Week 1 Physiology Flashcards
Homeostasis
State of body equilibrium or stable internal environment of the body, achieved through coordinated physiological activity
Feedback loops
A process conducted by the body in response to a change to maintain homeostasis
Features of a feedback loop
- Stimulus
- Receptors
- Control centre
- Effectors
- Response
Stimulus
Disrupts homeostasis by increasing or decreasing a controlled condition
Receptors
Detects the change in environment, sends nerve impulses or chemical signals to the control centre (brain)
Control centre (brain)
Receives the input and provides nerve impulses or chemical signals to the effectors, giving an idea of how to respond to the change
Effectors
Bring about a change or response to return to homeostasis
Response
Alters the controlled condition
Types of feedback loops
- Negative feedback
- Positive feedback
Negative feedback loops
Feedback which reduces (or opposes) the intensity of the original stimulus
Examples:
* Blood pressure
* Glucose levels
* Respiratory rate
* Water reabsorption by kidneys
* pH level of blood
* Body temperature
Positive feedback loops
Feedback which increases (or enhances) the intensity of the original stimulus
Examples:
* Stretching of the cervix during childbirth
* Production of prolactin (breast milk)
* Blood clotting (heal wounds by forming a scab)
3 main components of cells (name)
- Cell membrane
- Cytoplasm
- Nucleus
Cell membrane
- Outer barrier of the cell
- Regulates what crosses the membrane - enables the cell to have a stable environment
- Phospholipid bilayer
- Selectively permeable
- Generally negatively charged
Cytoplasm
Intracellular fluid that contains organelles (e.g. cytosol, organelles)
Nucleus
Contains our genetic material – DNA (e.g. chromosomes, genes)
Osmosis
Diffusion of water molecules across membrane
Hypertonic solution
High solute concentration
Hypotonic solution
Low solute concentration
Isotonic solution
Equally solute concentration
Concentration gradient
Underlies the movement in all types of active transport, is the force of movement
Moving down the concentration gradient
Moving something from an area of high concentration to an area of low concentration
Moving against the concentration gradient
Moving something from an area of low concentration to an area of high concentration
Membrane transport processes
Passive transport - no energy required:
* Simple diffusion
* Channel-mediated facilitated diffusion
* Carrier-mediated facilitated diffusion
Active transport - lots of energy required, force of movement is adenosine triphosphate (ATP):
* Primary active transport
* Secondary active transport
Simple diffusion
Non-polar and non-charged particles pass through easily, no facilitation required (e.g. oxygen, carbon dioxide)
Channel-mediated facilitated diffusion (definition)
Requires protein channel to help electrolytes cross the membrane (e.g. potassium, sodium, magnesium, calcium)
Carrier-mediated facilitated diffusion (definition)
Requires protein carrier, changes shape to allow large substances to cross membrane (e.g. trans membrane proteins such as glucose)
Primary active transport (definition)
- Uses sodium potassium pump (most common)
- Uses ATP directly
- Rule: pumps out 3 sodium ions against the concentration gradient and pumps in 2 potassium ions down the concentration gradient
- Allows the cell to maintain its specific negative charge
Secondary active transport (definition)
- Sodium movement enables electrolytes and vitamins to cross the membrane
- Can only occur after primary active transport has occurred first as it sets up a concentration gradient of sodium by moving sodium out of the cell
- Allows sodium ions to move back down its concentration gradient passively
- Can take a second molecule across with it
- Uses ATP indirectly
- Allows glucose and amino acids to easily enter the cell
- Involves symporters and antiporters
Symporters
Two molecules can cross the protein in the same direction (e.g. sodium and glucose, amino acids, electrolytes)
Antiporters
Two molecules can cross the protein in the opposite direction (e.g. sodium in, calcium or hydrogen out)
