Animal's regulation

Animal's regulation, including human, explained in a NUTshell!

Cell Specialisation

• Multicellular organisms have different cell types.

• Each type performs a specific function.

• Specialised cells → tissues → organs → systems.

Human Digestive System: Function

• Breaks down food into molecules.

• Molecules pass into bloodstream & through cell membranes.

• Provides nutrients (e.g. glucose) for energy.

• Lego car: the digestive system breaks down the lego house into bricks and the cells builds a lego car or something else that is different

What Gets Digested?

Macromolecule	Breaks Down Into	Location	Enzyme
Protein	Amino acids	Small intestine, Stomach	Proteases
Carbohydrate	Glucose / Monosaccharides	Mouth & Small intestine	Amylase
Lipids	Fatty acids & Glycerol / Monoglycerides	Small intestine	Lipases

Types of Digestion / Process

• Mechanical: Mouth (chewing), Stomach (churning) → smaller pieces, ↑ SA:V.

• Chemical: Mouth, Stomach, Small Intestine (uses enzymes and acids) break food into simplest molecules.

• Enzymes
  → Speed up chemical reactions

• 4 Phases of Food Processing

  1. Ingestion → 2. Digestion → 3. Absorption → 4. Elimination/Excretion/Egestion

Digestive System: Organs

• Main organs (food passes through): Mouth, Esophagus, Stomach, Small Intestine, Large Intestine, Rectum, Anus

• Accessory organs (no food pass): Pancreas, Liver, Gallbladder

• *Esophagus Transit Time
  → 4–10 seconds via peristalsis (muscle movement)

• *Pathway of Food
  → Mouth → Esophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus

Digestion in Mouth

• Teeth: Chewing → mechanical digestion

• Salivary glands: Release saliva

  • Contains amylase → breaks starch → glucose

Digestion in Stomach

• Muscular walls: Mechanical digestion through muscular wall movement with chemical digestion (gastric juices)

• Gastric glands:

  • Secrete gastric juice:

    • Protease → digests proteins

    • HCl → acidic pH (1.5–3.5), activates enzymes

    • Mucous → protects stomach lining from acid (if without → Acid burns stomach lining → system failure)

• Time in Stomach
  → ~4 hours → turns food into chyme (watery liquid)

Digestion in Small Intestine

• Main site for digestion + absorption

• Where Chyme goes to
  → receives juices from liver & pancreas

• Villi/Microvilli → ↑ surface area, absorb nutrients via diffusion/osmosis/active transport

• Mechanical: Bile (liver → gallbladder) breaks fats into droplets

• Chemical (pancreas enzymes):

  • Lipase → fats → fatty acids + glycerol

  • Protease → proteins → amino acids

  • Amylase → starch → glucose

Digestion in Large Intestine

• Receives undigested food + water from small intestine

• Water reabsorbed into body

• Forms faeces: water, bacteria, undigested food (can stay up to 3 days)

• Faeces expelled via anus

Bacteria in Large Intestine
→ Helpful → make vitamins

Excretory (Urinary) System, Organs & Functions

• Purpose: Remove toxic metabolic waste (e.g. urea, CO₂, dead cells) from blood.

• Made of "KUBU": 2 Kidneys, 2 Ureters, 1 Bladder, 1 Urethra.

• Metabolism: All chemical reactions in cells/organs.

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• Lungs: remove gaseous waste (carbon dioxide) from the blood when exhale

• Liver: Excretory organ that filters toxins and breaks down old red blood cells.

• Kidneys: Filter blood, remove nitrogen waste, control water balance (osmoregulation); built from 1+ million nephrons—tiny filters that clean the blood.

• Skin: Largest organ; excretes sweat from sweat gland (salt, urea) and sheds dead cells through sweat glands.

• Ureters: Carry urine → bladder

• Bladder: Stores urine

• Urethra: Releases urine

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Fun fact:

• Faeces are brown from dead red blood cells (bilirubin).

• CO₂ comes from cellular respiration.

• Urea forms from protein breakdown.

Endocrine System

• Made of glands that produce hormones (e.g., thyroxine, testosterone, insulin)

• Receptor: special proteins on surface of cell which attach to hormone, and respond depending on hormone type, and change how cell behaves.

• Hormones: Chemical messengers in blood → act on target cells, transported to where needed.

Endocrine vs Nervous System

Feature	Endocrine System	Nervous System
Type of message	Chemical	Chemical (neurotransmitters) AND Electrical
System that transports message	Circulatory system	Nervous system
How message travels	Hormones in bloodstream	Electrical impulses through neurons
Change detected by receptors	Yes	Yes
Speed to reach target	Slow	Very fast
Speed of response	Slow	Very fast
Duration of response	Long-lasting	Short-lasting
Distribution of response	Spread out to various cells/organs/tissues	Localised to one small area

Homeostasis and its importance

Homeostasis

• Maintaining a stable internal environment within narrow limits, despite external changes

Why it's important:

• Allows growth, tissue repair, reproduction, and normal cell function

• If internal conditions go beyond tolerance limits too long → malfunction, illness, or death

What it maintains:

1. BGL

2. Blood pH;

3. Blood CO₂/O₂ Levels;

4. Blood Pressure;

5. Heart Rate;

6. Blood Osmality;

7. Blood salt/electrolyte concentration.

Maintaining Homeostasis (Stimulus-Response Model)

1. Stimulus: Change in internal/external environment outside "set point"

2. Receptor: Specialized cells detect change and send message to control center

3. Control Center: Brain (hypothalamus/pituitary) sends message via nerves/hormones to effector

4. Effector: Muscle, gland, or organ responds to the message

5. Response: Counteracts the original stimulus, bringing system back to set point

Feedback Systems:

• Most biological systems use negative feedback: change in opposite direction to restore balance (return to set point)

Thermoregulation

Thermoregulation

• Endotherms (mammals/birds): Generate own body heat

• Ectotherms (other animals): Rely on external sources (e.g., sun) for body heat

• Thermoregulators receive info on skin.

Human Body Temperature Regulation

• Set point: 37°C (range: 35.6°C - 37.8°C)

• 80% of energy from cellular respiration is used to maintain body temperature

Physiological Responses

• Below 37°C: Vasoconstriction (blood vessel constriction, less close to skin, reduce heat loss), shivering (muscle movement), piloerection, increased metabolism

• Above 37°C: Vasodilation (blood vessel expansion, closer to skin, heat loss), sweating

Negative Feedback Loop: Body Temperature Regulation

• Stimulus: Temp goes above or below 37°C

• Receptor: Thermoregulator on skin and hypothalamus detect change

• Control Center: Hypothalamus processes the info, thyroid releases thyroxine for increased metabolism

• Effector:

  • If too hot: Sweat gland and vasodilation

  • If too cold: Shivering and vasoconstriction

• Response: Temp returns to normal (37°C)

Behavioral Responses to Temperature Regulation

• When Too Hot (Above 37.8°C):

  • Seek shade or cooler environment

  • Remove clothing to release heat

  • Increase water intake to cool down

  • Decrease physical activity to avoid generating more heat

• When Too Cold (Below 35.6°C):

  • Seek warmth or heated environment

  • Add clothing or blanket to retain heat

  • Curl up to conserve warmth

  • Increase physical activity to generate more heat

Osmoregulation

• Involves maintaining water balance and solute balance.

• Water intake (gain):

  • Drinking/eating: ~2.4L

  • Metabolism (aerobic respiration)

• Water loss:

  • Urine, faeces, evaporation, sweat: ~3.3L max

• Importance:

  • Maintains blood solute concentration, volume, and pressure

  • Supports biochemical reactions (which occur in aqueous environments)

Physiological Osmoregulation

Physiological Osmoregulation

1. High Osmolality (low water in blood)

   • Detected by osmoreceptors in the hypothalamus.

2. Message Sent to Pituitary Gland

   • Pituitary releases ADH (Antidiuretic Hormone).

3. ADH Acts on Kidneys

   • Increases water reabsorption into the bloodstream.

4. Urine Becomes More Concentrated

   • Less water is lost in urine to conserve hydration.

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If Well-Hydrated (Low Osmolality)

1. Low Osmolality

   • Hypothalamus detects sufficient water in blood.

2. Less ADH Released

   • Kidneys excrete more dilute urine, removing excess water

Negative Feedback System: Osmoregulation

• Stimulus

  • High osmolality (low water in blood) or low osmolality (too much water in blood).

• Receptor

  • Osmoreceptors in the hypothalamus detect changes in blood osmolality.

• Control Center

  • Hypothalamus sends a message to the pituitary gland, which releases ADH (Antidiuretic Hormone).

• Effector

  • Kidneys respond to ADH by adjusting water reabsorption.

• Response

  • If dehydrated (high osmolality): Kidneys reabsorb more water, producing concentrated urine.

  • If overhydrated (low osmolality): Less ADH is released, leading to more dilute urine.

Glucose Regulation

• Glucose is converted into ATP via cellular respiration by cells for energy.

• Excess glucose is stored as glycogen in the liver and muscle cells. If there’s more, it’s converted to fat (or back to glucose if needed.).

• BGL (Blood Glucose Level) is the concentration of glucose in the blood.

• BGL is regulated within the range of 3.5 - 8 mol/L.

Blood Glucose Regulation - Physiological

• Stimulus:

  • High or low blood glucose levels (BGL).

• Receptor:

  • Chemorecetors on Pancreas detects BGL changes via alpha and beta cells.

• Control Center:

  • High BGL: Beta cells release insulin.

  • Low BGL: Alpha cells release glucagon.

• Effector:

  • Insulin: Lowers BGL by promoting glucose uptake and glycogen storage.

  • Glucagon: Raises BGL by stimulating glycogen breakdown and glucose release.

• Response:

  • High BGL: Glucose uptake and storage.

  • Low BGL: Glycogen release into blood.

Negative Feedback Loop: Blood-Glucose Regulation

Blood-Glucose Response

• Hyperglycaemia (High Blood Glucose): BGL above 8mmol/L, often seen in Type 1 diabetes.

• Hypoglycaemia (Low Blood Glucose): BGL below the healthy range (typically below 4mmol/L).

Type 1 Diabetes

• Autoimmune disorder where the immune system destroys beta cells in the pancreas, preventing insulin production.

• Symptoms: High BGL, tissue/nerve damage, eye issues, kidney function decline, stroke.

Hyperthyroidism

• Overactive thyroid gland, producing excessive thyroxine.

• Symptoms: Increased metabolism, higher body temperature, weight loss, rapid heart rate, excess sweating.

• Treatments: Medication or surgery to remove part of the thyroid.

Autotrophs and Heterotrophs

Autotrophs are organisms that can make their own food from light and inorganic molecules.

Heterotrophs is an organism that must consume other organisms to generate energy.

What is the difference between organic and inorganic compounds?

• Organic Compounds:

  • Contain carbon atoms bonded mainly to hydrogen (C-H bonds).

  • Found in living things.

  • Examples: glucose (C₆H₁₂O₆), methane (CH₄), DNA.

• Inorganic Compounds:

  • Usually do not have carbon-hydrogen bonds, such as minerals.

  • Found in non-living matter.

  • Examples: water (H₂O), sodium chloride (NaCl), carbon dioxide (CO₂ — exception: CO₂ is inorganic even though it has carbon).

Exam Tips

ALWAYS INCLUDE DATA WHEN COMPARING/EXPLAINING!