Flashcards in structure Deck (34):
Interposed between sensory and motor neurons
Neurons have an architecture that consists of a cell body
and two sets of additional compartments called
‘processes’ -- axons and dendrites (also synaptic terminals at the end of axons). Neurons are organised into complex chains
and networks that are the pathways through which
information in the nervous system is transmitted.
Arising from the roof of the hind-brain
extension of the spinal cord. It contains networks of
neurons that constitute centres for the control of vital
functions such as breathing and blood pressure. Within
these are networks of neurons whose activity controls these
contains groups of neurons, each of which seem
to use predominantly a particular type of chemical
messenger, but all of which project up to cerebral
Packed into the limited space of the skull, the cerebral cortex
is thrown into folds that weave in and out to enable a much
larger surface area for the sheet of neurons than would
otherwise be possible. The cortical tissue is divided into a large number of discrete
areas, each distinguishable in terms of its layers and
halves of the brain do not work in isolation - for the left and
right cerebral cortex are connected by a large fibre tract
called the corpus callosum.
neurons: internal structure
Like any structure, it has to hold together. The outer
membranes of neurons, made of fatty substances, are
draped around a cytoskeleton that is built up of rods of
tubular and filamentous proteins that extend out into
dendrites and axons alike. The structure is a bit like a canvas
stretched over the tubular skeleton of a frame tent.
protuberances that stick out from the dendrites
In many axons, action-potentials move along reasonably well,
but not very fast. In others, action potentials really do skip
along the nerve. This happens because long stretches of the
axon are wrapped around with a fatty, insulating blanket,
made out of the stretched out glial cell membranes, called a
Neurotransmitters are stored in tiny spherical bags called
synaptic vesicles in the endings of axons. There are vesicles
for storage and vesicles closer to nerve endings that are
ready to be released.
a set of proteins in the membranes of neurons. usually found in complex
particles linking the outside of the cell to enzymes inside the
cell that affect cell metabolism.
- An important concept about somatosensory receptors is
that of the receptive field. This is the area of skin over which
each individual receptor responds.
- vision: the region of retina over which the cell
will respond to the prefered kind of image
The input from the body is systematically “mapped” across
the somatosensory cortex to form a representation of the
body surface. in the somatosensory cortex, the packing density of neurons is uniform. Consequently, the ‘map’ of the body
surface in the cortex is very distorted. a sensory homunculus is the pictorial representation of this.
structure of the two types of fiberss that transmit pain messages
A-delta and C fibers: both enter the spinal cord, where they synapse with a series of
neurons that project up to the cerebral cortex. They do so
through parallel ascending pathways, one dealing with the
localisation of pain (similar to the pathway for touch), the
other responsible for the emotional aspect of pain.
electrical acupuncture machine
A pair of electrodes are placed at the "Heku" points
on the hand, another at the site of pain.
of each eye, projects to the brain. The fibres
of each nerve meet at a structure called the optic chiasm;
half of them “cross” to the other side where they join the
other half from the other optic nerve that have stayed
“uncrossed”. Together these bundles of fibres form the optic
tracts, now containing fibres from both eyes.
each contains fibers from both eyes (crossed + uncrossed); the optic tracts project (via a synaptic relay in a structure called the lateral
geniculate nucleus) to the cerebral cortex. It is here that
internal “representations” of visual space around us are
consists of a number of areas, dealing with
the various aspects of the visual world such as shape, colour,
movement, distance etc. These cells are arranged in columns.
primary visual cortex
In V1, the first
stage of cortical processing, the neurons respond best to
lines or edges in a particular orientation. An important
discovery was that all the neurons in any one column of cells
fire to lines or edges of the same orientation, and the
neighbouring column of cells fires best to a slightly different
orientation, and so on across the surface of V1.
canonical cortical microcircuit
have suggested there is a canonical cortical microcircuit -
like chips in a computer. Not everyone agrees. We now think
the circuitry in one visual area has many similarities to that
in another, but there could be subtle differences that reflect
the different ways in which each bit of the visual brain interprets
different aspects of the visual world.
blood brain barrier
This is not really a barrier, but
specialised endothelial cells in the brain blood vessels that
are relatively resistant to the passage of large molecules
or immune cells from the blood into the brain.
(a cascade of proteins important
in killing invader cells)
hypothalamic-pituitary-adrenal axis; circuit linking the body and brain. links together the hypothalamus, pituitary
gland, adrenal cortex and hippocampus by a bloodstream
highway carrying specialised hormones.
alphabetic visual symbols in their right order
to hear the separate sounds in words in their right order involves extracting what is called the phonemic structure, so that the symbols can be translated into the correct sounds
control of reading: anatomy
the magnocellular system can be traced right from
the retina, through the pathway to the cerebral cortex and
cerebellum, to the motor neurons of the eye-muscles.
mainly on the receiving side
of the synapse, come in four varieties: three are ionotropic
receptors and have been given the names AMPA, NMDA and
kainate. The fourth type is metabotropic and is called
if the left eye sees
a pattern of vertical lines while the right eye sees a pattern
of horizontal lines. The resulting percept is termed binocular
rivalry, as the observer reports first that the vertical lines
dominate, then the horizontal lines and then back again to
a thin strip of tissue running across the
surface of the brain, directly in front of the somatosensory
cortex. in the motor cortex, individual neurons use a population code in which actions are specified by the firing of an ensemble of neurons.