Week 1 Lecutre 2 Homeostasis Flashcards
What is homeostasis ?
-Maintenance of relatively stable conditions in the bodys internal environment
-dynamic condition
- concerned with maintaining life
-interaction of multiple systems
Maintaining homeostasis
-All organ systems contribute to homeostasis
-Endocrine and nervous system are particularly important
-Maintain a stable internal environment and adapt to changes
-many variables are controlled by homeostasis eg blood pressure, blood glucose, ion balance, water balance
Organ systems interact to finely tune our internal environment
Control of homeostasis
-Restores the normal state of the body after disturbance
-External environment eg temperature
-Internal environment eg insufficient blood glucose
-Disturbance is normally mild and temporary
-Prolonged and intense disturbance can affect our health.
Regulation of our internal environment
-Feedback systems or feedback loop
- control system to maintain a variable within a given range following disturbance
- feedback system
- cycle or events
monitor, evaluate, effect a change, re- monitor
Stimulus (changes a controlled condition)
-> controlled condition (controlled variable)
Eg body temperature, blood pressure
Components of a feedback loop
Receptor> control centre > effector
Receptor- monitors change in a controlled condition
Sends input to a control centre
Afferent pathway
Eg nerve impulses or chemical signals
Microscopic structure
-Free nerve endings of first- order sensory neurones
-Encapsulated nerve endings of first- order sensory neurones
- separates cells that synapse with the first-order sensory neurones
Location and origin of stimulus
Exteroceptors = located at or near the external surface of the body
-provide information about the external environment
Eg, hearing, vision, smell, taste touch, pressure, vibration, temperature and pain
Interceptors = located in blood vessels, visceral organs, msucles and the nervous system
- provide info about internal organs
-generated nerve impulses not usually consciously perceived
Proprioceptors = located in muscles, tendons, joints and inner ear
Provide info about body position, muscle length and tension, and the position and movement of joints.
Type of stimulus
Mechanoceptors= sensitive to mechanical stimuli
Eg deformation, streching or bending of cells
- provide sensations of touch, pressure, vibration,proprioception, hearing and equilibrium.
Monitor the stretching of blood vessels and internal organs.
Thermorecptors = detect changes in temp
Nocieptors = respond to painful stimuli from physical or chemical damage to tissue
Photoreceptors = detect light that strikes the retina of the eye
Chemoreceptors = detect chemicals in the mouth (taste), nose (smell) and body fluids.
Osmorecptors = detect the osmotic pressure of body fluids.
Components of a feedback loop control centre
Control centre e.g brain sets the “set point “ of the variables
Evaluates input from receptors
Generates output as needed
Efferent pathway
Eg nerve impulses, hormones, chemical signals
Components of a feedback loop effector
Recibes output from the control centre
Produces a response that changes the controlled condition
Negative loop
Changes occurs in the opposite direction to the original stimulus
Eg desacerase in function or output
Eg blood pressure rises
Stimulus> controlled condition> receptors >control centre >effectors >response> return to homeostasis when blood pressure back to normal.
Positive loop
Changes occurs in the same direction to the original stimulus
Eg increase in function or output
Childbirth
Stimulus increasing> controlled condition >receptors > control centre > effectors >response > increased streching or the cervix > interruptions of the cycle = the birth of the baby
Body fluids
-Homeostasis maintains the volume and composition of body fluids
- intracellular fluid -inside cells
-Extracellular outside cells
Interstitial fluid - between cells of tissues
Blood vessels- plasma
Lymphatic vessels - lymph plasma
CNS- cerebrospinal fluid
Joints - synovial fluid
Eyes - aqueous humor and vitreous body
Why do we need homeostasis?
Prevent injury, infection, developing diseases, lifestyle, genetics
