Exam Qs ch 6- Organisms respond- Exam questions Flashcards
Describe + explain the events which occur at a point in the motor neurone during the passage of a nerve impulse
- Depolarisation
- To threshold
- Increased permeability of membrane to Na ions
- Na ions enter
- By diffusion
- Causes a positive PD in membrane
- K gates open
- Resting potential re-astablished
Describe the events which allow the transmission to take place across a synapse
- Increased permeability of presynaptic membrane to Ca ions
- Ca ions enter
- Vesicles fuse with membrane
- Exocytosis of neurotransmitter
- Diffuses across synaptic cleft
- Binds to receptors on post synaptic membrane
- Opens Na ion channels
What features of a reflex arc result in a response being rapid and automatic?
- Rapid- only involves 3 neurones, myelinated so salutatory conduction, few synapses- synaptic transmission is relatively slow
- Automatic- does not involve passage to brain, same pathway used each time
Explain how rod cells enable us to see in conditions of low light intensity
- Several rod cells connected to each neurone
- Causes spatial summation
Explain how cone cells enable us to distinguish between objects close together
- Each cone cell connects to a single neurone
- So no convergence
- Brain receives information from each cone cell individually
Explain how insulin controls the concentration of blood glucose by negative feedback
- Increase in blood glucose concentration causes an increase in insulin concentration
- Insulin reduces glucose back to an originsl level
- This results in a decrease in insulin level
Where does ultrafiltration occur?
Glomerulus
Give a component of the blood which is not normally present in filtrate
- Platelets
- Proteins
Explain how the cells of the proximal convoluted tubule (in the nephron) are adapted for the re absorption of glucose
- Many mitochondria provide ATP for active transport
- Many carrier proteins for active transport
- Microvilli provide a large surface area for absorption
What substances are present in the glomerular filtrate?
- Urea
- Amino acids
- Fatty acids
- Glycerol
Explain the effect on glomerular filtration rate due a large loss of blood from the body
- Filtration rate decreases
- As blood pressure decreases
Explain how a lack of insulin affects the re absorption of glucose in the kidneys of a person who does not secrete insulin
(Why urine of a diabetic contains glucose)
- Very high concentration of glucose in the blood
- So also a high concentration of glucose in filtrate
- Some glucose in the filtrate is reabsorbed into the blood by active transport
- This requires protein carriers
- These are saturated
- Not all glucose can be reabsorbed (so some glucose excreted out in urine)
Name the gland which releases ADH
Pituitary
Explain the role of the loop of Henle in the absorption of water from filtrate
- In ascending limb- Na ions actively removed into medulla
- Ascending limb is impermeable to water
- Descending limb is permeable to water- water moves out
- Low water potential in medulla
- The longer the loop the lower the water potential in medulla
- Water leaves collecting duct
- By osmosis
- Process called countercurrent multiplier
Explain the role of ADH in the production of concentrated urine
- When water potential of blood is too low- detected by receptors in hypothalamus
- Pituitary secretes more ADH
- ADH increases permeability of membrane (more aquaporins)
- More water is reabsorbed
- By osmosis
