Mcb 80 - Lecture 3 Quiz Questions

Front 1

What is a reflex.

Back 1

A reflex is an automatic, unconscious, involuntary, unlearned reaction to something

Front 2

What is a muscle spindle and what is its function?

Back 2

Contain 2-8 intrafusal muscle fibers, which resemble the more numerous extrafusal fibers that make up most of the muscle; send proprioceptive information about the muscle to the central nervous system, and to respond to muscle stretching.

Front 3

What is the difference between intrafusal and extrafusal muscle fibers?

Back 3

Extrafusal muscle fibers are motor neurons innervated by alpha motor neurons; intrafusal muscle fibers are sensory neurons innervated by gamma motor neurons

Front 4

Name two types of axons that innervate muscle spindles.

Back 4

Alpha motor neurons (extrafusal); gamma motor neurons (intrafusal)

Front 5

Define receptor potential.

Back 5

An electric potential generated in sensory axons adherent to muscle fibers that have been stretched (and accordingly deformed the membrane of the sensory neurons)

Front 6

Define action potential.

Back 6

A "spike" of positive and negative ionic discharge that travels along the membrane of a cell; all-or-nothing responses generated by local potentials

Front 7

In the context of action potentials, what is the significance of threshold?

Back 7

When local potentials reach a certain threshold, they generate action potentials

Front 8

What is a motor unit?

Back 8

A motor neuron and all of the muscle fibers it innervates

Front 9

What are homonymous and hereonymous connections?

Back 9

Homonymous: stretch neurons come from the same muscle to which the motor neuron that it innervates belongs
Hereonymous connections: stretch neurons synapse with motor neurons from similar muscles or even unrelated/antagonistic muscles

Front 10

What are synergistic and antagonistic muscles?

Back 10

Synergistic muscles: have similar, mutually helpful functions
Antagonistic muscles: have different, contradicting functions

Front 11

Define “convergence” and “divergence” as they appertain to synaptic connections.

Back 11

“Convergence”: multiple sensory axons converge to innervate a single motor neuron (they synapse on the post-synaptic muscle fiber)
“Divergence”: every motor neuron branches to innervate many muscle fibers

Front 12

In the context of synaptic potentials, what is inhibition?

Back 12

To create movement, sensory neuron not only stimulates the extensor (quadriceps) motor neurons, it also inhibits (prevents) the flexor (hamstring) motor neurons from firing

Front 13

What two qualities of the receptor potential convey information abut the nature or strength of the stimulus?

Back 13

Amplitude and duration

Front 14

What two qualities of the action potential convey information about the nature or strength of the stimulus?

Back 14

Number and timing

Front 15

Both reflexes are abnormally weak (hypo-reflexic). Name three possible problems that could lead to this symptom

Back 15

Failure of muscle, spindle, or motor/sensory axon

Front 16

Both reflexes are abnormally strong (hyper–reflexic). Name a problem that could lead to this symptom.

Back 16

Failure of inhibition (usually from the brain)

Front 17

The patellar tendon reflex is convenient for your doctor, but how does it help you?

Back 17

As you walk, your knee bends with each step, stretching the tendon. The stretch reflex tightens the muscle to prevent the knee from buckling.

Front 18

What four cells participate in the patellar tendon reflex? (Be specific as possible.)

Back 18

sensory receptor of the muscles (spindle fibers), sensory neurons (afferent neurons) carry sensory information towards the central nervous system; motor neurons (efferent neurons) carry information away from the central nervous system, inhibitory interneurons, effector muscle responds

Front 19

Give three examples of transduction that occur in the patellar tendon reflex.

Back 19

1. Mechanical to electrical
2. Electrical to chemical
3. Chemical back to electrical

Front 20

The reflex is abnormally weak in one knee, but normal in the other (asymmetric). Name two problems that could lead to this symptom.

Back 20

Sensory neurons might not be relaying information to CNS; motor neurons may not be relaying information from CNS to muscles

Front 21

The reflex is abnormally strong in one knee, but normal in the other
> (asymmetric). Name a problem that could lead to this symptom.

Back 21

Failure of inhibition, so motor neurons fire without regulation

Front 22

List three ways in which polysynaptic connections modify the monosynaptic stretch reflex.

Back 22

The stretch reflex
is called monosynaptic because at its most basic form it only involves
two neurons, and one synapse between them. The sensory neuron gets the signal and makes one synapse with the motor neuron which then
causes the muscle to contract. However, there are several points
where multiple neurons impact the synapse: when many sensory neurons
have to fire at the same time to cause the motor neuron to reach
threshold (this is an example of convergence), when one sensory neuron makes an excitatory connection with one motor neuron but an inhibitory connection with the motor neuron in the antagonist muscle (this is an example of divergence), and when there is decending input from the brain that can either ramp up or (more commonly) damp down the entire
knee jerk response.

Front 23

the stretch reflex
is called monosynaptic because at its most basic form it only involves
two neurons, and one synapse between them. The sensory neuron gets
the signal and makes one synapse with the motor neuron which then
causes the muscle to contract. However, there are several points
where multiple neurons impact the synapse: when many sensory neurons
have to fire at the same time to cause the motor neuron to reach
threshold (this is an example of convergence), when one sensory neuron
makes an excitatory connection with one motor neuron but an inhibitory
connection with the motor neuron in the antagonist muscle (this is an
example of divergence), and when there is decending input from the
brain that can either ramp up or (more commonly) damp down the entire
knee jerk response.

Back 23

Potential receptor