Homeostasis, Exercise and Adaptation Flashcards
Homeostasis ………
Maintenance of a constant and “normal” internal internal environment
Steady state exercise ……….
Physiological variable is unchanging, not necessarily “normal”.
Balance between demand and bodies response to demand
Homeostasis - dynamic constancy - Arterial blood pressure as an example.
Arterial blood pressure oscillates over time, however, the mean arterial blood pressure stays relatively constant (at rest).
What is the typical resting mean arterial blood pressure in humans?
93 mm Hg
What happens to an individuals ability to regulate blood pressure if they have a spinal cord injury?
Dysregulated balance between the sympathetic and parasympathetic nervous system resulting in fluctuation of mean arterial blood pressure. This dysregulated balance is caused by a deficient baroreflex.
Examples of intracellular control systems
Protein breakdown and synthesis
Energy production
Maintenance of stored nutrients
Examples of organ control systems
Pulmonary and circulatory systems
Replenish oxygen and remove carbon dioxide
Basic model for biological control systems
Stimulus (change in environment)
Sensor/receptor detects the change in variable
Afferent information from peripheral to control centre (Brain centres)
Brain processes and comes up with a response
Efferent information sent to the effectors (e.g. muscles, glands)
Effectors nullify the variation and return conditions to normal
Negative feedback loop
Response reverses the initial disturbance in homeostasis. E.g. increase in extracellular CO2 triggers receptor, info sent to respiratory control centre, respiratory muscles are activated to increase breathing, CO2 levels return to normal.
Positive feedback loop
Biological response increases the original stimulus’ effect. E.g. initiation of childbirth stimulates receptors in cervix, impulse is sent to brain to release oxytocin from pituitary gland, oxytocin promotes uterine contractions, contractions cause an increase in oxytocin release, therefore; process will continue until the baby is born.
Feedforward
Results in physiological responses in anticipation of a change in a variable. E.g. anticipatory rise, increasing Hr in anticipation to the commencing of exercise.
Gain/ (sensitivity of the response) (Example)
Degree to which a control system maintains homeostasis. E.g. Pulmonary and cardiovascular systems have large gains (thus more capable of maintaining homeostasis).
Regulation of body temp
Temperature change in the body (stimulus)
Thermoreceptors throughout the body detect
Afferent information is sent from thermoreceptors to hypothalamic brain centre
Centre identifies increase in temp and sends efferent information to the tissues and organs
Effectors; Skin blood vessels, sweat glands and skeletal muscle.
Effectors respond to change, resulting in a normal body temp.
Regulation of blood glucose (simplified)
Requires the action of hormones (insulin and glucagon)
Insulin being the storage molecule (high blood glucose levels)
Glucagon causing a release of glucose from glycogen and production of new glucose molecules (gluconeogenesis) (low blood glucose levels)
What individuals are unable to regulate their blood glucose control systems?
Diabetics
Regulation of cellular homeostasis
Stress proteins (heat shock proteins)
Repair damaged proteins to restore homeostasis in response to changes in pH, temperature and free radicals.
Why is exercise a major test for homeostatic control?
Exercise disrupts homeostasis by changing cellular pH, PO2, PCO2 and temperature.
Difficult to achieve a steady state; therefore, fatigue and cessation of exercise.
Definitions of Adaptation
Change in structure + function of cells/organs
Causes improved ability to maintain homeostasis but occurs much more slowly
Many adaptive changes occur in the cells and are linked to genetic changes.
Definition of acclimation
Adaptation to environmental stresses (E.g. heat or hypoxic stress)
Results in improved function of existing homeostatic system
Change in phenotype that is reversible and occurs very rapidly (sometimes in a few mins)
Definition of hormesis
Process in which low-moderate dose of potentially harmful stress (e.g. chemical agent/ environmental stress) results in a beneficial adaptive response on the cell or organ system
Cell signalling
Communication between cells using chemical messengers (CM)
Coordinates cellular activities
Important for maintaining homeostasis
Five types of signalling:
Intracellular signalling
Juxtacrine signalling
Autocrine signalling
Paracrine signalling
Endocrine signalling
Intracrine signalling
CM inside cell triggers response
Juxtacrine signalling
CM passed between two connected cells
