Viva Neurophysiology Flashcards
What are the parts of brainstem?
- Midbrain
- Pons
- Medulla oblongata
Classify the neurons
Neurons are classified by three different methods: • Depending upon number of poles: – Unipolar neurons – Bipolar neurons – Multipolar neurons. • Depending upon the function: – Motor neurons – Sensory neurons. • Depending upon length of axon: – Golgi type I neurons – Golgi type II neurons
Name the nerve fibers conducting the
impulse with maximum and minimum
velocity.
Type A alpha nerve fibers conduct the impulse with maximum velocity (70 to 120 meters/second). Type C fibers conduct the impulse with minimum velocity (0.5 to 2 meters/second).
What are the two types of potentials
noticed in nerve fibers?
• Action potential (nerve impulse) – produced when the nerve is stimulated with adequate strength of stimulus (threshold or minimal stimulus). It is propagated and nongraded. • Electrotonic potential or local response – is produced when the strength of stimulus is not adequate (subthreshold or subminimal stimulus). It is nonpropagated and graded.
Differentiate between EPSP and AP
What are the properties of generator
potential?
The properties of GP are:
• It is non-propagatory in nature
• It is monophasic
• It does not obey all or none law.
What do you mean by spatial and
temporal summation?
• Simultaneous stimulation of two afferent nerves by a stimulus of subthreshold intensity can evoke action potential in motor neuron. This property is known as spatial summation. • Whereas if subminimal stimuli are repeated at short intervals in a single nerve, reflex action can also be evoked which is known as temporal summation
What is the fractionation phenomenon?
Direct stimulation of motor nerve results in
more response than reflex response or in
other words the tension developed reflexly
is always a fraction of response that is
produced by direct motor nerve stimulation.
This is known as fractionation phenomenon.
What is afterdischarge?
Continuation of discharge of impulses from
motor neuron even after withdrawal of
stimulation from sensory side is called
as afterdischarge.
What do you mean by law of forward
conduction?
Synapse permits the conduction of impulse
from presynaptic to postsynaptic neuron
only, i.e. unidirectionally. This property is
known as law of forward conduction
ame the receptors responsible for
following sensations—touch, pressure,
hot, cold and pain
• Touch—Markel’s disc or Meissner’s corpuscle • Pressure—Pacinian corpuscle • Hot—Ruffini’s end organs • Cold—Krause’s end bulb • Pain—Free nerve endings.
Name the properties of action
potential.
- Propagative
- Biphasic
- All or none law
- No summation
- Refractory period.
What is saltatory conduction?
In a myelinated nerve fiber, the action
potential (nerve impulse) jumps from one
node of Ranvier to another node of Ranvier,
making the velocity of conduction faster.
This type of conduction in a myelinated
nerve fiber is called saltatory conduction.
Explain the mechanism of saltatory
conduction briefly.
Myelin sheath is not permeable to ions. So
during the conduction of action potential,
the entry of sodium ions from extracellular
fluid into nerve fiber occurs only at the node
of Ranvier, where the myelin sheath is
absent. This causes depolarization only in
successive node and not in internode. So,
the action potential jumps from one node
to another. Hence, it is called saltatory
conduction (saltare = jumping).
Why is the nerve fiber not fatigued
Nerve fiber is not fatigued because it can
conduct only one action potential at a time.
At that time it is completely refractory and
cannot conduct another action potential
What are the changes, which take
place in nerve cell body during degeneration of nerve fiber?
• The Nissl granules disintegrate by chromatolysis • Golgi apparatus also disintegrates • Cell body swells due to accumulation of fluid and becomes round • Neurofibrils disappear • Nucleus is displaced towards the periphery. In extreme conditions, nucleus is extruded out of the cell. Figure 17.2 illustrates the degeneration and regeneration of a nerve fiber.
What is Wallerian degeneration?
What is Wallerian degeneration? Degenerative change in the distal cut end of the nerve fiber is called Wallerian degeneration. Q.37 Explain the changes during Wallerian degeneration briefly. • Axis cylinder swells and breaks up into small pieces. After few days, the debris is seen in the space that was occupied by the axis cylinder • Myelin sheath disintegrates into fat droplets • Neurilemmal sheath is not affected but the cells of Schwann multiply rapidly. The macrophages invade from outside and remove the debris of axis cylinder and fat droplets. So neurilemmal tube becomes empty and it is filled with cytoplasm of Schwann cell.
Degeneration of nerve fiber
What is retrograde degeneration?
The degenerative change that occurs at the
proximal cut end of the nerve fiber is called
retrograde degeneration.
Q.39 What is transneuronal degeneration?
If an afferent nerve fiber is cut, the
degeneration occurs in the neuron with
which the afferent nerve fiber synapses. This
is called transneuronal degeneration.
Define and classify receptors
Define receptor. Receptor is an afferent nerve terminal, which receives the stimulus. It is defined as the biological transducer that converts various forms of energy, i.e. stimulus into action potential in nerve fiber. 46.Classify receptors. • Exteroceptors: – Cutaneous receptors – Chemoreceptors • Interoceptors: – Telereceptors. – Visceroreceptors – Proprioceptors.
What are the cutaneous receptors or
mechanical receptors?
Receptors situated in the skin are called
cutaneous receptors. The different cutaneous
receptors (Fig. 17.4):
• Touch receptors – Meissner’s corpuscle
and Merkel’s disc
• Pressure receptors – Pacinian corpuscle
• Temperature or thermoreceptors –
Krause’s end organ for cold and Raffini’s
end organ for warm
• Pain receptors or nociceptors – free
(naked) nerve ending
What are chemoreceptors, which
belong to the group of exteroceptors
Receptors giving response to chemical
stimuli are known as chemoreceptors. The
chemoreceptors, which belong to the group
of exteroceptors are taste receptors in taste
buds and olfactory receptors for smell in the
nose
What are telereceptors?
The receptors, which give response to
stimuli arising away from the body are
called telereceptors. Telereceptors are:
• Hair cells of organ of Corti in the ear for
hearing
• Rods and cones of retina in the eye for
vision.
