UAMS PA Physiology Exam 1

How humans and other animals function

Physiology

The abnormal function seen in animal and human disease

Pathophysiology

New methods to treat pathophysiological diseases

Translational research

The property of a system that regulates its internal environment

* Either open or closed

Homeostasis

Predetermined value or range that is the "happy place" or desired point

* Relative to the person and can change over time

Set point

Change in variable being regulated causes responses that moe the variable in a direction opposite of the original change

* Ex: temperature control, regulation of glucose concentration in blood

Negative feedback

Control evaluates the changes and activates the effector to accelerate the original change

* Ex: childbirth and release of oxytocin with contractions that stimulates more contractions

Positive feedback

Uses cues (internal or external) to stimulate changes in anticipation of a change

* Ex: Pavlov's dogs, fear cues cause increase in adrenaline before threat is imminent

Feedforward regulation

ECF

* high Na+ levels; low K+ levels

* 1/3 total body water

* interstitial fluid (75-80%; fluid surrounding cells); plasma (20-25%; fluid portion of blood)

ECF: Na+/K+ levels? how much total body water? segments?

ICF

* high K+ levels; low Na+ levels

* 2/3 total body water

ICF: Na+/K+ levels? how much total body water?

1) regulate passage of substances into and out of cells

2) detect chemical messengers arriving at cell surface

3) link adjacent cells together

4) anchor cells to extracellular matrix

4 functions of cell membranes

Fat-soluble substances (O2, CO2, alcohol)

* NOT WATER-SOLUBLE SUBSTANCES bc lipid bilayer

What goes through the membrane?

1) Peripheral

- not embedded; not covalently bound; easily broken away by mild treatments

2) Integral

- embedded/anchored in membrane

a) transmembrane (span bilayer 1 or more times; touches ECF and ICF)

b) non-transmembrane (embedded but does not span... doesn't touch both ECF and ICF)

Types of proteins in cell membrane

1) Desmosomes (rope-like attachments between cells - strength and connection)

2) Tight junctions (cell membranes of 2 cells fuse together - transcellular across epithelium)

3) Gap junctions (hollow tubes between each cell)

Membrane junctions

Endo - cell taking things in

Exo - cell getting things out - 1) replaces old portions of plasma membrane and 2) gets out membrane-impermeable molecules

Endo/exocytosis

1) Pinocytosis (cell drinking - non-specific)

2) Phagocytosis (cell eating)

3) Receptor-mediated (bringing in a receptor - specific)

Types of endocytosis

Simple diffusion only

What type of transport is not carrier-mediated?

Concentration gradient

What is the driving force of the movement of molecules in diffusion?

1) Diffusion coefficient (how easily something will move across a membrane - relative to molecule; inversely related to molecular radius of solute and viscosity of medium aka bigger molecules move slower, and molecules move slower in a more viscous medium)

2) Membrane properties (thickness, surface area, permeability)

3) Electrochemical gradient (due to charge of ion)

What factors affect the speed of diffusion?

Na+: 140

Cl-: 100

K+: 4

Ca++: 10

HCO3-: 24

Glucose: 70-100

Protein: 0.2

ECF: 290

Extracellular solute concentrations

Bilayer: O2, CO2, fatty acids, alcohols (non-polar)

Protein channels: Na+, K+, Ca++ (ions)

What moves through the lipid bilayer? Through protein channels?

- carrier protein

- conformational change

What does facilitated diffusion require?

1) Saturation (how many solutes in solvent; limited binding sites; rate of transport increases when less solutes present)

2) Stereospecificity (binding sites for solute on transport proteins are stereospecific)

3) Competition (D-galactose and D-glucose both recognized by transport protein; must compete for finite number of receptors; one will inhibit the transport of the other)

What 3 things play a role in carrier-mediated transport (for facilitated diffusion, primary/secondary AT)?

Primary directly uses ATP to move molecules, while secondary indirectly uses ATP to move them

Difference between primary and secondary AT?

1) Na+K+ ATPase pump (3Na+ out, 2K+ in; pump maintains concentration gradient; found everywhere)

2) Ca++ ATPase pump (found in endoplasmic and sarcoplasmic reticulums)

3) H-K+ ATPase pump (found in stomach and kidneys)

Main examples of primary AT?

Inactivation gate always trancedes over the activation gate

Gated channels

*Na+ moves down its gradient, while another solute moves against its gradient --> the Na+ movement gives energy to the other solute to move

1) Cotransport/symport (molecules move in same direction)

2) Countertransport/antiport (molecules move in different directions)

Secondary AT types

Flow of water between two solutions separated by a semipermeable membrane caused by a difference in solute concentration

* aka net diffusion of water across a membrane

Osmosis

Difference in osmotic pressure between two solutions

What drives osmosis?

1) Osmolarity

2) Osmotic pressure

What is osmosis dependent on?

Concentration of osmotically active particles in a solution

* mOsm/l = gC

* g = number of particles/mol in solution

* C = concentration (mmol/L)

Osmolarity

Isosmotic: solutions have the same osmolarity

Hyperosmotic: one solution has a higher osmolarity than other

Hypoosmotic: one solution has a smaller osmolarity than other

* ECF has osmolarity of 285-300 mOsm/L

iso/hyper/hypoosmotic

Describes the ease of which a solute crosses a membrane

σ = 1 --> major water movement; solutes do not go across membrane

σ = 0 --> no water movement; solutes do go across membrane freely

Reflection coefficient (sigma)

- Amount of pressure that needs to be applied to a solution to prevent the inward flow of water through a semipermeable membrane

- Pressure exerted by the movement of solvent molecules through a semipermeable membrane lower to higher solute concentration

Osmotic pressure

Higher

* Bc more particles moving and bumping into each other

____________ concentrations of solute increase osmotic pressure.

Measure of the osmotic pressure gradient between two solutions separated by a semipermeable membrane

Tonicity

Isotonic: same effective osmotic pressures (no osmosis)

Hypertonic: higher effective osmotic pressures than other solns

Hypotonic: lower effective osmotic pressures than other solns

* Water will move from hypotonic solutions to hypertonic solutions

Iso/hyper/hypotonic

Yes!

* Can have the same osmolarity but different tonicities

Can two solutions be isosmotic but not isotonic?

Hyperosmotic; hypertonic

* Results from

1) decreased water intake

2) water loss without proportionate solute loss

3) increased solute intake without proportionate water intake

4) excess accumulation of solutes

5) loss of excessive sweat

6) hyperosmotic volume contraction

Pathophys

* Dehydration: loss of water without loss of solutes

Isosmotic

* Caused by

1) hemorrhage (bc of loss of blood volume)

2) loss of GI tract secretions (vomiting, diarrhea, ileostomy, etc)

* May lead to dehydration and hypovolemic shock

Pathophys

* Dehydration: loss of water and solutes

Hypotonic; hypoosmotic

* Caused by

1) accumulation of solute-free fluid

2) excess antidiuretic hormone (ADH) or intake of large amounts of tap water without balance oslute ingestion (elderly; marathon runner)

3) symptoms largely neurologic bc water shift to brain tissues and dilutes sodium in vascular space

Pathophys

* Fluid excess: excess extracellular water in relationship to solutes

1) Thirst

2) Weight loss

3) Dryness of mouth, throat, face

4) Absence of sweat

5) Increased body temperature

6) Low urine output

7) Postural hypotension (BP bottoms out upon standing)

8) Dizziness and confusion

9) Increased hematocrit

Clinical signs/symptoms of fluid deficit / dehydration

1) Decreased mental alertness

2) Sleepiness

3) Poor motor coordination

4) Confusion

5) Convulsions

6) Sudden weight gain

7) Hyperventilation

8) Signs of increased ICP

9) Mild peripheral edema

10) Low serum sodium

11) Low hematocrit

Clinical signs/symptoms of fluid excess / water intoxication

Isotonic volume excess

* Causes

1) vein obstructions

2) decreased cardiac output

3) endocrine imbalances

4) loss of serum proteins (burns, liver disease, allergic reactions)

Pathophys

* Fluid excess: excess of both solutes and water

1) Weight gain

2) Excess fluid

3) Dependent or pitting edema

4) Increased BP

5) Neck vein enlargement

6) Effusions

7) CHF

8) Signs of increased ICP

9) Low serum sodium

10) Low hematocrit

Clinical signs and symptoms of fluid excess / edema

Diuretics... inhibit Na+ and water reabsorption by kidneys

- K+ also usually lose too quickly --> s/s of K+ loss are muscle weakness, fatigue, cardiac arrhythmias, abdominal distention, nausea/vomiting

How is edema treated?

Measures fractional volume occupied by RBCs

Hematocrit (Hct)

Decreases

If ECF volume increases, Hct _________

Increases

If ECF volume decreases, Hct _________

Hct may be unchanged because water shifts outside of the blood vessel

Hyposmotic expansion (excessive water intake) SHOULD decrease Hct due to dilution of RBC concentration... why may it not?