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OCR Biology A level 5.1.3 Neuronal Communication summary notes
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Summary notes for topic 5.1.3 Neuronal communication of OCR Biology A level Module 5. Detailed electronic notes with diagrams.
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The amount that each component in the sample adsorbs to the stationary phase is different Each component takes a different amount of time from being injected into the tube to being recorded at the
other end
RETENTION TIME: used to identify component
At the end of the tube is a detector - connected to a recorder which gives a peak that shows retention time.
Area under each peak (or height for sharp peaks) tells you the relative amount of each component
Mass spectrometry
Mass spectrometry is an analytical tool used for measuring the molecular mass of a sample and to obtain structural
information. Shows us the masses of the ions detected and their relative abundance- i.e. the isotopic composition of
an element.
5 steps:
Vaporisation: the element is turned into a gas using an electrical heater and as a result of the high vacuum
Ionisation: the gas is bombarded with high energy electrons which knocks electrons off the atoms, forming
positive ions.
Acceleration: the positive ions are then accelerated by an electric field.
Deflection: the positive ions’ paths are deflected with a magnetic field. Lighter ions are deflected more than
heavier ions with the same charge. Charge has a similar effect to mass. Uncharged atoms won’t be detected.
Detection: Ions of a specific mass/charge reach the detector. The magnetic field strength is slowly increased
so that ions of increasing mass are detected, generating a mass spectrum.
Fragmentation pattern tells you about the structure of a compound. The parent ion breaks up into smaller ions
which are also detected.
o Ions break up to ion + radical
o Radicals lost
5.1.3 Neuronal Communication
Sensory receptors are energy transducers that convert one form of energy to another
Each type of transducer is adapted to detect changes in a particular form of energy
Each change in energy levels in the environment is called a stimulus
Whatever the stimulus, the sensory receptors convert the energy into electrical energy
e.g Rods/cones convert light
Olfactory cells convert chemical potential
Sound receptors convert sound
, Sensory neurones carry
action potentials from a
sensory receptor to the
central nervous system
The cell body is situated
just outside the CNS
Motor neurone
carry an action
potential from
the CNS to an
effector such
as a muscle or
gland
The cell body is
inside the CNS
Differences:
Cell body not in CNS/in CNS
Cell body not at end/at end of neurone
Dendrites at end of dendron and axon/Dendrites connect direcly to cell body
Shorter axon/Longer axon
Dendron present/No dendron
Starts at sensory receptor/Ends at motor plate
How is how the resting potential is established and maintained;
Sodium/potassium pump
Pumps 3 Na+ ions out (of neurone)
Pumps 2K+ ions in
By active transport
Using ATP
K+ diffuse back out of cell
Membrane less permeable to Na+
As voltage gated Na+ channels are closed
Large number of anions inside cell cytoplasm
Cell membrane polarised
About -60mV
How is the action potential is generated;
Sodium ion channels open
Na+ ions diffuse toward negative region
inside cell
Move down an electrochemical gradient
Positive ions make the cell less negative
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