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Summary LECTURES & BOOK (also Q&A ANSWERS!) for Brain and Cognition 1 (Radboud University Nijmegen)
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Test Bank for An Introduction to Brain and Behavior 6th Bryan Kolb , Ian Q. Whishaw , G. Campbell Teskey A+ 2024
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Brain & Behavior (Chapter 1 & 2)
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Complete summary of Brain & Behavior
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What are the nervous system´s functional units?Visualizing cells→highlighting individual cells in nervous system tissue; to make the tissue firm, they
soaked it in formaldehyde to preserve and fix the tissue by binding together its constituent protein
molecules; the tissue is then sliced in thin sheets and stained (colored) with various dyes.
Golgi→technique (thin slice of brain tissue in solution containing silver nitrate and other chemicals)
same procedure that was used to produce black-and-white photographs; the nervous system is an
interconnected network of fibers in which information flows around this “nerve net”
Cajal→the nervous system is made up of discrete cells, which begin life as a simple structure and
become more complex with age; neurons are the nervous systems functional units; interactions
between these discrete cells enable behavior and the more neurons an animal has the more complex
its behavior
Basic structure of neuron→Soma, dendrites and axon
Neurons are the basis of information processing
Neural networks→connect wide areas of the brain and spinal cord; neurons work together to
produce most behaviors in most species; neurons are plastic so unused neurons be lost and new
connections with each other are made; most of our neurons are with us for life
Structure and function of the neuron
Dendrites collect information from other cells, and the spines are the points of contact with those
neurons; each neuron has a single axon to carry messages to other neurons; axon begins at an
expansion known as the axon hillock and the axon branches out into one or many axon collaterals;
the terminal button doesn’t touch another neuron but is close to its dendrites and this near
connection is called the synapse, which is the information transfer site between neurons
Sensory neurons→conduct information from the sensor receptors in or on the body into the spinal
cord and brain (bipolar neuron found in they eye has a single short dendrite and a single axon and
they transmit afferent sensory information from the retina´s light receptors to the neurons that carry
information into the brain´s visual centers) (Somatosensory neurons bring sensory information from
the body into the spinal cord)
Interneurons→associate sensory and motor activity in the CNS (the pyramidal cell has a long axon, a
pyramid-shaped cell body and two sets of dendrites and they carry information from the cortex to
the rest of the brain and spinal cord) (the purkinje cell carries information from the cerebellum to
the rest of the brain and spinal cord)
Motor neurons→carry information from the brain and spinal cord out to the body´s muscles
Neuronal networks→input, association and output; so sensory neurons collect afferent information
from the body and connect to interneurons that process the information and pass it on to motor
neurons. The motor neurons efferent connections move muscles and so produce behavior
Excitation and inhibition
Neurons either excite or inhibit other neurons (yes/no signal); the neuron sums the inputs and if its
excitatory inputs exceed its inhibitory inputs and then sends a message. Robots mimic neural
systems→robot that has excitatory input from chirping mail and orients towards it
,Five types of glial cells
Glial cells are the nervous system´s support cells.
Ependymal cells→produce and secrete cerebrospinalfluid, which acts as a shock absorber, carries
away waste products, assists the brain in maintaining a constant temperature and is a source of
nutrients for parts of the brain adjacent to the ventricles; hydrocephalus→if there is a blockage,
which causes pressure due to the produced CSF
Astrocytes→star shaped; contributes to neuronal nutrition, support and repair; contribute to the
structure of a protective partition between blood vessels and the brain the blood-brain barrier;
astrocytes receive signals from other neurons, pass them on to the blood vessels and so contribute
to increased blood flow and fuel supply; they also contribute to healing damaged brain tissue
Microglial cell→small; defensive function to remove dead tissue; provide growth factors that aid in
repair; involved in protecting the nervous system from disease and play an important role in
maintaining the brain´s health
Oligodendroglial cell→forms myelin around CNS axons in brain and spinal cord
Schwann cell→wraps around peripheral nerves to form myelin
Oligodendroglia and schwann cells contribute to a neuron´s nutrition and functioning by absorbing
chemicals that the neuron releases and releasing chemicals that the neuron absorbs
Glia cells and neuron repair
However, when the CNS is damaged for example when the spinal cord is cut, regrowth and repair do
not occur. So, the oligodendrocytes that myelinate the CNS do not behave like PNS schwann cells to
encourage brain repair.
Internal structure of a cell
Golgi body→membranous structure that packages protein molecules for transport
Lysosomes→vesicles that transport incoming supplies and remove and store wastes
Microfilaments→fibers making up much of the cell´s skeleton
Nucleus→Zellkern, containing the chromosomes and genes
Nuclear membrane→surrounding the nucleus
Mitochondrion→structure that gathers, stores and releases energy
Endoplasmic reticulum→extension of the nuclear membrane, where the cell´s protein products are
assembled in accordance with instruction from the nucleus
Intracellular fluid→fluid in which the cell´s internal structures are suspended
Tubule→tiny tube that transports molecules and helps give the cell its shape
Dendritic spine→small membranous protrusion from a dendrite that typically receives input from a
single axon at the synapse
Cell membrane
The cell membrane separates the intracellular from the extracellular fluid. It regulates the movement
of substances into and out of the cell; regulates differing concentrations of salts and other chemicals;
Phospholipid bilayer→double-layered structure (head of phospholipid are hydrophilic and tails are
hydrophobic), so no water can go through the membrane because of the hydrophobic tails neither
ions because they carry charges and cannot pass the polar phospholipid heads; just oxygen, carbon
dioxide and glucose for example can traverse the membrane.
,The nucleus and protein synthesis
Genes are contained within the chromosomes, the double-helix structures that hold an organisms
DNA. Each gene is the blueprint, or code, for making one protein. Human body contains 23 pairs of
chromosomes. The genetic code contains Adenine, Thymine, Guanine and Cytosine. A-T G-C. A
gene´s code is its sequence of thousands of nucleotide bases.
The RNA produced through transcription is like a single DNA strand except the base uracil which
takes place of thymine and is also attracted to adenine. The transcribed strand of RNA is called mRNA
because it carries the protein code out of the nucleus to the endoplasmic reticulum, where proteins
are manufactured. During translation each codon of the mRNA is transformed into a particular amino
acid, so there is a polypeptide chain, which constructs the protein. Each amino acid consists of a
central carbon atom (C) bound to a hydrogen atom (H), an amino group (NH3+), a carboxyl group
(COO-), and a side chain(R). The side chain varies in chemical composition from one amino acid to
another.
Proteins: the cell´s product
A protein´s shape and its ability to change shape and to combine with other proteins are central to
its function. A long polypeptide chain has a tendency to twist into a helix or for pleated sheets, which
in turn fold together to form more complex shapes. A protein is a folded-up polypeptide chain that
serves a particular function in the body.
Golgi bodies and microtubules
Crossing the cell membrane: channels, gates, and pumps
Proteins can change→some proteins change shape when other chemicals bind to them; others
change shape as a function of temperature; and still others change shape in response to changes in
electrical charge.
,Mendelian genetics and the genetic code
Human has 23 chromosome pairs; 22 autosomes and the 23 pair are the sex chromosomes; each cell
contains two copies of every gene, one inherited from the mother and one from the father, which
are called alleles; the two alleles can either be homozygous (identical) or heterozygous (different);
dominant allele (routinely expressed) and recessive allele (unexpressed); mutations may be as small
as a change in a single nucleotide base, but this will lead to a change in codon and result in a change
of one amino acid in a protein; mutations can be beneficial, disruptive or both
Allele disorders that affect the brain
A baby can only inherit Tay-Sachs disease when both parents carry the recessive allele (recessive
gene carries Tay-Sachs allele). Disorder characterized by seizures and degenerating motor/mental
abilities at baby age.
Only one defective allele is needed to cause Huntington (dominant gene carries Huntington´s allele).
Thus if one parent carries the defective allele, offspring have a 50 percent chance of inheriting the
disorder. Disorder characterized by memory loss, involuntary movements, death.
Genetic engineering
Manipulating a genome, removing a gene from a genome, or modifying or adding a gene to the
genome.
Selective breeding→researchers produce whole populations of animals possessing some unusual
trait that originally arose as an unexpected mutation in only one individual or few animals.
Cloning→altering early embryonic development; scientists begin with cell nucleus containing DNA
and place it in an egg cell from which the nucleus has been removed and after stimulating the egg to
start dividing, implant the new embryo in the uterus of a female.
Transgenic techniques→introduce genes into an embryo or remove genes from
Phenotypic plasticity and the epigenetic code
Phenotypic plasticity due to the genome´s capacity to express a large number of phenotypes and due
to epigenetics, the influence of environment and experience in phenotypic expression. Epigenetics
describes how a single genetic code produces each somatic cell type, explains how a single genome
can code for many phenotypes, and describes how cell functions go astray to produce diseases
ranging from cancer to brain dysfunction. Epigenetic mechanisms can influence protein production
either by blocking a gene to prevent transcription or by unlocking a gene so that it can be
transcribed. Chromosomes are wrapped around histones.
,Q&A Lecture:
2. false, it’s the other way around
3. false, they don’t touch there is a synaptic gap in between
4. true, but its not enough as a description how the brain can be understood
(neurons also inhibit each other)
5. true, the astrocytes do it
6. true, microglial cells
7. true, schwann cells
8. false, because it does the opposite so the water cannot go through; it attracts but
also repells water
9. false, they read the mRNA to convert it in a chain of amino acids
10. true
11. true
12. channels, pumps, and gates
13. false, because the Tay-sachs allele is on a recessive gene so both parents need to
have the gene
14. true, because the allele is on a dominant gene and one of the genes will definitely
be given to the child
15. false, because of epigenetic influence
16. histone modification, gene methylation, mRNA modification
,Neural transmission: how do neurons transmit information?
Electrical stimulation studies→Galvani discovered that passing an electrical current from
the uninsulated tip of an electrode onto a nerve to produce behavior-a muscular
contraction.
Electrical recording studies→less invasive evidence that information flow in the brain is
partly electrical; Richard Caton measured the brain´s electrical currents with a sensitive
voltmeter; today this method is EEG.
Tools for measuring a Neuron´s electrical activity
If an electrode connected to a voltmeter is placed on a single axon, the electrode can detect
a change in electrical charge on that axon´s membrane. The oscilloscope is a voltmeter with
a screen sensitive enough to display the minuscule electrical signals emanating from a nerve
or neuron over time. A microelectrode is small enough to place on or in an axon; they can
deliver an electrical current to a single neuron or record from it.
How ion movement produces electrical charges
Diffusion→movement of ions from an area of higher concentration to an area of lower
concentration through random motion; the result of diffusion is a dynamic equilibrium;
movement from an area of high concentration to an area of low concentration along the
concentration gradient.
The molecules are electrical charged. A voltage gradient is the difference in charge between
two regions that allows a flow of current if the two regions are connected.
Due to the concentration gradient, the positive potassium ions diffuse through the
membrane to the outside of the cell. Because the positively charged potassium ions are
attracted to the negatively charged ions inside, they don’t completely diffuse. Now there are
still more potassium ions inside, but the inside of the cell is negative, because there are
more negatively charged ions inside. As a result of the concentration gradient and the
selective permeability of the membrane you will induce a voltage gradient. At some point,
there is no more transportation of potassium ions from inside to outside, because there is a
concentration gradient that forces the potassium ions to go outside but at some point it is
not strong enough anymore to push the potassium ions outside because it is countered by
the voltage gradient. That is the equilibrium of concentration gradient=voltage gradient. Cl-
ions channel freely, but the Cl- voltage gradient that balances the concentration gradient
equals the membrane´s resting potential. The reversal potential is the membrane potential
when there is no flow of a certain ion across the membrane.
Resting membrane potential
The resting membrane potential is -70mV. The cell membrane´s channels, gates, and pumps
maintain the resting potential. There are more A- and K+ ions inside the cell and more Na+
and Cl- ions outside the cell. Because the membrane is relatively impermeable to large
molecules, the negatively charged Anions (A-) remain inside the cell. Na+ channels are
blocked and don’t allow the Na+ to diffuse to the inside, but still over time some Na+ ions
can leak inside. Due to the K+ leak channel some potassium diffuses to the outside of the cell
according to the concentration gradient. The Na/K pump pumps 3 Na+ ions out of the cell
and 2K+ ions inside the cell to restore the Na+ and K+ concentration gradients.
,Action potential
The voltage across the membrane suddenly reverses, making the intracellular side positive
relative to the extracellular side, then abruptly reverses again to restore the resting
potential. An action potential is triggered when the cell membrane is depolarized to about
-50mV. At that threshold potential, the membrane charge undergoes a remarkable further
change with no additional stimulation. The depolarizing phase of an action potential is due
to Na+ influx, and the hyperpolarizing phase, to K+ efflux.
At the hillock, where EPSP and IPSP are summed, there are highly specialized voltage-
operated ion channels. If the EPSP reaches the threshold of -50mV this causes the voltage-
operated Na+ channels to open which leads to more depolarization and an action potential
occurs.
Both sodium and potassium voltage-sensitive channels are attuned to the threshold voltage
of about -50 mV. If the cell membrane changes to reach this voltage, both types of channels
open to allow ion flow across the membrane. The voltage-sensitive sodium channels are
more sensitive and open first, as a result the voltage change due to sodium influx takes place
slightly before the voltage change due to potassium. Once the membrane depolarizes to
30mV the sodium channels close. The potassium channels are open longer than the sodium
channels so the efflux of potassium repolarizes and even hyperpolarizes the membrane.
The action potential is “all-or-none”! It is always the same size. All action potentials are alike
and are independent of stimulus intensity. Strong stimuli can generate an action potential
more often than weaker stimuli. The CNS determines stimulus intensity by the frequency of
impulse transmission.
The action potential propagates along the axon toward the terminals. This propagation
occurs through the activation of voltage-operated ion channels that are strung out along the
axon. The sodium channels depolarize and the potassium channels repolarize the axon
during propagation. When an action potential occurs, it brings adjacent parts of the
membrane to a threshold of -50mV. When the membrane at an adjacent part of the axon
reaches -50mV, the voltage-sensitive channels at that location pop open to produce an
action potential there as well. Each successive action potential “gives birth” to another down
the length of the axon.
Refractory periods prevent an action potential from reversing direction and returning to its
point of origin. Absolute refractory is during the depolarizing and repolarizing phase. During
hyperpolarization, another action potential can be induced, but the second stimulation must
be more intense than the first (relatively refractory).
Saltatory conduction→Schwann cells in the PNS and oligodendroglia in the CNS wrap
around each axon, forming the myelin sheath that insulates it. Action potentials cannot
occur where myelin is wrapped around an axon. There are gaps between the myelinated
axon called nodes of Ranvier, which are sufficiently close to one another that an action
potential at one node can open voltage-sensitive gates at an adjacent node. In this way
relatively slow action potentials jump quickly from node to node. Myelin has two important
consequences: propagation becomes cheaper, since action potentials only regenerate only
at the nodes of Ranvier, not across the entire axon; it improves the action potential´s
conduction speed.
Multiple Sclerosis→the myelin formed by oligodendroglia is damaged, which disrupts the
functioning of neurons whose axons it encases. Symptoms of sensory loss and difficulty
moving.
, EPSP´s and IPSPS´s/Integrating synaptic input
Neurons are not only stimulated by other neurons, but also inhibited. IPSP´s produce a
hyperpolarizing graded potential and decrease the likelihood that an action potential will
result. EPSP´s produce a depolarizing graded potential and increase the likelihood that an
action potential will result. Inhibitory synapses are usually found on the cell body.
Summation of inputs:
Temporal summation→two depolarizing pulses stimulation separated in time produce two
EPSP´s similar in size; pulses close together in time partly sum; simultaneous EPSP´s sum as
one large EPSP. Same for IPSP´s.
Spatial summation→EPSP´s produced at the same time, but on separate parts of the
membrane do not influence each other; EPSP´s produced at the same time, and close
together, sum to form a larger EPSP. Same for IPSP´s.
A neuron is an integrating machine. In the cell body all the incoming IPSP´s and EPSP´s are
combined. If the threshold is reached an axon potential is generated at the axon hillock.
Sensory Receptors
All sensory pathways begin with a stimulus, which acts on sensory receptors, which convert
the stimulus in neural signals, which are transmitted by sensory neurons to the brain,
where they are integrated. Chemoreceptors olfaction; Mechanoreceptors vibration,
acceleration, sound; Photoreceptors light; Thermoreceptors temperature; Nocireceptors
tissue damage (pain).
Take touch as an example: when you bend a hair, the encircling dendrite is stretched. This
displacement opens stretch-sensitive channels in the dendrite´s membrane. That
depolarizes the cell membrane and, when at threshold, voltage-operated channels in the
membrane open, and an action potential is generated.
Motor neurons
Motor neurons in the spinal cord are responsible for activating muscles. The axon terminal
of the motor neuron releases the chemical transmitter acetylcholine onto the muscle´s end
plate. Ach attaches to transmitter-sensitive channels on the end plate and opens them.
These Ach-operated channels allow sodium to go in and potassium to go out, which will
depolarize the end plate. This will active the voltage-operated sodium channels that trigger
an action potential on the muscle, causing it to contract. So muscles generate action
potentials to contract.
ALS→is a rapidly progressive fatal neuromuscular disease: motor neurons degenerate;
voluntary muscles become paralyzed; generally the intellect & senses are unimpaired
Neural transmission summed up:
1. Neurons receive signals either in a chemical (i.e. neurotransmitter, or odor molecule) or
physical form (i.e. touch in somatosensory receptors of skin, light in photoreceptors of eye)
2. These signals initiate changes in membrane of the postsynaptic neuron that make
electrical currents flow in and around the neuron
3. The electrical currents act as signals within the neuron, affecting the membrane at sites
far from the synapse
4. The current flow is mediated by ionic currents carried by electrically charged atoms (ions)
e.g sodium, potassium and chloride, dissolved in fluid inside and outside of neurons
5. Long-distance signals (action potentials) can be generated in the axon hillock, a region of
the neuron that integrates the current coming in from many synapses
6. The axon hillock is the “spike trigger zone” where “spike” refers to an action potential
7. The signal travels down the axon to its terminals causing the release of
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