Download Neuro Objectives 18

Neuro Objectives 18
1.
Adequate stimulus: the correct class of stimulus needed to generate a receptor
potential on a sensory afferent (i.e. light stimulus to “adequately stimulate” a
photoreceptor)
Transduction: translating an extracellular stimulus to an intracellular signal
Receptor potential: a graded potential generated in a sensory receptor cell
Nature of stimulus:
a.
Nature: 5 major senses, chemo-, mechano-, and photoreceptors; a
stimulus can be a combination of any of these and is not limited to these
classes.
b.
Location: Simply refers to location of receptor. Can be just about
anywhere.
c.
Intensity: There are two major ways to increase the intensity of the signal.
One is to increase the size of the graded potential given to the same size
stimulus. The other is to recruit more sensory afferent fibers (often less
sensitive fibers are already recruited, and thus, when there is a stronger
signal, the sensitive fibers fire as well as the less sensitive fibers to give a
spatial summation)
d.
Duration:
 Slowly adapting: Responds continuously to altered state (muscle
flexion, never truly adapts and is used to its state)
 Rapidly adapting: Remains stagnant and responds rapidly to change in
environment (hair cells, rapidly adapt to change in position and feeling
is lost after hair has been moved to a new position)
2.
Anatomical organization of sensory receptors: Must be able to receive a
signal, pass it to the CNS, and have mitochondria for energy production.
Long receptor: Has a long axon, and therefore produces action potentials
similarly to lower motor neurons. Only difference is source of input and output
(input is a receptor rather than from neurotransmitters, output is to CNS rather
than periphery)
Short receptor: Receptor is a small cell and therefore does not need to produce
an action potential. Thus, a receptor potential can be hyperpolarizing or
depolarizing, and the receptor potential is translated into neurotransmitter release
to a postsynaptic sensory neuron.
3.
Mechanisms used by sensory receptors and postsynaptic membranes:
a.
Similarities: Transduction; can use G-protein or gated ion channels for
transmission
b.
Differences: Sensory receptors need an adequate stimulus to generate
electrical signal whereas postsynaptic membranes use neurotransmitters
4.
Muscle spindles: Found encapsulated in intrafusal muscle fiber region that can’t
contract. When the muscle stretches, the receptors are exposed and relay
information concerning the stretching of the muscle fiber.
 Gamma motor neurons: Found encapsulated in intrafusal muscle fiber
region that can contract. Thus, CNS input through these motor neurons
can stretch the muscle and increase sensitivity to muscle stretching via the
muscle spindles.
Golgi tendon organs: Found encapsulated in myotendonous junction. GTOs are
found in between the muscle and the tendon, so when the muscle fibers flex, the
receptor is squeezed to stimulate the receptor.
5.
Roman numerals: I is big, IV is small.
Alphabet: A is fast, C is slow.
Greek letters: α, γ are motor neurons; β, δ are sensory neurons. Again, earlier in
the alphabet corresponds to faster transmission.
6.
Peripheral nerve fiber conduction velocity:
a.
Fast conducting fibers: large, heavily myelinated, most neuron fibers
b.
Slow conducting fibers: small, thinly myelinated/unmyelinated, used for
pain, temperature, and some touch