Week 2 Flashcards

Question

Golgi tendon organ- detection of muscle tension

Answer 1

Located at the junction of muscle and tendon Innervation by group 1b sensory afferents Position in series with muscle Sensitive to tension generated by contraction (Cf spindle in parallel, sensitive to length)

Answer 2

Lemniscal pathway (dorsal columns) Large sensory Ab fibres Touch vibration, two point discrimination, proprioception Spinothalamic pathway (anterolateral tracts) -small sensory Adelta and C fibres -pain and temperature (some touch)

Answer 3

It’s the largest organ of the body It forms the body’s universal external envelope It has an average surface area of 2 SQ M It’s a major sensory apparatus of the body Both low and high threshold afferents It’s sensory territories are organised Dermatomal slices

Answer 4

Muscles are richly supplied with millions of tiny muscle sense organs Proprioceptive organs Proprioception is a special sense in its own right It’s defined as the sense of awareness of body position in 3 dimensional space Proprioceptive afferents: provide for sensory awareness of limb position in 360 space of the body Muscle sense organs include -muscle spindles -Golgi tendons organ -joint receptors General sensory afferents of muscles -free nerve endings: general sensation such as pain and temperature

Answer 5

Diaphragm C3-5 Biceps C5-6 Wrist C8-T1 Nipple T4 Umbilicus T10 Hip flexion L1-2 Knee jerk (or quadriceps contraction) L3-4 Knee flexion S1 Great toe L5 (foot Dorsiflexion) Foot plantar flexion S1-2 Bladder L1-2 or S2-4 Anal sphincteric tone S2-4 (onuffs nucleus)

Answer 6

The brain has full sensory representation of the bodys surfaces (or skin) and muscles The left side of the bodys sensations are represented in the right brain The bodys surfaces map on the brain is not isometric with body surfaces from which signals arise

Answer 7

They are fibre tracts of the spinal sensory system information is conveyed to the brain They are divisible into 3 categories Lateral spinothalamic tract Dorsal column Dorsal spinocerebellar tracts Conscious sensation: processed in the sensory cortex, dorsal columns, spinothalamic tract Non conscious sensation: processed in the cerebellum, clarke’s column (from dorsal column), DSCT, VSCT

Answer 8

Sensory signals that are detected by the body are conveyed to the brain via a longitudinal sequence of three separate stages The last stage gives rise to a projection to the sensory cortex of the cerebrum - it can also give rise to awareness of sensation by the brain -sensation is said to be conscious sensation if we are directly aware of the information Sensation is said to be unconscious if the signals do not reach the cerebrum Sensations giving rise to conscious sensation are conveyed differently from those not giving rise to conscious sensation

Answer 9

On reaching the spinal cord a primary sensory neurone then divides: -1 axonal process terminates in the dorsal horn of its respective spinal segment -another axonal process is sent to the dorsal horn of the spinal segment above -another axonal process is sent to the dorsal horn of spinal segment below - the axonal segments travelling to the spinal segments below and above travel in the posterolateral tract of lissauer -the axon intended for its respective spinal neural segment then enters the respective dorsal horn -it then terminates in the dorsal horn -the lamina upon which it terminates is determined by the modality it represents -pain fibres terminate in laminae I and II of the dorsal horn -laminae III and IV are known as nucleus proprius -the in coming axon terminates on a cell body of a secondary sensory neurone (in nucleus proprius)

Answer 10

The secondary sensory neurone then sends its axon as follows: -towards the midline -towards the central canal of the spinal cord -it then divides under the central canal -it crosses the midline to emerge on the opposite side of the The axon of the secondary sensory neurone then travels into the white matter of the opposite side It joins the lateral funiculus It joins the fibres of the lateral spinothalamic tract The spinothalamic tract is in the lateral funiculus Fibres of the spinothalamic tract travel to the thalamus (opposite side to that from which sensory signals rose)

Answer 11

Axons of second order sensory neurones crossing the midline comprise the “spinal decussation” Spinal decussation fibres are known as anterior commissures They are also known as spinal Arcuate fibres Spinal sensory decussation occurs for all 31 neural levels of spinal cord

Answer 12

Secondary sensory neurones of the spinothalamic tract ascend the medulla, pons, midbrain and end in the thalamus In particular they travel to the ventral posterolateral VPL nucleus of the thalamus In the VPL, spinothalamic tract fibres terminate on 3rd order sensory neurones

Answer 13

Axons of 3rd order sensory neurones of the VPL ascend further to terminate in the post central gyrus of the cerebral cortex Axons of 3rd order sensory neurones of the VPL travel via the internal capsule

Answer 14

The spinothalamic tract is somatotopically organised throughout its full extent This means that the spatial mapping of the bodys surface is preserved within the tract Fibres arising from the lowest part of the body ascend dorsolaterally within the spinothalamic tract Fibres arising from cervical cord ascend ventromedially

Answer 15

Syringomyelia- fluid filled cyst (syrinx) forms in spinal cord Brown sequard syndrome- neurologic syndrome from hemisection of the spinal cord

Answer 16

The cerebral cortex represent that highest centre for processing of sensory information and for commanding of motor commands Sensory info from the body is first represented in the cerebral cortex in the primary sensory cortex Voluntary motor commands of muscles are issued through the motor cortex The primary motor cortex is separated from the primary sensory cortex by the central sulcus of the cerebral cortex

Answer 17

Normally movements of skeletal/somatic muscles are initiated voluntarily Most movements originate in the cerebral motor cortex Somatic muscles of the body are controlled by dedicated neurones of the “motor strip” of the frontal cortex Neurones of the “motor strip” are grouped according to skeletal muscles they command The motor map of cortical neurones can be reconstructed into a motor homonculus

Answer 18

The brain commands muscles to either: -rest or contract -levels of contraction vary depending on the requirements of the body -resting muscle tone: maintenance of posture (minimal contraction) -displacement of joints: movements (large forces required) The brains motor commands of muscles of the body are decussated Irrespective of site of origin of motor commands, skeletal muscles of the left side of the body are commanded to move or rest by the right cerebral motor cortex vice versa

Answer 19

The brain commands muscles through descending motor tracts Descending tracts are formed from axons of neurones with cell bodies in motor nucleus of the brain Cortical descending tracts originates in cerebral cortex: primary motor cortex (in pre central gyrus) Other in subcortical areas- non cortical descending tracts -midbrain, brainstem, pons, medulla

Answer 20

The brain gives its only commands either to glands, smooth muscle or skeletal muscle The brains outputs are conveyed through a group of neurones collectively known as efferents Motorneurones are divisible into two broad categories: motorneurones with cell bodies in spinal cord (cerebral cortex, diencephalon, brainstem)

Answer 21

Motorneurones with cell bodies in the brain (upper motorneurones) are in hierarchically higher centres of the CNS (eg cerebral cortex or brainstem) Lower motorneurones with cell bodies in the spinal cord or cranial nerve motor nuclei (lower motorneurones) are in hierarchically lower centres of the CNS (eg facial nerve motor nucleus or Rexed lamina IX of the spinal cord)

Answer 22

An upper motor neurone is that motor efferent whose entire axon resides within the central nervous system A lower motor neurone is that motor efferent whose axon travels in peripheral nerves

Answer 23

Upper motor neurones with cell bodies in the cerebral cortex are called cortical efferents Upper motorneurones with cell bodies in subcortical brain areas such as the brainstem are called brainstem efferents or bulbar efferents

Answer 24

These are also called pyramidal upper motorneurones They comprise what is known as pyramidal system of the brain (motor) Lesions of the pyramidal motor system impair movements in a characteristic way that distinguishes this particular system from

Answer 25

Extrapyramidal upper motorneurones Extarpyramidal motor system of the brain Lesions of the extrapyramidal motor system impair movements in a characteristic way that is different from that arising from injuries/defects arising from dysfunction of the pyramidal system

Answer 26

Axons of upper motor neurones travelling in the spinal cord are collectively known as descending fibre tracts Descending tracts are found either anterior (ventral) or lateral funiculus of the spinal cord Ascending and descending tracts are mixed within the ventral or lateral funiculi