Physiology 2 Flashcards
What does the hypothalamus release?
Neurohormones. Because its brain tissue releasing a chemical into the blood to work on a distal site.
What is the role of the hypothalamus?
It is the integration centre for the endocrine system. It holds nerves which project down into the posterior pituitary.
How is the posterior pituitary connected to the hypothalamus?
Via the infundibulum.
It is a continuation of the nerves from the hypothalamus. It contains nerve terminals and axons.
How is the anterior pituitary connected to the hypothalamus?
Via the capillary portal system.
It wraps itself round the posterior pituitary.
IT is connected via neurohormones.
What are the differences between the anterior and posterior pituitary?
Anterior is epithelial in origin, posterior is nervous tissue in origin.
Anterior isn’t directly attached to the hypothalamus and the posterior is.
Anterior produces its own hormones and posterior doesn’t.
Where is the pituitary gland located?
In the hypophyseal fossa of the sphenoid bone. Below the hypothalamus and optic chiasm.
what is the tiny middle lobe of the pituitary called?
The pars intermedia. It secreted melanocyte releasing hormone.
What are tropic hormones?
These control the release of another hormone.
What are non-tropic hormones?
These don’t control the release of another hormone. They directly stimulate a target cell.
What are the non-tropic neurohormones released via the posterior pituitary?
Vasopressin - maintains water balance.
Oxytocin - stimulates uterine contraction and parturition, aids expression of milk in the lactating breast.
What do the hypothalamic tropic hormones do?
They stimulate or inhibit the release of hormones from the anterior pituitary.
How many hypothalamic releasing hormones?
5
How many hypothalamic inhibiting hormones?
2
How many hormones are released from the anterior pituitary?
6 - 5 of these are tropic hormones.
They are all peptides.
What is a trophic hormone?
These have an effect on growth, either directly or indirectly.
What controls negative feedback for the anterior pituitary?
Usually in response to the hormone.
The hypothalamus, anterior pituitary and target endocrine cell. This is long-loop feedback and short-loop feedback.
How is the parathyroid feedback different?
its not in response to the hormone, it is in response to the physiological response (the raised calcium levels in plasma).
what is hypo secretion?
when too little hormone is secreted.
What is hyper secretion?
When too much hormone is secreted.
What are endocrine disorders caused by?
Primary, secondary or tertiary disorders.
What are primary disorders?
a defect in the cells that secrete the hormone (end organ) - common.
What are secondary disorders?
when there is too much or too little tropic hormone in the pituitary - fairly common.
What are tertiary disorders?
When there is hypothalamic defects, ie - not enough releasing hormone secreted - Rare.
What is hypo responsiveness?
Not enough response from the body to the hormone. Receptors might be under expressed, antagonistic effects from other hormones. Disordered post-receptor failure.
What is hyper responsiveness?
Too much response. Could be due to permissive effect (one hormone enhancing the activity of another).
What is a permissive effect?
When one hormone alters the activity of another.
For example, thyroid hormone increases adrenaline mediated lipolysis.
Why is thyroid hormone needed?
For growth hormone to act normally.
What happens with too little growth hormone?
As long as the individual has enough thyroid hormone, they will be small but well proportioned.
What happens with too little thyroid hormone?
The individual will be small and disproportionate. Thyroid hormone is needed in order for growth hormone to act normally (without it bones don’t elongate properly).
What can cause hyper-responsiveness?
Prolonged exposure to low concentrations of hormone in the plasma. = increase in receptors.
What causes hypo-responsiveness?
Prolonged exposure to high concentrations of plasma hormone. = down regulation in receptor expression.
What is an example of an antagonistic response?
Growth hormone impairs glucose uptake in response to insulin in muscle and adipose tissue - by decreasing insulin receptors on them. This allows more glucose to go to other parts of the body to grow.
What are the hypothalamus posterior pituitary hormones?
Vasopressin (ADH) and oxytocin.
What are the hypothalamus hormones acting on the anterior pituitary?
5 releasing: Growth hormone releasing hormone Prolactin releasing hormone thyrotropin releasing hormone Gonadotropin releasing hormone corticotropin releasing hormone
2 inhibitory:
Growth hormone inhibitory hormone
dopamine (prolactin inhibitory hormone)
What are the anterior pituitary hormones?
5 tropic: Growth hormone Luteinising hormone Follicle stimulating hormone thyroid stimulating hormone adrenocorticotropic hormone
1 non-tropic:
prolactin
