Neurosciences Flashcards
1
Q
What is rostral acording to brain?
A
The front caudal is the back
2
Q
What is rostral in terms of te spinal cord?
A
Towards the head
3
Q
What are the main parts of the brain?q
A
Cerebrum, Cerebellum and brain stem
4
Q
What are the outer layers of the brain called?
A
The meninges
5
Q
What are the parts of the brainstem?
A
Medulla oblongata, Pons, Midbrain, Diencephalon
6
Q
What are dermatomes?
A
The area of skin supplied by nerves from a specific spinal level
7
Q
What are the lobes of the brain?
A
Occipital, parietal, temporal and frontal
8
Q
What are some of the names of important fissures or giri?
A
Sylvian fissure(lateral) central fissure, cingulate girus, calcarine sulcus, parahippocampal girus
9
Q
Where is the primary mortor cortex?
A
The precentral girus in fron of central sulcus
10
Q
What is the premotor cortex?
A
the seccondary motor area
11
Q
Where is the primary somatosensory cortex?
A
The post central girus
12
Q
Where is the pituitary?
A
Below the optic chiasma, in from of the pons
13
Q
What is mindbody dualism?
A
The belief that the mind and the body are not linked and can be separated
14
Q
What are the criticisms of dualism?
A
What is non physical substance that makes the mind. how can an immaterial thing create physical effects? is it linked to supernatureal
15
Q
What is reductive physicalism?
A
Everything is explicable by the physcical giving a view of depression as biological
16
Q
What is interactionism?
A
Entities can have an effect on one another, mental distress casues symptoms and vice versa
17
Q
What are the consequences of dualistic thinking?
A
Makes us thing things are explicable by biomedical model but we have the mind that has an effect but we can’t study it medically unexplained symptoms are hard.
18
Q
What is the reptillia brain?
A
Part in development about homeostasis arousal survival and reflexed that most animals have
19
Q
What is the mamalian or limbic brain?
A
Emotions nurturing habits and memory are in this part from development
20
Q
Which part of the brain gives us the most distinct features?
A
The frontal lobe
21
Q
Where does dopamine affect?
A
The frontal cortex givind rewards euporia motor function and compulsion
22
Q
Where does serotonine afect?
A
all but occipital , mood memory and processsnin sleep cognition
23
Q
How can you test the frontal lobe ?
A
Proverb interpretation, similarities test, cognitive estimates, wisconsin card-sorting test
24
Q
What are the symptoms of schizophrenia?
A
Delusions, thought disorder when its hard to make sense of what someone says. hallucinations they can get worse and become withdraw and appear unemotional lose interest stop looking after themeselves and find it hard to do normal tasks
25
What the biological correlates for schizophrenia?
brain volume functional imaging neurotransmitter abnormalites and genetic factors.Dopamin blockers seem to work and this can be negated by other drugs such as for parkinsons
26
What is the non biological correlates for schizophrenia?
social migration to cities could cause it psychosocial treatments have an effect, associated with repeat childhood trauma. associated with stress
27
What are problems with classification and diagnosis of mental disorders?
have to set arbirary limits on thinds like depression, leads to stigma and prejudice, economy of thought may lead to oversimplification
28
What does evolution show about systems level architechture of the brain?
The brain always had the same parts just developed into different sizes but maintained function over time
29
What is the mechanism that the brain uses for defence at a low level?
It has receptors that go to the spinal cord and does motor autonomic endocrine responses.
30
What does the brain use for the avoidance of loom dangers?
Visual processing or auditory and goes to sensorimotor mid-brain to the effectors at a subconscious level
31
What is the highest level of avoidance pathway?
Learned threat which includes the cortex and limbic system
32
How can you look at the hierarchy of of bain function?
Lowest is spinal cord reflexes, hindbraind does sudden distal stimuli for the startling, midbrain and hypothalamus does species specific threat like fight or flight, then it is the thalamus sensory cortex and hippocampus using amygdala for complex avoidance
33
what is in the CNS?
Brain and spinal cord
34
What is the peripheral nervous system?
all the nerves other than the spinal cord and brain
35
What are the divisions of the peripheral nervous system?
Somatic under conscious control and autonomic which is subconscious nervous system
36
What is the spinal cord separated into?
cervical, throacic lumbar and sacral
37
What do cervical nerves usually do?
Head and neck diaphragm and the arms and hands
38
What do thoracic nerves usually do?
chest muscles breathing abdominal muscles
39
What do the lumbar nerves usually do?
Legs and feet
40
What do the sacral nerves do?
Bowel and bladder control as well as sexual function
41
What are the dorsal roots of the spinal cord?
The dorsal is the sensory receptor signals entering afferent signals
42
What is the ventral root of the spinal cord responsible for?
The motor function signals coming from the brain efferent signals
43
What is in the ganglion where the dorsal and ventral roots join?
The dorsal root ganglion for the sensory neurons.
44
What are the three biggest divisions of the brain?
Forebrain, Midbrain and Hindbrain
45
How can the forebrain be split up?
into the telencephalon and the diencepalon
46
What is in the telencephalon?
cerebral cortex basal ganglia and limbic system
47
What is the diencephalon made from?
The thalamus and hypothalamus
48
What is the midbrain?
The mesencephalon
49
What is the mesencephalon made of?
The tegmentum and tectum
50
What is the hindbrain made from?
the metencephalon and the myelencephalon
51
What is the metencephalon?
Pons and cerebellum
52
What is the myelencephalon?
The medulla
53
What is the function of the medulla?
Contains tracts with signals to the rest of the brain, low sensorimotor such as balance,
Responsible for autonomic functions such as vomiting and sneezing.
Contains the cardiac and respiratory and vasomotor centres.
Controls ventilation via signs from central chemoreceptors.
Controls vasomotor from central baroreceptors
54
What is the function of the pons?
The bridge or relay between the cortex and the mid brain to the cerebellum, it contains lots of neuronal fibers and has the pontine reticular formation which is used in pattern generation
55
What does the cerebellum do?
It is mainly involved with motor functions. It is unvolved with fine regulation of movement and correcting motor errors. could have a role in cognitive emotions.
56
What does the tectum made of?
The superior and inferior colliculus
57
What does the superior colliculus?
Sensitive to sensory change and orienting defensive movements. gets topical inputs of signt
58
What does the inferior colliculus do?
it is involved in subconscious auditory events.
59
What is the tegmentum made of?
The periaqueductal grey, red nucleus and substantia nigra
60
What does the periaqueductal grey do?
Role in defensive behaviour, role in pain ascending and descending signals, role in reproduction
61
What does the red nucleus do?
Relay station involved with the motor signals from the cortext and cerebellum and a role in pre-cortical motor control
62
What does the substantia nigra do?
It is involved in dopanin production involved in parkinsons disease
63
What is the thalamus doing?
Has specific nuclei and relays signals to the cortex and limbic systems for all sensations other than smell.
It has non-specific nuclei and has a role in regulating the state of sleep and wakefulness and arousal it is a relay from the basal ganglia and the cerebellum back to the cortex
64
What does the hypothalamus do?
Regulates the pituitary gland which regulates the hormones, tole in hormonal control of motivational behaviour hunger thirst sex pleasure pain temperature
65
What can the forbrain be split into?
The forebrain or cerebral cortex can be subcortical or cortical
66
What are the sructures in the subcortical area of the forebrain?
Basal ganglia and the limbic system
67
What are the components and what is the function of the basal ganglia?
Dorsal Striatum: Caudate nucleus and putamen
Ventral Straitum: Nucleus accumbens and olfactory tubercle
global pallidus
ventral pallidum
substantia nigra
subthalamic nucleus
Connects inputs of the brain by recurrent loops.
facilitates purposeful behaviour
inhibits unwanted movement
controls posture and movement
selects which competing systems are active
68
What are the constituets of the limbic system?
The Amygdala, hippocampus, fornix, cingulate gyrus and septum and mamillary bodies
69
What is the function of the amygdala?
almond associated with sensory stimuli with emotional impact
70
What is the function of the mammillary body?
They are important for the formation of recollective memory
71
What is the function of the hippocampus?
Involved with memory long term and spatial memory
72
What is the function of cigulate gyrus?
linking behavioural outcomes to motivation and autonomic control
73
What is the function of the septum?
Involved in defense and aggression
74
What is the function of the fornix?
It is involved with carying signals from te hippocampus to the mamillary bodies and septal nucleus
75
How many layers of cortical lobes are there?
6 layers of cell bodies made of white and grey matter
76
What are some important areas in the cortical lobes?
The primary motor cortex which is the origin of descending motor pathwaysalso premotor and supplementary motor areas wich have higher level motor plans and initiation of voluntary movement
Brocas area - production of speach and language
wernickes area - understanding verbal and written information
77
What is the frontl lobe responsible for?
Executive planning and judgmental roles it has the short term memory and controls behaviour based on setting.
78
What is the primary somatosensory cortex?
its in parietal lobe and recieves signals from the body. it maintains representations of the bodys position in spaces and predicting movement of moving objects
79
What is the temporal lobe involved with?
Primary auditary complex and it linkes with the limbic system and is involved with recognition of faces.
80
What is the occipital lobe doing?
The visual inputs with the primary visual cortex.
81
What is the dorsal stream?
The vision for movement where things are in relation to you.
82
What is the ventral stream?
It is used for identification of things meaning why it is important to us
83
What are the levels of description in neruological understanding?
Psychological, systems, mictocircuit, neruonal, intracellular and molecular
84
Why are X-rays bad for imaging the brain/spinal cord?
Not very good for the tissue but for the bone and for foreign objects.
85
How can x-rays be made more useful?
Using contrast x-ray. cerebral angiography can show you how well the blood vessels are working and if there is a blockage although they cant tell you about the brain function itself.
86
How is MRI used in neroscience?
very good for looking at the structure and composition of the brain for tumours and swellings. it is non-ionising and very high detail can be obtained from it.
87
What is functional magnetic resonance imaging?
It is tuning MRI to look at oxygenated and deoxygenated iron in the blood. this can tell you about what areas of the brain are using more oxygen and may be more active.
88
How does fMRI work but what is one issue with it?
Increased neuronal activity uses more oxygen which attracts more blood flow there so its slightly counterintuitive can't differentiate between inhibitory or exitatory
89
What is the use of PET scanning?
Positron emission tomography is when a chenical that binds to or is uses is radio tagged and given to a patient then the emissions from this isotope are tracked as part of the scan to give a 3 d image. it can be useful for showing activity and/ tumours
90
What is a new type of scanner that could be good?
MRI PET/fMRI scanners that can be used
91
What are EEG scans?
Electroencephalography detects the activity of neurons but it shows the summation of many neurons from the surface.
not very spatial signals
can use repetitions of tasks to see what's happening to get event-related potential
92
What is MEG?
Magnetoencephalography it pics up on magnetic activity from the flow of current through axons. it is a very big machine it is more indicative of actual activity due to less noise
93
What is TMS or TDCS?
Transcranial magnetic stimulation or transcrania direct current stimulation which passes current or magnetic filed through and an area of the brain to innactivate part of the brain to investigate function
94
What is galvanic skin conductors?
It is used for sweat measuring to measure the autonomic nervous system
95
What is important when considering which method to use?
Invasiveness and spatial and temporal investigations
96
What are the 3 Rs of animal models?
Replacement (can other methods be used?)
Refinement can it be done in a better way that maximises the benefit,
Reduction can it be done with fewer animals
97
Which animals are most used in research?
Mice, fish rats birds
98
What are some invasive measures usually used only in research?
Deep brain probes, intracellular investigaion of neurones. stimulate one region and record activity in another area. using tracer in neurones with anteriograde and retrograde tracers
99
What are the applications of invasive measures?
They can be mixed to look at the effect of pharmacological agents.
100
What are the uses of genetic engineering?
Knock out or excessive gene expression.
101
What is optogenetics?
Looking at stimulating with light with genetic implantation of receptors
102
What week in development do the eyes form?
3 weeks
103
Which week does the brain start to form properly?
6 weeks
104
When are the basic structures of the brain developed?
3 months
105
When are the CNS neurones myelinated?
at 5 months
106
What are some of the critical periods in deveopment in utero?
```
rubella can affect them
6th week eye malformations
9th week deafness
5th to 10th cardiac
2nd trimester CNS
```
107
What is fetal alcohol syndrome?
When alcohol from mothers blood passes to the baby, causes abnormalities like loss of cells loss of fibres motor and intellectual impairment, flat midface thin upper lip
108
What is the effect of opiates on babies?
withdrawl
109
What is the problem with cocaine usage?
withdrawl decreased cognition, hypoxia, or abortion
110
What is a stress response in the foetus?
not awareness but can cause uptake of lung fluid
111
What are primitive reflexes?
Ones present at birth that are usually repressed in adulthood and therefore a pathaloical sign in adults
112
What is the rooting reflex?
Turning the head in the direction of stroking of cheek
113
What is the suckling reflex?
Babies will such an opject that touches their lips
114
What is the moro(startle)reflex?
Back archs lega and arms flung out and then brougt back in when dropped
115
What is the grasping (palmar) reflex?
Babies grasp objects put in their hand
116
What is the stepping reflex?
The mimic walking when upright
117
What is the babinski reflex?
fan toes when sole of the foot is stroked
118
What is the tonic- neck reflex?
Turn head to one side and extend arm and leg
119
When is a baby able to track objects?
from birth
120
When can a baby converge the gaze?
at 7 or 8 weeks
121
Do neonates have perpheral vision?
no
122
When does taste develope?
At birth prevers sweet
123
When does smell develop?
at birth
124
When does dexterity develop?
at age 3
125
Where does development happen and how?
cranial to caudal, proximal to distal, simple to complex
126
What is the left hemisphere involved with?
Verbal speaking reading thinking and reasoning
127
What is the right hemisphere involved with?
nonverbal spatial patterns drawing recognition music emotionall ecpresssion
128
What are the types of malformation in development?
Miss development, things not developing, DNA is wrong the DNA is not executed orrectly
129
What can cause malformations?
toxins, Infections, Prematurity
130
What does cytomegalovirus do to a foetus?
Intracranial calcification as well as Aicardi-Goutières syndrome
131
What is lissencephaly?
Smooth brain neuronal migration disorder
132
How much alcohol can affect a foetus?
Binging very bad, 2 units a day can affect them
133
What can be looked for in the brain in an ultrasound scan?
Ventricular haemorrahge
134
What are some red flags in development of children?
Syndromic childen, history of brain injury, any loss of skill at any age, visually not fixing or following objects, hearing loss, low or high muscle tone, squint after 3 or 4 months 6th nerve. can't hold object in hand, handed ness before 3 years old, cant point at oject to share intrest by 2 years, no speach by 18 months, persistent to walking, girls not walking by 2 years, gboys not walking by 18 months, can't sit unsupported by 12 months
135
What do skeletal muscle fibres look like?
Myofibres in fascicles conected with epimysium perimysyuum and endomysium, they are in bundlles with nuclei around the edges.
136
What surrounds muscles?
Basement membrane syrrounding myofibriles collage and glycoproteins, there.
137
What is a motor unit?
The group of muscle fibres that are all innervated by the same nerve
138
What is the transmitter for the muscle?
Acetycholine
139
What are the proprioception muscles receptors?
Muscle spindles which are intrafusal fibres and Golgi tendons which are tension receptors
140
What is a primary muscle disesase?
A disorder in the muscle its self
141
What are the needs for a muscle biopsy?
cant put in formalin and is frozen and needs the right direction of slice also can look at it ultrastructurally
142
How can you look at fibre types?
Using histochemistry with enzymes to generate colour, oxidative enzymes
143
What are the types of muscle fibres?
slow twitch type 1 red which are oxidative and fatigue resistant
fast twitch which are very powerful but fatigue type 2:
2 A Glycolytic and oxidative intermediate 2B glycolytic which are white and fatigue easily.
144
How do motor units structure?
they can overlap and intermingle, fibre type depends on innervation, the size is dependant on the amount of controlled
145
What happens in deinervatio of motor neurones?
Collateral sprouting of adjacent motor units which allows re innervation with larger motor units get conversion of fibre types
146
What is the Z disk?
The lines of protein with alpha actin titin nebulin and desmin that define the sarcomere
147
What is a sarcomere?
Basic unit of contraction repeating arrangement forms a fibre
148
What makes the A bands?
The myosin strands.
149
Do the I bands or A bands shorten?
I bands
150
What makes up thick fillaments?
Myosin
151
What does desmin do?
Links myofibrils to eachother and the sarcolemma
152
What is the structure of actin?
There are actin globular proteins, with tropomyosing strands and troponin to block the binding sites
153
What are the m lines?
The fibres that are in the middle of the a band
154
What causes shortening of the sarcomere?
The sliding of the fibres over eachother not the shortening of fibres, activated by CA2+
155
What provides energy for the contraction?
ATP
156
What can store ATP?
Creatine pospate and is replenished by creating kinase which is released when a muscle fibre is damaged.
157
What are mitochondrial cytopathies?
Problems with mitochondria, have maternal inherided DNA which is circular, mutations can occur in nucleus or in mitochondria, can have clinical presentations of CNS problems,
158
How can mitochondrial cytopathies be diagnosed histologcally?
take a muscle biopsy, ragged red fires transport cain deficites in cytochrome oxidates negative fibres
159
What is dystophin?
a protein that binds to actin and the sarcoglycans in the sarcolemma
160
What other proteins are involved with dystrophin?
Merosin dystroglycans, sarcoglycans, and actin
161
What can happen in problems with dystrophin problems?
When the muscle contracts the muscle loses weakness and can cause the destruction of muscle fibres they are genetic.
162
What is duchennes muscular dystrophy?
Deletion from gene that causes open reading phrame and short protein or no protein is produced.
163
what happens in neuromuscular transmission of nerve impulese?
ACh binds to receptor, cation entry results in depolarisation of the end plate the action potential crosses the membrane and into t tubule system where calcium is released from the sarcoplasmic reticulum.
164
What ends the contraction?
When ACh is hydrolyses by acetyl cholinesterase in the neruomuscular junction
165
What is myasthenia gravis?
Variabe weaknes progressive with sustained effort eyesign of ptosis. it is autoimune and anti Acetylcholine in a reduction of receptors.
166
What are the adaptations of the endoneurium and perineurium?
They have tight junctions to reduce transport of unwanted sustances
167
How many nerves can one swann cells look after?
For myelenated nervs it is only one but otherwise can be several
168
What are oligodendrocytes and how do they differe to Schwann cells?
They can myelenate many and they are only found in the CNS
169
What is a peripheral neuropatheis?
damage to motor and sensory neurons can be axonopathies or to demyelination
170
What is axonal degeneration/regeneration?
When an axon is damage distally the nerve dies but can regrow from there and Schwann cells can produce sprouts they won't be as fast though
171
When does the neural tube close?
At the 4th week
172
Which important brain cells are derived from the ectoderm?
Melanocytes, Shwann cells, neurones
173
Which importan cells develop from the mesoderm?
Osteoblasts and osteoclasts, adipocytes and chondrocytes
174
What is it called when the neural tube fails to close at the head end?
anencephaly
175
What is it called when the neural tube fails to close in the spinal region?
Spina Bifida
176
What is a meningocele?
Protrusion of the meningesthrough where the vertebral spine should be
177
When does the anomaly scan take place?
Anomaly scan takes place at 20 weeks looking for development defects. ultrasound
178
What are the emryological areas of the brain called?
Prosencephalon, Mesencephalon and Rhombencephalon also the spinal cord
179
What does the Prosencephalon give rise to?
The frontal lobes and cortex, the telencephalon and diencephalon
180
What does the mesencephalon give rise to?
the thalamus and nuclei the mesencepalon
181
What does the rhombencephalon give rise to?
the cerebellum and brainstem
182
What can affect brain development in foetus?
Alcohol and valproate
183
What is the most comon developmental disorders?
Intellectual disability, from the malformation of the layers of the brain cortex
184
How much CSF is there?
About 120 mls
185
What are the causes of hydrocephalus?
Brain tumours menigitis, obstruction of the flow of CSF. There is also over production of non-obstructive.
186
What muscle is in the lower eye lid?
There isn't one
187
What is the muscle that is there for theupper eye lid?
Orbicularis oculi to close the eyelid this is innervatied by 7th cranial nerve. there is levator palpebrae superiouis that elevates the eyelid innervated by the 3rd cranial nerve the occulomotor
188
what is the name of the rim of tissue in the eyelid?
The tarsal plate which contains meibimian/ tarsal glands
189
What innervation is there in the eyelid?
Motor and also sympathetic for horners gland smooth muscle
190
Where is the tarsal gland?
runs vertically upwards from the eye lid rim in both upper and lower lid
191
What is the conjunctiva?
It is a mucous membrane which covers the eyelid and frontal areas of the eyeball/globe. It merges with the cornea at the limbus
192
What is the conjunctivia like?
It is loosly attached to the globe and highly vasuclar alhtough the vessels are usually constricted
193
What are the layers of the tear film?
The anterior lipid layer from meibomian glands, aqueous layer from the lacrimal and acessory glands, the mucin layer which is crom conjunctival goblet cells
194
What is in the aqueous layer?
antibodies enzymes and vitamin C
195
What is the importance of the tear film?
protects the eye and supplies the cornea with oxygen and nutrients and gives a smooth clear anterior refracting surface.
196
What is the purpose of the mucin layer of the eye?
it helps the aqueous layer sit on the globe
197
what is the function of the lacrimal gland?
Wash away foreign bodies
198
What is the function of cornea?
Allow light into the eye and begin focusing of the light
199
What are the three layers of the cornea?
Epithelium, Stroma and endothelium
200
What is the epithelium of the cornea like?
Stratified non-keratinising and has limbal stem cells, it is very sensitive to pain via the 5th nerve
201
What is the stroma of the cornea like?
Recular lamina of collagen fibres it is avascular
202
What is the endothelium of the cornea like?
It is a single layer on the back of the eye and it is not replaced and is a fluid pump for the eye.
203
What is the need for pumping of the endothelium?
It stops clouding of the cornea from absorption of water and the pump stops it from swelling
204
What is the anterior chamber?
it is the space between the posterior surface of the cornea and the anterior surface of the iris and lens, it is filled with aqueous humour producesd by ciliary body
205
Where does fluid exit from the anterior chamber?
Exits via the AC angle, the trabecular meshwork is here
206
What are the special quirks of the anterior chamber?
Can see convection currents in the eye
207
What is the function of the iris?
A muscular diaphragm that controls light entry to the eye
208
What muscles of the iris?
Dilator muscle wich is sympathetically innervated and then the sphincter muscle which is parasympathetic with muscarinic receptors
209
What are the two layers of the iris?
The anterior layer has stroma and gives iris colour,and the posterior pigment is all irides and muscle
210
Where is the cilliary body located?
Behind the iris beneath the conjunctiva and scleralateral to the lens.
211
What causes both pupils to be small?
Bright light
extremes of age
opiates and cholinergic.
212
What are the causes of asymetric pupils anisocoria?
Horners syndrome RE, angle closure LE, 3rd nerve palsy LE adie pupil LE cholinergic drop RE anticolinergic drop LE symathomimetic drop LE
213
What are the causes of large pupils?
Low light exited or amphetamines anticholinergics or death
214
What is the function of the lens?
To focus the light or accomodation which is achieved by contraction of the ciliary body
215
How does accommodation work?
the ciliary body (circular muscle) contracts which reduce tension in the zonule and the lens will become rounder for near vision.
when the ciliary body is relaxed it will put tension on the zonule causing it to flatten for the eye to focus on far objects
216
What is presbyopia?
The elasticity of the lens reduces over time and its ability to become round again is reduced leading to difficulty in seeing close up objects
217
what changes happen to the lens over time?
anterior epithelium produces fibres throughout life so the lens enlargens and the centre is the oldest, this can cause cataracts over time if the formation is imperfect
218
What is the aqueous humour?
the fluid that is found around the lens at the anterior portion of the eye
219
What is continuous with the choroid?
the ciliary body
220
What is the pars plicata?
the processes of the ciliary bodies tha secrete aqueous humour.
221
What are the innervation of the ciliary bodies?
3rd cranial nerve muscarinic receptors.
222
What causes pupils to dialate?
anticholinergic drugs like atropine which block the action of the muscles in the pupil
223
What is the vitreous humour?
Fills the space between te posterior surface of the lens and the retina. it is collagen fibres and large negatively charged glycosaminoglyans.it contains the remematns of blood vessels from te optic disc to the lens and becomes more liquid with age
224
What is the retina?
the area of the eye responsible for turning the light signals into nerve impulses
225
What are the layers of the retina?
Photoreceptors (rods and cones) 1st and 2nd order neurones (bipolar and ganglion cells) internerurones amacrine and horizontal cells, neruoglial cells pigment cells and supporting membranes
226
Describe the structure of the retina
There are rods and cones at the bottom lowest area of the eye above the pigment epithelium and choroid. above these layers there is the bipolar cells. The bipolar cells synapse with ganglion cells that transmit the signal to the optic nerve
227
what is the nutrient supply to the photo receptors?
no direct blood supply from diffusion from the choroidal blood supply
228
What are the properties of rods?
dim light perception but no colour
229
What are the properties of cones?
They allow perception of colour and are very concentrated in the fovea
230
What are the most common rods or cones?
Rods
231
What are horizontal cells?
recieve input from photo receptors and moduclate it and also control the activitiy of photoreceptors
232
What are muller of amacrine cells?
receive signals from bipolar cells and ganglion cells and modulate it
233
What is the optic disk?
An area with no rods or cones(blind spot) where the ganglion fibres leave as the optic nerve
234
What are the retinal blood vessels?
supply the inner part of the retina but not the photoreceptors the cast a shadow over photoreceptors
235
What is the Fovea?
the pit or depresssion at the centre of the macula that gives the best visual acuity. foveola is the most sensitive part of the retina contains only cones and no obscuring blood vessels.
236
What is the macula?
the portion of the eye at the centre of the retina that processes sharp clear straight ahead vision highest concentration of cones
237
Where is the macula?
in the temporal area.
238
What is the largest part of the uvual tract?
The choroid
239
What is the choroid?
it is highly vascular and heavily pigmented. it is the middle layer of the posterior eye it supplies blood to the outer retina which is controlled by retinal pigment epithelium
240
What is the optic disk?
Where ganglion cells leave the retina and there are lots of capillaries there are no photo receptors it has a central cup with an opening in the sclera and adventitial tissue the size is variable. good to see ocular and neurological problems
241
What is the sclera?
The tough outer protective layer and is the insertion point of the muscles. it is perforated by nerves and blood vessels and is opaque from collagen fibres
242
How many extraocular muscles are there in each eye?
6. 2 vertical recti 2 horisontal recti and two oblique muscles
243
What is the innervation of most muscles other than the lateral rectus and superior oblique?
the occulomotor nerve CNIII
244
What is the innervation of lateral rectus?
the 6th cranial nerve the abducens
245
What is the innervation of the superior oblique?
the 4th cranial nerve trochlea
246
Where is the origin of most muscles of the eye?
the orbital apex apart from inferior oblique which has an anterior origin.
247
Which muscle is different to the others?
The superior oblique as it runs with a tendon through a trochlea or pully
248
What is the orbit?
the bony protection of the globe. medial ehtmoidal (thin) and lateral zygomatic wall (thick) and the floor maxllary and roof are thin. opens into middle cranial fossa
249
Which bones make up the orbit?
Frontal ethmoid maxilla, zygomatic plus manny more
250
What are the opennings of the orbit?
The optic canal and the superior orbital fissure
251
What runs in the optic canal?
Optic nerve and opthalmic artery and sympathetic plexus
252
What runs in the superior orbital fissure?
the occulormotor 3rd, trochelar 4th, brances of the trigeminal 5th opthalmic and the abducents 6th,
253
What affects the diameter of the pupil?
Changes in light intesity, proximity of object, state of arousal sympathetic nervous system .
254
What is involved in the afferent limb of the pupil?
The retina then the optic nerve which decussates at the chiasm and then the optic tracts. this then goes to the lateral geniculate body of the thalamus and then to the superior colliculus and pre tectal nucleus
255
What is involved with the efferent limb of the pupil?
The pretectal nucleus sends fibres to the edinger-westphal nucleus in the mid brain, parasympathetic fibres of the 3rd cranial nerve and then synapse in the ciliary ganglion in the orbit. and then short ciliary nerves innervate and contract the sphincter pupillae and the ciliaris muscle (accommodation reflex)
increases focus on near vision
256
What are the differences in reflexes of pupils?
One eye affects the other, bilateral input to the pretectal nucleus. very quick response
257
Where is the nucleus for eye reflexes?
The superior colliculus
258
What normally happens when you shine a light in the left eye?
Simultaneous constriction of the pupils
259
What normally happens when you remove the light from the eye?
The pupils both dilate
260
What happens with an afferent pupillary defect with the left eye?
Poor or absent constriction of the left pupil and same on right when shined into left when shone on the right eye normal response. shows that can constrict but can't sense it on the left
261
What happens with an efferent pupillary defect with the left eye?
Could have difference sizes to begin with eg left bigger. shining light in the left causes little or no response in left but good in right. removing the light the left will stay similar and right dilates. when shining in the right it will causes poor or absent constriction of left and normal of right
262
What can cause optic nerve afferent defects?
Optic nere disease, severe retinal disease
263
What can cuase efferent defects?
3rd nerve palsy, adie pupil, iris damage, atropine drugs angle closure glaucoma
264
What is the dark response?
Active dilatation by sympathetic stimulation of dilator muscles and inhibition of sphincter muscle
265
What is Cliliospinal reflex?
pinching the neck on one side causes pupil dilation on that side,
266
What is the intraocular pressure?
15-20mmHg this allows the eye to move without being deformed
267
What is high intraocular pressure called and low?
Glaucoma and hypotony
268
What is the device used to measure intra ocular pressure?
Tonometer
269
What is the normal flow of aqueous humour?
producced in the ciliary body circulates around the lens and through the pupil and leaves the anterior chamber by the AC angle
270
what is conjugate movement?
Movement of the eyes together?
271
What is the purpose of eye movements?
Widens field of vision allow us to follow a target. stabilising vision acurate tracking and it maintains vision
272
What is the function of lateral rectus?
Moves the eye laterally (abduction)
273
What does medial rectus do?
Moves the eye medially (Adduction)
274
What does superior recuts do?
elevates
275
What does inferior rectus?
depresses the eye
276
What does the superior oblique do?
Medially rotates eye inwards (intorsion)
| Depresses the eye and Abducts
277
What does the inferior oblique do?
Laterally rotates the eye outwards (extorsion)
| Elevates and Abducts
278
what is the blood supply for the eye?
Internal carotid branches to give Opthalmic artery which branches to give central retinal artery( inner retina) and ciliary arteries (outer retina circulation and anterior part of the globe). they can be affected in different ways.
279
What is the structure of the retina like?
Tight junctions in capillaries no lymohatics and there is a blood retinal barrier to protect it/
280
What are the chordal capillaries like?
They are leaky and transfer fluid to the retina limited by the retinal pigment epithelium which has a pump fumction it also has photoreceptors
281
What is the photopic visual system?
The system used in good lighting conditions to give detail and color lots of cone receptors
282
What is scotopic visual system?
I is monocromatic for low light conditions and has a function of rod photoreceptors peripheral retina.
283
How long does it take for maximal sensitivity in dark?
10 minutes up to 30 minutes
284
How many types of cones are there?
3 RGB
285
What are the need for the types?
To percieve variety of coulours in our visible spectrum
286
What is abnormal colour vision?
colourblindnes can be caused by diseae or genetice can make it hard do distinguish
287
How wide is the visual field?
200degrees horizontal 150 degrees vertical
288
How are visual fields measured?
Angles from nose and edge of eye
289
What is it called if the eye is too long for the refractive power of the lens?
Myopia
290
What is is called if the eye is too short?
hyperopia
291
What is astigmatism?
When the refractive power of the cornea is not even
292
What is accomodation?
Changing the focussing of the lens to get a clear image
293
What causes change in accommodation with age?
The lens is less elsastic called presbyopia
294
What is visual acuity?
The ability to see detail or resolution. it is best at the centre.
295
How do you test visual acuity?
Using a snellen chart which is most commonly used or other
296
Wat is binocular vision?
Seeing one image with both eyes.
297
What is stereopsis?
Depth perception. it is not present at birth
298
What is strabismus?
eyes looking in different ways
299
What is the visual pathway?
Retina (cone, rod, bipolar, ganglion neurone),
optic nerve,
optic chiasm and optic tracts
thalamus (lateral geniculate ganglion)
optic radiations (temporal and parietal lobes)
visual cortex and visual association cortex
300
What fibres cross over at the chiasm?
medial fibres of the eyes with information from the temporal field.
301
What type of fibres do the optic tracts carry?
Fibres from the temporal retina( nasal visual field from the same side and the nasal fibres from the temporal visual field from the oposite side to give depth
302
What fibres enter the parietal lobe radiation?
The superior fibres from the lower visual field
303
What fibres enter the temporal radiation?
The inferior fibres which convey iformation from the superior visual field
304
Where is the visual cortex?
In the calcarine sulcus either side on the medial surface of the occipital lobe
305
Where do the fibres from the macula go?
To the posterior pole where the lood supply is from the middle and posterior cerebral artery
306
What kind of problems are there with the retina?
Total loss of vision in one eye, loss of part of cisiual field in one eye, loss of upper or lower half of field of vision los of centre of vision macular degeneration and tunnel vision
307
What are problems relating to the optic nerve?
Enlarged blind spot(swollen optic disc, loss of centre of visions(optic neuritis), Loss of vision in and arc shape(glaucoma) glaucoma(tunnel vission)
308
What is bitemporal hemianopia?
The temporal field of each eye is gone. Often caused by pituitary tumours
309
What happens when the optic tracts is damaged.?
It caues contralateral loss with same part of each eye, homonymous left of each.
310
What is incongruous?
not the same on both sides
311
What happes in optic radiations?
Contralateral homonymus field defects
312
What is macular sparing?
when the macula is spared as there is a posterior cerebral artery stroke but area for macula is supplied by middle
313
What is a blow out fracture?
frontal sinus broken causing double vision
314
go back to eye lecture?
cvd
315
What are the areas of a neuron?
Dendrites, Cell body, Myelinated axon, Axon terminals
316
What are dendrites?
Areas of nerve cells that receive input from other neurons
317
where is the first action potential?
Axon hillock
318
When are neurons formed?
Most before birth lots later though
319
What is high concentration in cell body of a neuron?
Nissel substance which is rough endoplasmic reticulum
320
What are the two types of neronal commuication?
Chemical for most and also electrical which are less abundant
321
What are electrical synapses like?
They have gap junctions electron dense material either side of junction
322
How does a chemical synapse work?
calcium influx into the presynaptic bulb causes the release of neurotransmitters that bind to receptors on the post synaptic membranes
323
What are dendritic spines?
They are small projections from the dendrites that hace post synaptic membranes
324
What is plasticity?
The ability of the synapse to be changed gained lost and strengthened. the basis of learning
325
How doe neurones differ?
Size shape electical properties neurotransmitters.
326
What are upper motor neurones like?
Large exitatory glutaminergic and pyramidal cells
327
Wat are striateal interneurons?
Small inhibitory GABAergic
328
How many axons are there in one cell?
Many
329
What are oligodendrocytes?
They myelinate neurons in the CNS not schwann cells. They are helping saltatory conduction providing metabolic support for axons
330
How many neurones can one oligodendrocyte myelinate?
Many
331
What is a myelin sheath?
Multiple layers of membrane with high 70% lipid and 30%protein. involved in compaction
332
What are microglia?
They are derived from yolk sac progenitors, resident immune cells of the CNS the resting state have lots of procecess then when activated they retract and become motile
333
What do the microglia do?
They help with synaptic placitity and pruning, immune sureillance and phagocytosis debris/microbes
334
What are astrocytes?
Star shaped cells but have a high heterogeneity
they have marker proteins such as GFPA
fibrous in white matter
protoplasmic in grey matter
335
What is the purpose of astrocytes?
Part of the blood-brain barrier, also go into nodes of Ranvier. they are progenitors of nerual cells, most abundant and give structure, homeostatic metabolic support through neurovascular coupling
336
How are fMRI and astrocytes linked?
They change blood flow in the brain
337
What are some special astrocytes?
Radial glia - progenitors of neural cells
Bergman glia in cerebellum
Muller cells in the retina
338
What symptoms of MND are due to loss of...?
Motor neurons microglia and astrocytes
339
What are involved in CNS lesisons in MS?
Oligodendroytes but also T lymohocytes and neurons
340
What is a tract?
An abundance of axons in the same directions
341
What are commissures?
Fibres that cross the mid line
342
What is a nucleus in the brain?
An area with an abundance of nuclei (cell bodies)
343
What is a ganglion?
Concentration of cell bodies in the PNS
344
What are some of the features of the blood brain barrier?
Tight junctions, foot proceses of astrocytes, pericytes basement membrane whcih lack fenestrations
345
Where are the Blood brain barrier thinner?
CIrcumventricular organs of the brain:
Pituitary, pineal gland, hypothalamus, and area postrema vomiting centre for body.
346
Where is CSF removed?
the arachnoid granulations and the lymphatics of the brain,along nerves
347
What are ependymal cells?
Epithelial-like cells that line ventricles and central canal of the spinal cord.
They produce CSF they are ciliated cells to give flow
348
What is the choroid plexus?
The frond like projections of ependymal cells vasuclarised and main site of CSF production.
349
What makes neurons negative inside relative to outside?
negative proteins inside the cytoplasm. potassium and chloride can leave. sodium can cross with difficulty and have sodium potassium pumps
350
What role does diffusion have in the maintenance of themembrane potential?
Chloride diffuses in against electrostatic pressure, sodium in with the electrostatic pressure and potassium out against the presure
351
Which ions are inside the cell?
Negative ions, potassium
352
Which ions are usually outside the cell?
Chloride,sodium
353
How is information transmitted through neurons even though they can only be on or off?
By the rate of firing of the cells
354
What doe neurotransmitters do?
They bind to ion channels and cause them to open.
355
What do exxcitatory neurotranmitter do?
Depolarise the membrane and increase the probability of an action potetnial taking place. excitatory post synaptic potential
356
What do inhibitory neurotransmitters do?
They hyperpolarise the cell membrane which makes it less likely for the cell generate an action potential called inhibitory post synaptic potentials
357
What is spatial sumation?
When signals from two neurons combine to form a larger signal making it more likely for the action potential to happen
358
What is the significance of the axon hilluck?
If it doesn't get a big enough voltage at the hillock it won't transmit down the axon
359
What happens once the threshold potential is met?
voltage gated sodium channels open and depolarise the membrane. then they close and potassium voltage gates open to depolarise. then becomes hyper polarised
360
What is the absolute refractory period?
Moreover, the absolute refractory period is the interval of time during which a second action potential cannot be initiated, no matter how large a stimulus is repeatedly applied
361
What is the relative refractory period?
When the membrane becomes hyperpolarised.
362
What is the speed of myelinated axonal transmission?
Up to 150m/s
363
What is the speed of unmeylinated axons?
2-5m/s
364
What does novichok do?
It interferes with acetylcholine by stoping acetylcholine esterase from breaking down the ACh
365
How is neurotransmitter regulated?
Enzymatic breakdown,
366
What does atropine do?
Can remove ACh from receptors
367
What are the 5 fundamental processes of synaptic transmission?
Manufacture of neurotransmittersStorage of the neurotransmittersRelease of thetransmitter via action potentialInteract with post-synaptic reveptors- diffusion across the synapseinactivation- breakdown or re-uptake
368
What are some fast acting neurotransmitter?
Acetylcholine, Glutamate Gamma-aminobutyric acid
369
What are neuroodulaters with egs?
They are slower acting such as Dopamine noradrenalin Serotonin
370
What does procaine and lignocaine do?
local anaesthetics block sodium channels
371
What are the most useful imaging techniques?
MRI and CT, Cerebral angiography
372
What is x-ray useful for?
Skull damage MR safety
373
What scanner is used for angiography?
CT
374
What are some problems with CT?
High dose radiation, limited anatomical detain somewhat, contrast agents are allergic, better than MRI for bone topics
375
How are CT presented?
Looking from the bottom of the bed to the top
376
What is the strength of most MRI magnets?
T1.5 or T3
377
What are white matter fibre tracts?
Water diffusion along fibre pathways
378
What is PET-CT scanning?
used to locate brain tumours
379
What does an extradural haemotoma look like?
Between the dura and skull causes brain compression. blood next to skull
380
What colour is blood on a CT?
White
381
What is a cerebral contusion?
"bruise" on the brain where it is dammaged
382
What is diffuse axonal injury?
When white matter fibres are dammaged
383
What is a T2 scan?
CSF white
384
What is a T1 weighting?
CSF white
385
What is the use of weighting?
It can help distinguish what the lesions are
386
What can you see on stroke patients?
See which artery was damaged
387
Give 3 functions of the cranial meninges.
1. Protects the brain and spinal cord form injury.2. Provides a framework for cerebral and cranial vasculature. 3. Provides a space for the flow of CSF.
388
What are the 3 meningeal layers?
1. Dura mater (outermost).2. Arachnoid mater.3. Pia mater (inner most).
389
What are the 2 connective tissue sheets of dura mater?
1. Endosteal layer - lines the cranium. 2. Meningeal layer.
390
Where are the dural venous sinuses located?
Between the endosteal layer of dura and the meningeal layer.
391
What vein do the dural venous sinuses drain into?
The internal jugular veins.
392
Name 3 locations where the dura mater folds inwards as dural reflections?
1. Falx cerebri.2. Tentorium cerebelli.3. Falx cerebelli.
393
Where is the falx cerebri located?
It lies in the longitudinal fissure between the cerebral hemispheres.
394
Where is the tentorium cerebelli located?
The tentorium cerebelli is a thick fibrous roof lying over the posterior cranial fossa and the cerebellum.
395
Where is the falx cerebelli located?
Between the 2 lobes of the cerebellum.
396
What lies beneath the arachnoid mater?
The subarachnoid space containing CSF and arteries.
397
What is the function of the blood-brain barrier?
It protects the brain by preventing the passage of some substances from the circulation into the nervous tissue.
398
Which meningeal layers are highly vascularised?
The dura and pia mater. The arachnoid mater is avascular.
399
Name the 3 elements that make up the blood-brain barrier.
1. Capillary endothelial cells. 2. Basement membrane.3. Astrocytic end-feet.
400
What are the 2 main arteries that supply blood to the brain?
1. Vertebral arteries.2. Internal carotid arteries.
401
Which arteries supply about 80% of blood to the brain?
The internal carotid arteries.
402
What are the vertebral arteries a branch of?
The subclavian arteries.
403
Where do the vertebral arteries enter the skull?
Through the foramen magnum.
404
What are the internal carotid arteries branches of?
The common carotids. Arise from bifurcation at the same level as the upper border of the thyroid cartilage.
405
What do the vertebral arteries supply?
The posterior cerebrum and thecontents of the posterior cranial fossa.
406
What do the internal carotid arteries supply?
The anterior and middle parts of the cerebrum and the diencephalon.
407
Where do the internal carotid arteries enter the skull?
Through the carotid foramina.
408
What are the terminal branches of the internal carotid arteries?
The middle and anterior cerebral arteries.
409
What does the middle cerebral artery supply?
The lateral surface of the hemispheres.
410
What does the anterior cerebral artery supply?
The medial aspect of the hemispheres and the corpus callosum.
411
What does the posterior cerebral artery supply?
The occipital lobe.
412
What artery passes through foramen spinosum?
The middle meningeal artery.
413
What do the two vertebral arteries form?
The basilar artery.
414
Where is a berry aneurysm likely to occur?
At branching points in the circle of willis, especially at the anterior communicating artery.
415
What is a berry aneurysm?
A sac-like out pouching that will progressively enlarge until it ruptures resulting in haemorrhage.
416
What are the two types of stroke?
1. Ischaemic.2. Haemorrhagic (intracerebral or subarachnoid).
417
Where are dural venous sinuses located?
In between the endosteal and meningeal layers of dura.
418
Where do cerebral veins drain into?
Into dural venous sinuses.
419
What does the great cerebral vein drain?
Deep brain structures.
420
What sinus does the great cerebral vein drain into?
The straight sinus.
421
Where is the straight sinus located?
In the midline of the tentorium cerebelli.
422
What vessels lie in the cavernous sinus?
- Cn 3, 4, 5(1), 5(2) and 6. - Internal carotid artery.
423
Why is the cavernous sinus of clinical importance?
If this sinus is infected Cn 3, 4, 5(1), 5(2) and 6 and the internal carotid artery could be affected.
424
How do dural venous sinuses and veins outside the skull communicate?
Via emissary veins.
425
What is the clinical significance of emissary veins?
They represent a possible route for infection to spread into the cranial cavity.
426
Briefly describe the pathway of venous drainage starting at the great cerebral vein.
Great cerebral vein -> straight sinus -> transverse sinus -> sigmoid sinus -> internal jugular vein -> jugular vein -> brachiocephalic vein -> SVC.
427
What sinuses form the confluence of sinuses?
The straight sinus and the superior sagittal sinus.
428
Where is the largest aggregation of choroid plexus?
In the lateral ventricles.
429
Where is the majority of CSF produced?
In the lateral ventricles (greatest amount of choroid plexus here`).
430
What is ependyma?
A thin-epithelial like structure lining the ventricles.
431
Tight junctions prevent the passage of fluid into the ventricles. Why is this important?
It means that the volume and composition of CSF can be closely controlled.
432
What embryonic part of the brain is the midbrain formed from?
Mesencephalon.
433
What embryonic part of the brain is the pons formed from?
Metencephalon of Rhombencephalon.
434
What embryonic part of the brain is the medulla oblangata formed from?
Myelencephalon of Rhombencephalon.
435
What are the characteristic features of a cervical vertebra?
- Small vertebral body.- Transverse foramen for vertebral arteries. - Bifurcation of spinous processes (except C7).- Triangular intervertebral foramen.
436
What region of the vertebral column has the greatest capacity for rotation?
The thoracic region.
437
What region of the vertebral column has the least capacity for flexion?
The thoracic region; this is due to the presence of the ribcage.
438
What are the 2 components of an intervertebral disc?
1. Nucleus pulposus.2. Annulus fibrosus: concentric layers of collagen surrounding the nucleus pulposus.
439
What does the ligamentum flavum connect?
Connects the laminae of adjacent vertebrae.
440
Where does the spinal cord end?a) in an adult.b) at birth.c) in the embryo.
a) L2.b) L3.c) runs the entire length of the vertebral column.
441
Where would you insert a lumbar puncture needle?
At the L3/L4 level in the sub-arachnoid space in order to take CSF.
442
Where would you insert an epidural needle?
Between the dura mater and vertebrae in order to inject anaesthesia.
443
What is the conus medullaris?
The tapered, lower end of the spinal cord.
444
What is the filum terminale?
A fibrous strand that proceeds downwards from the apex of the conus medullaris.
445
What is the cauda equina?
Spinal nerves from the lower spinal cord that hang obliquely downwards.
446
Define dermatome.
An area of skin with a sensory nerve supply from a single root of the spinal cord.
447
What is the dermatome for the thumb?
C6.
448
What is the dermatome for the knee?
L3.
449
What is the dermatome for the big toe?
L5.
450
Name 4 ascending spinal pathways.
1. DCML.2. Spinothalamic.3. Spinocerebellar. 4. Spinoreticular.
451
What sensations does the DCML pathway convey?
Fine touch, 2-point discrimination and proprioception.
452
What sensations does the spinothalamic pathway convey?
convey pain, itch, temperature, tactile and proprioceptive information from the contralateral side of the body to the brain
453
Describe the DCML pathway.
Fine sensation is detected by touch or proprioception receptors. Afferent signals are carried along 1st order neurones to the dorsal columns and up to the medulla where they synapse. 2nd order neurones decussate in the medulla and travel up to the thalamus where they synapse. 3rd order neurones then travel through the internal capsule to the somatosensory cortex.
454
Which dorsal column would an afferent signal from the lower limb use?
The gracile fasciculus (medial part of dorsal column). They then synapse at the gracile nucleus of the medulla.
455
Which dorsal column would an afferent signal from the upper limb use?
The cuneate fasciculus (lateral part of dorsal column). They then synapse at the cuneate nucleus of the medulla.
456
Describe the spinothalamic pathway.
Nociceptors or thermoreceptors detect pain, temperature or crude touch. 1st order neurones carrying these signals enter the spinal cord and ascend 2-3 spinal levels before synapsing in the dorsal horn of grey matter. 2nd order neurones decussate either through the anterior or lateral tracts and then travel up to the thalamus where they synapse. 3rd order neurones travel through the internal capsule to the primary somatosensory cortex.
457
Where is the somatosensory cortex located?
Post-central gyrus in parietal lobe.
458
What sensations is the lateral spinothalamic tract responsible for?
Pain and temperature.
459
What sensation is the anterior spinothalamic tract responsible for?
Crude touch.
460
What is the function of the spinocerebellar tracts?
They carry unconscious proprioceptive information to the ipsilateral cerebellum.
461
Do the fibres decussate in the spinocerebellar tracts?
No! They go to the ipsilateral cerebellum.
462
What sensation does the spinoreticular tract convey?
Deep/chronic pain.
463
Name 5 descending pathways.
1. Corticospinal. 2. Vestibulospinal.3. Rubrospinal.4. Tectospinal. 5. Reticulospinal.
464
Where in the thalamus do the DCML and spinothalamic tracts synapse?
In the ventral posterio-lateral division (VPL) of the nucleus of thalamus.
465
What descending pathways are described as pyramidal?
Corticospinal and corticobulbar tracts - responsible for voluntary control.
466
What descending pathways are described as extrapyramidal?
Vestibulospinal, rubrospinal, tectospinal, reticulospinal - responsible for involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion.
467
Are there any synapses within the descending pathways?
No. At the termination of the descending tracts, the neurones synapse with a lower motor neurone. (All the neurones within the descending motor system are UMNs).
468
What are the corticospinal tracts responsible for?
The control of voluntary muscles. Anterior - axial muscles. Lateral - limb muscles.
469
Describe the corticospinal tracts.
Originate in the primary motor cortex, descends through corona radiata and internal capsule to the medullary pyramids. 90% decussates here and becomes the lateral corticospinal tract; the remaining 10% forms the anterior corticospinal tract. The anterior tract then decussates through the anterior white commissure. Both tracts terminate in the ventral horn.
470
Describe the corticobulbar tracts.
Originate in the primary motor cortex, descends through corona radiata and internal capsule to the brainstem. The fibres terminate on motor nuclei of cranial nerves. They synapse with LMN's which carry motor signals to the face and neck.
471
Where do the extrapyramidal tracts originate?
The brainstem.
472
Where do the vestibulospinal tracts originate and what are they responsible for?
1. Originate from vestibular nucleus.2. Responsible for muscle tone and postural control.- Remains ipsilateral.
473
Where do the reticulospinal tracts originate and what are they responsible for?
1. Originate from reticular formation.2. Responsible for spinal reflexes.
474
What are the 3 layers of the eye?
Outer Layer: Sclera and Cornea
Middle Layer: Uvea
Inner Layer: Retina
475
how much of the refractive power comes from the cornea?
2/3rd,
Other 1/3 comes from the lens refractive power
476
What makes up the uvea (middle part of the eye)?
Iris
Ciliary body
Choroid
477
What muscles are contained in the iris?
Sphincter Pupillae
| Dilator Pupillae
478
What is the function of the ciliary body in the uvea?
Glandular epithelium which produces aqueous humor
| Smooth muscle that controls accommodation
479
What is the function of the choroid in the uvea?
Blood supply to the outer third of the retina
480
Explain Phototransduction of rod cells in the light
Rhodopsin chromophore retinal absorbs light photons
Causes conformational change from cis-11 retinal to trans-retinal
Opsin is activated
GTP binds to transducin
Transducing GPCR activates phosphodiesterase (PDE)
PDE breaks down cGMP
cGMP channels close and therefore there is less glutamate
less glutamate
Through ON/OFF cells, the level of glutamate causes depolarisation of hyperpolarisation of the bipolar/ganglion cells
481
What are 2 properties of rod cells?
Highly senstive to light - lots of rod cells in the peripheral retina
Have low visual acuity - due to retinal convergence of 3 rod cells at a single ganglion cell
482
what are 2 properties of cone cells?
Low sensitivity to light - need high light intensity for coloured vision
High visual acuity due to 1 cone cell per ganglion cell
483
How does the attenuation reflex work?
Muscles attached to the ossicles contract causing an increased rigidity of the tympanic membrane and therefore sound conduction is diminished in the middle ear
484
where is the organ of corti found?
In the scala media
485
What is endocochlear potential?
endolymph electrical potential is greater than the perilymph electrical potential and therefore this enhances auditory conduction
486
What is the auditory pathway from the eighth cranial nerve?
ECOLI:
Eighth Nerve (vestibulocochlear)
Cochlear nuclei (ipsilateral side) (medulla)
Olivary nucleus (superior on the contralateral side) (medulla)
Lateral lemniscus (PONS)
Inferior Colliculus (Cerebral peduncle)
medial geniculate body (MGB) (thalamus)
487
explain the process of neuralation?
Notochord develops in the mesoderm
The notochord induces the thickening of the overlying ectoderm cells
The ectoderm cells then invaginate to form the neurual groove and the neural folds.
Continued invagination brings the neural folds together.
This produces the neural tube and some neural crest cells on the top.
The neural tube forms the CNS
The neural crest cells form the PNS and other glial cells involved in the support of the nervous system
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What is the internal Capsule?
White matter structure containing myelinated fibres of ascending and descending tracts that pass between the basal ganglia and connect the cerebral hemispheres with the subcortical structures, brainstem and spinal cord.
