homeostasis and endocrine Flashcards
what is negative feedback
- prevents sudden changes
- reduc es action to the ffectors
- correct the set point
- negates change
- limits chaos in the body and creates stability
- this is the most commmon type of feedback loop
- such a body temp, blood pressure
what is positive feedback
- this increases the action to the body
- produces more instability
- there are only a few types for survival such as childbirth, blood clotting
- ## these mechanisms are short lived
what are the major endocrine glands
hypothalamus
- pineal gland
- pituitary gland
- thyroid gland
- parathryroid glands
- adrenal glands
- pancreas
- kidney
- ovaries
what organs contain endocrine cells but are not major organs of the endocrine system
- thymus
- heart
- liver
- stomach
- kidney
- small intestine
what are the types of hormones
- amino acid based - most common eg. amine = adrenaline and noradrenaline, thyroxine peptide - insulin and protein hormone s
- steroid - gonadal and adrenocortical hormones - synthiszed by cholesterol
- eicosanoids - leukotrienes and prostaglandins - these are deprived from arachadonic acid
what are autocrines and paracrine s
anutocrine s- chemicals that exert their effects on the same cells that secrete them
paracrines - locally acting chemicals that affect cells other than the ones that secreted them
what is target cell activation
- hormones only target specific cells dye to their specific receptors which the hormones bind to
- these receptors may be intraccelular or on the plasma membrane
- the activ action of these target cells depend on
- blood levels of the horome
- relative number of receptors on the target cell
- the affinity of those receptors for the hormone
there is up regulation - this is when the cells form more receptors in response to the hormone . this is an enhanced response
or down regulation - the target cells loose receptors in response to the horome and this is decreased response
what are the different horomone mechanism
- alter plasma membrane ermability
- stimulate protein synthesis
- activate or deactivate enzyme systems
- induce cellular secretory activity
- stimulate mitosis
what are the 3 diffrent stimuli for hormonal release
- humoral stimuli - secretion of hormones in direct response to changes in blood levels of ions and nutrients
- neural stimuli - nerve fibres stimulate hormone release
- hormaonal stimuli - release of hormones in response to hormones produced by other endocrine organs
what is the structure and function of the pituatriy glands
- two lobed - NEUROHYPOPHYSIS and ADENOHYPOPHYSIS
neurohypophysis
- posterior lobe, it has neural connections to the hypothalamus
- the nuclei of the hypothalamus synthesises ADH and OXYTOCIN which are transported to the neurohypophysis for release
ADENOHYPOPHYSIS
- anterior lobe
- it has no direct connection to the hypothalamus
- it produces 6 hormones, GH, TSH, ACTH, FSH, LH, PRL
- these regulate the activity of the endocrine glands
how do steroid and thyroid hormones wor
- they diffuse evil into the plasma membrane of the cells
- they activate the specific intracellular receptors
- the hormone receptor complex travels to the nucleus and binds a dna associated receptor protein.
- this prompts dna transcription to produce mrna
- the mrna is translated into proteins which bring a cellular affect
what is the thyroid glan d responsible for
- it secretes 3 horomones
1. calcitonin - for calcium homeostatsis
2. T3 ( triiodothyronine)
3. T4 thyroxine
what is the structure and function of the adrenal glands
- it is made up of the adrenal cortex and adrenal medulla
- the medulla secretes ADRENALINE
- the adrenal cortext produces adrenocortioids such as
- mineralocortoids ( mainly aldosterone which acts on the kidney to increase the Na+ reabsorption, electrolyte homeostasis, increase blood volume and pressure and regulate renin-angiotensin system)
- glucocorticoids (mainly cortisol which regulates the bodies response to stress and metabolism) - the secretion of this is controlled by the hormone ACTH from the anterior pituitary gland
- sex hormones (androgens)
