Brain Facts and Figures

Brain

Average Brain Weights (in grams) Species Weight (g) Species Weight (g) adult human 1,300 - 1,400 newborn human 350 - 400 sperm whale 7,800 fin whale 6,930 elephant 4,783 humpback whale 4,675 gray whale 4,317 killer whale 5,620 bowhead whale 2,738 pilot whale 2,670 bottle-nosed dolphin 1,500 - 1,600 walrus 1,020 - 1,126 Pithecanthropus Man 850 - 1,000 camel 762 giraffe 680 hippopotamus 582 leopard seal 542 horse 532 polar bear 498 gorilla 465 - 540 cow 425-458 chimpanzee 420 orangutan 370 California sea lion 363 manatee 360 tiger 263.5 lion 240 grizzly bear 234 pig 180 jaguar 157 sheep 140 baboon 137 rhesus monkey 90-97 dog (beagle) 72 aardvark 72 beaver 45 shark (great white) 34 shark (nurse) 32 cat 30 porcupine 25 squirrel monkey 22 marmot 17 rabbit 10-13 platypus 9 alligator 8.4 squirrel 7.6 opossum 6 flying lemur 6 fairy anteater 4.4 guinea pig 4 ring-necked pheasant 4.0 hedgehog 3.35 tree shrew 3 fairy armadillo 2.5 owl 2.2 grey partridge 1.9 rat (400 g body weight) 2 hamster 1.4 elephant shrew 1.3 house sparrow 1.0 european quail 0.9 turtle 0.3-0.7 bull frog 0.24 viper 0.1 goldfish 0.097 green lizard 0.08 Reference for many of these brain weights:

Blinkov, S.M. and Glezer, I.I. The Human Brain in Figures and Tables. A Quantitative Handbook, New York: Plenum Press, 1968. Demski, L.S. and Northcutt, R.G. The brain and cranial nerves of the white shark: an evolutionary perspective. In Great White Sharks. The Biology of Carcharodon carcharias, San Diego: Academic Press, 1996. Nieuwenhuys, R., Ten Donkelaar, H.J. and Nicholson, C. The Central Nervous System of Vertebrates. Vol. 3, Berlin: Springer, 1998. Berta, A., et al. Marine Mammals. Evolutionary Biology, San Diego: Academic Press, 1999. Mink, J.W., Blumenschine, R.J. and Adams, D.B. Ratio of central nervous system to body metabolism in vertebrates: its constancy and functional basis. Am. J. Physiology, 241:R203-R212, 1981. Rehkamper, G., Frahm, H.D. and Zilles, K. Quantitative development of brain and brain structures in birds (Galliformes and Passeriforms) compared to that in mammals (Insectivores and Primates). Brain Beh. Evol., 37:125-143, 1991. Ridgway, S.H. and Harrison, S., Handbook of Marine Mammals, Vol. 3, London: Academic Press, 1985. Shoshani, J., Kupsky, W.J. and Marchant, G.H., Elephant brain. Part I: Gross morphology functions, comparative anatomy, and evolution, Brain Res. Bulletin, 70:124-157, 2006.

Intracranial contents by volume (1,700 ml, 100%): brain = 1,400 ml (80%); blood = 150 ml (10%); cerebrospinal fluid = 150 ml (10%) (from Rengachary, S.S. and Ellenbogen, R.G., editors, Principles of Neurosurgery, Edinburgh: Elsevier Mosby, 2005)

Average number of neurons in the brain = 100 billion (Source: Various textbooks.)

Average number of neurons in the brain = 86 billion (Frederico Azevedo et al., Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain. J. Comp. Neurol., 513: 532-541, 2009.)

The octopus nervous system has about 500,000,000 neurons, with two-thirds of these neurons located in the arms of the octopus. ( from Hochner B, Shomrat T, Fiorito G., The octopus: a model for a comparative analysis of the evolution of learning and memory mechanisms. Biol Bull. 2006 Jun;210(3):308-317.

Number of neurons in honey bee brain = 950,000 ( from Menzel, R. and Giurfa, M., Cognitive architecture of a mini-brain: the honeybee, Trd. Cog. Sci., 5:62-71, 2001.)

Number of neurons in Aplysia nervous system = 18,000-20,000

Number of neurons in each segmental ganglia in the leech = 350

Volume of the brain of a locust = 6mm3 (from The Neurobiology of the Insect Brain, Burrows, M., 1996)

Ratio of the volume of grey matter to white matter in the cerebral hemipheres (20 yrs. old) = 1.3 (Miller, A.K., Alston, R.L. and Corsellis, J.A., Variation with age in the volumes of grey and white matter in the cerebral hemispheres of man: measurements with an image analyser, Neuropathol Appl Neurobiol., 6:119-132, 1980)

Ratio of the volume of grey matter to white matter in the cerebral hemipheres (50 yrs. old) = 1.1 (Miller et al., 1980)

Ratio of the volume of grey matter to white matter in the cerebral hemipheres (100 yrs. old) = 1.5 (Miller et al., 1980)

% of cerebral oxygen consumption by white matter = 6%

% of cerebral oxygen consumption by gray matter = 94%

Ratio of glial cells to neurons in the brain = 1:1 (Reference 1 and Reference 2)

(For more information about the number of neurons in the brain, see R.W. Williams and K. Herrup, Ann. Review Neuroscience, 11:423-453, 1988)

Number of neocortical neurons (females) = 19.3 billion (Pakkenberg, B., Pelvig, D., Marner,L., Bundgaard, M.J., Gundersen, H.J.G., Nyengaard, J.R. and Regeur, L. Aging and the human neocortex. Exp. Gerontology, 38:95-99, 2003 and Pakkenberg, B. and Gundersen, H.J.G. Neocortical neuron number in humans: effect of sex and age. J. Comp. Neurology, 384:312-320, 1997.)

Number of neocortical neurons (males) = 22.8 billion (Pakkenberg et al., 1997; 2003)

Average loss of neocortical neurons = 85,000 per day (~31 million per year) (Pakkenberg et al., 1997; 2003)

Average loss of neocortical neurons = 1 per second (Pakkenberg et al., 1997; 2003)

Average number of neocortical glial cells (young adults ) = 39 billion (Pakkenberg et al., 1997; 2003)

Average number of neocortical glial cells (older adults) =36 billion (Pakkenberg et al., 1997; 2003)

Number of neurons in cerebral cortex (rat) = 21 million (Korbo, L., et al., J. Neurosci Methods, 31:93-100, 1990)

Length of myelinated nerve fibers in brain = 150,000-180,000 km (Pakkenberg et al., 1997; 2003)

Number of synapses in cortex = 0.15 quadrillion (Pakkenberg et al., 1997; 2003)

Difference number of neurons in the right and left hemispheres = 186 million MORE neurons on left side than right side (Pakkenberg et al., 1997; 2003)

Proportion by Volume (%) Rat Human Cerebral Cortex 31 77 Diencephalon 7 4 Midbrain 6 4 Hindbrain 7 2 Cerebellum 10 10 Spinal Cord 35 2 (Reference: Trends in Neurosciences, 18:471-474, 1995)

Composition of Brain and Muscle Skeletal Muscle (%) Whole Brain (%) Water 75 77 to 78 Lipids 5 10 to 12 Protein 18 to 20 8 Carbohydrate 1 1 Soluble organic substances 3 to 5 2 Inorganic salts 1 1 (Reference: McIlwain, H. and Bachelard, H.S., Biochemistry and the Central Nervous System, Edinburgh: Churchill Livingstone, 1985)

Total surface area of the cerebral cortex = 2,500 cm2 (2.5 ft2; A. Peters, and E.G. Jones, Cerebral Cortex, 1984 )

Total surface area of the cerebral cortex (lesser shrew) = 0.8 cm2

Total surface area of the cerebral cortex (rat) = 6 cm2

Total surface area of the cerebral cortex (cat) = 83 cm2

Total surface area of the cerebral cortex (African elephant) = 6,300 cm2

Total surface area of the cerebral cortex (Bottlenosed dolphin) = 3,745 cm2 (S.H. Ridgway, The Cetacean Central Nervous System, p. 221)

Total surface area of the cerebral cortex (pilot whale) = 5,800 cm2

Total surface area of the cerebral cortex (false killer whale) = 7,400 cm2

(Reference for surface area figures: Nieuwenhuys, R., Ten Donkelaar, H.J. and Nicholson, C., The Central nervous System of Vertebrates, Vol. 3, Berlin: Springer, 1998)

Total number of neurons in cerebral cortex = 10 billion ( from G.M. Shepherd, The Synaptic Organization of the Brain, 1998, p. 6) . However, C. Koch lists the total number of neurons in the cerebral cortex at 20 billion (Biophysics of Computation. Information Processing in Single Neurons, New York: Oxford Univ. Press, 1999, page 87).

Total number of synapses in cerebral cortex = 60 trillion (yes, trillion) (from G.M. Shepherd, The Synaptic Organization of the Brain, 1998, p. 6). However, C. Koch lists the total synapses in the cerebral cortex at 240 trillion (Biophysics of Computation. Information Processing in Single Neurons, New York: Oxford Univ. Press, 1999, page 87).

Percentage of total cerebral cortex volume (human): frontal lobe = 41%; temporal lobe = 22%; parietal lobe = 19%; occipital lobe = 18%. (Kennedy et al., Cerebral Cortex, 8:372-384, 1998.)

Number of cortical layers = 6

Thickness of cerebral cortex = 1.5-4.5 mm

Thickness of cerebral cortex (Bottlenosed dolphin) = 1.3-1.8 mm (S.H. Ridgway, The Cetacean Central Nervous System, p. 221)

EEG - beta wave frequency = 13 to 30 Hz

EEG - alpha wave frequency = 8 to 13 Hz

EEG - theta wave frequency = 4 to 7 Hz

EEG - delta wave frequency = 0.5 to 4 Hz

World record, time without sleep = 264 hours (11 days) by Randy Gardner in 1965. Note: In Biopsychology (by J.P.J. Pinel, Boston: Allyn and Bacon, 2000, p. 322), the record for time awake is attributed to Mrs. Maureen Weston. She apparently spent 449 hours [18 days, 17 hours] awake in a rocking chair. The Guinness Book of World Records [1990] has the record belonging to Robert McDonald who spent 453 hours, 40 min in a rocking chair.

Time until unconsciousness after loss of blood supply to brain = 8-10 sec

Time until reflex loss after loss of blood supply to brain = 40-110 sec

Rate of neuron growth (early pregnancy) = 250,000 neurons/minute

Length of spiny terminals of a Purkinje cell = 40,700 micron

Number spines on a Purkinje cell dendritic branchlet = 61,000

Surface area of cerebellar cortex = 1,590 cm2 ( from Sereno et al., The human cerebellum has almost 80% of the surface area of the neocortex, PNAS, 117:19538-19543, 2020

Weight of adult cerebellum = 150 grams (Afifi, A.K. and Bergman, R.A., Functional Neuroanatomy, New York: McGraw-Hill, 1998)

Number of Purkinje cells = 15-26 million

Number of synapses made on a Purkinje cell = up to 200,000

Weight of hypothalamus = 4 g

Volume of suprachiasmatic nucleus = 0.3 mm3

Number of fibers in pyramidal tract above decussation = 1,100,000

Number of fibers in corpus callosum = 200,000,000 (Lunders, E., Thompson, P.M. and Toga, A.W., The Development of the Corpus Callosum in the Healthy Human Brain, The Journal of Neuroscience, 30:10985-10990, 2010.)

Area of the corpus callosum (midsagittal section) = 6.2 cm2

Species Cerebellum Weight (grams) Body Weight (grams) Mouse 0.09 58 Bat 0.09 30 Flying Fox 0.3 130 Pigeon 0.4 500 Guinea Pig 0.9 485 Squirrel 1.5 350 Chinchilla 1.7 500 Rabbit 1.9 1,800 Hare 2.3 3,000 Cat 5.3 3,500 Dog 6.0 3,500 Macaque 7.8 6,000 Sheep 21.5 25,000 Bovine 35.7 300,000 Human 142 60,000 Sultan, F. and Braitenberg, V. Shapes and sizes of different mammalian cerebella. A study in quantitative comparative neuroanatomy. J. Hirnforsch., 34:79-92, 1993.

Total volume of cerebrospinal fluid (adult) = 125-150 ml

Total volume of cerebrospinal fluid (infant) = 50 ml (Aghababian, R., Essentials of Emergency Medicine, 2006)

Turnover of entire volume of cerebrospinal fluid = 3 to 4 times per day (from Kandel et al., 2000, p. 1296)

Rate of production of CSF = 0.35 ml/min (500 ml/day) (from Kandel et al., 2000, p. 1296)

pH of cerebrospinal fluid = 7.33 (from Kandel et al., 2000, p. 1296)

Specific gravity of cerebrospinal fluid = 1.007

Color of normal CSF = clear and colorless

White blood cell count in CSF = 0-3 per mm3

Red blood cell count in CSF = 0-5 per mm3

Normal intracranial pressure = 150 - 180 mm of water

Composition of Serum and Cerebrospinal Fluid (CSF) CSF Serum Water (%) 99 93 Protein (mg/dl) 35 7000 Glucose (mg/dl) 60 90 Osmolarity (mOsm/l) 295 295 Na (meq/l) 138 138 K (meq/l) 2.8 4.5 Ca (meq/l) 2.1 4.8 Mg (meq/l) 0.3 1.7 Cl (meq/l) 119 102 pH 7.33 7.41 (Reference: Fishman, R.A. Cerebrospinal Fluid in Disease of the Nervous System. Philadelphia: Saunders, 1980)

Number of cranial nerves = 12

I- olfactory

II- optic



Number of fibers in human optic nerve = 1,200,000

Number of fibers in cat optic nerve = 119,000

Number of fibers in albino rat optic nerve = 74,800

Length of optic nerve = 50 mm (Reference: Kanski, J.J., Clinical Ophthalmology, 6th ed., Edinburgh: Elsevier, 2007.)



Number of fibers in oculomotor nerve = 25,000-35,000



Number of fibers in trochlear nerve = 2,000-3,500

Number of neurons in nucleus of the trochlear nerve = 2,000-3,500



Number of fibers in motor root of trigeminal nerve = 8,100

Number of fibers in sensory root of trigeminal nerve = 140,000



Number of fibers in abducens nerve (at exit from brain stem) = 3,700



Number of fibers in facial nerve (at exit from brain stem) = 9,000-10,000

Length of nucleus of the facial nerve = 2 to 5.6 mm

Number of neurons in nucleus of the facial nerve = 7,000



Length of dorsal motor nucleus of the vagus nerve = 10 mm



Number of neurons in nucleus of the hypoglossal nerve = 4,500-7,500

Length of nucleus of the hypoglossal nerve = 10 mm



Spinal Cord

Number of neurons in human spinal cord = 1 billion (from Kalat, J.W., Biological Psychology, 6th Edition, 1998, page 24)

Length of human spinal cord = 45 cm (male); 43 cm (female)

Length of human vertebral column (male) = 71 cm

Length of human vertebral column (female) = 61 cm

Length of cat spinal cord = 34 cm

Length of rabbit spinal cord = 18 cm

Length of the filum terminale = 15 cm

Cross sectional area of the spinal cord (C2 level) = 110 mm2

Cross sectional area of the spinal cord (C4 level) = 122 mm2

Cross sectional area of the spinal cord (C5 level) = 78 mm2

Cross sectional area of the spinal cord (C7 level) = 85 mm2

(Reference: Watson, C., Paxinos, G. and Kayalioglu, G., The Spinal Cord, Amsterdam: Elsevier, 2009)

Weight of human spinal cord = 35 g

Weight of rabbit spinal cord = 4 g

Weight of rat spinal cord (400 g body weight) = 0.7 g

Maximal circumference of cervical enlargement = 38 mm

Maximal circumference of lumbar enlargement = 35 mm

Pairs of Spinal Nerves = 31

Number of spinal cord segments (human)= 31



8 cervical segments

12 thoracic segments

5 lumbar segments

5 sacral segments

1 coccygeal segment



8 cervical segments

13 thoracic segments

6 lumbar segments

4 sacral segments

3 coccygeal segments



Sensory Apparatus

Audition

(Hearing: Its Physiology and Pathophysiology, A.R. Moller, Amsterdam: Elsevier, 2006)

(Hearing. Its Physiology and Pathophysiology, A.R. Moller, San Diego, Academic Press, 2000.)

(Hearing. Its Physiology and Pathophysiology, A.R. Moller, San Diego, Academic Press, 2000.)

(Hearing: Its Physiology and Pathophysiology, A.R. Moller, Amsterdam: Elsevier, 2006)

(Hearing: Its Physiology and Pathophysiology, A.R. Moller, Amsterdam: Elsevier, 2006)

(Northern, J.L. and Downs, M.P., Hearing in Children, 5th edition, Philadelphia: Lippincott Williams & Wilkins, 2002.)

(Northern, J.L. and Downs, M.P., Hearing in Children, 5th edition, Philadelphia: Lippincott Williams & Wilkins, 2002.)

(Guyton, A.C., Textbook of Medical Physiology, 1986)

(Hearing range reference: Discover Science Almanac, New York: Hyperion, 2003)

Diameter of external auditory meatus (ear canal)= 0.7 cm

Weight of malleus = 23 mg; length of malleus = 8-9 mm

Weight of incus = 30 mg; dimensions of incus = 5 mm by 7 mm

Weight of stapes = 3-4 mg; dimensions of stapes = 3.5 mm high, 3 mm long, 1.4 mm wide

Malleus, incus and stapes references: Gelfand, S.A. Hearing: An Introduction to Psychological and Physiological Acoustics, 4th edition, New York: Marcel Dekker, 2004.

Length of cochlea = 35 mm

Width of cochlea = 10 mm

Number of turns in the cochlea = 2.2-2.9

Length of basilar membrane = 25-35 mm

Width of basilar membrane = 150 microns (at base of cochlea) (Hearing. Its Physiology and Pathophysiology, A.R. Moller, San Diego, Academic Press, 2000.)

Auditory Pain Threshold = 130 db

Threshold for hearing damage = 90 db for an extended period of time

Decibel Sound Scale Decibels Sound 180 Rocket launching pad 140 Jet plane 140 Gunshot blast 120 Automobile horn 130 Pain threshold 120 Discomfort 90 Subway 80 Noisy Restaurant 75 Busy traffic 66 Normal conversation 50 Average home 30 Soft whisper Source: Lee, K.J., Essential Otolaryngology, 8th edition, New York: McGraw-Hill, 2003.

Taste

(From: Farbman, A.I., Taste Bud, in G. Adelman, eds., Encyclopedia of Neuroscience, 1987)

(From: Farbman, A.I.)

(Boron, W.F. and Boulpaep, E.L., Medical Physiology. A Cellular and Molecular Approach, Philadelphia: Saunders, 2003)

Smell

(Shier, D., Butler, J. and Lewis, R. Hole's Human Anatomy & Physiology, Boston: McGraw Hill, 2004)

(Shier, D., Butler, J. and Lewis, R. Hole's Human Anatomy & Physiology, Boston: McGraw Hill, 2004)

(Bear, M.F., Connors, B.W. and Pradiso, M.A., Neuroscience: Exploring the Brain, 2nd edition, Baltimore: Lippincott Williams and Wilkins, 2001, p. 269)

(Shier, D., Butler, J. and Lewis, R. Hole's Human Anatomy & Physiology, Boston: McGraw Hill, 2004)

(Bradshaw, J., Behavioral biology, in The Waltham Book of Dog and Cat Behaviour, ed. C. Thorne, Oxford: Pergamon Press, 1992)

(Boron and Boulpaep, 2003)

(Kavoi, B.M. and Jameela, H., Comparative morphometry of the olfactory bulb, tract, and stria in the human, dog, and goat. Int. J. Morphol. 29, 939-946, 2011.)

(Kavoi, B.M. and Jameela, H., Comparative morphometry of the olfactory bulb, tract, and stria in the human, dog, and goat. Int. J. Morphol. 29, 939-946, 2011.)

(Kavoi, B.M. and Jameela, H., Comparative morphometry of the olfactory bulb, tract, and stria in the human, dog, and goat. Int. J. Morphol. 29, 939-946, 2011.)

(McGann, J.P., Poor human olfaction is a 19th-century myth, Science, Volume 356 Issue 6338, eaam7263 DOI: 10.1126/science.aam7263, 2017)

Vision

(from Riordan-Eva, P. and Whitcher, J.P., Vaughan & Asbury's General Ophthalmology, 17th ed., New York: Lange Medical Books, 2008)

(from Riordan-Eva and Whitcher, 2008)

(Schiffman, H.R., Sensation and Perception. An Integrated Approach, New York: John Wiley and Sons, Inc., 2001)

(Foster, C.S., Azar, D.T. and Dohlman, C.H. Smolin and Thoft's The Cornea. Scientific Foundations and Clinical Practice, 4th edition, Philadelphia: Lippincott Williams & Wilkins, 2005)

(from Riordan-Eva and Whitcher, 2008)

(from Riordan-Eva and Whitcher, 2008)

(from Riordan-Eva and Whitcher, 2008)

(from Riordan-Eva and Whitcher, 2008)

(from Riordan-Eva and Whitcher, 2008)

Touch

(Source: Schiffman, H.R., Sensation and Perception. An Integrated Approach, New York: John Wiley and Sons, Inc., 2001)

(Source: Schiffman, H.R., Sensation and Perception. An Integrated Approach, New York: John Wiley and Sons, Inc., 2001)

Neurons

Mass of a large sensory neuron = 10-6gram ( from Groves and Rebec, Introduction to Biological Psychology, 3rd edition, Dubuque: Wm.C. Brown Publ., 1988 )

Number of synapses for a "typical" neuron = 1,000 to 10,000

Diameter of neuron = 4 micron (granule cell) to 100 micron (motor neuron in cord)

Diameter of neuron nucleus = 3 to 18 micron

Length of Giraffe primary afferent axon (from toe to neck) = 15 feet

Resting potential of squid giant axon = -70 mV

Conduction velocity of action potential = 0.6-120 m/s (1.2-250 miles/hr)

Single sodium pump maximum transport rate = 200 Na ions/sec; 130 K ions/sec

Typical number of sodium pumps = 1000 pumps/micron2 of membrane surface ( from Willis and Grossman, Medical Neurobiology, Mosby, St. Louis, 1981, p. 36)

Total number of sodium pumps for a small neuron = 1 million

Density of sodium channels (squid giant axon) = 300 per micron2 ( from Hille, B., Ionic Channels of Excitable Membranes, Sinauer, Sunderland, 1984, p. 210.)

Number of voltage-gated sodium channels at each node = 1,000 to 2,000 per micron2 ( from Nolte, J., The Human Brain, Mosby, 1999, p. 163.)

Number of voltage-gated sodium channels between nodes = 25 per micron2 ( from Nolte, J., The Human Brain, Mosby, 1999, p. 163.)

Number of voltage-gated sodium channels in unmyelinated axon = 100 to 200 per micron2 ( from Nolte, J., The Human Brain, Mosby, 1999, p. 163.)

Diameter of ion channel = 0.5 nanometer (Breedlove et al., Biological Psychology, 2007)

Diameter of microtubule = 20 nanometer

Diameter of microfilament = 5 nanometer

Diameter of neurofilament = 10 nanometer

Thickness of neuronal membrane = 5 nanometer (Breedlove et al., Biological Psychology, 2007)

Thickness of squid giant axon membrane = 50-100 A

Membrane surface area of a typical neuron = 250,000 um2 (Bear et al., 2001)

Membrane surface area of 100 billion neurons = 25,000 m2, the size of four soccer fields (Bear, M.F., Connors, B.W. and Pradiso, M.A., Neuroscience: Exploring the Brain, 2nd edition, Baltimore: Lippincott Williams and Wilkins, 2001, p. 97)

Typical synaptic cleft distance = 20-40 nanometers across (from Kandel et al., 2000, p. 176)

% neurons stained by the Golgi method = 5%

Slow axoplasmic transport rate = 0.2-4 mm/day (actin, tubulin)

Intermediate axoplasmic transport rate = 15-50 mm/day (mitochondrial protein)

Fast axoplasmic transport rate = 200-400 mm/day (peptides, glyolipids)

Number of molecules of neurotransmitter in one synaptic vesicle = 5,000 (from Kandel et al., 2000, p. 277)

Diameter of synaptic vesicle = 50 nanometer (small); 70-200 nanometer (large)

Diameter of neurofilament = 7 - 10 nm

Diameter of microtubule = 25 nm

Internodal Length = 150 - 1500 microns (depends on fiber diameter)

% composition of myelin = 70-80% lipid; 20-30% protein

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Ion Concentration (mM) - SQUID NEURON Intracellular Extracellular Potassium 400 20 Sodium 50 440 Chloride 40-150 560 Calcium 0.0001 10 Ion Concentration (mM) - MAMMALIAN NEURON Intracellular Extracellular Potassium 140 5 Sodium 5-15 145 Chloride 4-30 110 Calcium 0.0001 1-2 Data from Purves et al., Neuroscience, Sunderland: Sinauer Associates, 1997.

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Neurotoxins

Blood Supply