Part 1 of 6 Anatomy Flashcards

1
Q

Describe the outflow of the parasympathetic nervous system.

A

See F375 - Parasympathetic NS

· No PSNS in cervical , thoracic, lumbar regions, only in brain and sacral area

  • Cranio-sacro output:

o Cranial nerves with a PSNS component = 3, 7, 9, 10 → head, neck and thoracic

o Sacral nerves with PSNS component = S2, S3, S4 → affect pelvic organs

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2
Q

Describe the outflow of the sympathetic NS.

A

See F376 - Sympathetic NS outflow

  • Thoracic-lumbar output

o T1 – L2 → innervation of head and neck

o No cervical or cranial or sacral

· SNS nerves next to spinal chord – form a sympathetic chain (autonomic ganglia) → synapse with post-synaptic ganglia of SNS

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3
Q

Describe the structural and functional divisions of the nervous system.

A

See F372 - Structural and functional divisions of the nervous sys. (MM3)

Functional Division of the NS

  • Somatic NS = external environment
  • Autonomic NS = internal environment
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4
Q

Explain what the grey and white matter in the central nervous system consists of.

A

Arrangement of Central Nervous System

  • Made of neuronal and non-neuronal (glial) cells, which make grey and white matter

o Grey: Cell bodies

§ Spinal grey horns

§ Cortex of cerebrum

§ Basal ganglia

§ Nuclei

o White: Myelinated neuronal fibres (axons & dendrites)

§ Association fibres

§ Commissural fibres

§ Projection fibres

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5
Q

Explain the types of white matter.

A
  • Types of white matter:

o Association fibres: interconnect neural areas of cortex within single hemisphere

o Commissures: connect hemispheres, e.g. corpus callosum, thick band of white matter – connects cerebral hemispheres

o Projection fibres: link cortex to diencephalon, brain stem, cerebellum and spinal chord

(F377 - Types of white matter)

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6
Q

Identify and be able to pinpoint these structures:

  • Corpus callosum
  • Corona radiata
  • Basal nuclei:
    • Caudate
    • Putamen
    • Globus pallidus
  • Internal capsule
  • Projection fibres
  • Decussation of pyramids
  • Longitudinal fissure
  • Lateral ventricle
  • Fornix
  • Third ventricle
  • Thalamus
  • Pons
  • Medulla oblongata
A

See the rest of F377 - Types of white matter (MM4-5)

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7
Q

Describe structural divisions of the brain, detailing the components of the forebrain, midbrain and hindbrain.

A

See F378 - Divisions of the brain.

Extra Information

· Brain has 3 regions: forebrain, midbrain, hindbrain → formed during neurulation from dilations of neural tube – all 3 components have a central cavity

o Hindbrain = cerebellum, pons, medulla

o Forebrain = telencephalon and diencepalon

§ Majority of diencephalon is thalamus, lower part is hypothalamus

§ Hypothalamus located just above brain stem and mid-brain

§ Diencephalon is attached to midbrain

· Penduncles attach the cerebral hemispheres to the brain stem (made of white matter)

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8
Q

Be able to identify and understand the basic function of these structures:

  • Cerebrum
  • Cerebellum
  • Diencephalon
    • Hypothalamus
  • Mesencephalon
  • Pons
  • Medulla oblongata
  • Cerebellum
A

See F378 - Divisions of the brain.

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9
Q

Describe the basic structure of the diencephalon and the functions that it controls.

A

Diencephalon

  • Thalamus, hypothalamus, epithalamus, retina

See F379 - Diencephalon components and functions

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10
Q

The cerebral hemispheres are marked with folds. What are the names of these fissures?

A

These fissures are called sulci and gyri. They develop due to brain development in skull – not enough space, brain folds over itself.

Sulci (sulcus) = Depressions

Gyri (gyrus) = Elevations

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11
Q

Name and identify the major:

  • Fissures
  • Gyri
  • Sulci
A

Fissures

  • Transverse fissure - separates the cerebellum from the hemispheres
  • Longitudinal fissure - separates the 2 hemispheres

Sulci + Gyri

  • Calcarine sulcus = primary visual area
  • Major sulcus (aka central sulcus) [blue line], separates pre-central gyrus and post-central gyrus –> also is the border for parietal and frontal lobes
  • Parieto-occipital sulcus [green line] –> also is the border for the parietal and frontal lobes
  • Lateral sulcus (aka Sylvian fissure) [yellow line] –> also is the border for frontal and temporal lobes

Also other major sulci and gyri are shown in the figure indicated.

See F380

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12
Q

Name the lobes of the brain and briefly describe the function of each.

A

See F381 - Brain lobes and functions.

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13
Q

Describe the ventricular system of the brain.

A

Ventricular System of the Brain

See F382 - ventricular system of brain

  • Lateral ventricle:

o Frontal lobe – anterior horn of lateral ventricle

o Parietal lobe – body of lateral ventricle

o Occipital lobe – posterior horn of lateral ventricle

  • Third ventricle

o Ventricle of diencephalon – located between the 2 thalamus

o Open to the lateral ventricle via the interventricular foramen

  • Cerebral aqueduct

o Joins the third ventricle to the fourth ventricle

  • Fourth ventricle

o Continues from the aqueduct through the spinal chord into a structure called the central canal

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14
Q

Be able to point out these major structures in the brain stem:

  • Cerebral peduncles
  • Cerebellar peduncles
    • Superior (midbrain)
    • Middle (pons)
    • Inferior (medulla)
A

See F383 - Cerebral and cerebellar peduncles.

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15
Q

Understand and memorise this picture of brain stem gross anatomy. Can you sketch the structure?

A

See F384 - Brain stem gross anatomy

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16
Q

Describe the major features of the spinal cord.

A

See F385 - Spinal cord major features.

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17
Q

How many pairs of spinal nerves are there?

Are spinal nerves sensory or motor?

A
  1. 31 pairs of spinal nerves
  2. Mixed = both sensory and motor
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18
Q

Describe the major features of a transverse section of the spinal cord.

A

See F386 - transverse section spinal cord.

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19
Q

Briefly describe the pathways which make up the sensory pathways.

A

Sensory pathways can be divided into conscious and unconscious sensation.

Conscious Sensation: (Clinically most important)

  • These concious pathways transmit impulses from thalamus to sensory cortex for conscious interpretation
  1. Dorsal column-medial lemniscus pathway (DCML)
    • FAsciculus cuneatus
    • Fasciculus gracilis
    • Medial lemniscus
  2. Antero-Lateral System (ALS)
    • Lateral spinothalamic tract
    • Anterior/Ventral spinothalamic tract

Unconscious Sensation:

  • This pathway stretches to cerebellum
  1. Spino-cerebellar tracts
    • Dorsal spinocerebellar tract
    • Cuneocerebellar tract
    • Ventral spinocerebellar tract

(See MM6)

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20
Q

Describe the function of the Dorsal column-medial lemniscus pathway (DCML).

A

DCML

  • Transmit mechanical sensations into sensory info for:
    • Discriminative touch – fine touch, pressure, movement detection
    • Proprioception
    • Vibration

(MM 7)

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21
Q

Describe the functions of the Antero-Lateral System (ALS).

A

2 Components (Key role in tissue protection)

  • Lateral spinothalamic tract:
    • Fast pain pathway - immediate awareness and localization of pain
    • ‘Clinically important pathway’ –> pin prick test
    • Temperature
    • Crude touch
  • Anterior spinothalamic tract:
    • Backup for crude touch

(MM 8)

22
Q

What is the function of the spino-cerebellar tracts?

A

Unconcious Proprioception

Conveys information about muscle or tendon stretch to the cerebellum, which uses this information to co-ordinate skeletal muscle activity.

(MM10)

23
Q

Describe in detail the general structure of the sensory pathway, detailing the neurons involved, their locations and synapses and roles.

A

1. First order neurons

  • Cell bodies in ganglion (dorsal root ganglion or sensory ganglia of sensory cranial nerve)
  • Conduct from: cutaneous receptors of the skin and from proprioceptors to the spinal cord or brain stem
  • Spinal nerves = body
  • Cranial nerves = face + neck

Synapse 1-2 = Spinal cord or brainstem

_ 2. Second-order neurons_

  • Cell bodies in dorsal horn of spinal cord or in medullary nuclei
  • Conduct from: spinal cord or brainstem to thalamus or cerebellum

Synapse 2-3 = Thalamus or cerebellum

3. Third-order neurons

  • Cell bodies in thalamus
  • Conducts impulses to somatosensory cortex of cerebrum (NB: there are no 3rd-order neurons in the crebellum)

(MM 9)

24
Q

Describe the positioning of the 3 pathways of the sensory system in the spinal cord.

A
  1. Dorsal column-medial lemniscal pathway
  • Formed by paired tracts of dorsal white column in spinal cord.
    1. Fasciculus cuneatus
    2. Fasiculus gracilis
  • The two tracts then transfer the information to the nucleus cuneatus and nucleus gracilis respectively
  • The paired tract that continues from there in the medulla to the thalamus is the medial lemniscus
  1. Anterolateral pathways
  • Located in the ventral (anteiror) and lateral white columns of the spinal cord
  • Formed by:
    • Lateral spinothalamic tract
    • Ventral spinothalamic tract
  1. Spinocerebellar tracts
    * Ventral (anterior) and dorsal (posterior) spinocerebellar tracts

(See F387 - Locations of sensory/motor tracts spinal cord)

25
Q

Describe the basic structure of a sensory pathway.

A
  • Sensory pathways are ascending pathways which conduct sensory impulses upwards through chains of 3 successive neurons
26
Q

One of the roles of the dorsal column medial lemniscus pathway is proprioception. List the mechanisms involved in proprioception within the DCML.

A

Proprioception

When a joint moves –> Tension/length in the muscle/soft tissue changes –> proprioceptors start firing –> sense of position of parts of body

  1. Muscle spindle – stretching/length, (located in skeletal muscles) + Golgi tendon organs – tension, (located in tendons)
  2. Joint kinesthetic receptors - stretch, (located in joint capules of synovial joints)

(MM 11)

27
Q

Explain how muscle spindles work in proprioception.

A
  • Muscle spindles are fusiform proprioceptors found in perimysium of skeletal muscles
  • Composed of a bundle of intrafusal fibres which are encased in a connective tissue capsule
  • Detect muscle stretch and initiate a reflex which resist the stretch.

(MM 12)

28
Q

Explain how Golgi tendon organs work in proprioception.

A
  • Golgi tendon organs are proprioceptors located in tendons cloes tot he skeletal muscle insertion.
  • Made of small bundles of tendon fibres in a layered capsule with sensory terminals coiling between and around the fibres
  • When tendon fibres stretched during muscle contraction, the nerve endings are activated by compression - activation of Golgi tendon organs inhibit contraction of the muscle, causing it to relax.
29
Q

Explain how joint kinesthaetic receptors work in proprioception.

A
  • Joint kinaesthetic receptors are proprioceptors taht monitor stretch in articular capsules around synovial joints
  • 4 receptor types at least, e.g. Pacinian corpuscles, free nerve endings, Ruffini endings, Golgitendon organ -like receptors

Eg. Close eyes, flex fingers, can feel which joints are moving –> joint kinaesthetic receptors working

30
Q

Describe in detail the path of the DCML.

A
  1. S1 ascends from spinal cord up to the medulla in the brainstem.
    • If below T7: ascend ipsilaterally and medially in gracile fasciculus and synapses with S2 in gracile nucleus in medulla
    • If above T7: ascend ipsilaterally and laterally in cuneate fasciculus and ends by synapsing with S2 in cuneate nucleus in medulla
  2. S2 decussates to opposite side of medulla in upper medulla and ascends as medial lemniscus to contralateral thalamus
  3. S2-S3 synapse occurs in ventral posterolateral nucleus of thalamus
  4. S3 (now thalamocortical) go to sensory cortex by passing through the internal capsule (posterior limb) to the corona radiata.

(See F388 - Dorsal column medial lemniscus pathway tracing.)

31
Q

Describe in detail the path of the ALS.

A

Recall - 2 major tracts of the ALS

  1. Laterospinothalamic tract
  2. Anterior/ventral spinothalamic tract

Basic Pathway

  1. S1 starts from ree nerve endings (Nociceptors) in somatic tissues
  2. Synapse with the 2nd neuron within the spinal cord, dorsal horn
  3. 2nd neuron crosses to the opposite side via anterior white commissure & occupies the anterior part of the lateral white column
  4. 2nd order neurons ascend to thalamus and synapse with 3rd order neuron in ventral postero-lateral (VPL) nucleus of thalamus
  5. 3rd order neuron gets into posterior limb of the internal capsue –> corona radiata –> sensory cortex

(F389 - Anterolateral system pathway tracing)

32
Q

In the pathway of the ALS, the second order neurons have multiple destinations to choose from.

List these and explain their function in relation to pain transmission.

A

The second order neurons of the ALS can go to:

  • Thalamus –> spinothalamic tract (STT)
  • Midbrain –> spinomesencephalic tract (SMT)
  • Colliculi –> Spinotectal tracts (STcT)
  • Reticular formation –> Spinoreticular tract (SRT)
  • Hypothalamus –> spinohypothalamic tract (SHT)

(See F390 Anterior tracts of the ALS & 2nd order neuron pathways)

Roles in Pain Transmission

  • STT - (MOST IMPORTANT)
    • Discriminative aspects of pain
    • Localization, intensity
    • Consists of Aδ fibres
  • SRT – Arousal/modulation of pain via descending analgesic system
  • SMT – modulation of pain via descending analgesic system
  • STcT – turning the upper body towards stimulus
  • SHT – Pain associated visceral/endocrine reflexes

(See F389 - Anterolateral system pathway tracing)

33
Q

Describe the descending analgesic system of the CNS.

A

Role:

  • When pain signals occur in the body, the CNS have mechanisms in place to modulate the pain, these form the descending analgesic system

Mechanism:

  • Pain signals sent to sensory cortex –> signals passed through periaqueductal grey matter to hypothalamus, which then sends signals down through the midbrain then to either of these bodies in the medulla:
    • Locus ceruleus –> descending norepinephrine pathway
    • Nucleus raphe magnus –> descending serotonin pathway, descending opioid pathway

(See F391 - Descending analgesic system), MM 14 is an amazing summary.

34
Q

Name the 3 main spinocerebellar tracts and briefly describe their functions.

A
  1. Dorsal spinocerebellar tract – Mainly proprioceptive input to cerebellum (Upto C8 level).
  2. Cuneocerebellar tract - Mainly proprioceptive input to cerebellum (above C8 level).
  3. Ventral spinocerebellar tract – Mainly info regarding spinal interneuron activity to cerebellum.

See MM 15

35
Q

Describe the pathway of the dorsal and ventral spinocerebellar tracts.

A

Dorsal Spinocerebellar Tract

  • 1st neuron synapse with 2nd in dorsal nucleus in posterior gray horn.
  • 2nd neuron ascend towards medulla and enters the cerebellum through the inferior cerebellar peduncle.

Ventral Spinocerebellar Tract

  • 1st neuron synapse with 2nd in dorsal nucleus in posterior gray horn and cross to the opposite side.
  • 2nd neuron ascend towards midbrain and cross back again before entering the cerebellum through the superior cerebellar peduncle.

Both pathways are connected to the interposed nucleus of spinocerebellum.

(See F392 - Dorsal and ventral spinocerebellar tracts)

36
Q

Explain the difference between crude touch and fine touch and how they are each transmitted.

What tests might you use to test the function of them?

A
  • Crude touch sensation is not accurately localisable – transmitted mainly through ALS (Free nerve endings).
  • Fine touch is accurately localisable – transmitted mainly through DCML (Meissener’s).

Testing it: Touch with a whisk of cotton wool.

  • Can you feel? - Checking Crude touch - ALS
  • Can you locate? - DCML
37
Q

What is discriminative touch?

A
  • Discriminative touch is a complex sensation which uses primary sensations such as fine touch (Meissener’s corpuscles), pressure (Pacinian corpsucle),movement detection (Meissener’s corpuscles). This allows
    • Accurate localisation of touch
    • Differentiate between 2 very close & simultaneously touched points with precision. (2 point discrimination)
    • Acts with other primary sensations (proprioception/pressure) aids recognition of: surface characteristics (texture), objects by touch (Stereognosis) and graphaesthesia.

See MM 16

38
Q

Describe how you might test the function of the sensory pathways of the nervous system.

Also explain how you would interpret the tests.

A

Key Points to Remember in Testing

  • 2 main systems for testing conscious sensation, DCML and ALS, 2 main levels - thalamic and suprathalamic (cortical lesions)
  • Think about the roles of these systems and what tests you could use.

Primary Modalities (Thalamic Function)

  • DCML
    • Vibration – Tuning fork
    • Proprioception – Romberg sign/Joint position
    • Crude Touch - Touch with Cotton wool – Where?
    • Discriminative touch (see below)
  • Spinothalamic
    • Pain – Pin prick test – You feel sharp or dull ? Where?
    • Temperature
    • Crude Touch - Touch with cotton wool – Can you feel?

Interpretation: Thalamic Function

At the level of thalamus - basic sensory modalities:

  • Can feel pain
  • Can feel vibration very well (no deep processing) – hardly impaired in suprathalamic lesions.

Further Testing (Suprathalamic)

  • Test for cortical function – If primary modalities are intact (or the deficit is only mild)
    • 2 point discrimination
    • Stereognosis
    • Graphaesthesia

Interpretation: Suprathalamic Function

  • Complex processing occurs at supra thalamic levels.
39
Q

What part of the sensory system might be affected if sensation of these are abnormal?

  1. Pain
  2. Temperature
  3. Touch
  4. Vibration
  5. Proprioception
A

See F393 - Sensory modalities and sensory system correlation

40
Q

Name 7 types of receptors you may see in the sensory system and what they each sense.

A

(See F394 - Sensory receptors and sensations.)

41
Q

Name the cranial nerves and also whether each of them are motor or sensory.

A
  • Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Accessory, Hypoglossal

On October ‘ours, through Tuscan arbours, fine vineyards gleam veiling arched hills.

  • Some Say Marry Money But My Brother Says Big Brains Matter More

Side-by-Side

  • See F401 - Cranial nerves sensory or motor, function and location. Very useful table.
42
Q

Explain the structure of the nerve motor pathway.

A

Nerve Motor Pathways

  • 2 neuron system:
    • LMN = joins to the gland, muscle or organ it is innervating and synapses with UMN
    • UMN = from brain synapses with LMN

Lower Motor Neurons

  • The cranial and spinal motor nerves contain the lower motor neurons of nerve motor pathways
    • Cranial nerves = head & neck (relatively few)
    • Spinal = trunk & limbs
  • Cranial nerves are found in the brain stem while spinal nerves are found in the spinal cord

Upper Motor Neurons

  • Control LMN and hence the item LMN controls, e.g. muscle
  • UMN links commands from brain motor centres (cortical and subcortical) to LMN
43
Q

Describe how lower motor neurons are arranged in the:

  1. Spinal cord
  2. Brain stem
A

Spinal Cord LMNs (Spinal Nerves!)

  • Limb LMNs: laterally
  • Trunk LMNs: medially
  • Flexor Muscle LMNs: posteriorly
  • Extensor Muscles LMNs: anteriorly

Look at F399 - lower motor neuron location in spinal cord. A midline lesion would initially affect trunk muscles. Can you tell why?

Brain Stem LMNs (Cranial Nerves!)

  • See F400 Lower motor neuron location in the brain stem
44
Q

How are lower motor neurons controlled in the body?

A

Lower motor neurons are controlled either directly** or **indirectly.

Directly

  1. Spinal cord level (reflexes/ pattern generators)
  2. Brainstem level (posture/tone/ pattern generators)
  3. Cerebral cortex level (voluntary, skilled movements)

Indirectly

  1. Basal ganglia (planning, supervision, co-ordination)
  2. Cerebellum

Supraspinal centres control LMN via UMN. (Supraspinal centres refer to the controls which are located above the spinal cord, e.g. primary motor cortex, brain-stem, etc.)

45
Q

Explain where upper motor neurons can originate from before synapsing with LMNs.

A
  • Upper motor neurons are located in any of the supraspinal centres
    • Primary motor cortex for the pyramidal pathways
    • Brainstem nuclei for the non-pyramidal pathways
  • Hence multiple UMNs help to create the motor pathways
46
Q

Describe the tracts which the motor system is composed of.

A

Motor System

  • Categorised based on neuronal pathway organisation, origin of neurons and which areas are innervated.
  • 2 main divisions:
    1. Pyramidal tracts
    2. Non-pyramidal tracts

Pyramidal Tracts

  • aka ‘Direct Activation Pathway’, composed of:
    1. Corticospinal
  • Lateral corticospinal tract
  • Anterior corticospinal tract
  1. Corticobulbar

Non-pyramidal Tracts

  • aka ‘Extrapyramidal System’ or ‘Indirect Activation Pathway’
  1. Red nucleus –> rubrospinal
  2. Vestibular nucleus –> vestibulospinal
  3. Reticular nucleus –> reticulospinal
  4. Tectal nucleus –> tectospinal

See F402 - Motor system – pyramidal and non-pyramidal tracts org.

47
Q

Compare the pyramidal and non-pyramidal divisions of the motor system.

A

See F403 - Pyramidal & Non-pyramidal tracts Comparison table

48
Q

Explain where the motor pathways are located in the spinal cord.

A

Motor Pathway Location

Motor pathways in the spinal cord are grouped into 2 major divisions. These two divisions also have different functions, which will be discussed later.

[P] = pyramidal tract, [NP] = non-pyramidal

  1. Medial Group
  • Anterior corticospinal tract [P]
  • Tectospinal tract [NP]
  • Vestibulospinal tract [NP]
  • Reticulospinal tracts [NP]
    • Pontoreticulospinal tract (medial)
    • Medullary reticulospinal tract (lateral)
  1. Lateral Group
  • Lateral corticospinal tract [P]
  • Rubrospinal tract [NP]

See F404 - Location of motor pathways in the spinal cord.

49
Q

What is the function of the medial group of motor pathways?

A

Main Functionof Medial Group of Motor Pathways

  • Main functions: Proximal (trunk, girdle) muscle control –> posture, not fine movements

i) Vestibulospinal tract: Balance, Posture, Muscle tone
ii) Reticulospinal tract: Respiration, Muscle tone
iii) Tectospinal tract: Reflexes
iv) Anterior corticospinal tract: Voluntary control of trunk

  • Some of these pathways contribute to bilateral innervation of the trunk, so that even a hemiplegic patient can sit upright. Same case with unilateral lesions.
50
Q

What is the function of the lateral group of motor pathways?

A

Lateral Group Motor Pathways

  • Controls distal limb movements, important for voluntary skilled movements
  • Lateral group innervates contralateral distal muscles (limb)