Chapter 1 - In multipolar and bipolar cells, the cell body also receives
synapses and part of the input zone.
Structure/actions of the brain can alter mind and behavior, which can in turn modify structures/actions of the brain. (3) Unipolar neurons - single axons that branch into an input zone
- Brain coordinates and controls behavior via phrenology (= the assumption that the cerebral cortex consists of with dendrites and an output zone - common for transmitting
separate functional areas, in which each area is responsible for a behavioral faculty, like love or perception. touch information from the body into the spinal cord.
Brain contains about 86 billion neurons, which each contact many other cells at synapses. Three types of neurons:
- Axons (= a specialized extension of neurons) produce electrical impulses. (1) Motor neurons - neurons that govern movements - long axons
reaching out to synapse on muscles, causing them to contract in
Charles Darwin’s theory of evolution emphasizes: response to commands from the brain.
(1) the continuity of behavior and biological processes among species because of our common ancestry (2) Sensory neurons - long axons carrying messages from the periphery
(2) species-specific differences in behavior and biology, which evolved as adaptations to different environments. back to the spinal cord and brain.
- Conserved characteristics = features that come from a shared ancestor. (3) Interneurons - neurons receiving information from other neurons,
process it, and pass the integrated information to other neurons -
Ontogeny = process by which an individual changes in majority of neurons in the brain.
the course of its life-time. - Have short axons compared to sensory and motor neurons.
- Particular behavioral changes during ontogeny
may reveal the functions and mechanisms. Larger neuron = more complex in- and output = greater distances = more
rapid information convey.
Three approaches to understand the relationship
between brain and behavior: Arborization (= elaborate branching) of dendrites indicates complexity of
(1) somatic intervention - alteration of a structure/ the neuron’s information-processing function.
function of the brain/body to see how this - More arborization = more synaptic inputs.
alteration changes behavior.
- Somatic intervention = independent variable, A synapse has three principal components:
behavioral effect = dependent variable (1) Presynaptic membrane of the axon terminal of the presynaptic neuron
(2) behavioral intervention - intervention in behavior/ - Contains synaptic vesicles with neurotransmitters (= specialized chemical substances) used to
experience of an organism to look at resulting changes in the body structure/function. communicate with postsynaptic neurons.
- Behavior = independent variable, change in body = dependent variable - After electrical activity, vesicle fuses with the presynaptic membrane and releases neurotransmitters into
(3) correlation - finding the extent to which a given body measure varies with a given behavioral measure. the synaptic cleft.
Relations between brain and behavior are reciprocal (= each affects the other in an ongoing cycle of bodily and (2) Synaptic cleft - separates the presynaptic and postsynaptic neurons
behavior interactions. (3) Postsynaptic membrane on the surface of the dendrite or cell body of the postsynaptic neuron
- After diffusion across the cleft, released neurotransmitters react with postsynaptic receptors (= specialized
Neuroplasticity = ability of the brain, in development and adulthood, to be changed by environment and experience. protein molecules that capture and react to neurotransmitter molecules).
- Experience can affect the number or size of neurons, or the number or size of connections between neurons. - Postsynaptic membrane has high density of receptors.
- Social experience affects brain structure.
- Hebbian synapse = neurons strenghten their connections through use. Brain tissue can be visualized by histology using:
(1) Nissl stain - outlines all cell bodies
Reductionism = analysis on a simpler level of organization than that of the structure/function to be explained. - Dyes are attracted to RNA distribution within the cell.
- Able to measure cell body size and density of the cell in
Initially, Aristotle believed that the brain was a cooling unit for hot blood from the heart. Later, Descartes proposed particular regions.
the concept of spinal reflexes and neural pathways, until scientists came up with the concept of duality (= a (2) Golgi stains - labels a small minority of neurons in a sample.
nonmaterial soul and a material body). - Reveals fine details of cell structure like branching of
dendrites/axons
Consciousness = the personal, private awareness of our emotions, intentions, thoughts, and movements and of the - Useful for quantifying types/precise shape of neurons in
sensations that impinge upon us. a region.
(3) Autoradiography - highlighting specific brain regions where
the drug has become selectively concentrated.
(4) Immunohistochemistry (IHC) - creation of antibodies
Chapter 2 against a protein of interest
Neurons = tiny, discrete information-processing units, receiving inputs from other cells, integrating those inputs, and - Fluorescent antibodies seek out and attach to target
then distributing the processed information to other neurons. proteins in neurons in a brain slice, selectively revealing distribution of neurons making target protein.
- Cajal - even though neurons come very close to each other (contiguous), there is a tiny gap that separates them. (5) In situ hybridization - labels only neurons in which a gene of interest has been turned on
- Neuron doctrine proposed that (1) cells of the brain are independent from each other structurally, - Uses radioactively labeled lengths of nucleic acid (RNA/DNA)
metabolically, and functionally, and (2) information is transmitted between neurons via tiny gaps (= synapses). (6) Tract tracers - pattern of connections between neurons rather than cellular structure.
- Tract tracers = substances that are taken up by neurons and transported over the routes of their axons.
Almost all neurons have four distinct functional zones related to information processing: - 2 ways of transport:
(1) Input zone - (mainly) dendrites receive information from other neurons across synapses. - Anterograde labelling - tract tracer injected near dendrites and cell bodies of a region of
(2) Integration zone - cell body combines information that the neuron receives to determine whether to send a interest, where it will be taken up and transported to the tips of the axons, thus revealing the
signal of its own. targets of the neurons in the region under study.
(3) Conduction zone - axon leads away from the cell body, carrying the electrical signals away from the cell body. - Retrograde labelling - tract tracer injected into a region of interest, taken up by axon terminals and
- Before the end, the axon may split into multiple branches (= axon collaterals). transported back to their originating cell bodies, thus revealing sources of innervation of region.
(4) Output zone - axon terminals (= specialized swellings at the ends of the axon) transmit the neuron’s activity - Some tract tracers work trans-synaptically (= jump backward across synapses and work
across synapses to other cells. their way toward higher levels of the nervous system, leaving visible label along the way).
3 principal types of nerve cells, based on shape of cell bodies, dendrites, and axons for particular information Synapse configuration on a neuron’s dendrites and cell body is constantly changing, and dendrites constantly remodel
processing: shape in response to new patterns of synaptic activity and the formation of new neural circuits (= neural plasticity).
(1) Multipolar neurons - many dendrites and single axon - Number and structure of dendritic spines rapidly alter in response to neural plasticity.
(2) Bipolar neurons - single dendrite and single axon with soma in the middle - common in sensory systems. - Dendritic spines = outgrowths of dendrites on many neurons, which effectively increase surface area of
dendrites, allowing for extra synaptic contacts.
,Axon arises from the axon hillock (= a cone-shaped projection of the cell body), which is the neuron’s integration zone (2) trochlear nerve - for moving eye
- integrates information from all synapses on the neuron’s dendrites and soma, then converting the processed (3) abducens nerve - for moving eye
information into a code of electrical impulses, which carry the neuron’s message down the axon towards its target. (4) spinal accessory nerves - for
- Neurons mostly have one axon, which often divides into several axon collaterals, allowing the neuron to control of neck muscles
innervate a number of postsynaptic cells. (5) hypoglossal nerves - to control tongue
- Other cranial nerves have both
Cell body manufactures various materials, e.g enzymes/structural proteins, under guidance of DNA in cell nucleus. sensory and motor functions, e.g.
- Important substances needed at the axon terminals will be loaded onto transport vesicles (= hollow spheres trigeminal nerve for chewing
with specialized leglike motor proteins on their outer surface). - Spinal nerves - 31 pairs - each consists of
- If activated, motor proteins literally walk the vesicles through the inside of the axon between the cell fusion of two distinct branches (= roots) that
body and the axon terminals (= axonal transport). are functionally different.
- Axonal transport can work in both directions: - Dorsal root (back) = sensory projections
- Anterograde transport = transport of material towards the axon terminals from the body to the spinal cord
- Retrograde transport = transport of materials back to the cell body for recycling. - Ventral root (front) = motor projections from the spinal cord to the muscles
- 8 cervical (neck), 12 thoracic (thorax), 5 lumbar (lower back), 5 sacral (pelvic), 1 coccygeal segment
Axon have 2 different routes for transmission/transportation: (2) Autonomic nervous system - nerves that primarily control the viscera (= internal organs).
(1) rapid transmission of electrical signals along the outside of the axon - Autonomic ganglia support this control of organs and found in various locations outside the CNS.
(2) much slower transportation of substances inside the axon, to and from the axon terminals. - Autonomic neurons within brain and spinal cord send their axons to innervate neurons in ganglia, which
in turn send their axons to innervate all major organs.
Glial cells communicate with each other and with neurons, and can directly affect neuronal functioning by providing - Central neurons that innervate ganglia = preganglionic autonomic neurons.
neurons with raw materials and chemical signals that alter neuronal structure and excitability. - Ganglionic neurons that innervate body = postganglionic neurons.
- Glial cells continue to divide throughout life (in contrast to neurons), and can therefore form tumors in brain.
- 4 types of glial cells: Three major divisions autonomic nervous system:
(1) Astrocytes - receive synapses directly from neurons, surround and monitor activity of nearby neuronal (1) Sympathetic nervous system - prepares body for fight-flight response (meaning increased BP & HR)
synapses. - Preganglionic cells in thoracic and lumbar regions - send their axons only a short distance, innervating
- Cross talk among astrocytes and neighboring neurons causes a ‘tripartite synapse’ in which the sympathetic chain of autonomic ganglia that runs along each side of the spinal column.
astrocytes directly participate in the transmission of information between neurons. - Uses norepinephrine
- Involved in formation of new synapses as well as pruning of surplus synapses. (noradrenaline) to accelerate
- Can directly influence local brain chemistry activity.
(2) Microglial cells - migrate to sites of injury/disease to remove debris from injured or dead cells. (2) Parasympathetic nervous system - helps
- Key component of neural pain systems body to relax and recuperate - rest and
(3) Oligodendrocytes (CNS) and Schwann cells (PNS) - important for myelination digest response.
- Myelin = a fatty insulating substance wrapped around sections of the axons in multiple layers. - Parasympathetic axons travel a longer
- Nodes of Ranvier = small uninsulated patches of axonal membrane. distance before terminating in
- Myelination causes a large increase in the speed with which electrical signals pass down the axon, parasympathetic ganglia, because
jumping from one node to the next (= saltatory conduction). parasympathetic ganglia are not
- Oligodendrocytes provide chemical signals (= trophic signals) to enhance structural integrity of axons. collected in a chain as sympathetic
ganglia are.
Brain damage will lead to: - Uses acetylcholine to slow down
- Swelling of astrocytes = edema = damaged neurons, causing many symptoms of brain injuries. activity.
- Increased microglia = damaging inflammation response. (3) Enteric nervous system - maintaining
- Loss of insulating myelin sheath from axons in various regions of the brain - development of MS. fluid and nutrient balances in body by
- Schizophrenia if all three kind of glial cells are altered. regulating digestive activities of gut.
- Local network of sensory and motor
Nervous system is divided into: neurons to regulate functioning of
(1) central nervous system - brain and spinal cord gut, under the control of CNS.
(2) peripheral nervous system - all nervous system parts that are outside the bony skull and spinal column
- consists of nerves, among which motor nerves (transmit information from brain to the tissues) and Two cerebral hemispheres are part of the
sensory nerves (transmit information from sensors to brain) cerebral cortex (= elaborate folding of thick sheet
of brain tissue), mostly made up of neuronal cell
The peripheral nervous system has two distinct systems: bodies, dendrites, and axons.
(1) Somatic nervous system - consists of nerves that - Gyri are ridges, sulci are grooves.
interconnect brain and major muscles/sensory - Folded cortex greatly increases amount of
systems of the body. cortex in the skull.
- Main pathway through which the brain - 4 major cortical regions:
controls movement and receives sensory (1) frontal lobe - important for
information from head and body. movement and high-level cognition
- Contains cranial and spinal nerves. (2) parietal lobe - receive sensory information from body and participate in spatial cognition
- Cranial nerves - 12 pairs, with one left- (3) temporal lobe - receive/process auditory information for hearing
and right-sided nerve in each pair (4) occipital lobe - receive/process information from eyes for vision.
- Three cranial nerves for exclusively - Sylvian fissue - divides temporal lobe from the other regions of the hemisphere
sensory pathways to the brain: - Central sulcus - divides frontal and parietal lobes.
(1) olfactory nerve - for smell - Postcentral gyrus (posterior to central sulcus) involved in sense of touch
(2) optic nerve - for visual information - Precentral gyrus (anterior to central sulcus) involved in motor control
(3) vestibulocochlear nerve - for hearing
and balance Corpus callosum (= composed of bundled axons between two hemispheres) - enables communication between right
- Five cranial nerves for exclusively and left cerebral hemispheres and allows brain to act as a single entity during complex processing.
motor pathways from the brain: - Gray matter on exterior - composed of neuronal cell bodies and dendrites - receive and process information.
(1) oculomotor nerve - for moving eye - White matter on interior - composed of axonal fiber tracts with myelin - transmit information to other
locations.
, Medial - towards the middle The brain is bilaterally symmetrical aside from
Lateral - towards the side the corpus callosum, pineal gland and pituitary.
Ipsalateral - if second location is on same side of body - Most structures are paired in left/right-side
Contralateral - if second location is on other side of body - One side of the brain controls the opposite.
Superior - above
Inferior - below Neurons of cerebral cortex are arranged in 6
Anterior / rostral - head end distinct layers, with each layer having unique
Posterior / caudal - tail end appearance due to specific patterns of dendrites,
Proximal - near center of limb axons or neurons.
Distal - toward the end of limb - Some telencephalic structures do not have
Afferent - carry information into a region these layers, but are made up of allocortex
Efferent - carry information out of a region (= tissue with three layers or unlayered
Dorsal - towards the back organization).
Ventral - towards the belly - Cortical columns extend through thickness
of cortex, from white matter to the surface.
Brain development: - Synaptic interconnections of neurons
(1) CNS starts out as a neural tube, enlined with are vertical, but can also be horizontal.
cells and filled with fluid - separates into three - Layer I - few cell bodies
parts: - Layers V and VI - many neurons with large
- Forebrain (prosencephalon) cell bodies.
o Telencephalon = cortex, basal ganglia and
limbic system. The most prominent neuron in cerebral cortex =
o Diencephalon=thalamus & hypothalamus pyrimidal cells (layer III or V).
- Midbrain (mesencephalon) - Apical dendrite = 1 dentrite that extends from top of cell body (= apex) to outermost layer of cortex.
- Hindbrain (rhombencephalon) - Basal dendrites - dendrites that spread horizontally from the base of the cell body.
o Metencephalon = cerebellum & pons
o Myelencephalon = medulla The midbrain has both sensory and motor components:
- Tectum (= top part of midbrain) contains two pairs of bumps in each hemisphere involved in sensory
Brainstem - midbrain, pons and medulla combined. processing.
- Superior colliculi - rostral bumps - role in visual processing
In CNS: - Inferior colliculi - caudal bumps - role in sound processing
- Nuclei = aggregations of neurons - Motor components:
- Tracts = bundles of axons (1) substantia nigra - for release of dopamine - related to Parkinson’s disease
In PNS: (2) red nucleus - communicates with motor neurons in the spinal cord.
- Ganglia = aggregations of neurons - Reticular formation (= distributed network of neurons) - implicated in sleep and arousal, temperature
- Nerves = bundles of axons regulation, and motor control.
Basal ganglia - important in motor control - composed Cerebellum - attached to pons and crucial for motor coordination, control and certain aspects of cognition.
of: - has a convoluted surface for more surface area.
- Caudate nucleus telencephalon - Middle layer - Purkinje cell layer - Purkinje cells.
- Putamen telencephalon - Inner layer contains granule cells - rise to the surface of cerebellum and form parallel fibers of the outer layer.
- Globus pallidus telencephalon
- Substantia nigra midbrain Medulla - most caudal portion of brainstem that marks the transition from brain to spinal cord.
These nuclei are connected with the cerebral cortex - - Contains nuclei that regulate breathing and heart rate, therefore damage or lesion in medulla causes death.
forms a looping neural system. - All axons passing between brain and spinal cord pass through the medulla.
Limbic system - important in emotion and learning - Cortical regions communicate with one another via tracts of axons looping through the underlying white matter =
loose network of structures through each hemisphere connectome (= network map that completely describes functional connections within and between brain regions).
composed of:
- Amygdala emotion, odor perception, Brain and spinal cord are surrounded by 3 protective membranes called meninges:
learning and memory (1) Dura mater - outer layer
- Mammillary bodies learning and memory (2) Pia mater - inner layer - attached to surface of brain
- Hippocampus learning and memory (3) Arachnoid - suspends brain in cerebrospinal fluid (CSF)
- Fornix learning and memory Meningitis = inflammation of meninges (usually viral infection) characterized by headache, fever and stiff neck.
- Septal nuclei reward and reinforcement of Meningiomas = tumours formed by meninges.
learning
- Cingulate gyrus direction of attention and cognitive functions Ventricular system - series of chambers filled with CSF.
- Olfactory bulb sense of smell - The CSF in ventricular system has 2 functions:
- Stria terminalis - fiber pathway connecting amygdala to limbic structures near base of brain, especially (1) acts mechanically as a shock absorber for the brain - protected from sudden movements of head.
hypothalamus, participating in highly motivated behavior like sex/threat responses, and integration of (2) CSF provides medium for exchange of materials, like nutrients, between blood vessels and brain tissue.
hormonal signals. - Each hemisphere contains a lateral ventricle, which extends into all four lobes.
- Lined with specialized membrane (= choroid plexus) that produces CSF by filtering blood.
Thalamus - complex cluster of nuclei that (1) directs incoming sensory information to appropriate cortex regions for - CSF flows from lateral ventricles to third ventricle to fourth ventricle (lies between cerebellum and pons).
further processing, and (2) receives instructions back from cortex to control which sensory information is - From fourth ventricle, CSF exits the ventricular system through three small openings, causing it to
transmitted. circulate over the outer surface of the brain and spinal cord.
- Hypothalamus - packed with discrete nuclei for vital functions (hunger, thrist, thermoregulation) - controls
pituitary gland to regulate hormonal regulation of the body. The brain uses ~20% of body’s energy at rest.
