L5 Physiology

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Questions and Answers

What defines the Basal Metabolic Rate (BMR)?

The energy input from ingested food

The energy expenditure during physical activities only

The metabolic activity required to maintain basic body functions at rest (correct)

The total energy output including exercise and digestion

Which statement accurately describes energy conversion in the body?

Approximately 25% of chemical energy from food is used for bodily functions (correct)

All energy from nutrients is fully utilized for biological work

Energy output significantly exceeds energy input in a healthy metabolism

Energy can be created from heat during metabolism

What does the term 'energy balance' refer to?

The balance between energy intake and energy output (correct)

The equivalence of energy produced and energy stored in the body

The sum total of all energy transformations in physical activities

The calories consumed in relation to calories burned during exercise

Which factor is NOT typically considered when assessing obesity?

Social status Signup and view all the answers

What is a primary component of energy output in the body?

External work by skeletal muscles Signup and view all the answers

Which factors can influence basal metabolic rate (BMR)?

Gender Signup and view all the answers

What is the key difference between direct and indirect calorimetry?

Direct calorimetry measures heat production, while indirect calorimetry measures O2 uptake. Signup and view all the answers

When should basal metabolic rate be measured for optimal accuracy?

At room temperature with no food intake for 12 hours Signup and view all the answers

What effect does high leptin have on appetite control?

Suppresses appetite Signup and view all the answers

Which statement about energy balance is correct?

Positive energy balance indicates energy input is greater than output. Signup and view all the answers

Which hormones play a role in long-term energy balance maintenance?

Leptin and insulin Signup and view all the answers

What is the role of Neuropeptide Y (NPY) in appetite control?

Stimulates appetite and increases food intake Signup and view all the answers

How does exercise affect basal metabolic rate?

It can increase BMR temporarily. Signup and view all the answers

What is the primary function of ghrelin in the regulation of eating behavior?

Stimulates appetite Signup and view all the answers

What hormone is known to inhibit appetite by acting on NPY-secreting neurons?

Peptide YY (PYY) Signup and view all the answers

Which energy system produces ATP at the fastest rate?

Immediate Phosphagen Signup and view all the answers

Under which condition does the anaerobic contribution to ATP production dominate?

Short term, high intensity activity Signup and view all the answers

What is the effect of exercise on blood flow distribution during physical activity?

Increases blood flow to the heart and skin Signup and view all the answers

What defines obesity as discussed in the content?

Excess fat content in adipose tissue Signup and view all the answers

What cardiovascular change does not significantly alter during exercise?

Blood Flow to the Brain Signup and view all the answers

Why is frequent exercise recommended for diabetic patients?

It reduces plasma hyperglycemia Signup and view all the answers

Study Notes

Basal Metabolic Rate (BMR)

BMR: The energy expenditure per unit of time required to maintain basic body functions at rest.
Measured in kilocalories of heat produced per hour.
Affected by:
- Gender
- Age
- Temperature
- Exercise
- Smoking
- Food Consumption
- Pregnancy
- Sleep
- Hormones

Energy Balance

Energy cannot be created or destroyed (First Law of Thermodynamics).
Energy balance (input vs output)
- Input: Ingested food
- Output:
  - External work: Skeletal muscle contraction for movement.
  - Internal work: All other biological energy expenditure not related to external work.
Energy conversion:
- 25% of chemical energy in foods is used for biological work.
- 75% is converted to heat to maintain body temperature.

Measuring BMR

Measured using:
- Direct calorimetry: Measures the difference in temperature of water entering and leaving a chamber.
- Indirect calorimetry: Measures oxygen uptake.
- Food + O2 → CO2 + H2O + energy (mostly heat)

Conditions for Measuring BMR

Physical rest: Minimal muscle activity.
Mental rest: No stress or anxiety.
Room temperature: Comfortable environment (~25°C).
No recent food intake: Typically, 12 hours fasting.

Regulation of Food Intake

Short-term regulation: Determines the size and frequency of meals
Long-term regulation: Works to maintain normal levels of energy stores in the body.
Appetite control at the Arcuate Nucleus of the Hypothalamus:
- Neuropeptide Y (NPY) secreting neurons: Stimulate appetite, increase food intake.
- Melanocortin stimulating hormone (α –MSH) secreting neurons: Decrease appetite, reduce food intake.

Long-term Maintenance of Energy Balance

Leptin:
- Secreted from adipocytes (fat cells).
- Serum leptin levels are proportional to body fat stores.
- High leptin suppresses appetite by inhibiting NPY-secreting neurons and stimulating melanocortin-secreting neurons.
Insulin:
- Secreted from the pancreas
- Released in response to high blood glucose levels (hyperglycemia)
- High insulin suppresses appetite by inhibiting NPY-secreting neurons and stimulating melanocortin-secreting neurons.

Short-term Regulation of Eating Behavior

Ghrelin:
- Secreted from the stomach.
- Known as the "hunger hormone."
- Stimulates appetite by stimulating hypothalamic NPY-secreting neurons.
- Initiates meals.
Peptide YY (PYY):
- Produced by the small and large intestines.
- Opposite effect of Ghrelin – inhibits appetite.
- Inhibits hypothalamic NPY-secreting neurons.
- Terminates meals.

Obesity

Defined as: Excessive fat content in the adipose tissue stores.
Occurs due to positive energy balance and dysregulation of gastrointestinal hormones.

Exercise Physiology

Energy for muscle contraction: Requires ATP.
Sources of ATP:
- Myosin ATPase: Breaks down ATP as the muscle fiber contracts.
- Phosphocreatine (PC): A rapid source of energy.
- Glycolysis: The breakdown of glucose to generate ATP.
- Oxidative phosphorylation: Uses oxygen to produce ATP.

Energy Systems for Exercise

Immediate (Phosphocreatine and ATP): (4 molecules of ATP/min) Provides energy for 5 to 10 seconds of high-intensity exercise.
Short-term (Glycogen-Lactic Acid): (2.5 molecules of ATP/min) Provides energy for 1 to 1.6 minutes of intense exercise.
Long-term (Aerobic): (1 molecule of ATP/min) Provides energy for sustained moderate-intensity exercise.

Interaction between Energy Systems

A combination of anaerobic and aerobic processes is always at work during exercise, with one system dominating depending on the intensity.
Anaerobic systems dominate during short-term and high-intensity activity.
Aerobic systems dominate during long-term and lower to moderate intensity activity.

Cardiovascular Changes During Exercise

Increases:
- Heart rate
- Venous return
- Stroke volume
- Cardiac output
- Blood flow to skeletal muscles
- Blood flow to the heart muscle
- Blood flow to the skin
- Mean arterial blood pressure
Decreases:
- Blood flow to the gastrointestinal tract, kidneys, and other organs.
- Total peripheral resistance.
Unchanged: Blood flow to the brain.

Benefits of Exercise for Diabetics

Exercise helps regulate blood glucose levels.
Frequent exercise can reduce hyperglycemia (high blood glucose) by:
- Increasing insulin sensitivity.
- Improving glucose uptake by muscles during exercise.

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