Term Definition
Resting potential The neuron is not conducting an impulse and inside of neuron has a negative
charge of -70mV compared to outside
Outline the general organisation of the nervous system
- Formed of central nervous system, brain and spinal cord
- Peripheral nervous system divided into voluntary and automatic nervous system
- Autonomic nervous system consists of sympathetic and parasympathetic nervous system
- Voluntary nervous system has motor and sensory neurons
Outline functions of motor neuron
- It carries electrical signals from the brain to effectors
- It causes muscles to contract
Draw a labelled diagram of a motor neuron
Outline movement of ions across membrane of axon
- To establish resting potential, Na-K pump pumps sodium out and potassium in through active
transport which energy is supplied to the pump as ATP
- When the potassium channel opens, it allows only K+ to diffuse out of the axon through
facilitated diffusion
- When the sodium channel opens, it allows only Na+ to diffuse into the axon through facilitated
diffusion
Explain the effect of neonicotinoid pesticides in insects synapses in the
- Neonicotinoid pesticides are similar to nicotine
- Binds to acetylcholine receptors
- Binding is irreversible
- Prevents acetylcholine binding
- Blocks transmission from CNS
Explain how nerve impulses travel along a neuron
- Resting potential of -70mV
- Na/K pump maintains the resting potential
- More sodium outside than inside, more potassium inside than outside
- Nerve impulse is an action potential that stimulates a depolarisation along the axon
- If neuron is stimulated, sodium ion channel opens
- Sodium ions diffuse in
- Na+ move in causing depolarisation
- Potassium ion channel open
- Depolarising in one area triggers depolarisation in neighbouring region
Outline the factors affecting speed of an action potential
- Diameter of axon: Larger diameter
- Myelination of axon: Myelinated sheath
- Temperature: Higher temperature
- Concentration of Na+ ions: More Na+ ions
- Number of synapses involved: Lower number of neurons
Explain how a nerve message passes from one neuron to another
- Nerve impulse reaches the end of presynaptic neuron
- Depolarisation causes calcium channels in membrane to open
- Calcium diffuses into the presynaptic neuron
- Vesicles containing neurotransmitter move to and fuse with presynaptic membrane
- Neurotransmitter released by exocytosis into synaptic cleft
- Neurotransmitter diffuses across the synapse
- Neurotransmitter attaches to receptors on postsynaptic neuron
- Receptors cause ion channels to open and sodium diffuse into the postsynaptic neuron
- The postsynaptic neuron is depolarised
- Causes a new action potential
- Neurotransmitter on postsynaptic membrane is broken down
- Neurotransmitter is reabsorbed into the presynaptic neuron
Outline the role of calcium ions in the transmission of nerve impulses
- Calcium ions diffuses into presynaptic neuron
- Causing vesicles to move to and fuse with pre synaptic membrane
- Leading to exocytosis
