Physiology

Question 1

Explain what a motor unit is

Answer 1

A single alpha motor neuron and the muscle fibres that it innervates

Question 2

What is a muscle fibre?

How big is it?

Answer 2

1 muscle cell

Typically the full length of the muscle

Question 3

What is the neurotransmitter at the neuromuscular junction?

Answer 3

ACh

Question 4

What 2 things are needed for muscle contraction?

Answer 4

Ca2+

ATP

Question 5

Where does skeletal muscle get its Ca2+ from?

Answer 5

SR only

Ca2+ is released from lateral sacs as action potential spreads down transverse (T)-tubules

(look at diagram in notes)

Question 6

Explain how rigor mortis takes place?

Answer 6

Muscles need ATP in order to contract and RELAX

Without ATP muscles continually seize

Question 7

What is the smallest functional unit in skeletal muscle?

Answer 7

Sacromere

Functional unit = ability to carry out full function of cell

Question 8

Draw and label a sacromere:
A band
H zone
M line
I band

Answer 8

A band - area of actin and myosin that overlaps

H zone - central area of myosin with no overlap of actin

I band - peripheral areas of actin with no myosin underneath

M line - central part of myosin

Question 9

What has more muscle fibres per motor unit - intricate muscles or large powerful muscles?

Answer 9

Intricate muscles - fine movement requires more motor units per muscle fibres

Question 10

What 2 things is the gradation of muscle contraction dependant on?

Answer 10

• No of motor units stimulated (motor unit recruitment)

- Summation of contractions + length of fibre

Question 11

Explain how tetanus can become a thing in skeletal muscle

Answer 11

In skeletal muscle action potentials are much smaller than contractions
Hence multiple action potentials can occur and enable constant contraction of muscle

Question 12

What prevents cardiac muscle from becoming tetanised?

Answer 12

Long refractory period

Question 13

What is optimum length of muscle?

Answer 13

The optimum overlap of actin and myosin that allows for maximum tetanic tension

Question 14

What are the 2 types of skeletal muscle contraction - describe them both?

Answer 14

Isotonic - length changes and tension stays the same
Isometric - length stays same and tension changes

Met = police = rising tension

Question 15

How is muscle contraction in sarcomeres communicated to the bones of the body?

Answer 15

Via the elastic component of muscle e.g. tendons/connective tissue

Question 16

What impact does increased load have on velocity of muscle contraction?

Answer 16

Increased load decreases velocity of contraction

think if holding something v heavy on fingers it would take more time to scrunch up hand

Question 17

Describe how each of the following types of fibres get their energy:
Type I
Type IIa
Type IIx

Answer 17

Type I - slow twitch - aerobic
Type IIa - intermediate-twitch - aerobic and anaerobic
Type IIx - fast twitch - anaerobic

Question 18

What pathways are involved in providing immediate energy to muscle cells and energy in oxygenated and deoxygenated situations

Answer 18

Immediate - transfer of creatine phosphate to ADP = ATP
Oxygenated - oxidative phosphorylation
Deoxygenated - glycolysis

Question 19

What is a stretch reflex?

Answer 19

Sterotyped response to a specific stimulus

Question 20

Stretching of the muscle results in firing of what kind of neurons

Answer 20

Afferent neurons

Question 21

What are muscle spindles also known as and what are the sensory nerve endings found within them called?

Where are they found?

Answer 21

Intrafusal fibres - in the belly of the muscle

Annulospiral fibres

Question 22

What motor neurons supply the intrafusal fibres (muscle spindles)?

What is the role?

Answer 22

Gamma motor neurons

Maintain sensitivity of intrafusal muscle fibres to stretch

Question 23

What are nociceptors?

What are noxious stimuli?

Answer 23

1st order neurons

Afferent neurons activated NORMALLY by noxious stimuli

Thermal, mechanical and chemical

Question 24

What are the 2 types of nociceptors and compare them based on:

• Speed of transmission
• Response to what kind of stimuli
• Myelination

Answer 24

A𝛿-fibres

• Fast/1st
• Thinly myelinated
• Mechanical/thermal

C-fibres

• 2nd/slow
• no myelination
• ALL noxious stimuli (polymodal)

Question 25

Describe the pathway of a 1st order neuron

Answer 25

From site of noxious stimuli Travels to soma (cell body) in dorsal root ganglion Terminates in dorsal horn of spinal cord

Question 26

What neurotransmitters are found between afferent 1st and 2nd order neurons? (in dorsal horn of spinal cord)

Answer 26

Peptides and glutamate

Question 27

What are the 2 tracts of 2nd order neurons and what is each responsible for? Where do they travel?

Answer 27

``` Spinothalamic tract (STT) - Perception of pain (intensity and location) ``` ``` Spinoreticulothalamic tract (SRT) - autonomic response to pain, arousal, fear etc. ``` Anterolateral system

Question 28

Where do 2nd order neurons terminate?

Answer 28

Thalamus

Question 29

How is pain classified?

Answer 29

``` Time course Severity Source of pain (visceral/somatic) Mechanisms - Nociceptive - Inflammatory - Pathological ```

Question 30

What mechanisms of pain are adaptive? What are maladaptive?

Answer 30

Adaptive - Nociceptive - Infammatory Maladaptive - Pathological

Question 31

In terms of inflammatory pain what is hyperalgesia and what is allodynia? What causes inflammatory pain?

Answer 31

Hyperalgesia - increased sensitivity to noxious stimuli Allodynia - increased sensitivity to innocuous (harmless) stimuli Activation of immune system - increased cytokine production and local inflam

Question 32

What are the 2 types of pathological mechanism, describe them What analgesics can be used?

Answer 32

Neuropathic - damage to neural tissue Dysfunctional - no identifiable damage/inflam e.g. IBS Normal analgesics don't work - ~use anti-depressants

Question 33

What gives skeletal muscle it's striated appearance?

Answer 33

Dark areas = A zone (where myosin and actin overlap) Light zones = I zone (where actin is without myosin)

Question 34

How does the rapid termination of muscle contraction occur?.

Answer 34

ACh is broken down by AChE (acetylcholinesterase) at the end plate membrane

Question 35

How does Ca+ release from the SR lead to muscle contraction?

Answer 35

Ca+ binds to troponin on actin which causes tropomyosin to move out of the way and thencross-bridge binding sites are avaliable for myosin to bind to actin and contract