Week 1 09/13/2013
Hard Problem: Given the universe composed of matter and energy, why is there such thing as consciousness?
Mindbrain Problem: What is the relationship between the mental experience and brain activity?
Biological Psychology: physiological, evolutionary and developmental mechanisms of behaviour and experience
goal is to relate biology to issues of psychology
Neuroscience: much is relevant to behaviour but also includes more detail about anatomy and chemistry
Neurons: receive info and transmit it to other cells. Brain composed of individual cells
Glia: generally smaller, have many functions, BUT do not convey info over great distances
#1: Physiological Explanation
Relates to behaviour to the activity of the brain and other organs
Deals with machinery of body
Ex. Chemical reactions that enable hormones to influence brain activity and routes by which brain activity controls
muscles
#2: Ontogenetic Explanation
Comes from Greek word meaning “origin” How a structure or behaviour develops, including influences of genes, nutrition, experiences and other interactions
Ex. Ability to inhibit impulses develops gradually from infancy through teenage years reflecting gradual maturation of
frontal parts of the brain
#3: Evolutionary Explanation
Reconstructs the evolutionary history of a structure or behaviour
Characteristic features of an animal are almost always modifications of something found in ancestral species
Ex. Monkeys use tools occasionally > humans evolved elaborations that enable us to use tools even better
#4: Functional Explanation
Why a structure or behaviour evolved as it did
Small isolated population, gene can spread by accident through genetic drift Nerve Cells Wednesday, September 11, 2013
The Cells of the Nervous System
Cajal – one of two main founders of Neuroscience
His research demonstrated that nerve cells remain separate instead of merging into one another
The Structures of an Animal Cell
Membrane: surface of the cell, structure that separates the inside of the cell from the outside environment
it is composed of two layers of fat molecules that are free to flow around one another
most chemicals cannot cross the membrane, but specific protein channels in the membrane permit a controlled flow of water,
oxygen, sodium, potassium, calcium, chloride etc.
Nucleus: structure that contains chromosomes
all animal cells have this, with exclusion to mammalian red blood cells
Mitochondrion: structure that performs metabolic activities, providing the energy that the cell requires for all other activities
require fuel and oxygen to function
Ribosomes: sites the cell synthesizes new protein molecules
proteins provide building materials for the cell and facilitate various chemical reactions
some attracted to the endoplasmic reticulum: a network of thin tubes that transport newly synthesized proteins to other locations
The Structure of a Neuron
most distinctive is their shape, which varies from one to another
branching extensions
larger neurons: dendrites, a soma (cell body), and axon, and presynaptic terminals (the tiniest neurons lack axons, and some
welldefined dendrites) Nerve Cells Wednesday, September 11, 2013
Motor Neuron: soma in the spinal cord, receives excitation from other neurons through its dendrites and conducts impulses
along its axon to a muscle
Sensory Neuron: specialized at one end to be highly sensitive to a particular type of stimulation, such as light, sound or touch
Dendrites: branching fibers that get narrower near their ends (comes from Greek word meaning “tree”)
surface is lined with specialized synaptic receptors, where the dendrite receives info from other neurons
the greater surface area, the more info it can receive (branch widely)
Dendritic spines: short outgrowths that increase the surface area available for synapses
Cell body/Soma: contains the nucleus, ribosomes, and mitochondria
most of metabolic work of neuron occurs here
range in diameters 0.005 mm to 0.1 mm in mammals and up to full millimeter in certain invertebrates
covered with synapses on its surface in many neurons
Axon: thin fiber of constant diameter, in most cases longer than the dendrites
term comes from Greek word meaning “axis”
neurons info sender, conveying an impulse toward other neurons or organ or muscle
Myelin Sheath: insulating material
Nodes of Ranvier: interruptions in the myelin sheath
Presynaptic Terminal: swells at the tips of the branches of the axon (end bulb or bouton)
point where axon releases chemicals that cross through the junction between one neuron to the next
neuron can have any number of dendrites
only one axon, but that axon may have branches far from the soma
axons can be a meter in length (spinal cord to feet)
the size of it is like a narrow highway that stretches across a continent Nerve Cells Wednesday, September 11, 2013
Afferent Axon: brings infinto structure (sensory neuron) (A = admit)
Efferent Axon: carries infaway from structure (motor neuron) (E = exit)
Interneuron/Intrinsic Neuron: when a cell’s dendrites and axon are entirely contained within a single structure
shape of a given neuron determines its connections with other neurons and thereby determines its contribution to the nervous
system
wider branches = more targets
Glia
perform many functions (not transmitting info though)
from Greek word meaning “glue” – reflects early investigators idea that glia are like glue that held neurons together
smaller, but more numerous than neurons
Astrotypes: starshaped, help synchronize the activity of the axons, enabling them to send messages in waves
remove waste material created when neurons die and control the amount of blood flow to each brain area
Neurons communicate by releasing certain transmitters, such as glutamate, after neurons release this, nearby glia cells absorb
some of the access
glia convert most of this glutamate into glutamine and then pass it back to the neurons which convert it back to glutamate which
they get ready for further release
Microglia: very small cells, remove waste material as well as viruses, fungi and other microorganisms – function as part of the
immune system
Oligodendrocytes: build the myelin sheaths that surround and insulate certain vertebrate axons
Schwann Cells: glia cells that build myelin sheath
Radial Glia: guide to migration of neurons and their axons and dendrites during embryonic development
when embryological development finishes, most radial glia differentiate into neurons, and a smaller number differentiate into
astrocytes and Oligodendrocytes
The BloodBrain Barrier Nerve Cells Wednesday, September 11, 2013
Depends on the endothelial cells that form the walls of the capillaries
Outside the brain, such cells are separated by small gaps, but in the brain, they are joined tightly that virtually nothing
passes between them
The barrier keeps out useful chemicals as well as harmful ones
o Useful – fuels and amino acids, the building blocks for proteins
#1 Small Charged Molecules
oxygen and carbon dioxide, cross freely
water crosses through special protein channels in the wall of the endothelial cells
#2 Molecules that dissolve in the fats of the membrane
cross passively
Ex., vitamins A and D and all drugs that affect the brain
Active Transport: brain uses proteinmediated process that expends energy to pump chemicals from the blood into the brain
Chemicals that are actively transported into the brain include:
o Glucose (brains main fuel)
o Amino acids (building blocks of proteins)
o Purines
o Choline
o Few vitamins
o Iron
o Certain hormones
essential to health
Example: Alzheimer’s disease or similar conditions, the endothelial cells lining the brains blood vessels shrink, and harmful
chemicals ever the brain Nerve Cells Wednesday, September 11, 2013
also poses difficulty in medicine because it keeps out many medications
Vertebrate Neurons
Depend entirely on glucose, a sugar
because the metabolic pathway that uses glucose requires oxygen, neurons need a steady supply of oxygen
Glucose is practically the only nutrient that crosses the bloodbrain barrier after infancy, except for ketones (a kind of fat)
Glucose shortage is rarely a problem
liver makes glucose from many kinds of carbohydrates and amino acids
Only likely problem is an inabilituseo glucose
to use glucose the body needs vitamin B1, thiamine
prolonged thiamine deficiency, common in chronic alcoholism, leads to death of neurons and a condition Week 1 Friday, September 13, 2013
The Resting Potential of the Neuron
All parts of a neuron are covered by a membrane about 8 nanometers thick
Composed of two layers of phospholipid molecules (containing chains of fatty acids and a phosphate group)
embedded among phospholipids are cylindrical protein molecules chemicals can pass
Structure of membrane – flexibility and firmness and controls flow of chemicals between the inside and outside of cell
When there is no outside disturbance, electrical gradient/polarization: a difference in electrical charge between the inside and outside of the
cell
neuron inside – slightly negative electrical potential compared to outside (negatively charged proteins inside the cell)
Resting Potential: its stable, negative charge when the cell is inactive, difference in voltage in a resting neuron (RESTING VOLTAGE)
researchers measure by inserting a very thin microelectrode into the cell body
must be as small as possible so it does not cause damage
most common electrode is a fine glass tube filled with a concentrated salt solution and tapering to a tip diameter of 0.0005 mm or less
Membrane is selectively permeable: some chemicals pass through it more freely than others
Biologically important ions:
Sodium
Potassium
Calcium
Chloride
▯ cross through membrane channels or gates that are sometimes open or closed Week 1
More
Less
