Flashcards in B1 Topic 2 - Responding To Change Deck (15)
Homeostasis involves maintaining a stable internal environment.
Regulation of water levels in the blood.
Describe what happens in the body when the blood glucose level changes from the normal level.
Increase in glucose (e.g. from a meal) detected by pancreas > Insulin secreted from pancreas > Glucose turned into glycogen by liver > Blood glucose decreases backs to normal level.
Decrease in glucose (e.g. used for exercise) detected by pancreas > Glucagon released into blood > Glycogen turned into glucose by liver > Blood glucose increases back to normal level.
Describe what happens in the body when the internal temperature changes from the normal level.
Increase in temperature (e.g. from exercise) detected by hypothalamus in brain > Hairs lay flat > Sweat released from skin > Vasodilation in capillaries near skin > Sebaceous gland releases sebum or oil to moisturise the skin > Body temperature decreases backs to normal level.
Decrease in temperature (e.g. cold environment) detected by hypothalamus > Hairs stand on end > Vasoconstriction in capillaries near skin > Sweat production decreases or stops entirely > Body temperature increases back to normal level.
What mechanism is used to maintain a stable internal environment?
What are hormones and what do they do?
Hormones are chemical messengers which are sent into the blood. They are released from endocrine glands and travel all over the body, but they only affect the target cells which have the right receptors to respond to that particular hormone. Hormones tend to have long-lasting effects.
What are neurones and what do they do?
Neurones, or nerve cells, transmit electrical impulses around the body to transmit information. They are made up of a nucleus surrounded by branched dendrons, followed by an axon surrounded in myelin sheath which leads to branched synapses. The electrical impulses is sent down the axon of the cell. The myelin sheath acts as an insulator for the electrical impulses and also speed up the messages. Neurones are long so that the impulses travel faster, though at the end of each neurone there is a synapse which changes the electrical impulse into a chemical. They travel across a vey small gap to the next neurone where the message continues.
Summarise the differences between hormones and nerves.
Act for a short time
Act for long time
Affect body in a more general way
What order do electrical impulses travel through the reflex arc?
Stimulus > Receptor > Sensory Neurone > Central Nervous System > Motor Neurone > Effector > Response
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A reflex is an automatic response to a stimulus that tends to reduce the chance of injury.
What causes Type 1 diabetes? How can it be treated?
Type 1 diabetes occurs when the pancreas stops producing insulin, this causes an increase in the blood glucose levels which can kill the person. Type 1 is usually genetic and starts affecting an individual during their teens.
It is treated by injecting insulin into the bloodstream before meals or by avoiding food containing a lot of carbohydrates.
What causes Type 2 diabetes? How can it be treated?
Type 2 diabetes occurs when the pancreas can't produce enough insulin or when the body cells become immune to the effects of insulin, either way, the blood glucose levels rise to dangerous levels. It is usually caused by obesity, when an individual has a BMI over 30
Type 2 diabetes can actually be cured if it is spotted early and the individual improves their diet and does regular excessive to lose weight. They can also take medication and insulin.
How does auxin control plant growth in the roots and shoots of a plant?
Shoot (positive phototropism):
Auxin moves away from light and causes cells on that side to elongate by absorbing water into their vacuoles. This causes the plant shoot to bend towards the light allowing the plant to absorb more light for photosynthesis.
Root (positive gravitropism):
Auxin moves to the bottom of the root, which inhibits growth in the root's cells. This cause the top half of the root to grow faster than the bottom half which makes them bend downwards so that they can absorb more water and nutrients.
What does gibberellin control in a plant?
Seed germination, stem growth and flowering.