#127 Summary of Homeostasis and Co-ordination

 1 Animals and plants have internal communication systems that allow information to pass between different parts of their bodies, and so help them to respond to changes in their external and internal environments.

 2 Mammals keep their internal environment relatively constant, so providing steady and appropriate conditions within which cells can carry out their activities. This is known as homeostasis.

#126 Plant hormones - Gibberellin

Gibberellins are plant growth regulators that are synthesized in most parts of plants (mainly in young leaves and seeds and in stems). They have a role in seed germination and controlling stem elongation.

#125 Plant hormones - Auxin

Chemical communication in plants

Plant hormones or plant growth regulators are:
- produced in a variety of tissues
- move from cell to cell (by diffusion or active transport) or carried in xylem sap and phloem sap

The two types we're going to look at auxin and gibberellin.

#124 Venus fly trap

The Venus fly trap is a carnivorous plant that obtains a supply of nigtrogen compounds by trapping and digesting small animals, mostly insects.

#123 Birth control

‘Birth control’ means taking control over if and when a couple have a child. It may involve:
- contraception to prevent fertilisation
- use of hormones to prevent pregnancies

#122 Hormonal communication

Hormones like adrenaline, insulin, glucagion and ADH

- cell-signalling molecules
- made in endocrine glands; glands are groups of cells that secrete (produce and release) one or more substances
- passed directly into the blood

#121 Striated muscles

Striated muscles are muscles attached to the skeleton. They are neurogenic - they contract when stimulated to do so by impluses that arrive via motor neurones.

#120 Synapses

Synapse

- point where 2 neurones meet but do not touch
- contains the end of presynaptic neurone + synaptic cleft + end of postsynaptic neurone

#119 Action potentials

Action potentials are rapid changes in potential difference across the membrane.

#118 Control and co-ordination in mammals, the nervous system

Humans, like all living organisms, can respond to changes in the environment and so increase survival. Humans have 2 control systems to do this: the nervous system and the endocrine (hormonal) system. The human nervous system controls everything from breathing and standing upright, to memory and intelligence. It has 3 parts: detecting stimuli, coordinating and effecting a response.

#117 Control and co-ordination Syllabus 2016-2018

15.1  Control and co-ordination in mammals
15.2  Control and co-ordination in plants