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Topic 6 - Coggle Diagram
Topic 6
Muscles
Key feature of muscle change during contraction - shortens, pulling action as opposed to a pushing action
Muscles are antagonistic pairs - one contracts, one relaxes - move the skeleton.
Circular muscle - contracting, diameter gets smaller
Skeletal muscle - voluntary, conscious compared to not conscious Cardiac and Smooth muscle - opposite
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Made of many myofibrils - cumulative strength, and avoids point of weakness
Muscle contraction
Calcium ions binds to troponin which changes the shape of the tropomyosin causing it to move and expose the binding site on actin.
Also activates ATPase on myosin head
Myosin head binds to binding site/actin-myosin cross bridge, and then moves and pulls actin filaments inwards. Actin filaments slide past each other
ATP binds to myosin head, and breaks bridge
Myosin head moves back
Energy from ATP hydrolysis enables myosin head to move, pulling actin filaments inwards
Active transport of calcium ions from myofibril to sarcoplasmic reticulum
Advantage of myoglobin in muscle cells and type of muscle that have a higher amount of it and why:
Has a higher affinity for oxygen, so load oxygen at a lower partial pressure than haemoglobin -- e.g. diving animals
More in slow twitch fibres, as need oxygen for aerobic respiration – final electron acceptor = oxygen
Why do fast twitch fibres need a store of creatine phosphate? How does it get recycled again after?
More phosphate is needed to make/recycle ATP -- breakdown of creatine phosphate during anaerobic respiration
Receptors
When there is no stimulus how is the resting potential maintained in the sensory neurone in the Pacinian corpuscle?
Cell membrane is impermeable to ions so need channel proteins. More Na+ on outside of membrane, due to Na+/K+ pump = 3Na+ and 2K+ in. Stretch-mediated sodium channels are too narrow to allow sodium ions in, but potassium channels are leaky so some diffuses out. Relatively positively charged outside the axon of neurone
When pressure is applied to the Pacinian corpuscle the following happens:
Pacinian corpuscle becomes deformed and presses on the tip of the sensory neurone in that area. The membrane of the neurone is stretched. This widens and deforms the stretch-mediated sodium channels in the membrane and sodium ions diffuse into the neurone. This changes the potential of the membrane - positive inside (depolarisation), produces a generator potential. If this reaches threshold, it becomes an action potential along the sensory neurone to the CNS
Rods and Cones
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What happens to make the cones sensitive?
Colour of wavelength makes iodopsin break down (bleaching) and stimulate AP in optic neurone
Explain why rods function in the dark and why it takes a delay to start seeing (adjustment)?
Only need low light intensity to break down rhodopsin (bleaching) and start AP
Rods have retinal convergence - many rods to one bipolar neurone, so spatial summation occurs
The release of neurotransmitter is added together at the bipolar neurone so enough is released so threshold can be reached to get an AP
And, rods are very sensitive to light intensity. So in brighter conditions rhodopsin is broken (bleached) down faster than it is reformed, so it needs to be reformed/resynthesised once entering a dark room before an AP can be sent to the brain as sight
Homeostasis
Action of insulin
Binds to specific glycoprotein receptor on target/liver/muscle cell
More channel/carrier/transport proteins in vesicles move and fuse with cell membrane of muscle cells
More transporter proteins change shape and open, increase permeability of muscle cell and enable more glucose to enter via facilitated diffusion.
More glucose for respiration and respiration enzymes activated to increase rate of respiration.
Enzymes controlling glycogenesis activated so more glucose converted to glycogen.
Enzymes controlling conversion of glucose to fats/lipids activated so rate of formation increases. Decrease blood glucose concentration
Why is it important that glucose is used/converted as it enters cells, in the action of insulin?
Maintains concentration gradient of blood glucose, so glucose diffuses in through facilitated via carrier proteins
How does the second messenger cAMP form after adrenaline or glucagon attaches to the receptor protein on membrane of liver cell?
Attaching - alters the shape of the protein receptor and this activates adenylate cyclase
This converts ATP to cAMP
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