physiology test 1

what are levels of organization

how molecules, cells, tissues, and organs work together to make animals function

what are the different levels of organization focused on in physiology

• molecules, cells, tissues, organs, organ systems, organisms, and populations of one species

• we are especially focusing on tissues, organs, and organ systems

what are the key systems in physiology

• communication systems (nervous, endocrine)

• internal transport systems (circulatory, lymphatic)

• input/output systems (digestive, urinary, respiratory)

• mobility systems (musculoskeletal)

• immune systems

• reproductive systems

how do organisms living in different external environments maintain the same internal requirements

• regulate the characteristic using energy

• the cells inside of an organism are only exposed to a regulated internal environment, not to the harsh external environment

what is an external environment

anything (air, fluid, solid) that is outside of our barrier cells, including things in the hollow tubes of our digestive, excretory, and respiratory systems

what is the internal environment

any extracellular fluid (ECF) within our bodies that surrounds and is in direct contact with non-barrier cells

describe barrier cells

protective cells or epithelium that is a barrier from the external environment

describe the extracellurlar fluid (ECF)

the internal environment of the body (plasma and fluid)

describe epithelial cells

• the barrier to and allow for exchange with the internal environment

• absorption and secretion

• important for the immune system

describe how epithelial cells aid in absorption and secretion

transporting epithelia selectively move substances between a lumen and the ECF

label the lines of the epithelial cells

1. lumen of intestine or kidney

2. apical membrane

3. microvilli

4. tight junctions

5. basolateral membrane

6. extracellular fluid

what are tight junctions

• a transporting epithelium prevent movement between adjacent cells

• substances must instead pass through the epithelial cell, crossing two phospholipid cell membranes as they do so

describe how epithelial cells are important for the immune system

• protective epithelia have many stacked layers of cells that are constantly being replaced

• example: layers in skin

what are the two fluid compartments of the body

1. extracellular fluid

2. intracellular fluid

what is included in the extracellular fluid compartment

• interstitial fluid

• blood plasma

• cerebral spinal fluid (CSF)

• lymph fluid

• divided into the plasma and interstitial fluid and materials moving between cells and ECF must cross the cell membrane

what is included in the intracellular fluid compartment of the body

cytosol

what does it mean by the internal environment does not equal the intracellular fluid, cells, or cytoplasm

• the composition of our internal environment is highly regulated with each having its own distribution

• when the ECF compostion changes outside of an acceptable range compensatory mechanisms activate to return the fluid to its normal state

• regulated variables include: ion, nutrient, and energy molecule concentrations; pH, gases, temperature, etc

describe the banana in the ocean analogy

• the ocean is the ECF with high concentrations of Na+, Cl-, and HCO3-

• the banana is the cell that is K+ rich

• the peanut butter is proteins and anions

• the distribution is important for membrane dynamics

describe the law of mass balance

• if the amount of a substance in the body is to remain constant, any gain must be offset by an equal loss (output has to equal input)

• mass balance = (existing body load) + (intake or metabolic production) - (excretion or metabolic removal)

• regulation doesn’t mean no change, it means no net change

what is equilibrium

• a state in which opposing forces or influence are balanced

• an animal’s body is NEVER fully at equilibrium with the environment

what is homeostasis

• the composition of the body compartments are relatively stable and within the range required by cells for life

• O2, CO2, osmolarity, BP, NaCl, temperature, glucose

what are the anatomical body compartments

• cranial cavity

• thoracic cavity

  • plueral sac surrounding the lungs

  • pericardial sac surrounding the heart

• diaphragm

• abdominopelvic cavity

  • abdominal cavity

  • pelvic cavity

what are the different functional body fluid compartments

• extracellular fluid (lives outside the cells)

  • blood plasma (extracellular fluid inside blood vessels)

  • interstitial fluid (surrounds most cells)

• cells (intracellular fluid, ICF)

describe how all compartments are separated by membranes

• the pericardial sac is a tissue that surrounds the heart

• tissue membranes have many cells that are supported by connective tissues

• each cell has a cell membrane surrounding it

• phopholipid bilayers create cell membranes

describe how membranes are composed of a lipid bilayer

• phospholipids have 2 fatty acids and a phosphate group

• cholesterol and phospholipids are important components of animal cell membranes

• membrane phospholipids can form bilayers (sheets), micelles (droplets of phospholipids), liposomes (have an aqueous center)

• they arrange themselves so that their nonpolar tails are not in contact with aqueous solutions such as extracellular fluid

describe how size and charge affect the rate of diffusion across a membrane

• hydrophobic molecules (O2, CO2, N2) easily pass through

• small, uncharged polar molecules (H2O, indole, glycerol) somewhat easily pass through

• large, uncharged polar molecules (glucose, sucrose) rarely pass through and mostly reflect

• ions (anything with a charge) almost never pass through

describe how the body is in osmotic equilibrium and chemical disequilinrium (homeostasis)

the ECF and ICF are in osmotic equilibrium but have very different chemical compositions

describe osmosis

• the passive movement of H2O across a semi-permeable membrane from an area of low SOLUTE concentration to high SOLUTE concentration

• direcetion of water is determined by the concentration of impermable solutes on either side of the membrane

describe what will happen to the image with respect to osmosis

• the two comartments are separated by a membrane that is permeable to water but not glucose and solution B is more concentrated than solution A

• water moves by osmosis into the more concentrated solution and stops when concentrations are equal

describe osmotic pressure

the amount of physical pressure that must be applied to oppose osmosis

describe the molariity

the number of molecules of EACH solute in solution per unit volume (M)

describe the osmolarity

total concentration of ALL solute PARTICLES in solution per unit volume (OsM)

given the M, calculate the OsM of 1M glucose, 1M glucose and 2M sucrose, and 1M NaCl

• 1M glucose: 1 OsM

• 1M glucose and 2M sucrose: 3 OsM

• 1M NaCl: 2 OsM

what are the three types of tonicity

• hypotonic

• isotonic

• hypertonic

describe a hypotonic solution

less solute in solution than in the cell so the cell blows up

describe an isotonic solution

the amount of solute in the solution and in the cell is the same so the cell is turgid

describe a hypertonic solution

more solute in the solution than in the cells so the cell shrinks

what are the rules for osmolarity and tonicity

1. assume that all intracellular solutes are nonpenetrating (won’t freely pass membranes)

2. compare osmolarities before the cell is exposed to the solution (at, equilibrium, the cell and solution are always isosmotic)

3. tonicity of a solution describes the volume change of a cell at equilibrium

4. determine tonicity by comparing nonpenetrating solute concentrations in the cell and the solution. net water movement is into the compartment with the higher concentration of nonpenetrating solutes

5. hyposmotic solutions are always hypotonic

describe diffusion

• the passive movement of solutes from an area of higher concentration to an area of lower concentration

• does not require any external concentration

• happens with or without a barrier

• molecular movement continues after reaching equilibrium, just not NET movement

describe Fick’s Law of Diffusion

the rate of diffusion is porptional to (surface area)*(concentration gradient)*(membrane permeability)

• rate of diffusion changes based on the composition of lipid layer, membrane surface area, lipid solubility, molecular size, membrane thickness, and the concentration gradient

what are the general properties of diffusion

1. diffusion uses the kinetic energy of molecular movement and does not require an outside energy source

2. molecules diffuse from an area of higher concentration to an area of lower concentration

3. diffusion continues until concentrations come to equilibrium (however molecular movment continues after equilibrium has been reached)

4. diffusion is faster

   1. along higher concentration gradients

   2. over shorter distnces

   3. at higher temperatures

   4. for small molecules

5. diffusion can take place in an open system or across a partition that separates two systems

6. the rate of diffusion through a membrane is faster if

   1. the membrane’s surface area is larger

   2. the membrane is thinner

   3. the concentration gradient is larger

   4. the membrane is more permeable to the molecule

7. membrane permeability to a molecule depends on

   1. the molecule’s lipid solubillity

   2. the molecule’s size

   3. the lipid composition of the membrane

what are the types of epithelia

• exchange epithelium

• protective epithelium

• secretory epithelium

• transporting epithelium

• ciliated epithelium

describe exchange epithelium

the thin, flat cells of exchange epithelium allow movement through and between cells

describe the protective epithelium

have many stacked layers of cells that are constantly being replaced

describe the secretory epithelium

make and release a product

describe the transporting epithelium

selectively move substances between a lumen and the ECF

describe the chemical gradients

non-charged permeable solutes diffuse down own chemical gradients

describe the electrochemical gradients

diffusion of charged solutes is affected by own chemical gradient AND overall electrical gradients

look at this diagram (membrane transport)

describe facilitated diffusion

passive movement of non-permeable solutes down their own electrochemical gradient using a transport protein imbedded in the cell membrane

describe channel proteins

• used only for facilitated diffusion

• allows non-permeable molecules (e.g. ions or glucose) to passively cross the membranes

• allows permeable molecules (like water) to diffuse across the membrane more quickly (e.g. aquaporins)

describe carrier proteins

• used for facilitated diffusion and active transport

• change conformation to allow non-permeable molecules through membrane in a single direction (only open to one side of the membrane at a time)

• classified as one of three types (uniport, symport, antiport)

describe carrier saturation

• the transport can reach a maximum rate when all the carrier binding sites are filled with substrate

• extracellular substrate concentration→transport rate is proportional to substrate concentration until the carriers are saturated

what are the three ways to control channel and carrier proteins

• chemically-gated

• voltage-gated

• mechanically-gated

describe chemically-gated

a ligand binds to a receptor on the protein to change its confirmation

describe voltage-gated

a change in the electrical charge across the surrounding membrane changes the protein’s confirmation

describe mechanically-gated

a physical force changes the protein’s conformation

describe active transport

• solutes are moved against their electrochemical gradient using energy either stored in the bonds of molecules (e.g. ATP) or released from stored concentration gradients of other molecules across the same membrane

• primary = ATP

• secondary = concentration gradient of a second substance that is maintained using ATP

look at the primary active transport of Na+/K+ ATPase pumps

look at the diagram for the secondary active transport of sodium-glucose transporters (SGLT)

describe the steps in the directional movement of glucose across intestinal epithelium

1. Na+ glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ concentration gradient

2. GLUT transporter transfers glucose to ECF by facilitated diffusion

3. Na+ K+ ATPase pumps Na+ out of the cell, keeping ICF Na+ concentration low

describe transepithelial transport

• polarized epithelia have different transport proteins on apical and basolateral membranes

• allows selective directional transport across the epithelium

what is absorption with regard to transepithelial transport

transport from lumen to ECF

what is secretion with regard to transepithelial transport

transport from ECF to lumen

describe the negative feedback loop

• homeostatic (i.e. keep regulated variable with a desired optimal range)

• a negative feedback response is in the opposite direction of the stimulus

• examples: thermoregulation of core body temp and Ca2+ levels in the blood

what examples of internal and external sensors/receptors

what is the regulated variable in a feedback loop

variable being monitored and maintained

what is the stimulus in a feedback loop

an increase or decrease in regulated variable

what is the sensor/receptor in a feedback loop

cells measuring the levels of regulated variable (pick up the changes)

what is the setpoint in the feedback loop

desired value (usually a range) of the regulated variable

what is the afferent pathway in the feedback loop

nerves that carry signal from sensor to IC (input)

what is the integrating center (IC) in the feedback loop

the tissues, gland, or organ maintaining variable that compares “value” of the regulated variable to the setpoint and determines if any action needs to be taken

what is the efferent pathway in the feedback loop

hormones or nerves that carry signal from IC to effector tissues (the output)

what is the effector in the feedback loop

tissue that carries out response and brings regulated variable back within desired range

what is the response in the feedback loop

physiological or behavioral change that affects the level of the regulated variable

when do negative feedbacks turn response loops on/off

when the behavior (eg temperature) gets to the edge of the normal range of function

how does the body maximize heat loss with thermoregulation

• vasodilation of cutaneous blood vessels

• increased sweating

• behavioral responses

  • use of fans to increase convective heat loss

  • immersion in water to increase conductive heat loss

  • staying out of the sun to prevent radiant heat gain

  • removing clothes

how does the body minimize heat production with thermoregulation

• diminished food intake to lessen obligatory heat production

• shivering and constricting vessels in response to a fever

• behavioral responses

  • decreased physical activity

what is the regulated variable for thermoregulation for increasing Tb

core body temperature

what is the stimulus for thermoregulation for increasing Tb

increase in Tb outside of range

what is the sensor/receptor for thermoregulation for increasing Tb

thermoreceptor cells in the hypothalamus of the brain

what is the setpoint for thermoregulation for increasing Tb

37 degrees celsius

what is the afferent pathway for thermoregulation for increasing Tb

NONE

what is the integrating center for thermoregulation for increasing Tb

same as sensor cells

what is the efferent pathway for thermoregulation for increasing Tb

• sympathetic cholinergic neurons regulate fast physiological and behavioral responses

• thyroid hormones regulate metabolic pathways

what is the effector for thermoregulation for increasing Tb

arterioles, sweat glands, base of hair follicles

what is the response for thermoregulation for increasing Tb

• physiological: increased vasodilation, sweating, pilorelaxation

• behavioral: stretch out, decrease activity, decrease food intake, remove clothes, avoid warm environments

• metabolic: decrease obligatory heat production

what is the feedback for thermoregulation for increasing Tb

decrease Tb

what is an antagonist control

when an increase or decrease in a regulated variable uses different efferent pathways to intiate different responses

what does it mean that acceptable ranges differ

• regulated variables can be kept within a very narrow range or a much wider range depending on their importance of constancy

• narrow range example:

  • the set point for blood pH is 7.4 and the acceptable range for pH is only 7.35-7.45

  • the set point for core temp is 98.8 and the acceptable range for core body temperature is 97-99 degrees F

• wide range example

  • the set point for blood oxygen saturation is about 99nm Hg, and the acceptable range is 60-100 mm Hg

what does it mean that feedback sensitivities differ

• variables that drastically impact the functioning of important processes must be maintained within a narrow range and are sensitive to even smaller changes

• sensitive feedback example: blood osmolarity feedback loops activates with a 3% change in concentration

• robust feedback example: blood O2 saturation feedback loops don’t activate until there is a 40% drop

what does it mean that setpoints are not fixed

• set points for different individuals can vary

• setpoints for an individual can change

  • increased Tb setpoint during exercise, fever, ovulation

  • decreased Tb setpoint during sleep and hibernation

  • circadian rhythms are due to changing setpoints

what does it mean that not everything is regulated

• physiological regulation is used to regulate only the most important variables needed to sustain life

• the vital list

  • ions: Na+, K+, Ca2+

  • gases: O2 and CO2

  • physical properties: osmolarity, blood pressure, temperature

  • nutrients: glucose levels (brain fuel)

what are the benefits to regulation

• regulation of the internal environment means cells don’t have to withstand changes in their immediate environment

• enzymes and other biochemical systems can evolve to work optimally under a specific set of conditions

what are the costs to regulation

• it’s EXPENSIVE

• it takes a lot of energy to generate and dissipate heat, or maintain ion balance within the body

what is meant by feedback loops are not all the same

• they may have more than one integrating center

• they may have more than one efferent pathway controlled by nerves and/or hormones

• they often have multiple response to regulate the variables

describe positive feedback loops

• non-regulatory (i.e. increases the difference between the level of the regulated variable and the setpoint until an external change occurs that restores homeostasis)

• response is in the SAME direction as the stimulus

• examples

  • labor and delivery

  • erections

  • nerve action potentials

  • blood clotting

what is the stimulus in labor

cervical stretch

what is the sensor/receptor in labor

stretch receptors in cervix

what is the setpoint in labor

no stretch