Module 06 AI

Endocrine system function :

Uses hormones in the blood to regulate body processes like growth, metabolism, reproduction, and homeostasis

Endocrine vs nervous system :

Endocrine = slow, long-lasting, widespread; Nervous = fast, short, specific

Hormones :

Chemical messengers released into blood to affect distant target cells

Major endocrine organs :

Pituitary, thyroid, parathyroid, adrenal glands, pineal gland, pancreas, gonads

Hypothalamus :

Neuroendocrine organ that links nervous and endocrine systems

Endocrine signaling :

Hormones travel long distances through blood

Paracrine signaling :

Signals act on nearby cells

Autocrine signaling :

Signals act on the same cell

Juxtacrine signaling :

Direct contact between cells

Endocrine vs exocrine :

Endocrine = ductless, hormones into blood; Exocrine = ducts, secretions to surface

Hormonal vs neural signaling :

Hormonal = slow, long-lasting, widespread; Neural = fast, short, targeted

Peptide/protein hormones :

Water-soluble, stored in vesicles, bind membrane receptors

Steroid hormones :

Lipid-soluble, derived from cholesterol, bind intracellular receptors

Amine hormones :

Derived from amino acids (e.g., epinephrine, thyroid hormone)

Water-soluble hormone action :

Use second messengers (like cAMP)

Lipid-soluble hormone action :

Direct gene activation

Second messenger system :

Intracellular signaling cascade that amplifies hormone effects

Signal amplification :

One hormone can trigger millions of intracellular responses

Hormone transport proteins :

Increase half-life and create a reservoir of hormone

Hormone regulation :

Controlled by negative feedback loops

Humoral :

Ion/nutrient levels

Neural :

Nerve signals

Hormonal :

Other hormones

Target cell activation factors :

Hormone concentration, Number of receptors, Binding affinity

Negative feedback :

Hormone output reduces original stimulus

Hypersecretion :

Too much hormone → exaggerated response

Hyposecretion :

Too little hormone → reduced response

Up-regulation :

Increase receptors → more sensitivity

Down-regulation :

Decrease receptors → less sensitivity

Hypothalamus location :

Brain region controlling pituitary

Anterior pituitary :

Glandular tissue, produces hormones

Posterior pituitary :

Neural tissue, stores/releases hormones

Posterior pituitary hormones :

ADH, Oxytocin

ADH :

Water retention

Oxytocin :

Labor + milk ejection

Anterior pituitary hormones :

GH, TSH, ACTH, FSH, LH, PRL

Hypophyseal portal system :

Blood connection delivering hypothalamic hormones to anterior pituitary

Long-loop feedback :

Target gland hormones inhibit hypothalamus/pituitary

Short-loop feedback :

Pituitary hormones inhibit hypothalamus

Primary disorder :

Problem in target gland

Secondary disorder :

Problem in pituitary

Tertiary disorder :

Problem in hypothalamus

Thyroid Location :

Anterior neck

Thyroid follicle :

Functional unit containing colloid (thyroglobulin + iodine)

Thyroid hormones (T3, T4) :

Increase metabolism, heat production, growth

Thyroid Control pathway :

TRH → TSH → Thyroid hormones

Thyroid-binding globulin (TBG) :

Transports thyroid hormones in blood

Hyperthyroidism :

Increased metabolism, weight loss

Hypothyroidism :

Decreased metabolism, weight gain

Parathyroid Location :

Posterior thyroid

Parathyroid Hormone :

PTH (parathyroid hormone)

Parathyroid Function :

Raises blood calcium levels

Parathyroid Targets :

Bone → increases resorption, Kidneys → reabsorb Ca²⁺, Intestines → increase absorption (via calcitriol)

Parathyroid Regulation :

Low Ca²⁺ stimulates PTH release

Hyperparathyroidism :

Hypoparathyroidism :

Low calcium, muscle spasms

Adrenal cortex zones :

Zona glomerulosa, Zona fasciculata, Zona reticularis

Zona glomerulosa →

aldosterone

Zona fasciculata →

cortisol

Zona reticularis →

androgens

Adrenal Gland Steroid hormones :

Derived from cholesterol

Adrenal Gland Cortisol control :

CRH → ACTH → cortisol

Cortisol function :

Stress response, increases blood glucose

Addison’s disease :

Low cortisol

Cushing’s disease :

High cortisol

Adrenal medulla hormones :

Epinephrine, norepinephrine (catecholamines)

Catecholamine function :

Fight-or-flight response

Pineal gland :

Produces melatonin (sleep cycles)

Pancreas :

Insulin, Glucagon, Somatostatin

Insulin →

lowers blood glucose

Glucagon →

raises blood glucose

Somatostatin →

inhibits both

Type 1 diabetes :

No insulin production

Type 2 diabetes :

Insulin resistance

Heart →

ANP

Kidney →

EPO

Skin →

Vitamin D

Adipose →

leptin

Diabetes insipidus :

Low ADH → excessive urination

Addison’s disease :

Low cortisol → fatigue, low BP

Cushing’s disease :

High cortisol → weight gain, hyperglycemia

Hyperthyroidism :

High metabolism

Hypothyroidism :

Low metabolism

Hyperparathyroidism :

High calcium

Hypoparathyroidism :

Low calcium

Reproductive system function :

Produce gametes, fertilization, support fetus

Male gonads :

Testes → produce sperm + testosterone

Female gonads :

Ovaries → produce ova + estrogen/progesterone

H P G axis :

GnRH → FSH & LH → gonads → sex hormones

FSH :

Males → sperm production; Females → follicle development

LH :

Males → testosterone production; Females → ovulation

Estrogen :

Female secondary sex characteristics, cycle regulation

Progesterone :

Maintains uterine lining

Testosterone :

Male characteristics, sperm production

Inhibin :

Inhibits FSH release