Physiology 1: Intro to Homeostatsis

What is homeostasis as it relates to physiology?

* the state of "normalcy"
* it is the purpose of physiology and why we have the body functions we do- human preservation

negative feedback vs positive feedback

* negative reduces effect/eliminates original stimulus and opposes change eg. human body temp and shivering
* Positive feedback reinforces original stimulus or further from homeostasis eg. oxytocin released during childbirth

What is a sensor (receptor)?

* detects change


* Thermostat recognizes shift
* parathyroid gland with calcium levels

What is a control or integration center?

middle man- it recognizes the sensor's warning and tells another thing to fix it.

* Thermostat signals the furnace
* Parathyroid gland

What is the effector?

responds to the stimulus

* furnace
* Osteoclasts

Describe the order of negative feedback

* Sensor/receptor


* control/integration center
* effector

What 8 things have to stay at homeostasis?

* Carbon dioxide
* sodium ions
* potassium ions
* ammonia
* glucose
* amino acids
* Fatty Acids
* oxygen

What is feedback and the types?

* response after a detected stimulus
* positive and negative

What are the negative feedback steps for thermal regulation?

* Skin thermo receptors
* hypothalamus thermoregulatory center
* sweat glands secrete

What are the negative feedback steps for human blood pressure? Explain

* blood vessels
* brain
* heart
* When blood pressure increases, signals are sent to the brain from the blood vessels. Signals are sent to the heart from the brain and heart rate slows down, thus helping blood pressure to return to normal.

What are the negative feedback steps for blood sugar?

* insulin
* liver
* ??? storage..?
* Regulation of blood sugar in humans - When blood sugar rises, insulin sends a signal to the liver, muscles and other cells to store the excess glucose. Some is stored as body fat and other is stored as glycogen in the liver and muscles.

What are the negative feedback steps for Blood cell production?

* kidneys
* erythropoietin
* Production of human red blood cells (erythropoiesis) - A decrease in oxygen is detected by the kidneys and they secrete erythropoietin. This hormone stimulates the production of red blood cells.

What are positive feedback examples?

* blood clotting
* Fruit ripening: Once ripe, it gives off a gas known as ethylene (C2H4) through its skin. When exposed to this gas, the apples near to it also ripen. Once ripe, they too produce ethylene, which continues to ripen the rest of the tree in an effect much like a wave
* PROMPTES CHANGE

What is feedforward control? What are some examples?

* Initiation of a response in anticipation of the stimulus
* ie. nerves