Homeostasis Flashcards
In broad terms and in relation to homesotatic mechanisms, the body “effectors” are
Muscles and Glands
What are homeostatic responses generally aimed at maintaining ?
The internal Milieu, i.e. physico-chemical conditions in the ECF
Homeostatic mechanisms generally respond to …
A. changing variables, which therefore tend to oscillate
B. Deviations from the set point
What is negative feedback ?
When the effector negates the stimulus.
What is the difference between positive and negative feedback?
Positive feedback occurs to INCREASE the change or output: the result of a reaction is amplified to make it occur more quickly. Negative feedback occurs to REDUCE the change or output: the result of a reaction is reduced to bring the system back to a stable state.
What is a set point?
Is a balanced physiological value for a variable.
What is a sensor ?
Sensor or receptor monitors variations from the set point and detects the change.
What is integration?
The integration or control center takes the received information and sends signals to effectors.
What is an effector ?
any muscles or glands that receives information from the integrating center and acts to bring about the changes needed to maintain homeostasis.
What is oscillation?
The value always oscillates about the set point in a system controlled by negative feedback.
What is the difference between efficient and less efficient ?
The efficient has low tolerance for change and requires high levels of ATP.
A less efficient has high tolerance for change and it will take more time to response because oscillations will be larger.
What is a circadian rhythm ?
The set points of some controlled variables are not constantly and can vary, often with the diurnal (circadian) rhythm approximately a 24 hour daily cycle.
An example is the temperature (1 or 2 while slepping) and the cortisol secretion.
What are the components of human thermoregulatory homeostatic system when increasing the temperature?
1.Stimulus: blood temperature warmer than hypothalamic set point.
2. It activated the heat loss center in the hypothalamus: Skin blood vessels and integumentary system.
3. The body temperature decreases and the hypothalamus heat-loss center shuts-off
The body temeperature is usually ?
35.8c-38.2c
What happen with skin blood vessels and sweat glands work to decrease the body temperature?
*Skin blood vessels: they dilate capillaries become flushed with warm blood, heat radiates from skin surface.
*Sweat glands: secrete perspiration, which is vaporized by the body heat, helping to cool it down.
What are the components of human thermoregulatory homeostatic system when DECREASING the temperature?
1.Stimulus: blood temperature cooler than hypothalamic set point.
2. It activated the heat promoting center in the hypothalamus: Skin blood vessels and skeletal muscles
3. The body temperature increases and the hypothalamus heat promoting center shuts-off
What happen with skin blood vessels and skeletal muscle work to increase the body temperature?
The skin blood vessels: constrict blood is diversify from skin capillaries and withdrawn to deeper tissues; minimizes overall heat loss from skin surface.
What are the two types of receptor that participate in thermoregulation homeostasis?
*Shell or peripheral receptors
*Deep body temperature receptors
Describe how and why fever is generated, and what aspects of homeostatic control are altered during a feverish period
-During inflammation e.g. infection, autoimmune disorders, macrophages and other cells release cytokines- interleukins, tumour necrosis factor.
-Cytokines act on the hypothalamus - release prostaglandins which reseat the hypothalamic set point to a higher level- heat promoting mechanisms activated.
-Vasoconstriction, reduced heat loss, skin cools, shivering commences and chills as body temperature rises.
-Once the immune system (+antibiotics/antiviral drugs) has reversed the disease process, the hypothalamic set point returns to normal.
-Heat loss mechanism is activated
*Fever mau assist control of infections by increasing the metabolic rate, increasing phagocytic activity (neutrophils) and inhibition of bacteria growth (increased temperature, sequestration of iron, copper and zinc by the liver)
Describe one of the examples you were given of positive feedback.
Regulation of clotting
1. Break or tear in blood vessel wall
2. clotting occurs as platelets adhere to site and release chemicals.
3. release chemicals attract more platelets.
4.Clotting proceeds until brake is sealed by newly formed clot.
Give another example of positive feedback
1- push baby against the cervix
2. the cervical stretch
3. Stimulates the production in the hypothalamus of oxytocin
4. oxytocin is stored by the posterior pituitary and released in the bloodstream.
5. Oxytocin causes uterine contraction
the delivery of the baby stops the cycle
What is the difference between normal positive feedback
They are limited duration loops and they stop when the process had been driven to completion.
Where is the nephrone located?
In the kidneys
What does the nephron do ?
*It filters the blood fluid via nephrones
*Almost all of this fluid, and everything it contains is reabsorbed and returned to the body.
* Toxic wastes are excreted, and the amount of water and salt retained or lost in the final urine or will depend on the bodies needs.