Lecture 22: Homeostasis & The Endocrine System Flashcards
(32 cards)
Define homeostasis
Maintaining a relatively constant internal environment that differs to the external environment and remains constant even when there are environmental changes
What is the negative feedback system and what are the components?
A mechanism by which animals that regulate internal environments achieve homeostasis
It is a loop that detects a change that triggers a response to REDUCE the stimulus
- set point
- stimulus
- sensor
- control center
- effector
- response
Describe the set point of a negative feedback system
a variable maintained near a particular value
ex. body temperature at 37 degrees celsius
Describe the stimulus of a negative feedback system
anything that fluctuates the variable above or below the set point
ex. a change in salinity
Describe the sensor/receptor of a negative feedback system
Recognizes the stimulus and sends information to the control centre
Describe the control centre of a negative feedback system
Triggers a response
ex. the hypothalamus
Describe the effector of a negative feedback system
Carries out a response
ex. muscles or capillaries
Describe the response of a negative feedback system
Whatever activity brings the variable back to the set point –> reduces the stimulus
ex. sweating to cool body temperature down
Define thermoregulation
The process by which animals maintain an internal temperature within an optimum range that can differ from the external environment
Define endotherms and ectotherms - give examples of animals
endotherms: use internal metabolism to produce heat to maintain body temperature
- ex. birds and mammals
ectotherms: have body temperatures that are determined by external conditions
- ex. amphibians, reptiles (not birds), most fish, invertebrates
Describe the steps of the negative feedback loop of thermoregulation for body temperature increase
- set point/homeostasis: internal body temperature around 37 degrees C
- stimulus: body temperature increases above set point
- sensor/receptor: warm temperature receipts detect stimulus and signal the thermostat in the hypothalamus
- control centre: hypothalamus triggers a response in the effectors
- effectors:
- blood vessels/capillaries in skin dilate to fill with blood and bring to skin surface so heat can radiate out of body
- sweat glands secrete sweat to evaporate out of body –> cools body - response: sweating and heat loss reduce body temperature (stimulus) back to the set point and stops the loop
Describe the steps of the negative feedback loop of thermoregulation for a body temperature decrease
- set point/homeostasis: body temperature around 37 degrees C
- stimulus: body temperature decreases below set point
- receptors: temperature receptors detect stimulus and signal thermostat in hypothalamus
- control centre: hypothalamus activates warming mechanisms in the effectors
- effectors:
- skeletal muscles contract rapidly to cause shivering and generate heat
- blood vessels in skin contract to reduce heat loss through surface - responses: muscle contractions and capillary contractions reduces stimulus by increasing body temperature to set point and stopping the loop
Describe the endocrine system
A system that regulates the body by short- and long-distance CHEMICAL signalling between cells and organs
define hormone
Molecules that function as chemical signals that are secreted by the endocrine system (usually an endocrine gland) that circulate throughout the body in the blood in order to trigger a response
define target cells
cells that have the specific receptor molecules to which a hormone binds and can respond to the signal
some target cells can have receptors for multiple hormones
define endocrine gland and distinguish it to an exocrine gland
Endocrine glands are DUCTLESS glands that secrete hormones directly into interstitial fluid surrounding cells.
- ex. adrenal glands, pituitary glands
Whereas,
Exocrine glands have ducts and secrete substances OUT of the body (through digestive tract or surface).
- ex. sweat glands, salivary glands, mammary glands, the pancreas
How does the hypothalamus interact with the anterior and poster pituitary glands
The hypothalamus receives information from nerves throughout the body and responds by initiating appropriate endocrine signals that travel to the pituitary gland
What is the posterior pituitary glands role?
the PPG is an extension of the hypothalamus that stores hormones produced by the hypothalamus
It receives hormones from neurosecretory cells of the hypothalamus that trigger the PPG to secrete the stored hormones in response to a nerve (electrical) impulse sent from the hypothalamus
Which 2 hormones are released from the posterior pituitary gland?
Antidiuretic Hormone: sent to the kidneys
Oxytocin: sent to the mammary glands and uterine muscles
What is the anterior pituitary glands role?
synthesizes and secretes its own hormones in response to a hormonal signal from the hypothalamus.
Many of the hormones synthesized by the APG regulate the function of other endocrine glands or cells
Describe the function of the pancreas, what are the main hormones produced by it?
The pancreas is an endocrine gland that functions in GLUCOSE HOMEOSTASIS by responding to blood glucose levels by releasing a hormone into the blood
- insulin
- glucagon
Describe the function of the thyroid glands
releases hormones regulating - blood pressure
- heart rate
- muscle tone
- digestive functions
- reproductive functions
describe the function of the adrenal glands, what are the main hormones produced by it?
releases stress hormones (epinephrine and norepinephrine)
to trigger fight or flight responses (related to the sympathetic nervous system)
Describe the role of ADH
released by the Posterior pituitary gland in response to high salt concentration in the bloodstream via an electrical signal from the hypothalamus. This occurs when there is too much water loss and a high salt concentration in the blood. It is sent to the collecting duct of the kidney to increase the permeability of the collecting duct to reabsorb more water and reduce further water loss.
