Endo Intro to endocronology Flashcards
What is homeostasis?
Maintenance of a steady state/internal
environment
What elements stimulate hypothalamus if there is a change in temperature?
-Cutaneous temperature receptors
-Hypothalamic temperature receptors
What is done to counter heat loss?
sweating,
vasodilatation
What is done to counter heat gain?
shivering,
vasoconstriction,
metabolism
What happens to the set point when the body has an infection?
With infection the set point
is changed and body
temperature rises
What are the benefits of an increase in body temperature during an infection?
– Inhibits bacterial growth
– Speeds up metabolic reactions
– Increases delivery of white blood cells to infection sites
What is the homeostatic control of blood pressure?
- Medulla signals to heart and peripheral resistance
- Baroreceptors(stretch receptors) signal the medulla tor control blood pressure with negative feedback.
What does hypertension do that causes an increase in blood pressure?
Resetting the
sensitivity of the
baroreceptors
What is the control of circulating cortisol concentrations?
- Hypothalamus secretes corticotropin releasing hormone which acts on the anterior pituitary gland.
- This leads to the secretion of ACTH that acts on the adrenal cortex resulting in the release of cortisol.
- Negative feedback acting on the hypothalamus control circulating cortisol concentrations
What are the effectors that are involved in circulating cortisol concentrations?
- Anterior pituitary gland
- Adrenal cortex
What increases set point in control of circulating cortisol concentrations?
- Stress
- Circadian rhythm
How does the positive feedback control system work in haemostasis?
- Break or tear in blood vessel wall
- Clotting occurs as platelets adhere to site and release chemicals
- Released chemicals attract more platelets
- Clotting proceeds until break is sealed by newly formed clot
How does the positive feedback system in the control of uterine contractions in labour work?
- In labour oxytocin
stimulates contraction
of uterine muscles - Cervix dilates and
activate stretch
receptors - Action potentials
signal to
hypothalamus - Stimulates further
release of oxytocin
What are major endocrine glands?
- Hypothalamus
- Pituitary gland
- Thyroid, adrenal cortex, gonads
- Pancreas
- Parathyroid glands
What does the hypothalamus secrete?
Releasing & inhibiting hormones
What does the anterior lobe of pituitary gland secrete?
Trophic hormones
What does the posterior lobe of the pituitary gland secrete?
oxytocin & vasopressin (ADH)
What does the thyroid gland secrete?
Thyroxine, tri-iodothyronine
What does cortex of the adrenal gland secrete?
Cortisol, aldosterone
What does the medulla secrete of the adrenal gland secrete?
Adrenaline/noradrenaline
What do the gonads secrete?
Oestrogens, androgens, progestagens
What does the pancreas secrete?
Insulin, glucagon
What do parathyroid glands secrete?
Parathyroid hormone
How do endocrine hormones work?
Hormones released by an endocrine cell into the general circulation and acting on distant target sites
How do paracrine hormones work?
Hormones released by an endocrine cell which at locally on adjacent cells
How do autocrine hormones work?
Hormones released by a cell which act back on the same cell
How do intracrine hormones work?
Conversion of an inactive hormone to an active hormone that acts within that cell
What are the general functions of hormones?
- Reproduction, growth and development
- Maintenance of internal environment
- Energy production, utilisation and storage
What are the different chemical classification of hormones?
- Protein/peptide hormones
- Steroid hormones (cholesterol)
- Amino acid derivatives(tyrosine/tryptophan)
- Fatty acid derivatives
What is the half life of protein/peptide hormones and how are they transported?
-Half life is minutes
-Transport is mainly unbound
What is the half life of tyrosine derivatives(catecholamines), thyroid hormones and how are they transported?
-Seconds(CA’s) hours(thyroid hormones)
-Transport of thyroid hormones is bound to plasma proteins
What is the half life of cholesterol derived hormones and how are they transported?
-Half life is hours-days
-Transport is bound to plasma proteins
Where are the magnocellular neurons and what do they synthesise and release?
Magnocellular neurons in
the hypothalamus
synthesise and release
posterior pituitary
hormones
Where do other neurosecretory cells in the hypothalamus release their hormones into?
release
their hormones into the
portal capillaries in which
they are transported directly
to endocrine cells of the
anterior pituitary gland
What are the glands controlled by the hypothalamic-pituitary axis?What are the hormones and what do they act on?
-Hypothalamus stimulate anterior pituitary gland with releasing/inhibiting neurohormones.
-Anterior pituitary gland releases trophic hormones TSH, ACTH and LH/FSH
-TSH acts on thyroid
-ACTH acts on adrenal cortex
-LH/FSH act on Gonads
What and where does a release of corticotropin releasing hormone(CRH) increase release of and from where?
-CRH released from hypothalamus
-Acts on anterior pituitary to increase release of ACTH
Where is TSH released from and what does it increase secretion of and from where?
-TRH released from hypothalamus
-Acts on anterior pituitary to increase release of TSH
Where is Growth hormone inhibiting hormone(GHIH) released from, what is it also known as and what does it decrease release of and from where?
-GHIH is released from hypothalamus
-Also known as somatostatin
-Acts on anterior pituitary to reduce release of TSH
Where is Gonadotropin releasing hormone(GnRH) released from and where does it act and what does it increase release of?
-GnRH is released from hypothalamus
-Acts on anterior pituitary to increase release of LH and FSH
Where is dopamine released from and where does it act and what does it decrease release of?
-Dopamine released from hypothalamus
-Acts on anterior pituitary to decrease release of prolactin
Where is growth hormone releasing hormone(GHRH) released from, where does it act and what does it increase release of?
-GHRH released from hypothalamus
-Acts on anterior pituitary to increase release of growth hormone
Where is growth hormone inhibiting hormone(GHIH) released from, where does it act and what does it decrease release of?
-GHIH released from hypothalamus
-Acts on anterior pituitary to decrease release of GH
What processes is cortisol involved in?
-Gluconeogenesis
-Protein mobilisation
-Fat mobilisation
-Anti-inflammatory effects
What does a lack of cortisol cause?
Addison’s disease
What does an excess of cortisol cause?
Cushing’s disease
What is addison’s disease?
Deficiency of adrenocortical hormones
What is cushing’s disease?
Excess glucocorticoids
What causes testicular feminization?
Complete resistance to
circulating androgens
What does vitamin D resistance cause?
Rickets
