Module 6 - Nervous coordination Flashcards
3 marks
Explain how applying pressure to the Pacinian corpuscle produces the changes in membrane potential
- Pressure causes membrane / lamellae to become deformed
- Sodium ion channels in membrane open and sodium ions move in
- Greater pressure more channels open / sodium ions enter.
3 marks
Describe how stimulation of a Pacinian corpuscle produces a generator potential.
- There are stretch-mediated sodium ion channels in the membrane
- Increased pressure deforms (sensory neurone/axon) membrane/lamellae
- Sodium ion channels open
- Sodium ions diffuse in
- Depolarisation leading to generator potential
3 marks
Explain how a resting potential is maintained across the axon membrane in a neurone.
- Higher concentration of potassium ions inside and higher concentration of sodium ions outside the neurone
- (Membrane) more permeable to potassium ions (leaving than sodium ions entering)
- Sodium ions actively transported out and potassium ions in;
3 marks
Explain why the speed of transmission of impulses is faster along a myelinated axon than along a non-myelinated axon.
- Myelination provides electrical insulation
- In myelinated saltatory conduction
- In non-myelinated depolarisation occurs along whole length of axon
3 marks
A scientist investigated the effect of inhibitors on neurones. She added a respiratory inhibitor to a neurone. The resting potential of the neurone changed from –70 mV to 0 mV.
Explain why.
- Less ATP produced
- Less active transport
- Electrochemical gradient not maintained
4 marks
Explain how a resting potential is maintained in a neurone.
- Membrane less permeable to sodium ions
- Sodium ions actively transported out
- By sodium ion carrier
- 3 sodium ions out for two potassium ions in (inside is -70mV)
2 marks
Explain how a lower body temperature leads to slower nerve impulse conduction
- Slower diffusion
- Of ions /Na+/K-
3 marks
A myelinated axon conducts impulses faster than a non-myelinated axon. Explain the difference
- In myelinated, depolarisation only at nodes
- In myelinated, nerve impulse jumps from node to node / saltatory conduction
- In myelinated action potential does not travel along whole length
2 marks
Explain how the resting potential of-70mV is maintained in the sensory neurone
- Membrane more permeable to potassium ions and less permeable to sodium ions
- Sodium ions actively transported / pumped out and potassium ions in.
2 marks
Explain how MS, which is a disease in which parts of the myelin sheaths surrounding neurones are destroyed, results in slower responses to stimuli.
- Less / no saltatory conduction
- Impulse unable to ‘jump’ from node to node (of ranvier)
- More depolarisation over length / area of membranes
3 marks
Explain how chloride ions entering the post synaptic membrane will inhibit transmission of nerve impulses by postsynaptic neurones
- Post synaptic membrane becomes more negatively charged / hyperpolarised
- Stimulation does not reach threshold level / action potential not produced (more Na+ required)
- Depolarisation does not occur
2 marks
Explain how someone becomes aware of the pain if they prick their finger on a thorn
- Sensory neurone synapses with another relay neurone
- Impulses to brain
Temporal summation
Several impulses in short time provide enough neurostransmitter to reach threshold
2 marks
Explain the role of the refractory period
- So no impulses can be sent
- Seperates action potentials
- Ensures unidirectionality
Compare a NMJ and synapse
NMJ
* Only excitatory
* Connects motor neurone to muscles
* Always acetylholine
* No concept of threshold
Synapse
* Excitatory or inhibitory
* Connects 2 neurones
* Could be any neurotransmitter
* A new action potential is generated om mext neurone
