What are hormones?
Hormones are the chemical messengers (proteins) that send signals from one part of the body to another
Where are hormones secreted into in humans?
What part of the brain produces many hormones?
The pituitary gland
How does human growth hormone stimulate growth?
It Increases uptake of amino acids into soft tissue and bone cells
Promotes synthesis of tissue proteins eg long bones during growing years
What happens as a result of under-production of human growth hormone during adolescence?
Reduction in overall growth = pituitary dwarfism
What happens as a result of over-production of human growth hormone during adolescence?
Increase in overall growth, especially long bones = gigantism
What happens as a result of over-production of human growth hormone during adulthood?
Enlargement of hand, foot and jaw bones = acromegaly
_____ is produced by the pituitary gland and controls the growth and activity of the thyroid gland?
TSH - thyroid stimulating hormone
TSH induces the formation of ________ in the thyroid gland which controls the body's metabolic rate and growth?
What happens as a result of over-production of TSH? (all ages)
Too much thyroxine produced = increased size and activity of thyroid gland and swollen neck and bulging eyes
What happens as a result of under-production of TSH as a child?
Too little thyroxine produced = decreased mental and skeletal development
What happens as a result of under-production of TSH as an adult?
Too little thyroxine produced = lethargy and increased weight
What is the most common type of auxin?
Indole acetic acid - IAA
What is IAA produced by?
The root and shoot tips and leaf meristems
What does IAA do?
Stimulates cell division in apical meristems and cambium
Promotes cell elongation in apical and lateral meristems
Is necessary for cell differentiation
What is the result of low levels of IAA in a plant?
Stimulates root growth
Does not effect shoot growth
What is the result of high levels of IAA in a plant?
Stimulates shoot growth
Inhibits root growth
What is the result of very high levels of IAA in a plant?
Inhibits shoot and root growth
What is phototropism?
The directional growth of a plant in response to light from one direction
A unidirectional light source causes an
equal / unequal
distribution of hormone in the tip
There is a higher concentration of auxin in the
illuminated / non-illuminated
When the shoot bends towards the light this is called...?
High levels of auxin produced by the apical buds prevent the growth of _____ buds?
Seperation of a leaf from a plant is called ...?
Give one commercial use of auxins
Produce seedless fruits
Delay abscission of fruits to prevent fruit dropping before they are ripe
Induce root growth in shoot cuttings - rooting powder
Selective herbicide on grass where it kills broad-leaved plants eg dandelion but not the grass
What is the most common gibberellin?
Gibberellic acid - GA
What do gibberellins do?
Stimulate cell division and elongation in stems
Break dormancy in buds and seeds
Cause an increase in length of internodes (the space between two sets of leaves)
Higher Biology - Unit Three - Hormonal Influences