Endocrine + homeostasis (Human Bio) Flashcards
What are endocrine glands
glands that secrete hormones into the extracellular fluid that surrounds the cell that make up the glands
Describe the functioning of steroid hormones
Lipid soluble (do not dissolve in water)
Once they are released into the blood, the hormones bind to transport proteins, enabling them to travel in the bloodstream
When they reach target cells, steroid hormones separate from the transport proteins and diffuse across the cell membrane
Inside the cell they combine with a receptor protein in cytoplasm or nucleus
Hormone receptor complex activates genes controlling formation of particular proteins
Transcription is stimulated and therefore protein synthesis
E.g. oestrogen, progesterone
Describe protein/amine hormones
Protein and Amine hormones
Water soluble not lipid soluble, unable to diffuse across cell membrane
Attaches to receptor proteins in membrane of the target cell
Combination of the hormone with the receptor causes a secondary messenger substance to diffuse through the cell and activate particular enzymes
E.g. insulin binds to a receptor protein and leads to an increase in glucose absorption by cell
describe hypothalamus
Regulates body functions (e.g. heart rate, body temperature)
Serves as a connector between the nervous system and endocrine system
Describe relationship between hypothalamus and pituitary gland
Secretes releasing factors, which stimulate the secretion of hormones, or inhibiting factors, which slow down the secretion of a hormone
These factors travel through blood vessels to anterior lobe of pituitary gland
What is the infundibulum
A stalk that joins the hypothalamus and pituitary gland
What does the pituitary gland consist of
Anterior lobe → joined to hypothalamus by blood vessels in infundibulum
Posterior lobe → joined to hypothalamus by nerves fibres
What are some hormones released by anterior lobe
FLAT PiG
Gonadotropins
Hormones that affect the gonads (testes and ovaries)
(Follicle stimulating hormone is released aswell)
Growth hormones
Stimulates body growth, protein synthesis
Thyroid-stimulating hormone (TSH)
Stimulates production and release of hormones from the thyroid gland
Adrenocorticotropic hormone (ACTH) Controls production and release of some the hormones from the cortex of the adrenal glands
Prolactin
Works with hormones to initiate and maintain milk production in females
What are some hormones released by the posterior lobe
Oxytocin
Stimulates contraction of the muscles of the uterus
Also stimulates mammary glands resulting in release of milk during breastfeeding
Antidiuretic hormone (ADH) Causes kidneys to remove water from urine that is forming
Describe causes, symptoms, diagnosis, treatment of Diabetes 1
Cause:
Immune system fault causing the breakdown of beta cells in the Islets of Langerhan of the pancreas which produce insulin
Symptoms: Increased thirst Frequent urination Fatigue Weight loss
Diagnosis:
Blood test
Treatment:
Insulin injections
Describe causes, symptoms, diagnosis, treatment of Diabetes 2
Cause:
being obese or overweight, produces insulin but cells don’t respond (fat affects receptors)
Symptoms: Unexplained weight loss Increased thirst Increased hunger Fatigue Frequent urination
Diagnosis:
Blood test
Treatment:
Managment plan to keep blood glucose level in normal range = e.g. diet, exercise
Describe hypothyroidism
Cause:
Too little thyroxine, iodine deficiency in diet can prevent thyroid gland from making enough hormones
Symptoms
Slow heart rate
Weight gain
Goitre (neck swelling)
Diagnosis:
Blood test
Treatment:
Increase iodine in diet
thyroid hormone tablets
Describe hyperthyroidism (e.g. graves disease)
Cause:
Too much thyroxine due to enlarged thyroid gland therefore produces too much of hormone
Symptoms:
Rapid heart rate
Weight loss
Protruding eyes
Diagnosis:
Blood test
Treatment:
Drugs that block thyroid glands
Example of a positive feedback loop
Childbirth
Labour initiated =by secretion of hormone oxytocin from posterior lobe of pituitary gland
Oxytocin causes contraction of uterus
Contraction pushes baby’s head against the mothers cervix
Stimulation of the cervix causes it to send nerve impulses to the brain, which respond by instructing pituitary gland to secrete more oxytocin
The increased oxytocin makes uterus contract more strongly which push baby’s head more forcibly against cervix, sending more impulses to the brain for oxytocin secretion, making the uterine contractions increasingly intensify
Once baby is delivered, nerve impulses messaged are ceased and positive feedback cycle stop
Describe the role of the liver
Liver is able to convert glucose into glycogen when glucose levels are high like after a meal
And is able to convert glycogen back to glucose if blood glucose is low like during exercise
What does the hepatic portal vein do?
A vein that delivers blood with glucose to the liver from other organs
What does the liver do with glucose it receives?
Be removed from blood by liver to provide energy for liver functioning
Be removed by the liver and/or muscles and converted into glycogen for storage
Continue to circulate blood, available for body cells to absorb and use as a source for energy
Be converted into fat for long-term storage if it is in excess of that required to maintain both normal blood sugar and tissue glycogen level
Describe glycogenesis
Forms glycogen from glucose and is stimulated by insulin which is secreted by beta cells in Islets of Langerhans
Describe glycogenolysis
Converts glycogen back to glucose and is stimulated by glucagon which is secreted by alpha cells in Islets of Langerhans
What is the role of the pancreas
Contains hormone secreting cells called islets of Langerhans which contain:
Contain Alpha cells which secrete glucagon –> stimulates glycogenolysis in the liver
Contain Beta cells which secrete insulin –> stimulates glycogenesis
What is the role of the adrenal glands
Split into the adrenal cortex and adrenal medulla
Adrenal cortex secretes cortisol
Adrenal medulla secretes adrenaline and noraderenaline
What is a negative feedback loop for reducing body temp
Stimulus: rise in external/core body temp
Receptors: peripheral thermoreceptors in skin/thermoreceptors in hypothalamus
Modulator: hypothalamus receives and then sends nerve impulse
Effector:
- sweat glands
- skin
- behavioural changes
- Thyroid (to secrete less thyroxine)
Response:
- secrete sweat
- vasodilation (lose heat)
- take of piece of clothing
- decrease in metabolic rate
Feedback: decrease in body temp
Negative feedback loop for increase in osmotic pressure
Stimulus: rise in osmotic pressure due to decrease of water in blood
Receptor: Osmoreceptors in hypothalamus detect rise in osmotic pressure
Modulator: Hypothalamus receives impulse and stimulates posterior lobe of pituitary gland
Effector: posterior lobe secretes more anti-diuretic hormone (ADH) which effects the nephrons tubules in the kidney and permeability is increased
Response: More water is absorbed into the blood from the distal convoluting tube and collecting duct
Feedback: Osmotic pressure decreases
Negative feedback loop to increase pH
Stimulus: Breathing rate decreases, increases carbon dioxide in body which results in a decrease in pH
Receptor: Chemoreceptors in aortic and carotid bodies detect change
Modulator: respiratory system in medulla oblongata is stimulated
Effector: nerve impulses are sent to muscles in respiratory system
Response: contraction rate of muscles in respiratory system increase
Feedback: This results in an increase in breathing rate, which decreases the carbon dioxide in body and increases the body’s pH
