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4U Biology
Homeostasis
| Question | Answer |
|---|---|
| ADH (antidiuretic hormone) | secreted by pituitary gland; makes distal and collecting tubules more permeable to water |
| Aldosterone | secreted by adrenal glands; stimulates reabsorption of Na+ (by active transport) which then causes water to be reabsorbed in ascending Loop of Henle |
| active transport | going from low concentration to high concentration; requires energy in form of ATP |
| passive transport | going from high concentration to low concentration; does NOT require energy in form of ATP |
| hypertonic cell | having a higher concentration of solutes compared with the surrounding solution. Water moves in so concentrations are balanced. |
| hypotonic cell | having a lower concentration of solutes compared with the surrounding solution. Water moves out to balance concentrations. |
| homeostasis | process by which biological systems maintain a stable internal environment (within narrow ranges), even when external conditions change. |
| Negative feedback loop | counteracts a stimulus, bringing the system back to a set point eg. regulating body temperature or blood glucose |
| Positive feedback loop | amplifies the stimulus to push a process to completion eg. childbirth or ejaculation |
| neuron | nerve cell, made up of cell body, axon, terminal branches. Nerve impulse starts at dendrites on cell body and moves toward terminal branches |
| myelin sheath | layer of fatty Schwann cells that insulate the nerve impulse, allowing it to move faster |
| sensory neuron | transmits impulse from sensory organs to the brain |
| motor neuron | transmits impulse from the brain to muscles, glands, and organs |
| interneuron | connects motor and sensory neurons |
| Saltatory conduction | nerve impulse is prevented by Schwann cells from flowing along the axon. Instead, the nerve impulse jumps from one Node of Ranvier to the next Node. This kind of transmission is much faster |
| neurotransmitters | chemical messengers that transmit signals from neurons to target cells (may be muscles, glands or other neurons). They cross the synapse and bind to specific receptors on the post-synaptic membrane |
| depolarization | Na+ gates in the axon open, allowing sodium ions to flow into the axon in response to a stimulus. |
| resting potential | at rest, the inside of the neuron is more negative than the outside, creating a polarised cell. This difference is achieved by the sodium potassium pump, which moves Na ions from a low to high concentration using ATP. This restores the polarization. |
| wave of depolarization (nerve impulse) | If the neuron is stimulated, the axon becomes deploarized. This depolarization moves down the axon (in one direction) in a wave. The axon becomes re-polarized behind this wave. |
| sodium-potassium pump | restores the resting potential. This mechanism moves 3 sodium ions out and moves 2 potassium ions in, so there is a net neg charge inside neuron. |
Created by:
jcepella