Homeostasis And The Endocrine System Flashcards
What is homeostasis?
The existence of a stable environment
Name some conditions that must be controlled by the body
Body temperature
Water content
Carbon dioxide
Blood sugar
Blood pressure
What is homeostatic regulation?
The adjustment of physiological systems to preserve homeostasis
Name the 5 elements of a homeostatic control system
Stimulus
Receptor
Input
Output
Response
Which type of feedback is more common negative or positive?
Negative feedback
Name some negative feedback systems
Temperature control
PH
Blood sugar
Name some positive feedback systems
Haemostasis
Labour and delivery
What is the control centre for thermoregulation?
Hypothalamus
Name some heating mechanisms of the body
Shivering
Hairs on our body stand up
Response to get up and move
Name some cooling mechanisms in the body
Sweating
Redistribute the blood
What are the two main systems for homeostatic regulation?
Intrinsic and extrinsic
What is another name for intrinsic regulation?
Auto regulation
What is auto regulation?
It is when cells, tissues and organs adjust automatically to environmental changes
What is extrinsic regulation?
It results in either your nervous system making changes or your endocrine system
What can cause homeostasis to go wrong?
An infection, injury or a genetic abnormality
Who are most vulnerable to homeostatic disruption?
Newborns and elderly
Why are newborns vulnerable to homeostatic disruption?
Because of the immaturity of their systems such as immune system, renal function, endocrine system, thermoregulation
Why are elderly more vulnerable to homeostatic disruptions?
They are less responsive to hormones
Have decreased efficiency of the heart and circulatory system
Have loss of neurones and neurotransmitters (nervous system is slower)
What are the two types of glands?
Exocrine and endocrine
What do exocrine glands do?
They secret their products into ducts that empty out into a surface or cavity
What do endocrine glands do?
They secret hormones into intracellular spaces, then hormones diffuse into the bloodstream,
Do endocrine glands have ducts?
No
Name 3 systems that produce hormones that aren’t glands
Stomach
Small intestines
Kidney
What are the main functions of the endocrine system
They regulate sodium and water balance (blood volume)
They regulate calcium and phosphate balance (preserves extra cellular fluid concentration for cell survival )
They regulate energy balance and control of macronutrient utilisation and storage
Regulate responses to stress
Regulate reproduction, sexual development and growth
What are the 2 types of hormones?
Non-steroidal hormones
Steroidal hormones
Which category of hormone attaches to a surface receptor?
Non-steroidal hormone
What mechanism do non-steroidal hormones work by?
Second-messenger mechanism
What are non-steroidal hormones?
Whole proteins which are short chains of amino acids or could just be one amino acid
Which category of hormone can pass through the cell membrane of the target organ?
Steroidal hormones
What are steroidal hormones?
Small lipid soluble chemical
Which category of hormone normally has a slower action?
Steroidal hormones
Which category of hormone will produce a hormone-receptor complex?
Steroidal hormone
What are the two types of non-steroidal hormone?
Protein or peptide hormones
Amino acid derived hormones
Which type of non-steroidal hormone is more common?
Protein or peptide hormones
How are protein/peptide hormones synthesised?
They are synthesises as pre-prohormones in which they undergo transformation at the required time
Where are protein/peptide hormones stored?
They are stored in secretory glands
Give some examples of protein/peptide hormones
Insulin
Glucagon
Adrenocorticotropic hormone (ACTH)
What are amino-acid derived hormones synthesised from?
Other amino acids
Give some examples of amino-acid derived hormones
Adrenaline
Noradrenaline
Dopamine
What are steroidal hormones derived from?
Cholesterol
Where are steroidal hormones synthesised?
Adrenal cortex
Gonads
Placenta
Which type of hormone requires binding proteins in the blood?
Steroidal hormones
Give some examples of steroidal hormones
Testosterone
Oestrogen
Progesterone
What are the 5 major pathways to hormone effects?
Paracrine pathway
Autocrine pathway
Endocrine (telecines) pathway
Synaptic pathway
Neuroendocrine pathway
What is the paracrine pathway?
It is where hormones are produced in a cell, secreted, act directly on nearby receptor cells
What is the autocrine pathway?
It is where the hormone is secreted by the cell and then that cell has a receptor for itself -> the hormone that is releases acts on the cell that has produced it
What is the endocrine pathway?
It is where hormone are produced in a cell, secreted and travel through blood vessels to distant cells, attach to receptors, act on the cell
What is the synaptic pathway?
Hormones produced in neurone, secreted and travel along axon to the synapse where they are re released and taken up by nearby neurone with appropriate receptors to exert an effect
What is the neuroendocrine pathway?
Hormones produced in neurone, secreted, travel along axon to synapse, released, take up into vascular system, travel to distant cells with appropriate receptors to exert an effect
The hypothalamus contains neurones that synthesise inhibiting and releasing hormones to act on what?
The pituitary gland
Name 4 common releasing hormones from the hypothalamus
Growth hormone RH
Thyrotropin RH
Corticotropin RH
Gonadotropin RH
Name 4 mechanisms that trigger the hypothalamus or pituitary gland to initiate a hormone release
Neurotransmitters
Injury
Release of chemical mediators after injury
Neuroendocrine signals
What are some of the causes of altered hormone function?
Impairment of the hypothalamus or pituitary gland
Impairment of the endocrine gland
Too much or too little hormone produced and secreted
Inactive hormone production by the gland
Inadequate hormone receptor binding
Lack of response by the target cell to the hormone
Impaired negative feedback loop
Hormone produced ectopically
Impaired hormone metabolism and elimination
Name some disorders of the endocrine system
Acromegaly
Gigantism
Achondroplasia
Hyperthyroidism
Hypothyroidism
Cushing syndrome
Diabetes mellitus/diabetes insipidus
Pheochromacytoma
Glucagonoma
Somatostatinoma
Where is the thyroid located ?
Anterior part of the neck
What is the shape of the thyroid gland?
Butterfly shape
What does the thyroid do?
Plays a critical role in stimulating metabolism
What does the thyroid facilitate the breakdown of?
Carbohydrates, proteins, fats for energy, stimulating heat and glucose production
What does the thyroid produce?
Structural proteins, enzymes and other hormones
What does the thyroid promote?
Growth and development in children both mentally and physically
What happens if thyroid hormone is released?
Increased glucose absorption
Release of lipid from adipose tissue
Metabolism of proteins from muscle tissue
Increased cholesterol breakdown in liver
Increased oxygen consumption
Increased body heat production
Increased cardiac output
Increased gastric motility
Increased muscle tone and reactivity
Increased activist action of cognitive processes
What is hyperthyroidism?
Excessive thyroid hormone production
What is hyperthyroidism caused by?
Increased stimulation of thyroid gland
Diseases of thyroid gland
Increased production of TSH by a pituitary tumour
Some medications containing high levels of iodine
Health food supplements containing seaweed
What is hypothyroidism?
Deficient thyroid hormone
Can be congenital or acquired
When does congenital hypothyroidism occur?
During foetal development
What causes congenital hypothyroidism?
A lack of thyroid development -> lack of thyroid hormone syntheisis
Wha does congenital hypothyroidism look like?
In uterus, maternal T4 crosses placenta so baby appears normal at birth
Results in developmental delay and impaired growth
What can help congenital hypothyroidism?
Thyroid replacement therapy
What is Grave’s disease?
Excessive stimulation of the thyroid gland, an autoimmune condition
Which gender is Grave’s disease more common in?
Women
Name some symptoms of Grave’s disease
Fine hair
Bulging eyeballs
Muscle wasting
Sweating
Tachycardia
Weight loss
Tremor
What is acquired hypothyroidism caused by?
Due to autoimmune disorder, iodine deficiency, surgical removal or radiation therapy to thyroid gland, medications that destroy the thyroid gland and genetic defects
Which sex is acquired hypothyroidism more common in?
Women
Name some symptoms of acquired hypothyroidism
Course, brittle hair
Large tongue
Hoarseness
Constipation
Muscle wasting
What is the treatment of acquired hypothyroidism?
Hormone replacement life long therapy
What is the treatment for Grave’s disease?
Radiation treatment of thyroid
Some medications to prevent hormone production
Can have part or all of the thyroid removed
What are 3 homeostatic regulation mechanisms?
Autoregulation
Nervous system
Endocrine
What bodily activities is calcium essential to?
Muscle function
Nerve function
Heart function
Bone density
What effect does calcitriol have on the skeletal system?
Promotes calcium and phosphate ion absorption along the digestive tract
What effect does growth hormone have on the skeletal system>
Stimulates osteoblast activity and synthesis of bone matrix
What effect does thyroxine have on the skeletal system?
With growth hormone, stimulates osteoblast activity and synthesis of bone matrix
What effect do sex hormones have on skeletal system?
Stimulates osteoblast activity and the synthesis of bone matrix; oestrogen stimulate epiphyseal closure earlier than androgens
What effect does parathyroid hormone have on skeletal system?
Stimulates osteoclast and osteoblast activity; elevates calcium ion concentration in body fluids
What effect does calcitonin have on skeletal system?
Inhibits osteoclast activity; promotes calcium loss by kidneys; reduces calcium ion concentrations in body fluids
What is the primary source of calcitriol?
Kidneys
What is the primary source of growth hormone?
Pituitary gland
What is the primary source of thyroxine?
Thyroid gland (follicle cells)
What is the primary source of sex hormones?
Ovaries
Testes
What is the primary source of calcitonin?
Thyroid gland
What does low calcium plasma levels cause the parathyroid glands to secrete?
Parathyroid hormone (PTH)
What are the 3 responses from PTH release?
Bone response -> osteoclasts stimulated to release stored calcium ions from bone
Intentional response -> rate of intestinal absorption of calcium increases
Kidney response -> kidneys retain calcium ions
What is the response to high calcium ion levels in plasma?
Parafollicular cells in the thyroid gland secret calcitonin
What are the 3 responses to release of calcitonin?
Bone response -> osteoclasts inhibited while osteoblasts continue to lock calcium ions in bone matrix
Intestinal response -> rate of intestinal absorption decreases
Kidney response -< kidneys allow calcium loss
What is diabetes?
The absence, deficit or resistance to insulin leading to hyperglycaemia
What is type 1 diabetes linked with?
Viral infection and autoimmune disease
What is type 2 diabetes linked with?
Obesity, age and ethnicity
What are the risk factors of type 1 diabetes?
Family history, viral infection
What are the risk factors of type 2 diabetes?
Obesity, hypertension, poor lifestyle, diet
