Paper 2 Advanced Info Questions Flashcards
Describe the structure of a sensory neurone.
The cell body is located in the middle between the dendron and axon.
Describe the structure of a relay neurone.
The cell body is attached to the end of the axon and also has many short dendrites attached.
Describe the structure of a motor neurone.
The cell body is attached to the end of the axon and also has many short dendrites attached. Also has an axon terminal.
What is the role of shwann cells and myelination.
Has a myelin sheath which acts as an electrical insulator. Depolarisation only occurs at the nodes of ranvier enabling it to go alot quicker.
How do pupils dilate?
Dim light acts as a stimulus which photoreceptors detect. The information then gets sent by a sensory neurone to the CNS and then to the radial muscles in the iris by a motor neurone which then contact to dilate your pupils.
How do pupils contract?
Bright light acts as a stimulus which photoreceptors detect. The information then gets sent by a sensory neurone to the CNS and then to the circular muscles in the iris by a motor neurone which then contact to constrict your pupils.
How do effectors respond to a stimulus?
Stimulus detected by receptor cells which causes an electrical impulse to be sent along a sensory neurone to the CNS which then processes the information and then sends the impulse along a motor neurone to the effector.
Describe the role of the sodium potassium pump.
At rest, the membrane is polarized with the outside being more positive than inside, with voltage -70mv. This is created by sodium potassium pumps which moves 3Na+ outside the cell for every 2K+ that moves in which requires ATP. 1K+ also moves out via facilitated diffusion.
What happens during an action potential?
There is a stimulus that causes Na+ channels to open making inside the neurone less negative. If threshold is reached (-55mv) more Na+ channels open causing it to be depolarized. If +30mV is reached, Na+ channels close and K+ channels open restoring the resting potential making it repolarized. However, too many K+ will leave due to hyperpolarization but the K+ channels will close and resting potential will ne finally reached.
What is the purpose of the refractory period?
Allows ion channels to recover and acts as a time delay between action potentials making them discrete (separate). Also makes sure they’re unidirectional.
How is a nerve impulse transmitted between neurones?
Action potential arrives at the synaptic knob causing Ca2+ channels in presynaptic membrane to open. This causes vesicles containing neurotransmitters to fuse with the presynaptic membrane and release the neurotransmitter into the synaptic cleft via exocytosis. The neurotransmitters then bind to receptors on the postsynaptic membrane causing Na+ channels to open generating a new action potential.
How do photoreceptors convert light into an electrical impulse?
Photoreceptors detect light which is then absorbed by light-sensitive pigments. Light bleached the pigments which triggers a nerve impulse down a bipolar neurone. This is connected to an optic nerve that takes it to the brain.
How are rod cells stimulated in the light?
Light causes rhodopsin to break apart into retinal and opsin causing bleaching. This closes sodium channels therefore when they are actively transported out of the cell, they cannot diffuse back in. This makes the inside more negative than the outside causing hyperpolarization. This stops the rod cell releasing neurotransmitters therefore no inhibition of the bipolar neurone so an action potential can be sent along it and thus along the optic nerve to the brain.
How does IAA work?
IAA is an auxin that is in the tip of shoots. When entering the nucleus, it regulates transcription of genes related to cell elongation and growth.
What is the role of phytochromes?
Phytochromes are molecules that absorb light. They exist as Pr and Pfr. Pr is converted into Pfr when exposed to red light (daytime) and Pfr is converted into Pr when exposed to far red light (nighttime).
