ENDOCRINE SYSTEM
Key Notes
🔹 Endocrine vs. Nervous System
Endocrine: Uses hormones to signal distant targets via blood; responses are
slower but longer lasting.
Nervous: Uses electrical signals and neurotransmitters; fast and short-term
effects.
🔹 Types of Glands
Exocrine: Releases substances through ducts (e.g., sweat, saliva, digestive
juices).
Endocrine: Release hormones directly into the blood (e.g., pituitary,
thyroid).
o Some organs (like the pancreas, ovaries, and liver) have both
endocrine and non-endocrine functions.
🔹 Functions of Hormones
Regulate body fluids, metabolism, biological rhythms, muscle contractions,
and immune responses.
Control growth, development, and reproductive processes.
🔹 Hormone-Receptor Interaction
Hormones act only on cells with matching receptors.
Receptor levels can increase (up-regulation) or decrease (down-regulation)
depending on hormone levels.
🔹 Types of Hormones
, Lipid-Soluble (e.g., steroid, thyroid hormones): Enter cells and influence
gene expression.
Water-Soluble (e.g., proteins, amines): Bind to cell surface and trigger
second messenger pathways.
🔹 Hormone Action Depends On:
1. Hormone concentration
2. Number of receptors
3. Interaction with other hormones (synergistic or antagonistic)
🔹 Regulation of Hormone Secretion
Controlled by nervous signals, blood chemical changes, or other hormones.
Negative feedback is most common; positive feedback is rare but occurs in
specific cases (e.g., childbirth).
Major Endocrine Organs and Hormones
🧠 Hypothalamus & Pituitary Gland
Hypothalamus: Controls pituitary activity via regulatory hormones.
Pituitary Gland:
o Anterior Lobe (produces hormones)
hGH: Stimulates tissue growth and metabolism.
TSH: Stimulates thyroid hormone production.
FSH/LH: Regulate reproductive functions.
PRL: Promotes milk production.
ACTH: Stimulates adrenal cortex to release cortisol.
Key Notes
🔹 Endocrine vs. Nervous System
Endocrine: Uses hormones to signal distant targets via blood; responses are
slower but longer lasting.
Nervous: Uses electrical signals and neurotransmitters; fast and short-term
effects.
🔹 Types of Glands
Exocrine: Releases substances through ducts (e.g., sweat, saliva, digestive
juices).
Endocrine: Release hormones directly into the blood (e.g., pituitary,
thyroid).
o Some organs (like the pancreas, ovaries, and liver) have both
endocrine and non-endocrine functions.
🔹 Functions of Hormones
Regulate body fluids, metabolism, biological rhythms, muscle contractions,
and immune responses.
Control growth, development, and reproductive processes.
🔹 Hormone-Receptor Interaction
Hormones act only on cells with matching receptors.
Receptor levels can increase (up-regulation) or decrease (down-regulation)
depending on hormone levels.
🔹 Types of Hormones
, Lipid-Soluble (e.g., steroid, thyroid hormones): Enter cells and influence
gene expression.
Water-Soluble (e.g., proteins, amines): Bind to cell surface and trigger
second messenger pathways.
🔹 Hormone Action Depends On:
1. Hormone concentration
2. Number of receptors
3. Interaction with other hormones (synergistic or antagonistic)
🔹 Regulation of Hormone Secretion
Controlled by nervous signals, blood chemical changes, or other hormones.
Negative feedback is most common; positive feedback is rare but occurs in
specific cases (e.g., childbirth).
Major Endocrine Organs and Hormones
🧠 Hypothalamus & Pituitary Gland
Hypothalamus: Controls pituitary activity via regulatory hormones.
Pituitary Gland:
o Anterior Lobe (produces hormones)
hGH: Stimulates tissue growth and metabolism.
TSH: Stimulates thyroid hormone production.
FSH/LH: Regulate reproductive functions.
PRL: Promotes milk production.
ACTH: Stimulates adrenal cortex to release cortisol.
