8. Muscles - Marco Narici Flashcards
What 2 types of cells are in the nervous system? Describe each one
- Neurones = transmits electrical impulses
- Supporting cells =
In CNS - glial cells, oligodendroctyes and microglia
In peripheral nerve - Schwann cells
Nerve cell structure
- Also known as?
- What 3 things does it consists of?
- Neurone
2. Cell body, dendrites and axon
Neurone structure
- What does the cell body contain?
- What do the dendrites do?
- What does the axon do?
- Which 2 ways can an axon end?
- Cell organelles
- Conducts nerve impulses towards the cell body
- Conducts nerve impulses away from the cell body
- Terminates as a swelling which synapses with the next neurone
Ends as a motor end plate on a skeletal muscle cell
Neurone
- Why do neurones have large nucleus and nucleolus?
- Size of nerve cell body?
- What 2 things are there a lot of for protein synthesis?
- What 3 features do all neurones have?
- High metabolic requirements
- Large
- RER and ribosomes
- Dendrites, soma and axons
Structure of a spinal nerve
- What will be the function of the neurones?
- What type of nerves are all spinal nerves?
- What are the 3 coverings?
- Some will have sensory function and some will have motor function
- Mixed nerves
- Epineurium
Perineurium
Endoneurium
Spinal nerve
- Describe the epineurium
- Describe the perineurium
- Cells that form the inner surface of the perineurium are joined by what?
- What is a bundle of nerve fibres also known as?
- Describe the endoneurium
- Dense layer of fibrous tissue
- Layers of flattened cells separated by layers of collagen; surrounds a bundle of nerve fibres
- Tight junctions
- Fascicle
- Thin layer of tissue surrounding individual axons and myelin sheath
Myelin
- What is it made out of?
- It can be formed from the cell membrane of what in the CNS?
- It can also be formed from the cell membrane of what in peripheral nerves?
- What is the node of Ranvier?
- What is found here?
- It is also the anatomical basis of what?
- In the CNS, all axons are what?
- Is this the case in peripheral nerves?
- Lipid
- Oligodendroctyes
- Schwann cells
- The gap between the myelin covering formed by adjacent Schwann cells
- Majority of the sodium ion channels
- Saltatory conduction
- Myelinated
- No, some axons are non-myelinated (but are embraced by supporting cells)
Muscle types
- Describe skeletal muscles in 3 ways
- Describe cardiac muscle in 3 ways
- Describe non-striated/smooth muscle in 3 ways
- Striated / rapid & strong contractions / usually voluntary nervous control
- Striated / contracts rhythmically / involuntary
- Contractions slow and sustained / involuntary / can be single unit or multi-unit
Skeletal muscle
- A single skeletal muscle is made up of what?
- Within this, what is there?
- Each muscle fibre contains what?
- What does this contain?
- Multiple fascicles
- Multiple skeletal muscle fibres
- Multiple myofibrils
- Myofilaments made of action, myosin and other proteins
Striated muscle contraction
- How is striated muscle shortened?
- What 2 things become shorter?
- What stays the same?
- What is shortening dependent on?
- Equation for force generated?
- Equation for velocity if contraction?
- Thick filaments pulling thin filaments towards the centre of the sarcomeres
- H zone and I band
- A band
- Calcium-dependent
- F = number of sarcomere in parallel
- V= number of sarcomere in series
Muscle fibre arrangement
What are the 2 ways skeletal muscle fibres can be arranged?
Parallel-fibres muscles
Pennate-fibred muscles
- Parallel-fibred muscles: fibre length? Relevance to function?
- Pennate fibred muscles: fibre length? Fibre number? Relevance to function?
- Longer fibres
Capable of greater shortening velocity - Shorter fibres but more fibres
Stronger but slower contracting
Motor units
- Each alpha motor neurone in the spinal cord can innervate what?
- A single muscle fibre receives innervation from what?
- Define motor unit
- Define Henneman’s size principle
- Several muscle fibres
- One motor neurone only
- An alpha motor neurone in the spinal cord and all the muscle fibres it innervates
- The degree of contraction of a whole muscle relies on recruiting motor units from smallest to largest
What are the 3 muscle fibre types? What is each one also known as?
- Slow oxidative fiber = SO = type 1
- Fast oxidative glycolytic fiber = FOG = type 2a
- Fast glycolytic fiber = FG = type 2x
Slow oxidative fiber = SO = type 1
- Twitch type?
- Metabolic type?
- Myosin ATPase activity?
- Source of ATP?
- Glycogen content?
- Fibre diameter?
- Resistance to fatigue?
- Functional role?
- Twitch type? Slow
- Metabolic type? Slow oxidative
- Myosin ATPase activity? Low
- Source of ATP? Oxidative phosphorylation
- Glycogen content? Low
- Fibre diameter? Low
- Resistance to fatigue? High
- Functional role? Posture/ endurance
Fast oxidative glycolytic fiber = FOG = type 2a
- Twitch type?
- Metabolic type?
- Myosin ATPase activity?
- Source of ATP?
- Glycogen content?
- Fibre diameter?
- Resistance to fatigue?
- Functional role?
- Twitch type? Fast
- Metabolic type? Fast oxidative-glycolytic
- Myosin ATPase activity? High
- Source of ATP?oxidative phosphorylation and glycolysis
- Glycogen content? Moderate
- Fibre diameter? Moderate
- Resistance to fatigue? Moderate
- Functional role? Medium endurance
Fast glycolytic fiber = FG = type 2x
- Twitch type?
- Metabolic type?
- Myosin ATPase activity?
- Source of ATP?
- Glycogen content?
- Fibre diameter?
- Resistance to fatigue?
- Functional role?
- Twitch type? Fast
- Metabolic type? Fast glycolytic
- Myosin ATPase activity? High
- Source of ATP? Glycolysis
- Glycogen content? High
- Fibre diameter? High
- Resistance to fatigue? Low
- Functional role? Rapid powerful movements
Neurotransmitter
- What happens to it in a presynaptic neurone?
- What happens to it when a presynaptic neurone is stimulated?
- Synthesised and stored
2. Released
- What is between the presynaptic cell and the post synaptic cell?
- What 2 types of synapses can there be? What takes place here?
- What 2 types of transmittor receptors can there be?
- What ion is predominantly inside the cell?
- What 2 ions are predominantly outside the cell?
- Synaptic cleft
- Axo-dendritic + axo-axonic
Neurotransmission - G-protein linked + gated channels
- Potassium
- Sodium and chloride
- What is the name of the equation that works out the equilibrium potential for any ion?
- What is the name of the equation that works out the membrane potential?
- What is the resting membrane potential in neurones?
- Nernst equation
- Goldman equation
- Electronegative
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?
- EPSP = excitatory post synaptic potential
Stimulate excitatory nerve
Depolarisation of post synaptic cell - IPSP = inhibitory post synaptic potential
Stimulate inhibitory nerve
Hyperpolarisation of post synaptic cell
- Explain temporal summation
- Explain spatial summation
- What do these summations determine?
- 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 separate inputs - separated EPSPs/IPSPs when inputs fire separately but when they fire together you get a combined (summated) EPSP/IPSP
- Likelihood of an AP being set up in post synaptic cell
ACh release at NMJ
- Is dependent on what happening to the motor neurone?
- What ion influx is there and through what?
- What do the ions promote?
- What is activated by ACh? How many ACh molecules per each one?
- This leads to an influx of what ions in the muscle fibre membrane? What does this result in?
- Release of several vesicles of ACh (when the motor neurone is activated) causes what?
- Depolarisation of the presynaptic membrane
- Calcium ions / voltage dependent calcium channels
- Fusion of ACh vesicles with presynaptic membrane
- nAChR’s = nicotinic ACh receptor - 2 molecules per receptor
- Sodium ions - depolarisation of muscle fibre membrane
- EPP = end plate potential
Drugs used at the NMJ to induce paralysis
- Which drugs antagonise the action of ACh on nAChRs?
- Which activate nAChRs for a long time?
- Which increase ACh in the synapse, reversing the effects of competitive muscle relaxants? What kind of side effects do they cause?
- Competitive muscle relaxants
- Depolarising muscle relaxants
- Anticholinesterases
Muscarinic side effects
- What can 2 action potentials close together cause?
- What can 4 action potentials close together cause?
- What can 8 action potentials very close together cause?
- In skeletal muscle, why is wave summation and tetanic contraction possible?
- Wave summation
- Unfused tetanus
- Fused tetanus
- The twitch contraction lasts longer than the action potential
- What are thick filaments made of?
2. What are thin filaments made of?
- Myosin
2. Actin
Myosin = thick filaments
Which part interacts with the thin filaments?
Head
Actin = thin filaments
- What are the other 2 things that the thin filaments is made up of?
- Which one prevents the myosin head binding to the actin?
- Troponin and tropomyosin
2. Tropomyosin
Calcium ions in contraction
- In striated muscle, what do the calcium ions bind to?
- What does this cause?
- What is moved out of the way?
- If other conditions are correct (eg. ATP levels high enough) what takes place?
- What is this process known as?
- Troponin C
- Conformation change in the troponin complex
- Moves tropomyosin out of myosin binding sites
- Contraction
- Actin-linked regulation of muscle contraction
Calcium ions
- In skeletal muscle, what does sarcoplasmic reticulum do when the muscle is relaxed and when it is depolarised?
- In cardiac muscle, apart from the SR, where else of the calcium ions come from?
- In smooth muscle, where do almost all calcium ions come from?
- Muscle relaxed = SR acts as calcium store
Muscle depolarised = SR releases calcium ions - From the extracellular fluid via calcium channels
- Extracellular fluid
T-tubules
- What do T tubules allow?
- What do T tubules come close to in striated muscle?
- When the membrane on the T tubule is depolarised, what does this do to SR?
- Because of this, ions can be released where they are needed. What are the 2 places they are needed?
- Changes in membrane potential to be communicated right to the middle of the muscle fibre
- SR
- Calcium release
- Junction of the A bands and the I bands
The cross bridge cycle of contraction
- What do myosin heads hydrolyse in order to become reorientated and energised?
- Myosin heads then bind to actin, forming what?
- Myosin heads then rotate toward what?
- As the myosin head binds to ATP, what happens?
- Contraction will continue if what 2 things are available?
- ATP
- Crossbridges
- The centre of the sarcomere
- The cross ridges detach from actin
- ATP and calcium ions
What are the 3 type of nerve fibres? Which of these are myelinated and which are non-myelinated?
A / B / C
A and B myelinated
C unmyelinated
Nerves fibre types: As you go from A-C…
- Diameter
- Conduction velocity
- Decreases
2. Decreases
What are the 3 type of cutaneous receptors?
- Pain and temperature
- Touch
- Deep pressure
Adaptation of receptors
- What are the 2 types of adaptations?
- What does the CNS use to judge the amplitude of the stimulus?
- 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?
- Slow adaptation and rapid adaptation
- Frequency of APs coming in via a given type of fibre
- Slow adaptation
What 5 types of sensory receptors are there?
Pain Touch Deep pressure Tendon Muscle spindle
Muscle and tendon proprioceptors
- Muscle spindles are used to detect changes in what?
- What are the main muscle fibres outside known as?
- What are the small muscle fibres inside known as?
- Golgi tendon organs are used to detect changes in what?
- Muscle length
- Extrafusal muscle fibres
- Intrafusal muscle fibres
- Tendon tension
Spinal cord
- White matter contains axons of what?
- Grey matter contains what?
- What is in the ventral and lateral horns?
- What is in the dorsal horn?
- Axons of neurones ascending to/descending from higher centres in CNS
- Cell bodies of many kinds of neurones
- Cell bodies of motor neurones
- Cell bodies of sensory neurones and interneurones
- How do sensory neurones enter the dorsal horn?
2. How do motor neurones leave the ventral and lateral horn?
- Via the dorsal root of the spinal nerve
2. Via the ventral root of the spinal nerve