Introduction

Chapter 1

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)

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

Levels of Structural Organization

Subatomic Particles – electrons, protons, and neutrons

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.)

Atom – smallest unit of an element (hydrogen atom, lithium atom, etc.)

Continued…

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

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

All organisms share several characteristics of Life

All organisms share several characteristics of life…Continued

Assimilation – Changing substances into different chemical forms

Excretion – Removal of wastes

Absorption – passage of substances across membranes and into bodily fluids

Development – Living things become more complex

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

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

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 rangeSet-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.

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

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

There are 2 types of feedback loops

Body temperature drops below the set-

point (37°C)

thermoreceptors send signals to the hypothalamus

hypothalamus detects the change in temperature

The hypothalamus sends signals to the skeletal

muscles

The skeletal muscles contract rapidly

(shivering) generating body heat

Body temperature returns towards the

set-point.

Stimulus

Receptors

Control CenterEffectors

Negative Feedback

Example of Homeostasis and Negative Feedback

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.

Figure 1.8 The homeostatic mechanism that regulates body temperature

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

Uterine muscles contract. Muscles push baby against cervix.

Baby stretches the cervix

Stretch receptors from cervix

send a signal to the hypothalamus

Hypothalamusdetects stretching of

cervix

Hypothalamus promotes

the secretion of Oxytocin

Oxytosin promotes additional uterine

contractions

Positive feedback cyclechild birth

stimulus

receptor

control center

effectors

positive feedback

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