Physiology Exam 1

Modules 1A-1E

Physiology

the study of the functions of a living organism (how)

Principles of Physiology

1. Homeostasis is essential for health and survival

2. The function of organ systems are coordinated

3. Most functions are controlled by multiple regulatory systems, often working in opposition

4. Information flow between cells, tissues, and organs is an essential feature of homeostasis and allows for integration

5. Controlled exchange of materials occurs between compartments and across cellular membranes

6. Physiological processes are dictated by the laws of chemistry and physics

7. Physiological processes require the transfer and balance of matter and energy

8. Structure is a determinant of function

Levels of organization

Atoms → Molecules → Cells → Tissues → Organs → Organ Systems → Organism

Gap Junction signaling

Signal directly from cell to cell

Synaptic signaling

signal across synaptic cleft via neurotransmitters

Paracrine and Autocrine signaling

signal by diffusion in interstitial fluid (neighbor and self)

Endocrine signaling

signal by circulating body fluids via hormones

Circulatory system

Transport of blood throughout the body

Digestive system

Digestion and absorption of nutrients and water; elimination of wastes

Endocrine system

Regulation and coordination of many activities in the body involving hormones

Immune system

defense against pathogens

Integumentary system

Protection against injury and dehydration

Lymphatic system

Collection of extracellular fluid for return to blood; participation in immune defenses; absorption of fats from digestive system

Musculoskeletal system

Support, protection, and movement of the body

Nervous system

Regulation and coordination of many activities in the body involving neurotransmitters

Reproductive system

production and transfer of sperm; production and provision of eggs

Respiratory system

Exchange of CO2 and O2; regulation of H+ concentration in body fluids

Urinary system

Regulation of plasma composition through controlled secretion of ions, water, and organic wastes

ICF

67%

ISF

26%

Plasma

7%

Exchange Via GI Tract

Absorption: lumen to blood (nutrients & vitamins)

Secretion: blood to lumen (Bile salts & bilirubin)

Exchange Via Kidney

Filtration: blood to lumen (nutrients, water, ions)

Secretion: blood to lumen (K+ & wastes)

Reabsorption: lumen to blood (nutrients & water)

ICF K+

150 mM

ECF K+

5 mM

ICF Na+

15 mM

ECF Na+

145 mM

ICF Cl-

7 mM

ECF Cl-

100 mM

Homeostasis

the mechanism by which organisms maintain a relatively constant steady state of internal environment

Body temp set point

37 degrees C

Blood glucose set point

5.6 mM

Blood pH set point

7.4

Mean Arterial Pressure set point

93 mmHg

ECF local homeostasis

restricted to one tissue space, uses paracrine and autocrines

ECF systemic homeostasis

involves entire body, uses neurotransmitters and hormones

Homeostatic Process

Stimulus → Receptor → Afferent Pathway → Integrating Center → Efferent Pathway → Effector → Response

Reflect Receptor

Detects change using threshold stimulus

Afferent Pathway

Carries info from reflect receptor to integrating center (only NS)

Integrating Center

Receives stimulus, analyzes information, and generates an appropriate response (ES: Endocrine gland, NS: Brain or Spinal Cord)

Efferent Pathway

Carries commands from integrating center to effectors (ES: Hormones, NS: neurotransmitters)

Effector

Any cell affected by the efferent pathway (change in function)

Response

local or systemic

Negative feedback

the effector response corrects the variable and brings it back to the set point, which stops activation of the reflex receptor and the reflex loop

Positive feedback

mechanism that amplifies an initial stimulus, pushing a process to completion by increasing the output in the same direction

The plasma membrane

regulates exchange between ECF and cytoplasm, detects chemical signals in the extracellular environment, links adjacent cells together

Phospholipids

Hydrophilic heads and Hydrophobic tails creating the plasma membrane

Membrane Cholesterol

Interacts with the fatty acid chain region of phospholipids and keeps the fluidity of the membrane in an immediate range when exposed to substances that tend to increase membrane fluidity

Phospholipid tails

Saturated or Unsaturated. Saturated is more tight and reduces membrane fluidity

Membrane permeable substances

Small non polar molecules (Gases, Fatty acids, Urea, Water)

Non-permeable substances

Large or polar molecules (Glucose, Ions, Amino Acids, Proteins)

Equilibrium Potential

E=61/charge LOG ECF/ICF

Resting membrane potential

-70 mV

K+ equilibrium potential

-90mV

Na+ equilibrium potential

+60mV

Cl- equilibrium potential

-70mV

Ca2+ equilibrium potential

+122mV

Why is resting membrane potential -70mV?

at rest, the membrane is more permeable to K+ than Na+ due to the presence of K+ leak channels being low force, but high concentration compared to Na+ leak channels being high force, but low concentration. This allows resting potential to be closer to K+ equilibrium.

Depolarizing

Less negative

Hyperpolarizing

More negative

Repolarizing

Return to -70

Types of Passive Transport

1. Simple diffusion

2. Facilitated Diffusion

3. Osmosis

Types of Active Transport

1. Primary

2. Secondary

3. Vesicular

Simple diffusion

unassisted movement of a substance across bilayer down the gradient (H→L)

Rate of simple diffusion increases when…

1. concentration gradient increases

2. membrane surface increases

3. membrane thickness decreases

4. molecule is smaller

5. lipid solubility of the molecule is greater

6. temperature increases

Facilitated Diffusion: carrier proteins

Protein assisted movement of a substance across the membrane down a gradient (H→L)

GLUT1

most cells; basal glucose uptake

GLUT2

liver, kidney, pancreas, small intestine; carrier for glucose & fructose

GLUT4

skeletal and cardiac muscle; insulin responsive

Facilitated diffusion: ion channels

ion channels are transmembrane proteins that create a pore for passive transport of ions with their electrochemical gradient

ion channel gating mechanisms

a) ligand binding (doorbell)

b) change in membrane potential (traffic light)

c) post-translational modification

d) stretch/stress (bladder)

Osmosis

the passive movement of water due to the solute concentration

Osmolarity

molarity x number of particles

Intracellular and Extracellular Osmolarity

~300 mOsM

Tonicity

determines change in shape of a cell when places in a solution (only looks at trapped solutes)

iso-

300 mOsM

hypo-

<300 mOsM

hyper-

>300 mOsM

Hypotonic

Increase Volume

Hypertonic

Decrease Volume

Isotonic

No change

.9% Saline

Isotonic

5% Dextrose in .9% Saline

Isotonic

5% Dextrose in water

Hypotonic

.45% Saline

Hypotonic

5% Dextrose in .45% Saline

Hypotonic

Why would it be beneficial to use an isotonic solution?

to keep a patient hydrated

What is the value of using a hypotonic solution?

extreme dehydration

active transport

transmembrane proteins that move ions and hydrophilic molecules across the plasma membrane up a gradient (L→H), which requires a source of energy

Uniporter

one transporter

Symporter

two transporters, same direction

Antiporter

two transporters, opposite direction

Primary Active Transport

transports a substance against their gradient, requires a protein, requires energy

Na+/K+ pump

primary; antiporter; 321 NOKIA

H+/K+ pump

primary; antiporter

Ca2+ pump

Primary; uniporter

Secondary Active Transport

Coupled transport, with at least one substance against its gradient while one moves with its gradient

Na+/Ca2+

Secondary; antiporter

Na+/K+/2Cl-

Secondary; symporter

Na+/amino acids

Secondary; symporter