- Created by: Emmatjies
- Created on: 11-01-20 12:53
Purpose of hormone
Hormones are chemical messengers that influence target cells or tissues.
Their release is dependant on the effects produced by the tissue.
- Pituatary gland
- Pineal gland
- Adrenal gland
- Thyroid gland
- Parathyroid gland
Methods of control enabling the release of hormone
- Positive feedback:
Stimulus increase hormone which increases effect, which triggers the stimulus.
- Negative Feedback:
Stimulus increase hormone, which increase effect, which decreases hormone which decreases effect.
- Hormonal stimuli- Rrelease of a hormone in response to another hormone
- Humoral stimuli - Control of hormone release in response to changes in extracellular fluids such as blood or the ion concentration in the blood.
- Neural stimuli - Stimulation of endocrine glands by the nervous system
Homeostasis is the ability to maintain a state of balance.
Negative feedback is an example of homeostasis. Very subtle changes that happen rapidly and constantly.
An example would be the Ca 2+ bone matrix.
- Low calcium blood plasma,
- Parathyroid recognises this and liberates PTH (parathyroid hormone) into the plasma
- PTH liberates Calcium from bone
- Plasma calcium is now raised.
The pituitary gland is located in the brain below the hypothalumus and releases:
ACTH, TSH, GH, PRL, FSH, LH, MSH, Oxytocin, ADH.
The anterior pituitary releases hormones produced in the hypothalumus.
The posterior pituitary releases hormones, stimulated by direct neural stimulation from the hypothalumus.
Have control over the endocrine glands, apart from adrenal glands.
Imaging used is CT, MRI
not plain film or ultrasound due to superimposition of structures.
Situated ontop of the kidneys
2 parts to the adrenal glands the medulla and cortex.
the cortex secretes cortisol stimulated by ACTH
the medulla secretes adrenaline which is stimulated by the automatic nervous system.
Imaging used is MRI, CT, US
Surrounding the superior part of the trachea
Thyroid hormones T3 and T4 regulate the rate of metabolism.
It is stimulaated by TSH from the anterior pituitary.
Calcitonin regulates the rate of calcium used by bone. Stimulated by an increase in plasma calcium.
Imaging- US , RNI, MRI, CT
Located on the posterior part of the thyroid.
Releases PTH, which is responsible for calcium homeostasis.
Stimulated by calcium blood plasma.
Pancreatic duct runs through the centre of the pancreas, which is a retroperitoneal organ.
Insulin which is stimulated by an increase in blood sugar, brings about the storage of glucose.
Glucagon is stimulated by a decrease in blood sugar and counteracts the effects of insulin.
Imaging used is plain film MRI, and RNI