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NMS Summary
Nerves
-Cell excitability
Membrane potential = Em which is effected by multiple ions
Em ≠ Eion because there is an imbalance in electrical and chemical forces
Resting membrane potential of -70 mV is achieved by ion movement across the membrane
(through carriers as not lipophilic)
The potential is achieved by ion distribution due to K+ efflux and Na+ influx and the potential also
influences the movement of these ions
Different protein carriers:



One for each different ion e
...
g
...

The Na+ ion channels open first for
depolarisation and then K+ channels open
during repolarisation
...

-Neurones
The Central nervous system comprises of the brain and spinal cord and the
Peripheral nervous system is the nerves that run away from the CNS
...

The Myelin sheathes are produced by different cells depending on the location of the neurone
...

Glial cells also can myelinate the
neurones as well as providing physical
and metabolic support for the
neurones bringing the neurones close
to blood vessels forming the blood
brain barrier






Fibrous astrocytes are found
in the white matter
Protoplasmic astrocytes are
the glial cells of the grey
matter
...

Ependymal cells line the cavities in the CNS with cerebral spinal fluid (CSF) which coats the
spinal cord and provides buoyancy in the brain
...

In the synaptic bouton, located at the distal end of the neuron, there are many mitochondria and
secretory granules for the release of neurotransmitters
...
Not all axons are myelinated however and some can be unmyelinated
...

A single neurone is surrounded by the endoneurium, and
the nerves all come together into a fascicle which is
surrounded by the perineurium
...

Motor neurones: these are multipolar neurones and are
found in the ventral root
Sensory neurones: these are unipolar neurones and are found in the dorsal
root
...
Within the cell body
there is a large amount of protein synthesis,
creating new proteins for the plasma membrane
and proteins for the membranes of
neurotransmitter vesicles
...
Therefore when the nucleus is damaged or the mechanism
of communication between the cell body and the distal cytoplasm is interupted then the cell
undergoes changes
...
In the peripheral nervous system if there is only axonal damage then
there is a possibility of recovery
...

- Neurone damage
Neurone damage can occur due to many different reasons:




Ischaemia – lack of blood supply to the nerve can cause it to become damaged due to lack of
respiratory materials
Trauma by direct damage such as knife damage or indirect damage due to compression of
the nerve
Diseases such as motor neurone disease
...

Here the nucleus pulposus herneates through the annulus fibrosis and
crushes the rami, causing severe pain, reduced movement and spinal ache
...

The ends swell due to axonal transport along microtubules in the cytoskeleton made of
kinesin and dynein still carrying molecules in a reterograde and anterograde direction leading
them to become irregular in size
...

In days to weeks the schwann cells become phagocytic and with the aid of macrophages they
degenerate the axon in Wallerian Degeneration, by this same process 3 or 4 nodes
closest to the trauma zone on the proximal end are cleaved inorder to leave a smooth end
for reinnervation to occur
...


Weeks to months
if the correct neuronotrophic factors are in place within the nerve along with active schwann cells
then they can lead to the reinnervation of the motor neurone, in addition to this the nerve requires
the correct specific growth proteins to be present in conjunction with the endoneurial sheath being
intact
...





Schwann cells align longitudinally within the endoneurial sheath
The growth cone reaches the end of the proximal segment of the axon, near to the
laceration site
 Axon sprouts extend out of both ends of the
laceration to bridge the gap between the two ends,
many axon sprouts enter the opposite end, however
only one axon sprout remains within that side
...
Small motor neurones dictates a type I nerve to be created and large motor
neurones results in type II fibres
...

Type of damage to the nerve: transient nerve damage (neurapraxia) is the most likely to
be able to recover as it is just damage to the myelin sheath instead of the axon and so more
schwann cells can align and help with the myelination of the axon
...

Neuronotmesis occurs mainly in lacerations and is a complete section of the nerve, where
the whole nerve including connective tissues is severed and so the chance of reinnervation is
very slim and surgery is the only way in which reinnervation can occur, surgery is carried
out by stitching the perineurium back together, however it is not guaranteed that it will
result in reinnervation
...


- Consequences of nerve damage
Hours: fasciculations and fibrillations occur in the muscle distal to the trauma site
Days-Weeks: Fibrillation followed by full paralysis distally to the traumaa
Weeks-Months: Atrophy occurs in both the muscle and bone found distally to the trauma
...
If autonomic nerves are damaged then we
can see hot dry skin occuring in addition to nail growth retardation and bone decalcification
...

Synapses

-Gap Junction
This is a fast and primitive form of communication between adjacent cells which transfers ionic
current bi-directionally
...


-Chemical synapse
A slower unidirectional synapse which involves
the transport of neurotransmitters from the
synaptic bouton to the postsynaptic
membrane
...

2
...

4
...
The transmission is terminated quickly by re-uptake of the neurotransmitter and also Ach
can be broken down into Acetate and Choline by Acetyl Cholinesterase
Neurotransmitters:
Excitatory – Glutamate
Inhibitory – GABA
These are the main ones however there are more than 100 different neurotransmitters
Neurotransmitter receptors:
These are membrane spanning protein molecules which undergo a conformational change to
pass on the signal
...
Two types:



Ionotropic – transmitter binds, conformational change, channel opens, ion movement
Metabotropic – transmitter binds, conformational change, G-protein is activated which
activate effector systems, ion channels are indirectly opened or closed, inhibiting or
exciting second messenger/enzyme systems

Ionotropic receptor action neurotransmitter binds and opens protein ion channels so sodium can
get through and depolarise the membrane if excitatory, if inhibitory binds then Cl- ion channels open
and allowing Cl- to move into the neurone, hyperpolarising the membrane
...


- Neuromuscular Junction
The neuromuscular junction is a chemical synapse between a motor neurone bouton, and the
sarcolemma of a skeletal muscle myofibril at the motor end plate
...


If there is an action
potential in the presynaptic neurone
then there will always be
depolarisation of the sarcolemma

There are many junctional
folds at the motor end plate which
allows for a higher density of
receptors

There is only excitatory
input into muscles

There is only one
neurotransmitter at neuromuscular
junctions: ACh

There is only one receptor
at the neuromuscular junction:
Niotinic Cholinergic receptors

When Ca2+ enters the
presynaptic bouton it binds to
synaptotagmin causing a
conformational change which stimulates vesicles to carry out exocytosis
2 Acetyl choline molecules binds to a single
nicotinic receptor (Ligand gated ion channels, made
up of 5 sub units) on the postsynaptic end plate,
which causes the channel to open causing the
membrane to become permeable to sodium and
potassium ions
...
In order for a sustained
contraction to occur the muscle fibre must be receiving action potentials at a rate of 40 Hz
...

Dihydroxypyridine protein receptors are found on the surface of the sarcoplasmic reticulum and
they reach to the sarcolemma, when depolarisation of the sarcolemma occurs a conformational
change occurs which causes the ‘plug’ to be pulled out of the reticulum and allow calcium out
...

The action potential is propagated along the sarcolemma by Ttubules
...

There are many drugs that can inhibit the action of the
neuromuscular junction:









Vesamicol can inhibit the carrier transport of ACh
into the vesicle
...

Presynaptic toxins such as the botulinum toxin are capable of inhibiting the exocytosis
of the ACh vesicle, as their subunits cleave the protein involved in exocytosis
...
These drugs are contraindicated in burns patients because the
depolarisation can lead to an efflux of K+ ions and can cause a cardiac arrest due to the
reduction in excitability of the cardiac muscle
...

Anticholinesterases are also used to inhibit AChE action so ACh is not degraded so
continues to cause depolarisation
...
The muscle weakness occurs in skeletal muscle which undergoes
sustained activity, as the eyes muscles are the most active (due to saccades)
...

- Raynaud’s syndrome
Hyperactivity of the sympathetic nervous system causes over constriction of the blood vessels at
extremities and in stressful situations the loss of blood can cause pain to the individual
...
Usually this only
affects one side of the face at once and so shows one eyelid drooping, uneven iris sizes and only one
side of the face being dry
...
There are three types of G-protein Gs, Gi

and Gq
...
M1 receptors are found in the enteric nervous system controlling secretions into the GIT
as well as being found within the central nervous system
...
The M3 receptors are in control of contracting smooth muscle within the GIT, in addition to
this they control the endocrine and exocrine function of the body
...

Muscarinic receptors are antagonised by atropine which is useful in combatting bradycardia and
hyperhidrosis
...

- β-Adrenoreceptors
These are also G-coupled receptors which are activated by adrenaline and noradrenaline which
detaches and binds to adenylyl cyclase to activate it in order to convert ATP to 3’,5’ cAMP
...
Antagonists
such as propranolol result in a lowering of the heart rate so can result in dizziness, fatigue and
venous pooling as there is not sufficient blood pressure to allow the blood to be supplied to all areas
of the body at sufficient pressures as bradycardia ensues
...

If these symptoms arise then it is possible to use drugs such as somatostatin to maintain blood
pressure or to use compression stockings in order to maintain pressure on the body to keep the
blood pressure up throughout the body
...
They are important in our protection,
postural control and homeostasis
...
Alternatively the reflex arc can bypass the CNS all
together
...

 Stretch reflexes (myotatic)

If the muscle is put under tension then spindles within the muscle are put under tension and
stretch mediated ion channels in the membrane open and the muscle is sent a message to
contract
...

 Golgi tendon organ reflex
When the muscle is overworked and contracts too much the Golgi tendon organ, an organ
found within collagen fibres of tendons, is excited and the action potential travels to an
inhibitory inter neurone which causes the muscle to stop contracting
...
The other branch of the
afferent neurone from the spindle fibre synapses at an inhibitory interneuron which causes
the hamstring to be relaxed to allow the knee to jerk
...

Receptor: muscle spindle
Afferent nerve: trigeminal (CN V)
Central component: Pons
Efferent nerve: trigeminal (CN V)
Effector: Masseter
 Gag reflex when there is sensory stimulus that reaches the soft palate or the posterior of
the oral cavity which is detected by the trigeminal nerve or glossopharyngeal nerve
respectively, it is a monosynaptic reflex and results in the elevation of the soft palate and
contraction of the pharynx
Receptor: pressure receptors within the soft palate or posterior section of the oral cavity
Afferent nerve: Hypoglossal nerve (CN XII)
Central component: medulla, the nucleus of the solitary tract and the nuclear Ambiguus
Efferent nerve: Vagus (CN X) with some glossopharyngeal (CN IX) input
Effector: muscles of the tongue and larynx
 Swallowing reflex the first part of deglutition is controlled voluntarily however when it
reaches the pharynx, reflexes take over
...
Causing the larynx to close, the
oesophageal sphincter to open and for the glottis to close
...
To change
contractile force only certain slow twitch motor units are activated for smaller forces, the strength
is determined by the number of fascicles innervated by the motor unit
...
Motor units are always recruited from Weakest
to Strongest
...


Muscle contraction mechanism
1
...
Ca2+ binds to troponin which causes a conformational change, moving tropomyosin
out of the myosin binding site
3
...
The myosin head moves forward in a power stroke contracting the sarcomere
5
...

- Diseases of the Motor Unit
These diseases are usually hard to diagnose and manage, all of them interrupt the action of the
motor unit







Motor neuronopathies are problems with the cell body of the motor neurone e
...
g multiple sclerosis
(demyelinating) and Guillain-Barré syndrome (autoimmune response which destroys the
axon) can be inherited or acquired
...

Disorders of transmission occur when there is a fault at the neuromuscular junction, such as
the bouton being too far away from the muscle fibre or not enough ACh being produced by
the presynaptic knob
...
g Duchenne muscular dystrophy, an X linked recessive disorder which causes dystrophin
not to be formed correctly so it is not present in the sarcolemma meaning that excessive
Ca2+ can move into the muscle, as well as the linkage of the contractile proteins being
unable to be attached to the extracellular matrix, can’t be cured
...
Fasciculations can also arise due to spontaneous depolarisation of the
muscle fibre as it has become hypersensitive due to the lack of innervation it has been receiving,
reflexes are also reduced or non-existent
...
Patients suffer with weakness, atrophy and fasciculations
...
Aetiology is unknown, but it has been observed that in

patients the proteins of the neurone membrane are not broken down effectively so protein
misaggregation occurs which results in the death of the motor neurone, glutamate exotoxicity has
also been theorised to add to this to lead to the cell death
...

Movements










Flexion – decreasing the angle between two body parts
Extension – increasing the angle between two body parts
Abduction – movement away from the midline
Adduction – movement towards the midline
Circumduction – conical movement of a bodypart
Supination – turning a body part so the palm or sole faces anteriorly
Pronation – turning a body part so the palm or sole faces posteriorly
Eversion - the movement of the sole of the foot away from the median plane
Inversion - the movement of the sole towards the median plane

Pennate structures are feather like structures with long parallel
tendons and short muscle fibres arranged at an angle, the more
pennate structures means more muscle fibres can fit in so the more
powerful the muscle is
...
Sesamoid muscles can develop such as the patella in the tendons that are prone to
compression
...
Also found in the hand
...

Fascia are sheets of fibrous tissue, mostly collagen, which allow attachment of muscle, they are
commonly used as an anchor for the muscles of facial contraction, and the face’s fascia is superficial
...


Loose connective tissue is loosely arranged fibres which form a meshwork which binds tissue
whilst maintaining movement, often found in structural support of organs, glands, blood vessels
and nerves
...
However we can find irregularly orientated DCT in the dermis
...
It is made of:






Fibres, usually collagen or elastin and provide structure and elasticity
Ground substance, large polysaccharide substances on proteins (glycosaminoglycans)
which the fibres of the connective tissue embed themselves in
Fibroblasts are the most numerous cells in connective tissue and are responsible for
the production of the fibres and ground substance
Within the tissue there are macrophages to destroy invading pathogens, and mast
cells which contain histamine which is important in inflammation
Adipose cells are also found within skin and are unilocular in adults yet multilocular
in children

Structure
Loose

Dense
regular

Function
- Metabolic exchange
- Communication between tissues
They are delicate and flexible, are
well vascularised but not resistant to
stress

- Providing structural stability
- Mechanical support
- Protection
They are more resistant to stress
but less flexible and due to the
arrangement of the collagen fibres
they are resistant to traction forces

Examples
 Adipose
tissue
 Epithelial
tissue
 Muscle and
neurones




Bone
Tendons
Ligaments

Dense
irregular

- Metabolic support
- Elasticity
- structural stability



dermis

- Cartilage
This is a highly resistant connective tissue which provides support and is the precursor to bones in
foetuses
...
Found in the ear, epiglottis and Eustachian tube
Fibrocartilage has many collagen fibres however sparse ground substance and also contains
mostly type 1 collagen as well as some type 2
...

Hyaline cartilage is surrounded by the perichondrium and contains mostly type 2 collagen
and the ground substance, it allows for friction free movement and is also a good supportive
tissue
...


- Dental connective tissues







Oral mucosa
Periodontal ligaments(fibres) – holds the
tooth in place along with other collagen fibres
Alveolar bone
Cementum – holds the tooth in place
Dentine
Dental pulp – the living component of the
tooth with nerves and blood vessels

The protein fibres that make up these connective
tissues are synthesised by Fibroblasts, and they get embedded into the Extracellular matrix which
then aggregate into fibres to create mechanical and tensile strength (collagen) or elasticity (elastin)
...
There are also many immune cells and
stem line cells within the tissue
...
The
lattices formed give some collagen a limited ability to stretch
...

-Ground Substance







Proteoglycans

Provides unstructured extracellular material to fill the space between cells and fibres
Provides an environment for the laying down and maturation of protein fibres during tissue
development and turnover
Holds water
Provides support for normal cell function and migration
Helps in the mineralisation of connective tissues
Made of Proteoglycans and glycoproteins

Glycoproteins






These are proteins with many
glycosaminoglycan chains attached
They attract water and act as a
lubricant and shock absorber
Can bind to many proteins such as
growth factors
Aid in collagen fibril formation





Conjugated proteins with short irregular hetero/oligosaccharide
sidechains bound to a polypeptide chain
Often found in the cell membrane and used for cell adhesion and
migration as well as mineralisation, can be also used to link cells
and the ground substance within the extracellular matrix
...


The Spinal Cord
There are 7 cervical vertebra, 12 Thoracic vertebra, 5 lumbar
vertebra and 5 fused sacral vertebra
...
The spinal cord runs from the foramen magnum to between
L1 and L2
...

The spine provides protection for the spinal nerves due to its bony
nature
...
Within
the spine haematopoiesis occurs and the cells produced travel out
through the venous plexus
...

In the spine the spinal nerves are surrounded by meninges which keep the nerves safe from chemical
and physical damage
...

The nerves exit the spinal cord through roots out
of the column and leave to travel through the rest
of the body
...

Grey matter contains the cell bodies of the
neurones wheras the white matter is the
myelinated axons of the spinal nervesconnec



Vertebrae

Vertebrae consist of the body of variable sizes depending on
their location within the spine, with those that are located more
inferiorly tending to be larger
...
On the superior and inferior surfaces of
vertebra there are also 2 articular processes where they articulate with other vertebrae
...



Cervical vertebrae

Have a small kidney shaped body and the largest vertebral foramen in the spine as the spinal
cord is largest at the top, they also possess transverse processes and foramina
...
However not all Cervical vertebrae fit this
description:
 C1 – Atlas: has no body just the anterior arch
and articular facet, there is also a distinct lack
of spinous process, only the posterior
tubercle can be seen
...


If these vertebrae are damaged in any way or are compromised
then there can be large damage to the spinal cord, fracture to the
vertebrae can cause paralysis due to severing of the nerves,
Intervertebral disks can also herniate and cause the nerve to be
crushed
...
The fascia are very
strong and are made of dense connective tissue formed into very thin ligaments or tendonsco
...
The superficial fascia of the neck is mainly
adipose tissue
...







The muscles in this part of the neck are divided as
to where they lie in relation to the hyoid bone
...

The common carotid artery passes through the anterior triangle, and bifurcates within the
triangle into the external and internal carotid arteries
...

The cranial nerves in the anterior triangle are the facial [VII], glossopharyngeal [IX], vagus
[X], accessory [XI], and hypoglossal [XII] nerves
...
The main contents of the carotid triangle
are the common carotid artery (which bifurcates within
the carotid triangle into the external and internal carotid
arteries), the internal jugular vein, and the hypoglossal (CN XI) and vagus (CN XII)
nerves
...
It contains the infrahyoid
muscles, the pharynx, and the thyroid, parathyroid glands
...
It contains
the lymph nodes
...
It
contains the submandibular salivary gland, the lymph nodes and
also the facial artery and vein pass through here
...

A significant muscle in the posterior triangle region in the omohyoid
muscle
...
The inferior belly
crosses the posterior triangle, splitting the triangle into two
...

The vasculature within the posterior triangle
includes the external jugular vein which empties into
the subclavian vein
...

The accessory nerve CN XII may also be found
within the triangle in addition to the cervical plexus
which branches into the phrenic nerve, other
branches provide cutaneous innervation to the face
and neck
...


The Skull
This is important in the protection of the brain, brainstem and special sensory tissues, and within it
the cranial nerves and spinal cord allows for communication with the rest of the body
...
The
nasal cavity is also important in
ventilation
...
The pterion is a
region of very thin bone where the
temporal, frontal, sphenoid and parietal
bones come together and so there are many sutures here, making it extremely susceptible to a
direct blow, and due to the anterior branch of the middle meningeal vessels lying underneath this
area of the skull if is damaged then an extradural haemorrhage can occur
...
The cranium is very
angular and there is a shallow, toothless mandible
...
The metopic suture exists at the front of the
cranium and holds the two frontal bones together
...


Orbicularis oris does not attach to bone
and is important in mastication, injestion and
articulation
...
It is important in
mastication as it compresses the cheeks to
the occlusal surface of the teeth
...

Orbicularis occuli has three parts:
-

Orbital part which squeezes the eye
shut
The Palpebral part which controls blinking
The lacrimal part which empties the lacrimal sac, causing tears to form

The muscle is innervated by the frontal and zygomatic branches of the facial nerve (CN VII)
Levator palpebrae superioris inserts into the upper eyelid and controls the opening of the
upper eyelid, it is innervated by the oculomotor nerve (CN III)
Zygomaticus major and Zygomaticus minor both attach to the zygomatic arch to the
corners of the mouth and enable smiling
...

Damage to the facial nerve can lead to unilateral paralysis of the face so one side is unable to
express emotion
...
Due to paralysis there is a loss of tone in the side of the face
affected so the crow’s feet disappear
...
The muscles of the eye receive
innervation from a variety of nerves, the superior, medial and
inferior rectus as well as the inferior oblique all receive innervation
from the Oculomotor nerve (CN III), the Abducens nerve (CN VI)
is responsible for the innervation of the lateral rectus muscle and
the superior oblique muscle is controlled by the Trochlear nerve
(CN IV)


Muscles of Mastication

There are four muscles involved in mastication and they are all innervated by the mandibular
branch of the trigeminal nerve (CN V):

 Masseter – attaches from zygomatic arch to the ramus of the mandible, controls
elevation of the mandible
 Temporalis – arises from the temporal fossa and attaches to the coronoid process to
help in the elevation of the mandible as well as retraction
 Medial pterygoid – arises from medial side of lateral pterygoid plate and medial aspect
of the lateral pterygoid plate and is important in the elevation of mandible, can also be
used to grind
 Lateral pterygoid – attaches to lateral aspect of pterygoid plate to the coronoid
process of mandible aids in the protrusion of the mandible can also be used to grind


The Scalp
Comprised of 5 layers:
- Skin
- Connective tissue (superficial fascia)
- Aponeurosis of occipitofrontalis
- Loose connective tissue (areolar, provides
metabolic support to the skull and muscles)
- Pericranium (vascular connective tissue
surrounding the skull)



Temporomandibular Joint
Consists of the condylar process of the
mandible which fits into the mandibular fossa,
the articular disc sits between these two
surfaces and acts as a lubricant, as well as
being surrounded by synovial fluid
...
Upon
opening of the mouth the condylar process
moves out of the mandibular fossa and onto
the articular surface
...

Jaw ache is often due to the articular disc moving onto the articular surface when the jaw is
opened and then remaining there and not returning to the articular fossa and so when the jaw
closes the condylar process returns but comes into contact with retrodiscal tissues which is very
painful
...

The mandible is attached to the cranium by two ligaments: the Sphenomandibular
ligament which attaches the inner aspect of the mandible to the sphenoid bone, and the
Stylomandibular ligament connecting the styloid process to the posterior section of the
mandible
...




Hyoid bone

A free floating bone located within the neck, superficial to
the larynx and inferiorly to the mandible
...

The suprahyoid muscles are the digastric, mylohyoid,
stylohyoid and Geniohyoid; and are involved in the
elevation of the hyoid and consequently larynx
...

If fracture occurs to the hyoid bone then the person will be
unable to breathe, as the bone suspends the larynx
...
Have a general
structure of an aromatic ring, which makes the substance lipid soluble, with a linkage (which can
be an amide or ester group) to a basic amine group
...

In more acidic conditions the amine group becomes more ionised to form an equilibrium with
the body, at physiological pH there is a higher concentration of the ionised form of the drug,
only the unionised form of the local anaesthetic can cross the membrane and therefore only the
unionised form can have a functional effect, meaning that if there is an infection or inflammation
where the pH is increased the anaesthetic is less effective
...

Local anaesthetic is indiscriminate in its action and can affect both motor and sensory
neurones however sensory neurones are more sensitive to its effects so the correct neurones are
largely targeted even if it does have some inhibitory effect on the motor control
...
Infiltration anaesthesia is applied near to
the terminal nerve ending to interrupt innervation to a local area such as a single tooth, whereas a
Nerve block anaesthetic is primarily used to anaesthetise a whole section such as a side of the jaw
where one would inject in the angle of the mandible
...


Bones and Teeth

Bones are important in calcium storage, homeostasis and metabolism, Calcium is important
physiologically and also in cellular signalling
...
Bones are also mineralised by calcium in
calcification
...

Osteoclasts: multinucleated cells responsible for bone resorption often found at the
periphery of bone
Osteoprogenitor cells: the stem cells of bone, used to remake bone after damage

Surrounding the trabeculae of bone is marrow which can either be red marrow which is found in the
ends of bones and is involved in the production of new red blood cells, or yellow marrow which is
found along the length of the bone and is an adipose store
...
This means that the
communication with osteoblasts and osteoclasts is extremely important
...

- Outermost layer of compact bone merge
with dense cortical bone
- Innermost layer merges with trabecular
bone

- Components of the bone matrix
Collagen (type I), proteoglycans, matrix proteins, growth factors, calcium hydroxyapatite crystals
- Ossification
Intramembranous ossification is the formation of usually flat bone from hyaline cartilage and fibrous
membranes
...

Endochondral ossification occurs in all bones below the skull and involves the ossification of the
hyaline cartilage in the early embryo
...
The blood vessels deliver new nutrients which
stimulate mesenchymal cells to differentiate to osteoblasts which gather at the outer edge of the
bone wall, to create a bone collar
...
Meanwhile more cartilage is deposited by chondrocytes at the
distal ends of the bone lengthening
...
Osteoclasts delivered by the bud travel to the outer edges of the cavity and further
degrade the cartilage to create more space, in contrast to this blasts now create trabeculae to
create new spongy bone (bone is still elongating)
...
At the start of the epiphyseal plate
ossification occurs
...

- Mineralisation
This occurs when there is insufficient serum free calcium or phosphate levels in order to precipitate
hydroxyapatite crystals and so the extracellular matrix is mineralised instead
...
The vesicles are
derived from the plasma membranes of Osteoblasts, Cementoblasts and Odontoblasts and they have
high concentrations of alkaline phosphatase which aid in the hydrolysis of inorganic pyrophosphatase,
and mineralisation
...
Within the vesicles the ions mineralise and form a crystal within the
vesicle that eventually grows and bursts the membrane of the vesicle, it is possible for these crystals
to stick together to form a centre for further calcification
...
Under normal circumstances calcium is unable to bind to collagen however acid
phosphoproteins are able to bind to both calcium and collagen and so the protein provides an
excellent starting point for crystal formation on collagen fibres
...

Mineralisation in bone and dentine
 Occurs by both matrix vesicles
and heterogeneous nucleation
 The HAp crystals seed onto
collagen fibres
 Mineralisation is controlled by
phosphor-glycoproteins and
proteoglycans between the un

Mineralisation in enamel
 Only occurs by heterogeneous
nucleation
 Does not use collagen as a
scaffold, the crystals form on
enamel proteins
 Tuftelin, enamelin and
amelogenin regulate crystal
growth

mineralised and the mineralised
tissue
Fluorosis occurs when excess fluoride is digested by people during tooth development and can lead
to hypomineralisation or hypoplastic (incomplete development of) enamel
...
Teeth appear to
be mottled or simply have faint flecking in the enamel
...
This results in sufferers being more likely to have skeletal
deformities and bone pains
...
This
results in similar symptoms to osteoporosis with bone loss, leading to the patient having bone
imperfections and being more susceptible to fractures
...
Hypomineralised teeth have normal appearing enamel however it
is very weak and is worn away easily and so people are left with little enamel at a young age
...
m

Teeth
- Enamel










Has a prismatic structure (full of prisms) of
hydroxyapatite crystals packed together –
hydroxyapatite has the general structure
Ca5(PO4)3(OH,F,Cl) with the last group being
optional and each has different properties:
- F improves resistance to caries
- CO3 makes more susceptible to caries
Ion substitutions can occur if the ions are the
same size
The hardest and most highly mineralised tissue in the body as 96% of the tissue is inorganic
component
The organic component consists of proteins exclusive to dentine: amelogenins and nonamelogenins
...

The mineralisation of enamel does not use matrix vesicles and only utilises heterogeneous
nucleation, however the site of nucleation is not associated with collagen and the nucleation
instead occurs within the matrix
Some nucleation is able to occur immediately when the matrix is secreted by the
ameloblasts






The matrix of the enamel is removed during maturation to provide more space for the
inorganic content
...







The tubular structure of dentine is formed by odontoblasts, which also aid communication,
dentine starts as predentine which is laid down before being mineralised
...
Tertiary dentine is produced by
odontoblasts after the tooth has undergone assault or external stimuli have been applied
...

Within dentine there is the inorganic Hydroxyapatite
crystals which makes up 70% of the dentine (slightly
more than bone), and the crystals are smaller than those
found in enamel
...


- Cementum




Cell biology
Structure

Provides attachment of the teeth to collagen fibres of periodontal ligaments
Similar to bone in chemical composition and properties but is avascular and not innervated
Can be repaired and regenerated
Bone
Osteoblasts, Osteocytes,
Osteoclasts

Enamel
No cells

Woven bone has a loose
and disorganised structure
of calcified collagen
...


Many
hydroxyapatite
crystals

Dentine
Odontoblasts,
Odontocytes,
Odontoclasts
Tubular structure
...

The muscles of the tongue are all innervated by the hypoglossal nerve both the intrinsic and extrinsic
muscles apart from the palatoglossus muscle which runs from the palatine process into the tongue
...

The intrinsic muscles include the superior longitudinal musle which moves the apex of the tongue
superiorly, the vertical muscle that flattens the tongue, the transverse muscle which protrudes the
tongue and the inferior longitudinal muscle which lowers the apex
...
The innervation it
receives can be both visceral and somatic external information
...
Uses acetyl
choline at the ganglionic synapse and noradrenaline at the effector, however, at sweat glands the
innervation is sympathetic however acetylcholine is used as the neurotransmitter at the effector
...
Uses acetyl choline at the
ganglionic synapse and acetylcholine at the effector but with a muscarinic receptor
...

Parasympathetic action
Heart rate decreases
Constrict
Constrict
Dilate
Dilate
Constrict
Increase
Storage of glucose as glycogen
Erection
Reduced
Circular muscle contracts, constricting the
pupil
Increased salivary production
Reduced adrenaline produced
Increased urine secretion
Bladder contracts, sphincter relaxes

Heart
Coronary arteries
Skeletal muscle blood vessels
Visceral arteries
Skin arteries
Bronchi
Gastro-intestinal tract peristalsis
Liver
Penis
Mental acuity
Eye
Salivary glands
Adrenal medulla
Kidneys
Bladder

Sympathetic action
Heart rate increases
Dilate
Dilate
Constrict
Constrict
Dilate
Reduces and sphincters tighten
Liberates glucose from glycogen
Ejaculation
Hightened
Contraction of the radial muscle, dilating the
pupil
Reduced salivary production
Increased adrenaline production
Reduced urine secretion
Bladder relaxes, Sphincter contracts

Somatic innervation arises from the ventral horn of the spinal
cord and the efferent neurones are without ganglia and travel
straight to the effector without synapsing and all neuromuscular
junctions are nicotinic cholinergic synapses
Autonomic innervation arises in the lateral horn of the spinal
cord or within the brain
...
The postganglionic fibres cell body is located within the
ganglion and the axon is unmyelinated making the nerve more
vulnerable to damage and also the transmission is slower
...
In a normal human there is
roughly 1 preganglionic fibre to 35 or more postganglionic
fibres
...
In contrast to this the parasympathetic nervous
system originates from the brain and brainstem as well as the sacral vertebrae S2 – S4
...
The
sympathetic nerve fibres do
not all synapse at the same level and many can travel up or down the sympathetic chain to synapse in
different ganglia
...
These prevertebral ganglia are associated with the branches of the aorta to aid in the
distribution of the postganglionic fibres by the blood vessels
...


The afferent nerves of the sympathetic nervous system
travels through the sympathetic ganglion in order to reach
the dorsal root ganglion where it can reach the dorsal
horn
...


Direction of Fibre
Location of Ganglion
Target example
Immediate synapse
Same level
Skin by sympathetic nerves
Ascend chain
Cervical ganglia
Head and Neck
Descend chain
Lumbar and sacral ganglia
Reproductive organs
Traverse chain
Prevertebral ganglia
Stomach and GIT
There is always some sympathetic innervation to blood vessels which creates tonic vasomotor tone
to maintain some contraction within the walls of the blood vessels
...

The adrenal medulla is an exception to the sympathetic nerves synapsing in ganglia as the medulla is
directly innervated by preganglionic nerve fibres
...
Adrenaline is particularly useful in the excitation of noninnervated tissues such as the smooth muscle of bronchioles
...
Unlike the sympathetic nervous system the preganglionic fibres are long and they synapse in
ganglia proximal to the target tissue
...


Pterygopalatine
Ganglia – Lacrimal gland

As the visceral (the not consciously perceived information) and
somatic fibres pass through the same spinal nerve, organ pain can
often be misinterpreted by the patient as cutaneous pain from a
different part of the body
...


- Enteric Nervous system
Makes up the 3rd division of the Autonomic Nervous system in conjunction with
Myelinated
the sympathetic and parasympathetic nerves
...
Although the
ENS can operate on its own it receives
innervation from the central nervous system as
well, with the level of integration varying at
different locations, it interacts with the central
nervous system by communicating with the
sympathetic and parasympathetic nervous systems which in turn connect to the CNS
...

Components of the enteric nervous system
- Receptors: Mechanoreceptors which detect distension in the wall of the gastrointestinal tract,
Chemoreceptors detect chemicals within the food
...
Excitatory interneurons secrete acetyl choline whereas inhibitory interneurons have a large
range of neurotransmitters
...

Excitatory motor neurones use ACh, Substance P, Serotonin (5-HT) and the inhibitory
neurotransmitters use a large variety of peculiar neurotransmitters such as Nitric Oxide, Vasoactive
intestinal peptide (VIP) and ATP amongst others
...

The submucosal plexus controls intestinal secretions of acid, enzymes and mucus; and also aids in
peristalsis through reflexes, involving afferent neurones, interneurons and efferent neurones
...

The muscles must first contract to for the
bolus in the forward direction and in front
there must be relaxation to
allow the bolus to pass
RELAXATION
forwards, giving the need for
inhibitory interneurons
...

Chaga’s disease is caused by the trypanosome parasite which breeds within the GIT and secretes a
toxin which damages the neurones of the enteric nervous system
Irritable bowel syndrome is a non-pathological disease which is the result of a dysfunctional
interaction between the CNS and ENS, there are drugs available for the treatment of the disease
however they can affect neurotransmitters elsewhere in the body
...
Radio waves are passed
through the subject which knocks the body’s protons out of alignment so when the radio waves are
turned off the protons realign and emit radiation which shows up and varies in intensity depending
on the proton density of the tissue so an image can be obtained
...
Useful in conjunction
with other images to determine activity within the body
Ultrasound – high frequency sound waves are passed through the body and get reflected from
tissues within the body which create an electrical impulse when returned to the scanner which can
be interpreted into an image
...

For imaging on a smaller scale (histology) the specimens must be prepared prior to this, the stages
are as follows:
1
...
Alcohol solutions in increasing concentrations are used to remove all water from the
sample, then it is cleaned by xylene to remove the alcohol
3
...
Samples are then stained and viewed
The stain used is dependent on what is wanted to be viewed:




Haematoxylin and Eosin – Eosin is an acidic dye that stains basic compounds pink
and haematoxylin is a basic dye which can stain acidic compounds purple
Periodic acid Schiff – stains carbohydrates and compounds rich in carbohydrates
magenta
Masson’s Trichrome - Nuclei and other basophilic structures are stained blue,
cytoplasm, muscle, erythrocytes and keratin are stained bright-red
...




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