Skeletal Muscle, Cardiac Muscle and Movement - Topic 1

Question 1

Motor Unit

Answer 1

One alpha motor neuron and all muscle fibres/ cells associated with it.

Question 2

What do neurotransmitters do and how are they transmitted?

Answer 2

Initiate nerve impulses and they are transmitted by electrical signal.

Question 3

Skeletal Muscle

Answer 3

Muscle type activated by motor neurons.

Question 4

What way are skeletal muscles arrnged and what direction do they contract?

Answer 4

They are arranged lengthwise and contract horizontally.

Question 5

Neuromuscular Junction

Answer 5

Synapse between motor neuron and muscle fibre where electrical signal is relayed into mechanical action by the muscle

Question 6

Princliples of muscle contraction

Answer 6

1. Alpha motor neurons activates bundle of muscle cells (motor unit)
2. Each muscle cell produces an equal amount of force
3. The no. alpha neurons activated contribute to the force produced by motor units
4. So the relative force gained by muscle contraction is dependent on the number of motor units activated.

Question 7

Gap between motor neuron post synapse and muscle cell

Answer 7

Neuromuscular junction

Question 8

Why do muscle cells produce an equal amount of force?

Answer 8

Because they are very thin and long and approx. the same length so the overlapping of actin and myosin is equal on each one (equal contraction).

Question 9

Muscle Twitch

Answer 9

Single muscle contraction followed by relaxation.

Question 10

What is needed for another muscle contraction or even a twitch to occur?

Answer 10

The previous contraction must relax. (Repolarisation - action potential must not be reached so Voltage needs to be below threshold)

Question 11

What controls fine movement, e.g. eye?

Answer 11

Many motor neurons associated with the same mucle cells

Question 12

Summation

Answer 12

Increased force from multiple muscle twitches in short enough intervals.

Question 13

Tetanus

Answer 13

Sustained muscle contraction from very rapid/continual stimuli.

Question 14

How can one motor nueron cause tetanus?

Answer 14

It can release Ca2+ multiple times, causing repeated stimulation required for tetanus to occur.

Question 15

What happens when the intervals between stimuli are short? How does it gettig shorter change the contraction of muscle?

Answer 15

The action potential generated in the previous contraction (e.g a twitch) cannot go below the threshold so the next contraction is stronger (summation). This eventually creates incomplete tetanus and then tetanus when stimuli is continuous and at maximal strength.

Question 16

What is the difference between summation and tetanus?

Answer 16

Summation = series of stimuli added produce a stronger contraction because the muslc eis stimulated before it has fully relaxed from a previous twitch. The second twitch is stronger

Ttanus = contractions fuse, producing continuous contraction without relaxation in between. When stimuli are repeated so frequently that there is no noticeable relaxation phase between twitches.

Question 17

Alpha Motor Neuron

Answer 17

Neuron that stimulates skeletal muscle contraction.

Question 18

Graded Response

Answer 18

Variable muscle force based on motor unit activation.

Question 19

Muscle Fatigue

Answer 19

Decreased muscle performance after prolonged activity.

Question 20

Electrical Impulse

Answer 20

Signal from the brain to initiate muscle contraction.

Question 21

Stimulus Intensity

Answer 21

Magnitude of signal affecting muscle tension.

Question 22

Twitch Force

Answer 22

Force generated by a single muscle twitch.

Question 23

Skeletal Muscle Activation

Answer 23

Process of stimulating muscle fibers to contract.

Question 24

Muscle Cell Arrangement

Answer 24

Skeletal muscle cells are horizontally bundled.

Question 25

Force Production

Answer 25

Dependent on number of activated motor units.

Question 26

Threshold Level

Answer 26

Minimum force required for muscle contraction.

Question 27

Twin Pulse Interval

Answer 27

Time between two stimuli affecting muscle response.

Question 28

Short Intervals

Answer 28

Time gaps between stimuli impacting contraction strength.

Question 29

Incomplete Tetanus

Answer 29

Partial relaxation between rapid stimuli.

Question 30

Muscle Response

Answer 30

Reaction of muscle fibers to stimulation.

Question 31

Force Doubling

Answer 31

Increased contraction force with closely spaced stimuli.

Question 32

Electrical Stimulation Frequency

Answer 32

Rate of stimuli affecting muscle contraction dynamics.

Question 33

Muscle Contraction Decision

Answer 33

Brain determines number of activated muscle cells.

Question 34

Muscle Fiber Innervation

Answer 34

Each fiber receives input from one motor neuron, causing it to contract.

Question 35

Twitch

Answer 35

Single muscle contraction followed by relaxation.

Question 36

Recruitment

Answer 36

Activation of multiple motor units for greater force.

Question 37

Motor Units

Answer 37

Alpha motor neuron and its innervated muscle fibers.

Question 38

What are the two modes of skeletal muscle activation?

Answer 38

Recruitment of multiple motor units (TENSION) and Frequency of stimuli (STIMULUS VOLTAGE)

Question 39

Recruitment of multiple motor units

Answer 39

The amount of force generated when skeletal muscle contracts is dependent on the number of activated motor neurons collaorated.

Question 40

Number of motor units for muscles for delicate movement vs muscles for strength

Answer 40

Delicate movement have less motor units (less muscles less per motor neuron)

Question 41

Frequency of Stimulation

Answer 41

Sustained skeletal muscle contraction by the same motor neuron

Question 42

Fast Twitch Units

Answer 42

Muscle fibers that contract quickly and powerfully.

Question 43

Slow Twitch Units

Answer 43

Muscle fibers that contract slowly and endurance-focused.

Question 44

Cardiac Muscle

Answer 44

Muscle tissue that makes up the heart.

Question 45

Arrangement of Cardiac Muscle Cells

Answer 45

Tandemly (not horizontally) arranged - they contract independently in sequence.

Question 46

Intercalated Discs

Answer 46

Separation wall between two neighbouring cardiac muscle cells with holes that allow communication between cardiac cells (signalling molecules). They insulate a signal so it doesn’t get lost between the cells.

Question 47

Sino Atrial (SA) Node

Answer 47

Pacemaker of the heart initiating contraction signals.

Question 48

Autorhythmic Cells

Answer 48

Cells generating spontaneous action potentials in heart.

Question 49

Contractile Cells

Answer 49

Cells responsible for heart muscle contraction. They contract when a signal from the neighbouring cell is transported through the insulated wall of intercalated disc.

Question 50

Difference between cardiac and skeletal muscle activation.

Answer 50

Skeletal muscle is only activated by a motor neuron and contractile cardiac muscle cell is activated by neighbouring cell through an intercalated disc AND internal pacemaker.

Question 51

Action Potentials

Answer 51

Electrical signals triggering muscle cell contraction - rapid change in the voltage across a cell membrane, caused by a shift in the balance of ions inside and outside the cell

Question 52

Gap Junctions

Answer 52

Connections allowing electrical signals between cells.

Question 53

Horizontal Contraction

Answer 53

Skeletal muscle cells contract in a coordinated manner.

Question 54

Sequential Contraction

Answer 54

Cardiac muscle cells contract one after another and pulled to the direction the signal travels from.

Question 55

Unidirectional Signal Travel

Answer 55

Signal flows in one direction through cardiac cells.

Question 56

Autorythmic Muscle Cells

Answer 56

Muscle cells that function independently of nervous input.

Question 57

Muscle Relaxation

Answer 57

Return of muscle fibers to resting state.

Question 58

Maximum Force in Tetanus

Answer 58

Peak tension achieved during sustained contraction.