hormones Flashcards
what is the definition of hormone?
chemical substance produced in minute quantities by an endocrine gland. It is transport in the bloodstream to target organs where it exerts its effects. After hormones have performed their functions, they are eventually destroyed by the liver and excreted by the kidney
what are some characteristics of hormones?
- hormone production of some endocrine glands is controlled by nervous system
- others are regulated by chemical substances
what is an endocrine gland?
- ductless glands that produce hormones and secrete the hormones into the bloodstream directly
what is the effect of an endocrine gland?
hormone responses are slower as it depends on rate of bloodflow vs nerve impulses transmitted in the form of electrical signals through neurones for reflex
what does the exocrine gland in the pancreas do?
produce pancreatic juice, which is carried by pancreatic duct to duodenum
what does the endocrine gland do in the pancreas?
contains special group of cells called islets of Langerhans which secretes hormones insulin and glucagon into bloodstream
what hormone does the pituitary gland secrete?
- anti-diuretic hormone (ADH)
- several hormones that controls secretion of hormones of other endocrine glands (e.g. growth)
what hormone does the adrenal gland (medulla) secrete?
adrenaline
what hormone does the pancrease secrete?
islets of langerhans
what hormone do the ovaries secrete?
- oestrogen
- progesterone
what hormone does the testes secrete?
testosterone
what hormone does the hypothalamus secrete?
some pituitary hormones
what happens when amount of insulin secreted is normal?
- insulin decreases blood glucose concentration by
- increases permeaility of cell membranes to glucose, increasing rate of glucose uptake by cells
- stimulating liver and muscle cells to convert excess glucose into glycogen for storage
- increasing oxidation of glucose dry tissue respiration
what happens when amount of insulin secreted is below normal?
- glucose cannot be stored or utilised by tissue cells, so blood glucose concentration rises
- some glucose is lost in urine, giving rise to diabetes mellitus
- muscle cells do not have reserves of glycogen and the body grows weak and continuously loses weight
- body oxidises fat instead of glucose to release energy. This results in production of ketones which are then excreted in urine
what happens when amount of insulin secreted is above normal?
- abnormal decrease in blood glucose concentration
- low blood glucose concentration resulting in stroke
- coma and death may follow
what is the purpose of glucagon?
main target of glucagon is liver
- stimulates liver to convert glucogen to glucose
- convert fats and amino acids into glucose
insulin + glucagon regulate the blood glucose concentration (homeostatic mechanism)
what is diabetes mellitus?
a disease where the body is unable to control its blood glucose concentration to remain within normal limits. Lack of insulin secretion cannot stimulate liver to convert excess glucose to glycogen for storage. Hence, blood glucose concentration rises, leading to a persistently high level that exceeds kidney’s ability to completely reabsorb all the glucose present in glomerular filtrate and glucose that is not reabsorbed is excreted in urine
what is type 1 diabetes?
- develops early in life, aka juvenile or early-onset diabetes
what does type 1 diabetes do?
- islets of Langerhans are unable to produce/secrete sufficient insulin
what is type 2 diabetes?
develops later in a person’s life and is called late-onset diabetes
what does type 2 diabetes do?
develops when target cells, e.g. muscle cells, do not respond well to insulin
what are the signs of diabetes?
- persistently high blood glucose level
- healing of wounds is slow or difficult
- present of glucose in urine after meal
what is the treatment of type 1 diabetes?
- ensure supply of sugary foods such as glucose sweets in case blood glucose drops too low if they use too much insulin, exercise too much or eat too little
- inject insulin regularly
what is the treatment for type 2 diabetes?
- exercise and regulate carbohydrate content in diet
- if lifestyle changes fail, take medication and insulin injections
what is adrenaline?
- adrenal medulla secretes hormone adrenaline when you are afraid/angry/anxious/stressed
- adrenaline prepares your body for fight or flight or for states of emergencies
- response are temporary as adrenaline is a short-lived hormone
- destroyed by liver excreted by kidney
what is the response to stimuli?
- stimuli activate the hypothalamus in the brain
- transmission of impulses down spinal cord
- motor neurone transmits impulses to adrenal gland
- adrenal gland secretes adrenaline into bloodstream
- blood transports adrenaline to target organs
what are the effects of adrenaline?
- stimulate liver to convert glycogen to glucose, which is released back into the bloodstream. This increases blood glucose concentration so more glucose ix oxidised to release energy during cellular respiration, for fight or flight
- cause coronary arteries to widen, thus transporting more blood containing O2 and glucose to heart muscles for cellular respiration to release energy. Hnece, heart has more energy to pump faster to transport more glucose and oxygenated blood to the skeletal muscles so muscular contractions can take place for fight or flight
- increases metabolic rate –> more energy reduced in tissue respiration
- increases rate and depth of ventilation –> increases rate of uptake of O2 by lungs
- increases rate of blood clotting
- constricts arterioles to the gut –> decrease digestive activities
- constricts arterioles to the skin –> cause paleness, channeling more blood to muscles (e.g. in limb)
- dilate pupils –> enhance vision
- constracts hair muscles, produce “goose bumps”, hair stands on ends
what is the mode of transmission for endocrine gland?
- involves hormoens which are chemical substances
- hormones transport by blood
what is the mode of transmission for nervous controls?
- invovles nerve impulses which are electric signals
- impulses transmitted by neurones
what is the speed and duration of response in the endocrine gland?
- usually slow responses
- responses may be short-lived or long lived (growth hormone)
what is the speed and duration of response for nervous system?
- usually quick responses
- responses are short-lived
what are the number of target organs affects in endocrine gland?
- always involuntary
- may affect more than one target organ
what is the number of target organs affected in nervous system?
- involuntary or voluntary
- usually localised
