Lesson 11 of 11 · 14 min
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Next Toppers - 11th ScienceWhole chapter · Hinglish
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Must-know facts
24 facts
- 01Coordination: organs interacting and complementing each other; the neural system is quick and point-to-point, the endocrine system works through hormones.
- 02Exercise raises breathing rate, heart beat and blood flow to meet the extra oxygen demand.
- 03Hydra: network of neurons. Insects: brain plus ganglia. Vertebrates: most developed.
- 04CNS = brain + spinal cord; PNS = all nerves joined to the CNS.
- 05Afferent fibres carry impulses to the CNS; efferent fibres carry them from the CNS.
- 06Somatic system: CNS to skeletal muscles. Autonomic system: CNS to involuntary organs and smooth muscles; split into sympathetic and parasympathetic.
- 07Neuron = cell body (with Nissl's granules) + dendrites (towards the cell body) + axon (away from it), ending in synaptic knobs with vesicles.
- 08Multipolar: cerebral cortex. Bipolar: retina. Unipolar: usually embryonic stage.
- 09Myelin sheath is formed by Schwann cells; the gaps are nodes of Ranvier. Myelinated fibres in spinal and cranial nerves.
- 10Resting axon: permeable to K⁺, nearly impermeable to Na⁺; inside high K⁺ and negative proteins, outside high Na⁺.
- 11Sodium-potassium pump: 3 Na⁺ out for 2 K⁺ in. Outside positive, inside negative = polarised.
- 12Stimulus: membrane freely permeable to Na⁺, Na⁺ rushes in, polarity reverses (depolarised) = action potential = nerve impulse.
- 13Current flows inside from A to B and outside from B to A, so the impulse moves along.
- 14Then K⁺ permeability rises, K⁺ diffuses out and the resting potential is restored.
- 15Synapse: pre-synaptic + post-synaptic membranes, with or without a synaptic cleft.
- 16Electrical synapses: membranes very close, current passes directly, always faster, rare in humans.
- 17Chemical synapse: impulse → vesicles fuse → neurotransmitter into cleft → binds receptors → ion channels open → new potential, excitatory or inhibitory.
- 18Meninges from outside in: dura mater, arachnoid, pia mater.
- 19Forebrain: cerebrum, thalamus, hypothalamus. Hemispheres joined by corpus callosum.
- 20Cortex = grey matter (cell bodies); inner myelinated tracts = white matter.
- 21Hypothalamus: body temperature, eating, drinking; hypothalamic hormones.
- 22Limbic system + hypothalamus: sexual behaviour, emotions, motivation.
- 23Midbrain: cerebral aqueduct, corpora quadrigemina. Hindbrain: pons, cerebellum, medulla.
- 24Medulla: respiration, cardiovascular reflexes, gastric secretions. Brain stem = midbrain + pons + medulla.
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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.