BIO310

What is physiology?

The study of how cells, tissues, organs, and organ systems function in living organisms

What are organs?

Composed of 2 or more of the four tissue types

What are the 4 major tissue components?

Epithelial, connective tissue, neurons, muscle

What is an organ system?

Collection of organs that together perform an overall function

What are connective-tissue cells?

Connect, anchor, and support the structures of the body

What are the types of connective tissue?

Loose connective, dense connective, blood, bone, cartilage, adipose

What are muscle cells?

Specialized to generate mechanical force; the 3 types are:

• cardiac (involuntary)

• skeletal (involuntary)

• smooth (voluntary)

What is a neuron?

Cell of the nervous system that is specialized to initiate, integrate, and conduct electrical signals to other cells, sometimes over long distances

What is a nerve?

Cellular extensions from many neurons, packaged together along with connective tissue

What are the levels of cellular organization?

1. Cells

2. Tissue

3. Organ

4. System

5. Body

What are epithelial cells?

Specialized for the selective secretion and absorption of ions and organic molecules, and for protection

• must be in contact with the external environment (ex. skin, respiratory cells in contact with outside air)

• Characterized and named according to their unique shapes

What is meant by the basolateral side?

Facing the body

What are the different shapes of epithelial cells?

1. Cuboidal - cube

2. Columnar - elongated

3. Squamous - flattened

4. Ciliated

What are endothelial cells?

Not in contact with external environment, line closed tubes such as blood vessels and heart

What are the extracellular fluid and matrix?

The immediate environment that surrounds each individual cell in the body

What does the ECM consist of?

Mixture of proteins, polysaccharides, and minerals

What are the general functions of the ECM?

1. Provides a scaffold for cellular attachments - allows for shape of tissue

2. Transmits information in the form of chemical messengers to the cells to help regulate their activity, migration, growth, and differentiation

What are the types of proteins in the ECM?

1. Rope-like collagen fibers

2. Rubber band-like elastin fibers

3. Nonfibrous proteins that contain carbohydrate

What is body fluid?

Watery solution of dissolved substances (oxygen, nutrients, and wastes) present in the body

What is extracellular fluid?

Fluid in the blood and in spaces surrounding the cells

What is interstitial fluid?

75-80% of extracellular fluid that lies around and between cells

• Ex. surfactant, saliva, CSF< synovial fluid, peritoneal fluid

What is plasma?

20-25% of extracellular fluid which is in the fluid portion of the blood

What is the interstitium?

The space containing the interstitial fluid

What is the total volume of extracellular fluid?

Sum of plasma and interstitial fluid

What is homeostasis?

Refers to physiological variables in a state of dynamic constancy; it is not a static process (static = dead, biology is always within a predictable physiological range)

• Body temperature, partial pressure of oxygen, electrolyte concentration

• Physiological variables can change dramatically over a 24-hour period, but the body is still in overall balance

What are the states of homeostasis?

1. Physiology - homeostasis is maintained

2. Pathophysiology - homeostasis is not maintained

How does blood glucose concentration change during a typical 24-hour period?

Most variable thing in our body, increase after eating, then return to set point via homeostasis

• insulin facilitates sugar entry into cells for use

What is dynamic constancy?

Levels change over short period of time but remain relatively constant over long period of time

What are feedback loops/systems?

Common mechanisms to control physiological processes

What is a negative feedback system?

Brings about responses that move a variable opposite to the direction of its original change

What is a positive feedback system?

Enhances the production of the product or accelerates a process

What are the ways the body controls for body temperature?

1. Constriction of skin blood vessels - meant to reduce heat loss

2. Curling - contraction of muscle to reduce heat loss, change of posture as well

3. Shivering - increases heat production (muscles are contracting - this burns energy producing heat)

What is a regulator?

Has the ability to keep the body temperature within a physiological range (zone of stability)

Describe the process of childbirth?

More contractions = more pushing = more oxytocin = stronger contractions

Describe the process of blood clotting?

Clotting factors activate so one factor activates another until the clot is formed

What is a reflex?

Specific, involuntary, unpremeditated, “built-in“ response to a particular stimulus

What are the components of a reflex arc?

1. stimulus

2. receptor

3. afferent (incoming) pathway

4. integrating center

5. efferent (outgoing) pathway

6. effector

What is a stimulus?

Detectable change in the internal or external environment

What is a receptor?

Detects the environmental change

What is the afferent pathway?

Signal travels between the receptor to the integrating center

What is the efferent pathway?

Signal travels from the integrating center to the effector

What is an integrating center?

Receives signals from many receptors, some of which may respond to quite different types of stimuli

• output reflects the net effect of the total afferent input (integration of numerous bits of information)

What is feedforward regulation?

Physiological changes that occur in anticipation of a future change to a variable

What body cells can act as effectors in homeostatic reflexes?

Almost all body cells

• muscles and glands are the major effectors of biological control systems

What are glands?

May be both a receptor and an integrating center, and they secrete hormones into the blood that act as effectors

What is a hormone?

Type of chemical messenger secreted into the blood by cells of the endocrine system, may act on many different cells simultaneously because they circulate throughout the body

• produced and secreted from endocrine glands or in scattered cells that are distributed throughout another organ

What are neurotransmitters?

Chemical messengers that are released from the endings of neurons onto other neurons, muscle cells, or gland cells

What is an autocrine substance?

Acts on the same cell that secreted the substance

What is a paracrine substance?

Target cells in close proximity to site of release of paracrine substance

What is a neurotransmitter?

Targets a neuron or effector cell in close proximity to site of neuro-transmitter release

What is a hormone?

Target cells in one or more distant places in the body

What are gap junctions?

Physical linkages connecting the cytosol between two cells, which allow molecules to move from one cell to an adjacent cell without entering the extracellular fluid

What is juxtracrine signaling?

Chemical messenger not actually being released from the cell producing it but rather is in the plasma membrane of that cell; when the cell encounters another cell type capable of responding to the message, the two cells link up via the membrane-bound messenger

What is adaptation?

A physiological process that the body uses to cope with changes in external environment, over generations due to changes in gene expression frequency

• Not reversible

• Denotes a characteristic that favors survival in specific environments

Acclimatization

Reversable physiological process body uses to cope with changes in the external environment

• improved functioning of an already existing homeostatic system due to prolonged exposure to an environmental change

Acclimation

Experimental term, cousin to acclimatization ?

What are the changes in physiology that are responses to changes in the external environment?

1. Acute change

2. Chronic changes (termed acclimation and acclimatization; also termed phenotypic plasticity or phenotypic flexibility)

3. Evolutionary changes

What are the changes in physiology that are internally programmed to occur whether or not the external environment changes?

1. Developmental changes

2. Changes controlled by periodic biological clocks

What are acute changes?

Short-term changes in an individual’s physiology that occur immediately after an environmental change. These changes are reversible.

What are chronic changes?

Long-term changes in physiology that develop after prolonged exposure to new environmental conditions. These are reversible and involve acclimation or phenotypic plasticity.

What are evolutionary changes?

Changes in gene frequencies across generations in a population due to environmental changes. These are not reversible in individuals.

What are developmental changes?

Changes in the physiology of individual animals that occur in a programmed way as the animals mature from conception to adulthood and then to senescence.

What are changes controlled by periodic biological clocks

Physiological changes that occur in a cyclic manner (e.g., daily) due to internal biological clocks.

What is the circadian rhythm?

Rhythmical changes which cycles approximately once every 24 hours.

• waking and sleeping

• body temperature

• hormone concentrations in the blood

• excretion of ions into the urine

How do steroid hormones fluctuate throughout the day?

Stress hormone like cortisol drops while sleeping and increases before waking (example of feedforward regulation)

What are corrective responses?

Negative feedback homeostatic responses, initiated after the steady state of the individual has been perturbed

What happens to body temperature during sleep and wake?

In sleep, drops because body is not very active and elevates 1hr before we wake

What is the purpose of the cell membrane?

1. Separates the cell from extracellular environment

2. Detects chemical messengers arriving at the cell surface and affects the way cells communicate

3. Regulates the passage of substances into and out of cells and between cell organelles and cytosol

4. Links adjacent cells together by membrane junctions

5. Anchors cells to the extracellular matrix

What is the purpose of the extracellular matrix?

Helps maintain the shape of the tissue

What is the difference between the cytoplasm and cytosol?

Cytoplasm - refers to all fluid in a cell except that in the nucleus

Cytosol - all fluid in a cell, except nuclear fluid and fluid in organelles

What is the structure of membrane phospholipid molecules

Made of many forms of amphipathic molecules

• Lipophilic and hydrophilic parts

• Choline or other charged group is positive (+)

• Phosphate is negative (-)

• 2 chains of hydrocarbon derived from fatty acids

• Glycerol residue joins the hydrocarbon and head

Head is soluble due to charges (polar)

What is a saturated fatty acid?

Straight, this leads to a rigid structure, maximum number of single bonds

What is an unsaturated fatty acid?

Bent due to double bond, this 30 degree angle allows for more space between molecules, allowing them to move around

• Do not want rigid cell membrane, want it to be fluid to allow for mobility (this means molecules can move around)

• Bilayer molecules are not attached by bonds allowing them to move around in the membrane

• Cells can expand to a limit, the more fluid the membrane, the more expandability of the cell

What is the structure of the cell membrane?

Major membrane lipids are phospholipids = amphipathic and organized into a bilayer with the nonpolar fatty acid chains in the middle

• The polar regions of the phospholipids are oriented toward the surfaces of the membrane as a result of their attraction to the polar water molecules in the extracellular fluid and cytosol

How is cholesterol present in the plasma membrane and intracellular membranes?

• The plasma membrane contains cholesterol at the tails since it is lipid soluble

• Intracellular membranes contain very little cholesterol

• The close association of the nonpolar rings of cholesterol with the fatty acid tails of phospholipids tens to limit the ordered packing of fatty acids in the membrane

  • Make spaces between tails, adding to membrane fluidity

• A more highly ordered, tightly packed arrangement of fatty acids tends to reduce membrane fluidity

• Cholesterol and phospholipids have a coordinated function in maintaining an intermediate membrane fluidity

How does cholesterol affect membrane temperature?

Act as buffers to temperature effects on the membrane

• High temps = more movement, the cholesterol placing space between the tails prevents extreme fluidity

• Low temps = less movement, cholesterol prevents super rigidity because it creates space between the tails

What are integral membrane proteins?

Protein embedded within the cell membrane

• Has 3 domains: intracellular, extracellular, transmembrane

• Cannot be extracted from the membrane without disrupting the lipid bilayer

• Amphipathic

• Can be transmembrane or just integral

What is a peripheral membrane proteins?

Not amphipathic and do not associate with the nonpolar regions of the lipids in the interior of the membrane

• located at the membrane surface where they are bound to the polar regions of the integral membrane proteins

• Easy to detach because they are bound to one side of the membrane and don’t have a part within the membrane

What is a transmembrane protein?

Form channels through which ions or water can cross the membrane, others are associated with the transmission of chemical signals across the membrane or the anchoring of extracellular and intracellular protein filaments to the plasma membrane

What are integrins?

Integrins are transmembrane proteins that bind to specific proteins in the extracellular matrix and link them to membrane proteins on adjacent cells

• Extracellular domain allows for protein-protein interactions with ECM

• Intracellular domain can bind to proteins within cells

What are desmosomes?

Desmosomes hold adjacent cells firmly together in areas that are subject to considerable stretching, such as the skin

• difficult to take apart

• Consist of a region between two adjacent cells where the apposed plasma membranes are separated by about 20 nanometer

• Can join cells anywhere

What are dense plaques?

Characterize desmosomes, accumulations of proteins along the cytoplasmic surface of the plasma membrane

• serve as anchoring points for cadherins

• peripheral proteins

What are cadherins?

Proteins that extend from the cell into the extracellular space, where they link up and bind with cadherins from an adjacent cell

What are keratin proteins?

Cellular proteins inside the cytoplasm

What are tight junctions?

Form when the extracellular surfaces of two adjacent plasma membranes join together so that no extracellular space remains between them

• occurs in a band around the entire circumference of the cell

• form barriers that limit the movement of material between cells

• Separates apical and basolateral portions of the cell

What are the 3 functions of tight junctions?

1. limit the passage of molecules and ions through the space between cells. So most materials must enter the cells by diffusion or active transport) to pass through the tissue. This pathway provides tighter control over what substances are allowed through. This will lead to Trans-epithelial transport.

2. They block the movement of integral membrane proteins between the apical and basolateral surfaces of the cell to maintain the special functions of each surface

3. what is the third one ???

What are gap junctions

Each cell has a ring of 6 connexin proteins that together form the pore, and the rings of the 2 cells line up to create continuity between cells

• Each ring of connexin proteins is called a connexon

• Direct passage of molecules between neighboring

• Adjoining cells have an array of connected hexagonal channels

• Central channel allows passage of molecules smaller than 1.5 nm (DNA and RNA cannot pass)

What are mucin secreting cells?

At least 10 types of endocrine cells that release their secretions into the spaces outside the cell, after which the secretions enter the blood for transport elsewhere

• endocrine-like cells termed paracrine cells produce secretions that affect nearby cells

What is simple diffusion?

one area has high concentration, other has low

• Molecules will pass from high to low concentration

• As temp increases, more diffusion occurs - more movement of molecules due to higher KE

• Some molecules will pass from low to high but this is at a lower rate so net flux is from high to low

How does diffusion time vary?

Increases in proportion to the square of the distance over which the molecules diffuse

• limited by distance

Rate is measured by their permeability coefficients

• Membranes act as barriers that slow diffusion

• Major limiting factor = hydrophobic interior of lipid bilayer

What is a permeable membrane?

Substances can move across the cell membrane

What is an impermeable membrane?

Substances cannot move across the membrane

What is passive vs. active movement?

Passive: areas of high to low concentration

Active: move against concentration gradient, fueled by energy from the hydrolysis of ATP

What is simple diffusion?

Movement of molecules from one location to another solely as a result of their random thermal motion

• No energy required

• Higher concentration to lower concentration

What are some factors net flux depends on in passive diffusion?

1. Temperature

2. Mass of the molecules

3. Surface area

4. Medium through which the molecules move

What is the phospholipid bilayer permeable to?

• Lipid soluble molecules (steroids)

• Gases (CO2, O2, NO, CO)

• Uncharged polar molecules (urea, ethanol)

• Water (but very slowly)

For permeability, moleceule should break all its hydrogen bonds with water

What is mediated transport?

Many molecules (ex. AA and glucose) are able to cross membranes but are too polar to diffuse through lipid bilayers and too large to diffuse through channels; conformational changes of integral membrane proteins known as transporters bring these solutes into and out of cells

How is the specificity of an ion channel determined?

1. Channel diameter

2. Charged and polar surfaces of polypeptide subunits that form the channel walls

3. Number of water molecules associated with the ion

What is facilitated diffusion?

Requires protein molecules that assist in the transmembrane movement of solutes

• Movement along a concentration gradient (higher to lower)

What are pathways of passive transport?

Channels - voltage gated, ligand gated, water aquaporins

Carriers/transporters - uniport, co-transport (symport), counter-transport (antiport)