W10 - Homeostasis & The Endocrine System Flashcards
What are the main functions of the endocrine system
Mairegulation of : sodium & water (blood volume), calcium & phosphate, energy balance & control of macronutrients, response to stress and reproduction
What are the 2 types of hormones
Non - steroidal (insoluble)
Steroidal hormones (soluble)
What do non - steroidal hormones do
Attach to specific membrane receptors and work by a secondary messenger mechanism
What do steroidal hormones do
Pass through the cell membrane of the target organ
Name 2 types of non steroidal hormones and say what they do
Proteins
- synthesised by pre pro hormones (undergo transformation at a certain time)
- stored in secretory glands & are exocytose from cells
- e.g. insulin, glucagon, adrenocorticotropic hormone (ACTH)
Amino acids
- synthesised by other amino acids
- e.g. adrenaline, noradrenaline and dopamine
Name and example of a steroidal hormones
Oestrogen, testosterone and progesterone
What is the paracrine pathway
Hormones produced in cells, secreted & act directly on nearby receptive cells
What is the autocrine pathway
Cell is able to produce its own hormone and exert effect on itself, receptor cells are also secretory cells
What is the endocrine (telecrine) pathway
Hormones produced in a cell, secreted & travel via the blood to distant cells, bind to receptors and act upon that cell
What is the synaptic pathways
Hormones produced in the neuron, secreted and travel down the axon to synapse, released and taken up by nearby neuron with the appropriate receptors to exert an effect
What is the neuroendocrine pathway
Hormones produced in neuron, secreted, travel down axon to the synapse, released, taken up by vascular system, travel to distant cells with receptors to exert an effect
What does the hypothalamus do
Contains neurons that synthesise inhibiting and releasing hormones to act in the pituitary gland
E.g.
GHRH (growth hormone)
THR (Thyrotropin)
CRH (corticotropin)
GnRH (gonadotropin)
What is negative feedback of hormone secretion regulation
Most common
Affected by environment & body temp, stress, nutrition and presence of specific body substances
E.g. thyroid hormone or insulin
What is positive feedback in regulating hormone secretion
Amplifies change instead of reversing them
Presence of hormones increases production of the hormone until there is interruption in the cycle
E.g. oxytocin in childbirth
Describe the thyroid
Butterfly shape
Stimulates metabolism
Helps break down carbs, proteins, fats for energy, stimulate heat & glucose production
Produces structural proteins, enzymes & hormones
Promotes growth & development in children
Name 4 thyroid hormones
TRH - thyrotropin releasing hormone
TSH thyrotropin stimulating hormone
Thyroxine T4 tetraiodothyronine
T3 (triiodothyronine)
What happens if thyroid hormone is released
Increase glucose absorption
Release lipids from adipose tissue
Metabolism of proteins from muscle tissue
Increase cholesterol breakdown in the liver
Increase oxygen consumption
Increase body heat production
Increase cardiac output
Increase gastric motility
Increase muscle tone & reactivity
Increase activity of cognitive processes
Name 2 thyroid disorders
Hyperthyroidism
- Hugh stimulation of the gland
- increase production of TSH by pituitary tumour
- treatment: medication containing high levels of iodine or health food supplements containing seaweed
Hypothyroidism
- during foetal development
- lack of thyroid development
- caused impaired growth & developmental delays
- detected in neonatal screening
What Graves’ disease
Autoimmune diseases: excessive stimulation of the thyroid gland
7-10x more common in women
IgG antibodies bind to TSH receptors & stimulate XS thyroid secretions
What acquired hypothyroidism
Autoimmune
Iodine deficiency
Treatment : Surgical removal or radial therapy to thyroid gland or medication to destroy the gland & genetic defects
What is homeostasis
Existence of a stable internal environment
What elements are in homeostasis
Stimulus
Receptor
Input
Output
Response
What negative feedback for homeostasis
Primary mechanic
Maintains a normal range than a fixed value
E.g temperature control, PH, blood sugar
What positive feedback in homeostasis
Found where there’s a dangerous or stressful process must be completed
E.g labour
What are the 2 homeostatic regulation mechanisms
Auto regulation (intrinsic)
- cells, tissues and organs
Extrinsic
- nervous system & endocrine system
