Homeostasis and Negative/Positive Feedback

Major Body Cavities 

Anatomy and Physiology

Proximal means closer to the origin of the body part or the point of attachment of a limb to the body trunk. Distal means farther from the origin of a body part or the point of attachment of a limb to the body trunk. In this case, because the thigh is closer to the body trunk than the knee, the knee is distal to the thigh.


The cranial cavity is where the brain is located.



The pelvic cavity houses many organs, such as the urinary bladder and the uterus in females, but not the lung.



The pericardial cavity houses the heart.



The body cavity that houses the lungs is known as the __________.


Human Body Systems Functions Overview


divides the body into upper (superior) and lower (inferior) portions in the horizontal plane



A transverse plane divides the body into an upper and lower portion in the horizontal plane.



divides the body into left and right parts that are parallel to, and therefore not directly on, the midline



A parasagittal section divides the body into left and right parts that are parallel to the midline.



cuts the body diagonally between the horizontal and the vertical planes



An oblique section cuts the body diagonally between the horizontal and the vertical planes.



divides the body in two equal left and right sides along the midline



The median, or midsagittal, plane __________.



The spinal cord is located in the dorsal body cavity.



Which internal organ is NOT housed in the ventral body cavity?



the thoracic and abdominopelvic cavities



the vertebral (or spinal), cranial, and pleural cavities



The ventral body cavity has two major subdivisions, the thoracic cavity and the abdominopelvic cavity.



the vertebral (or spinal) and cranial cavities



the vertebral (or spinal), abdominopelvic, and thoracic cavities



The ventral body cavity is subdivided into which of the following sets of cavities?



The neck is included in the axial part of the body.



The head is included in the axial part of the body.



The trunk is included in the axial part of the body.



Which of the following is/are NOT included in the axial part of the body?



release of glucagon to increase a lower-than-normal level of glucose in the blood



This is an example of negative feedback.



labor contractions causing the release of oxytocin, which results in an increase in the quantity of labor contractions



shivering to generate heat when body temperature is below normal



release of insulin to decrease a high level of glucose in the blood



Which of the following is an example of positive feedback?


Anatomical Position and Directional Terms


breathing rate increasing as a result of exercise



A person who has become ill is said to be out of homeostasis. In other words, he or she is suffering from a homeostatic imbalance.



heart rate increasing as a result of exercise



Which of the following is an example of a homeostatic imbalance?


Basic terminology and concepts of Anatomy and Physiology


A frontal (coronal) plane lies vertically and divides the body into anterior (front) and posterior (back) parts.



The frontal (coronal) plane divides the body into superior and inferior parts.



The appendicular part consists of the appendages, or limbs, which are attached to the body's axis.



Which of the following refers to a major body division that includes the limbs?


Homeostasis

Introduction to Anatomy & Physiology

Biological Hierarchy of Organization

In this lesson, we will review the biological hierarchy of organization. Anatomy is the study of the bodyâs structures and physiology is a study of how those structures function. The human body is very complex and to truly understand its complexities we need to first understand how it is organized. Think about a house. Itâs made from a lot of small parts, like boards, nails, and wiring, for example. Right? When we look at living organisms, we see the same thing: a hierarchy of organization, from the simplest level of organization or simplest parts up to the most complex. We refer to this as the biological hierarchy of organization. Here are the levels in the biological hierarchy of organization, from simplest to most complex: starting with the atom; the molecule or compound, the macromolecule; the organelle; the cell; the tissue; the organ; the organ system; and, finally, the organism. Now letâs go through these starting with the simplest, the atom. Chemistry is a science of matter and all matter is made of chemical elements, such as carbon, nitrogen, and oxygen. The smallest piece of an element is an atom. Atoms can unite together to form molecules or compounds. To understand this, consider water. It is made of two atoms of hydrogen joined to one atom of oxygen to form a molecule of water, H2O. Water molecules are quite small but some molecules, such as fat and DNA for example, are rather large. So these are often referred to instead as macromolecules, with âmacroâ meaning large. Atoms, molecules and macromolecules provide the nutrients and building materials our bodies need to stay alive and healthy, and they also participate in chemical reactions that do all of the work performed in our bodies. Macromolecules can unite together to build complex structures that carry out various functions inside cells. These are the organelles. You can think of the organelles as being like âmini organsâ inside of the cells. Examples of organelles include mitochondria, ribosomes, and centrioles. Cells contain the combination of organelles necessary to sustain life and, for this reason, life begins at the cell. With few exceptions, your bodyâs cells are alive. In fact, cells are the basic units of all living organisms. Tissues are groups of cells organized together to perform some common function. For example, muscle tissue contracts to provide movement. There are four general categories of tissues. Epithelial tissues form all of the bodyâs linings and coverings, such as the outer surface of your skin or the lining of your stomach. Connective tissues have many functions and include bone, cartilage, blood, and fibrous connective tissue, which forms very strong ligaments and tendons. Muscle tissue provides movement both of materials through the body as well as movement of the body itself. And nervous tissue allows control of various body processes and also communication throughout the body. Tissues can organize into larger functional units called organs, such as your lungs, your heart, and your liver. Each organ performs at least one specific job. Your lungs, for example, bring in oxygen and clear out carbon dioxide. Multiple organs join together to form organ systems, each with some overall function. For example, the organs in your cardiovascular system are your heart and your blood vessels, and they carry your blood, which is a type of tissue. The heart acts as a pump and the vessels are the pipes, so to speak, through which your blood travels. These structures work together to deliver nutrients and oxygen to your cells to supply their needs and to haul away their waste products. Our organ systems include the integumentary system, which is mostly our skin; the skeletal system, which includes our bones; the muscular system, which includes all of our muscles and their tendons; the nervous system, which includes the brain and all of the nerves in the body; the cardiovascular system that we just spoke about; the lymphatic system, which helps keep us healthy; the respiratory system, that brings in oxygen and clear carbon dioxide; the digestive system, that brings in nutrients; the urinary system, that fine tunes our body fluids and clears our waste products; and the reproductive system, which helps us continue our species. When you put all of these organ systems together, as well as all the levels of organization


The organismal level represents the sum total of all structural levels working together to keep us alive.



Which of the following represents the sum total of all structural levels working together to keep us alive?


Body Cavities and Membranes

Positive and Negative Feedback Loops 

Intro to Anatomy & Physiology

Label Homeostatic Control System


The dorsal body cavity houses the cranial and vertebral cavities, whereas the ventral body cavity houses the thoracic and abdominopelvic cavities.



The cranial cavity is part of __________.


Anatomical Position, Directional Terms, & Body Planes

Homeostasis and Negative Feedback Mechanisms

PRESENTER: Keeping the body's internal environment in optimal condition in the face of a changing external environment is essential for survival. There is a name for this process. It's called homeostasis. What homeostasis really means is that many conditions in the body are held as close as possible to particular values. This allows body cells to survive. Think about a cell in the body. What conditions or levels of variables have to be regulated in order to keep that cell happy? Is it (a) temperature; (b) certain ions (such as sodium, potassium, calcium, and hydrogen); (c) nutrients (such as glucose); (d) oxygen and carbon dioxide; or (e) all of the above? The correct answer is (e). These and many other variables need to be controlled. Working together, the body's organ systems accomplish this feat using a mechanism called negative feedback. Negative feedback maintains homeostasis. Negative feedback mechanisms are so common in the body that we have a special symbol for them in the book-- a teeter-totter. Every negative feedback mechanism attempts to hold some variable-- for example, body temperature-- as close to a certain value as possible. This value is called the set point. When the variable changes in one direction, negative feedback brings the variable back toward the set point. Every negative feedback mechanism has three components; a receptor that senses the value of the variable, a control center that decides how to respond to a change in the variable, and an effector that can adjust the value of the variable back toward the set point. For example, temperature-sensitive cells in the skin and the brain acquire data about body temperature. A control center in the brain interprets this information and determines a response, and effectors, such as sweat glands and skeletal muscles, carry out the response. These three components are connected together by two pathways; an afferent pathway that carries sensory information from the receptor to the control center and an efferent pathway that carries information from the control center to the effector. To help you remember this, think about it this way-- afferent information approaches and efferent information exits the control center. Let's see how this works. One, a stimulus produces a change in the variable away from the set point. Two, the receptor detects the change. Three, information sent along the afferent pathway access input to the control center. Four, output from the control center is information sent along the efferent pathway to the effector. Five, the effector creates a response that reduces the effect of the stimulus and returns the variable to the set point-- its homeostatic value. Let's return to the example of body temperature. A stimulus-- heat, in this case-- increases body temperature, tipping the body out of homeostatic balance. Temperature-sensitive cells in the skin and brain act as receptors and detect this change. They transmit sensory information along afferent pathways to the control center-- in this case, the thermoregulatory center in the brain. The control center, having decided that the body is too hot, sends instructions along efferent pathways to the effectors. The effectors, in this case, are sweat glands that release water onto the surface of the skin. As the sweat evaporates, body temperature falls, eliminating the stimulus and restoring homeostatic balance. This feedback mechanism also works if the stimulus is cold-- body temperature falls, temperature-sensitive cells detect this change, and signal the control center in the brain. Faced with a different change, the control center makes a different choice to right the balance. It sends instructions to a different set of effectors-- not sweat glands that would cool the body further but skeletal muscles. Shivering generates heat, which raises body temperature, eliminates the stimulus, and restores homeostatic balance. You can see from these examples how negative feedback mechanisms maintain homeostasis. Given our example of the negative feedback that controls body temperature, you might wonder how it is that your body can raise its temperature when you have a fever in response to an infection. What happens is that the infection causes the set point in the control center in the brain to change. As a result, body temperature is now colder than the new set point, then the body generates and conserves heat so the temperature rises to match the new set point. It's just like turning up the thermostat in your house and having the heat turned on. Which of the following do you think will happen when your fever subsides? Is it (a) your set point returns to normal and then you shiver; (b) your set point returns to normal and then you sweat; (c) your set point remains elevated and you shiver; or (d) your set point remains elevated and you sweat? The correct answer is (b). Your set point returns to normal. And because your temperature is now higher than the set point, you sweat to bring your temperature down to the normal set point. As you've seen, negative feedback mechanisms play an important role in maintaining homeostasis. That is, they allow us to maintain the internal environment of the body within the limits that support life. You will encounter many more examples of homeostatic mechanisms as we investigate each of the body's systems. You will also see that the loss of homeostasis leads to most diseases.


The respiratory system consists of the nasal cavity, pharynx, larynx, trachea, bronchi, and lungs.



The respiratory system contains the __________.


Introduction and the Principle of Complementarity


Blood clotting is a normal response to a break in the lining of a blood vessel, and it is an excellent example of an essential body function controlled by positive feedback.



Which of the following is an example of a positive feedback mechanism?


Regional Terms, Directional Terms, Planes & Sections


because they allow us to explain where one body structure is in relation to another



because they enable us to identify an extreme anatomical variation in a human body



Directional terms allow us to explain where one body structure is in relation to another.



because they allow us to designate specific areas within major body divisions



because they allow us to accurately describe the position of a human body



Why are directional terms so important?


Abdominal Quadrants and Regions 

The terms cranial and superior are synonymous, and they mean "toward the head end or upper part of a structure or the body; above." As such, the chin is cranial, or superior, to the navel.


The navel is superior (cranial) to the chin.



The chin is superior (cranial) to the navel.



Which of the following statements is correct?


Four Abdominal Quadrants and Nine Abdominal Regions

Homeostasis: Regulating Blood Sugar

The sugary snack you devour enters your digestive system and is broken down to simple sugars like glucose. Glucose enters the bloodstream, causing an increase in blood glucose levels. But various mechanisms bring blood glucose back down to its normal level, the set point. This is an example of homeostasis, the bodyâs tendency to maintain relatively constant internal conditions. Hormones produced by the pancreas regulate blood glucose levels. Let's zoom in. When blood glucose levels are high, glucose molecules leave the blood and enter beta cells in the pancreas. The beta cells respond by releasing the hormone insulin. Insulin enters the bloodstream and is transported to cells all over the body. Let's see what happens in the liver. Insulin binds to receptors on liver cells. This causes the cells to take in more glucose. Inside the liver cells, glucose is converted to glycogen, a storage molecule. Blood glucose levels decrease as glucose is taken up by liver cells and other body cells. As a result, less and less insulin is released by the pancreas, and blood glucose levels stabilize at their set point. This is an example of how negative feedback maintains homeostasis. What happens if youâve skipped lunch, and your blood glucose levels are low? Letâs zoom into the pancreas again. When blood glucose levels are low, alpha cells in the pancreas release the hormone glucagon. Glucagon enters the bloodstream and acts on target cells in the liver. Glucagon binds to receptors on the liver cells, signaling the liver cells to break glycogen down to glucose. Glucose is released, and blood glucose levels increase. As a result, less glucagon is released by the pancreas, and blood glucose levels stabilize at their set point. In this way, two hormones with opposing effects allow the body to maintain homeostasis of blood glucose levels. In diabetes, the body is unable to maintain homeostasis of blood glucose levels. In type 1 diabetes, the beta cells of the pancreas are destroyed by the immune system, and so no insulin is produced. In type 2 diabetes, the pancreas produces insulin but target cells do not take up glucose. In both types of diabetes, when blood glucose levels rise, cells do not take up the additional glucose, and so blood glucose remains high. This example shows the importance of homeostasis in everyone's life. Copyright Â© 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings


Tissues are groups of similar __________ that have a common function.


Positive feedback is not part of homeostatic control systems.


Positive feedback is not part of homeostatic control systems.



Which of the following is NOT one of the three components of homeostatic control systems?



The retroperitoneal cavity contains the kidney.



The cavity between articulating bones at most joints is known as the __________.



The walls of the ventral body cavity and the outer surfaces of the organs it contains are covered by a thin, double-layered membrane, the serosa, or serous membrane.



A serosa, or serous membrane, can be found within which one of the following body cavities?



a horizontal plane that divides the body into anterior and posterior parts



A sagittal plane is a vertical plane dividing the body into right and left parts.



a horizontal plane that divides the body into superior and inferior parts



a vertical plane that divides the body into anterior and posterior parts



a vertical plane that divides the body into right and left parts



Which of the following best describes a sagittal plane?



This is the medical term for the center region of the trunk around the umbilicus.



This is the medical term for the upper right corner of the trunk, which runs alongside the thoracic cage.



This is the medical term for the center, lowermost area of the trunk.



If you know that the appendix lies in the right lower part of the trunk, you could also say it lies in the __________.



blood clotting when the lining of a blood vessel is injured



decreased urine production when the blood pressure drops



This is an example of a negative feedback system.



sweating to help lower elevated body temperature



an increased respiratory rate when blood pH is elevated



Which of the following events is NOT the result of a negative feedback mechanism?


Introduction to Principle of Complementarity


The variable changes in a direction opposite to that of the initial change.



In positive feedback mechanisms, the result or response enhances the original stimulus so that the response is accelerated.



The result or response enhances the original stimulus, and the response is accelerated.



The output shuts off the original stimulus or reduces its intensity.



They mostly function to keep blood chemicals within narrow ranges.



Which of the following is true of positive feedback mechanisms?



The sternal region is superior to the umbilical region.



The sternal region of the body is __________ to the umbilical region.



The nervous and endocrine systems control all changes in the body.



Which two systems monitor the body for homeostasis?



This is one of the characteristics of the anatomical position.



The body is “standing at attention.”



Which of the following does NOT represent correct positioning when placing the body in the anatomical position?



Olfactory epithelium is housed in the nasal cavity.



The middle ear ossicles are housed in the middle ear cavity.



Which of the following is/are housed in the orbital cavity?



The levels of complexity always begin with cellular and increase from there, ending with organ systems.



Which of the following shows increasing complexity levels?



The frontal, or coronal, plane divides the body into anterior and posterior parts.



The plane that divides the body into anterior and posterior parts is called the __________.


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