Function: Slow-acting control system; uses hormones to regulate growth, reproduction, and metabolism.
Cardiovascular and Lymphatic Systems (Pg 10)
Cardiovascular System
Heart, Blood vessels.
Function: Heart pumps blood; blood vessels transport blood carrying oxygen, carbon dioxide, nutrients, and wastes.
Lymphatic System
Red bone marrow, Thymus, Lymphatic vessels, Thoracic duct, Spleen, Lymph nodes.
Function: Picks up fluid leaked from blood vessels and returns it to blood; houses white blood cells that direct immune responses against infections.
Respiratory, Digestive, and Urinary Systems (Pg 11)
Respiratory System
Lungs, Trachea, Larynx, Pharynx, Nasal cavity.
Function: Supplies blood with oxygen and removes carbon dioxide from blood.
Digestive System
Oral cavity, Esophagus, Stomach, Small intestine, Large intestine, Rectum, Anus, Liver.
Function: Breaks down food into absorbable units; transports those units and water into the blood for distribution to body cells; substances not absorbed are eliminated as feces.
Urinary System
Kidneys, Ureter, Urinary bladder, Urethra.
Function: Eliminates nitrogenous wastes from the body; regulates water, electrolyte, and acid-base balance of the blood.
Functions: Testes produce sperm and male sex hormones; male ducts and glands aid in delivery of sperm to the female reproductive tract.
Female Reproductive System
Mammary glands (in breasts), Ovary, Uterine tube, Uterus, Vagina.
Functions: Ovaries produce eggs and female sex hormones; uterine tubes serve as the site of fertilization, uterus is where fetal development occurs; mammary glands produce milk to nourish the newborn.
Review Questions (Pg 13)
How does the study of anatomy differ from physiology?
What is the principle of complementarity?
What is the correct sequence of structural levels from simplest to most complex?
What is the smallest unit of life?
Which structural level consists of more than one tissue type?
Which are the two principal control systems of the body? How do they differ in function?
Which organ system regulates the water, electrolyte, and acid-base balance of the blood?
Which organ system contains the cells that direct our immune responses?
Homeostasis
Homeostasis: relatively stable condition of the body’s internal environment.
It is a highly dynamic process (dynamic equilibrium).
Maintained despite changes in the external environment.
Homeostatic control mechanisms function to maintain homeostasis.
The concept underlies health and survival; failures underlie disease processes.
Examples of failures include: non-functional negative feedback systems (e.g., some diabetes cases), stimuli overwhelming negative feedback (e.g., heat stroke), wrong setpoints (e.g., hypertension), chronically activated positive feedback (e.g., heart failure).
Variables and Setpoints (Pg 15-16)
Variable: factors that are controlled and kept within a narrow, stable range.
Setpoint: target value for a variable – the value the body works to maintain.
Setpoints are not fixed values; they can change.
Conceptual representation: let V(t) be the variable value; Vset may vary with time; error e(t) = V(t) - Vset(t) represents deviation that the control system strives to minimize.
Components of Homeostatic Control Mechanisms (Fig. 1.5)
Stimulus produces a change in a variable.
Receptor detects the change.
Input: Information travels along afferent pathway to the control center.
Control Center processes information and determines appropriate response.
Efferent pathway carries information from control center to an effector.
Effector responds to reverse the imbalance and moves the variable toward the setpoint.
The return toward setpoint reduces the initial stimulus; the system returns to balance.
Negative Feedback (Pg 17)
Definition: Homeostatic mechanisms that function to return a variable back toward its setpoint (restores balance).
They prevent severe changes to the body’s internal environment.
Example: Body temperature regulation.
Negative Feedback in Action (Pg 18)
Response to a drop in body temperature:
Stimulus: Cold.
Body temperature falls; receptors (temperature-sensitive cells in skin and brain) detect the change.
Control center (thermoregulatory center in brain) processes signal.
Efferent pathway triggers skeletal muscles to produce heat (shivering).
Effectors raise body temperature toward the setpoint.
Once temperature is restored (setpoint reached), the stimulus ends and shivering stops.
Positive Feedback (Pg 19-20)
Definition: Homeostatic mechanisms that cause a variable to move farther away from its setpoint.
The response amplifies the imbalance; occurs in infrequent events and does not require continuous adjustments.
Example: Formation of a platelet plug to stop bleeding.
Positive feedback cycle (summary):
1) Break or tear in a blood vessel wall initiates the process.
2) Platelets adhere to the site and release chemicals.
3) Released chemicals attract more platelets.
4) Platelet plug is formed.
5) The cycle ends when the plug is fully formed.
Maintenance of Homeostasis (Pg 21)
Homeostasis is essential for health and survival.
Failures to maintain homeostasis underlie disease processes:
Non-functional negative feedback systems (e.g., type I & II diabetes).
Stimulus may overwhelm a negative feedback mechanism (e.g., heat stroke).
Establishing the wrong setpoint (e.g., hypertension).
Chronically activated positive feedback system (e.g., heart failure).
Review Questions (Pg 22)
What is homeostasis?
What are the three components of homeostatic control mechanisms? What is each component’s function?
How does negative feedback differ from positive feedback?
Calcium levels in Doug’s blood drop below set point. The hormone PTH is released which acts on bones. The bones release stored calcium into the blood allowing calcium levels to rise back to set point. – What is the stimulus? – What is the effector? – What is the response? – Is this an example of negative or positive feedback?