8. Muscles - Marco Narici

Question 1

What 2 types of cells are in the nervous system? Describe each one

Answer 1

1. Neurones = transmits electrical impulses
2. Supporting cells =
   In CNS - glial cells, oligodendroctyes and microglia
   In peripheral nerve - Schwann cells

Question 2

Nerve cell structure

1. Also known as?
2. What 3 things does it consists of?

Answer 2

1. Neurone

2. Cell body, dendrites and axon

Question 3

Neurone structure

1. What does the cell body contain?
2. What do the dendrites do?
3. What does the axon do?
4. Which 2 ways can an axon end?

Answer 3

1. Cell organelles
2. Conducts nerve impulses towards the cell body
3. Conducts nerve impulses away from the cell body
4. Terminates as a swelling which synapses with the next neurone
   Ends as a motor end plate on a skeletal muscle cell

Question 4

Neurone

1. Why do neurones have large nucleus and nucleolus?
2. Size of nerve cell body?
3. What 2 things are there a lot of for protein synthesis?
4. What 3 features do all neurones have?

Answer 4

1. High metabolic requirements
2. Large
3. RER and ribosomes
4. Dendrites, soma and axons

Question 5

Structure of a spinal nerve

1. What will be the function of the neurones?
2. What type of nerves are all spinal nerves?
3. What are the 3 coverings?

Answer 5

1. Some will have sensory function and some will have motor function
2. Mixed nerves
3. Epineurium
   Perineurium
   Endoneurium

Question 6

Spinal nerve

1. Describe the epineurium
2. Describe the perineurium
3. Cells that form the inner surface of the perineurium are joined by what?
4. What is a bundle of nerve fibres also known as?
5. Describe the endoneurium

Answer 6

1. Dense layer of fibrous tissue
2. Layers of flattened cells separated by layers of collagen; surrounds a bundle of nerve fibres
3. Tight junctions
4. Fascicle
5. Thin layer of tissue surrounding individual axons and myelin sheath

Question 7

Myelin

1. What is it made out of?
2. It can be formed from the cell membrane of what in the CNS?
3. It can also be formed from the cell membrane of what in peripheral nerves?
4. What is the node of Ranvier?
5. What is found here?
6. It is also the anatomical basis of what?
7. In the CNS, all axons are what?
8. Is this the case in peripheral nerves?

Answer 7

1. Lipid
2. Oligodendroctyes
3. Schwann cells
4. The gap between the myelin covering formed by adjacent Schwann cells
5. Majority of the sodium ion channels
6. Saltatory conduction
7. Myelinated
8. No, some axons are non-myelinated (but are embraced by supporting cells)

Question 8

Muscle types

1. Describe skeletal muscles in 3 ways
2. Describe cardiac muscle in 3 ways
3. Describe non-striated/smooth muscle in 3 ways

Answer 8

1. Striated / rapid & strong contractions / usually voluntary nervous control
2. Striated / contracts rhythmically / involuntary
3. Contractions slow and sustained / involuntary / can be single unit or multi-unit

Question 9

Skeletal muscle

1. A single skeletal muscle is made up of what?
2. Within this, what is there?
3. Each muscle fibre contains what?
4. What does this contain?

Answer 9

1. Multiple fascicles
2. Multiple skeletal muscle fibres
3. Multiple myofibrils
4. Myofilaments made of action, myosin and other proteins

Question 10

Striated muscle contraction

1. How is striated muscle shortened?
2. What 2 things become shorter?
3. What stays the same?
4. What is shortening dependent on?
5. Equation for force generated?
6. Equation for velocity if contraction?

Answer 10

1. Thick filaments pulling thin filaments towards the centre of the sarcomeres
2. H zone and I band
3. A band
4. Calcium-dependent
5. F = number of sarcomere in parallel
6. V= number of sarcomere in series

Question 11

Muscle fibre arrangement

What are the 2 ways skeletal muscle fibres can be arranged?

Answer 11

Parallel-fibres muscles

Pennate-fibred muscles

Question 12

1. Parallel-fibred muscles: fibre length? Relevance to function?
2. Pennate fibred muscles: fibre length? Fibre number? Relevance to function?

Answer 12

1. Longer fibres
   Capable of greater shortening velocity
2. Shorter fibres but more fibres
   Stronger but slower contracting

Question 13

Motor units

1. Each alpha motor neurone in the spinal cord can innervate what?
2. A single muscle fibre receives innervation from what?
3. Define motor unit
4. Define Henneman’s size principle

Answer 13

1. Several muscle fibres
2. One motor neurone only
3. An alpha motor neurone in the spinal cord and all the muscle fibres it innervates
4. The degree of contraction of a whole muscle relies on recruiting motor units from smallest to largest

Question 14

What are the 3 muscle fibre types? What is each one also known as?

Answer 14

1. Slow oxidative fiber = SO = type 1
2. Fast oxidative glycolytic fiber = FOG = type 2a
3. Fast glycolytic fiber = FG = type 2x

Question 15

Slow oxidative fiber = SO = type 1

1. Twitch type?
2. Metabolic type?
3. Myosin ATPase activity?
4. Source of ATP?
5. Glycogen content?
6. Fibre diameter?
7. Resistance to fatigue?
8. Functional role?

Answer 15

1. Twitch type? Slow
2. Metabolic type? Slow oxidative
3. Myosin ATPase activity? Low
4. Source of ATP? Oxidative phosphorylation
5. Glycogen content? Low
6. Fibre diameter? Low
7. Resistance to fatigue? High
8. Functional role? Posture/ endurance

Question 16

Fast oxidative glycolytic fiber = FOG = type 2a

1. Twitch type?
2. Metabolic type?
3. Myosin ATPase activity?
4. Source of ATP?
5. Glycogen content?
6. Fibre diameter?
7. Resistance to fatigue?
8. Functional role?

Answer 16

1. Twitch type? Fast
2. Metabolic type? Fast oxidative-glycolytic
3. Myosin ATPase activity? High
4. Source of ATP?oxidative phosphorylation and glycolysis
5. Glycogen content? Moderate
6. Fibre diameter? Moderate
7. Resistance to fatigue? Moderate
8. Functional role? Medium endurance

Question 17

Fast glycolytic fiber = FG = type 2x

1. Twitch type?
2. Metabolic type?
3. Myosin ATPase activity?
4. Source of ATP?
5. Glycogen content?
6. Fibre diameter?
7. Resistance to fatigue?
8. Functional role?

Answer 17

1. Twitch type? Fast
2. Metabolic type? Fast glycolytic
3. Myosin ATPase activity? High
4. Source of ATP? Glycolysis
5. Glycogen content? High
6. Fibre diameter? High
7. Resistance to fatigue? Low
8. Functional role? Rapid powerful movements

Question 18

Neurotransmitter

1. What happens to it in a presynaptic neurone?
2. What happens to it when a presynaptic neurone is stimulated?

Answer 18

1. Synthesised and stored

2. Released

Question 19

1. What is between the presynaptic cell and the post synaptic cell?
2. What 2 types of synapses can there be? What takes place here?
3. What 2 types of transmittor receptors can there be?
4. What ion is predominantly inside the cell?
5. What 2 ions are predominantly outside the cell?

Answer 19

1. Synaptic cleft
2. Axo-dendritic + axo-axonic
   Neurotransmission
3. G-protein linked + gated channels
4. Potassium
5. Sodium and chloride

Question 20

1. What is the name of the equation that works out the equilibrium potential for any ion?
2. What is the name of the equation that works out the membrane potential?
3. What is the resting membrane potential in neurones?

Answer 20

1. Nernst equation
2. Goldman equation
3. Electronegative

Question 21

What are the 2 types of postsynaptic potentials and what kind of nerve do you have to stimulate in each one?
Which one represents depolarisation of a postsynaptic cell and which one represents hyperpolarisation?

Answer 21

1. EPSP = excitatory post synaptic potential
   Stimulate excitatory nerve
   Depolarisation of post synaptic cell
2. IPSP = inhibitory post synaptic potential
   Stimulate inhibitory nerve
   Hyperpolarisation of post synaptic cell

Question 22

1. Explain temporal summation
2. Explain spatial summation
3. What do these summations determine?

Answer 22

1. 4 separate incoming action potentials - first there will be 2 separate EPSPs/IPSPs and then when 2 action potentials get close enough there will be “summated” EPSPs/IPSPs
2. 2 separate inputs - separated EPSPs/IPSPs when inputs fire separately but when they fire together you get a combined (summated) EPSP/IPSP
3. Likelihood of an AP being set up in post synaptic cell

Question 23

ACh release at NMJ

1. Is dependent on what happening to the motor neurone?
2. What ion influx is there and through what?
3. What do the ions promote?
4. What is activated by ACh? How many ACh molecules per each one?
5. This leads to an influx of what ions in the muscle fibre membrane? What does this result in?
6. Release of several vesicles of ACh (when the motor neurone is activated) causes what?

Answer 23

1. Depolarisation of the presynaptic membrane
2. Calcium ions / voltage dependent calcium channels
3. Fusion of ACh vesicles with presynaptic membrane
4. nAChR’s = nicotinic ACh receptor - 2 molecules per receptor
5. Sodium ions - depolarisation of muscle fibre membrane
6. EPP = end plate potential

Question 24

Drugs used at the NMJ to induce paralysis

1. Which drugs antagonise the action of ACh on nAChRs?
2. Which activate nAChRs for a long time?
3. Which increase ACh in the synapse, reversing the effects of competitive muscle relaxants? What kind of side effects do they cause?

Answer 24

1. Competitive muscle relaxants
2. Depolarising muscle relaxants
3. Anticholinesterases
   Muscarinic side effects

Question 25

1. What can 2 action potentials close together cause? 2. What can 4 action potentials close together cause? 3. What can 8 action potentials very close together cause? 4. In skeletal muscle, why is wave summation and tetanic contraction possible?

Answer 25

1. Wave summation 2. Unfused tetanus 3. Fused tetanus 4. The twitch contraction lasts longer than the action potential

Question 26

1. What are thick filaments made of? | 2. What are thin filaments made of?

Answer 26

1. Myosin | 2. Actin

Question 27

Myosin = thick filaments | Which part interacts with the thin filaments?

Answer 27

Head

Question 28

Actin = thin filaments 1. What are the other 2 things that the thin filaments is made up of? 2. Which one prevents the myosin head binding to the actin?

Answer 28

1. Troponin and tropomyosin | 2. Tropomyosin

Question 29

Calcium ions in contraction 1. In striated muscle, what do the calcium ions bind to? 2. What does this cause? 3. What is moved out of the way? 4. If other conditions are correct (eg. ATP levels high enough) what takes place? 5. What is this process known as?

Answer 29

1. Troponin C 2. Conformation change in the troponin complex 3. Moves tropomyosin out of myosin binding sites 4. Contraction 5. Actin-linked regulation of muscle contraction

Question 30

Calcium ions 1. In skeletal muscle, what does sarcoplasmic reticulum do when the muscle is relaxed and when it is depolarised? 2. In cardiac muscle, apart from the SR, where else of the calcium ions come from? 3. In smooth muscle, where do almost all calcium ions come from?

Answer 30

1. Muscle relaxed = SR acts as calcium store Muscle depolarised = SR releases calcium ions 2. From the extracellular fluid via calcium channels 3. Extracellular fluid

Question 31

T-tubules 1. What do T tubules allow? 2. What do T tubules come close to in striated muscle? 3. When the membrane on the T tubule is depolarised, what does this do to SR? 4. Because of this, ions can be released where they are needed. What are the 2 places they are needed?

Answer 31

1. Changes in membrane potential to be communicated right to the middle of the muscle fibre 2. SR 3. Calcium release 4. Junction of the A bands and the I bands

Question 32

The cross bridge cycle of contraction 1. What do myosin heads hydrolyse in order to become reorientated and energised? 2. Myosin heads then bind to actin, forming what? 3. Myosin heads then rotate toward what? 4. As the myosin head binds to ATP, what happens? 5. Contraction will continue if what 2 things are available?

Answer 32

1. ATP 2. Crossbridges 3. The centre of the sarcomere 4. The cross ridges detach from actin 5. ATP and calcium ions

Question 33

What are the 3 type of nerve fibres? Which of these are myelinated and which are non-myelinated?

Answer 33

A / B / C A and B myelinated C unmyelinated

Question 34

Nerves fibre types: As you go from A-C... 1. Diameter 2. Conduction velocity

Answer 34

1. Decreases | 2. Decreases

Question 35

What are the 3 type of cutaneous receptors?

Answer 35

1. Pain and temperature 2. Touch 3. Deep pressure

Question 36

Adaptation of receptors 1. What are the 2 types of adaptations? 2. What does the CNS use to judge the amplitude of the stimulus? 3. The receptor for a painful stimuli (for example) would display which type of adaptation so that there is a continuous message that the stimulus is still there?

Answer 36

1. Slow adaptation and rapid adaptation 2. Frequency of APs coming in via a given type of fibre 3. Slow adaptation

Question 37

What 5 types of sensory receptors are there?

Answer 37

``` Pain Touch Deep pressure Tendon Muscle spindle ```

Question 38

Muscle and tendon proprioceptors 1. Muscle spindles are used to detect changes in what? 2. What are the main muscle fibres outside known as? 3. What are the small muscle fibres inside known as? 4. Golgi tendon organs are used to detect changes in what?

Answer 38

1. Muscle length 2. Extrafusal muscle fibres 3. Intrafusal muscle fibres 4. Tendon tension

Question 39

Spinal cord 1. White matter contains axons of what? 2. Grey matter contains what? 3. What is in the ventral and lateral horns? 4. What is in the dorsal horn?

Answer 39

1. Axons of neurones ascending to/descending from higher centres in CNS 2. Cell bodies of many kinds of neurones 3. Cell bodies of motor neurones 4. Cell bodies of sensory neurones and interneurones

Question 40

1. How do sensory neurones enter the dorsal horn? | 2. How do motor neurones leave the ventral and lateral horn?

Answer 40

1. Via the dorsal root of the spinal nerve | 2. Via the ventral root of the spinal nerve