trivia Flashcards
sensory neurons
none
motor neurons
none
interneurons
These are by far the most numerous (in the
human brain)
glial cells
long thought to have a purely
supporting function to the neurons
cerebral cortex
cortical tissue is the most highly
developed area of the brain in humans - four times bigger
than in gorillas
lateralization of the brain
Many of the cortex’s functions are carried out by
both sides of the brain, but some are largely lateralised to
one cerebral hemisphere or the other. Areas concerned with
some of these higher functions, such as speech (which is
lateralised in the left hemisphere in most people), have been
identified.
On the receiving side of the cell, the dendrites have close
contacts with incoming axons of other cells, each of which is
separated by a miniscule gap of __. These junctional spots are
named __, from __ words that mean “__”.
On the receiving side of the cell, the dendrites have close
contacts with incoming axons of other cells, each of which is
separated by a miniscule gap of about 20 billionths of metre. These junctional spots are
named synapses, from classical Greek words that mean “to
clasp together”.
Cajal
Ramon Y Cajal, father of modern neuroscience. photograph shows him in 1890.
Hodjkin
Alan Hodgkin and Andrew Huxley won the Nobel Prize for discovering the mechanism of transmission of the nerve impulse. They used the "giant axon" of the squid in studies at the Plymouth Marine Biology Laboratory
Huxley
Alan Hodgkin and Andrew Huxley won the Nobel Prize for discovering the mechanism of transmission of the nerve impulse. They used the "giant axon" of the squid in studies at the Plymouth Marine Biology Laboratory
action potential speed
in myelinated neurons,
action-potentials can race along at 100 metres per second!
action potential frequency
The most efficient axons can
conduct action potentials at frequencies up to 1000 times
per second.
synaptic cleft
20 nanometer gap that the chemical messenger diffuses across
excitatory and inhibitory neurotransmitters
The main excitatory neurotransmitter in the brain is
glutamate. There are
two inhibitory neurotransmitters – GABA and glycine.
synaptic transmission time
Synaptic transmission is a very rapid process: the time
taken from the arrival of an action potential at a synapse to
the generation of an epsp in the next neuron is very rapid -
1/1000 of a second.
alcohol dependency
about one in ten of regular drinkers will become dependent
alcoholics
alcohol deaths
More than 30,000
people die every year in Britain from alcohol-related diseases.
pregnancy and alcohol
Pregnant mothers who drink run the risk of having
babies with damaged brains and low IQ’s.
smoking deaths
More than
100,000 people die every year in Britain from smoking-related
diseases.
cannabis dependency
About one in ten users may become
dependent
cannabis and mental illness
Although not yet proven,
there is some evidence that heavy use by young people might
trigger the mental illness schizophrenia in
susceptible individuals.
“mid-week blues”
Animal experiments have shown that Ecstasy can
cause a prolonged, perhaps permanent reduction of
serotonin cells. This might account for the “mid-week blues”
suffered by weekend ecstasy users. Every year, dozens of
young people die after taking it
amphetamines and mental illness
Frightening schizophrenialike
psychosis can happen after Dexedrine and Speed.
amphetamines
man-made chemicals that include
“Dexedrine”, “Speed”, and the methamphetamine derivative
called “Ecstasy”. also d-LSD
heroin
a man-made chemical derivative of the plant
product morphine. a very dangerous drug that can kill in even
modest overdose (it suppresses breathing reflexes).
cocaine
plant-derived chemical which can cause
intensely pleasurable sensations as well as acting as a
powerful psychostimulant.
receptive field size
Pacinian corpuscles have
much larger receptive fields than Meissner’s corpuscles
animal experiments on the pain threshold
Animal experiments have revealed that electrical stimulation
of brain areas such as the aqueductal gray matter causes a
marked elevation in the pain threshold and that this is
mediated by a descending pathway from the midbrain to the
spinal cord.
example of endogenous opioid
met-enkaphalin
hyperalgesia
enhanced pain. There is a lowering of the pain threshold, an
increase in the intensity of pain, and sometimes both a
broadening of the area over which pain is felt or even pain in
the absence of noxious stimulation. This can be a major
clinical problem. Hyperalgesia involves sensitisation of the
peripheral receptors as well as complex phenomena at
various levels of the ascending pain pathways.
science behind acupuncture
Forty years ago, a research laboratory was set up in China to
find out how it works. Its findings reveal that electrical
stimulation at one frequency of vibration triggers the
release of endogenous opoiods called endorphins, such as
met-enkephalin, while stimulation at another frequency
activates a system sensitive to dynorphins.
how do photoreceptors work?
respond to the
light that hits them by generating tiny electrical potentials.
These signals pass, via synapes through a network of cells in
the retina, in turn activating retinal ganglion cells whose
axons collect together to form the optic nerve. These enter
the brain where they transmit action potentials to different
visual regions with distinct functions.
photoreceptor light sensitivty comparison
rods are about 1000 times more sensitive to light than the other,
less numerous category called cones.
genetic basis of colorblindness
due to the absence
of certain visual pigments
types of retinal ganglion cells
About 90% of these cells are very small, while another
5% are large M-type or magnocellular cells. We shall see
later that abnormalities in the M-Type cells may underlie
certain cases of dyslexia
where are internal “representations” of visual space around us are
created?
cerebral cortex
number of cortical layers
six
decision making brain region
cerebral cortex
behavior of V5 neurons
(V5 = MT)
It turns out that activity of cells in
V5 accurately reflects the strength of the movement signal.
Neurons here respond selectivity to particular directions of
movement, increasing their activity systematically and
accurately when the proportion of dots moving in their
preferred motion direction increases.
17th C neuro metaphor
In the 17th C,
Descartes used a hydraulic metaphor to explain how the
“humours” of the brain moved the muscles - a metaphor
borrowed from the water engineering he saw in the gardens
of French chateaux.
20th C neuro metaphor
At the turn of the 20th C, reflecting
the industrial age, neurophysiologists described the
intricate wiring of the brain as “an enchanted loom” or later
as a giant “telephone exchange”.
21st C neuro metaphor
Now, at the start of the
21st C, computational metaphors abound, such as the
fanciful speculation that “the cerebral cortex operates not
unlike a private world wide web”.
