Endocrine and Digestive Systems: ANP College Study Guide

Introduction to the Endocrine System

Overview of Regulatory Systems

The human body uses two main regulatory systems to maintain homeostasis: the nervous system and the endocrine system. These systems communicate via 'input' and 'output' messages to coordinate bodily functions.

• Nervous System: Uses electrical impulses for rapid, short-term responses.

• Endocrine System: Uses hormones for slower, long-term regulation.

Regulatory Feedback Mechanisms

• Negative Feedback: A change in one direction results in a response that causes a change in the opposite direction, stabilizing physiological functions. Example: Regulation of blood glucose levels by insulin.

• Positive Feedback: A change in one direction causes further change in the same direction, amplifying the response. Example: Oxytocin release during childbirth.

Endocrine System Structure and Function

Endocrine vs. Exocrine Glands

• Endocrine Glands: Release hormones directly into the bloodstream.

• Exocrine Glands: Release products via ducts to the exterior or into body cavities.

Major Endocrine Organs

• Pituitary Gland

• Thyroid Gland

• Parathyroid Glands

• Adrenal Glands

• Pancreas

• Gonads (Ovaries and Testes)

• Pineal Gland

• Thymus

Hormones: Types and Actions

Types of Hormones

• Amino Acid-Based Hormones: Include proteins, peptides, and amines.

• Steroid Hormones: Derived from cholesterol; include sex hormones and adrenal cortex hormones.

Mechanisms of Hormone Action

Hormones act by binding to specific receptors on target cells, causing changes such as:

• Altering membrane permeability

• Stimulating synthesis of proteins or enzymes

• Activating or deactivating enzymes

• Inducing secretory activity

• Stimulating mitosis

Endocrine Glands and Their Hormones

Pituitary Gland

• Anterior Pituitary: Produces hormones such as growth hormone (GH), prolactin, ACTH, TSH, FSH, and LH.

• Posterior Pituitary: Stores and releases oxytocin and antidiuretic hormone (ADH).

Thyroid Gland

• Produces thyroid hormones (T3 and T4) that regulate metabolism.

• Produces calcitonin, which lowers blood calcium levels.

Parathyroid Glands

• Produce parathyroid hormone (PTH), which increases blood calcium levels.

Adrenal Glands

• Adrenal Cortex: Produces corticosteroids (mineralocorticoids, glucocorticoids, and gonadocorticoids).

• Adrenal Medulla: Produces epinephrine and norepinephrine for the 'fight or flight' response.

Pancreas

• Produces insulin (lowers blood glucose) and glucagon (raises blood glucose).

Gonads

• Ovaries: Produce estrogen and progesterone.

• Testes: Produce testosterone.

Pineal Gland

• Produces melatonin, which regulates sleep-wake cycles.

Thymus

• Produces thymosin, important for T-cell development in the immune system.

Digestive System Overview

Functions of the Digestive System

The digestive system is responsible for breaking down food, absorbing nutrients, and eliminating waste.

• Ingestion: Taking in food.

• Digestion: Mechanical and chemical breakdown of food.

• Absorption: Uptake of nutrients into the blood.

• Defecation: Elimination of indigestible substances.

Digestive Tract Anatomy

• Alimentary Canal: Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus.

• Accessory Organs: Salivary glands, liver, pancreas.

Digestive Processes

• Propulsion: Movement of food through the tract via peristalsis.

• Mechanical Digestion: Chewing, mixing, and churning food.

• Chemical Digestion: Enzymatic breakdown of food.

• Absorption: Passage of nutrients into blood or lymph.

• Defecation: Elimination of waste.

Metabolism and Energy Balance

Metabolic Pathways

Metabolism refers to all chemical reactions in the body, including catabolism (breakdown) and anabolism (synthesis).

• Cellular Respiration: Process by which cells produce ATP from glucose.

• Glycolysis: First step in glucose metabolism, occurs in the cytoplasm.

• Krebs Cycle: Occurs in mitochondria, produces ATP, NADH, and FADH2.

• Electron Transport Chain: Final step, produces most ATP.

Equation for Cellular Respiration: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$

Summary Table: Major Endocrine Glands and Their Hormones

Gland	Hormone(s)	Main Function
Pituitary	GH, TSH, ACTH, FSH, LH, PRL, ADH, Oxytocin	Growth, metabolism, reproduction, water balance
Thyroid	T3, T4, Calcitonin	Metabolism, calcium regulation
Parathyroid	PTH	Calcium regulation
Adrenal	Cortisol, Aldosterone, Epinephrine, Norepinephrine	Stress response, metabolism, water balance
Pancreas	Insulin, Glucagon	Blood glucose regulation
Gonads	Estrogen, Progesterone, Testosterone	Reproduction, sexual characteristics
Pineal	Melatonin	Sleep-wake cycle
Thymus	Thymosin	Immune function

Relevant Images