Lecture 1: Intro to Physiology

What is physiology?

The study and function of organisms

"How's and why's of the body"

Structural Levels of Organization

1. Atoms/molecules (building blocks of matter)

2. Cells (basic unit of life)

3. Tissues (group of cells working together)

4. Organs (several types of tissues combine together to perform a function)

5. Organ systems

6. Organisms

External Environment

Components outside the body

Ex: air, nutrient, water, inorganic ions, urine, feces

Internal Environment

Components inside the body

Ex: cells, fluid.

What are the external and internal environments separated by?

Epithelium

Ex: skin, lining of lungs, intestinal tract, and kidney tubules

Major Concept...

The human body requires contact with the external environment

Problem: not all cells are in direct contact w/external environment

Solution: Fluid compartments -> allow for cell communication

• components to be shared between 2 cells

Fluid compartments of the body: Total Body Water (TBW)

Volume of water contained in all the body's compartments

• All H2O that's part of internal environment (the yellow from diagram Slide 8)

What does TBW include?

1. Intracellular fluid (ICF)

2. Extracellular fluid (ECF)

What is intracellular fluid?

Fluid INSIDE cells

What is extracellular fluid?

Fluid OUTSIDE cells (surrounding cells)

Includes:

• Plasma

• Interstitial fluid (ISF)

What is plasma?

Liquid (non-cellular) portion of blood

• a type of ECF

• “fluid surrounding cells but in blood”

What is interstitial fluid (ISF)?

Fluid (outside the blood) surrounding cells

• a type of ECF

Now that cells can communicate, what is the goal??

Homeostasis!!

What is homeostasis?

Maintenance of a relatively constant INTERNAL environment (balance)

A unifying theme in physiology

Disruption -> disease

Homeostatic Control Systems

Regulatory responses to maintain homeostasis

Classes of Homeostatic Control Systems

1. Intrinsic/Local controls (small scale)

2. Extrinsic/Systemic controls (involves multiple systems)

Intrinsic/Local Controls

Inherent IN an organ

• control @ the local level (organ level)

• regulating by itself

• ex: BV dilating/constricting b/c it senses chemical change

Extrinsic/Systemic Control

Regulatory mechanisms initiated OUTSIDE organ

• uses endocrine and nervous system

• Ex: hormones, action potentials, or neurons to regulate a particular organ

• coordinates response from several organs -> to achieve common goal

Regulated Variables

Conditions regulated by homeostatic control

Ex: Temperature, pH, salinity, dissolved gas concentration, nutrient and waste concentration...

What is a set point?

Range for a regulated variable the body wants to maintain

Ex:

• Body Temperature: 37 C

• Blood glucose: 100 mg/dL

• Blood pH: 7.35-7.45

What happens if you go out of the range?

Error signal

• Deviation from the set point

Homeostatic Response Components

1. Stimulus

   1. Change from set point (error signal)

2. Sensor (Detects stimulus)

   1. Detects stimlulus

3. Integrating Center

   1. Receives input from receptors

   2. Determines needed output to effectors

   3. Usually a part of the nervous system

4. Effectors

   1. Receives output to respond to stimulus

Ex:

• Stimulus = increased glucose

• Sensor and Integrating center: Beta Cells from Pancreas

• Output = Insulin, which binds to effectors

• Effectors = Cells of body -> removes glucose from blood and take into their own cells, which lowers blood glucose

What is Feedback?

Response made after change detected

What are types of feedback?

1. Negative feedback

2. Positive feedback

What is Negative Feedback?

Response moves the system in the opposite direction of initial change

• Stabilizing

• More common

Ex: Body temperature and blood glucose level

What is Positive Feedback?

Response moves the system in the same direction as the initial change

• Directional (until you break the feedback loop, it will continue going in that direction)

• Less common

Ex: Child birth, ovulation, fever, blood clotting

What is diabetes?

Metabolic disease affecting:

• Blood glucose levels (usually higher levels)

• Urine volume (increases)

What are the results of diabetes?

• Excessive thirst (dehydrated)

• Excessive fluid loss

• Eventually all body systems affected

• Ex: increased glucose can damage neurons

What are the different types of diabetes?

1. Diabetes Mellitus Type I

2. Diabetes Mellitus Type II

3. Gestational Diabetes

4. Diabetes Insipidus

What is Diabetes Mellitus Type I?

Inadequate insulin production

• Insulin DEPENDENT

• autoimmune disease

• beta cells don't produce insulin, effector cells fine, must inject insulin

What is Diabetes Mellitus Type II?

Body cells LOSE RESPONSE to insulin

• Non-insulin dependent

• MOST COMMON

• usually happens later on in life

• beta cells okay

• effector cells decreased or damaged (problem w/receptor)

What is Gestational Diabetes?

Temporary loss of sensitivity to insulin due to hormonal changes

• Mimics Type II

What is Diabetes Insipidus?

Inadequate anti-diuretic hormone secretion -> HIGH URINE VOLUME

• RARE

Ex:

• ADH = Vasopressin

• Diuretic = what causes you to urinate

• anti = stops urinating, makes you reabsorb fluids more

• inadequate ADH = will not reabsorb H2O and it will turn into urine

How can you develop diabetes?

Obesity (diet) and Sedentary lifestyle

• High fat content relative to lean body mass

• Body mass index (BMI) 30-39

*BMI = body weight (kg) / height (m)^2

ECF includes all of the following except...

A) ISF

B) ICF

C) plasma

D) all of the above is part of ECF

Homeostasis......

A) Uses only intrinsic control mechanisms

B) Is the maintenance of a relatively constant external environment

C) Is a unifying theme in physiology

D) All of the above

The amount of deviation from a set point is the...

A) error signal

B) regulated variable

C) sensor

D) effector

Which of the following is not true of positive feedback?

A) It is less common

B) It moves the system in the same direction as the stimulus

C) It is stabilizing

D) It includes ovulation

Which type of diabetes results in high urine volume due to inadequate anti-diuretic hormone secretion?

A) Diabetes Mellitus Type I

B) Diabetes Mellitus Type II

C) Gestational Diabetes

D) Diabetes Insipidus