Homeostasis
Three internal factors maintained by Homeostasis
- Temperature
- Water concentration
- Blood glucose levels
- pH of blood / cells
A dendrite...
Receives signals and transmits them to the cell body
What is down-regulation?
The decrease in the number of receptors on the membrane of a cell to reduce its sensitivity to a hormone.
Explain the difference between hypothermia and hyperthermia
Hypo - drop in internal temperature (cold), Hyper - increase in internal temperature (hot)
What four ways do animals lose water?
- Breath
- Perspiration (sweat)
- Urine
- Faeces
Define homeostasis
The term used to describe a constant internal environment within a living organism despite internal or external changes.
What is Exocytosis?
Vesicles surround molecules, carry them to the outer edge of the cell membrane, and fuse with the membrane to release the molecules outside the cell
An example of a steroid hormone
- Oestrogen
- Progesterone
- Testosterone
- Cortisol
What is an Endotherm?
Animals, such as mammals, that generate most of their heat by internal metabolism.
What is a Xerophyte?
Plants that live in very dry environments
An example of a negative feedback loop
Any negative feedback loop i.e. blood glucose levels, thermoregulation, osmoregulation
What is a synaptic cleft?
The small space between neurons
What gland is the 'Master gland'?
Pituitary gland
What is Kleptothermy?
The tendency of some organisms to share body temperature in order to stay warm – often occurs through huddling
What does ADH (antidiuretic hormone) do?
Increases the amount of water absorbed in the collecting ducts, specifically the proximal tubule and loop of Henle.
An example of a positive feedback loop
Any positive feedback loop i.e. pregnancy contractions, albedo effect (snow and reflection of heat)
How does a myelin sheath increase the speed of an action potention?
Action potential skips from node to node (space between myelin sheaths), increasing the speed that the action potential moves
What are the three steps of hormone function?
1. Reception - hormone attachment to the receptor
2. Signal transduction - signal conversion in the cytosol
3. Induction - response
What is Vasodilation?
Blood vessel expansion to increase heat lost to the environment.
What does ABA (abscisic acid) do?
Causes guard cells to close therefore reducing the transpiration in plants (reducing water loss)
What is the receptor of pain?
A Nociceptor
Steps of a reflex arc
•Stimulus is detected by a receptor
•An action potential (nervous signal) is generated in a sensory neurons and travels to the spinal cord through the dorsal root
•Within the grey matter of the spinal cord, the sensory neuron activates an interneuron which immediately connects and signals a motor neuron
•Motor neuron leaves through the ventral root
and activates the effector (a muscle) to cause a
movement
Can amino acid based hormones cross the cell membrane?
Amino acid based hormones are hydrophilic, they are unable to cross the cell membrane and instead attatch to receptors on the surface of the membrane.
How does insulin production influence body temperatures?
Insulin release is inhibited, resulting in higher levels of blood sugar. These higher blood sugar levels allow for greater cellular respiration to take place, and therefore heat to be produced.
Three differences you can expect to see on a mesophyte compared to a xerophyte
- thinner cuticles
- more stomata
- larger and thinner leaves
(compared to xerophytes)