Assoc. Prof. MUDr. Markéta Bébarová, Ph.D.
Department of Physiology, Faculty of Medicine, Masaryk University
Brain and behavior, 
environment of the neuron
This presentation includes only the most 
important terms and facts. Its content by 
itself is not a sufficient source of
information required to pass the
Neuroscience exam. 
Figures and tables re‐used from:
‐ Principles of Neural Science (5th ed.), Kandel et al. (2013)
‐ Medical Physiology (2nd ed.), Boron and Boulpaep (2012)
‐ Neuroscience (4th ed.), Purves et al. (2008)
‐ Medical Neurobiology (1st ed.), Mason (2011)
‐ Review of Medical Physiology (20th ed.), Ganong (2005)
‐ Atlas of Human Physiology (6th ed.), Silbernagl a Despopoulos (2004)
Functional regions of the CNS
Functional regions of the CNS
Functional regions of the brain cortex
Broadmann
52 areas
Methods for measurement of regional cerebral
blood flow, thus, of brain activity
PET (positron emission tomography)
- a substance labelled by radionuclides with a short half time
- the substance is injected, the increase and following decrease
of its concentration is evaluated by scintillation detectors
placed around the head
- e.g. labelled 2-deoxyglucose – its consumption is a good indicator of the flow
Functional regions of the brain
Functional regions of the brain
fMRI (functional magnetic resonance)
- better resolution
- reduced haemoglobin becomes paramagnetic, change the
signal emitted by blood, we can measure the amount of oxyand
deoxyhaemoglobin as an indicator of the blood flow
Functional regions of the brain
Methods for measurement of regional cerebral
blood flow, thus, of brain activity
Functional regions of the brain
Homeostasis
• is the process of ensuring that bodily variables stay 
within a preferred range
• endocrine, nervous, immune systems
Homeostasis – nervous system
• brain is „smart“ – when possible anticipate
challenges to homeostasis → all an cipatory 
homeostatic adjustments require intact forebrain
(voluntary reaction)
• unexpected challenges to homeostasis → met by 
largely unconscious reflexes mediated by the spinal 
cord and/or brainstem
Homeostasis – nervous system
• interactions with external environment require 
behavioural component as a function of the brain
• behaviour (from simple to complex) requires 
contribution of three main components:
sensory, executive, motivational
Goal directed behaviour
• energetic balance
• volume and osmolarity
• temperature
• performance
• strenghthen health
• reproduction
• defense
• ...........
Neuron
• approx. 1011 of nerve cells (glial cells 10 times frequent)
• the most consistent neuronal trait ‐ individuality
• neurons differ in location, morphology, connections, 
physiological characteristics
• cells within localized clusters (nuclei) or layers (laminae) 
often share many common characteristics
Most neurons share a group of traits: 
• derive from ectoderm
• four morphological regions – dendrites, body, axon, 
synaptic terminals
Most neurons share a group of traits: 
• four functional components – input, integrative, 
conductile, output
• generate electrical potentials
• communication with another neurons
Neuron
The law (doctrine) of dynamic polarization: 
Neuronal information flows in one direction  from the 
dendrites and the soma to the axon and synaptic 
terminals. (Cajal)
Glial cells
• CNS ‐ oligodendrocytes, astrocytes, microglial cells
• PNS ‐ Schwann cells
• critical for development of NS
CNS PNS
Myelin
Myelin insulates axons – rapid (saltatory) conduction of AP.
demyelination
Astrocytes
• metabolic functions: K+, pH, oxidative stress (GSH), 
energy storage (glycogen), glutamate‐glutamin shuttle
• modulation of synaptic activity, tissue repair
Cerebral
Compartments
Ganong´s Review of Medical Physiology, 23rd edition
Cerebral Circulation
Cerebral Circulation
• provides:
1) constant sufficient blood supply
2) dynamic blood redistribution
(metabolic hyperaemia)
(black-out during several seconds of the brain ischemia,
irreversible damage during several minutes)
Cerebral Circulation
• Anatomical specialities of cerebral circulation:
1) circulus arteriosus cerebri
(interconnection of main cerebral arteries by anastomoses)
(almost 1/2 of the vasal resistance falls on arteries
which are abundantly innervated)
3) very short arteriols
2) very high density of capillaries
(3000 – 4000 capillaries / mm2 od the grey matter)
 minimalization of diffuse distance for gases and
other substances
Cerebral Circulation
• Functional adaptation of cerebral circulation:
4) high reactivity on changes of CO2 concentration
1) high and stable blood flow
2) high O2 extraction
3) well developed autoregulation (myogenic and metabolic)
5) local vs. total hypoxia
6) innervation
Cerebral Circulation
Ganong´s Review of Medical Physiology, 23rd edition.
sympathetic system
Cerebral Circulation
• Special physical conditions of cerebral circulation:
1) solid cover of brain by skull
Monro-Kelli theory
 flow may be increased only by acceleration of the
blood flow, not by an increase of capacity of the
bloodstream
 Cushing reflex
2) gravity
orthostatic reaction (postural syncope)
Cerebral Circulation
Ganong´s Review of Medical Physiology, 23rd edition
• Blood-brain barrier
cerebral capillaries – tight inter-endothelial connections
Cerebral Circulation
• Blood-brain barrier
 lipophilic substances (O2, CO2, xenon; unbound
forms of steroid hormones)
By free diffusion:
 water (aquaporins; osmolality of blood and
cerebrospinal fluid is identical!)
 ions (e.g. H+, HCO3- vs. CO2 !)
By transcellular transport (regulated):
 glucose – the main source of energy for neurons
(free diffusion would be slow – accelerated by GLUT)
 transporters for thyroid hormones, some organic acids,
choline, precursors of nucleic acids, aminoacids, …
Cerebral Circulation
• Blood-brain barrier
• Functions:
- maintenance of constant composition of the neuron
environment
- protection of brain against endogenic and exogenic
toxins
- prevention of loss of neurotransmitters to the
bloodstream
Cerebrospinal fluid
- production -
rate of production: 450‐550 ml/day 
(70 % come from plexus choriodei)
circulating volume:  130‐150 ml
CSF pressure in supine position in 
lumbar region: 
70‐180 mmH2O
Cerebrospinal fluid
- composition -
Cerebrospinal fluid - circulation
Cerebrospinal fluid ‐ function
• mechanical and protective
• drainage
• homeostatic
• information transfer 
Cerebrospinal fluid ‐ function
• mechanical and protective
• drainage
• homeostatic
• information transfer 
Cerebral Circulation
• Paraventricular organs
 brain regions where the
blood-brain barrier is missing
(fenestrated capillaries)
Ganong´s Review of Medical
Physiology, 23rd edition
- secretion of polypeptides
(oxytocin, vasopressin, …),
- chemoreceptive zones (AP)
- osmoreceptive zones (OVLT)
Blood flow in brain ‐ methods
• global: Fick principle ‐ Kety method using inhaled nitrous 
oxide (N2O)
• Perfusion CT
• Invasive methods (local monitoring in neurosurgery):
flow: probe with thermistors 
pO2 
• magistral arteries ultrasound
• transcranial Doppler ultrasound
• PET, fMRI
Energy sources
• glucose (does not need insulin)
astrocytes GLUT 1 (→ lactate)
neurons GLUT 3
• under some conditions also:
ketone bodies: starvation and diabetes
• new‐borns also FFA during breastfeeding
Energy sources
• most of the energy is needed to maintain ion 
gradients across cell membranes and transmit 
electrical impulses
• part of glucose in neurons is converted to amino 
acids and lipids
• part of the total glucose is utilised by glial cells
Ammonium
• glutamate entering the brain takes up ammonia and 
leaves as glutamine
→ opposite to the reac on of kidney
• ammonium is very toxic for neural tissue
• hepatic encephalopathy