Neural Control AND Coordination flash cards

1. 1.What are the two systems that coordinate and integrate all activities of organs in higher animals?

   The neural system (nervous system) and the endocrine system (hormones).

   Hint: One is fast and electrical, the other slow and chemical.

2. 2.What is a neuron?

   A neuron is the structural and functional unit of the nervous system; an excitable cell specialised to receive, conduct and transmit nerve impulses.

   Hint: Excitable unit of nervous system.

3. 3.Name the three major parts of a neuron.

   Cell body (cyton/soma), dendrites, and axon.

   Hint: Soma + two kinds of processes.

4. 4.What are Nissl's granules and where are they found?

   Nissl's granules are groups of rough endoplasmic reticulum (ribosome-rich) found in the cell body and dendrites of a neuron; they carry out protein synthesis.

   Hint: Rough ER in cyton/dendrites.

5. 5.What is the difference between dendrites and axon in terms of impulse direction?

   Dendrites conduct impulses TOWARDS the cell body; the axon conducts impulses AWAY from the cell body towards the synapse.

   Hint: Dendrite = towards, axon = away.

6. 6.What are the fine terminal branches at the end of an axon called, and what do they end in?

   They are called axon terminals, which end in bulb-like structures called synaptic knobs (containing synaptic vesicles with neurotransmitters).

   Hint: Knobs hold neurotransmitter vesicles.

7. 7.Classify neurons on the basis of the number of axons and dendrites (structural types).

   Multipolar (one axon, many dendrites — e.g. cerebral cortex), bipolar (one axon, one dendrite — e.g. retina), and unipolar (cell body with one axon only — found in embryonic stage).

   Hint: Multi, bi, uni — by number of processes.

8. 8.Where are multipolar and bipolar neurons typically found?

   Multipolar neurons are found in the cerebral cortex; bipolar neurons are found in the retina of the eye.

   Hint: Cortex vs retina.

9. 9.What are the two types of axons based on presence of a myelin sheath?

   Myelinated axons (covered by a myelin sheath with nodes of Ranvier) and non-myelinated axons (lacking a myelin sheath).

   Hint: With vs without the fatty covering.

10. 10.Which cells form the myelin sheath around axons in the peripheral nervous system?

    Schwann cells form the myelin sheath around axons in the peripheral nervous system.

    Hint: Named after their discoverer, wrap PNS axons.

11. 11.What are nodes of Ranvier?

    Nodes of Ranvier are the gaps between adjacent myelin sheath segments along a myelinated axon where the axon membrane is exposed.

    Hint: Gaps in the myelin covering.

12. 12.Where are myelinated nerve fibres commonly found and where are non-myelinated fibres found?

    Myelinated fibres are found in spinal and cranial nerves; non-myelinated fibres are commonly found in the autonomic and somatic neural systems.

    Hint: Spinal/cranial vs autonomic/somatic.

13. 13.QUESTION: In a myelinated axon, the impulse jumps from one node of Ranvier to the next. What is this rapid form of conduction called?

    Saltatory conduction. Because the myelin sheath insulates the axon, the impulse leaps node-to-node, making conduction much faster than in non-myelinated fibres.

    Hint: Latin 'saltare' = to jump.

14. 14.Are neurons capable of division in adults?

    No. Neurons are amitotic (they generally do not divide) in the adult; damaged neurons are usually not replaced.

    Hint: Post-mitotic cells.

15. 15.On the basis of function, what are the three types of neurons?

    Sensory (afferent) neurons carry impulses towards the CNS; motor (efferent) neurons carry impulses from the CNS to effectors; and interneurons (association/relay neurons) connect the two within the CNS.

    Hint: Afferent, efferent, and connectors.

16. 16.What is meant by the polarised state of a neuronal membrane?

    It is the resting condition in which the neuron is not conducting an impulse, and there is a potential difference across the axon membrane (outside positive, inside negative).

    Hint: Resting, charge-separated membrane.

17. 17.What is the approximate value of the resting membrane potential of a neuron?

    About $-70$ mV (the inside of the membrane is negatively charged relative to the outside).

    Hint: Around minus seventy millivolts.

18. 18.In the resting state, how are Na$^+$ and K$^+$ distributed across the axon membrane?

    The axoplasm (inside) has high K$^+$ and low Na$^+$; the fluid outside has high Na$^+$ and low K$^+$. Negatively charged proteins are also high inside.

    Hint: K high inside, Na high outside.

19. 19.How does the resting membrane maintain its ionic gradients?

    By the sodium-potassium pump, which actively transports 3 Na$^+$ out of and 2 K$^+$ into the cell, and by selective ionic permeability (membrane is more permeable to K$^+$ than Na$^+$ at rest).

    Hint: 3 Na out, 2 K in — active pump.

20. 20.QUESTION: Why is the outer surface of a resting axon membrane positively charged compared to the inner surface?

    Because the Na-K pump keeps Na$^+$ high outside, the membrane at rest is more permeable to K$^+$ (which leaks out), and large negatively charged proteins remain trapped inside. The net effect leaves the outer surface positive and the inner surface negative.

    Hint: Think ion distribution + trapped proteins.

21. 21.What is an action potential?

    An action potential is the rapid reversal of membrane potential (nerve impulse) that occurs when a site on the axon is stimulated, momentarily making the inside positive and outside negative.

    Hint: The nerve impulse itself.

22. 22.What causes depolarisation during an action potential?

    A stimulus increases the membrane's permeability to Na$^+$; Na$^+$ rushes into the axon (voltage-gated Na$^+$ channels open), reversing the polarity so the inside becomes positive (about $+30$ mV).

    Hint: Sodium floods inward.

23. 23.To what value does the membrane potential rise at the peak of depolarisation?

    About $+30$ mV (the membrane potential at the stimulated site becomes positive on the inside).

    Hint: Around plus thirty millivolts.

24. 24.What causes repolarisation of the membrane after depolarisation?

    Na$^+$ channels close and K$^+$ channels open; K$^+$ diffuses out of the axon, restoring the negative charge inside and returning the membrane towards its resting potential.

    Hint: Potassium exits to reset.

25. 25.What is the term for the difference in potential between the resting and stimulated membrane surfaces called that constitutes the impulse?

    The action potential (nerve impulse). The rise-and-fall of potential travels along the axon as a wave.

    Hint: The travelling wave of charge reversal.

26. 26.How does the action potential travel along the axon?

    Depolarisation at one point sets up local current that depolarises the adjacent region; this self-propagating wave moves along the axon, while the region behind repolarises.

    Hint: Each patch triggers the next.

27. 27.What is a synapse?

    A synapse is the junction between the terminal of one neuron (presynaptic) and the dendrite/cell body of the next neuron (postsynaptic), across which an impulse is transmitted.

    Hint: The neuron-to-neuron junction.

28. 28.What are the two types of synapses?

    Electrical synapses and chemical synapses.

    Hint: One uses current, the other uses molecules.

29. 29.How does transmission occur at an electrical synapse?

    The pre- and post-synaptic membranes are in very close contact, so electric current (the impulse) flows directly and almost instantly from one neuron to the next; transmission is faster than at chemical synapses.

    Hint: Direct current flow, very fast.

30. 30.Which type of synapse is faster, electrical or chemical, and which is more common in humans?

    Electrical synapses are faster (transmission is almost instant), but chemical synapses are far more common in the human nervous system.

    Hint: Faster one is rarer.

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