HNN Week 2 Flashcards
1
Q
Describe the muscles in the face and their function:
A
See drawing p4 HNN stripy notes
MAIN MUSCLES
- frontalis - moves scalp and wrinkles forehead (has a posterior belly called occipitalis at posterior of head and the two are connected by aponeurosis)
- platysma - tenses skin of lower face and neck
- corrugator supercili - draws eyebrows medially making the vertical forehead wrinkles
EYE MUSCLES
- obicularis occuli (palpebral and orbital part)
NASAL MUSCLES
- nasalis - flares nostrils
- procerus - depresses medial end of eyebrow
ORAL MUSCLES
- obicularis oris - closes mouth and puckers lips
- buccinator - draws cheeks in
UPPER ORAL MUSCLES
- risorius - moves corner of mouth lateral and superior
- zygomaticus minor - smiling
- zygomaticus major - smiling
- levator labii superioris - elevates upper lip AND deepens furrow between nose and mouth when sad
- levator labii superioris alaeque nasi (Little Ladies Snore All Night) - lifts upper lip and flares nostrils
- levator anguli oris - for smiling and deepening furrow between nose and mouth when sad
LOWER ORAL MUSCLES
- depressor anguli oris - moves corners of mouth down
- depressor labii inferioris - depresses lower lip
- mentalis - protrudes lower lip and wrinkles chin
2
Q
Describe the three muscles surrounding the ear and their function:
A
- posterior auricular muscle (retracts and elevates ear)
- superior auricular muscle (elevates ear)
- anterior auricular muscle (elevates and moves ear anteriorly)
3
Q
Describe the 4 muscles of mastication and their innervation:
A
1 - masseter (most superficial and largest, elevates mandible)
2 - temporalis (elevates mandible)
3 - medial pterygoid (elevates mandible, quadrangular with two heads)
4 - lateral pterygoid (moves jaw side to side and protracts mandible, triangular with two heads)
All receive motor innervation from the trigeminal nerve
4
Q
What is the innervation of each of the facial muscles?
A
MAIN MUSCLES (3)
- frontalis (temporal branch)
- platysma (cervical branch)
- corrugator supercili (temporal branch)
EYE MUSCLES (1) - obicularis occuli (palpebral and orbital part) (temporal and zygomatic branches)
NASAL MUSCLES (2)
- nasalis (buccal branch)
- procerus (buccal branch)
ORAL MUSCLES (2)
- obicularis oris (buccal branch)
- buccinator (buccal branch)
UPPER ORAL MUSCLES (6)
- risorius (buccal branch)
- zygomaticus minor (buccal branch)
- zygomaticus major (buccal branch)
- levator labii superioris (buccal branch)
- levator labii superioris alaeque nasi (buccal branch)
- levator anguli oris (buccal branch)
LOWER ORAL MUSCLES (3)
- depressor anguli oris (marginal mandibular branch)
- depressor labii inferioris (marginal mandibular branch)
- mentalis (marginal mandibular branch)
5
Q
Describe the arterial supply of the face:
A
brachiocephalic trunk -> common carotids -> EXTERNAL carotid (supplies everything outside the skull) :
BRANCHES:
- facial artery -> superior and inferior labial artery
- occipital artery
- posterior auricular artery
- maxillary artery
- superficial temporal artery
6
Q
Describe the venous drainage of the face:
A
- superficial temporal vein and maxillary vein join forming retromandibular vein
- retromandibular vein + posterior auricular vein + facial vein = external jugular vein
7
Q
Describe the nervous supply of facial structures:
A
Facial nerve branches: supply all muscles (Two Zebras Bit My Carrot) - temporal branch - zygomatic branch - buccal branchES - marginal mandibular branch - cervical branch (- also posterior auricular branch)
Trigeminal branches: supply sensation and motor supply to muscles of mastication
- ophthalmic branch = V1
- maxillary branch = V2
- mandibular branch = V3
8
Q
What is the physiology of salivary glands and the composition of saliva?
A
- ~1.5L produced per day
- pH 6-7
- dissolves food so that particles can react with chemoreceptors in the mouth
Contents:
- mucous
- amylase
- lysozyme
9
Q
Why is salivary a-amylase important if pancreatic a-amylase has the same digestive function?
A
Salivary a-amylase dissolves food that is stuck in teeth
10
Q
How does the nervous system control saliva secretion?
A
Controlled by sympathetic and parasympathetic division of the ANS.
Both divisions stimulate salivate SECRETION but the the parasympathetic division stimulates saliva secretion more so.
Increased parasympathetic activity -> increased blood flow to glands -> increased secretion.
11
Q
Describe the physiological process behind saliva secretion including ion movement:
A
- the acini cells in each of the salivary glands secrete a PRIMARY SECRETION that has an ion composition similar to extracellular fluid
- as the secretion flows through the duct system of the glands, active transport occurs and the composition changes
- > Na/K pump actively transports Na out of saliva
- > K+ ions are actively pumped into
- > as a consequence, Cl moves out also, following the Na
- > HCO3- is actively secreted into saliva
- as the rate of salivation increases, the pH increases as more HCO3- is added
- pH increases from 6.2-7.4
12
Q
Describe the anatomy and physiology of the parotid gland:
A
- produces serous saliva that is rich in enzymes
- the facial gland passes through the parotid gland and separates it into a deep and superficial lobe
- 4 bordering structures:
- > zygomatic arch superiorly
- > mandible inferiorly
- > masseter anteriorly
- > ear and sternocleidomastoid muscle posteriorly
- secretions transported by STENSEN DUCT from the anterior surface of the gland through the masseter muscle, pierces buccinator muscle and enters the oral cavity near the 2nd MOLAR
13
Q
Describe the anatomy and physiology of the submandibular salivary gland:
A
- mixed mucous and serous secretions
- 3 boundaries:
- > inferior body of mandible superiorly
- > anterior belly of digastric anteriorly
- > posterior belly of digastric posteriorly
- gland is J shaped and hooks round the mylohyoid muscle
- secretions excreted though 5cm long submandibular duct which opens at base of lingual frenulum
14
Q
Describe the anatomy and physiology of the sublingual salivary gland:
A
- smallest and deepest of the three glands
- contributes 5% of all secretions and is mainly mucous
- found in sublingual fossae on the medial surface of the mandible under the tongue
- the secretory glands (leaving each sublingual gland) unite anteriorly in a horse-shoe shape and open at sublingual caruncle (small lump either side of lingual frenulum)
- each gland also has 8-20 excretory ducts (ducts of rivinus) which open out on top of sublingual folds (mucous membrane anterior to glands in bottom of mouth)
15
Q
Describe the innervation of each of the salivary glands:
A
SUBMANDIBULAR AND SUBLINGUAL:
- facial nerve supplies parasympathetic
- superior cervical ganglion supplies sympathetic
PAROTID:
- glossopharyngeal nerve supplies parasympathetic
- superior cervical ganglion supplies sympathetic
16
Q
How would you test the trigeminal nerve?
A
SENSORY
- cotton wool ball on face, repeat with pin
MOTOR
- place fingers on temples, patient clenches teeth and test temporalis muscle
- place fingers on cheeks and patient clenches teeth feeling masseter muscles
- test jaw jerk
CORNEA (sensory supply of cornea is trigeminal nerve)
- lightly touch cornea with cotton wool wisp while patient looks away and there will be reflex shutting of eyelids
17
Q
How would you test the facial nerve?
A
MOTOR - test muscle control:
- raise eyebrows
- frown
- smile
- puff out cheeks
- tightly close eyes and resist gentle opening
18
Q
What may be the clinical effects if a patient receives a slash to the side of the face?
A
- parotid gland swells
- leaking saliva may form fistula
- blood spurts from 3 places:
- > superior temporal artery
- > facial artery
- > superior labial artery
- if facial nerve branches damaged = tarrsorephy
- > cornea drys out as eyelids cannot close
19
Q
What is tarrsorephy?
A
Surgical procedure where the eyelids are partially sewn together to prevent drying out of cornea
20
Q
What is the violence reduction unit?
A
- part of Police Scotland, which is a national centre of expertise on violence
- tries to reduce violence
- teams up with agencies in fields of health, education and social work and targets violence in school/workplaces/on streets
- trains hairdressers, vets, dentists and firefighters to look for signs of domestic abuse
- has managed to increase the sentence time for carrying a knife
- runs various programmes to help reduce and contain violence
21
Q
Describe the ‘medics against violence’ programme run by the violence reduction unit:
A
- charity set up by 3 surgeons in 2008 to prevent young people being killed or being victims of life-changing injuries
- secondary school education programmes
- NHS professionals volunteer with the charity and educate school pupils
- beneficial as incidents of youth crime are falling
22
Q
What is spinal shock and why does it occur?
A
- long term depression of all spinal reflexes
- spinal cord functions and reflexes become depressed to the point of total silence
- amount of disability and duration depends on level and degree of injury
- there is temporary suppression of all reflex activity below level of injury and spinal neurons gradually regain their exciteability over time from hrs -> weeks -> months
23
Q
What are the phases of spinal shock and its recovery?
A
- Areflexia
- Initial reflex return
- Increased muscle tone
- Hyperreflexia and spasticity
24
Q
What are clinical symptoms of spinal shock?
A
- paralysis
- areflexia
- loss of sensation
- loss of bladder and bowel reflexes
25
What are complications that can arise depending on the level of spinal injury and spinal shock?
- low BP -> hypotension -> loss of sympathetic stimulation of blood vessels
- impaired breathing -> hypoxia
- lack of sympathetic input to the heart -> bradycardia
- hypothermia -> cannot shiver and heat loss from the dilated blood vessels causing low BP
26
In the dorsal medial lemniscus pathway, what are the two areas that receive different signals in the thalamus and where do they receive signals from?
1) ventroposterolateral (VPL) nucleus = receives sensory information from the body
2) ventroposteromedial (VPM) nucleus = receives sensory information from the head
27
What is the rubrospinal tract?
- descending tract
- non-pyramidal
- allows the motor cortex and cerebellum to influence motor activity and control the tone of limb FLEXORS
28
What is the tectospinal tract?
- mediates REFLEX movements in response to VISUAL STIMULI
29
What is the vestibulospinal tract?
- control EXTENSOR muscle tone in antigravity maintenance of posture
30
What is the reticulospinal tract?
- controls muscle tone, voluntary movement, reflexes and is involved in the control of breathing
31
Draw the locations of the main ascending/descending tracts on a cross section of the spinal cord:
See stripy notes HNN p4
32
Although most organs receive both P and S input from the ANS, which organs receive parasympathetic only?
- ciliary muscles which focus the eye
| - iris sphincter muscle
33
Although most organs receive both P and S input from the ANS, which organs receive sympathetic only?
- adrenal medulla
- hair follicles and sweat glands
- spleen
- iris dilator muscle
34
Describe the ANS:
- autonomic nervous system
- regulates organs and maintains homeostasis
- requires CNS input
- consists of pre-ganglionic and post-ganglionic fibres
35
Describe features of the sympathetic division of the ANS:
- T1-L2
- post-ganglionic neurons in the sympathetic trunk
- short pre-ganglionic neurons and long post-ganglionic neurons
- preganglionic neurotransmitter always cholinergic ACh
- postganglionic neurotransmitter adrenergic NA (except sweat glands are cholinergic ACh)
36
Describe features of the parasympathetic division of the ANS:
- CN 3, 7, 9 and 10 and S2-4
- post-ganglionic neuron in wall of viscera they innervate
- long preganglionic and short postganglionic neuron
- preganglionic neurotransmitter AND postganglionic neurotransmitters are cholinergic ACh
37
What is the effect of the sympathetic NS on the following:
a) viscera
b) HR
c) bronchus
d) pupils
e) genitalia
a) increases activity
b) increases
c) dilates
d) dilates
e) ejaculation
38
What is the effect of the parasympathetic NS on the following:
a) viscera
b) HR
c) bronchus
d) pupils
e) genitalia
a) decreases activity
b) decreases
c) constricts
d) constricts
e) erection
39
What is the anatomical difference between and upper and lower motor neuron?
An upper motor neuron runs from the cortex to the anterior (ventral) horn of grey matter in the spinal cord.
A lower motor neuron runs from the ventral horn of grey matter in the spinal cord to innervate skeletal muscle.
40
What is a upper motor neuron lesion?
A lesion of the neural pathway between the brain and the grey matter of the spinal cord (i.e. somewhere on the upper motor neuron) e.g. cerebral infarction,
41
What is a lower motor neuron lesion?
Affects the nerves travelling out of the spinal cord from the anterior horn of grey matter to the periphery e.g. nerve root damage or peripheral nerve damage
42
What signs (UMNL or LMNL) are seen if there is a lesion between C1-5?
UMNL signs seen in all limbs
43
What signs (UMNL or LMNL) are seen if there is a lesion between T3-12?
UMNL signs seen in lower limbs (upper limbs normal)
44
What signs (UMNL or LMNL) are seen if there is a lesion between T12-S2?
LMNL signs seen in lower limbs (upper limbs normal)
45
What is hemiparesis?
Weakness of limbs on one side
46
What is paraplegia?
Paralysis of the lower limbs
47
What is tetraplegia?
Paralysis of all 4 limbs
48
What are signs/symptoms of an UMNL?
- muscle weakness but NOT MUCH WASTING
- increased reflexes
- increased tone and spasticity
- clonus
- positive babinski sign
49
What are signs/symptoms of an LMNL?
- muscle weakness AND WASTING
- decreased reflexes
- reduced tone and spasticity
- fasciculations
- negative babinski sign
50
Describe the effects of a spinal injury at different segments of the spinal cord on RESPIRATION:
C3,4,5 -> contribute to the phrenic nerve, therefore if there is damage in this region then signals from the respiratory centre in the brain cannot innervate respiratory muscles. Damage above this level means there is no continuity of signals between the respiratory centres in the brain and the respiratory nerve terminal innervating the lungs.
C7+8 -> innervate intercostal muscles, diaphragm innervation still intact but paradoxial breathing occurs where the chest wall moves in on inspiration and out on expiration as the intercostals do not contract to expand the chest
51
Describe the effects of a spinal injury at different segments of the spinal cord on BODY MOVEMENT:
C1-4 -> most severe and paralysis of the arms, trunk and legs, limited head and neck movement
C5 -> normal shoulder and bicep control, no wrist or hand control
C6 -> normal wrist control, no hand control
C7+T1 -> arms can straighten, issues with dexterity of hands and fingers
T1 - T8 -> paraplegia, hands not affected, poor trunk control but good balance
L-S regions -> poor control of hip flexors and legs
52
What is the difference between a complete and an incomplete spinal cord injury?
Complete = no motor or sensory function below the level of the SCI
Incomplete = partial motor or sensory loss below the level of the SCI
53
Describe the effects of a spinal injury at different segments of the spinal cord on BLADDER CONTROL:
- micturition reflex depends on integrity of lumbosacral region, damage above this area (i.e. not directly in this area) means reflex should gradually return
- automatic bladder: where the bladder suddenly voids when the stretch receptors in the bladder wall reach threshold
- Indirect control of micturition can occur as when the bladder fills, distension of stretch receptors produces a reflex increase in BP (an exaggerated BP increase) and flushing of face occurs = signalling that the patient must go to the toilet
- Scratching inside thigh = sensory bombardment of the sacral region -> micturition reflex stimulated and bladder empties
- Increased emptying of bladder can be taught by compression if arm movement intact
54
What are the risks associated with incomplete bladder emptying in a patient with a SCI?
increased UTI risk
kidney damage
renin released
hypertension
55
What are other complications of SCI that must be monitored?
- loss of sensation = constant monitoring and prophylaxis as there is increased risk of DVT and pressure sores
- hyperreflexia and increased BP = headaches, dizziness
56
Describe the recovery and management process of a spinal cord injury patient:
- urgent assessment and decompression: surgery, metal plates to stabilise spinal cord, immobilise patient to prevent further injury
- physiotherapy and mobilisation
- supportive care (DVT / prophylaxis)
- bowel and bladder management = intermittent self-catheterisation and balanced food and fluid intake
- pain management (analgesia, opioids)
57
Describe the return of reflexes after a SCI:
SOMATIC FIRST
- flexor reflexes first
- extensor reflexes (knee jerk)
- exaggerated extensor reflexes may occur
(plantar reflex -> cremasteric reflex -> ankle jerk -> knee jerk)
AUTONOMIC REFLEXES SECOND
Initially there would be autonomic dysreflexia and mass reflex responses due to a large sympathetic discharge, but then these would gradually subside
58
What is the babinski reflex?
Negative babinski sign = normal = plantar movement of toes when sole of foot stimulated
Positive babinski response = abnormal = dosriflexion of toes when the sole of the foot is stimulated
59
What is the abdominal reflex?
NORMALLY if abdominal wall scratched, muscles contract to pull umbilicus towards the stimulus
60
What is the cremasteric reflex?
Scratching of inner thigh causes contraction of cremaster muscle and elevates the ipsilateral testicle
61
What teams are involved in the recovery of a spinal cord injury?
- spinal injury unit (try to give prognosis although this is difficult, use the ASIA scale and sensory tests)
- physiotherapist (strength training, rehabilitation, wheelchair use, muscle strengthening, teaching transferable skills)
- psychologist (as depression is common)
- occupational therapist (helps patient reach highest levels of physical and psychological independence so they can return to normal work/home, provide assistive devices to make home life as straight forward as possible)
62
What are the wider effects of a spinal cord injury on a patient and their family?
- loss of job -> pressure -> income support -> employment rehabilitation
- community nurse care
- home modifications
- anxiety and deppression
- parenting roles and main breadwinner roles reversed?
63
What is gastrulation?
The process of the three germ layers developing
- ectoderm
- mesoderm
- endoderm
64
How does the neural plate form?
- CNS appears at the end of week 3 after gastrulation
- thickening of the ectoderm forms called primitive streak
- at end of primitive streak is a 'primitive node'
- a tube extends from the primitive node travelling in the opposite direction called notocord (made of mesoderm)
- notocord controls embryonic folding and has an inductive relationship with the overlying ectoderm, inducing it to thicken and form the neural plate
65
How does the neural tube form from the neural plate?
- the notocord is the inducer and the ectoderm is the responder
- neural plate is made from neuroectoderm
- neuroectoderm lengthens and its lateral edges elevate forming neural folds
- there is a depressed midregion called the neural groove
- neurulation occurs where the neural folds approach each other in the midline and fuse forming the neural tube
- various factors control the bending of the neural plate
- > intrinsic factors in the cytoskeleton
- > extrinsic factors = adhesion points in the notocord and factors expressed from surface ectoderm
- microtubules and microfilaments cause the cells of the neural tube to change shape and become wedged allowing bending
- > dorsolateral hinge points = at the top of each neural fold
- > median hinge point = at the base of the neural groove in the midline
- the neural tube sinks down into the mesoderm and the overlying ectoderm repairs itself
- by day 22, the neural tube is a closed structure
66
What is neural crest tissue and where is it derived from?
- tissue from the top of the neural folds becomes pinched off forming neural crest tissue
- neural crest cells change from epithelial -> mesenchymal
- neural crest cells migrate and give rise to other cell types:
- > Schwann cells
- > melanocytes and hair follicles
- > adrenal medulla
67
What signalling occurs that allows neurulation to occur?
- upregulation of FGF and INHIBITION of BMP4 are both required
- notocord signals activate noggin and chordin expression which STOPS BMP4 production
- BMP4 normally tells tissue to form somites which develop into muscle, so when BMP4 is inactive it causes the mesoderm to stop producing muscle and to make neural tube instead
- various cell adhesion molecules also regulate neurulation as the neural plate switches from producing E-cadherin to producing N-cadherin
- N cadherin allows the two ends of the neural tube to recognise each other and fuse and also prevents fusion of the newly formed neural tube with the overlying ectoderm
68
What two conditions can arise as a result of incorrect neural crest cell migration?
Treacher Collin's Syndrome: TCOF1 gene mutation or retinoic acid exposure early in life
- under-developed zygomatic bones and ears, hearing loss and distinctive facial features
Di George Syndrome: 22q11.2 deletion syndrome
- cleft palate, cardiac abnormalities, NO THYMUS, abnormal facial expressions, poor immune system
69
How does the spinal cord form from the neural tube?
- closure of the neural tube begins in the cervical region and proceeds from there in both directions (up and down) simultaneously
- the open ends of the neural tube are called and anterior and posterior neuropores
- anterior neuropore closes by day 25 and the posterior neuropore closes by day 27
- walls of the closed neural tube are lined by neuroepithelial cells
- neuroepithelial cells give rise to neuroblasts (primitive nerve cells)
- neuroblasts form the MANTLE layer of the spinal cord which becomes grey matter
- more neuroblasts are continually added to the mantle layer
- nerve fibres emerge from neuroblast cells forming the marginal layer (fibres are myelinated) and this later becomes white matter
- the neural tube wall differentiates into dorsal and ventral aspects
- ventral thickening = basal plates = motor area
- dorsal thickening = alar plates = sensory area
- > sulcus limitans is the boundary between the basal and alar plates
- the midline portion of the tube on the dorsal side forms the roofplate, and the midline portion of the tube on the ventral side forms the floorplate
- the roofplate and floorplate have NO NEUROBLAST CELLS and act as pathways for nerve fibres to pass between sides of the spinal cord
70
How do spinal nerves form from the neural tube?
- spinal nerves arise from the cell bodies of nerve cells in the basal plate in week 4
- fibres (motor axons) grow out of the basal plate and are gathered into bundles called ventral nerve roots
- dorsal root ganglia form from neural crest cells that have migrated to the spinal cord area
- dorsal nerve roots containing sensory fibres arise from cell bodies in the dorsal root ganglia
- distal processes from dorsal and ventral nerve roots join forming spinal nerves containing both motor and sensory fibres
71
Describe the formation of the brain vesicles during week 3:
Week 3 = 3 primary brain vesicles present
1) prosencephalon (forebrain = cerebrum + thalamus + hypothalamus)
2) mesencephalon (midbrain = tectum and cerebral peduncle)
3) rhombencephalon (hindbrain = cerebellum, pons and medulla oblongata)
The three regions form at different rates
72
Describe the formation of the brain vesicles during week 5:
Week 5 = 5 primary brain vesicles present
1) prosencephalon becomes:
- > telencephalon (cerebrum)
- > diencephalon (thalamus and hypothalamus)
2) mesencephalon remains unchanged from week 3
3) rhombencephalon becomes:
- > metencephalon (pons and cerebellum)
- > myelencephalon (medulla oblongata)
73
What is anencephaly and how does it occur?
- failure of the anterior neuropore to close
- absence of major portions of brain, skull and scalp
- telencephalon structures fail to form so the cerebral hemispheres are not properly formed
- individuals usually do not survive more than a few days/hours
- can be detected prenatally by ultrasound scanning
74
What is spina bifida and how does it occur?
- failure of the posterior neuropore to close
- various types:
1) spina bifida occulta: the outer bony part of the vertebrae is not closed properly but there is no protrusion of the spinal cord, there may be hair over the defect
2) myelomeningocoele: meninges and spinal nerves protrude out
3) spina bifida cystica/meningocoele: vertebrae form normally but the meninges protrude
75
How do they meninges develop and at what time?
They develop from mesenchymal and neural crest cells
| - at days 20-35 the cells migrate around the neural tube forming the meninges
76
What is hydrocephalus and how can it be treated?
- associated with spina bifida
- cerebral abnormalities of XS fluid in the brain and there is raised intracranial pressure
- XS CSF drained using a shunt, directly into the abdomen in a surgical procedure that has great results
77
How does the eye develop?
- each eye forms as an outgrowth of the diencephalon called an optic vesicle
- optic vesicles have an inductive relationship with the surface ectoderm
- the eyes appear as shallow grooves at day 22 and continue developing until week 10
- next to each optic vesicle, a thickened area of cells forms called lens placode
- lens placode becomes a double layered optic cup
1) outer pigmented layer
2) inner neural layer that contains rods, cones and neurons
- both layers at the rim of the optic cup form the iris and ciliary body
- the ciliary bod produces aqueous humour
- LENS is an initially hollow structure derived from surface ectoderm, the cells elongate but contain no nuclei or organelles and are transparent so that we can see
- the optic stalk becomes the optic nerve and the two layers (pigmented outer and neuronal inner) fuse and the cavity between the two disappears)
- neuroglia cells are in the inner layer of the optic cup and support the growing nerve fibres
- mesenchyme around the optic cup condenses forming eyeball layers
- space between the cornea and lens becomes anterior chamber of eye
- gap between the lens and retina fills with gelatinous fibrous tissue and forms the posterior chamber
78
Describe the blood supply to the developing eye:
- blood supply to the developing eye = hyaloid artery (a branch of the ophthalmic artery)
- the hyaloid artery travels through a groove on the ventral surface of the optic cup called the choroidal fissure
- eventually the hyaloid artery (and vein) become the central artery (and vein) of the retina = JUST A NAME CHANGE
79
How do the eyelids form?
- are folds of ectoderm with mesenchyme inbetween that grow over the cornea
- months 5-7 in utero, the eyelids form, fuse and separate again
- when the eyelids fuse they enclose a conjunctival sac anterior to the cornea and the inner layer of ectoderm becomes conjunctiva
- lacrimal glands form as ectodermal buds from upper conjunctival sac into the surrounding mesoderm
80
What are the major genes involved in eye development?
- PAX6 is the key regulatory molecule expressed before neurulation begins, by the anterior neural plate
- SHH (sonic hedgehog) is responsible for eye field separation by upregulating the production of PAX2 in the optic stalks
- PAX2 therefore restricts PAX6 signalling to having an effect on the optic cup and lens only
81
What is microphtalmia?
Eyeball is too small
| Causes: PAX6 disorder, intrauterine infection, foetal alcohol syndrome
82
What is anophtalmia?
Eyeball is absent as optic vesicle fails to develop
83
What is cyclopsis?
Having only one eyeball
- failure of prosencephalon to divide orbits of the eye
- mutations in SHH
84
What is colomba iridis?
Cleft in the iris of the eye, a keyhold defect as the choroid fissure fails to close
85
What is congenital detachment of the retina?
Failure of fusion of the inner and outer layers of the retina
86
What is congenital cataracts?
- the lens is opaque due to abnormal development of lens fibres
- can be genetic cause or due to rubella infection during weeks 4-7 gestation
87
Why is it important that mothers are vaccinated against rubella?
It can cause other issues as well as cataracts such as hearing loss
88
What is the function of the blood brain barrier and how can it be compromised?
- function is to protect the brain from foreign substances like peripheral neurotransmitters and maintain a constant environment
- compromised by:
- > hypertension
- > infection
- > trauma
89
Give an example of an area of the brain that lies out-with the blood brain barrier and what is controls:
The area postrema
| It control the vomit reflex
90
What are the two main routes of drug administration?
- > enteral = involves the digestive system e.g. lipophilic drugs
- > parenteral (any non-oral administration) e.g. IV, topical, opioid analgesics
91
What do analgesic agents do and give named example?
- pain relief and control e.g. NSAIDS, opioids
92
What do antiolytics and sedatives do and give named example?
- sleepy and reduce anxiety e.g. barbitates (also called minor tranquilisors and hypnotics)
93
What do antipsychotics do?
- relieve symptoms of schizophrenic illness
94
What do antidepressants do and give named example?
- alleviate symptoms of depression and affect disorders of mood rather than thought and cognitive function e.g. ketamine, SSRI (fluxotine), MAOI (monoamine oxidase inhibitors e.g. phenelzine)
95
What do anaesthesics do and give named example?
- produce anaesthesia e.g. dexoflurane, isoflurane, propofol
96
What do psychomotor stimulants (psychostimulants) do and give named example?
- cause wakefulness and euphoria e.f. cocaine, caffeine, amphetamine
97
What do psychotomimetics do and give named example?
- disturbs perception (distinguishable from sedatives and stimulants) e.g. LSD, THC
98
What do cognition enhancers (no-otrophic) do and give named example?
- improve memory and cognitive performance e.g. donepezil, tacrine
99
What is LSD?
Psychoactive drug that binds to serotonin receptors causing hallucinations
100
What is THC?
Tetrahydrocannabinol (a constituent of cannabis) which is a psychotomimetic drug
101
Name some neurological disorders:
- dementia
- epilepsy
- parkinson's
- stroke
102
Name some psychiatric disorders:
- anxiety
- depression
- sleep disorders
- schizophrenia
103
What illnesses are classed as miscellaneous?
- motion sickness
| - fever
104
What is the basic pathophysiology of Parkinson's disease?
- death of cells in the niagrostriatal pathway
| - characterised by tremor, rigidity and hypokinesia (decreased bodily movement)
105
What is the basic pathophysiology of Schizophrenia?
- complex with cerebral cortex abnormalities
- alterations in neurotransmitter systems
- there is a theory around dopamine
- > drugs that DEPLETE DOPAMINE have anti-psychotic symptoms
- > drugs that INCREASE/RELEASE DOPAMINE have psychotic symptoms
106
What drugs can be used to treat schizophrenia and name examples?
- dopamine receptor blockers (antipsychotics) e.g. haloperidol, dozapine
107
When are dopamine receptor agonists
a) desirable?
b) undesirable?
a) to treat parkinson's disease
| b) to treat Schizophrenia, nausea
108
When are dopamine receptor antagonists
a) desirable?
b) undesirable?
a) when used as antipsychotics
| b) in parkinson's treatment
109
What two dopamine pathways must you achieve a balance between in the brain?
The mesolimbic pathway and the nigrastriatal pathway
110
What are the cutaneous branches of the trigeminal nerve?
V1 = ophthlamic
V2 = maxillary
V3 - mandibular
111
Embryologically, where do the muscles of mastication arise from?
First pharyngeal arch
112
Embryologically, where do the muscles of facial expression arise from?
Second pharygeal arch
113
What is a spinal reflex?
Where afferent signals enter the spinal cord, efferent signals leave the spinal cord and head to muscle and the brain is not involved in controlling the reflexes (although can be).
114
Describe the components of a reflex pathway and how a reflex is initiated:
- monosynaptic circuit has a 2 neuron reflex arc with a single synapse
- afferent neuron is proprioceptive A-alpha fibre
- efferent neuron is a motor neuron that innervates the same muscle that the proprioceptor fibres arose from
- striking a tendon with a hammer is the stimulus and stretches the quadriceps muscle
- this activates stretch receptors on the muscle and action potentials are released
- at the synapse, signals are transmitted from 1a afferent fibres to ventral motor neurons which travel out again and innervate the same muscle in which the stretch receptors were activated
- an AP is then produced in the skeletal muscle fibres and this triggers excitation-contraction coupling
- there is a brief shortening of the muscle fibres and a 'twitch contraction' occurs causing pulling on the tendon and a jerking motion of the lower limb
115
How do you elicit a tendon reflex?
- useful as a neurological test
| - hit the tendon with a tendon hammer to activate the monosynaptic reflex circuit
116
What does it mean that reflexes are 'stereotyped'?
The response is the same, and at a similar level of muscle contraction and movement each time
117
How can the brain influence reflexes?
- the excitability of a reflex is modulated by descending pathways from the brain
- the brain can be very 'SENSITIVE' so that a small muscle stretch causes a big contraction to prevent the muscle lengthening = a stiff joint
- the brain can be 'UN-SENSITIVE' so that a large stretch of the muscle is needed before a reflex is stimulated = the muscle will be relaxed and flaccid
- the body uses this principle all the time to maintain posture
118
What are the segmental roots of the jaw jerk reflex?
5th cranial nerve
119
What are the segmental roots of the biceps reflex?
C5 and 6
120
What are the segmental roots of the triceps reflex?
C6, 7 and 8
121
What are the segmental roots of the brachioradialis reflex?
C5 and 6
122
What are the segmental roots of the knee jerk reflex?
L3 and 4
123
What are the segmental roots of the ankle jerk reflex?
S1 and 2
124
How can a patient reinforce a reflex and what is the physiological basis of this?
- Jendrassik's manouevre by clenching hands and trying to pull apart can reinforce lower limb movements
- clenching your teeth just before a reflex is carried out can reinforce upper limb reflexes
- reinforcement increases the excitability of motor neurons in the pool that you are testing
- hitting a tendon with a hammer triggers a signal to be sent along the 1a afferent fibres to the monosynaptic junction, but the signal may not be strong enough to reach the threshold needed for an action potential to be fired
- by carrying out the reinforcement techniques, this will increase the total number of motor neurons that respond and the threshold needed for an AP to be fired will be reached and then the reflex response should be observed
- the manoeuvre causes the background resting membrane potential of the muscle to already be a bit more depolarised and this means that action potential threshold can be reached more easily
- effectively, the reinforcement increases the total number of neurons that are contributing to the reflex response
125
When is the plantar response used and what is the babinski sign? (+ and -)?
- used to test disorders of the corticospinal tract pathways
- applying pressure up the lateral edge of the foot ad medially along under the toes causes downwards (plantar flexion) curling of the toes
- positive babinski sign = dorsiflexion of the toes = abnormal
- negative babinski sign = plantarflexion of the toes = normal
126
What is unusual about the plantar response in young children?
- in newborns and neonates, you see a positive babinski sign in the plantar reflex up to the age of one year
- this is normal for them
- initially there are two reflex circuits but after the age of one year the corticospinal tract matures and becomes myelinated and then fanning up of the toes is suppressed
127
What is a mononeuropathy (a point neuropathy)?
affects a single peripheral nerve, is a disorder of the PNS
128
What is the ASIA scale used for and what are it's gradings A-E?
- a standard neurological classification for spinal cord injuries
A - complete -> no motor or sensory function preserved
B - incomplete -> sensory function preserved but motor not
C - motor function preserved and more than half of the key muscles have a MRC grading of 3 or LESS
D - motor function preserved and more than half of the key muscles have a MRC grading of 3 or MORE
E - normal -> motor and sensory function are normal
129
What are proprioceptors?
Sensory fibres that are emitted from muscles to allow 3D spacial awareness
130
What is nociceptive pain?
- normal pain, caused when there is damage or threat to damage normal tissue
- is useful for protecting the body
- is characterised by
- > high threshold
- > limited duration
- fibres that carry this pain are
- > alpha-delta
- > C fibres
131
What is chronic (neuropathic pain)?
- unuseful pain that interferes with daily living and serves no biologically useful role
- brought on by stimuli that normally evoke innocuous sensation (not dangerous or harmful)
- > alpha beta, alpha delta and C fibres transmit this pain
132
Where are cell bodies of sensory neurons found?
dorsal root ganglion
133
Where are cell bodies of motor neurons found?
ventral horn of grey matter
134
Describe the 5 different types of cutaneous mechanoreceptor endings:
1) meissner's corpuscles
2) merkel discs
3) hair follicle afferents
4) pacinian corpuscles
5) ruffini endings
135
Describe the white reaction and process of the triple response:
1) red reaction line = point of mechanical trauma of the skin
2) odemitis wheal = the white region around the skin that raises
3) flare = red spotted region that surrounds the wheal
- applying mechanical trauma to the skin causes tissue damage and release of K ions and prostaglandins
- platelets release serotonin
- the chemicals activate the free nerve endings of nerve fibres and peptides are released from some neighbouring nerve fibres (substance P and calcitonin gene related peptide CGRP)
- these activate mast cells they release of histamine
- substance P causes extravasation -> oedema -> swelling compresses capillaries making skin paler
- CGRP causes dilation of blood vessels -> seen in flare region
136
As different grey matter regions are dedicated to different sensory modalities, what region do A-delta and C fibres terminate in?
Laminae I and II
137
As different grey matter regions are dedicated to different sensory modalities, what region do A-beta fibres terminate in?
Laminae III - V
138
Describe the self-modification system for pain in the spinal cord:
- collateral branches come off nerves in the ascending tracts and activate descending circuits that project signals back down to interfere with circuitry in the dorsal horn (the collateral branches activate supraspinal loops)
- there is then interference of signals coming in on primary and secondary neurons of the ascending tracts and this 'dampens down' signals so that someone's perception of pain is reduced
139
What is TENS and what is it useful for?
- transcutaneous electrical nerve stimulation
- can modulate pain in conditions like: RA, sciatica, sports injuries, MS
- the treatment is topographically specific i.e. electrodes are placed to activate larger diameter afferents that overlap the area of injury and pain
- TENS is not effective in all patients
140
What are the two theories as to how TENS is thought to work:
1) nociceptors have small diameter axons, TENS activates large diameter axons of other sensory receptors and creates a 'jamming' effect in the dorsal horn of the spinal cord as there is transmission interference
2) TENS causes release of endorphins in the brainstem and activates descending pathways so that transmission in ascending pain pathways is suppressed
141
What are endogenous opioids and the three families in the body:
- opioids that the body produces as its own pain relief
- three families:
- > enkephalins = reduce the amplitude of EPSP so that transmission in the dorsal horn can be suppressed
- > pro-opiomelanocortin (POMC)
- > dynorphins
142
What are the three opioid receptors in the body?
- Mu
- Delta
- Kappa
143
What is a 'sensory unit'?
A single sensory nerve and all the receptors with which it is connected
144
Describe the physiological basis of two-point discrimination:
- all over the skin there are receptive fields = the area in which a sensory nerve picks up stimulation
- stimuli must fall between two separate receptive fields for two point discrimination to be possible
- in the hand there are a high density of small receptive fields = two point discrimination can be felt at much smaller distances (few cm)
- on the shoulder and back there are a low density of larger receptive fields = two point discrimination is less accurate and can be felt at much larger distances (42cm on back)
145
What do meissner's corpuscles detect?
Light touch
146
What do hair follicle afferents detect?
Gentle brushing
147
What do merkel discs detect?
Pressure and mechanical deflection (found on hairy skin)
148
What do pacinian corpuscles detect?
Pressure and vibration
149
What do ruffini endings detect?
Slippage or stretch of the skin
