F214 Flashcards
Define homeostasis
Maintaining stable internal environment within narrow limits even though environment is changing
Describe how negative feedback is used to control blood glucose concentration
- Alpha and beta cells detect change in blood glucose
- Higher glucose concentration:
- > beta cells secrete insulin
- > increased uptake of glucose by hepatocytes
- > glycogenesis
- > increased use of glucose in respiration
- Lower glucose concentration
- > alpha cells secrete glucagon
- > increased glycogenolysis
- > gluconeogenesis
- > glucose leaves by facilitated diffusion
Suggest why a high intake of protein will result in a high concentration of urea in urine
- High intake of protein = large amount of amino acids
- Amino acids cannot be stored
- Amino acids deaminated
- Large amount of ammonia enters ornithine cycle
- Increased blood concentration of urea
- Higher concentration of urea in blood increases water absorption from urine
Outline the hormonal and neuronal mechanisms involved in control of heart rate
- Adrenaline increases heart rate
- Cardiovascular centre in medulla oblongata
- Nervous connection to sinoatrial node
- Vagus decreases heart rate (para.)
- Accelerator increases heart rate (sym)
- High bp detected by baroreceptors
- Low blood pH detected by chemoreceptors
- Receptors in carotid sinus
Explain how the glomerulus is able to perform its function
- Afferent arteriole is wider than efferent arteriole
- Build up if hydrostatic pressure
- Endothelium of capillary has fenestrations
- Allows ultrafiltration
Effects of kidney failure on the composition of blood
- High in urea
- High in ions/salts
- High in water
Explain the need for close matching on the donated kidney to the recipient
- Donated kidney will be recognised as foreign
- Antigens will be different
- Causes rejection
- By immune system
- Use of immunosuppressant drugs
- Suitable size in specific cases eg if recipient is a small child
Describe and explain how the resting potential is established and how it is maintained in a sensory neurone
- Sodium/ potassium pump uses ATP
- Pumps sodium out, potassium in
- Potassium ions diffuse back out of cell
- Membrane less permeable to sodium
- Voltage gated sodium channels closed
Explain what might happen to a person if the liver did not break down insulin
- Blood glucose level would fall below norm
- Glucose would continue to be taken up by cells
- Less glucose available in blood so mitochondria cannot generate enough ATP
- coma/ death
What is meant by the term autotroph
Can make organic molecules from inorganic molecules
What is meant by the term heterotroph
Relies on organic molecules that have been made by another organism
Describe how light is harvested in chloroplast membranes
- Primary and accessory pigments form an antenna complex (photosystem)
- Photon absorbed by pigment molecules
- Electrons excited and move to higher energy level and returned to pigment
- Photon passed from one pigment to another
- Photon passed to chlorophyll a
- Range of accessory pigments allow range of wavelengths to be absorbed
Describe the different ways in which the pancreas acts as both an endocrine and an exocrine gland.
Endocrine - Hormones released into blood - Beta cells secrete insulin - Alpha cells secrete glucagon - Islets detect blood glucose conc Exocrine - Fluid released into duct - Triggered by nervous stimulation - Pancreatic secretions into duodenum - Alkaline - Contains lipase, amylase
Where are glucocorticoids produced?
Adrenal cortex
Explain the role of the loop of Henle in the production of urine.
- Role of Loop of Henle is to cause a decrease in water potential in medulla
- In ascending limb active transport outwards of sodium and calcium ions
- Walls of descending limb permeable to water
- Water potential of tissues surrounding collecting duct is Lowe than fluid inside
- Water removed from filtrate in collecting duct
- Acts as a countercurrent multiplier
