Biology Unit 9 Explanation & Notes

28-2 Mechanisms of Homeostasis – finding balance

Homeostasis is the regulation and maintenance of the internal environment – temperature, fluids, salts, pH, nutrients, and gases – within the narrow ranges that support human life. The internal control systems of the body respond quickly to any outside or internal changes.

Control Systems in the BodySensors Control center Communication systems

Receptors that gather info about inside/outside body

conditions

Receives info from the sensors and compares it to an ideal body condition; sends messages

if body conditions are not ideal

Carries messages from control center through the nervous or endocrine system (hormones) and has body

respond to inside/outside changes

Feedback is information from sensors that allow a control center to compare current conditions to a standard set of required conditions. Information is constantly moving through your sensors, a control center, and the target.

Negative feedback – A control system that responds against changes that go above or below a set condition (like an air conditioner)

Positive feedback – A control system that responds with changes to go away from above or below a set condition (blood rushing to cut on finger)

28-3 Interactions Among Systems – organs are connected

What does it mean to “regulate”? ___________________________________________________________.

Thermoregulation is the process of maintaining a steady body temperature under many conditions. You sweat when it is hot and you shiver when it is cold. Your skin and muscles work together to maintain a constant body temperature but they are connected to other organ systems like the respiratory, circulatory, nervous, and endocrine systems.

What organ systems do you see at work in this diagram?

PARTNER UP! – Complete pg 5&6 in your UNIT 9 SAW!

29-1 How Organ Systems Communicate

The nervous system is a physically connected network of cells, tissues, and organs that controls thoughts and voluntary or involuntary movements (squinting in the sun).

The endocrine system is a collection of physically disconnected organs that helps control growth, development, and responses to the environment (sweating on a hot day).

A stimulus is something that causes a response. For humans, it could be a chemical, cellular, or behaviorial trigger that causes a change.

The central nervous system (CNS) includes the brain and spinal cord which interprets messages from other nerves and stores them for later use. The peripheral nervous system (PNS) is a network of nerves that sends messages between the CNS and the organs.

29-2 Neurons – receiving and transmitting signals

A neuron is a specialized cell that stores information and carries messages within the nervous system and between other body systems.

There are three main parts:

Cell body – contains the nucleus and organelles

Dendrites – branchlike extensions of the cytoplasm and the cell membrane that receive messages from neighboring cells

Axon – a long extension that carries electrical messages away from the cell body and passes them to other cells.

DRAW IT! Pg. 876 in textbook

Draw a neuron with the cell body, dendrites, and axon

Before neurons are stimulated, they are considered to be “at rest.” Inside the neuron cell it is more negatively charged than the outside. The difference in electrical charge along the neuron cell membrane is called the resting potential, because it has the potential to transmit a signal.

An action potential when an electrical impulse is sent down an axon by the changes in the electrical charges.

Before an action potential moves into the next neuron, it crosses a tiny gap between the neurons called a synapse. The axon terminal, the part of the axon through which the impulse leaves that neuron, has chemical-filled vesicles. When the impulse reaches the terminal, the vesicles attach to the membrane and releases chemicals or neurotransmitters that signal a neighboring neuron to create an action potential.

Bio Question: Why aren’t neurons directly wired together? Think about the electricity in your house!

Class lab work: pg. 22-23 – let’s complete the animated biology activity together

29-5 Brain Function and Chemistry

Chemicals are needed for your nervous system to work and they also interact with your brain to make memories, influence emotions, and control muscles. However, if too much or too little of the neurotransmitters are produced, an area of a brain can be affected which can lead to illnesses such as depression or schizophrenia.

Drugs alter brain chemistry.

Drugs are primarily taken to bring one system in the body back to homeostasis but side effects could cause another system to go out of homeostasis. Certain drugs, prescription or recreational, can lead to addiction which is the physiological need for a substance. A person becomes addicted when the body changes the way it works so that the drug is needed in order to function normally.

If there is too much neurotransmitter present in the synapse, the brain cells goes through desensitization by lowering the amount of receptors in the neuron to reduce the amount of impulses. If there is too little neurotransmitter, the brain cells goes through sensitization by increasing the number of receptors to produce more impulses.

What does a synapse look like with too much neurotransmitter? How about with too little neurotransmitter? (pg. 893)

29-6 The Endocrine System and Hormones – chemicals that react and balance

If you hear a loud clap, your body would react by releasing chemicals that speeds up your heart rate and send bloods to your muscles in order to fight or run. Hormones are chemical signals made by the endocrine system that help the body grow, develop, and keep homeostasis. These hormones are created in organs called glands, found throughout the body. Glands will release hormones into the bloodstream which then interact with only specific cells that have the right receptors.

The endocrine system has several glands that release certain hormones. The major ones are:

Hypothalamus – stimulates the production of hormones that control growth, reproduction, and body temperature. The nervous and endocrine systems connect to each other at the hypothalamus. This is where releasing hormones, or hormones that stimulate other glands to release their hormones, are stored.

PARTNER UP! Complete pg. 29,30,40 in your SAW

Pituitary gland – produces hormones that control cell growth and water concentration in blood; influences adrenal, thyroid, and sex glands

TOO MUCH NEUROTRANSMITTERTOO LITTLE NEUROTRANSMITTER

30-1 Respiratory and Circulatory Functions

There are thousands of kilometers of blood vessels and millions of air sacs in your body and all are constantly being used to circulate blood and oxygen to keep you alive. The circulatory system transports blood, brings vital supplies to the cells, and carries away their waste. The blood vessels also make sure low-oxygen blood and high-oxygen blood do not mix. The respiratory system is where gas exchange occurs when blood picks up oxygen and drops off carbon dioxide in the lungs. BOTH OF THESE SYSTEMS WORK TOGETHER TO MAINTAIN HOMEOSTASIS!

Circulatory System Key Terms:

Lungs – absorbs oxygen from the air you inhale

Alveoli – tiny clusters of air sacs in lungs

Trachea – windpipe made of soft tissue with rings of cartilage

Diaphragm – muscle under rib cage that controls breathing

Respiratory System Key Terms:

Heart – muscular pump that keeps blood moving in body

Arteries – blood vessels that carry blood away from heart

Veins – blood vessels that carry blood back to heart

Capillaries – small blood vessels that transport blood to and from cells

How long can you hold your breath? Let’s see! Take a deep breath, and let’s time it! Ready? GO!

I held my breath for this long: _____________

What “forced” me to take a breath? Think feedback!

30-2 Respiration and Gas Exchange – oxygen and CO2 cross paths

In the alveoli, the respiratory and circulatory systems come together to exchange gas. Here, O2 and CO2 are carried by the blood. Gases move by diffusion – moving from area of high concentration to low concentration. So when red blood cells, a type of cell that picks up oxygen in the lungs and delivers them to throughout the body, enter the capillaries, CO2 diffuses from them into the alveoli while oxygen diffuses from the alveoli into the red blood cells.

Since breathing (gas exchange) is extremely important, the brain has centers that monitor dissolved gases in the

blood like CO2. If levels are high, signals are sent to make the diaphragm and rib cage muscles to work harder to increase oxygen flow.

Bio thought: Why can’t you hold your breath for more than a minute or so?

30-3 The Heart and Circulation – the ultimate pump

A doctor listens to your heartbeat because how it sounds and how fast it beats tells a lot about how it is working. Each day, your heart beats about 100,000 times (2.5 billion times in 70 years).

Heart structure: (HIGHLIGHTER TIME!)

Atrium – two smaller, upper chambers

Ventricles – two larger, lower chambers

Valves – tissue flaps preventing blood flowing backwards

Blood flow in heart: (HIGHLIGHTER RIDE TIME!)

1. Low-oxygen blood enters right atrium, then to right ventricle

2. Right ventricle pumps low-oxygen blood to the lungs

3. High-oxygen blood enters left atrium from lungs, then to left ventricle

4. Left ventricle pumps high-oxygen blood to body

PARTNER UP! Complete pg. 57 and 58 in your unit 9 SAW

30-4 Blood Vessels and Transport

Arteries, Veins, and Capillaries

Arteries need to be strong and flexible because they carry blood under large pressure. The elastic layers of arteries expand and contract to push the blood through. Veins, however, lack thick walls. Instead, it relies on surrounding muscles to push the blood

Pulmonary Circulation

Systemic Circulation

Location Occurs only between heart and lungs

Occurs between heart and body,

except lungs

Function

Carries low-oxygen blood to the lungs, then high-oxygen

blood to heart

Carries high-oxygen blood to the body, then low-oxygen

blood to heart

back to the heart and also has valves to prevent blood from flowing backwards. Capillaries have really thin cell walls which make it easy for materials and gases to diffuse into and out of the blood.

Bio Question: how come arteries do not need valves?

PULSE CHECK ACTIVITY!

Find a partner to check your pulse. You will be measuring your pulse twice, once at a relaxed state and again at an active state.

RELAXED STATE: take a minute and relax by sitting comfortably in your chair, breathing deeply, and closing your eyes. When you are ready, have your partner check your pulse by either placing the index and middle finger on the wrist or inside of the elbow. Count the pulses for 30 seconds and then multiply it by 2. Record your results, now it’s your partners turn.

MY RELAXED PULSE RATE IS: ____________ Beats Per Minute

ACTIVE STATE: This time, grab a book and raise it in the air for one minute to raise your heart rate. Then, immediately have your partner take your pulse for 30 seconds and multiply it by 2. Record your results and then it’s your partner’s turn.

MY ACTIVE PULSE RATE IS: _____________ Beats Per Minute

Questions:

1.) How did your two pulse rates compare? How did you feel during each one?

2.) Why did your body increase the pulse rate during the active state?

3.) Why do you think exercise is important for your circulatory health?