Lecture 11- Homeostasis Flashcards
What is homeostasis?
The steady state of physiological conditions in the body
True or False: All living things regulate internal conditions in some way.
True. Homeostasis is a basic characteristic of living things.
Negative Feedback regulation
Response to a stimulus reduces stimulus.
This is the most common type and works to oppose the initial change. Imagine your room getting too hot. The sensor detects the rise in temperature, and the control center tells the effectors (sweat glands) to kick in, cooling you down and bringing the temperature back to the set point. Examples include thermoregulation, blood sugar regulation, and blood pressure regulation.
Which type of feedback regulation is more common?
Negative feedback (reduce stimulus)
Positive Feedback regulation
Response to stimulus amplifies stimulus- less common.
This less common type amplifies the initial change. One example is childbirth. As the baby pushes down, it triggers the release of a hormone that causes stronger contractions, further pushing the baby down. This positive loop continues until birth, then stops with the removal of the stimulus (the baby),
Osmoregulation
The process by which organisms manage their internal water and salt balance. It’s essentially all about keeping the right amount of water and electrolytes in their cells and fluids to function properly.
Osmoregulation/maintaining homeostasis- Paramecium
Paramecium is a unicellular protist (SAR clade) and generally aquatic (freshwater). The solute inside the cell is greater than the outside (outside the cell is a hypotonic environment). Due to osmosis, water naturally moves from an area of low solute concentration (freshwater) to an area of high solute concentration (the paramecium cell). This can cause the paramecium to take in too much water. To remedy this, the paramecium has a CONTRACTILE VACUOLE which is an organelle for osmoregulation. The contractile vacuole pumps water out to maintain water balance and prevent lysis (bursting) of the cell.
What is the organelle for osmoregulation and what does it do?
Contractile vacuole, pumps water out to maintain water balance and prevent lysis.
Osmoregulation/maintaining homeostasis- Jellyfish
Phylum Cnidaria. Disploblastic development -> 2 adult tissue layers. No dedicated circulatory system- all water movement via diffusion.
Diffusion= molecules move from an area of high concentration to an area of low concentration. Jellyfish passively matches the surrounding salinity to avoid major water imbalances.
“Flat” morphology
Osmoregulation/maintaining homeostasis- Humans
Terrestrial Animals.
Animals first evolved in oceans. Take our marine environment with us on the inside. Have to keep it and maintain conditions- gases, pH, etc.
Terrestrial Adaptations for maintaining homeostasis
Reproduction/development- Amniotic sac
Water balance- Scales/skin, Excretory system
Homeostasis for smaller, aquatic/marine vs. larger, terrestrial
Smaller, aquatic/marine- often osmosis/diffusion
Larger, terrestrial- dedicated transport tissues to prevent desiccation, maintain pH, solute
Homeostasis in Animals- basic constraints
Body size/shape limited by physical laws
Strength, diffusion, movement, heat exchange also limited by physical laws
Example: Shape of Swimming Animals
Problem: Limited by water, denser, more viscous than air
Solution:
-> smooth body
-> streamlined shape
Diverse organisms, same environment (seal, penguin, tuna etc)
Convergent evolution- selection favors similar adaptations
Explain the exchange animals have with their environment.
Animals are not closed systems. They exchange nutrients, gases, and waste with their environment. These materials are typically transported as dissolved materials in H2O across the cell membrane. The way animals exchange with their environment affects their body plan.
(Think of coelomates vs. acoelomates. Coelomates are more complex and have space for internal organs. This facilitates efficient exchange and a well-developed circulatory system to transport materials throughout the body, which enables larger body sizes and increased complexity. Aceolomates lack a coelom, a fluid-filled body cavity. Due to the absence of a coelom, most of their cells are directly in contact with the environment, limiting their body size.)
