Endocrine System Flashcards
The Endocrine System
Much slower than the nervous system Actions are mediated by hormones Regulates the following systems: - regulation of cellular metabolism - Maintenance of homeostasis - sexual development - growth and development from childhood to adult - modulates long term behaviour (mood and sleep)
What are endocrine glands
they have no ducts\they secrete and release hormones directly into the blood
What are hormones
chemical messengers that act on target cells through specific receptors
What are the three classes of hormones
Proteins - chains of amino acids (usually injected)
Steroids - synthesised from cholesterol (oral administration)
Amino acid derivatives - thyroid hormones + catecholamines (adrenaline, dopamine, noradrenaline)
Where do glands develop from
epithelial cells
Where do cords of cells develop and grow
down into the underlying tissue
what carry secretions to the surface of the epithelium
epithelial cells form ducts
Ductless endocrine glands
The hormone being delivered diffuses from the extracellular fluid into the bloodstream
Paracrine secretion
contain paracrine factors (polypeptides) diffused over short distances
Cell to cell communication - inducing changes in adjacent cells (peptide neurotransmitters)
Where is paracrine secretion important
In embryogenesis where gradients of polypeptides influence developmental change
Where is the pineal gland
in the brain
Tell me about the concentration of hormones in the blood
these often act at very low concentrations, these however vary:
- episodic
- diurnal
this is important when taking bloods as conc may vary throughout the day
How are steroids and thyroid hormones transported
specific carrier/binding proteins:
- improves solubility
- increases half life
- provides a reserve in the blood
What kinds of hormones are biological active
free hormones, once bound they are rendered inactive
Name the types of cell membrane receptors
peptides
glycoproteins
catecholamines
Name intracellular receptors in the nucleus
steroids
thyroid hormones
Anterior Pituitary develops from where
the epithelium of the mouth
The posterior pituitary
down growth of the hypothalamus which consists of nerve fibres
Endocrine Axes/Cascades
the target tissue of the one hormone is another endocrine gland:
THIS ALLOWS AMPLIFICATION AND FINE CONTROL
Hypothalamus
secretes hormones that control the secretion and release of pituitary hormones
Pituitary hormones
stimulate/control many other endocrine glands (thyroid, gonads etc.)
What are the two main functions of the hypothalamus
- Control release of anterior pituitary hormones via RELEASING HORMONES
- it secretes hormones that are stored and released by the posterior lobe of the pituitary gland:
- oxytocin
- antidiuretic hormone (ADH)
What is the name of the anterior lobe of the pituitary gland
Adenohypophysis
What are the 6 hormones the Adenohypophysis secretes
- Growth hormone (GH)
- Thyroid stimulating
hormone (TSH) - Adrenocorticotropic hormones (ACTH)
- Follicle stimulating hormone (FSH)
- Luteinising hormone (LH)
- Prolactin
What is the name of the posterior lobe of the pituitary gland and what’s it composed of
Neurohypophysis
neural tissue
What is the function of the neurohypophysis
stores hormones which are secreted by neurosecretory cells in the hypothalamus
Transported via neuronal axons in the stalk of the posterior lobe of the pituitary
What are the two hormones released from the neurohypophysis
ADH (antidiuretic hormone)
Oxytocin
What controls the pituitary
hypothalamus
Explain the action of negative feedback control
the final product of a cascade sets to inhibit a hormones higher up the cascade. The hypothalamus is an important site of negative feedback in many hormone systems.
optic chasm
immediately inferior to the hypothalamus and superior to the pituitary gland
Where is the thyroid gland
anterior to the trachea
Development of the thyroid gland
develops as down growth of the epithelium of the tongue (leaves a pit at the back known as the foramen caecum)
What is situated immediately inferior to the foramen caecum
thyroglossal duct
What do follicular cells secrete in the thyroid gland and where are they stored
Tri-iodothyronine (T3) and Thyroxine (T4)
stored in colloid (thyroglobulin)
What does thyroxin regulate
energy use - rate of metabolism
protein production - growth and development
regulates sensitivity of cells to other hormones
What types of cells produce calcitonin (regulates calcium homeostasis)
parafollicular (aka c) cells
Where do parathyroid glands develop from
the wall of the pharynx in two pairs of glands
Where are the parathyroid glands located
embedded in the posterior aspect of the thyroid
What hormone does the parathyroid glands produce
parathyroid hormone - this regulates calcium homeostasis - stimulates osteoclasts to breakdown bone matrix and therefore increases blood calcium levels
What are the three layers of epithelial cells in the cortex
zona glomerulosa
zona fasciculata
zone reticular
What cells are in the medulla
neural crest cells
What produces steroid hormones
the Adrenal cortex
Where does the adrenal cortex develop from
mesoderm of the posterior abdominal wall
Whats secreted by the zone glomerulosa
mineralocorticoids e.g. aldosterone
whats secreted by the zone fasciculata
glucocorticoids e.g. cortisol
What is secreted by the zone reticularis
sex steroids - androgens
Where does the adrenal medulla develop from
forms from neural crest cells neuroectoderm
What cells does the Adrenal medulla contain
Chromaffin which produce catecholamines -epinephrine -norepinephrine -dopamine DIRECT CONNECTION WITH SNS
Where do pancreas ducts empty into
duodenum
What is the exocrine component of the pancreas
pancreatic acini produce pancreatic amylase (pancreatitis)
What is the endocrine component of the pancreas
Islets of Langerhans produce hormones (diabetes mellitus)
- alpha cells = glucagon
- beta cells = insulin
What hormone does the GI tract produce
Gastrin
