?

Answer 1

-Hypothalamus -Pituitary Gland -Pineal Gland -Thyroid Gland -Parathyroid Glands -Thymus -Adrenal Glands -Pancreas -Ovary -Testes -Fat tissue

Question 2

Functions of the endocrine system

Answer 2

-Growth and development -sex differentiation -metabolism -adaptation to an ever changing environment –regulate digestion –use and store nutrients –electrolyte and water metab –Reproductive functions

Question 3

What are the types of hypothalamic neurons?

Answer 3

• Autonomic neuron: autonomic neuron>>preganglionic neuron>>post ganglionic neuron>>pancreatic islet cells(OR adrenal gland)>>hormone - Magnocellular neurosecretory neuron: neurosecretory neuron synapses directly into posterior pituitary releasing hormones (OXY and ADH) - Parvocellular neurosecretory neuron: neurosecretory neuron releases hormone directly into hypophyseal portal circulation that acts on anterior pituitary lobe.

Question 4

Hormones: -function as ____. -paracrine or autocrine? -what is their goal?

Answer 4

-function as chemical messengers -they are both paracrine and autocrine! -the goal of hormones is to signal amplification! (amplify its message)

Question 5

A single hormone can exert various effects in different tissues, True or False? One single function can be regulated by several hormones, True or False?

Answer 5

-TRUE!!! a single hormone can exert various effects in different tissues -TRUE! a single function can be regulated by several hormones.

Question 6

Explain the process of each of the following forms of intercellular communication -Endocrine -Neuroendocrine -Paracrine -Autocrine

Answer 6

Endocrine: -Cell releases hormone that travels through the blood and acts on a target cell. Neuroendocrine: -Neuron releases hormone that travels through the blood and acts on target cell. Paracrine: -Cell releases a hormone that travels through the interstitial fluid to act on a nearby target cell. Autocrine: -cell releases hormone into the interstitial fluid that acts on itselt. (Like Tcells)

Question 7

Explain how Water Soluble Hormone gets into the cell to elicit is effects.

Answer 7

-water soluble hormone(first messenger) must bind to a receptor on cell wall membrane thereby activating G-protein(transducer)>>adenyl cyclase (effector)>>cAMP(second messenger)>>target cell response.

Question 8

Explain how Fat soluble Hormone gets into the cell to elicit its effects.

Answer 8

Since the hormone is lipophillic it can pass directly through the cell wall whereby it binds to a receptor in the cytoplasm allowing its entrance in the nucleus. Once in the nucleus it exhibits its effects on DNA production & therefore new protein production.

Question 9

What factors affect the response of a target cell to a hormone?

Answer 9

-Level of the hormone in the blood -Relative number of receptors on target cell. –up-regulation: number of receptors on the cell wall are increased. will have greater response. –down-regulation: number of receptors on the cell wall are decreased, will have decreased response. -Affinity of the receptors for hormones (ex. pH of body fluids plays a role in the affinity of insulin receptors.)

Question 10

Describe the mechanism of action of the following: -humoral secretion of hormone -neural secretion of hormone -Hormonal release of hormones

Answer 10

Humoral: -capillary blood contains low levels of Ca2+ which stimulate the parathyroid glands to release PTH (hormone) Neural: -Preganglionic fiber stimulate adrenal medulla cells leading to the release of catecholamines into the blood. Hormonal: -hypothalamus secretes hormones that stimulate the anterior pituitary to secrete hormones that act on various endocrine organs (such as thyroid, adrenal cortex, gonads) which secrete effector hormones.

Question 11

How are Hormone Levels controlled/maintained?

Answer 11

-Hormone levels fluctuate with sleep-wake cycle (GH and ACTH) -Secreted in cyclic manner (Female sex hormones) -Regulated by feedback mechanisms that monitor substances such as glucose (insulin) and water (ADH) in the body -Regulated by feedback mechanisms that involve the hypothalamic-pituitary-target system

Question 12

What is diurnal secretion and which hormone follows this pattern?

Answer 12

-diurnal= once every 24hrs -glucocorticoid secretion follows a diurnal patter, peak glucocorticoid levels are present sometime between 8 & 9 AM.

Question 13

What are the Peptide & Protein Hormones and what tissue/gland are they secreted from?

Answer 13

• Hypothalamus: TRH (thyrotropin releasing hormone), GnRH (Gonadotropin releasing hormone), CRH (corticotropic releasing hormone) , GHRH (growth hormone releasing hormone), Somatostatin [inhibits stomatomedin (which increases GH)] *basically stomatostatin inhibits GH.
• Anterior Pituitary: ACTH, TSH, FSH, LH, PRL, GH
• Posterior Pituitary: oxytocin, ADH
• Thyroid: Calcitonin
• Pancreas: Glugacon, insulin, somatostatin
• Liver: Somatomedin
• Parathyroid: PTH
• Placenta: HCG, HCS, HPL
• Kidney: Renin
• Heart: ANP
• GI: Gastrin, CCK, Secretin, GIP, Somatostatin, GLP
• Adipocyte: Leptin

Question 15

What are the two groups of hormones derived from the amino acid Tyrosine?

Answer 15

Thyroid Hormones (T3 and T4)

Catecholamines (NE and E)

Question 16

Describe the formation of insulin

Answer 16

Preproinsulin>>signal sequence removed>>proinsulin>> connecting chain removed>>insulin

Question 17

Is adipose tissue an endorcrine organ? why or why not?

Answer 17

Adipose tissue is an endocrine organ, it secretes many adipokines; one of which is leptin.

Question 18

How do hypothalmic releasing hormones reach their final targets?

Answer 18

Hormones from the hypothalamus that intend on traveling to the anterior pituitary are relased into the hypophyseal portal system before reaching the anterior pituitary.

Hormones from the hypothalamus that intend on traveling to the posterior pituitary have longer neurons that synapse directly into the posterior pituitary where then the hormone is released.

Question 19

What are the five cell types of the anterior pituitary gland?

Answer 19

Thyrotrophs: produce thyrotropin, also called TSH (Thyroid Stimulating Hormone)

Corticotrophs: produce corticotrophin, also called adrenocorticotropic hormone (ACTH)

Gonadotrophs: produce gonadotropins; LH and FSH

Somatotrophs: produce growth hormone

Lactotrophs: Produce prolactin

Question 20

Describe the levels and process of Hormone secretion and its feedback mechanisms

Answer 20

CNS input>>Hypothalamus>>>releasing hormone sent to Anterior pituitary.

Anterior pituitary releases tropic hormone that travels to target gland which thereby secretes its hormone to act on its target cell eliciting a physiologic effect.

The hormone secreted by the target gland has negative feedback effects at both the level of the pituitary and the hypothalamus.

Question 21

Describe the Thyroid Hormone feedback mechanisms

Answer 21

Hypothalamus secretes Thyrotrophic Releaseing Hormone that travels to the Anterior Pituitary and signals it to release Thyroid Stimulating Hormone which then travels through the blood to its target the thyroid. The thyroid then releases its thyroid hormones to enact on its target cells. The thyroid hormones have negative feedback at both the level of the pituitary and the hypothalamus.

Question 22

Describe the feedback loops of Glucocorticoids

Answer 22

Hypothalamus releases Corticotrophic Releasing hormone to the anterior pituitary(AP), stimulating the AP to release ACTH into the blood and travels to the adrenal cortex. The adrenal cortex then releases Glucocorticoids that then work on their target cell to induce a physiologic effect. The release of glucocorticoids has a negative feedback effect at both the level of the AP and the hypothalamus

Question 23

Describe the Feedback loops of LH, FSH, and Testosterone

Answer 23

Hypothalamus releases GnRH to act on the AP, the AP releases LH, FSH, into the blood to enact on the ovaries/testes. This induced the ovaries/testes to release progesterone, estrogen, and testosterone(LH) to act on its target cells, these hormones have negative feedback loops at both the level of the AP and hypothalamus.

*testis produces inhibin which inhibits FSH at the level of the AP.

Question 24

Parturition Feedback loops

Answer 24

Oxytocin released from posterior pituitary inducing uterine contraction and the release of Progesterone that increases uterine contractions leading to increased stretch and increased release of oxytocin.

The release of oxytocin inhibits the inhibiting effects of Prostaglandins in uterine contraction.