Nerves and hormones Flashcards
The nervous system allows humans to do what?
React to their surroundings and coordinate their behaviour.
What is a stimulus?
A change in the environment.
What type of cells detect stimuli?
Receptor cells.
Give some examples of receptors and the stimuli they detect?
1) Receptors in the eyes that are sensitive to light.
2) Receptors in the ears that are sensitive to sound. 3)Receptors in the ears that are sensitive to changes in position and enable us to keep our balance. 4)Receptors on the tongue and in the nose that are sensitive to chemicals and enable us to taste and to smell.
5) Receptors in the skin that are sensitive to touch, pressure, pain and to temperature changes.
Structure of a human light receptor cell?
Like most cells in the body it has a nucleus cytoplasm and a cell membrane.
Describe how a simple reflex action occurs.
Impulses from a receptor pass along a sensory neurone to the central nervous system. Then at a junction (synapse) between a sensory neurone and a relay neurone in the central nervous system, a chemical is released that causes an impulse to be sent along a relay neurone. Next a chemical is then released at the synapse between a relay neurone and motor neurone in the central nervous system, causing impulses to be sent along a motor neurone to the organ (the effector) that brings about the response. Finally the effector is either a muscle or a gland, a muscle responds by contracting and a gland responds by releasing (secreting) chemical substances.
Examples of internal conditions that are controlled.
1) The water content of the body – water leaves
the body via the lungs when we breathe out and via the skin when we sweat to cool us down, and excess water is lost via the kidneys in the urine.
2) The ion content of the body – ions are lost via the skin when we sweat and excess ions are lost via the kidneys in the urine.
3) Temperature – to maintain the temperature at which enzymes work best
4) Blood sugar levels – to provide the cells with a constant supply of energy.
What is a hormone?
A chemical substance that is secreted from a gland and can change a bodily function. Hormones travel through the bloodstream.
Several hormones are involved in the woman’s menstrual cycle. What are they?
FSH
LH
Oestrogen
What does FSH control?
FSH causes ova to mature in the ovaries and stimulates oestrogen to be produced.
What does LH control?
The release of a mature ovum.
What does oestrogen do?
Inhibits further production of FSH.
Uses of hormones in fertility?
Oral contraceptives to reduce the production of FSH.
FSH and LH being given to stimulate the production of ova for IVF.
Plants are sensitive to which 3 factors?
Light
Moisture
Gravity
Auxin controls which plant tropisms?
Geotropism and phototropism.
