Summary of the book used for Brain, hormones and metabolism

CHAPTER 2: FUNCTIONAL NEUROANATOMY

SPECIALIZED CELSS MAKE UP THE NERVOUS SYSTEM

Every organ and muscle in the body is in communication with the nervous
system. The nervous system is made up of cells, most important: Neurons. Each
neuron is a tiny, discrete information-processing unit, receiving inputs from cells,
intergrading those inputs and then distributing the processed information to
other neurons. Even more glia cells provide various forms of support and also
contribute in information processing.

The neuro doctrine proposed that the cells of the brain are independent from
one another structurally, metabolically and functionally and that information is
transmitted from on neuron to the next. The gaps in between the neurons are
called: Synapses.

THE NEURON HAS FOUR STRUCTURAL DOVOSIONS SPECIALIZED FOR
INFORMATION PROCESSING

1. Dendrites: cellular extensions that serve as an input zone, receiving
information from other neurons, can be branched.
2. Cell body: contains the cell nucleus. Receives information and also serves
as an integration zone, combining the information that is received to
determine if it should be send a signal or not.
3. Axon: a single extension, leads away from the cell body and serves as a
conduction zone, carrying the cells own electrical signals away from the
cell boy. The axon may split axon collaterals.
4. Axon terminals: specialized swelling at the end of the axon, are
functional output zone. Transmit the activity to another cell.

NEURONS CAN BE CLASSIFIED BY SHAPE SIZE OR FUNCTION

1. Multipolar neurons: have many dendrites and a single axon, most
common motor neuron.
2. Bipolar neurons: have a single dendrite and a single axon, most
commonly used for sensory systems.
3. Unipolar neurons: have a single dendrite that goes through the
integration zone, cell body is put aside. Such cells transmit touch
information from the body to the spinal cord.

Motor neurons, have long axons, reaching out to muscles or organs and glands.
Sensory neurons carry messages from the periphery to the brain and spinal
cord. Have many different shapes, depending on their function? The majority of
the brain is made up of interneurons, these neurons receive information from
other neurons, process it, and pass it on.

INFORMATION IS RECEIVED THROUGH SYNPASES



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,Dendrites are like tree branches (arborization), dendrites can be covered in
synapses. These synapses transmit information from the axon terminal of the
presynaptic to the receptive surface of the post synaptic neuron. On the
presynaptic axon terminals there are tiny hollow spheres, called synaptic
vesicles, each vesicle contains a neurotransmitter (communication). After
diffusing across the cleft, the neurotransmitter interacts with the postsynaptic
receptors. This action results in an electrical change in the post synaptic cell. the
configuration of synapses is constantly changing, the term used to describe this
continual remodeling is neural plasticity.

THE AXON INTEGRATES AND THEN TRANSMITS INFORMATION


- The axon hillock is the neurons
integration zone, gathering
information from all the synapses
on the neuron’s dendrites and
somas. It is then converting the
information into a code of
electrical impulses to go to the
target.
- Important substances needed at
the axon terminals are loaded into
transport vesicles, hollow spheres
with leglike motor proteins. These “walk the vesicle through the axon to
the terminals. This is called axonal transport. Anterograde to terminal
Retrograde to cell body



GLIA CELLS SUPPORT AND ENHANCE NEURAL ACTIVITY

- Astrocyte
o Receive synapses directly from the neurons and surround and
monitor the activity of nearby neuronal synapses. Protect synapses,
formation new synapses and pruning surplus synapses.
o Can store glucose
o Phagocytes
o Nourishment (glucose, lactate and glycogen)
o Nerve glue
o Play a role in epilepsy
o Communication between neurons
o Respond to brain injury by changing in size, this edema damages
neurons
- Microglia
o Are very small
o The brain cleanup crew: migrate to the sites of injury in the nervous
system and remove debris from injured or dead cells.
o Key component in neural pain system
o Maintenance of synapses in Alzheimer they do not function
properly, might be a form of treatment

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, - Oligodendrocytes
o Produce myelin sheets  insulation multiple axons
o Myelin= 80% lipids and 20% protein
o Node of Ravier: little areas where the axon is not covered in
myelin.
o Loss of oligodendrocytes is linked to schizophrenia
o Defect myelination is linked to Multiple Scleroses
- Schwann cells
o Produce myelin sheets in the peripheral system
o One cell per axon, therefore better in re-growth of an axon
o Also support non-myelinated axons
o Formation of myelin is the same with oligodendrocytes


THE NERVOUS SYSTEM CONSISTS OF CENTRAL AND PERIPHERAL
DEVISIONS

THE PERIPHERAL SYSTEM HAS TWO DIVISIONS

- Somatic nerve system
o The main pathway though which the brain controls movement and
receives sensory information from the body.
o Made up out of cranial nerves and spinal nerves
 12 pairs of cranial nerves
 Three are specifically sensory
 Olfactory  smell
 Optic  vision
 Vestibulocochlear  hearing and balance
 Five pairs are motor
 Along the length of the spinal cord 31 pairs spinal nerves
emerge (one member for each side of the body
 Each nerve has two branches (roots), Dorsal: sensory
projection. Ventral: motor projections
- Autonomic nerve system
o The brains main system for controlling the organs of the body
o Supporting these functions are aggregates of neurons called
autonomic ganglia
o The central neurons that innervate the ganglia are known as
preganglionic automatic nerves; the ganglionic neurons that
innervate the body are known as postganglionic
o Three major divisions
 Sympathetic nervous system
 Prepares the body for action: fight or flight response
 Uses norepinephrine as neurotransmitter
 Parasympathetic nervous system
 Helps the body relax, recuperate and prepare for future
action: rest and digest response
 Uses acetylcholine as neurotransmitter
 Enteric nervous system


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,  Local network of sensory and motor neurons that
regulate the functioning of the gut under control of the
CNS

THE CENTRAL NERVOUS SYSTEM CONSISTS OF THE BRAIN AND SPINAL
CORD

- Cerebral cortex: made up of neuronal cell bodies, dendrites and axons.
The ridges of tissue are called gyri and are separated from each other by
furrows called sulci, these increase the cortex volume.




- There are multiple lobes in the brain:
o Frontal lobe
 High cognitive function
o Parietal lobe
 Receives sensory
information from the body
and participates in spatial
cognition
o Temporal lobe
 Sense of smell, hearing and
aspects of learning and
memory
o Occipital lobe
 Vision
o Some of the ridges between the lobes are very clear: Silvian
fissure, divides the temporal from the other regions of the
hemisphere.
- Corpus callosum: axons across the midline in a large C-shaped bundle
enabling communication between the two hemispheres




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