nervous system Flashcards
Central and Peripheral Nervous
System
The central nervous system
(CNS) is composed of
the brain and spinal cord.
The peripheral nervous
system (PNS) is composed of
ganglia (structures containing
neurons outside of the CNS)
and nerves (bundles of axons
from CNS and PNS neurons)
Grey matter
called like this
because its colour is pink-greyish.
It contains the body of the
neurons, and the axon terminals.
White matter
contains the nerves
(axons) connecting different
region of the NS to each other or
to the body.
White and Grey Matter locations in brain
White and Grey Matter in the PNS and CNS
Functional division
The nervous system can be divided into regions that are responsible for sensation
(sensory functions or Afferent System) and
for the response (motor functions or Efferent System).
But there is a third
function that needs to be included. Sensory
input needs to be integrated with other
sensations, as well as with memories,
emotional state, or learning (cognition). Some
regions of the nervous system are termed
integration or association areas. The
process of integration combines sensory
perceptions and higher cognitive functions
such as memories, learning, and emotion to
produce a response
Other classifications of the Nervous
System
Macrostructure – areas vs networks
Paul Broca – Aphasiologist → studies from
lesions led to a localistic approach → 1:1 between
areas and functions (Brodmann)
* Neuroimaging and functional Neuroimaging →
Networks
Microstructures – the nervous cells
Microstructure – neurons
Microstructure – glial cells
Glia are the ‘glue’ of the nervous system.
1. Much more than a passive support.
2. At least as numerous as neurons.
3. Provide trophic support.
4. Regulate electrical activity.
5. Protect neurons from external factors.
Each neuron is like a high maintenance computing cluster.
Glia are the maintenance teams of technicians and engineers that actually allow
them to function as a network
The brain can be divided into three basic units:
the forebrain (brain cortex + hidden structures),
2. the midbrain (mesencephalon),
the hindbrain (upper part of the spinal cord, the brain stem,
and the cerebellum).
Brain cortex - Hemispheres
The cerebrum is divided into two halves: the right and left
hemispheres (connected by the corpus callosum).The left
hemisphere controls the right half of the body, and the right
hemisphere controls the left half.
Hemispheric lateralization
the idea that each hemisphere is
responsible for different functions. Each of these functions is
localised to either the right or left side.
The left hemisphere is associated with language functions, while
the right hemisphere is associated with more visuospatial
functions.
Brain cortex- lobes
Six layers of cortex, with different neurons in each layer.
Each cerebral hemisphere can be subdivided into four (plus one) lobes, each associated with different
functions.
Hidden structures in brain
- Limbic lobe: Amygdala, hippocampus, Thalamus and Hypothalamus
- Basal Ganglia
3. Ventricles and cerebrospinal fluids
Amygdala
Involved in fear and emotions
Hippocampus
Involved in memory and high cognitive functions (LTM)
Thalamus and Hypothalamus
The thalamus relays information between the cerebral cortex, brain stem, and other cortical structures. It
contributes to many processes, including attention, perception, timing, and movement. The hypothalamus
modulates a range of behavioural and physiological functions (hunger, thirst, body temperature, and sexual
activity).
Basal Ganglia
The basal ganglia are a group of
structures that regulate the coordination
of fine motor movements, balance, and
posture alongside the cerebellum. It’s
called “Ganglia” because it is a group of
soma of neurons within the white matter.
These structures are connected to other
motor areas and link the thalamus with
the motor cortex. The basal ganglia are
also involved in cognitive and emotional
behaviours, as well as playing a role in
reward and addiction
Components and functions of the basal ganglia
Ventricles and Cerebrospinal fluids
Within the brain, there are fluid-filled interconnected cavities
which are extensions of the spinal cord, called ventricles. These
produce - and are filled with - a substance called cerebrospinal
fluid, which is a clear and colourless liquid. Cerebrospinal fluid
circulates the brain and spinal cord and functions to cushion
the brain within the skull.
the midbrain (mesencephalon) - The mesencephalon plays a role in different bodily functions,
including:
- Controlling the process of vision,
- Pupil dilation
- Eye movement
- Hearing
- Regulating movements of muscles.
Main structures of Mesencephalon
tectum, tegmentum, and substantia nigra
Cerebellum
The cerebellum consists of two hemispheres which are connected
by the vermis, a narrow midline area. Like other structures in the
central nervous system, the cerebellum consists of grey matter and
white matter.
The cerebellum is most directly involved in coordinating voluntary
movements. It is also responsible for several functions including
motor skills such as balance, coordination, and posture.
what makes up the Brain stem
Medulla
Pons
Midbrain
Medulla
autonomic functions i.e. breathing blood pressure heart
rate
Pons –
Relaying sensory information between the cerebrum and
cerebellum, sleep, arousal
Midbrain
It consists of the centre for visual and auditory reflexes.
It is involved in the processing of visual and auditory information. It
regulates eye movement and pupil dilation. It is involved in
regulating muscle movement and motor control
structures in the spinal cord:
Dorsal horns: sensory
nuclei
* Dorsal root ganglia
* Ventral horns: efferent
nuclei
* Ventral root
* White matter:
ascendent or
descendent tracts
[tracts and coloumns]
* Decussation = X
PNS – Cranial nerves
The nerves attached to the brain are the cranial nerves, which are primarily responsible for the
sensory and motor functions of the head and neck (except for one that targets organs in the
thoracic and abdominal cavities as part of the parasympathetic nervous system). There are twelve
cranial nerves.
They can be classified as sensory nerves, motor nerves, or a combination of both. Three of the
nerves are solely composed of sensory fibres (I, II, VIII); five are strictly motor (III, IV, VI, XI, XII); and
the remaining four are mixed nerves.
Neurotransmitter =
Biochemical that mediates fast-acting direct
communication between two neurons (pre- and post-synaptic)
Neuromodulator
Biochemical that modulates activity of neurons and neural
networks by changing the ability of neurons to response to neurotransmitters.
Can act at sites remote from where they are synthesized.
diagram of Chemical synapse process
