Lucas part 6

Question 1

3 components of the CNS

Answer 1

Motor cortex, cellebrum, spinal cord

Question 2

4 main purposes of skeletal muscle control systems

Answer 2

Voluntary Motion
Coordination of Multiple Muscles
Graded Force Levels (adjust contraction intensity)
Automatic Systems (reflexes)

Question 3

which part of the CNS controls voluntary motion

Answer 3

motor cortex

Question 4

what does the cerebellum do

Answer 4

coordinate timing and accuracy of complex movements

Question 5

what does the spinal cord do in the CNS

Answer 5

Houses central pattern generators for rhythmic activities like walking, and reflex arcs for automatic responses

Question 6

whats the order that leads to a motor output

Answer 6

stimuli - sensory neuron - interneuorn - motor neuron - muscle

Question 7

Signals from the ____travel down to motor neurons in the spinal cord.

Answer 7

motor cortex

Question 8

____ motor neurons directly control muscle contraction.

Answer 8

alpha

Question 9

____ lets us modulate the level of force produced by a muscle

Answer 9

modulate

Question 10

____ levels of force are achieved through ____

Answer 10

graded, summation

Question 11

temporal vs spatial summation

Answer 11

temporal: single presynaptic neuron sends signals to a postsynaptic neuron at a rapid rate, the signals add up.

spatial:** multiple** presynaptic neurons send signals to a postsynaptic neuron at the same time, the signals add up

Question 12

Small motor units involve =
Large motor units involve =

Answer 12

fine control (e.g., fingers).
strong force (e.g., thighs).

Question 13

Problem: Too many motor units (thousands) for the brain to control individually.

Solution: ?

Answer 13

Solution: Recruitment based on the size principle

Question 14

small alpha neurons are used for:

Answer 14

SO fibres, slow endurance tasks

Question 15

big alpha neurons are for:

Answer 15

FG fibres, powerful, short bursts.

Question 16

which motor neurons require more or less ESPS to fir

Answer 16

small: require less epsps to fire
large: require more esps to fire

Question 17

what do you do on alpha motor neurons to recruit faster fibers

Answer 17

Increase stimulation rate of brain

Question 18

3 type of reflex arcs

Answer 18

Withdrawal (Flexor) Reflex
Crossed-Extensor Reflex
Stretch (Myotactic) Reflex

Question 19

what is the purpose of the Withdrawal (Flexor) Reflex

Answer 19

Pull a limb back in response to pain.

Question 20

purpose of the Crossed-Extensor Reflex

Answer 20

Maintain balance when one limb is withdrawn.

Question 21

purpose of Stretch (Myotactic) Reflex

Answer 21

Maintain Posture: Keeps muscles at a baseline level of tension (muscle tone).
Prevent Overstretching: Protects muscles from being stretched too far, potentially causing damage.
Stabilize Joints: Ensures smooth and coordinated movements by regulating muscle length.

Question 22

explain the withdrawal reflex steps

Answer 22

sensory receptor detects pain
action potential travels from sensory to spinal cord
interneuron communication
INI is excited, stimulates 1.1 (flexor/hamstring) - pull limb away
1.2 excites 1N2 to stimulate extensor (quadriceps) - smooth movement

Question 23

what is reciprocal innervation

Answer 23

prevents the muscles from working against each other.

Flexor Muscle: Activated (contracts to pull the limb away).
Extensor Muscle: Inhibited (relaxes to allow smooth withdrawal)

Question 24

Why Does the Reflex Bypass the Brain?

Answer 24

If you waited for your brain to process the pain, you might not withdraw your foot quickly enough to prevent further injury.
a signal is also sent to the brain so you become aware of the pain (but this happens after the reflex action).

Question 25

steps of the cross extensor reflex

Answer 25

finish the withdrawal reflex first, then with reciprocal innervation, (pained limb - withdrawal)
branch 1.3 excites 1N3 interneuron
1N3 in standing limb, 3.1 excites extensor (quads), 3.2 excites flexor inhibited (hamstring)

so 1.3 - 1N3 - 3.1 - 3.2 - 1N4

Question 26

Neural tone refers to the

Answer 26

baseline level of activity in alpha motor neurons.

Question 27

Increase Tone:

Answer 27

More frequent APs, resulting in stronger muscle contractions.

Question 28

Decrease Tone

Answer 28

Fewer APs, resulting in less contraction.

Question 29

Where Would You Find Large Motor Units?

Answer 29

Found in muscles requiring strong force (e.g., quadriceps).

Question 30

Small Motor Units:

Answer 30

Found in muscles requiring fine control (e.g., eye muscles).

Question 31

speed of less tone, default, and more tone:

Answer 31

less: slower
more: faster

Question 32

____ tighten the ends of the muscle spindles, maintaining their sensitivity even when the muscle is contracted.

Answer 32

gamma motor neurons

Question 33

which reflex involves only Involves only one synapse between the sensory neuron and motor neuron, making it fast.

Answer 33

myotactic reflex

Question 34

example of myotactic reflex

Answer 34

A tap on the patellar tendon stretches the quadriceps muscle.
Muscle spindles in the quadriceps detect the stretch and send signals via sensory neurons to the spinal cord.
The sensory neurons:
Activate alpha motor neurons, causing the quadriceps to contract (knee extends).
Inhibit the hamstring muscles (antagonists) to ensure smooth movement.
The result is the familiar “knee jerk” motion.

Question 35

steps of myotactic reflex

Answer 35

Muscle Stretch:

A sudden stretch of a muscle (e.g., due to a tap on a tendon) activates muscle spindles.
Example: The patellar reflex when the patellar tendon is tapped during a knee-jerk test.
Sensory Neuron Activation:

The stretch-sensitive neurons (Ia afferent fibers) wrapped around the muscle spindles detect the stretch.
These neurons fire action potentials and send the signal to the spinal cord.
Integration in the Spinal Cord:

The sensory neurons synapse directly onto alpha motor neurons of the same muscle (a monosynaptic reflex).
This is the simplest reflex arc, involving only one synapse between the sensory and motor neurons.
Motor Neuron Activation:

The alpha motor neurons send signals back to the muscle, causing it to contract.
This contraction resists the initial stretch and restores the muscle to its original length.
Inhibition of Antagonist Muscles:

At the same time, interneurons in the spinal cord inhibit the alpha motor neurons of the antagonist muscle.
This ensures smooth contraction of the stretched muscle without resistance from its opposing muscle (reciprocal inhibition).

Question 36

in terms of stimulation rate, what is the order from lowest to highest fibres

Answer 36

SO, FOG, FG