Week 8 - Diencephalon, Basal Ganglia, Limbic Systems and Cerebral Cortex

Question 1

What are the 4 components of the diencephalon?

Answer 1

Epithalamus
Thalamus (+ Metathalamus)
Subthalamus
Hypothalamus

Question 2

Define the diencephalon.

Embryologically, what is it derived from?

Answer 2

The caudal part of the forebrain

Prosencephalon (forebrain)

Question 3

What is the blood supply of the diencephalon?

Answer 3

Posterior cerebral artery

Posterior communicating artery

Question 4

What is the function of the diencephalon?

What other areas of the brain does the diencephalon connect with?

Answer 4

It is the primary relay and processing centre for sensory information and autonomic control

Limbic system, basal ganglia, primary sensory area (e.g. auditory and visual)

Question 5

What is the relation of the 3rd ventricle to the structures of the diencephalon and lateral ventricles?

Answer 5

narrow midline cleft between and below the two lateral ventricles which communicate with the 3rd ventricle via the interventricular foramen of Monro

in between the left and right thalami

Question 6

What are the borders of the diencephalon?

roof, floor, anterior/posterior walls

Answer 6

roof - choroid plexus of the 3rd ventricle

floor - optic chiasma, infundibulum, mammillary bodies and uppermost part of the mesencephalic tegmentum

anterior wall - laina terminalis, anterior commissure and anterior column of the fornix

posterior wall - stalk of hte pineal gland, posterior commissure and Habenular commissures

Question 7

What 5 structures make up the epithalamus?

Answer 7

1. stria medullaris
2. posterior commissure
3. habenular nuclei (medial and lateral)
4. pineal body
5. paraventricular nuclei (anterior and posterior)

Question 8

What is the stria medullaris?

Answer 8

A fibre bundle which projects from a number of areas including the limbic system and basal ganglia, to the habenula.

Question 9

What is the posterior commissure?

Answer 9

A transversely-orientated commissural white matter tract that connects the two cerebral hemispheres along the midline.

Question 10

What is the habenular?

What is its function?

Answer 10

part of the epithalamus
receives input from the brain via the stria medullaris.
Outputs to many midbrain areas including neuromodulators - e.g. dopamine, noradrenaline and serotonin

Divided into lateral (limbic) and medial (motor) parts.

Functions include - pain processing, reproductive behaviour, nutrition, sleep-wake cycles, stress responses and learning

Question 11

What is the pineal body?

What is its function?

Answer 11

an endocrine gland, made up of pinealocytes which secrete melatonin in response to darkness.
Also secretes many hormones that have important regulatory functions on other endocrine organs including - thyroid, parathyroids, adrenals and gonads.

Question 12

Thalamic Anterior Nuclear Group

1. Where is the input from?
2. Where is the output too?
3. What are its connections role?

Answer 12

1. input from mammillary bodies (of the hypothalamus)
2. output to the cingulate cortex
3. emotional aspects of behaviour, instinctive drives and memory

Question 13

Thalamic Medial Nuclear Group

1. Where is the input from?
2. Where is the output too?
3. What are its connections role?

Answer 13

1. input from prefrontal cortex reciprocal fibres, hypothalamus, amygdala and other thalamic nuclei
2. output to prefrontal cortex
3. mood and emotion

Question 14

What are the 6 nuclei divisions of the lateral nuclear group?

Answer 14

lateral dorsal 
lateral posterior 
pulvinar 
ventral anterior 
ventral lateral 
ventral posterior

Question 15

What are the two metathalmic nuclei?

Where are they located?

What pathways do they have roles in?

Answer 15

medial geniculate nucleus
lateral geniculate nucleus

two bumps off the ventral posterolateral surface of the pulvinar nucleus

MG = auditory pathway 
LG = visual pathway

Question 16

Lateral dorsal, lateral posterior and pulvinar nuclei

What is their role?

Answer 16

Role in receiving fibres regarding emotion and behaviour

Question 17

Ventral Anterior Thalamic Nucleus (lateral group)

1. Where is the input from?
2. Where is the output too?

Answer 17

1. input from basal ganglia

2. projects axons to premotor cortex

Question 18

Ventral Lateral Thalamic Nucleus (lateral group)

1. Where is the input from?
2. Where is the output too?

Answer 18

1. input from basal ganglia

2. projects axons to primary motor cortex (pre-central gyrus)

Question 19

Ventral Posterior Thalamic Nucleus (lateral group)

1. Where is the input from?
2. Where is the output too?

Answer 19

1. input from brainstem and spinal cord

2. projects axons to somatosensory cortex (relaying sensory information)

Question 20

Intralaminar Nucleus of the Thalamus

1. Where is it located?
2. Where is its input from?
3. Where is its output too?

Answer 20

1. located within the internal medullary lamina (‘Y’ shaped structure)
2. input from the brainstem through ascending reticular activating systems (ARAS), and spinothalamic and trigeminothalamic tracts
3. output to the cerebral cortex and basal ganglia (caudate nucleus and putamen)

Question 21

What is the role of the intralaminar nucleus?

What happens if there is a lesion in the intralaminar nucleus?

Answer 21

reinforcement of learning and action (mechanism for activation of the cerebral cortex)

Reduction in perception of pain and level of consciousness

Question 22

What are the two types of intralaminar nuclei of the thalamus?

Answer 22

centromedian nucleus (larger of the two) 
parafascicular nucleus

Question 23

What is the reticular nucleus of the thalamus?

What is its role?

Answer 23

a thin layer of cells located on the lateral aspect of the thalamus
located between external medullary lamina and the internal capsule

receives collaterals of thalamocortical and corticothalamic fibres

Question 24

Define the subthalamus

Answer 24

part of the diencephalon that lies between the posterior part of the thalamus and the tegmentum of the midbrain.
It is also posterior and lateral to the hypothalamus.

Question 25

Define the hypothalamus

Answer 25

the ventral-most part of the diencephalon | found below the thalamus and ventromedial to the subthalamus

Question 26

What is the relation of the hypothalamus to the 3rd ventricle?

Answer 26

it forms the floor and lower part of the lateral wall of the 3rd ventricle

Question 27

What are the anterior hypothalamic nuclei? (x5)

Answer 27

1. preoptic 2. anterior hypothalamic 3. supraoptic 4. suprachasmatic 5. paraventricular

Question 28

What are the middle hypothalamic nuclei? (x3)

Answer 28

1. dorsomedial hypothalamic 2. ventromedial hypothalamic 3. arcuate

Question 29

What are the posterior hypothalamic nuclei? (x2)

Answer 29

1. posterior hypothalamic | 2. nuclei of the mammillary body

Question 30

What are the roles of the hypothalamic nuclei?

Answer 30

AUTONOMIC - controlling heart rate, urine release from bladder, movement of food through G.I. tract and blood vessel diameter. ENDOCRINE - regulates pituitary gland secretions that influence: metabolism, ion concentration, sexual development and functions. MUSCLE CONTROL - e.g. muscles involved in swallowing and stimulates shivering TEMPERATURE REGULATION - promotes heat loss when hypothalamic temperature increases through sweat production. promotes heat production when hypothalamic temperature decreases through shivering REGULATION OF FOOD/WATER INTAKE - hunger centre promotes eating and satiety centre inhibits eating. thirst centre promotes water intake EMOTIONS - large range of emotional influences over body functions, influences stress-related and psychosomatic illnesses, as well as feelings of fear and rage REGULATION SLEEP-WAKE CYCLE - coordinates responses to the cycle with other areas of brain (e.g. reticular system) SEXUAL DEVELOPMENT + BEHAVIOUR - stimulates sexual development, arousal and behaviours

Question 31

What is the function of the preoptic nucleus of the hypothalamus?

Answer 31

autonomic (parasympathetic) temperature regulation sexual development and behaviour note - preoptic area is larger in males that females.

Question 32

What is the function of the supraoptic nucleus of the hypothalamus?

Answer 32

endocrine function

Question 33

What is the function of the suprachasmatic nucleus of the hypothalamus?

Answer 33

Regulation of the sleep-wake cycle - receives direct input from the eyes concerning light-dark cycles and is implicated during jet lag.

Question 34

What is the function of the paraventricular nucleus of the hypothalamus?

Answer 34

endocrine function

Question 35

What is the function of the anterior hypothalamic nucleus?

Answer 35

autonomic (parasympathetic) | temperature regulation

Question 36

What is the function of the dorsomedial hypothalamic nucleus?

Answer 36

sexual development and behaviour

Question 37

What is the function of the ventromedial hypothalamic nucleus?

Answer 37

regulation of food and water intake | sexual development and behaviour

Question 38

What is the function of the posterior hypothalamic nucleus?

Answer 38

autonomic (sympathetic) | temperature regulation

Question 39

What is the function of the lateral hypothalamic area?

Answer 39

``` autonomic (sympathetic) muscle control regulation of food and water intake emotions regulation of sleep-wake cycle ```

Question 40

What is the function of the arcuate nucleus of the hypothalamus?

Answer 40

endocrine | regulation of food and water intake

Question 41

What structures make up the basal ganglia?

Answer 41

``` caudate nucleus lentiform nucleus amygdaloid claustrum substantia nigra (in the midbrain) subthalamic nucleus ```

Question 42

What structures make up the lentiform nucleus?

Answer 42

putamen | globus pallidus

Question 43

What basal ganglia structures make up the corpus striatum?

Answer 43

lentiform nucleus (putamen and globus pallidus), and the caudate nucleus

Question 44

Where is the amygdala found?

Answer 44

found within the temporal lobe, deep to the uncus | found at the anterior end of the inferior horn of the lateral ventricles.

Question 45

What is the subthalamic nulceus? Where is it found?

Answer 45

traditionally part of the subthalamic region but functionally grouped with the basal nuclei. Shaped like a biconcave lens. Lies between thalamus (above) and substantia nigra (below).

Question 46

What are the two cell divisions in the substantia nigra?

Answer 46

pars reticulata | pars compacta

Question 47

What is the role of pars compacta?

Answer 47

produces dopamine, an inhibitory neurotransmitter. | important in maintaining the striatal pathway (main input of the basal ganglia)

Question 48

What is the function of the globus pallidus in the corpus striatum?

Answer 48

it send fibres (efferents) to the substantia nigra pars reticulata and to the thalamus it receives fibres (afferents) from the striatum (caudate nuclues and putamen)

Question 49

What are the main inputs to the basal ganglia (striatum)?

Answer 49

* Entire Cerebral Cortex - glutamatergic fibres releasing glutamate to excite the striatum or striatal neurons * Substantia Nigra - fibres arise in pars compacta and reach the striatum to form the nigrostriatal connections. Nigrostriatal fibres are dopaminergic - releasing dopamine * Thalamus - thalamostriatal connections/afferents, which carry glutamate (glutamatergic) * Reticular Formation of the Brainstem (midbrain) - afferents are noradrenergic supplying NA to the basal ganglia. * Locus Coeruleus - afferent fibres are serotonergic (supplying serotonin)

Question 50

What are the functions of the basal ganglia?

Answer 50

Planning and modulation of movement pathways Control of movement and learning Coordinating motivation with body movement - inhibiting individual behaviour in a complex social interaction and small voluntary movements

Question 51

What is the function of the mammillary body nuclei?

Answer 51

Part of the hypothalamus and limbic system. | Receives afferent fibres from the hippocampus and projects to the anterior nuclei of the thalamus and brainstem.

Question 52

Define the hypothalamus

Answer 52

part of the diencephalon the brain centre for regulation of the autonomic nervous system. Generally activation of the posterior hypothalamic domain is associated with sympathetic responses and anterior hypothalamic domain is associated with parasympathetic activity.

Question 53

What is the relation of the pituitary gland to the hypothalamus?

Answer 53

connected to the hypothalamus via the infundibulum | hormones are produced in the hypothalamus that are released from the posterior pituitary

Question 54

What hormones are produced in the hypothalamus and where?

Answer 54

supraoptic nuclei - produces vasopressin paraventricular nuclei - produces oxytocin These are transported to the posterior pituitary in the hypothalamohypohyseal tract

Question 55

What releasing factors are produced in the hypothalamus and where?

Answer 55

``` adrenocorticotropic hormone luteinising hormone follicle-stimulating hormone thyroid-stimulating hormone growth hormone prolactin ``` produced in the anterior pituitary

Question 56

Define interthalamic adhesion

Answer 56

flattened band of tissue connecting the two thalami at their medial surfaces

Question 57

Define the hypothalamic sulcus

Answer 57

a groove in the lateral wall of the 3rd ventricle, marking the boundary between the thalamus and hypothalamus

Question 58

What is the role of the medial geniculate nucleus?

Answer 58

part of the auditory thalamus and represents the thalamic relay between the inferior colliculus and auditory cortex

Question 59

What is the role of the lateral geniculate nucleus?

Answer 59

relay centre in the thalamus for the visual pathway. Receives major sensory input from the optic nerve travelling from the retina. Sends connections to the primary visual cortex.

Question 60

What is the role of the limbic system?

Answer 60

processing of memories creation of emotional states, drives and associated behaviours reproduction nutrition - hunger/thirst

Question 61

Describe the limbic system

Answer 61

forms a ring surrounding the diencephalon | made up of parts of the cerebrum and diencephalon

Question 62

Describe the basal ganglia motor loop for coordinated movements What is the role of this motor loop?

Answer 62

motor and sensory information from the primary motor and sensory cortices to the putamen via descending tracts, originating from pyramidal cells in the 5th layer of the cerebral cortex. Putamen either facilitates movements or inhibits/eliminates unwanted movements (which also reduce muscle tension). It sends this to the thalamus which projects axons to the primary motor cortex completing the closed circuit. Coordinated voluntary movement following long-term procedure training, e.g. gymnastics.

Question 63

Describe the basal ganglia cognitive association loop What is the role of this cognitive loop?

Answer 63

Axons/projection fibres from the brain (motor and sensory areas) travel to the caudate nucleus. Two types of feedback - positive when movement is accomplished and negative when movement is unsuccessful. Fibres travel via the thalamus and sends fibres back to the cerebrum to complete the circuit. Rewarding learning of movements. (positive/negative feedback)

Question 64

What is the function of the nucleus accumbens? What other basal ganglia structure is it closely related to?

Answer 64

its function is related to addiction caudate nucleus

Question 65

Describe the interconnections between the cerebral cortex and the basal ganglia

Answer 65

Efferent fibres sent from cerebral cortex, intralaminar thalamic nuclei and pars compacta of the substantia nigra to the putamen and caudate - the 'input' regions of the basal ganglia. The lateral (external) and median (internal) globus pallidus receives fibres from the putamen and caudate nucleus The lateral globus pallidus sends fibres to the subthalamic nucleus which sends fibres back in response to the median globus pallidus. Median globus pallidus forms connections by sending axons to the thalamus Caudate and putamen have reciprocal connections to the substantia nigra of the midbrain

Question 66

What is the primary function of the caudate nucleus, putamen and globus pallidus of the basal ganglia?

Answer 66

control of posture and movement

Question 67

What is the relation of the caudate nucleus to the ventricles and other structures of the brain?

Answer 67

Lies in the wall of the lateral ventricle Head of the caudate is medial to the internal capsule - forming a prominent bulge in the lateral wall of the anterior horn of the ventricle The tapered tail of the caudate nucleus follows the curvature of the lateral ventricle into the temporal lobe

Question 68

What is the relation of the putamen and globus pallidus to the ventricles and other structures of the brain?

Answer 68

Lie lateral to the internal capsule, deep to the cortex of the insula

Question 69

What structure(s) make up the neostriatum (striatum)?

Answer 69

caudate nucleus and putamen

Question 70

What structure(s) make up the paleostriatum?

Answer 70

globus pallidus

Question 71

What happens if the basal ganglia becomes damaged? What disorders are associated with pathophysiology of the basal ganglia?

Answer 71

abnormal motor control alterations to muscle tone abnormal involuntary movements Neurodegenerative diseases - Parkinson's, Huntington's; Wilson's disease (heptolenticular degeneration)

Question 72

What causes Parkinson's disease? What are the resulting symptoms?

Answer 72

Degeneration of the pars compacta of the substantia nigra leading to depleted levels of striatal dopamine Resting tremor of the upper limb Progressive akinesia, motor rigidity, flexed posture (in benign essential tremor) and difficulty initiating movements Symptoms can be exacerbated by anxiety and relieved by alcohol. Late stages of Parkinson's - dystonia and chorea (a neurological disorder causes jerky involuntary movements that especially affect the shoulders, hips and face)

Question 73

What causes Wilson's disease? What is another name for Wilson's disease? What are the symptoms/characteristics?

Answer 73

an autosomal recessive disorder of copper metabolism hepatolenticular degeneration ``` leads to progressive dementia, dystonia, cerebellar dysarthria and ataxia characteristic violent (bat's wing) postural tremor ```

Question 74

What causes Huntington's? What are the symptoms/characteristics?

Answer 74

An autosomal dominant inherited degeneration of the neostriatum (caudate and putamen) Causes progressive dystonia, akinesia and dementia Chorea is characteristic - (a neurological disorder causes jerky involuntary movements that especially affect the shoulders, hips and face).

Question 75

what is a thalamotomy? when is it used?

Answer 75

neurosurgically placed lesions in the region of the ventral anterior and ventral lateral nuclei used to alleviate some of the motor symptoms associated with disorders of the basal ganglia (rigidity, tremor at rest, dyskinesias) and cerebellum intention tremor, i.e. to relieve the tremor in multiple sclerosis.

Question 76

What are the components of the limbic system? | cerebral/diencephalic/other

Answer 76

cerebral components cortical areas - limbic lob (cingulate gyrus, dentate gyrus and parahippocampal gyrus) nuclei - hippocampus and amygdaloid body tracts - fornix diencephalic components thalamus - anterior nuclear group hypothalamus - centres concerned with emotions, appetites (thirst/hunger) and related behaviours ``` other components reticular formation (network of interconnected nuclei throughout the brainstem) ```

Question 77

Describe the Papez circuit

Answer 77

information from cortical association areas passes via the cingulate gyrus, cingulum and parahippocampal gyrus to the hippocampus where it is processed the processed information is transferred to the hypothalamus mammillary bodies via the fornix the circuit is completed and feedback to the cortex is sent via mammillothalamic fibres relaying information from the hypothalamus to the anterior nucleus of the thalamus. From there, the thalamus projects fibres to the cingulate gyrus, cingulum and parahippocampal gyrus

Question 78

What is the role of the Papez circuit?

Answer 78

significant role in memory functions | role in expression of emotion

Question 79

What does the word 'hippocampus' mean in Greek?

Answer 79

'hippos' - horse 'kampos' - sea monster --> seahorse the hippocampus is sea horse shaped

Question 80

What is the anterior perforated substance?

Answer 80

a quadrilateral area of grey matter found anterolateral of the optic tract within the basal forebrain

Question 81

What are the septal nuclei?

Answer 81

an area of the brain adjacent to the septum pellucidum and below the rostrum of the corpus callosum consists of 4 nuclei involved in emotional functioning

Question 82

What is the uncus?

Answer 82

the innermost part of the anterior parahippocampal gyrus, part of the medial temporal lobe part of the limbic system and the posterior portion is part of the hippocampus houses the primary olfactory cortex, receiving olfactory fibres from the lateral olfactory stria

Question 83

What is the fornix? What is its function?

Answer 83

commissural fibre of the brain forming an integral part of the limbic system important for the transfer of complex cognitive information between the cerebral hemispheres.

Question 84

What structures does the fornix connect?

Answer 84

hippocampus to the mammillary bodies of the hypothalamus mammillary bodies to the anterior nuclei of the thalamus hippocampus to the septal nuclei and nucleus accumbens

Question 85

What is the cingulum bundle?

Answer 85

a prominent white matter tract that interconnects the frontal, parietal and medial temporal lobes, whilst also linking the subcortical nuclei to the cingulate gyrus

Question 86

What is the function of the hippocampus? What are the divisions of the hippocampus? Why?

Answer 86

emotion and learning essential for long-term memorisation and memory formation, organisation and storage CA1, CA2, CA3 and CA4 (cornu ammonis) each division contains a different cell type and so each has a slightly different function

Question 87

What are the 3 parts of the achicortex?

Answer 87

hippocampus subiculum (continuation of the hippocampus) entorhinal cortex (continuation of the subiculum)

Question 88

Damage to the hippocampus can result in what?

Answer 88

pathological ageing and age-related diseased, i.e. Alzheimer's Studies have found shrinkage of the hippocampus in cases of Alzheimer's disease, leading to amnesia for relatively recent events and an inability to learn new information

Question 89

Describe the limbic circuit for motor expression of emotionality

Answer 89

input from the limbic lobe, amygdala and hippocampus to the caudate and nucleus accumbens of the basal ganglia processing of information can be facilitated or inhibited feedback via output fibres to the thalamus, from there sends axons onto various regions of the cerebrum, including the motor area (pre-central gyrus)

Question 90

Describe the major hippocampal pathway input and output

Answer 90

Input - perforant fibre(s) from the entorhinal cortex Output - alveus-fimbria-fornix pathway fibres project to - septal area, mammillary bodies and anterior nucleus of the thalamus. (*only need to know input and output of pathways)

Question 91

What is the corona radiata?

Answer 91

A pair of white matter tracts seen at the level of the lateral ventricles. inferiorly - these tracts converge as the internal capsule contains ascending and descending fibres that carry much of the neural traffic to and from the cerebrum

Question 92

What is the relation of brain structures to the lateral ventricles?

Answer 92

anterolateral wall of the anterior horn bordered by the caudate nucleus posterolateral wall of the anterior horn bordered by the thalamus lateral to the lateral ventricle (not directly bordering) is the putamen

Question 93

What is the choroid fissure?

Answer 93

a narrow cleft between the thalamus and fornix to which the choroid plexus is attached

Question 94

What is the septum pellucidum?

Answer 94

a thin double membraned structure that separates the anterior horns of the two lateral ventricles

Question 95

What are pes-hippocampi?

Answer 95

the name given to two or three grooves on the expanded head of the hippocampus

Question 96

What might cause a limbic lobe disorder? Why is this? What happens to the patient in this disorder?

Answer 96

alcohol abuse a diet deficient in thiamine leads to capillary haemorrhages in the upper brainstem and limbic structures. the patient falls into confusion and coma known as Wernicke's encephalopathy

Question 97

What is the difference between the extreme and the external capsule?

Answer 97

the extreme capsule is a series of white matter tracts found between the insular cortex and the claustrum the external capsule is a series of white matter tracts found between the claustrum and the putamen of the lentiform nucleus

Question 98

Describe the visual pathway

Answer 98

1. Each visual field is split into a temporal and nasal half 2. When light passes through the lens of the eye, it projects to the opposite side of the retina 3. the optic nerve consists of axons that extends from the retina to the optic chiasm 4. in the optic chiasm axons from the nasal half of the retina cross and project to the opposite side of the brain. axons from the temporal half do not cross. 5. axons continue on in the optic tract to the lateral geniculate nucleus of the thalamus. (collateral branches synapse with the superior colliculi) 6. optic radiation consisting of axons from the thalamus project to the primary visual cortex 7. images from the right side of the visual field project to the left side of the brain, whilst images from the left side of the visual field project to the right side of the brain

Question 99

What cranial nerves can pituitary tumours have an affect on?

Answer 99

``` II - optic III - oculomotor IV - trochlear V1 - ophthalmic trigeminal V2 - maxillary trigeminal VI - abducens ```

Question 100

What can hypothalamic or pituitary tumours cause?

Answer 100

under- or over-production of circulating hormones which cause secondary disorders of: * growth (dwarfish, gigantism and acromegaly) * sexual function (precocious puberty or hypogonadism) * body water control (diabetes insipidus and pathological drinking) * eating (obesity and bulimia) * adrenal cortical control (Cushing's disease and adrenal insufficiency) Bitemporal visual field loss - if tumours of the pituitary gland increase in size to compress the optic nerve or optic chiasm (due to being closely adjacent)

Question 101

Describe the olfactory pathway

Answer 101

1. specialised ciliated nerve cells of the olfactory nerve are found in the olfactory epithelium of the nasal cavity. 2. olfactory nerve axons pass through the cribiform plate of the ethmoid bone 3. these synapse with the olfactory bulb on the inferior surface of the frontal lobe and preliminary processing of olfactory information takes place 4. axons from large mitral cells of the bulb leave in the olfactory tract which passes backwards on the basal surface of the frontal lobe 5. just before reaching the optic chiasm, most olfactory tract fibres are deflected laterally in the lateral olfactory stria 7. these fibres cross to reach the temporal lobe and terminate mainly in the primary olfactory cortex of the uncus on the inferomedial aspect of the temporal lobe and amygdala 8. the anterior part fo the parahippocampal gyrus - the entorhinal area - makes up the olfactory association area

Question 102

What is the pyriform cortex? | What is its function?

Answer 102

The collective cortices of the primary olfactory cortex and the olfactory association cortex responsible for appreciating olfactory stimuli

Question 103

What is Anosmia? What does it result in? What causes it?

Answer 103

damage to the olfactory nerves loss of sense of smell and flavour of food. (elementary aspects of taste - sweet, salty, bitter, sour - are preserved) multiple causes: * frequently follows head trauma or a meningioma (tumour of the meninges) that invades the olfactory nerves * Alzheimer's - appreceptive agnosia where atrophy of the uncus leaves patients able to detect the presence of odours but unable to identify or discriminate them * Semantic dementia - associative agnosia where atrophy of the amygdala and inferior temporal neocortex occurs resulting in patients able to detect odours, match and discriminate them but unable to accurately name/describe/identify them

Question 104

What is tunnel vision? | What can cause it?

Answer 104

loss of peripheral vision | pituitary tumour due to close relationship of pituitary gland and optic nerve

Question 105

Why are eating carrots good for your eyes?

Answer 105

carrots contain precursors for vitamin A. deficiency in vitamin A is linked to blindness, cataracts and macular degeneration. carrots also contain lutein an important anti-oxidant that is linked to increasing pigment density in the macular. higher pigment density is linked to decreased risk of macular degeneration.