3.6.2 Nervous Communication Flashcards
When a neurone transmits a series of impulses, why does rate of oxygen consumption increase?
Increased rate of respiration
More energy supplies
For active transport of ions
Why does a myelinated axon conduct impulses faster than non-myelinated one?
Action potential at nodes
Myelinated axons have saltatory conduction so the Na+ ions travel forward in leaps
Action potential doesn’t have to travel whole length
Explain effect of myelination on rate of nerve impulse conduction
Myelin insulates
Saltatory conduction- nerve impulses ‘leap’ to next node of Ranvier
Describe how the number and distribution of rods and cones across retina differs in nocturnal mammals to humans
Lots more rods than cones as cones work in bright light and rods work in low light
Rods have high sensitivity
Rhodopsin bleaches at low light intensities
Why does person see image in colour when image is focused in fovea
High concentration of cone cells in fovea
Colour detected by cone cells
3 different types of cone cells (red,green,blue)
Explain why vision using fovea has high visual acuity
Each cone is connected to separate neurone
Explain why vision using other parts of the retina has high sensitivity to light
Contains rod cells Explain effect of myelination on rate of nerve impulse conduction which are photoreceptors very sensitive to light
Allow black and white vision in low light
Rhodopsin in receptors
Receptors connected to neurone
Explain what causes transmission at a synapse to occur in one direction
Neurotransmitter only in presynaptic membrane
Receptors only in post synaptic membrane
Describe the role of receptors and of the nervous system in heart rate increase during exercise
Chemoreceptors detect rise in CO2
Send impulses to medulla
More impulses to SAN
By Parasympathetic
Describe how increased carbon dioxide concentration in blood causes an increase in the heart rate
Chemoreceptors in artery/aorta detect decrease in pH
Sends electrical impulses to medulla
More nerve impulses to SAN
Explain how a resting potential is maintained across the axon membrane in a neurone
Higher concentration K+ ions inside axon/higher concentration Na+ outside axon
K+ diffuses out/Na+ diffuses in
Membrane more permeable to K+ ions
Move by active transport (sodium potassium pump)
Describe the role of mitochondria in synaptic transmission
Aerobic respiration to release ATP
Energy required for active transport of Ca2+ ions/make acetylcholine
Describe the sequence of events in the post synaptic neurone after large numbers of acetylcholine molecules have fused with the cholinergic receptors
Na+ channels open
Na+ enter by diffusion down concentration gradient
Depolarisation
Threshold reached/action potential generated
Explain why the speed of transmission of impulses is faster along a myelinated axon than along a non-myelinated axon
Myelination provides electrical insulation
Saltatory conduction
In non-myelinated depolarisation occurs along whole length of axon
