The Endocrine System Flashcards
Define exocrine gland.
An exocrine gland secretes into the ducts and onto the surface or lumen. They act locally.
Examples are sweat glands gastric glands .
Define endocrine gland.
An endocrine gland has no duct and it secretes hormones into the bloodstream. Act at a distance.
What hormones play role in endocrine function of reproduction, metabolic rate, and growth.
Reproduction - oestrogen and testosterone.
Metabolic rate - thyroid
Growth - growth hormone
What hormones play role in the endocrine function of stress response, immune system, and blood pressure.
Stress response - adrenaline or cortisol
Immune system - cortisol
Blood pressure - Anti-diuretic hormone or aldosterone.
What hormones play role in the endocrine function of the digestive processes, blood glucose levels, blood calcium levels and the sodium/potassium balance.
Digestive processes - gastrin, CCK, secretin
Blood glucose levels - insulin and glucagon
Blood calcium levels - calcitonin and parathyroid hormone.
Sodium/potassium balance - Aldosterone
Compare the nervous and endocrine system and how they work closely together.
Nervous system - releases neurotransmitters at synapses.
Endocrine system - releases hormones into the bloodstream.
Compare the nervous system and endocrine system on how fast they respond.
Nervous system - fast responding (m sec), but short acting.
Endocrine system - slower response (sec, min, hour), but longer lasting.
Which neurons secrete hormones?
Neurohormones - hypothalamus, posterior pituitary, adrenal medulla.
Why do hormones only affect some cells when all cells are exposed to hormones in the blood?
Hormones, bind to specific receptors on specific target cells.
The number of receptors can increase or decrease .
What are the two groups of hormones?
- Water soluble (mostly proteins) -hypothalamic and pituitary hormones, GIT hormones, insulin, adrenaline, etc.
- Lipid soluble (steroids) - sex hormones: oestrogen, progesterone, and testosterone.
Cortisol, aldosterone and thyroid hormones.
What is the action of water soluble hormones?
- The hormone binds to the receptor (on cell membrane) which is the first messenger.
- ATP is converted to cAMP (second messenger)
- cAMP serves as a second messenger to activate certain enzymes.
- Activate activated enzymes catalyse reactions that produce physiological response.
- cAMP is inactivated.
What is the action of lipid soluble hormones?
- Lipid soluble hormone diffuses into the cell.
- Activated receptor (inside cell) hormone complex alters gene expression.
- Newly formed mRNA direct synthesis of specific proteins on ribosomes.
- New proteins alters cells activity.
What is the pituitary and how many parts does it made up of?
The pituitary produces many hormones which control other glands.
There are two parts of the pituitary:
1. The smaller posterior picture (30%)
2. The larger anterior pituitary (70%)
The pituitary is controlled by the hypothalamus .
What is the posterior pituitary made of?
The posterior pituitary is made of nervous tissues. It stores and releases two hormones (made in hypothalmus):
- Oxytocin.
- Antidiuretic hormone.
What’s the role of oxytocin?
It stimulates uterine contractions in labour and milk ejection in lactating mothers.
What is the role of ADH?
It acts on the kidneys to increase water reabsorption into the blood - decreases urine output.
What control is the posterior pituitary under?
It’s under nervous control.
The nerve impulses > hypothalamus > posterior pituitary = hormones being released into the blood
Explain the role of ADH.
- Stimulated by dehydration.
- Increased water reabsorption by kidneys.
- Decrease in sweat production.
- Constricts arterials if severe blood loss (increases blood pressure)
What role does alcohol play on ADH?
Alcohol inhibits ADH.
This results in large volume of urine excretion, resulting in dehydration.
What is the role of diabetes insipidus on ADH?
Results in a lack of ADH. Excreting large volumes of urine resulting in dehydration.
What control is the anterior pituitary under?
It’s under hormonal control by the hypothalamus. The hormones are carried from the hypothalamus via the blood vessels to specific target cells in the anterior pituitary.
What are the six anterior pituitary hormones?
- Growth hormone (GH) -for bones and muscles
- Prolactin (PRL) -mammary glands
- Follicle stimulating hormone (FSH)
- Luteinising hormone (LH)
- Thyrotropic hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
How is hormone secretion regulated?
It’s regulated by:
1. Signals from the nervous system.
2. Chemical changes in the blood.
3. Other hormones.
They all use negative feedback to prevent over and under secretion of hormones
What does the thyroid control?
Metabolic rate
