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What is a Hormone?

A hormone is a chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs


What hormone is produced by-
1. adrenal gland
2. pancreas
3. testes
4. ovaries

1. adrenaline- readies the body for fight-flight response
2. insulin
3. testosterones- develops male sexual characteristics in males
4. oestrogen- develops female sexual characteristics and controls menstrual cycle


What part of the blood carries hormones?

blood plasma


What are the effects of adrenaline?

- Increasing blood glucose concentration for increased respiration in muscle cells
- Increasing pulse rate and breathing rate so glucose and oxygen can be delivered to muscle cells, and carbon dioxide taken away, from muscles cells more quickly
-Diverting blood flow towards muscles- again to ensure the reactants of respiration are as available as possible
-Dilating pupils to allow as much light as possible to reach the retina so more information can be sent to the brain


What is the difference between endocrine and nervous system.

1. made up of glands
2. type of message- hormones
3. Speed- slow
4. Length of effect- slower

1. made up of nerves, spinal cord and brain
2. type of message- electric impulse
3. speed- fast
4. Length of effect- fast


Define Homeostasis

Homeostasis is defined as the maintenance of a constant internal environment


Most homeostatic mechanisms in the body are controlled by a process known as?

Negative feedback


How does negative feedback works?

-if the level of something rises, control systems are switched on to reduce it again
-if the level of something falls, control systems are switched on to raise it again

Negative feedback mechanisms are usually a continuous cycle of bringing levels down and then bringing them back up so that overall, they stay within a narrow range of what is considered ‘normal’


By the production of what two hormones is negative feedback of glucose levels controlled?

INSULIN - Insulin is produced when blood glucose rises and stimulates liver and muscle cells to convert excess glucose into glycogen to be stored
GLUCAGON- Glucagon is produced when blood glucose falls and stimulates liver and muscle cells to convert stored glycogen into glucose to be released into the blood


Brief type-1 diabetes

Type 1 diabetes is a condition where the blood glucose levels are not able to be regulated as the insulin-secreting cells in the pancreas are not able to produce insulin
means that blood glucose levels are often far too high


What are the symptoms of type-1 diabetes?

extreme thirst,
weakness or tiredness,
blurred vision,
weight loss
and loss of consciousness in extreme cases


Brief the treatment of type-1 diabetes

It can be treated by injecting insulin
The extra insulin causes the liver to convert glucose into glycogen, which reduces the blood glucose level


What is the process of temperature regulation ?

1. Regulation is controlled by the brain which contains receptors sensitive to the temperature of the blood
2. The skin also has temperature receptors and sends nervous impulses to the brain via sensory neurones
3. The brain responds to this information by sending nerve impulses to effectors in the skin to maintain the temperature within a narrow range of the optimum, 37°C


What is the function of fatty tissue inside the skin?

Fatty tissue under the dermis acts as a layer of insulation to prevent too much body heat being lost through the skin


What is the homeostatic response for increase in the body temperature?

1. thermoreceptors detects the change and skin detects the change
2. increased sweating, vasodilation and hairs lie flat on the skin
3. body temperature goes down


What is the homeostatic response for decrease in the body temperature?

1. thermoreceptors detects the change and skin detects the change
2. vasoconstriction, shivering, skin hairs erect
3. increase in body temperature



1. When we are hot, blood flow in capillaries increases because blood vessels to the skin capillaries get wider – this is known as vasodilation
2. This cools the body as blood (which carries heat around the body) is flowing at a faster rate through the skin’s surface and so more heat is lost by radiation



1. When we are cold blood flow in capillaries slows down because arterioles leading to the skin capillaries get narrower – this is known as vasoconstriction
2. This reduces the amount of heat lost from blood by radiation as less blood flows through the surface of the skin


Define gravitropism

a response in which parts of a plant grow towards or away from gravity


Define phototropism

a response in which parts of a plant grow towards or away from the direction from which light is coming


What is the positive and negative response for gravitropism?

positive- grows towards the gravity - ROOTS
negative- grows away from the gravity - SHOOTS


What is the positive and negative response for phototropism ?

positive- grows towards the direction of the light- SHOOTS
negative- grows away from direction of the light- ROOTS


How does a plant responds to stimuli ?

Plants respond to stimuli by producing a growth hormone called auxin which controls the direction of growth of roots or stems


Brief auxin

-Auxin stimulates the cells behind the tip to elongate (get larger); the more auxin there is, the faster they will elongate and grow
-Auxin is made in shoot tip only
-When light shines on the shoot predominantly from one side though, the auxin produced in the tip concentrates on the shaded side, making the cells on that side elongate and grow faster than the cells on the sunny side
-This unequal growth on either side of the shoot causes the shoot to bend and grow in the direction of the light


Brief the plant hormones in the weed killer.

Most weedkillers contain synthetic hormones like auxin – known as 2,4D
They are selective so they are sprayed onto an area such as a lawn or farm crops and the synthetic auxin affects the weeds but not the grass / crop plants
The weeds respond by growing very fast and then dying, leaving more space, nutrients and water for the grass or crop plants to grow