3.6.2 and 3.6.3 Nervous Coordination and Muscles Flashcards
label
answer
What is the purpose of the myelin sheath?
To insulate the axon
What is nervous control?
Electrical transmission via nerve impulses and chemical transmission at synapses, fast acting, APs carried by neurones with connections to specific cells, localises and short lived response
What is skeletal muscle?
Type of muscle you use to move
What is the myosin?
A contractile protein found in thick myofilament. It has an ATPase activity
What is actin?
A protein found in the thin myofilament
What is a myofibril?
Long, cylindrical organelles inside muscle fibres. each is made up of a series of contractile units called sarcomeres
What ion is required for muscle contraction?
Calcium ion
Describe sliding filament theory
Myosin and actin filaments slide over each other making the sarcomeres contract. the simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract
What happens to the actin-myosin binding site during muscle relaxation?
Blocked by tropomyosin
How is muscle contraction triggered and what then happens?
An AP from a motor neurone stimulates a muscle cell and it depolarises the sarcolemma. Depolarisation spreads down the T tubules to the sarcoplasmic reticulum. This causes the sarcoplasmic reticulum to release Ca2+ ions into the sarcoplasm
What happens to troponin during muscle contraction and what is the effect of this?
Calcium ion binds to the troponin, changing it’s shape so the tropomyosin is moved and the actin-myosin binding sites are exposed
What happens when the actin-myosin binding site is exposed?
Myosin heads bind to the actin-myosin binding sites on actin forming cross bridges
What is the effect of the actin-myosin binding sites being blocked?
Filaments cannot slide past each other
Why is ATP required for muscle contraction?
Hydrolysis of ATP provides energy to move the myosin head which pulls the actin along. it also provides energy to break the cross bridge so the myosin head detaches to allow binding to the next binding site
What happens when the myosin head reattaches to a different binding site ?
A new actin myosin cross bridge forms. Aany cross bridges form and break very rapidly pulling the actin filament along- which shortens the sarcomere so the muscle contracts
How is ATP broken down?
Hydrolysis reactions
What is the role of the stimulus during an action potential ?
This excites the neurone cell membrane, causing the Na+ channels to open. The membrane becomes more permeable to Na+, so Na+ diffuse into the neurone down the Na+ electrical gradient. This makes the inside of the neurone more positive.
What are the nodes of Ranvier ?
Gaps between schwann cells where there is bare membrane. Na+ channels are concentrated here.
What is myelin sheath made by ?
Schwann cells
Speed of nerve impulse dependant on…
Diameter of axon, temperature and myelination
What is the role of the Na/K pump and the K+ channel in the resting potential ?
Na/K pumps use AT to move 3 Na+ out of the neurone for every 2 K+ moved in, using ATP. Then K+ channel allows facilitated diffusion of K+ out of the neurone down their conc gradient. This makes the outside of the membrane more positive, creating a pd. Then K+ diffuse back in down their electrical gradient, there is no net movement of K+.
What is the voltage across the membrane during resting potential?
- 70mV