Exam 1: Lecture I Flashcards
Physiology
study of the biological function of an
organism/tissue/cell
Pathophysiology
study of an organism/tissue/cell in a state of disease or injury
Comparative patho/physiology
differences between species
Order of system of cells
Cells > Tissues > Organ system > Organism
The “Cell Theory”
Each cell has a unique pattern of gene expression. The
selective combination of expressed genes and their
expression levels determines a cell’s properties
Is it possible to have identical DNA but different properties
Yes, people have the same genes
What causes cells in the body to have different tasks from each other, yet still have the same DNA?
Gene expression
Extracellular environment is composed of
extracellular matrix + interstitial fluid
What is ECM?
ECM are protein fibers (collagen, elastin) & ground substance (amorphous gel)
Interstitial fluid
- traffics O2, nutrients, hormones to cells
- removes CO2,
wastes - continuously formed from blood plasma
- continuously returned to
plasma
Cells are embedded
in the ECM
Cell –
ECM interactions through integrins and dystroglycan important for structure
and signaling
Muscle Tissue
skeletal, cardiac, smooth
Epithelial Tissues
many kinds, simple (one layer) & multilayer.
Endothelium vs epithelium
- Helps to protect body
- Lines many passages inside the body
Nervous Tissue
Composed of dendrites, an axon, a cell body and supporting cells
-Important for the CNS
Connective Tissues
- large amounts of extracellular
material (proteins or fluid). - Includes extracellular matrix, adipose (fat) tissue, cartilage, bone, teeth, tendon
Why do we need so many systems and
tissue types??
To be able to respond to external and internal
perturbations to maintain a “normal” state
Homeostasis
“maintaining constancy of the internal environment”
3 parts of Homeostasis
- Sensors
- Integrating center
- Effector systems
Sensors
monitor important parameters
Integrating center
receive input from sensors,
recognize changes from set point, control effectors
Effector systems
implement actions to restore set
point
Example of “regulated” parameters
respiration and heart rate (pCO2, pH)
- blood flow
- temperature
- blood glucose
Negative feedback
Brings response back to original set point
“a state of dynamic constancy”
Examples of Negative feedback
- Body temperature ( shivering/sweating)
- Blood glucose
- Blood pressure
In depth Blood Glucose:
After eating
- Blood glucose rises
- Activation of Pancreatic islets (of langerhans)
- Insulin increases
- Cellular uptake of glucose increases
- Blood glucose decreases
Insulin is effecter
In depth Blood Glucose:
Fasting
- Blood glucose lowers
- Activation of pancreatic islets
- Insulin decreases
- Glucagon increases
- Cellular uptake of glucose
- Glucose secretion into blood by liver
- Blood glucose increases
In depth blood pressure
Lying down
- Blood pressure falls when you stand up (stimulus)
- Blood pressure receptors respond ( sensor)
Medulla oblongata of brain is the integrating center
- Heart rate increases ( effector)
- Rise in blood pressure ( negative feedback response)
Positive Feedback
In rare cases: a positive feedback cascade may restore homeostasis.
- Pushes farther away from set point
Example of positive feedback
Perturbation = bleeding injury: Blood clotting
-Childbirth
Blood clotting in depth
- injury attracts a few
platelets (blood cells for clotting).
• these platelets release factors that attract many MORE platelets (positive
feedback) and other proteins to form clot.
• net result: injury is blocked by platelet clot, prevents further loss of blood
to restore homeostasis
Gap junctions
Points that provide cytoplasmic channels from one cell to another with special membrane proteins. Also called communicating junctions.
- Local
- Specificity depends on anatomic location:The heart
Synaptic cleft
The narrow gap that separates the presynaptic neuron from the postsynaptic cell.
- Specificity depends on anatomic location and receptors
- We release a molecule in one direction to another
- Is a form of cell communication in that neurons signal each other through synapses
Paracrine
Release from a cell and acts on cells nearby
- Ex: Nitric Oxide- Passes through other cells to eventually raise blood levels
Autocrine
Release from a cells and acts on the same cell
Endocrine
Releases into the blood and travels throughout the body and can act on any site
If blood glucose falls to low
A. the medulla oblongata is stimulated to release insulin
B. pancreatic islet cells are stimulated to release glucagon
C. the liver is stimulated to take up glucose
D. blood glucose increases by positive feedback
B. pancreatic islet cells are stimulated to release glucagon
- the liver would be stimulated to release glucose to bring blood sugar back up
- blood glucose increases by negative not positive feedback
Two ways for a cell to receive outside inputs despite membrane barrier
Method 1
Membrane-permeable (lipid soluble) signaling molecule
- can cross directly into the cell and it binds to the receptors which are inside the cell or nucleus
- Ex: Steroids like testosterone, aldosterone, estrogen
Two ways for a cell to receive outside inputs despite membrane barrier
Method 2
Receptors bind signaling molecule outside the cell. -Binding of signaling molecule → change in receptor conformation -Shape change activates second messenger signal -Second messenger(s) change activities of cell
- can’t cross plasma membrane so there must be a surface receptor which will then interact with 2nd messengers which are inside the cell. This causes effects to happen
- Ex; GPCR and Ligand gated ion channels
The Action Potential
The active propagation of a
membrane depolarization along the surface of
an excitable cell.
- channels open and close to move excitation
Action potential is essential for
function of excitable cells. Ex: neurons, cardiac myocytes, skeletal muscle myocytes
Membrane potential
a measure of charge inside the
cell relative to outside.
Depolarization
cell membrane potential is MORE POSITIVE than rest (MORE EXCITABLE)
- inside the cell is more positive than outside
Repolarization
cell membrane potential is returning to rest (usually from depolarization)
Hyperpolarization
cell membrane potential is MORE
NEGATIVE than rest (LESS excitable)
- inside the cell is more negative than the outside
Our plasma membrane is
a lipid bilayer which is hydrophobic
No ion can cross membrane by itself
- Membranes excludes and separates individual ion species
Electrical Potential
Electrical gradient
Difference in net charge at
inner & outer face
- Charge of outside relative to inside
Chemical gradient
concentration gradient
Difference in net concentration of an ion
Energy favors ion flow
down concentration gradient from high to low
Chemical gradients
Stored energy
- Cell uses energy ( ATP) to pump ions to create gradient (slow)
- Cell then uses energy from gradient to drive other processes (fast or slow)
Abbreviation for membrane potential
Em
- difference in voltage across membrane
How can membrane potential exist?
By convention
outside= 0 mV
- measure inside relative to outside
- Em = -70 mV, then inside is 70 mV more negative than outside
Which ions have a high concentration OUTSIDE the cell?
NA+, K+, Ca 2+
Which ions have a high concentration INSIDE the cell?
Cl-
Na/K pump
Helps to maintain Na+ and K+ chemical gradients
- 3Na+ out, 2 K+ in per 1 ATP
K+ channel (leak)
Passive K+ flow sets membrane potential (Em) near -70 mV
- Open channel which constantly leaks out K+
Voltage-Gated Ion Channels: Close/Inactivated
Channel conformation
blocks ion passage
through pore
Voltage-Gated Ion Channels: Open
aqueous pore spans entire
membrane, ions can
transit pore
Voltage-Gated Ion Channels: Activation
Focus on depolarization gated channels • Membrane depolarization → conformational change → opens pore → ions transit channel
Na channels have a ____ activation whereas K channels have a ____
Fast, slow
Action Potential diagram
Rising (Upstroke- Na+ enters)
Falling ( Downstroke- K+ exits
Axon Initial Segment (AIS)
site of action potential generation
-ion channels concentrated at AIS
What is a G protein coupled receptor (GPCR)?
Largest family of membrane receptors
• Many diverse families of GPCR
• 7 transmembrane domains
• Extracellular stimulus/signaling molecule binds to GPCR outside cell
• GPCRs form a complex with G proteins inside cell
• G proteins are a heterotrimer of G protein α, β, and γ subunits
• Stimulation of GPCR causes Gα and Gβγ to depart receptor and activate
separate signaling cascades.
• Uses GTP for energy
What are the two most important factors in determining resting membrane potential?
Na/K pump and K leak channels
