| Term | Definition |
| Homeostatis | Maintaining the body’s internal environment in a
steady state despite a wide range of
environmental conditions |
| Homeostatic Systems (2 points) | Nervous system
Endocrine system |
| Receptor (2 points) | Neuron that senses changes in the environment (stimulus)
Sends nerve impulses or chemical signals (inputs)
to control centre |
| Control centre (2 points) | -Sets range of values which must be maintained
-Evaluates inputs from receptors
– Generates output commands/responses
– Typically nerve impulses, hormones, chemical signals |
| Effector (2 points) | – Receives signal from control centre
– Produces response/effect that changes controlled
condition |
| Negative Feedback system | Reverses/counteracts a change caused by a
stimulus
Minimises/eliminates effects of stimulus
Reestablishing homoeostasis |
| Positive feedback systems | Strengthens/reinforces a change caused by a
stimulus |
| How does the endocrine system maintains homoeostasis | Regulates activity and growth of target cells in the
body
Hormones regulate metabolism |
| Hormones (5 points) | Chemical messenger molecules
Secreted into circulatory system
Communicate regulatory messages
Act on distant target cells
Present in blood, milk, urine |
| Classes of hormones(5 points) | 1) Peptide -Gonadotropin Releasing Hormone
2)Polypeptides (<100 peptides)- Adrenaline
3)Protein hormones (>100 peptides) - Prolactin
4)Amines (Derived from tyrosine and tryptophan) - Seratonin
5)Steroids(lipophillic) - Testosterone |
| Endocrine glands | Secrete directly into Extracellular fluid and travel via the blood
stream (internally) |
| Exocrine glands | Secrete into ducts that empty onto the surface of a
covering/lining
Eg. Mucus, sweat, oil, earwax, saliva, digestive enzymes |
| Ectocrine signalling | The hormone is secreted in to the environment e.g.
pheromones |
| GnRH | Gonadotropin- Hypothalamus- Stimulates FSH, LH release |
| GNRH | Growth Hormone Releaseing Hormone - Hypothalamus- Stimulates GH release |
| Oxytocin | Posterior pituitary- Stimulates utherine contraction, milk let down |
| Glucocorticoids | Adrenal Cortex- Essential for normal response to stress |
| Epinephrine /Norepinephrine | Adrenal Medulla-Augments sympathetic response to stress by actions on several organs |
| Melatonin | Pineal Gland - Regulates sleep |
| Testosterone | Testes - sperm production |
| Oestradiol, progesterone | Ovaries - Stimulates utherine lining |
