Endocrine System 2 Flashcards
What is normal range?
Set of values for a regulated variable. These can fluctuate around a set point
What is a set point?
Physiological value of which a normal range functions
True or false? Individual normals tend to be wider than the range of value of the population.
False
Describe the negative feedback loop
The stimulus is detected by the sensors and this sends signals to the control centre which sends signals to the effectors to oppose the effect of the stimulus.
What is the role of the sensors?
Monitor the variable and detect changes
What is the role of the control centre?
Compare the variable’s changed values to the set point and sends signals to the effector.
What is the role of the effector?
Acts to oppose the stimulus
What is positive feedback?
Amplification. When a process is driven to completion.
If a variable goes up, the feedback makes it go up further.
What is the purpose of the endocrine system?
Releases hormones into the blood stream to bind to the membrane receptors of target cells.
What is the relative speed of the endocrine system?
Slow, but long lasting
What are hormones?
Chemicals that bind to specific target cells within the body
What are hormones made up of?
Amino acids or cholesterol
Where do hormones come from?q
Released by endocrine gland cells
How do hormones travel around the body?
In the bloodstream
How do water-soluble hormones work?
They do not require carrier proteins to travel in the blood but cannot cross cell membranes so they bind to receptors on the membrane of the target cell
How do lipid-soluble hormones work?
Require carrier proteins to travel in the blood but can diffuse easily across plasma membranes to =bind to the intracellular receptors inside of a target nucleus.
Are receptors hormone specific?
Yes
How do lipid soluble hormones produce a response?
Stimulate creation of new proteins, enzymes, to produce a response.
How do water soluble hormones produce a response?
Activate a second messenger system to produce a response
How do hormones know when to stop?
The body will break them down/ recycle them or they are excreted in sweat, urine, or faeces.
What is an example of a water-soluble hormone?
Adrenaline
What is an example of lipid-soluble hormone
Thyroid hormone and cortisol
How are lipid soluble hormones synthesised and stored?
Some are premade and some are made only when required
How are water soluble hormones synthesised and stored?
All are premade and stored
What kind of response does a lipid soluble hormone evoke?
Cellular Response
Is the action mechanism for lipid soluble fast or slow?
Slow because protein synthesis takes a long time
How fast is the action mechanism for water-soluble hormones?
2nd messengers are premade so this is a fast response.
Describe the action mechanism for Water soluble hormone
Receptors activate G-proteins either inhibits or activates 2nd messengers which affect the actions of other proteins (ion channels or enzymes)
What are the 2 types of 2nd messengers?
cAMP and Ca ions.
What are the two glands involved in the regulation of plasma glucose and calcium concentration?
Parathyroid Glands, Thyroid gland, and the kidneys
Why does calcium need to be regulated?
Because there needs to be enough calcium in the blood for cells to use when they need it
How does the body use calcium?
Calcium is a second messenger which affects the actions of proteins and ion channels.
Interacts with vesicles to facilitate release of neurotransmitter
Interacts with myofilaments to form cross-bridges.
All muscle requires Ca
Where is most calcium stored in the body?
In the bones, it is important for making bones hard
How does calcium enter the blood plasma?
Absorbed from the digestive tract?
Resorbed from bone broken down by osteocytes
Reabsorbed back into blood from kidneys
How does the calcium get removed from the blood?
Deposited back into the bone by osteoblasts
Filtered out of the blood by the kidneys
Which organs/ glands are involved in Ca homeostasis?
Parathyroid
Kidneys
Thyroid gland
Bones
Digestive system?
How are the parathyroid glands involved in the regulation of Ca?
They secrete PTH (parathyroid hormone)
How many parathyroid glands are there?
4
How are kidneys involved in Ca homeostasis
Stimulated by PTH to secrete calcitriol
Filter blood, reabsorbed and filters Ca into the blood
How is the thyroid gland involved in Ca homeostasis?
Secretes calcitonin (minor role)
How are bones involved in Ca homeostasis
Osteoblasts remove Ca to store as bone
Osteoclasts release Ca by breaking down bone
What hormones stimulate the bone mechanisms in Ca homeostasis?
Parathyroid, calcitriol, and calcitonin
How is the digestive system involved in Ca homeostasis?
Absorbs calcium from digesting food
What hormone regulates the digestive system in Ca homeostasis?
Calcitriol
What are the sensors in Ca homeostasis?
Parathyroid glands, detect calcium levels in blood flowing through them.
What are the effectors for Ca homeostasis?
Bone, Kidneys (calcium reabsorbed), kidneys (vitamin D converted to calcitriol), and digestive tract
What is hypercalcemia?
High plasma Calcium levels
What are the two sensors for hypercalcemia?
Thyroid and parathyroid glands
What role does the thyroid have in correcting hypercalcemia
Releases calcitonin, which sends messages to the bones and the kidneys to perform their functions
What gland is involved in plasma glucose homeostasis
Pancreas
Why is blood glucose regulated?
Because it needs to be available if cells require it
What is the purpose of glucose in the body?
Used to make ATP and other substances essential for body function
How is glucose stored in the body?
Stored as glycogen
How does glucose enter the blood plasma?
Absorbed by the digestive tract.
Released into the blood by the liver
How is glucose removed from blood plasma?
Removed from the blood by body cells
Removed and stored in liver and skeletal muscle as glycogen
Stored in adipose as fat
When is more glucose required in the body?
During periods of growth, stress, and exercise
Which glands involved in glucose homeostasis?
Pancreas, liver
How is the pancreas involved in glucose homeostasis?
Pancreatic cells secrete glucagon and insulin
What do alpha islet cells secrete?
Glucagon
What do beta islets cells secrete?
Insulin
Is glucose high or low in a fasting state?
Low
Describe what happens during hypoglycemia?
Alpha cells detect low glucose and release glucagon. This sends signals to the liver which can react in 3 different ways
What occurs during gluconeogenesis?
Glucose molecules are built and released into the blood
What occurs during glycogenolysis?
Break down of glycogen to release more glucose into the blood
What occurs during ketone synthesis?
More ketones are built to release into the blood
Describe what happens during hyperglycemia
Beta islet cells detect high glucose and releases insulin.
All body cells will increase glucose intake
Liver and muscle take excess glucose from the blood to store as glycogen
Adipose cells store as fat
How does the hypothalamus connect to the anterior pituitary gland?
Releases chemicals into a blood portal to connect to the anterior pituitary gland cells.
How does the hypothalamus connect to the posterior pituitary gland?
Hypothalamic neurons have long axons that terminate in the posterior pituitary gland?
What are posterior pituitary glands made up of?
Hypothalamic neuron cell bodies.
Where are the posterior pituitary hormones stored?
Held in axon terminals until required to be released into the cell body when an AP causes them to become depolarised.
What are the two posterior pituitary hormones?
Oxycontin
ADH (anti-diuretic)
WHat are the features of oxytocin?
Water-soluble
Stimulates milk release during breastfeeding
Stimulates contract of uterine muscles during childbirth
What are the features of ADH?
Water-soluble
Stimulates kidney to reabsorb water when dehydrated
Secreted during exercise and stress response
What are the hormones secreted by the anterior pituitary gland?
GH (growth hormone)
Thyroid stimulating hormone (TSH)
Adrenocorticotropin Hormone (ACTH)
What are the features of GH?
Water-soluble
Stimulates liver, skeletal muscle and adipose for fuel metabolism
Stimulates liver to release IGF for growth
What is the purpose of TSH?
Water-soluble
Stimulates the thyroid to release thyroid hormones
What is the purpose of ACTH?
Water-soluble
Stimulates the adrenal gland to release cortisol
What glands/organs are involved in cell metabolism?
Hypothalamus
Pituitary Gland
Thyroid Gland
Describe the general pattern of hormone release from the hypothalamus
Releases or inhibits hormone release to the pituitary gland. A 3rd hormone will then be sent to the target organ and effectors.
Describe the Hypothalamic-pituitary-thyroid axis
Hypothalamus secretes (TRH) thyrotropin-releasing hormone
Anterior pituitary gland secretes TSH
Thyroid gland secretes thyroid hormones T3/4
What is the purpose of the Hypothalamic-pituitary-thyroid axis
Stimulated by exercise and cold stress
Increases basal metabolic rate and stimulates growth in fetus during early childhood
Increases mental alertness
Where is the thyroid gland located?
Wraps around the trachea, below the adams apple.
On the anterior and lateral surface of the trachea.
What hormones are produced by the thyroid?
Thyroid Hormones (T3 and 4)
Calcitonin
Describe the synthesis and storage of thyroid hormones
Thyroglobulin (TGB) make in thyroid follicles
Iodine enteral cells and reacts with tyrosine in TGB
T3 and T4 detach from TGB as needed and travel in blood with a carrier protein
What is TGB made up of?
Thyroglobulin contains tyrosine (Y)
Describe target cell activation by thyroid hormone
Made and stored until required.
Travels bound to a carrier protein
Bind to receptor within the nucleus
Actives genes to form different proteins
What is BSR?
Basal metabolic rate is the energy required for basic functions such as blood circulation and respiration
How do thyroid hormones increase BMR?
Thermogenesis
Oxygen consumption
Fat and protein breakdown
What glands/ organs are involved in cell metabolism and growth?
Hypothalamus
Pituitary Gland
When are the highest GH concentrations?
When asleep and in puberty
What is a direct effect of GH?
Fuel mobilisation.
Describe fuel mobilisation in muscle, liver, and adipose
In muscle it inhibits uptake of glucose and stimulates protein synthesis
In the liver it stimulates glucose synthesis
In adipose it increases fat breakdown
What is an indirect effect of GH?
Growth, IGF is released from the liver which stimulates growth in bones
Describe the Hypothalamic-Pituitary-Liver axis
Hypothalamus either secretes GHRH (GH releasing hormone) or GHIH (GH inhibiting)
The anterior pituitary gland then secretes subsequent amounts of GH
This causes the liver to secretes insulin-like growth factor (IGF-1), which causes growth of cells
GH also causes fuel mobilsation in liver, muscle, and fat
What are the two types of hormones that the hypothalamic neurons secrete?
Releasing or inhibiting hormones
Describe the general releasing pattern of hormones from the hypothalamus
Hypothalamus
Anterior Pituitary Gland
Target Endocrine Organ
Effectors
When is cortisol the highest?
In the morning as it fluctuates in a circadian rhythm
Where is cortisol secreted from?
Outer layer of adrenal glands
What is secreted from the outer layer of the adrenal glands?
Aldosterone and cortisol
Where are the adrenal glands located?
on top of the kidneys
Where are the catecholamines secreted from?
Medulla of the adrenal glands
What kind of protein is cortisol?
Lipid soluble
What are the normal effects of cortisol?
Increases blood glucose by stimulating
- pancreas
- liover
- skeletal muscles
- adipose
Maintains blood pressure
Suppresses inflammation
What hormone does the hypothalamus secrete for the Pituitary gland?
Corticotropin-releasing (CRH)
Describe the Hypothalamic-Pituitary-Adrenal Axis
Hypothalamus secretes CRH to the anterior pituitary which causes it to secrete ACTH (Adrenocorticotropin) to the adrenal gland which releases cortisol
What are the target effectors of the adrenal gland (cortisol)?
Liver, muscle, adipose
Pancreas
Cardiovascular system
Immune system
What are the 3 phases of stress response?
Alarm Stage
Resistance Stage
Exhaustion stage
Describe the alarm stage of the stress response and what happens to the body
Increased oxygen intake
Increased oxygen and glucose circulated to the brain and skeletal muscle
Reduce activation of unnecessary body function (e.g. saliva)
Describe how stress triggers the sympathetic nervous system
AP sent from emotion centre of the brain
Hypothalamic neurons control centre for sympathetic nervous system
Stress triggers the hypothalamus to activate the sympathetic nervous system
Describe the release of catecholamine
Sympathetic nerves stimulate the adrenal gland (medulla) and catecholamine is released into the blood stream to target organs
What are the corticolamines?
Adrenaline and noradrenaline
What type of hormone is a catecholamine?
Water-soluble
What happens to the lungs due to catecholamine?
Rate of breathing increases as airway dialates
What happens to the heart due to catecholamine?
Heart rate and strength of contraction
What happens to the blood vessels due to catecholamine?
Blood pressure (vasoconstriction)
What happens to the liver due to catecholamine?
Glycogen breakdown (glycogenolysis)
Glucose synthesis (gluconeogenesis)
What happens to the skeletal muscle due to catecholamine?
Glycogen breakdown (glycogenolysis)
What happens to the adipose due to catecholamine?
Fat break down
What happens during the resistance phase of stress?
Body working to resist the effect of stress, stress lasts more than a few hours and glycogen stores have been used up so lipid and protein stored must be mobilised
What is the most dominant hormone of the resistance phase?
Cortisol
Describe the process of fuel mobilisation into blood during the resistance phase
Cortisol is released
Glucagon is released from pancreas
Adrenaline is released
GH is released from pituitary
Describe the process of increased blood pressure during the resistance phase
Cortisol is released
ADH is released
Aldosterone is released from adrenal cortex
Describe the process of suppressed inflamation during the resistance phase
Cortisol is released
How do blood vessels vasoconstrict?
ASH stimulates constriction.
ADH stimulates the kidney to reabsorb water into the plasma
Aldosterone stimulates the kidneys more Na into the plasma.
Does vasoconstriction cause blood pressure to increase or decrease?
Increase
Describe the exhaustion phase of stress
Lasts for weeks to years. ‘
Lipid reserves used up and organs begin to get damaged as structural proteins begin to get broken down
What are the two things that can go wrong with hormone secretion?
Hyposecretion
Hypersecretion
What can go wrong with hormone signalling?
Hyposensitivity
What disease is caused by the hyposecretion of cortisol?
Addison’s Disease
Which disease is caused by the hypersecretion of cortisol?
Cushing’s disease
What are the symptoms of Addison’s disease?
Low blood pressure
fatigue
Loss of appetite
What is a cause of Addison’s Disease?
Autoimmune disease that attacks the adrenal cortex
What is a common cause of Cushing’s disease?
Adrenal cortex tumor
Taking glucocorticoid medication for long periods of time
What are the symptoms of Cushing’s disease?
High blood pressure
Thinning of arms and legs and weight gain in torso
Moon face, buffalo hump
Stretch marks and easy bruising
What disease is caused by the hyposecretion of growth hormone?
Dwarfism
What disease is caused by the hypersecretion of growth hormone?
Gigantism
Acromegaly
What is a common cause of dwarfism?
Genetic mutation or inheritance
What is a common cause of gigantism?
Pituitary gland tumor in childhood
What is a common cause of acromegaly?
Pituitary gland tumor in early adulthood
What is a symptom of acromegaly?
Large and irregularly shaped extremities and facial features
What diseases are called by the hyposecretion of thyroid hormone?
Hypothyroidism
Simple goitre
What is a cause of infantile hypothyroidism?
Missing or poorly developed thyroid
Poorly functioning anterior pituitary
Lack of iodine in mother’s diet
What are the symptoms of infantile hypothyroidism?
Low metabolic rate
Delayed growth
Swollen tongue and around eyes
What is a cause of adult hypothyroidism?
Autoimmune disease
Iodine deficiency
Removal of thyroid
What is a symptom of adult hypothyoidism?
Low metabolic rate
Tiredness
Cold sensitivity
Depression
What disease is caused by hypersecretion of thyroid hormone?
Grave’s disease
What is a cause of Graves disease?
Autoimmune disorder
What are some symptoms of Graves disease?
High metabolic rate
Increased heart rate
Sensitive to heat
Nervousness
Bulging eyes
Goitre
What disease is caused by hypersecretion of parathyroid hormone?
Hyperparathyroidism
What disease is caused hyposecretion of parathyroid hormone?
Hypothyroidism
What is a cause for hyperthyroidism?
Parathyroid tumor
What are the common causes of hypothyroidism?
Damaged parathyroid gland due to genetic or autoimmune disease
What are the symptoms of hyperthyroidism?
Soft fragile bones
Kidney stones
various problems related to calcium’s many functions
What are the symptoms of hypothyroidism?
Muscle tetanus
Seizures
Decreased cardiac function
What disease is caused by the hyposecretion of insulin?
Type I diabetes Mellitus
What is a common cause of Type I diabetes Mellitus?
Beta islet cells in pancreas destroyed by virus and autoimmune disease
What are some symptoms of Type I diabetes Mellitus?
Polyuria (excessive urine production)
Polydipsia (excessive thirst)
Cardiovascular issues
What disease is caused by hyposensitivity and hyposecretion of insulin?
Type II diabetes
What disease is caused by insulin hyposensitivity?
insulin resistance
What is a cause of insulin resistance?
Chronically high insulin levels
