Endocrine System Flashcards
Where and what do endocrine glands secrete ?
Hormones are secreted directly into the bloodstream
What is an endocrine gland ?
Ductless glands with a rich blood supply
Endo - internal, Crine - secretions
Name the 8 endocrine glands
Pineal gland
Pituitary gland
Parathyroid gland
Thyroid gland
Adrenal gland
Pancreas
Ovary
Testis
What are some functions of endocrine glands ?
Cellular metabolism
Growth and development
Sexual development
Homeostasis
Behaviour - mood/sleep
What is an exocrine gland ?
May or may not have excretory ducts
Where do exocrine glands secrete ?
Externally onto an epithelial surface
Tongue - saliva
Skin - sebum/sweat
GI tract - digestive enzymes
Name the 3 classes of hormones
Proteins/ peptides
Steroids
Amino acid derivatives
Describe the half life of proteins
They have a short half life of a few minutes, as they are not attached to a carrier protein.
Describe how proteins work ?
Note : usually water soluble, readily transported in blood
- Bind to plasma membrane receptors on target cells
- Signal transduction
- Initiate cellular changes (i.e. gene expression)
What are steroids synthesised from ?
Cholesterol
Name some examples of steroids
Testosterone
Oestrogen
Cortisol
Describe the half life of steroids
They have a longer half life than proteins, as they require specific transporter proteins in the blood.
Describe how steroids work ?
They readily diffuse across the plasma membrane
Bind to intracellular receptors/transcription factors - modify gene expression.
What are amino acid derivatives modified from ?
Tyrosine
Where are catecholamines synthesised in ?
Renal medulla
What are catecholamines ?
Neurotransmitters
Name some catecholamines
Adrenaline
Noradrenaline
Dopamine
Name some thyroid hormones
Thyroxine
Tri-iodothyronine
How do all hormones act ?
By binding to receptors
e.g. cell membrane receptors - peptides, glycoproteins and catecholamines
e.g. intracellular receptors - steroids and thyroid hormones
Episodic hormones
Released in response to physiological demand
e.g. insulin
Jagged lines
Diurnal hormones
Released in a predictable pattern over 24 hours
e.g. cortisol
Has a peak in the graph
- May also respond to episodic stimuli
Constant hormones
Fairly constant blood concentrations for normal physiological function.
e.g. thyroxine
Name the 3 types of stimuli that trigger endocrine glands to produce and release their hormones
Humoral
Neuronal
Hormonal
What is humoral stimuli ?
Circulating molecules in the blood.
SIMPLEST
i.e. critical ions or nutrients
What is neuronal stimuli ?
Stress responses
Sympathetic nervous system
e.g. Adrenaline
What is hormonal stimuli ?
In response to hormones produced by other endocrine glands
e.g. pituitary or hypothalamus
Describe the relationship between the hypothalamus and pituitary gland in the control of the endocrine system.
Hypothalamus and pituitary gland coordinate the endocrine system - orchestrate activity of other endocrine glands
Provides signal amplification - cascades and fine control
Hypothalamus secretes hormones which control release of pituitary hormones
Pituitary hormones stimulate/control many other endocrine glands
Negative feedback system
Function of the hypothalamus
Controls release of hormones from the anterior lobe of the pituitary gland
What types of hormones are released from the hypothalamus ?
Releasing hormones (GHRH)
Inhibitory hormones (GHIH)
What does the posterior pituitary do ?
Storage of hormones secreted by neurosecretory cells in the hypothalamus
Transported via neuronal axons to the posterior lobe
- ADH or Vasopressin
- Oxytocin