Maintaining Homeostasis

Define Homeostasis

How the body’s organ systems, tissues, and cells work, and how their functions are integrated to regulate the body’s internal environment.

Examples of internal environment

temperature, pH, glucose

Why is it important to have a stable Internal Environment?

It keeps enzymes and cellular processes working at its best ability, preventing fatigue, confusion, and performance loss.

Role of a receptor

Nerve endings in the skin sense temperature. It senses the change in the environment, then sends a signal to the control center (in most cases, the brain) which in turn generates a response that is signaled to an effector

external stressor

outside the body, such as intense heat or lack of oxygen

Internal Stressor

within the body, such as a low blood glucose level

Role of control center

The command center, receives signal from the receptor and generates a response to either increase or decrease its activity that is then signaled to the effector (typically in hypothalamus)

Hypothalamus helps regulate? 

• blood pressure

• heart rate

• strength of contraction of the

cardiac muscle tissue

• respiration

• digestion

• body temperature

• thirst and fluid balance

• interaction of the nervous system

and endocrine system

• appetite and food intake

• sleep-wake cycles

The role of an effector 

to carry out the response that adjusts the body's internal conditions. Muscles, glands, or organs, receive a signal from a control center and then perform an action.

Negative feedback

loops work to reverse a stimulus, back to starting point (example. too hot→ sweating to cool body down)

Positive feedback

mechanisms enhance the stimulus

For specific situations- childbirth; blood clotting/injury (platelet adhesion). 

distinguish negative from positive feedback

Positive increases or amplifies a change and negative reverses or reduces a change to maintain balance.

How does CO2 affects blood pH?

It causes a drop in pH (increase in H⁺)- creates acidity

What is pH level in blood and what is the average?

It is the acidity level in the blood ranges from 0-14, the average is 7.35-7.45 (slightly alkaline) 

Ventilation Adjustment

High CO₂ or low pH → chemoreceptors signal the medulla → increased ventilation removes CO₂ and raises pH.

Intrinsic control

internal (regulation of the heart by the heart) the SA node (pacemaker) starts the heartbeat, and the AV node helps spread the signal to make the heart contract in rhythm.

Extrinsic control

(external) comes from outside the heart, the autonomic nervous system (ANS) and hormones (like adrenaline) adjust the heart rate depending on the body’s needs, such as speeding it up during exercise or slowing it down at rest.

Insulin Function

Insulin (from β-cells) lowers glucose by helping cells absorb glucose from the blood and store it as glycogen.

Glucagon function

Glucagon (from α-cells) raises glucose by signaling the liver to break down glycogen and release glucose in the blood 

Exercise effects on insulin sensitivity

Exercise improves insulin sensitivity, the body’s cell responds better to insulin, so glucose is taken up more easily, blood sugar then stays balanced.

normal core temperature

near 37±1 °C, 98.6 °F

Why exercise generates heat

Body heat production increases with metabolic rate , when you exercise your muscles work harder and use more energy (ATP). So exercising generates heat because muscles are metabolically inefficient, only part of that energy is used for movement, the rest is released as heat.

Radiation

The transfer of energy waves from one object and absorbed by another.

Convection

Moving heat from one place to another by the motion of air or water.

Conduction

Heat from deep down moves directly through the body tissues to the skin and then to whatever is touching the skin 

Evaporation

When sweat changes from liquid to vapor, it removes heat from the body.

Why is evaporation dominate during exercise

Because it’s the main way for the body to lose heat during exercise

high humidity reduces evaporation because the air has a lot of water vapor, so it cant absorb your sweat. Because of this it increase thermal strain since your body temperature rises, and makes the heart work harder to circulate blood to the skin. 

Vasoconstriction 

skin narrows to reduce blood flow to the surface, minimizes heat loss

Shivering

Rapid, the muscle involuntarily does contractions which create heat through increased muscle movement

Non-shivering

Hormones increase metabolic rate to produce heat without muscle movement 

What does wind chill do?

Wind chill makes temperature feel colder, increasing the body works harder to stay warm, but frostbite can happen faster since the body is losing heat more quickly.

The unit of clothing insulation

clo

How to reduce convective heat loss?

Air between clothes and skin can be warmed up

key heat acclimatization adaptations

plasma volume, earlier sweating, more dilute sweat

How do adaptations to heat acclimation improve performance

Increased plasma volume improves blood flow and prevents dehydration, earlier sweating starts cooling the body sooner, and more dilute sweat reduces salt loss 

Environmental factors that affect performance

temperature, humidity, altitude

How does altitude affect you

It can lead to sickness and dizziness. There is less oxygen in the air making it harder for the lungs to breath, you can dehydrate because of the water loss from the body since the air is so cold and dry.

Dehydration risks

kidney failure, reduced blood volume, muscle cramps, light headed, less energy

Sweat and evaporation

Sweating helps cool the body through evaporation

Ways to monitor hydration

urine color, osmolarity, body mass changes

Conduction in sports

Cleats getting hot directing from standing on warm turf

Convection in sports

Wind cooling a cyclist or runner because the moving air carries heat away from the skin.

Radiation in sports

The sun radiating heat onto someone while outdoors playing a sport

Evaporation in sports

Dumping water on myself helps cool my body because the extra liquid on my skin evaporates, removing heat and lowering body temperature

Body composition and hypothermia 

Athletes with low body fat and high sweat rates, such as endurance runners, lose heat quickly and have less insulation, making them more prone to hypothermia in cold environments.

Gradual acclimatization

Training in hot conditions over time helps the body adapt

Hydration

Drinking fluids before, during, and after exercise maintains blood volume and cooling ability.

Clothing

Wearing light, breathable, and light-colored clothing helps heat escape and reduces heat absorption.

Cooling strategies

Using ice vests, cold towels, or water immersion before or during exercise helps lower body temperature and prevent overheating.