Week 1 - Control of the Internal Environment: Homeostasis, Exercise & Adaptation Flashcards
Homeostasis
maintenance of a constant and “normal” internal environment
“It is the process by which we adapt and adjust to changes in our environment to maintain our functional integrity.”
Hormesis
refers to a biological process in which low-to-moderate doses of a potentially harmful stress results in a beneficial adaptive effect
Define steady state exercise and explain how it differs to homeostasis.
where physiological variables are unchanged (HR, VO2, Bp) but this doesn’t necessarily mean “normal”
its the balance between demands placed on the body and the body’s response to those demands
What are the two biological control systems of the body?
1) Intracellular control systems: protein breakdown/synthesis, energy production, maintenance of stored nutrients (fats and carbs)
2) Organ systems: pulmonary and circulatory systems, replenish oxygen and remove carbon dioxide
What are the 3 general components of a biological control system?
Receptor, control center, and effector.
Describe the principles that underlie physiological control of variables.
Peripheral receptors/ sensors
- detect changes in the internal conditions of the body (peripheral organs and tissues) and send this afferent information to the brain ‘centres’ which processes and integrates this - (compares present value with desired value)
Control center
- send efferent information to effector organs/tissues either through nerves or hormones (or both) to negate (negative feedback) or to amplify (positive feedback) the change.
Effectors
- bring the internal environment back to normal (negative feedback) or amplify the changes (positive feedback).
What are the two classes of biological control systems?
Negative and positive feedback
Define negative feedback and provide an example.
where the response reverse the initial disturbance in homeostasis and restores normal values
Example: respiratory systems control of C02 concentration in extracellular fluid (blood)
- Increase in extracellular C02 triggers a receptor/sensor
- Sends afferent information to respiratory control center
- Respiratory muscle activated to increase breathing
- C02 concentration returns to normal
Other examples: blood pressure, heart rate, body temperature
Positive feedback
Biological responses amplifies the original stimulus (change)
Example: Childbirth
- Initiation of childbirth stimulates receptors in cervix and sends message to the brain to release oxytocin from pituitary gland
- Oxytocin promotes increased uterine contractions
Other example: clotting of blood after cutting yourself
What is the “Gain” of a biological control system?
the degree to which a control system maintains homeostasis - pulmonary and CV systems have large gains (thus more capable of maintaining homeostasis)
Explain the regulation of body temperature in response to exercise.
What happens to effector organs/tissues if core body temperature drops?
Body temperature rises as exercise generates heat from working skeletal muscles.
Thermoreceptors detect this change in internal environment of the body and will send afferent information to the hypothalamus (control center).
The hypothalamus sends efferent information to effector organs and tissues which causes the increase in heat loss mechanisms (dilation of blood vessels and activating sweat gland secretion).
This negative feedback response limits the increase in core body temperature and creates a steady state where heat gain from exercise and heat loss is balanced.
If core body temperature drops, effectors constrict blood vessels and sweat glands are inactive.
Adaptation
refers to a change in the structure and function of the cell or organ system (often in response to exercise) that results in an improved ability to maintain homeostasis during physiologically stressful conditions (exercise)
Acclimation
adaption to environmental stresses (e.g. heat or hypoxic stress), which results in an improved function of existing homeostatic systems
Define Hormesis.
What model can explain exercise-induced hormesis?
is the process in which a low-to-moderate dose of potentially harmful stress results in a beneficial adaptive response on the cell or organ system
Exercise-induced hormesis refers to the Inverted U shape model where there is an optimal intensity and duration of exercise stress to induce the greatest beneficial adaptive response - this varies between biological systems (CV, skeletal muscle) and people
5 different types of cell signaling pathways
Intracrine signaling
Juxtracrine signaling
Autocrine signaling
Paracrine signaling
Endocrine signaling