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What is the function of the endocrine system?
Regulates body functions to maintain homeostasis alongside the nervous system.
Are endocrine glands anatomically connected?
No, they are not physically connected.
Name the major endocrine glands?
Hypothalamus, pineal gland, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, thymus, ovaries, and testes.
How does the endocrine system regulate body functions?
Through hormones (chemical messengers).
How do endocrine glands release hormones?
Directly into the bloodstream (they are ductless).
How does the endocrine system differ from the nervous system?
It controls long-duration activities (e.g., growth, metabolism).
How do hormones reach their target organs?
Through the bloodstream.
What determines a hormone’s effect on a target cell?
The presence of specific receptors on the cell.
What is upregulation?
An increase in receptors due to low hormone levels.
What is downregulation?
A decrease in receptors due to high hormone levels.
What are steroid hormones derived from?
Cholesterol
Give examples of steroid hormones.
Testosterone, Estrogen, Cortisol, Aldosterone.
How do steroid hormones travel in the bloodstream?
Bound to carrier proteins.
Where do steroid hormones bind in the target cell?
Intracellular receptors (cytoplasm or nucleus).
What do steroid hormones do in the cell?
Act as transcription factors to alter gene expression.
Give examples of peptide hormones.
Insulin, Glucagon, Growth Hormone, ADH, TSH.
How do peptide hormones travel in the bloodstream?
Freely dissolved in plasma (no carrier required).
Where do peptide hormones bind?
Cell membrane receptors.
How do peptide hormones exert their effects?
Through second messenger systems (e.g., cAMP, IP3, DAG).
Name two types of peptide hormone receptors
G-Protein Coupled Receptors (GPCRs) and Enzyme-Linked Receptors.
What are two types of amine hormones?
Thyroid hormones (T3 & T4) and Catecholamines (Epinephrine, Norepinephrine).
How do thyroid hormones act?
Like steroid hormones, binding intracellular receptors.
How do catecholamines act?
Through GPCRs.
What three factors affect hormone levels?
Secretion, Degradation, and Excretion.
How do hormones influence the body?
By changing enzyme activity or membrane transport rates.
Do hormones act at high or low concentrations?
Low concentrations but with significant effects.
What is the function of the hypothalamus?
Links the endocrine and nervous systems.
How is the hypothalamus connected to the pituitary gland?
Through the infundibulum (pituitary stalk).
What are the two lobes of the pituitary gland?
Anterior pituitary (glandular) and Posterior pituitary (neural tissue).
How does the hypothalamus regulate the pituitary gland?
Through releasing/inhibiting hormones.
What does Corticotropin-Releasing Hormone (CRH) do?
Stimulates ACTH release.
What does Gonadotropin-Releasing Hormone (GnRH) do?
Stimulates FSH & LH release.
What does Thyrotropin-Releasing Hormone (TRH) do?
Stimulates TSH release.
What does Growth Hormone-Releasing Hormone (GHRH) do?
Stimulates GH release.
What does Somatostatin (GH-inhibiting hormone) do?
Inhibits GH release.
What does Prolactin-Inhibiting Hormone (PIH/Dopamine) do?
Inhibits Prolactin release.
What does Adrenocorticotropic Hormone (ACTH) target?
The adrenal cortex.
What does Thyroid-Stimulating Hormone (TSH) target?
The thyroid gland.
What does Follicle-Stimulating Hormone (FSH) target?
Ovaries/Testes (stimulates egg/sperm production).
What does Luteinizing Hormone (LH) target?
Ovaries/Testes (stimulates ovulation & testosterone production).
What does Growth Hormone (GH) do?
Promotes growth & metabolism.
What does Prolactin (PRL) do?
Stimulates milk production.
Where are posterior pituitary hormones made?
In the hypothalamus.
What does Antidiuretic Hormone (ADH) do?
Regulates water balance in the kidneys.
What does Oxytocin (OT) do?
Stimulates uterine contractions & milk ejection.
What is negative feedback?
High hormone levels inhibit further secretion.
What is positive feedback?
High hormone levels stimulate more secretion.
Give an example of negative feedback.
High T3/T4 inhibits TRH & TSH release.
Give an example of positive feedback.
Oxytocin during childbirth increases contractions.
What does the thyroid gland produce?
T3 & T4 (metabolism) and Calcitonin (lowers blood calcium).
What does the parathyroid gland produce?
Parathyroid Hormone (PTH) (increases blood calcium).
What does the adrenal cortex produce?
Aldosterone (salt/water balance) and Cortisol (stress response).
What does the pancreas produce?
Insulin (lowers blood glucose) and Glucagon (raises blood glucose).
What hormones do the ovaries produce?
Estrogen (female reproduction) and Progesterone (pregnancy regulation).
What hormone do the testes produce?
Testosterone (male reproduction).
What does the pineal gland produce?
Melatonin (regulates sleep cycles).
