Key Takeaways
- The nervous system is divided into CNS (brain + spinal cord) and PNS (nerves throughout the body)
- Neurons transmit electrical impulses; the three parts are dendrites (receive), cell body (process), axon (transmit)
- The digestive system breaks down food mechanically and chemically, absorbing nutrients and eliminating waste
- Digestive pathway: mouth → esophagus → stomach → small intestine → large intestine → rectum → anus
- Most nutrient absorption occurs in the small intestine; most water absorption in the large intestine
- The endocrine system uses hormones to regulate growth, metabolism, reproduction, and homeostasis
- Key endocrine glands: pituitary (master gland), thyroid (metabolism), pancreas (blood sugar), adrenals (stress response)
- The urinary system (kidneys, ureters, bladder, urethra) filters blood, removes waste, and regulates fluid/electrolyte balance
- The kidneys produce urine by filtering blood — they process about 180 liters per day but produce only 1-2 liters of urine
Nervous, Digestive & Other Body Systems
The Nervous System
The nervous system is the body's communication network, controlling and coordinating all body functions.
Divisions
| Division | Components | Function |
|---|---|---|
| Central Nervous System (CNS) | Brain + Spinal Cord | Integration and processing center |
| Peripheral Nervous System (PNS) | Cranial and spinal nerves | Carries signals to/from CNS |
PNS subdivisions:
- Somatic (voluntary): Controls skeletal muscles; conscious movement
- Autonomic (involuntary): Controls organs, glands, smooth muscle
- Sympathetic: "Fight or flight" — increases heart rate, dilates pupils, diverts blood to muscles
- Parasympathetic: "Rest and digest" — decreases heart rate, stimulates digestion
Neurons
| Part | Function |
|---|---|
| Dendrites | Receive signals from other neurons |
| Cell body (soma) | Contains the nucleus; processes signals |
| Axon | Transmits electrical impulse away from cell body |
| Myelin sheath | Insulates axon; speeds up signal transmission |
| Synapse | Gap between neurons where neurotransmitters are released |
Major Brain Regions
| Region | Function |
|---|---|
| Cerebrum | Higher thought, memory, language, sensory processing, voluntary movement |
| Cerebellum | Coordination, balance, fine motor control |
| Brain stem | Basic life functions: breathing, heart rate, blood pressure, consciousness |
| Hypothalamus | Homeostasis: body temperature, hunger, thirst, sleep, hormone regulation |
| Thalamus | Relay station: routes sensory information to appropriate brain areas |
The Digestive System
The digestive system breaks down food into nutrients the body can absorb and use.
Digestive Pathway
| Organ | Function | Type of Digestion |
|---|---|---|
| Mouth | Chewing breaks food; saliva contains amylase (starch digestion) | Mechanical + Chemical |
| Esophagus | Transports food via peristalsis (wave-like contractions) | Mechanical |
| Stomach | Churns food; HCl and pepsin break down proteins | Mechanical + Chemical |
| Small Intestine | Primary site of nutrient absorption; uses bile and pancreatic enzymes | Chemical + Absorption |
| Large Intestine (Colon) | Absorbs water and electrolytes; forms feces | Absorption |
| Rectum/Anus | Stores and eliminates feces | Elimination |
Accessory Organs
| Organ | Role in Digestion |
|---|---|
| Liver | Produces bile (emulsifies fats); detoxifies blood; stores glycogen |
| Gallbladder | Stores and concentrates bile; releases it into small intestine |
| Pancreas | Produces digestive enzymes + bicarbonate; also produces insulin (endocrine) |
Three sections of the small intestine:
- Duodenum: Receives chyme from stomach + bile + pancreatic juice
- Jejunum: Primary site of nutrient absorption
- Ileum: Absorbs B12 and bile salts; connects to large intestine
The Endocrine System
The endocrine system uses hormones (chemical messengers) released into the bloodstream to regulate body functions.
| Gland | Key Hormones | Function |
|---|---|---|
| Pituitary (master gland) | Growth hormone, TSH, ACTH, ADH, oxytocin | Controls other glands; growth; water balance |
| Thyroid | T3, T4, calcitonin | Regulates metabolism; lowers blood calcium |
| Parathyroid | PTH (parathyroid hormone) | Raises blood calcium levels |
| Adrenal | Cortisol, aldosterone, epinephrine | Stress response; blood pressure; electrolytes |
| Pancreas | Insulin, glucagon | Regulates blood glucose |
| Ovaries | Estrogen, progesterone | Female reproduction |
| Testes | Testosterone | Male reproduction |
Blood glucose regulation:
- Insulin (from beta cells): Lowers blood glucose by promoting glucose uptake into cells
- Glucagon (from alpha cells): Raises blood glucose by promoting glycogen breakdown in the liver
The Urinary System
| Structure | Function |
|---|---|
| Kidneys (2) | Filter blood; produce urine; regulate fluid, electrolytes, and pH |
| Ureters (2) | Transport urine from kidneys to bladder |
| Bladder | Stores urine (capacity ~500 mL) |
| Urethra | Eliminates urine from the body |
The nephron is the functional unit of the kidney:
- Each kidney contains about 1 million nephrons
- Nephrons filter blood, reabsorb useful substances, and secrete waste
- The kidneys process ~180 L of blood daily but produce only 1-2 L of urine (99% is reabsorbed)
Which division of the autonomic nervous system is responsible for the "fight or flight" response?
Where does MOST nutrient absorption occur in the digestive system?
Which hormone LOWERS blood glucose levels?
What is the functional unit of the kidney?
Arrange the organs of the digestive tract in the correct order food travels through them.
Arrange the items in the correct order
Match each endocrine gland to its primary function.
Match each item on the left with the correct item on the right
Which part of the brain controls basic life functions such as breathing and heart rate?
The liver produces _____, which is stored in the gallbladder and helps emulsify (break down) fats.
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Which of the following are functions of the kidneys? (Select all that apply)
Select all that apply
Neurons transmit electrical impulses along a long, thin fiber called the:
The primary function of the large intestine is to:
Which gland is often referred to as the "master gland" because it controls the function of other endocrine glands?
The part of a neuron that receives signals from other neurons is called the _____.
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