Homeostasis Flashcards
U4L1 (14 cards)
What is homeostasis?
Homeostasis is the ability of an organism to maintain a stable internal environment, despite changes to its external environment/surroundings.
All organs work together to achieve homeostasis.
What is the organization of a human?
Organelles, Cells, Tissues, Organs, Organ Systems, Organisms.
How does homeostasis work?
Homeostasis works by using feedback pathways (negative in the body typically).
Organs/structures communicate with eachother in response to changes in the body.
What is the cellular relay chain?
Stimulus, Sensor (receptor), Afferent pathway, Integrating center, Efferent pathway, Target (effector), Response.
This loops to form what is called a negative (or positive) feedback loop.
What is the receptor?
The receptor is responsible for sensing stimuli (change in temperature).
These monitors send signals through the sensory pathway.
These signals (afferent pathway), go to the brain (integrating center).
What is the Integrating centre?
The integrating centre (brain). This center takes the signals and sends them through the motor pathway to the regulator to restore a normal balance.
The signal than travels away from the brain to reach its destination (afferent pathway).
What’s the effector?
The effector(s) (muscles, glands), responds to the stimuli and brings the body back to homeostasis.
What is negative feedback?
Negative feedback is a process in which a mechanism is activated to restore conditions to their original state.
The response OPPOSES the stimuli. It ensures that small changes won’t become to large.
What’s an example of Thermostat and Homeostasis?
So thermostat is at 21C. The temperature in the room drops to like 19C, this is the stimulus.
The stimulus gets picked up by the sensor (the thermostat) which then gets sent to the CPU of the thermostat. The signal gets sent (afferent pathway) to the CPU (integrating-centre).
The CPU processes this change and sends a signal to the thermos to turn it on (efferent pathway).
The effector (furnace) turns on, and heats the home up which is the response. Once the room reaches the pre-set temperature, the thermos will turn off.
What is thermoregulation?
So, humans have an ideal temperature (36.2, 37.2C). Anything above is hyperthermia and is typically a symptom of infection (fever) or heat stroke.
Anything lower is Hypothermia and can lead to cell death (frostbite).
How does thermoregulation work?
So basically, thermoreceptors that are connected to the nervous system sense changes in body temperature.
They send these messages via sensory neurons up to the brain.
The integrating sensor is the Hypothalamus. The hypothalamus sends signals via motor nerves to the sweat glands.
Effector: Sweat glands initiate sweating to help cool off the skin and body.
Blood vessels dilate to allow more blood to reach the surface of the skin. heat from blood is lost to the skin so blood can return to core of your body &
cool the internal organs.
The result is the body returns back to a normal temperature and the hypothalamus turns off the cooling system.
What about thermoregulation under cold stress?
Receptor: Thermoreceptors message the hypothalamus via sensory neurons.
Integrating center: Hypothalamus sends signal via motor neurons.
Target: Muscles begin to contract rapidly to produce heat to bring body temperature back up.
The skin also constricts which reduces blood flow to the surface and helps to keep the core warm.
Smooth muscles: Hair follicles stand up to trap warm air.
Skeletal muscles: They contract which causes shivering.
Result: Core temperature is risen back up to a stable temperature.
What are dueling hormones?
Insulin: Produced by B-cells by the pancreas. They are released into the circulatory system when glucose levels are high. They essentially instruct the cells to take in more glucose.
Glucagon: Produced by A-cells of the pancreas. They are released into the circulatory system when blood levels are low. It signals the liver to break down glycogen into simpler glucose in order to be used by the cells (glycogen is a polysaccharide).
What’s an example of positive feedback?
An example of positive feedback is childbirth.
The head of the baby touches the cervix. Nerves sense this and they send a signal to the brain. The brain than simulates the pituitary gland to release Oxytocin, Oxytocin is brought to the uterus (via bloodstream). Oxytocin stimulates cervix contractions to help push the baby out (labour).
More examples include apple’s ripening and blood clotting during a wound.
