Lecture: Chapter 1 - Homeostasis
I. Organization of Life
A. Structure:Function and Function:Structure
1. Anatomy - study of the structure of cells, tissues, organs, organisms
2. Physiology - study of how cells, tissues, organs, organisms function
3. Darwin - Origin of the Species (1858)
a. Structure and Function are intimately linked
b. Structure dictates the Function
1. Finch beaks and food on the Galapagos
c. Evolution "selects" most favorable Functions
1. kidneys/skin of various organisms
a. kangaroo rat - desert
b. human - land
c. sea bass - salty ocean water
d. Environment and competition "naturally" select genes that give rise to Structures that have favorable
Functions to improve the viability of each species
B. Organization of Living Things
1. principles of matter/energy
2. atoms -> molecules
3. complex organic molecules
4. organelles -> cells
5. tissues
6. organs
7. organ/body systems
8. organism (Physiology/Anatomy)
(Physics)
(Chemistry)
(Biochemistry)
(Cellular Biology)
(Histology)
(Physiology/Anatomy)
(Physiology/Anatomy)
*** all fields overlap and contribute to each other
II. Basic Functions of Organisms
A. Maintenance of Boundaries - separation of organism from outside world
a. virus - protein coat around DNA/RNA interior
b. cell - cell membrane (semipermeable - selective)
c. organism - skin
B. Movement - ability to move self and materials
a. cells - cilia and flagella (sperm)
b. humans - muscle cells (contractility) & bone
C. Responsiveness (Irritability) - respond to both Internal and External changes
a. nervous system - quick response to change
b. endocrine system - medium/longer changes
D. Digestion - breaking down foodstuffs to useable/absorbable form
a. digestive system - breakdown/absorb essential materials
E. Metabolism - all chemical reactions that occur in cells & body
a. anabolism - synthesizing larger molecules
b. catabolism - breaking down large molecules
c. regulated primarily by endocrine hormones
cellular respiration - breaking bonds of larger molecules for useable energy currency (ATP)
a. digestive system - mainly carbohydrate & fats
b. respiratory system - oxygen and carbon dioxide
c. cardiovascular system - distribution of nutrients and gases
glucose + oxygen -> carbon dioxide + water + ENERGY (stored in ATP)
F. Excretion - removing all types of waste from the body
a. digestive system - unused foodstuffs
b. urinary system - nitrogenous wastes (urea) and electrolyte (salt) balance
c. respiratory system - carbon dioxide
G. Reproduction - creating more organisms of the same species
a. virus - depends on cells for their machinery
b. cells - the process of division (mitosis)
c. human - sexual (sperm and egg)
i. regulated by hormones (especially female)
H. Growth - increase in size of cell, organ, or organism
a. number of cells can increase (mitosis)
b. size of cells can increase (fat cells)
III. Basic Biological Needs of Humans
A. Nutrients - molecules for structure and energy
1. carbohydrates - primary energy source & structural
a. glycogen, sugars (glucose)
2. proteins - primarily structural & for signaling (hormones and receptors)
a. 20 amino acids are basic building blocks
b. actin and myosin microfilaments of muscle
c. receptors for hormones/neurotransmitters
d. neuropeptides (enkephalins of nervous system)
3. fats (lipids) - insulation, energy, structure
a. major component of membranes (phospholipids)
b. highest energy content by weight (calories)
4. vitamins - act as cofactors for enzyme functioning
5. minerals - essential for signaling and structure
a. nerve signals - Na+, K+, Ca++, Clb. carry oxygen - Fe++ in hemoglobin
c. bone - Ca++ Phosphates
B. Oxygen - essential for maximum energy gain from food
1. cellular respiration depends on oxygen
2. nervous system alone uses 25% of all oxygen in humans
C. Water - essential for cellular reactions and transport
D. Body Temperature - essential for cellular reactions
1. most human enzymes work best at 37C (98F)
E. Atmospheric Pressure - for proper absorption of oxygen
Physiology is the study of how organisms separate self and non-self; move; respond to
internal and external changes; digest, metabolize, and excrete materials; reproduce; and
grow.
This is achieved by maintaining a proper BALANCE both internally and with the outside world.
IV. Homeostasis
A. Homeostasis - maintaining relative constancy in response to internal and external changes
- dynamic process; changing but relatively constant within limits
- concerns all factors relating to well being of organism (see above)
- regards maintaining internal environment of body due to internal and external changes
1. Homeostasis refers especially to maintenance of proper conditions for:
a. oxygen (O2) and carbon dioxide (CO2) levels
b. levels of nutrients in blood (e.g. glucose)
c. electrolyte /salt balance and osmotic pressure (fluid levels)
d. acid-base balance (pH)
e. temperature
f. pressure of body cavities (especially lungs)
Examples of homeostatic mechanisms:
1. proper nutrient levels in the blood
a. insulin/glucagon - blood glucose levels
2. proper heart rate and blood pressure
a. adrenaline - response to stimuli
3. removing wastes from the blood
a. kidneys - nitrogenous wastes (urea)
b. respiratory - carbon dioxide
4. maintaining proper oxygen levels in blood
a. brain and respiratory - adjust breathing rate
5. body posture and simple muscular reflexes
a. nervous system and muscular system
B. General Characteristics of Homeostatic Control Mechanisms
1. Nervous & Endocrine Systems are general controls
2. Basic Organization of Control Mechanisms
a. receptor - monitors internal/external stimuli
sends info to control center via afferent path
b. control center - analyzes info as it compares to a "set point" for that particular variable
1. variables may include: glucose level, heart rate, blood pressure, urea concentration,
oxygen level, tension on a muscle.
c. effector - physiological mechanism acting from the control center via efferent path
C. Negative Feedback Mechanisms
1. control mechanism DECREASES intensity of condition to bring back to "set point"
example: regulation of glucose levels in blood
a. person eats a candy bar with lots of sugar
b. glucose levels in the blood rise rapidly
c. receptors sense increase in blood sugar
d. control center calls for reduced blood sugar
insulin is secreted into the blood stream
e. insulin causes effector cells (liver & muscle) to absorb glucose and store it as glycogen
- glucose levels return to normal (0.9 mg/ml blood)
D. Positive Feedback Mechanisms (cascade - like a snowball effect)
1. control mechanism INCREASES intensity of condition - causing a "domino" effect
example: labor contractions during birth
a. baby rotates into cervix causing pressure
b. receptors sense increased muscle tension
c. control center calls for release of oxytocin, causing muscles (effectors) to contract more
d. increased muscle tension causes receptors to continue the message to the control center
e. more oxytocin is released
f. loop continues until baby is delivered and the stimulus is no longer present
In Physiology, we study how each of the organ systems work to provide survival needs
of organism and maintain homeostasis of each of the essential variables !!!!!!