test #3 Flashcards
(228 cards)
Paramecium
is a single cell protist (no nervous system).
what happens when when the cell (paramecium) hits an obstacle?
Ca2+ channels mechanically open
The depolarization of the cell then causes what to occur in the cillia?
a reversal in the beating of the cilia the cell retracts.
What happens in order to return cilliary beating to its original direction?
Ca2+ is then pumped out
Reflex
the involuntary movement of skeletal muscles.
Monosynaptic reflex:
requires only two types of neurons
muscle stretch reflex regulates what?
the amount of tension in the muscles of the antagonistic pair that maintains body posture
What does the 1a-afferent neuron do?
receives and relays the stretch signal to the spinal A-motor neuron.
What does the spinal a-motor neuron do?
induces response (quadriceps contraction)
The patellar tendon reflex:
if the muscle is stretched by a mild weight, the 1a-afferent neuron signals the a-motor neuron to induce muscle contraction.
If the loop(neuron, reflex circuit) is interrupted by cutting the afferent neuron what happens?
No response
Muscle spindle
a small group of stretch-sensitive intrafusal fibers (non-muscle fiber cells)
The Muscle spindle is innervated by
1a-afferent neurons
The muscle spindle does not contribute to what?
muscle tension
Extrafusal fibers
muscle fibers
Other components of the neuronal circuit inhibit the activity of the motor neuron to:
prevent the muscle from contracting when the other muscle in the antagonistic pair contracts establish limits to how excited the motor neuron can become
CNS interneurons can modify what?
spinal activity
Divergent axons from motor neurons send excitatory signals to the
interneurons that inhibit them
inhibitory interneurons (Renshaw cells) can also be activated by
second motor neurons
the circuit limits the excitation of
motor neurons
if neurotransmitters from Renshaw cells are blocked with strychnine (a toxin) what happens?
no control of motor neuron activity
What is Strychnine?
a toxic alkaloid from the seeds of Strychnos nux-vomica.
What do Phasic and tonic stretch receptor neurons innervate
the motor neurons of the abdominal muscles of the crayfish and respond to the stretching of the muscles.
stretch receptors react to muscle stretching by doing what?
sending excitatory signals to the motor neurons to make the muscle contract










