Practical Human Physiology

Basically an extension of anatomy

What is the plasma membrane’s structure?

• fluid lipid bilayer embedded with proteins

  • most abundant lipids = phospholipids

• small amount of carbohydrates → on surface only

  • role of selfness = blood

    • negative → doesn’t have carbs

    • positive → has carbs

• cholesterol → tucked btw phospholipid molecules

  • contributes to fluidity and stability of cell membrane = breaks rigidness of membrane

  • precursor for hormones → testosterone, estrogen

Function of plasma membrane proteins:

• span membrane to form water-filled pathways, or channels across lipid bilayer

• serves as carrier molecules and docking-marker acceptors

• membrane-bound enzymes

• receptor sites

• cell adhesion molecules (CAMs)

• proteins on surface are important in cells’ ability to recognize “self” and in cell-to-cell

Functions of the lipid bilayer of the plasma membrane:

• forms basic structure of the membrane

• hydrophilic interior serves as barrier to passage of water soluble substances between ICF and ECF

• responsible for fluidity of the membrane

Function of membrane carbohydrates:

• serve as self-identity markers which enable cells to identify and interact with one another

• different cell types have different markers

• carbohydrate-containing surface markers are also involved in tissue growth

What are the levels of organization?

1. Chemical

2. Cellular

3. Tissue

4. Organ

5. Body System

6. Organism

The “chemical” level of organization is…

molecules composed of atoms

The “cellular” level of organization is…

• cells are basic unit of life

• Senses and responds to changes in its environment

The “tissue” level of organization is…

four primary types of tissues

What are the four primary types of tissues?

1. Muscle

2. Epithelial

3. Nervous

4. Connective

What is muscle tissue?

Produces protection and movement through contraction of muscle fibers

Give three examples of muscle tissue..

• Skeletal: attaches to the bone & provides movement of the body

• Cardiac: only in heart & causes it to beat

• Visceral/Smooth: in the walls of the internal organs

What is epithelial tissue?

Covers the surface of the bod and is the main tissue of the skin —> secrete and protection

Give examples of epithelial tissues..

• skin

• intestinal, respiratory, urinary, and circulatory tract

• In the lining of blood vessels and body cavities

• Forms the glands of the Exo/Endocrine system

What is nervous tissue?

Coordinates and controls all bodily activities by transmitting messages throughout the body

Give examples of nervous tissue…

• brain

• nerves

• spinal cord

What is connective tissue?

Supports and connects organs and body tissues

Give examples of connective tissue…

• adipose —> fat

• fibrous —> tendons, ligaments

• cartilage —> smooth, elastic

• bone —> hard, unbendable

• blood —> liquid/vascular

The “organ” level of organization is…

consists of two or more types of tissues

The “body system” level of organization is…

groups of organs that perform related functions

How many body systems are there and what are they?

1. circulatory system

2. digestive system

3. respiratory system

4. urinary system

5. skeletal system

6. muscular system

7. integumentary system

8. immune system

9. nervous system

10. endocrine system

11. reproductive system

12. lymphatic system

When you think about these 11-12 physiological systems, what is the common “denominator” that ties them together, so they are in various ways dependent on each other?

Homeostasis

What is homeostasis?

A maintenance of a relatively stable internal environment

• each cell contributes

• essential for survival and function of all cells

What is extracellular fluid (ECF)?

It is a fluid environment in which the cells live

• outside of the cells

What are the two components of extracellular fluid?

1. plasma/blood

2. interstitial fluid

What is intracellular fluid (ICF)?

Fluid contained within all body cells

What factors are homeostatically regulated?

1. concentration of nutrient molecules

2. concentration of O2 and CO2

3. concentration of waste products

4. pH

5. concentration of water, salt, and other electrolytes

6. volume and pressure

7. temperature

What is the role of the circulatory system?

It carries materials from one part of the body to another

What is the role of the digestive system?

• breaks down dietary food into smaller molecules that can be distributed to body cells

• transfers water and electrolytes from external environment to internal environment

• eliminates undigested food residues to external environment in the feces

What is the role of the respiratory system?

• gets O2 from and eliminates CO2 to the external environment

• important in maintenance of proper pH of internal environment

What is the role of the urinary system?

• removes excess water, salt, acid, and other electrolytes from plasma and eliminates them in urine

• Thanksgiving —> have to pee a lot

What is the role of the skeletal system?

• provides support and protection for soft tissues and organs

• serves as storage reservoir for calcium

• along with muscular system enables movement of body and its parts

• bone marrow is ultimate source of all blood cells

What is the role of the muscular system?

• moves the bones

What is the role of the integumentary system?

• serves as our protective barrier

• important in regulating body temperature

What is the role of the immune system?

• defends against foreign invaders and against body cells that have become cancerous

• paves way for repairing or replacing injured or worn-out cells

What is the role of the nervous system?

• controls and coordinates bodily activities that require rapid responses

• detects and initiates reactions to changes in external environment

What is the role of the endocrine system?

• secreting glands of endocrine regulate activities that require duration rather than speed

• controls concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume and electrolyte composition

What is the role of the reproductive system?

• not essential for homeostasis (not essential for survival of individual)

• is essential for perpetuating the species

In order to maintain homeostasis, we need to be able to…

• detect deviations from normal in the internal environment that need to be held within narrow limits

• integrate this information with other relevant information

• make appropriate adjustments in order to restore factor to its desired value

What are the two classes of control systems?

1. Intrinsic controls

2. Extrinsic controls

What are intrinsic controls?

local controls that are inherent in an organ

What are extrinsic controls?

• regulatory mechanisms initiated outside an organ

• accomplished by nervous and endocrine systems

What is a feedforward system?

• term used for responses made in anticipation of a change

• hormonal influences to generate a response

Example of feedforward systems?

1. hunger pains (ghrenlin) —> start looking for food

What is a feedback system?

refers to responses made after change has been detected

What are the types of feedback systems?

1. negative - exerts a response to oppose/decrease

2. positive - exerts a response to amplify

What is a negative feedback system?

• primary type of homeostatic control

• opposes initial change

• components:

  • sensor: monitors magnitude of a controlled variable

  • control center: compares sensor’s input with a set point

  • effector: makes a response to produce a desired effect

What is a positive feedback system?

• amplifies an initial change

• does not occur as often as a negative feedback system

• Example:

  • uterine contractions become increasingly stronger until the birth of the baby

Disruptions in homeostasis can lead to…

• illness

• death

• pathophysiology: abnormal functioning of the body associated with disease

What is the plasma membrane?

• AKA cell membrane

• surrounds every cell → thin layer of lipids and protein that forms outer boundary

• separates cell contents from its surroundings

  • separates ICF and ECF

• controls movement of molecules between the cell and the environment

• participates in joining cells to form tissues and organs

• important role in the ability of a cell to respond to changes in the cell’s environment

What is the nucleus?

• typically the largest single organized cell component

• enclosed by a double-layered nuclear envelope

• contains cell’s genetic material, DNA

What are the DNA functions?

• directs protein synthesis

• serves as genetic blueprint during cell replication

What is the cytoplasm?

• portion of cell interior not occupied by the nucleus

• consists of

  • organelles

  • cytoskeleton

What are organelles?

• “little organs”

• distinct, highly organized, membrane-enclosed structures

What is the cytoskeleton?

• complex protein network protein of cytosol

  • found in a complex, gel-like liquid called the cytosol

• “bone and muscle” of the cell

• Has three distinct elements:

  • microtubules

  • microfilaments

  • intermediate filaments

What is the cytosol?

• occupies about 55% of total cell volume

• semi-liquid portion of cytoplasm that surrounds the organelles

• contains cytoskeleton

What activities do the cytosol participate in associated with gelatinous portion of cytoplasm?

• enzymatic regulation of intermediary metabolism

• ribosomal protein synthesis

  • perform what is necessary within the cell —> free ribosome

• storage of fat, carbohydrate, and secretory vesicles

What is the endoplasmic reticulum (ER)?

• elaborate fluid-filled membranous system distributed throughout the cytosol

• Primary function -> protein and lipid manufacture

• Two types:

  • smooth ER

  • rough ER

What is the smooth ER?

• lipid synthesis

• mesh of tiny interconnected tubules

What is the rough ER?

• protein synthesis

• projects outward from smooth ER as stacks of relatively flattened sacs

• surface has attached ribosomes, but free ribosomes can sometimes go through rough ER depending on signaling

What is the golgi complex?

• closely associated with the ER

• consists of cisternae

• number of golgi complexes per cell varies with the cell type

• AKA the post office

What are the functions of the golgi complex?

• processes raw materials into finished products

• sorts and directs finished products to their final destinations

• packages secretory vesicles to release by exocytosis

What are cisternae?

It is a stack of flattened, slightly curved, membrane-enclosed sacs

• like pancake stack

What is a lysosome?

• membranous sacs containing hydrolytic enzymes

• serve as intracellular digestive system

• Extracellular material attacked by lysosomes enters cell by endocytosis

What is endocytosis?

the process of actively transporting molecules into the cell by engulfing it with its membrane

What are they kinds of endocytosis?

• pinocytosis

• receptor-mediated endocytosis

• phagocytosis

What is pinocytosis?

A kind of endocytosis where you are taking in fluid; very small

What is receptor-mediated endocytosis?

receptor based endocytosis, which means it is more specific

What is phagocytosis?

type of endocytosis where you are engulfing something large

What are peroxisomes?

membranous sacs that house oxidative enzymes that detoxify various waste products

• waste products = alcohol

Examples of things with a lot of peroxisomes?

1. Liver: fibrous tissue does not equal a lot of peroxisomes

2. Potatoes: lots of peroxisomes

   1. potatoes stay good because of a lot of starch

What is the mitochondria?

• energy organelle

  • major site of ATP production

  • contains enzymes for citric acid cycle and electron transport chain

• enclosed by a double membrane

  • cristae

What is the cristae?

It is the inner infolded membrane of the mitochondria

Would the mitochondria be different in a superhero?

there would be an increased number of mitochondria

What are the steps involved in generation of ATP within the cell?

1. Glycolysis

2. Citric Acid Cycle (Kreb Cycle)

3. Electron Transport Chain

What is glycolysis?

• chemical process involving 10 separate sequential reactions that break down glucose into two pyruvic acid molecules

• anaerobic process

What is the citric acid cycle?

• requires oxygen

• pyruvic acid from glycolysis is converted to acetyl CoA which enters citric acid cycle

• citric acid cycle consists of eight separate biochemical reactions that are directed by enzymes of mitochondrial matrix

• important in preparing hydrogen carrier molecules for entry into electron transport system

What is the electron transport chain?

• requires oxygen

• series of reactions that occur on the inner mitochondrial membrane

• major source of ATP needed for cellular activities

What cellular activities that require ATP?

• synthesis of new chemical compounds

• membrane transport

• mechanical work

• repair of cells/tissues in a superhero

Breaking a chemical bond is…

an energy source in proteins

Athletes can remove lactatic acid, more or less efficiently?

More efficiently because of their training

What differences does a superhero have?

1. stress → stress on cells and stress response

2. speed of cellular response

3. fitness training

What are microtubules?

• AKA freeway

• transport secretory vesicles

• movement of specialized cell projections

• form mitotic spindle during cell division

• contain tubulin protein

What are microfilaments?

• contractile systems

• mechanical stiffeners

• gives strength

• contain 2 chains of actin protein

What are intermediate filaments?

• help resist mechanical stress → cannot pull off our skin

• gives strength

• contains keratin

What are cell-to-cell adhesions?

• Adhesions bind groups of cells into tissues and package them into organs

• Once arranged, cells are held together by three different means

  • Extracellular matrix

  • Cell adhesion molecules in cells’ plasma membranes

  • specialized cell junctions

What is the extracellular matrix?

• AKA biological glue

• major types of protein fibers interwoven in matrix

  • collagen, elastin, & fibronectin

What are the three types of specialized cell junctions?

1. Desmosomes

2. Tight junctions → impermeable junctions

3. Gap junctions → communicating junctions

What are desmosomes?

• A kind of specialized cell junction that doesn’t come apart easily

• act like “spot rivets” that anchor two closely adjacent non-touching cells

• most abundant in tissues that are subject to considerable stretching

What are tight junctions?

• Firmly bond adjacent cells together → like sewing

• seal off the passageway between the two cells

• found primarily in sheets of epithelial tissue

• prevent undesirable leaks within epithelial sheets

Example(s) of tight junctions:

• Bladder → urine doesn’t leak

• Digestive system → acid doesn’t spill

What are gap junctions?

• small connecting tunnels formed by connexons

• especially abundant in cardiac and smooth muscle

• in non-muscle tissues permit unrestricted passage of small nutrient molecules between cells

• serve as method for direct transfer of small signaling molecules from one cell to the next

Example(s) of gap junction:

Uterine contactions

What is membrane transport?

• cell membrane is selectively permeable

• two properties of particles influence whether they can permeate cell membrane without assistance

  • relative solubility of particle in liquid

  • size of particle

What are the kinds of membrane transport?

1. Unassisted membrane transport

   1. diffusion

   2. osmosis

2. Assisted membrane transport

   1. carrier-mediated transport

   2. facilitated transport

   3. active transport

   4. vesicular transport

What is diffusion (simple passive diffusion)?

• uniform spreading out of molecules due to their random intermingling

• molecules move from area of high concentration to area of low transport

• process is crucial to survival of every cell

• simple passive diffusion → no energy required

• doesn’t require membrane

Diffusion plays an important role in what processes?

• exchange of oxygen and carbon dioxide between blood and air in lungs

• movement of substances across kidney tubules

Diffusion example outside of body system:

Sugar in coffee

Simple diffusion is

movement of ions from hyper to hypo

What are the factors affecting rate of diffusion in Fick’s law of diffusion?

• Magnitude/steepness of the concentration gradient

• Permeability of the membrane to the substance

• Surface area of the membrane across which diffusion is taking place → more surface area doesn’t = increased efficiency

• Molecular weight of the substance → high weight = more energy required

• Distance through which diffusion takes place

What is osmosis?

• net diffusion of water down its own concentration gradient

• requires membrane

• energy independent → passive process

• Tonicity of solution