IB biology: topic 6: hormones

what type of cells make up the Islets of Langerhans?

alpha and beta cells

what is the exocrine function of the pancreas?

secretes digestive enzymes into the pancreatic duct

what is the endocrine function of the pancreas?

secretes hormones (insulin and glucagon) directly into the blood

what is the pancreatic juice made up of?

amylase (carbohydrase), trypsinogen (protease), lipase

what is the role of alpha cells in the pancreas?

manufacture and secrete glucagon

what is the role of beta cells in the pancreas?

manufacture and secrete insulin

what is homeostasis?

the control process that ensures the internal environment of the body remains constant within certain limits despite changes that occur in the external environment

what systems are involved in homeostasis?

endocrine system and nervous system

what are hormones?

chemical messengers that are secreted directly into the blood which get carried to organ to exert their functions, they are produced in glands.

what is a negative feedback?

whenever a change occurs in a system, the change automatically causes a corrective mechanism to start, which reverses the original change and brings the system back to normal.

the bigger then change the bigger the corrective mechanism.

what are the normal blood glucose levels?

4- 8mmol dm-3 (milli mol per decimetre cubed)

what cells in the pancreas act when blood glucose levels are too high?

beta cells secrete insulin which stimulates liver and skeletal muscle to convert glucose into glycogen

what cells in the pancreas act when blood glucose levels are too low?

alpha cells secrete glucagon which stimulates liver to convert glycogen to glucose.

where are the Islets of Langerhans found?

in the pancreas

what organ detects changes in blood glucose concentration?

pancreas

type I diabetes: onset?

childhood

type II diabetes: onset?

later in life (due to obesity/ageing)

type I diabetes: cause?

body no longer makes any insulin (thought to be by autoimmune response which the body destroys its own beta cells)

type II diabetes: cause?

body does not respond to insulin/not enough is produced (typically caused by obesity, diets high in sugar, genetics)

type I diabetes: treatment?

insulin injections

type II diabetes: treatment?

exercise and healthy eating

what is the function of thyroxine?

regulates the metabolic rate and helps control body temperature

what are benefits of a higher metabolic rate?

increased protein synthesis,

increased generation of heat,

increased growth

what are the consequences of an underactive thyroid?

lack of energy,

depression and forgetfulness,

weight gain despite loss of appetite,

feeling cold,

constipation

describe the normal release of thyroxin by the thyroid?

1. hypothalamus detects low thyroxin levels and triggers release of TRH
2. pituitary gland produces thyroid stimulating hormone (TSH),
3. TSH triggers thyroid to release thyroxin,
4. high thyroxin levels instructs hypothalamus to stop releasing TRH

what chemical is vital for the production of thyroxin? why?

iodine - thyroxin is composed of 4 iodine atoms

what is leptin?

a protein hormone secreted by adipose cells (fat storage cells)

what are the target cells for leptin?

group of cells in hypothalamus that contribute to appetite control

what happens when adipose tissue increases?

blood leptin concentrations rise, causing long-term appetite inhibition and reduced food intake

what are the consequences of increased leptin levels?

more appetite inhibition and so reduced food intake

what is the role of melatonin?

maintains circadian rhythms

what gland releases melatonin?

pineal

what triggers the release of melatonin?

darkness, cells in hypothalamus trigger pineal to release melatonin, light causes levels to fall again

what are the effects of melatonin?

increased drowsiness,

drop in body temperature,

decreased urine production