nervous coordination and muscles Flashcards
why is speed of conduction greater in a myelinated sheath than an non myelinated sheath
In a non-myelinated axon, action potentials need to be triggered along the whole axon. whereas
In myelinated axons, action potentials need to be triggered only at the nodes of Ranvier. the myelinated axon prevents the movement of ions
As a result, myelinated axons produce a reduced number of action potentials.The formation of an action potential takes time.
So, in a myelinated axon, where a reduced number of action potentials are needed, less time is taken up with the repeated formation of action potentials.
As a result, myelinated axons have a greater speed of conductance compared to non-myelinated axons.
how can an organism detect the strength of a stimulus
measure the frequency of action potentials . the greater the frequency the greater the strength of a stimulus
what is a limiting factor of the frequency of action potentials
the length of its refractory period
MS leads to the slowing down of transmission of nerve impulses in the brain and spinal cord. Explain why.
No saltatory conduction can occur without myelin sheaths on neurones. Instead, depolarisation would have to occur through the length of the neurone. This is slower, which slows down nerve transmission.
Symptoms of MS include difficulty walking and muscle stiffness. Scientists have developed a drug called bexarotene that has been shown to be effective in repairing myelin sheaths. Explain how bexarotene could treat the symptoms of MS.
Bexarotene restores myelin sheaths around neurones in the brain and spinal cord and myelin is an electrical insulator. This means saltatory conduction can occur, where action potentials jump between nodes of Ranvier. This would treat the symptoms of MS because the speed of conductance would be increased since saltatory conduction is faster. As a result, nerve impulses can travel through the brain and spinal cord faster to neuromuscular junctions and contract muscle
what is an adaptation of the synaptic cleft
it has a short diffusion distance and therefore a faster action potential as faster diffusion of aceytlcholine
what is a difference between cholinergic and neuromuscular junctions
Nerve impulses end at a neuromuscular junction, as a muscle contraction occurs. In cholinergic synapses, the nerve impulse continues.
why is it important that acetylcholine is broken down by acetylcholinesterase
-acetylcholine is broken down to prevent sodium ion channels on the post synaptic membrane staying open , therefore prevents permanent depolarisation of the post synaptic membrane
what are the similarities and differences between a cholinergic synapse and a neuromuscular junction
- both use acetylcholine?
-both are stimulated by action potentials at the presynaptic membrane - cholinergic synapse found between neurones whereas neuromuscular junction can only be excitatory
Check your answer against the following model answer.
Lower concentration of calcium ions within the muscle tissues will lead to less tropomyosin being moved away from actin binding sites within the sarcomeres.
This will lead to fewer actinomyosin bridges being formed.
As a result, fewer myosin heads are able to successfully pull on actin filaments - leading to a reduced force for muscle contraction.
Check your answer against the following model answer.
Lower concentration of calcium ions within the muscle tissues will lead to less tropomyosin being moved away from actin binding sites within the sarcomeres.
This will lead to fewer actinomyosin bridges being formed.
As a result, fewer myosin heads are able to successfully pull on actin filaments - leading to a reduced force for muscle contraction.
