The document discusses the levels of structural organization in the human body from subatomic particles to organisms. It also describes homeostasis as the process by which the internal environment is maintained through regulatory feedback loops. There are two main types of feedback loops - negative feedback loops which reduce deviations from the set point, and positive feedback loops which increase deviations from the set point in a short term manner. As an example, negative feedback is used to maintain body temperature, while positive feedback increases uterine contractions during childbirth to push the baby through the cervix.

2. The language of anatomy and physiology is usually derived
from Greek or Latin origins.
Anatomy: Study of the structures of the human body
(Greek: ana = up; tome = to cut)
Physiology: Study of the functions of the organs
(Greek: physis = nature; logia = to study)

3. Today we know that all matter, including the human body, is
composed of tiny particles called atoms.

4. Levels of Structural Organization
Subatomic Particles – electrons, protons, and neutrons
Atom – smallest unit of an element
(hydrogen atom, lithium atom, etc.)
Molecule – particle of 2 or more atoms
(water molecule, glucose molecule, etc.)
Macromolecule – very large molecule
(protein, DNA, etc.)
Organelle –carry on specific activities within a cell
(mitochondrion, Golgi apparatus, nucleus, etc.)
Continued…

5. Levels of Structural Organization…continued
Cell –basic unit of life
Humans = 50 -100 trillion cells
(muscle cell, nerve cell, etc.)
Tissue – group of similar cells that perform a specialized function
(epithelia, connective, muscle and nerve)
Organ – Groups of different tissue
(skin, femur, heart, kidney, etc. )
Organ System – Group of organs that function together
(skeletal system, digestive system, etc.)
Organism – the human

6. All organisms share several characteristics of Life
Responsiveness – organisms are able to detect changes in the
environment and respond to them
Metabolism – is the sum of all chemical reactions in a cell
Reproduce – DNA replication, Cell Division, Sexual Reproduction
Growth – increase in size of body or organ
Respiration – releases energy from food
Digestion – break down of food

7. All organisms share several characteristics of life
…Continued
Development – Living things become more complex
Absorption – passage of substances across membranes and
into bodily fluids
Assimilation – Changing substances into different chemical forms
Excretion – Removal of wastes

8. Humans depend on 5 requirements for life.
Water - Essential for transportation & metabolic processes
Food - Source of energy and used as building blocks for growth
and repair
Oxygen – required to release energy from metabolism
Heat – form of energy, drives chemical reactions
Pressure – a force required for breathing and circulation

9. Homeostasis
Homeostasis is a process in which a stable internal environment of
an organism is maintained.
Homeostatic Control Mechanisms – monitor the internal
environment and corrects conditions as needed.
Vital Signs measure the ability to
maintain homeostatic mechanisms: e.g.
heart rate, blood pressure, pH, body
temperature, respiratory rate, ect.
Vital signs assess the conditions
of homeostatic mechanisms

10. 3 components of a Homeostatic Mechanism
Receptor – monitors the environment and provides information about
changes in the conditions
Control Center – Region in body that sets the normal range
Set-Point: target value that is maintained by the control center
(e.g. Body temperature = 98.6 F, or 37 C)
Effector – Produces a response that alters conditions in the environment
(usually a muscle or a gland)
*The control center receives input from receptors and
sends output to effectors when changes are needed.

11. Control of Homeostatic Mechanisms
Homeostasis is maintained through regulatory processes called
feedback loops
A feedback loop is a cycle of events in which a body
condition (such as body temperature) is continually
monitored and adjusted to be within specific limits
Figure 1.6 a homeostatic
mechanism monitors a
particular aspect of the internal
environment and corrects any
changes back to the value
indicated by the set-point

12. There are 2 types of feedback loops
1. Negative Feedback Loop –reduces the deviation of conditions
from a set-point
• Most common way to maintain homeostasis
• Effectors act to lessen or counteract the stimulus
2. Positive Feedback Loop –increases the deviation of
conditions from a set-point
• Effectors respond by reinforcing the stimulus
• Drives systems away from equilibrium (runaway train)
• Not a way to maintain homeostasis

13. Example of Homeostasis and Negative Feedback
Stimulus
Negative Feedback
Body temperature drops
below the set-point
(37°C)
Body temperature
returns towards the setpoint.
Effectors
The skeletal muscles
contract rapidly (shivering)
generating body heat
Receptors
thermoreceptors send
signals to the
hypothalamus
Control Center
hypothalamus detects the
change in temperature
The hypothalamus sends
signals to the skeletal muscles

14. Control of Homeostatic Mechanisms
Negative Feedback restores conditions back towards set-point.
As conditions return towards normal, negative feedback gradually
shuts down the effectors. This prevents a correction from going to far.

15. Figure 1.8
The homeostatic mechanism that
regulates body temperature

16. Positive Feedback
As a stimulus moves conditions away from the set-point,
positive feedback further increases the deviation.
Positive feedback produces unstable conditions that are usually
short-lived.
Example: The increase in uterine contractions during childbirth

17. effectors
Uterine muscles contract.
Muscles push baby against cervix.
positive feedback
stimulus
Oxytosin promotes additional
uterine contractions
Baby stretches the cervix
receptor
Stretch receptors from cervix
Hypothalamus promotes
send a signal to the
hypothalamus
the secretion of Oxytocin
control center
Hypothalamus
detects stretching of
cervix

18. Positive Feedback & Childbirth
Positive feedback continues to increase the strength of contractions.
The cycle ends only after the baby is born and the cervix is no longer
stretched.
End of Chapter 1