Lecture 1 Flashcards
Homeostasis
A dynamic range of conditions that is achieved via positive and negative feedback. Any wavering outside of these set range of conditions introduces the setting for disease.
Positive Feedback
Actions done to facilitate (continue in the same direction) the disturbance. Not seen very often. Usually pathologic if seen (Ex: Tumor producing increased sodium).
Negative Feedback
Actions done to inhibit any further changes, and ultimately reverse the direction of the disturbance.
Physiologic Examples of Positive Feedback
-Parturition (Childbirth)
-Lactation
-Coagulation
Parturition and Lactation result in increased oxytocin.
Example of Negative Feedback
When we are hypotensive due to dehydration, the kidney senses this and activates the RAAS. Aldosterone causes us to hold onto sodium, which holds onto water. This increases our blood volume to increase our BP.
Purpose of Homeostasis
To maintain constant ECF composition through positive and negative feedback. Involves nutrient delivery (ions, glucose levels, etc), removal of metabolic waste (such as BUN), protection, and regulation of body functions.
Cell
The smallest unit that is capable of all the functions of life and is therefore the primary location of all physiologic and pathological processes in humans.
Structure
determines function
Function
determines structure
Plasma Membrane
Made up of a phospholipid bilayer. Purpose of it is to separate fluid compartments (separate ICF from ECF).
Organelle and Cell Membrane
Within a cell, all organelles have the same membrane. This allows for trafficking of materials between cell membranes and organelle membranes.
Ex: Phagocytes eat toxins, and form a membrane around toxin. It can then fuse with lysosomes, which have the same membrane. this allows the toxin to be broken down.
Plasma Membrane Makeup
- Hydrophilic Heads
- Chains of hydrocarbons (Fatty Acids)
- Cholesterols
- Proteins
- Carbohydrates
Hydrophilic Heads
Composed of glycerol (3 carbon compound) and phosphate (PO4). Phosphate carries a charge, which allows the head of the phospholipid to interact with water.
Chains of Hydrocarbons (Fatty Acids)
A component of the plasma membrane. A hydrophobic area attached to the glycerol. Allows for separation of fluids.
Cholesterols
A component of the plasma membrane that allows for membranes to be flexible and allows cells to move in a fluid fashion. The less of this, the more rigid the cell.
Proteins
Ion Channels, Receptors, etc. that can go through the membrane. Also serve as a point of attachment for the cytoskeleton to the membrane (Anchoring site).
Carbohydrates
A component of the plasma membrane that can be attached to proteins or to the phospholipids. Used for cell signaling and for identification. Helps recognize our cells as “self”. Also, there are receptors that allow the cell to move and be mobile.
Cytoskeleton
Gives support and structure to cells. Composed of microfilaments (thin fibers composed of actin), intermediate filaments (composed of actin), and microtubules (composed of tubulin). Regulate cell movement (migration, contraction, division), movement of vesicles within cells, and act in cell signaling processes.
Microvilli
Cytoplasmic extensions containing microfilaments which increase cell surface area for absorption.
Cilia
Long, slender extensions of plasma membrane; composed of microtubules (9 groups of pairs surrounding a central pair) anchored to cell surface with basal body; beat rhythmically to move fluids or secretions across cell (respiratory and reproductive tracts)
Centrioles
Cylindrical structures composed of microtubules (9 groups of triplets); two in each centrosome; control movement of DNA strands during cell division
Ribosomes
Made of ribosomal RNA (rRNA) and proteins. Can be bound (Rough ER) or free in the cytoplasm. The site of polypeptide synthesis.
Ribosomes
Synthesize polypeptides (the primary structure of proteins). Made of small and large subunits that sandwich a strand of mRNA to read the codon, and then tRNA comes to bind a new Amino Acid to the chain.
Free Ribosomes
Free in cytoplasm that are synthesizing polypeptides that will be used BY the cell, WITHIN the cell.
Bound Ribosomes
Found in the rough Endoplasmic Reticulum. Usually are synthesizing proteins that are then shipped out (ex: Epinephrine, acetylcholine, etc.)