| Muslces | - Effector organs that respond to nervous stimulation by contracting and o bring about movement
- Cardiac + smooth muscle is not under conscious control |
| 3 types of muscle | - Cardiac, in heart
- Smooth, walls of blood vessels + gut
- Skeletal, makes up bulk of body muscle in vertebrates, attached to bone, conscious control |
| Gross structure of skeletal muscle | - Individual muscles are made up of millions of tiny muscle fibres, myofibrils
- They are arranged in order to maximise its force
- Muscle is composed of smaller units bundled into progressively larger ones
- The seperate cells become fused together into muscle fibres
- These muscle fibres share nuclei + sacroplasm |
| Sacroplasm meaning | - Cytoplasm
- Sacroplasm is mostly found around fibre
- Has large conc. of mitochondria + sarcoplasmic reticulum (strores ca2+) |
| Types of protein filament that make up myofibrils | - Actin
- Myosin |
| Actin | - Thinner, consists of 2 strands twisted around one another |
| Myosin | - Thicker, consists of long rod-shaped tails with bulbous heads that project to the side |
| Another important protein found in muscle | - Tropomyosin
- Forms fibrous strand around actin filament |
| A bands and I bands | - At the centre of each A band is a lighter-coloured region called the H-zone
- At the centre of each I band is a line called Z-line
- The distance between adjacent Z-lines is called sacromere
- When muscle contracts, these sacromeres shorten + the pattern of light + dark bands changes
During contration
- Z lines = closer together
- H zone = shortens
- I band = shortens
- A band = stays the same |
| Types of muscle fibre | - Slow-twitch fibres
- Fast-twitch fibres |
| Slow-twitch fibres | - Marathon running
- Less myosin filaments
- Little store of myoglobin
- Less powerful contractions
- Aerobically respires
- Good blood supply
- Lots of mitochondria |
| Fast-twitch fibres | - Sprinting/weight lifting
- More myosin filaments
- Large store of myoglobin
- Stronger contractions
- Anaerobically respires
- Glycogen store |
| Similarities between neuromuscular junction and a synapse | - Have neurotransmitters that are transported by diffusion
- Have receptors, that on binding with the neurotransmitter, cause an influx of S ions
- Use a S-P pump to repolarise the axon
- Use enzymes to breakdown neurotransmitter |
| Neuromuscular junction | - Only excitatory
- Only links neurons to muscles
- Only motor neurons are involved
- The action potential ends here (it is the end of neural pathway)
- Acetylcholine binds to receptors on membrane of muscle fibre |
| Synapse | - May be excitatory or inhibitory
- Links neurons to neurons, or neurons to other effector organs
- Motor, sensory + intermediate neurons may be involved
- A new action potential may be produced along another neuron ( postsynaptic neuron)
- Acetylcholine binds to receptors on membrane of post-synaptic neuron |
