Term
| How are hormones secreted? |
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Definition
Ductless endocrine glands release hormones into the circulation.
- Chemical messengers |
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Term
| Describe the difference between endocrine and exocrine glands. |
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Definition
Exocrine: secretions enter ducts from where they either exit the body or connect to the lumne of a structure such as the intestines or the surface of the skin.
- Endocrine glands secrete hormones that enter the interstitial fluid and diffused into the blood, from where they can reach distant target cells. |
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Term
| Name 5 things hormones regulate. |
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Definition
- Basal metabolism: Thyroid hormone
- Extracellular fluid composition: ADH, Aldosterone
- Stress and critical illness: cortisol
- Energy production: insulin
- Reproduction: Estrogen and testosterone
- Uterine contractions: oxytocin
- Milk production: prolactin
- Growth and development: growth hormone and thyroid hormone |
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Term
| Describe the general mechanism of hormones. |
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Definition
1) Endocrine gland secretes hormone into circulatory system
2) Hormone binds with receptor on target cell
3) Binding of hormone triggers:
- Altered channel permeability due to pre-existing channel-forming proteins
- Second messenger system to alter existing protein activity
- Activate specific genes to create new proteins. |
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Term
| Types of hormones & their characteristics |
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Definition
- Peptide: water-soluble, binds to cell surface receptors. (Insulin)
- Amine: lipid-soluble, can travel to nucleus.
- Steroid: derived from cholesterol. Lipid-soluble, can pass to nucleus. (Testosterone) |
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Term
| Peptides vs steroid hormones |
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Definition
- Major form: free (peptide) vs protein-bound (steroid)
- Receptor locations: plasma membrane (peptide) vs. intracellular (steroid)
- Most common signalling:
1) Second messenger, 2) enzyme activation by receptor, 3) intrinsic enzymatic activity of receptor (peptide) vs. intracellular receptors directly alter gene transcription (steroid)
- Rate of excretion/metabolism: fast, minutes (peptides) vs. slow, hrs to days (steroid) |
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Term
| Possible fates of a hormone |
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Definition
After circulating in blood:
1) excreted in urine/feces
2) inactivated by metabolism
3) activated by metabolism and bind to target cells
4) go directly to target cells |
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Term
| Describe the regulators of hormone secretion |
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Definition
1) Ions/nutrients
- Major function of hormone is to regulate ion/nutrient plasma concentration by negative feedback (Glucose & Insulin, Ca & parathyroid hormone)
2) Neurotransmitters
- Adrenal medulla controlled by preganglionic fibers (parasympathetic and sympathetic)
3) Hormones
- Secretion of one hormone is indirectly controlled by blood concentration of other hormone
- TROPHIC HORMONE = a hormone that stimulates the secretion of another hormone |
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Term
| Describe how neurons regulate the endocrine system |
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Definition
Autonomic nervous:
1) Adrenal medulla stimulates epinephrine
2) Autonomic ganglion stimulates/inhibits endocrine gland cells
Hypothalamus:
3) Posterior pituitary neurons secrete hormones
4) Hypothalamic hormones stimulate/inhibit anterior pituitary which releases hormones |
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Term
| Anterior Pituitary Hormones |
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Definition
Hypothalamus releases hormones, which go to anterior pituitary where 2nd hormones are produced. 2nd hormones go to target endocrine glands where 3rd hormones secreted.
Stimulating:
1) GnRH released in hypothalamus -> LH & FSH released in anterior pituitary -> LH & FSH act on gonads to secrete testosterone (males) and estradiol & progesterone (females)
2) GHRH (Hypothalamus) -> stimulates GH (growth hormone) release in anterior pituitary -> IGF-1 secretion in liver; protein synthesis, carb & lipid metabolism in other organs and tissues
4) TRH (Thyrotropin-releasing hormone) -> TSH released in anterior pituitary -> thyroid secretes thyroxine
5) CRH (Corticotropin-releasing hormone) -> ACTH released in anterior pituitary -> Adrenal cortex releases cortisol
Inhibiting:
1) SS (Somatostatin) -> inhibits GH
2) DA (Dopamine) -> inhibits prolactin release -> inhibits breast development and milk production |
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Term
| Connections between hypothalamus and pituitary gland |
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Definition
Neural and vascular connections between hypothalamus and pituitary gland
- Paraventricular and supraoptic nuclei travel down INFUNDIBULUM (bridge) to end in posterior pituitary
- Blood supply to anterior pitutiary comes via vessels in median eminence
Hormone secretion by anterior pituitary controlled by hypothalamic hormones reaching the anterior via hypothalamo-pituitary portal vessels -> venous outflow to heart. |
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Term
| What are hypophysiotropic hormones? |
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Definition
| the hypothalamic hormones that regulate anterior pituitary gland function |
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Term
| Pathway of hormone to affect thyroid gland |
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Definition
1) Hypothalamus releases TRH (Thyroid-releasing hormone)
2) TRH stimulates TSH (Thyroid-stimulating hormone) secretion in anterior pituitary
3) TSH goes to thyroid to secrete thyroxine (T4) and triiodothyronine (T3). |
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Term
| Composition of Thyroid Gland |
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Definition
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