Extensive notes tailored to the specification points for OCR 2015 (new) Spec, needed for both the AS and A2 components.
My revision from then got me an A* equivalent raw mark last year, and I received an A* at A2.
They contain as much if not more information than your textbook, in a much more c...
(a) The roles of mammalian sensory receptors in converting different types of stimuli into nerve
impulses
● To include an outline of the roles of sensory receptors (e.g. Pacinian corpuscle) in
responding to specific types of stimuli and their roles as transducers.
Sensory receptors are groups of specialised cells that detect changes in the surroundings and
convert them to neuronal signals by initiating or changing the frequency of action potentials.
They act as transducers, converting one type of energy, or a change in the magnitude of
frequency of a type of energy, and converting it to chemical, and then electrical, energy.
Some examples of sensory receptors include rods and cones in the eye, which are
photoreceptors, chemoreceptors, such as the olfactory receptors in the nose, thermoreactors in
the end-bulbs of Krause in the tongue, and vibration receptors in the cochlea of the ear.
One example of a sensory receptor is the Pacinian corpuscle, which is a mechanoreceptor—
detecting pressure and movement—found in the epidermis of the skin. It comprises a neuron
with concentric layers of connective tissue. When pressure is placed on the skin, this deforms
the layers of connective tissue, and because the membrane of the neuron contains stretch-
mediated sodium ion channel, the neuron is depolarised when the connective tissue is
deformed, generating a generator potential, which, by positive feedback, will generate an action
potential which is transmitted along neurones to the central nervous system.
(b) The structure and functions of sensory, relay and motor neurones
● To include differences between the structure and function of myelinated and non-
myelinated neurones.
● Sensory neurons carry the action potential from a sensory receptor to the central nervous
system. Sensory neurones have a long dendron carrying the action potential from a sensory
receptor to the cell body, which is position just outside the CNS. They have a short axon carrying
the action potential into the CNS.
● Relay neurons connect sensory and motor neurons, mainly in the central nervous system. They
have many short dendrites to receive impulse transmissions from a number of sensory receptors
and a short axon with variable numbers of synaptic endings to carry the action potential to the
cell bodies of motor neurones in the CNS.
● Motor neurons carry an action potential from the central nervous system to an effector such as
cells in a muscle or gland. Motor neurones have their cell body in the CNA and have a long axon
that carries the action
potential to effector
cells.
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