Neural Control and Coordination

Biology · Class 11

Lesson 11 of 11 · 14 min

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Must-know facts

24 facts

  1. 1Coordination: organs interacting and complementing each other; the neural system is quick and point-to-point, the endocrine system works through hormones.
  2. 2Exercise raises breathing rate, heart beat and blood flow to meet the extra oxygen demand.
  3. 3Hydra: network of neurons. Insects: brain plus ganglia. Vertebrates: most developed.
  4. 4CNS = brain + spinal cord; PNS = all nerves joined to the CNS.
  5. 5Afferent fibres carry impulses to the CNS; efferent fibres carry them from the CNS.
  6. 6Somatic system: CNS to skeletal muscles. Autonomic system: CNS to involuntary organs and smooth muscles; split into sympathetic and parasympathetic.
  7. 7Neuron = cell body (with Nissl's granules) + dendrites (towards the cell body) + axon (away from it), ending in synaptic knobs with vesicles.
  8. 8Multipolar: cerebral cortex. Bipolar: retina. Unipolar: usually embryonic stage.
  9. 9Myelin sheath is formed by Schwann cells; the gaps are nodes of Ranvier. Myelinated fibres in spinal and cranial nerves.
  10. 10Resting axon: permeable to K⁺, nearly impermeable to Na⁺; inside high K⁺ and negative proteins, outside high Na⁺.
  11. 11Sodium-potassium pump: 3 Na⁺ out for 2 K⁺ in. Outside positive, inside negative = polarised.
  12. 12Stimulus: membrane freely permeable to Na⁺, Na⁺ rushes in, polarity reverses (depolarised) = action potential = nerve impulse.
  13. 13Current flows inside from A to B and outside from B to A, so the impulse moves along.
  14. 14Then K⁺ permeability rises, K⁺ diffuses out and the resting potential is restored.
  15. 15Synapse: pre-synaptic + post-synaptic membranes, with or without a synaptic cleft.
  16. 16Electrical synapses: membranes very close, current passes directly, always faster, rare in humans.
  17. 17Chemical synapse: impulse → vesicles fuse → neurotransmitter into cleft → binds receptors → ion channels open → new potential, excitatory or inhibitory.
  18. 18Meninges from outside in: dura mater, arachnoid, pia mater.
  19. 19Forebrain: cerebrum, thalamus, hypothalamus. Hemispheres joined by corpus callosum.
  20. 20Cortex = grey matter (cell bodies); inner myelinated tracts = white matter.
  21. 21Hypothalamus: body temperature, eating, drinking; hypothalamic hormones.
  22. 22Limbic system + hypothalamus: sexual behaviour, emotions, motivation.
  23. 23Midbrain: cerebral aqueduct, corpora quadrigemina. Hindbrain: pons, cerebellum, medulla.
  24. 24Medulla: respiration, cardiovascular reflexes, gastric secretions. Brain stem = midbrain + pons + medulla.

Common traps

Where marks are lost

Saying the pump moves 2 Na⁺ out for 3 K⁺ in.

It moves 3 Na⁺ out for every 2 K⁺ in.

Saying K⁺ rushes in during depolarisation.

Na⁺ rushes in to depolarise; K⁺ then diffuses out to restore the resting potential.

Saying the outside of a resting axon is negative.

At rest the outer surface is positive and the inner surface negative.

Saying chemical synapses are faster than electrical ones.

Transmission across an electrical synapse is always faster; electrical synapses are rare in humans.

Saying dendrites carry impulses away from the cell body.

Dendrites carry impulses towards the cell body; the axon carries them away.

Placing bipolar neurons in the cerebral cortex.

Multipolar neurons are in the cerebral cortex; bipolar neurons are in the retina.

Putting the pons or cerebellum in the forebrain, or the thalamus in the hindbrain.

Forebrain: cerebrum, thalamus, hypothalamus. Hindbrain: pons, cerebellum, medulla.

Saying the white matter is the cerebral cortex.

The cortex is grey matter (cell bodies); white matter is the inner myelinated tracts.

Listing the meninges as pia mater outermost.

Outer to inner: dura mater, arachnoid, pia mater.

Key terms

28 terms

Coordination
The process by which two or more organs interact and complement each other's functions.
CNS
Central neural system: the brain and spinal cord, where information is processed and control is exerted.
PNS
Peripheral neural system: all the nerves of the body connected to the CNS.
Afferent fibres
Nerve fibres that carry impulses from tissues and organs to the CNS.
Efferent fibres
Nerve fibres that carry regulating impulses from the CNS to tissues and organs.
Somatic neural system
The PNS division relaying impulses from the CNS to skeletal muscles.
Autonomic neural system
The PNS division relaying impulses from the CNS to involuntary organs and smooth muscles; sympathetic and parasympathetic.
Visceral nervous system
The nerves, fibres, ganglia and plexuses carrying impulses between the CNS and the viscera in both directions.
Nissl's granules
Granular bodies in the cell body and dendrites of a neuron.
Dendrites
Short branched fibres that carry impulses towards the cell body.
Axon
The long fibre that carries impulses away from the cell body.
Synaptic knob
Bulb-like ending of an axon branch holding vesicles of neurotransmitter.
Myelin sheath
Covering formed round an axon by Schwann cells.
Nodes of Ranvier
Gaps between neighbouring myelin sheaths on an axon.
Resting potential
The electrical potential difference across the resting neural membrane.
Sodium-potassium pump
Active transport that moves 3 Na⁺ out for 2 K⁺ in, keeping the ion gradients.
Action potential
The potential difference across a depolarised site of the membrane; the nerve impulse.
Depolarisation
Reversal of membrane polarity (inside positive, outside negative) as Na⁺ enters.
Synapse
Junction formed by the membranes of a pre-synaptic and a post-synaptic neuron.
Synaptic cleft
The fluid-filled gap between the two membranes at a chemical synapse.
Neurotransmitter
Chemical released into the synaptic cleft that carries the impulse to the next neuron.
Meninges
The three coverings of the brain: dura mater, arachnoid and pia mater.
Corpus callosum
Tract of nerve fibres joining the left and right cerebral hemispheres.
Association areas
Cortex regions neither clearly sensory nor motor, handling memory, communication and intersensory links.
Hypothalamus
Forebrain part at the base of the thalamus controlling temperature, eating and drinking, and secreting hypothalamic hormones.
Limbic system
Inner hemisphere parts with amygdala and hippocampus; with the hypothalamus, governs emotions, sexual behaviour and motivation.
Corpora quadrigemina
Four round swellings on the dorsal side of the midbrain.
Brain stem
Midbrain, pons and medulla oblongata; links the brain with the spinal cord.
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