Wednesday 8 April 2009

iGCSE Biology - Chemical Coordination

  • A gland is an organ that secretes a substance.
  • Exocrine glands secrete their product through a duct.
  • Endocrine glands secrete their product directly into a bloodstream.
  • Differences between nervous and endocrine control:

Nervous System

Endocrine System

  • Works by nerve impulses transmitted through nerve cells (although chemicals are used at synapses)
  • Works by hormones transmitted in the bloodstream
  • Nerve impulses travel fast and usually have an instantaneous effect
  • Hormones travel more slowly and take longer to act
  • Response is usually short-lived
  • Response is usually longer-lasting
  • Impulses act on individual cells such as muscle fibres, so have a very localised effect.
  • Hormones can have widespread effects on different organs

 

  • Main endocrine glands:

Gland

Hormone

Some functions

Pituitary

Follicle stimulating hormone (FSH)

Stimulates egg development and oestrogen secretion in females and sperm production in males

Luteinising hormone (LH)

Stimulates egg release in females testosterone production in males

Anti-diuretic hormone (ADH)

Controls the water content of the blood

Growth hormone (GH)

Speeds up the rate f growth and development in children.

Thyroid

Thyroxin

Controls the body’s metabolic rate

Pancreas

Insulin

Lowers blood glucose

Glucagon

Raises blood glucose

Adrenals

Adrenaline

Prepares body for physical activity

Testes

Testosterone

Controls development of male secondary sexual characteristics

Ovaries

Oestrogen

Controls development of female secondary sexual characteristics; regulates menstrual cycle

Progesterone

Controls menstrual cycle

 

  • Adrenaline produces a number of changes in the body:

                     Breathing rate increases and breaths become deeper.

                     The heart beats faster.

                     Blood is diverted from intestine to muscles.

                     Glycogen is turned into glucose and released into the blood in     the liver.

                     The pupils dilate.

                     Body hair stands on end.

                     Mental awareness is increased.

  • Insulin causes glucose to be converted into glycogen in the liver.
  • Glucagon causes glycogen to be converted into glucose in the liver.
  • Diabetes is where a person cannot produce enough insulin.

5 comments:

  1. nice i have a biology igcse monthly exam tomorow and i think this will be usefull

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  2. Hey... This is some really helpful stuff.. Thanks.. But I can't help but notice that there is nothing on plants on there. For example; factors that affect photosynthesis?

    Thanks.. :)

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  3. This is v.helpful since it can help, cadidates to get ready 4 their...

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