Organisms' interaction with the environment flashcards

Topic 4: Organisms' interaction with the environment

The reflex arc, in order

Stimulus detected by a receptor → impulses along a sensory neurone to the CNS → chemical released at a synapse → relay neurone → synapse → motor neurone → effector: a muscle contracts or a gland secretes.

What information reaches the thermoregulatory centre?

Impulses from receptors in the centre itself, sensitive to the temperature of blood flowing through the brain (core temperature), and from temperature receptors in the skin.

Responses when core temperature is too high and too low

Too high: skin blood vessels dilate, so more energy is transferred from the skin; more sweat, which cools as it evaporates. Too low: skin blood vessels constrict, less energy transferred; muscles may shiver.

Insulin vs glucagon

Both from the pancreas. Insulin (glucose too high): glucose moves from the blood into cells and is stored as glycogen in the liver and muscles, or as lipid when full. Glucagon (glucose too low): glycogen changes back into glucose, which enters the blood.

Type 1 vs Type 2 diabetes

Type 1: the pancreas does not produce enough insulin; diet, exercise and insulin injections. Type 2: the body does not respond to its own insulin; obesity is a significant factor; diet, exercise and drugs.

Jobs of the liver in removing waste and poisons

Excess amino acids are deaminated to form ammonia, which is converted into urea; poisons are detoxified; old red blood cells are broken down and the iron is stored.

How does a healthy kidney make urine?

Blood is filtered (water, glucose, ions, urea; not cells or large proteins); all the glucose, the needed ions and as much water as needed are reabsorbed; urea, excess ions and excess water are released as urine.

ADH and negative feedback when blood water content is too low

The pituitary gland releases more ADH; the kidneys reabsorb more water; a small volume of concentrated urine is made; blood water content rises, so less ADH is released.

Three ways white blood cells defend the body

Phagocytosis (ingesting pathogens); producing antibodies that destroy particular bacteria or viruses; producing antitoxins that counteract toxins.

How does vaccination give immunity, and what is herd immunity?

Dead or inactive pathogen is injected; white blood cells make specific antibodies; if the real pathogen arrives, the correct antibody is made rapidly. If a large proportion of people are immune, spread is very much reduced.

How does an antibiotic-resistant strain such as MRSA spread?

A mutation produces a resistant strain; the antibiotic kills non-resistant bacteria; resistant ones survive and reproduce; the strain spreads rapidly because people are not immune and there is no effective treatment. Overuse speeds this up.

Innate behaviour, imprinting, habituation, classical and operant conditioning

Innate: inborn. Imprinting: early attachment to the first moving object seen. Habituation: learning to ignore a repeated harmless stimulus. Classical: linking a neutral stimulus with a natural one. Operant: trial and error with reward or punishment.