synaptic transmission ms Flashcards
Explain how the resting potential of –70 mV is maintained in the sensory neurone
when no pressure is applied.
membrane more permeable to potassium ions and less permeable to sodium ions
potassium ions move in and sodium ions move out by active transport
When DDT binds to a sodium ion channel, the channel remains open all the time.
Use this information to suggest how DDT kills insects.
Neurones remain depolarised;
2. So no action potentials
Suggest how cannabinoids could prevent muscle contraction.
as it closes calcium ion channels
Prevents influx of calcium ions into pre-synaptic membrane
vesicles don’t fuse with membrane
Neurotransmitter does not diffuse across synapse / does not bind to
receptors
No action potential
The blink reflex involves synapses. Channel proteins on presynaptic neurones are involvedin reflex responses. Explain how.
Allows calcium ions in;
At end of presynaptic neurone;
Causing release of neurotransmitter;
Blinking involves cholinergic synapses. Anaesthetic S is a similar shape to acetylcholine. Suggest how anaesthetic S stops the transmission across the synapse.
Binds to receptor;
On postsynaptic (membrane); Prevents acetylcholine from binding;
No action potential in postsynaptic neurone;
Explain how the release of acetylcholine at an excitatory synapse reduces the membranepotential of the postsynaptic membrane
Binds to receptor and opens Na+ channels; Na+ enter and make membrane potential less negative
When the postsynaptic membrane is stimulated by acetylcholine, an action potential is less likely if GABA is released at the same time. Explain why.
GABA opens K+ and Cl– channels so K+ passes out and Cl– passes in
Membrane potential hyperpolarised
Requires increased stimulation
must allow more Na+ to enter;
To reach threshold;
People who have McArdle’s disease produce less ATP than healthy people. As a
result, they are not able to maintain strong muscle contraction during exercise. Use
your knowledge of the sliding filament theory to suggest why.
ATP needed for
cross bridges between actin and myosin;
Power stroke / movement of myosin heads / pulling of actin;
Detachment of myosin heads;
Myosin heads move back to original position
why’s there more phosphocreatine in older people
Fast muscle fibres used for rapid contractions;
Phosphocreatine used up rapidly during contraction / to make ATP;
(As people get older) slower metabolic rate slower ATP production
slower respiration;
ATP used to reform phosphocreatine;
what Attaches to Z line at the end of
the sarcomere
actin
If myosin molecules are unable to bind to other myosin molecules, this prevents
muscle contraction.
why
Can’t form myosin thick filaments;
Can’t pull actin past myosin
Myosin moves
Can’t move actin towards each other
can’t pull Z lines together.
Both slow and fast muscle fibres contain ATPase.
Explain why.
to breakdown atp
as muscle contraction requires energy from hydrolysis of atp
ATP used by myosin
Explain how a decrease in the concentration of calcium ions within muscle
tissues could cause a decrease in the force of muscle contraction.
Less tropomyosin moved from binding site.
Fewer actinomyosin bridges formed;
Myosin head does not move
The trained mice were
able to exercise for a longer time period than control mice.
why
More aerobic respiration produces more ATP;
2. Anaerobic respiration delayed;
3. Less or no lactate;
During vigorous exercise, the pH of skeletal muscle tissue falls. This fall in
pH leads to a reduction in the ability of calcium ions to stimulate muscle
contraction.
Suggest how.
- Low pH changes shape of calcium ion receptors
- Fewer calcium ions bind to tropomyosin
- Fewer tropomyosin molecules move away;
- Fewer binding sites on actin revealed;
- Fewer cross-bridges can form
