Topic 21- Nutrition

Outcomes:

Compare and Contrast the Nutritional Needs of Animals

Sequence the Regulation of Digestion

1. Food Enters Oral Cavity

   • Neural signals trigger saliva secretion → bolus forms.

2. Swallowing via Pharynx → Stomach

   • Food stretches stomach → gastrin released → gastric juice produced + churning begins.

3. Chyme Enters Duodenum (Small Intestine)

   • CCK triggers enzyme release from pancreas and bile from gallbladder.

   • Secretin stimulates bicarbonate release from pancreas.

4. High Fat Content Detected

   • CCK & Secretin increase → slow stomach emptying and peristalsis.

Hypothesize and Diagnose the Impact of Variability on Digestion Regulation

Sequence Calorie Use

• Immediate Energy:

  • Carbs used first (quick energy source, esp. for brain).

• Short-Term Storage / Moderate Energy:

  • Proteins used if carbs/fats are low (but generate ammonia).

• Long-Term Energy Reserve:

  • Fats (triglycerides) metabolized more slowly but provide more kcal/g.

Hypothesize and Diagnose the Impact of Variability on Calorie Use

Sequence the Regulation of Appetite and Consumption

• Stomach is Empty

  • Ghrelin released → stimulates hunger.

• Food Intake

  • Insulin (pancreas) and PYY (small intestine) released post-meal → suppress appetite.

• Fat Storage Status

  • Leptin (from adipose tissue) reflects long-term reserves. Low leptin → increased hunger.

• Satiety Center Activation

  • Stomach stretch sends signal to brain → fullness sensed.

Hypothesize and Diagnose the Impact of Variability on Appetite and Consumption

Sequence Glucose Homeostasis

1. High Blood Glucose (after a meal)

   • Insulin released → glucose uptake by cells → stored as glycogen.

2. Low Blood Glucose (between meals/fasting)

   • Glucagon released → glycogen broken down → glucose released into blood.

Hypothesize and Diagnose the Impact of Variability on Glucose Homeostasis

I. Diet and Nutritional Needs

A. Chemical Energy

1. Nutrition: The process by which food provides chemical energy and nutrients needed by the body.

2. Animal Feeding Categories:

   • Herbivores: Eat only plants (e.g., cows, deer).

   • Carnivores: Require meat for survival (e.g., cats—cannot survive on plant-based diets).

   • Omnivores: Eat both plant and animal matter (e.g., raccoons, humans); must incorporate varied protein sources.

3. Protein Requirement: Even omnivores need external sources of amino acids since we cannot synthesize all of them.

4. Caloric Values:

   • Carbohydrates: 1g = 4 kcal (primary energy source, ~50% of daily calories)

   • Proteins: 1g = 4 kcal

   • Lipids: 1g = 9 kcal (most are triglycerides; energy-dense)

   • Note on Calories:

     • U.S. food labels use “Calories” (with capital C) = kilocalories.

     • 1 Calorie (big C) = 1000 calories (little c).

     • Always check units—some international products use lowercase 'c'.

5. Energy Sources:

   • Fats: Higher energy yield, slower to metabolize.

   • Carbs: Quick, accessible energy; preferred by the brain.

   • Proteins: Can be used for energy, but breakdown produces ammonia, leading to sweat odor after intense workouts.

B. Organic Building Blocks

1. Carbon Source: Must come from organic material (plants, animals, fungi—not rocks).

2. Protein Source: Required to obtain essential amino acids.

3. Essential Nutrients: Cannot be synthesized; must be ingested or death will occur over time.

4. Essential Amino Acids:

   • 20 total; humans can synthesize ~11.

   • Adults require 8, infants require 9 (e.g., histidine must be supplemented in formula).

   • Can be obtained from diverse sources (grains + legumes, spinach, rice, etc.).

5. Essential Fatty Acids:

   • Linoleic acid & Linolenic acid (polyunsaturated)

   • Found in seeds, oils, vegetables

   • Not present in large quantities in meats like chicken—must eat a variety (e.g., nuts, spinach, citrus salad with walnuts).

6. Balanced Diet Message:

   • No need for extreme plans—just variety and moderation.

   • Many fad diets cause people to miss essential nutrients.

   • In the U.S., deficiency is rare but possible with restricted diets.

C. Essential Vitamins

1. Water-Soluble Vitamins:

   • Not stored; must be consumed regularly.

   • B-complex:

     • B3 (Niacin): Component of NAD/NADP (electron carriers in respiration).

     • B9 (Folic Acid):

       • Prevents anemia and neural tube defects.

       • Deficiency can lead to birth defects where the nervous system develops externally.

     • B12 (Cobalamin):

       • Needed for RBC formation.

       • Only found in animal products or fortified foods (critical for vegans).

       • Deficiency causes fatigue, low energy, and anemia—common after 6+ months without animal-based foods.

   • Vitamin C (Ascorbic Acid):

     • For collagen synthesis, antioxidant activity, and iron absorption.

     • Scurvy: Leads to bleeding gums, fatigue, weak connective tissue, yellow skin, and tooth loss.

     • Combine with iron-rich foods for improved absorption (e.g., spinach + citrus).

2. Fat-Soluble Vitamins (stored in body fat, risk of overdose):

   • Vitamin A:

     • Supports vision (rhodopsin production).

     • Overdose (especially in children) can cause toxicity.

   • Vitamin D:

     • Enables calcium absorption; made with UV exposure.

     • Found in fortified milk.

     • Deficiency → rickets in children, osteomalacia in adults.

     • Excessive supplements (20,000–50,000 IU) can cause hallucinations, organ damage.

     • Get levels tested before supplementing.

3. Minerals:

   • Calcium: Bones, teeth, muscle signaling.

   • Phosphorus: ATP, nucleic acids, phospholipids.

   • Sulfur: Component of disulfide bridges in proteins.

   • Chloride (Cl⁻): Water balance, HCl production, nerve function.

   • Magnesium: Enzyme cofactor, muscle/nerve function.

4. Trace Elements:

   • Iron: Hemoglobin & cytochromes in the ETC.

   • Iodide: Thyroid hormone synthesis.

II. Regulation of Appetite & Consumption

A. Control of Fat Storage & Metabolism

• Animals like humans are bulk feeders, eating at intervals.

• Digestive processes are stimulated by food presence in organs.

• Food arrival triggers:

  • Hormonal secretion

  • Peristalsis

  • Activation of digestive compartments

B. Nervous System

• Sends signals that regulate appetite and digestion.

• Satiety center (in the brain) signals fullness based on stomach stretch.

C. Hormonal Regulation

1. Stimulates Hunger:

   • Ghrelin: Secreted by stomach when empty.

2. Suppresses Appetite:

   • Insulin: From pancreas after a meal.

   • PYY: From small intestine post-meal.

   • Leptin: From adipose tissue; levels fall with fat loss → increased hunger.

III. Regulation of Digestion

A. Oral Cavity

• Digestive steps activated only when food enters.

• Saliva secretion triggered by neural signals.

• Bolus formation leads to swallowing via pharynx.

B. Stomach

• Controlled by enteric nervous system.

• Food arrival → stretching of stomach → secretion of gastrin:

  • Gastrin stimulates gastric juice production.

  • Promotes churning of food.

C. Small Intestine (Duodenum)

1. Chyme triggers hormones:

   • Cholecystokinin (CCK):

     • Pancreas → digestive enzymes

     • Gallbladder → bile

   • Secretin:

     • Pancreas → bicarbonate (HCO₃⁻) to neutralize acid

2. High-fat chyme:

   • Increases CCK & Secretin → slows peristalsis and stomach emptying

3. Blood Glucose Regulation:

   • High glucose → insulin release

   • Low glucose → glucagon release

4. Diabetes Mellitus:

   • Caused by insulin deficiency or resistance

   • Results in high blood glucose, kidney stress, and long-term damage (e.g., blindness, gangrene)