Neurons Flashcards
Outline the general organization of the nervous system.
4 marks
formed of central nervous system
brain and spinal cord
peripheral nervous system divided into **voluntary **and **autonomic **nervous systems
autonomic nervous system consists of sympathetic and parasympathetic nervous system
voluntary nervous system has motor and sensory neurons
Draw a diagram to show the structure of a motor neuron.
5 marks
cell body drawn and labelled with a nucleus shown inside (reject if cell body not drawn at end of axon)
axon drawn at least three times as long as the diameter of the cell body and labelled
Schwann cells / mylin sheath drawn and labelled
gaps in the myelin sheath drawn and labeled
at least five dendrites drawn leading to the cell body labelled
at least two motor end plates / boutons / synaptic knobs / synaptic terminals drawn and labelled
Outline the changes that lead to the depolarization of an axon as an action potential travels along a neuron.
5 marks
local currents / ions diffuse from adjacent depolarised section of axon
resting / membrane potential reduced
voltage-gated ion channels affected
sodium channels open
sodium diffuses in / moves in rapidly
therefore fewer positive charges outside and more inside / inside becomes positive relative to outside / membrane polarity reversed
before depolarisation outside was positive relative to inside
when some sodium gates open entry of Na+ causes more sodium gates to open
membrane potential rises from -70mV to +30 mV
Explain how the nerve impulse passes along a neuron.
8 marks
in resting potential
sodium is pumped out by the active transport and potassium in
a concentration gradient builds up electrical potential / voltage
negative inside compared to outside
in action potential
must pass threshold level
sodium channels open and ions diffuse into neuron
membrane depolarized
potassium diffuse out across membrane through ion channels
active transport of ions once more
slower in un-myelinated neuron than in myelinated
an action potential in one part of the neuron causes the action potential to develop in the next section self-propagating signal
Explain how a non-mylenated neuron can maintain a resting potential and undergo an action potential.
9 marks
resting potential is a charge difference across the membrane / -70mV
inside negative compared to the outside
active transport of ions across the membrane / pumps using ATP
positively charged sodium ions / Na2 are pumped out
fewer K+ are pumped in / 2 K+ compared to 3 Na+
neurone contains negatively charged organic ions
membrane allows little / no diffusion of ions
to create action potential sodium ion channels open
sodium ions move into the neurone
therefore there is depolarisation / membrane polarisation is reversed
this causes similar changes further on along the neurone
reference to diffusion of ions / local currents
potassium ion channels open after the sodium ion channels
potassium diffuses out causing some repolarization
Explain the process of synaptic transmission.
7 marks
presynaptic neurons pass stimulus / potential to postsynaptic neurons
presynaptic neuron releases neurotransmitter into synaptic cleft
process involves exocytosis
exocytosis requires Ca+2 entry into presynaptic neuron
neurotransmitter binds with postsynaptic membrane receptor
neurotransmitter binding can cause postsynaptic membrane ion channel to open / increase / change permeability of post-synaptic membrane
increase / change permeability of post-synatic membrane
open channel allows specific ions to enter / exit post-synaptic membrane
depolarization / hyperpolarization can result in / initiate action potential
outcome depends on type of postsynaptic receptor and type of channel opened ; reference to excitatory and inhibitory synapses
Na+ passing to the inside of the post-synaptic neuron (usually) causes depolarization
Cl- passing to the outside of the post-synaptic neuron (usually) causes hyperpolarization
(some) neurotransmitters are destroyed by enzymes
