Regulating the Body to Maintain Homeostasis HOMEOSTASIS

As in all systems in nature, animal systems must maintain balance. We call this homeostasis.

How do ecosystems maintain balance?

In animal systems, what must be balanced? Levels of oxygen/carbon dioxide Amount of water Levels of hormones Levels of waste Body temperature (warm-blooded animals)

Organ systems work together to maintain balance Levels of oxygen/carbon dioxide Taken in and released by the respiratory system Transported around the body by the circulatory system Amount of water Absorbed through the digestive tract Removed by the excretory system as urine. Levels of hormones Produced in endocrine glands Delivered to their target cells by the circulatory system Levels of waste Filtered out of the blood when it passes through the kidneys, organs of the excretory system. Body temperature Sensed and maintained by the integumentary system

There are a lot of organ systems at work here. How does the body monitor all of this?

Your Brain Does the Monitoring How does this happen? Certain parts of your brain are responsible for completing specific tasks.

The Brain is part of the Nervous System. Two parts of the nervous system: Central Nervous System (CNS) Control center of the body Consists of the brain and spinal cord Functions to interpret and respond to information from the environment and from within the body Peripheral Nervous System Transmits signals between organs and CNS Sensory neurons-send information from sense organs to CNS. Motor neurons-send commands from CNS to muscles and other organs.

The Brain CEREBRUM Learning, Memory, Perception, Intellectual Function Regulates balance, posture, and movement Regulates breathing and heart rate, feelings of hunger and thirst, controls secretions of hormones, regulates body temperature, sleep. Which part of the brain do you think will be involved in maintaining homeostasis in an animal system? THE BRAIN STEM

The Brain Stem-divided into two areas The Upper Brain Stem - Thalamus- central site for sensory processing Hypothalamus- regulates heart rate, breathing rate, feelings of hunger and thirst, controls the release of hormones The Lower Brain Stem Relays information throughout the CNS Medulla oblongata- Regulates heart rate, breathing rate, body temperature, and sleep

How does the brain relay messages to the rest of the body? Specialized cells called neurons. Networks of neurons constantly gather, interpret, and respond to information about the body’s internal state and environmental conditions. Structure of a Neuron

How does the brain relay messages to the rest of the body? Neurons do not touch end to end. So how do they pass on messages? There is a gap between two neurons called a synapse. The neuron must use chemical messengers called neurotransmitters to pass the message across the synapse.

We are going to start by looking at O 2 & CO 2 levels. Which system is responsible for bringing O 2 into the body and releasing CO 2 ? RESPIRATORY SYSTEM Back to the brain regulating homeostasis by monitoring what is in the bloodstream!

Respiratory System How does the structure of the alveoli relate to its function?

The RESPIRATORY SYSTEM is responsible for the exchange of gases, BUT the breathing rate is not controlled here. The central controlling area for breathing, called the respiratory center, is in the lower part of the brain stem, in the medulla oblongata.

How does the brain do it? Receptors in the brain continuously monitor the amount of CO 2 in the blood. If there is too much CO 2 —the brain sends a signal to increase breathing rates! Why would this happen? If there is too little CO 2 – the brain sends a signal to decrease breathing rates! Why would this happen?

What about waste in the bloodstream? As cells carry out their daily activities they produce wastes called metabolic waste. The wastes leave the cell by crossing the cell membrane and travels in the bloodstream. These wastes are highly toxic and will poison the organism if not removed.

What about wastes in the bloodstream? The brain monitors the amount of waste in the bloodstream. How do you get rid of wastes? As your blood is flowing through your body, it passes through the kidneys. The kidneys act as filters, removing wastes from your blood.

Wastes & the Excretory System What wastes are filtered? Excess water Metabolic wastes Ammonia (urea) They combine to form urine which is stored in the bladder until it is ready to be excreted when you urinate. Every day the kidneys send about 6 cups of urine to the bladder! Every day the kidneys send about 6 cups of urine to the bladder!

How do the kidneys filter blood? Within each kidney are about one million nephrons. Blood passes through the nephron where wastes (urea, excess water, salts) are filtered out. The cleansed blood goes back into the veins that carry the blood from the kidneys and back to the heart.

The kidneys aren’t the only part of the human body that performs excretion (removal of wastes). Your skin excretes salts, water, small amounts of nitrogen wastes, and other substances as sweat. Your lungs excrete carbon dioxide (a waste!) and water vapor in exhaled air.

Excretion of Wastes in Animals Simple aquatic invertebrates and some fishes excrete ammonia into the water through their skin or gills by diffusion. Other animals, especially terrestrial animals, need to minimize water loss. To do so, they convert ammonia to nontoxic urea and it is eliminated by urination. The urine is concentrated or diluted based on how much water is available. In this way, eliminating metabolic wastes is linked to maintaining water balance.

Okay, so far we’ve regulated CO 2 /O 2 levels and wastes. What about body temperature? Not all animals have to maintain a constant body temperature. Warm-blooded Maintain a constant internal temperature using their metabolism. endothermy. Called endothermy. Cold-Blooded Adjust to the temperature of their surroundings. Do not use their metabolism to regulate body temperature.

How do endotherms regulate their internal temperature? Your body maintains a constant temperature due to the flow of blood through the blood vessels just under the skin. To release heat to the air, blood flow is increased to the vessels. To retain heat, blood is shunted away from the skin. How does your body know what temperature it is?

Because of this, endotherms can stay active at temperatures that would slow down the activity of ectotherms.

REVIEW WHAT WE HAVE LEARNED SO FAR: We rely on our bloodstream to : deliver nutrients & oxygen carry wastes to be filtered out in the kidneys to assist in maintaining body temperature The brain helps monitor the substances in the bloodstream & body temperature. It sends signals to the body via neurons to respond to changes in the levels of the substances.

How is balance accomplished? Levels of oxygen/carbon dioxide Amount of water Levels of hormones Levels of waste Body temperature (warm-blooded animals)

How does the body adapt to change? Maintaining Homeostasis

Two ways the body responds to change Negative Feedback Positive Feedback

Maintaining Homeostasis Two ways the body responds to change Negative Feedback Change occurs and the body responds by reversing the direction of the change For example, a car trying to maintain a speed of 55 mph, suddenly realizes they are going 80 mph What does the driver do? The driver applies the brakes. What happens to the speed of the car?

Maintaining Homeostasis Two ways the body responds to change Positive Feedback Change occurs and the body responds by pushing forward in the same direction For example, a car trying to maintain a speed of 55 mph, suddenly realizes they are going 20 mph What does the driver do? The driver accelerates. What happens to the speed of the car?

Real Life Example Regulation of Room Temperature A heater works to maintain the temperature of a room at the temperature it is set (72˚F for example) As the unit runs, the temperature will rise above 72˚F. A thermostat detects this increase and shuts off the heater. As the room cools, the thermostat detects the decrease in temperature and signals the heating element to turn on. What would occur if a window was opened so that so that cold air was allowed to come into the room?