Lecture 12 study guide ( anatomy )

Question 1

Define motor units

Answer 1

A motor unit consists of one motor
neuron and all muscle fibers it
innervates

Question 2

What’s the difference between small and large motor units? and how do they effect the level of motor control?

Answer 2

• Fine control muscles (e.g.,
  fingers, eyes) have small
  motor units.
• Large, weight-bearing
  muscles (e.g., hips) have
  large motor units.

Question 3

activities that require fine motor control

Answer 3

eye movement

Question 4

activities that require gross motor control

Answer 4

walking, running, skipping, as well as playground skills (e.g. climbing) and sporting skills (e.g. catching, throwing and hitting a ball with a bat).

Question 5

Latent period:Describe the events that occur during this initial period following stimulus application.

Answer 5

The time between the activation of a motor neuron until the muscle contraction occurs

Question 6

Contraction Period: Explain the processes occurring as muscle tension
increases.

Answer 6

Active cross bridges; tension
rises.

Question 7

Relaxation Period: Discuss the processes involved as muscle tension
decreases and why this phase is important for muscle recovery.

Answer 7

Calcium pumped back into
the SR; tension decreases to
zero

Question 8

Temporal Summation: Describe how multiple stimuli in quick succession
influence muscle force.

Answer 8

Twitch force increases
* Additional Ca2+ gets released

Question 9

Unfused Tetanus: Define this form of contraction and its physiological
implications.

Answer 9

• Increased stimuli frequency
• Muscle tension is near maximum
• Sustained, quivering contraction

Question 10

Fused Tetanus: Explain how sustained high-frequency stimulation leads to a
steady, maximal contraction.

Answer 10

• Maximum muscle tension
• Contractions “fuse” into one
• Prolonged contraction leads to
  fatigue

Question 11

Describe the role of stimulus frequency and strength of stimulus in determining muscle
force production.

Answer 11

With the increase in the stimulus frequency, there is an increase in muscle size and force.

Question 12

Explain how variations in stimulus frequency and strength contribute to changes in muscle tension.

Answer 12

If the frequency of motor neuron signaling increases, summation and subsequent muscle tension in the motor unit continues to rise until it reaches a peak point.

Question 13

Creatine-Phosphate System: Explain how this pathway supports short, intense bursts of activity.

Answer 13

Creatine phosphate donates its
phosphate to ADP
* Via creatine kinase
* Muscles have enough ATP and CP
reserves to last about 15 seconds

Question 14

Anaerobic Glycolysis: Discuss when this pathway is used and its role in muscle metabolism.

Answer 14

Glucose broken into 2 pyruvic acid
– Pyruvic acid converts to lactic acid
– Doesn’t require oxygen
– Quickly produces 2 ATP molecules

Question 15

Aerobic Glycolysis & Oxidative Phosphorylation: Describe how these
processes provide energy for endurance activities.

Answer 15

quickly produces two ATP molecules It is used during high-intensity, sustained, isometric muscle activity.

Question 16

Define muscle tone and explain its importance in maintaining posture and stabilizing joints.

Answer 16

• Slight contraction of relaxed
  muscles due to spinal reflexes.
  Functions:
• Maintains muscle firmness,
  stabilizes joints, and supports
  posture.

Question 17

Discuss the physiological basis for muscle tone and how it contributes to overall muscle function.

Answer 17

It helps to maintain posture and declines during REM sleep.

Question 18

Isotonic Contractions: Describe how muscle length changes during isotonic
contractions and provide examples.

Answer 18

1) Concentric contractions
– Muscle shortens against a load
– I.E. Biceps contract to pick up
backpack
2) Eccentric contractions
– Muscle lengthens against a
load
– I.E. Laying the backpack down,
causing the biceps to lengthen
while generating a force

Question 19

Isometric Contractions: Explain the nature of isometric contractions and their functional roles

Answer 19

Muscle length stays the same
* Cross-bridges generate force
* Actin filaments do not shorten
* Load is greater than maximum
muscle tension

Question 20

Identify the primary factors that contribute to muscle fatigue, including metabolic, neural, and mechanical influences.

Answer 20

• Ionic/pH imbalances (I.E., Ca2+,Na+, H+, K+)
• Increased inorganic phosphate (Pi)
• Decreased ATP and increased magnesium (Mg2+)
• Decreased glycogen
• Lactate does not significantly change pHduring exercise.

Question 21

Explain how each of these factors pf muscle fatigue limits muscle
performance and endurance

Answer 21

the force behind the muscles’ movements decrease, causing you to feel weaker

Question 22

Compare and contrast the contraction mechanisms of smooth muscle and skeletal muscle.

Answer 22

smooth muscle contracts very slowly, develops high force/cross-sectional area and maintains force for long periods of time with low use of ATP

Question 23

Highlight the structural and functional differences, as well as the unique control mechanisms that distinguish smooth and skeletal muscle

Answer 23

Smooth muscle differs from skeletal muscle in function. Unlike skeletal muscle, smooth muscle is capable of maintaining tone for extended periods and often contracts involuntarily. At a cellular level, smooth muscle can be described as an involuntary, non-striated muscle.