Homeostasis Flashcards
WHat are cells?
Fundamental units of life
What are cell contents contained in?
Lipid belayer membrane
What are some common basic cellular functions of cells?
Perform specialised functions
Share mechanisms to change nutrients into energy
Deliver metabolism + catabolism products to surrounding fluid
Replicate + regenerate
What are cells bathed in?
Extracellular fluid - maintained in appropriate state to enable cells to function
Definition of cells:
Basic structural and functional unit
Definition of tissues:
Aggregates of cells with particular function
Definition of organs:
Specialised tissues plus connective tissue
Definition of systems:
Group of integrated organs that collectively perform a function
What are all parts of the body linked by?
Fluid
What do organ systems create?
Internal environment
How much of body is fluid?
60%
What is body fluid divided into?
Compartments
Intracellular - 70% fluid within cells
Extracellular - 30% fluid outside cells
What does extracellular fluid include?
Plasma
Interstitial fluid
What’s interstitial fluid?
Fluid between cells
What is regulation of intracellular ad extracellular fluid important for?
Functioning of organelles, cells, tissues, systems, organisms
What are fluid compartments separated by?
Membranes
How are body fluids balanced?
Need to balance intake and outtake
Definition of homeostasis:
Physiological control systems maintain relatively stable internal environment (within safe limits) in a fluctuating environment
What is homeostasis the result of?
Organised ‘self-government’
How is homeostasis maintained?
By control systems:
Within cells - genetics
Within/between tissues - nervous + endocrine system
Characteristics of control systems:
Require multiple elements
Many systems interlinked
Most use negative feedback
What may control systems be?
Open loop
Closed loop
Feedforward
Open loop control systems:
No feedback
Controller -> controlled component -> output
Closed loop control systems:
Output feeds back + influences controller
Controller -> controlled component -> output -> sensor -> feedback -> controller
Types of feedback in closed loop control system:
Negative feedback - return to set-point
Positive feedback - moves away from set-point
Feedforward control systems:
Response generated in anticipation of change
What isn’t open loop feedback influenced by?
Not influenced by resulting conditions - not useful for maintaining local homeostasis
Example of open loop feedback:
Glucose absorbed into gut epithelial cells
What is closed loop feedback influenced by?
Influenced by resulting conditions
Return to set point - maintains homeostasis
Characteristics of set point:
Dynamic and constantly adjusting
Thermoregulation:
Skin and hypothalamus receptors detect increased temperature
Effector responses begin to reduce temperature (e.g. by sweating, vasodilation)
Receptors detect temperature below set point
Effector responses begin to increase temperature (e.g. vasoconstriction)
What is hunting?
Overshooting and undershooting
What does the depth and extent of hunting depend on?
Properties of elements of feedback system
What does negative feedback control?
Controls system within limits
Arterial blood pressure:
What’s the sensor?
Baroreceptors - send signals to control centre
Arterial blood pressure:
What’s the control centre?
Solitary nucleus in medulla oblongata (set point) - identifies change in blood pressure
Arterial blood pressure:
What’s the effector?
Heart + blood vessels respond
Arterial blood pressure:
What’s the controlled variable?
Rise or fall in arterial blood pressure
Arterial blood pressure:
What does negative feedback involve?
Returns controlled variable to within safe limits
What’s gain?
Degree of effectiveness of negative feedback control system
How do you calculate gain?
Correction / error
What happens to output in closed loop feedback?
Output continually enhanced and moved further away from homeostasis
What would happen if there was no termination mechanism in closed loop feedback?
System would ‘run away’
Oxytocin:
Positive feedback
Induced uterine contractions in child birth
Characteristics of feed forward control:
Infrequent
Feed forward control - example
Digestive system
Sight/smell - response in GI tract - gut prepared for digestion
Local result = ingest a digested + nutrients absorbed
Overall result = nutrient levels controlled in blood
What’s adaptive control?
Feedforward responses can be changed over time and iterations
Summary of negative feedback:
Promotes stability
Summary of feed-forward:
Anticipates change
Summary of positive feedback:
Promotes change in one direction - instability might result in disease but not always
