OCR A-Level Biology Chapter 14 Flashcards
14.1
What is the Endocrine System? give examples of glands.
Th system of endocrine glands which secrete hormones into the bloodstream. Some of the main glands are: - Pituitary gland -Thyroid gland - Pancreas
14.1
What are Hormones? What are some examples?
Are chemical messengers, can take several forms such as steroids, glycoproteins and polypeptides. Act on specific receptors known as target cells.
Steroids - Lipid soluble = can pass through membranes.
Non-steroids - Hydrophillic = can’t pass through membranes.
14.1
Hormones vs Neural Communication
Hormones: Nervous system:
-Slow transmission - Fast
-Via blood - Via neurones
-Travel everywhere - Travel specifically
-Slow, long lasting - Rapid, short
response lasting response
14.1
What is the Adrenal Cortex?
Production of hormones controlled by the hormones released from the pituitary gland.
E.g
Androgens - Small amounts of both male and female sex hormones are released.
14.1
What is the Adrenal Medulla?
Releases adrenaline and noradrenaline when the sympathetic nervous system is stimulated. Involved in fight or flight.
Adrenaline - Increases heart rate, raises glucose concentrations.
Noradrenaline - increases heart rate, widen pupils, widening of air passages in lungs.
14.2
What is the Pancreases role as an Exocrine Gland?
Most is made up of exocrine glandular tissue.
Produces digestive enzymes and pancreatic juice.
Secreted into the pancreatic duct, to the duodenum, to the small intestine.
Produces amylases, proteases and lipases.
14.2
What is the Pancreases role as an endocrine gland?
Produces insulin and glucagon which help control blood glucose concentration.
The Islets of Langerhans produces these hormones.
14.2
Differences between Exocrine and Endocrine tissues.
Exocrine: Endocrine:
- Darker -Lighter
- Small clusters -Large clusters
14.2
What are the different cells in the Islets of Langerhans and their functions?
Alpha cells - produce and secrete glucagon
Beta cells - produce and secrete insulin
A differential stain has to be used to distinguish the two, large pink cells for Alpha cells and small blue cells for Beta cells.
14.3
How is Blood Glucose Concentration increased?
- Diet
- Glycogenolysis = breaking down of glycogen into glucose.
- Gluconeogenisis = Production of glucose from non-carb sources.
14.3
How is Blood Glucose Concentration decreased?
- Respiration
- Glycogenisis = production of glycogen.
14.3
What is the role of Insulin?
Insulin lowers the blood glucose concentration as a part of homeostasis. It does this by:
- Increasing absorption of glucose
- Increasing rate of glycogenesis
- Increasing rate of glucose to fat conversion
- Inhibiting release of glucagon from the Alpha cells.
Insulin is broken down by enzymes in the liver so it has to be constantly secreted.
14.3
What is the role of Glucagon?
The liver and fat cells have glucagon receptors so they can respond to it. It responds by:
- Glycogenolysis.
- Reducing glucose absorption by the liver.
- Increasing glucagoneogenesis.
14.3
Describe the process of Insulin secretion.
- When normal, potassium channels are open and K ions diffuse out of the Beta cells.
- When concentration levels rise, glucose is transported into the Beta cell by a glucose transporter.
- Glucose is metabolised to ATP.
- ATP binds to ATP-sensitive channels so they close.
- K ions can no longer diffuse out, lowering cell potential so depolarisation occurs.
- voltage-gated calcium channels open because of depolarisation.
- Calcium ions enter and cause secretory vesicles to release the insulin into the bloodstream via exocytosis.
14.4
What is Diabetes type 1?
- The Beta cells in the islets of Langerhans are unable to produce Insulin due to an autoimmune disease that attacks these cells.
- It can’t be prevented or cured.
- Arises in childhood.
