Describe the structure and function of skeletal, cardiac and smooth muscle
| Cell structure | Cell function | |
| Skeletal muscle | Long, cylindrical, multiple nuclei on the outside. Striated (stripy) | Voluntary movements, moving the skeleton etc. |
| Cardiac muscle | Branching, one nucleus in the centre, striated | Pumping blood |
| Smooth muscle | Not striated (smooth-looking!) | Many involuntary movements (e.g. digesting food) |
Describe the mechanism of contractility in muscle and the generation of force
Explain the Ca2+ regulation of contraction
Describe the length tension relationship
Understand how Ca2+ regulation can result in wave summation and tetanus
Outline the physiological properties of motor units
Understand the organisation and function of the neuromuscular junction
I'm not really sure what I'm supposed to explain here. Basically, a motor neuron synapses onto an area of the muscle called the motor end plate. It is a cholinergic synapse, meaning that acetylcholine is released from the presynaptic neuron. That acetylcholine then binds to nicotinic ACh receptors on the target muscle cell. Nicotinic ACh receptors are sodium channels that always have an excitatory effect when opened. Each muscle cell only has one neuromuscular junction (there are more during development, but they get pruned away so that the muscles don't get conflicting and confusing input).
Describe how the nervous system (including reflexes) controls muscle contraction
It is also worth noting that spinal reflexes can be either monosynaptic or polysnaptic. In a monosynaptic reflex, the sensory neuron synapses directly onto a motor neuron. In a polysynaptic reflex, the sensory neuron synapses onto one or more interneurons, which synapse onto a motor neuron. Polysynaptic reflexes allow for the possibility of modulation of reflexes. For instance, in the inverse myotactic reflex (the "drop" reflex), an inhibitory interneuron secretes glycine (an inhibitory neurotransmitter), causing muscle relaxation. (This is the reflex that makes you instinctively drop something that would be too heavy to catch.)
Identify the muscle receptors and explain their role in spinal reflexes in skeletal muscle control.
There are several different muscle receptors that respond to tension and length of the muscle. These are the sorts of receptors that play a role in reflexes such as the knee-jerk reflex. The main receptors are Golgi tendon organs and muscle spindles. Golgi tendon organs are found in the tendon and are sensitive to tension and change of tension in the tendon. Muscle spindles are found in the belly of the muscle and are sensitive to length and change of length in the muscle. Both types of receptors can be either static (receptive to constant tension or length) or dynamic (responsive to changes in tension or length).
Describe different muscle fibre types & their properties
Describe the recruitment patterns of motor units in relation to the nervous system control of force generation.
- Motor Control- see the end of the third section where I talk about Henneman's size principle.
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