Lesson 8 - Ascending Pathways

Question 1

What are the 2 types of senses?

Answer 1

1. Special 2. General

Question 2

——- senses are spread throughout the body

Answer 2

General

Question 3

———— senses are localised by their respective sensory organ

Answer 3

special

Question 4

The 5 special senses carried by cranial nerves

Olfaction - CN ?
Vision - CN ?
Taste - CN ?, ?
Hearing - CN ?
Vestibular - CN ?

Answer 4

Olfaction - CN I
Vision - CN II
Taste - CN VII, IX
Hearing - CN VII
Vestibular - CN VIII

Question 5

Define interoception

Answer 5

the sense of the physiological condition of the body

pain, temperature, touch pressure of the viscera

Question 6

Define exteroception

Answer 6

Any formal sensation that results from stimuli located outside the body and is detected by exteroceptors

Pain, temp, touch pressure of the external world

Question 7

Define proprioception

Answer 7

Position sense from joints, tendons, ligaments

Question 8

List what the following receptors do/monitor:

Nociceptors: ?
Thermoreceptors: ?
Mechanoreceptors: ?
Chemoreceptors: ?
Baroreceptors: ?

Answer 8

Nociceptors: monitor tissue damage

Thermoreceptors: monitor temperature, found in skin, muscle liver and hypothalamus

Mechanoreceptors: monitor contact and pressure, found mostly in the skin

Chemoreceptors: monitor chemical composition of body fluids (02, C02, pH etc.)

Baroreceptors: subset of mechanoreceptors, monitor changes in pressure of tubular organs (vessels, ureters, bowel)

Question 9

Function of the frontal lobe of the cerebral cortex?

Answer 9

Initiation and control of voluntary movement as well as expressive language function.

Higher function of mood, personality, judgement, motivation, executive functions.

Question 10

Function of the parietal lobe of the cerebral cortex?

Answer 10

perception and discrimination of somatic sensory stimuli. Also involved in integrating visual and somatic sensory information.

Question 11

Function of the Temporal lobe of the cerebral cortex?

Answer 11

Auditory perception and discrimination and receptive language function. Olfaction as well as learning and memory function in the medial region (those areas of allocortex).

Question 12

Function of the occipital lobe of the cerebral cortex?

Answer 12

• Visual perception and recognition
• Insular - buried in the lateral sulcus. It receives taste afferent information. It is associated with somatic sensory and limbic function and influences autonomic (visceral) functions

Question 13

Motor areas of the cerebral cortex:

• —————— gyrus of frontal lobe
• Primary motor cortex directs ———- movement

Answer 13

Precentral
voluntary

Question 14

Sensory areas of the cerebral cortex

• ———— ————- of parietal lobe
• Primary sensory cortex: receives s——— sensory information (touch, pressure, pain, vibration, taste, and temperature)

Answer 14

• Postcentral gyrus
• Somatic

Question 15

Each spinal nerve carries sensory innervation for a part of the body surface. The area of skin that is innervated is known as a ———–

Answer 15

dermatome

Question 16

What is a dermatome?

Answer 16

A dermatome is an area of skin supplied by a particular spinal nerve (PNS)

Question 17

Each dermatome corresponds to the entry or exit point of ———-(motor) and ——— (sensory) rootlets.

Answer 17

ventral
dorsal

Question 18

31 dermatomes = 31 ———– ———s

Answer 18

spinal segments

Question 19

If a spinal nerve is cut, ———- is lost in that dermatome

Answer 19

sensation

Question 20

Somatosensory axon are relayed to the post central gyrus (primary somatosensory cortex)
- Propioception
- Interoception
- Exteroception

By 3 order of neurons:
1 PNS :————- ———– ——-
2 CNS: ——– matter of spinal cord/brainstem
3 CNS: —————– ————- nucleus (VPN) of Thalamus

Answer 20

Dorsal root ganglia
Grey
Ventral Posteromdedial Nucleus

Question 21

First-order neuron (primary afferent neuron):

The first neuron enters the spinal cord through the ——— ———– of a spinal nerve and its cell body lies in the ——— ——— ganglion.

The central process may ———– extensively and make synaptic connections that mediate spinal reflexes and intersegmental coordination.

The main fiber remains on the ———- side of the cord and terminates in ——— contact with the 2nd neuron either in the spinal gray matter or in the medulla oblongata of the brainstem depending on the modality.

Answer 21

dorsal root x2

collateralize

ipsilateral
synaptic

Question 22

Second-order neuron (second neuron):

The second neuron has its cell body in the cord or ———- ———–

Its Axon crosses over (————s) to the opposite side of the CNS and ascends to the ——– where it terminates upon the third neuron.

Answer 22

medulla oblongata.

decussates
thalamus

Question 23

Third-order neuron / third neuron:

The third neuron has its cell body in the ———-
Its Axon passes to the somatosensory cortex in the parietal lobe of the ———— cerebral hemisphere.

NOTE: TWO MAIN TRACTS IN THE SPINAL CORD FIT INTO THIS PATTERN –
1. THE DORSAL / POSTERIOR ———-S
2. THE S———— TRACTS

Answer 23

thalamus
ipsilateral

COLUMNS
SPINOTHALAMIC

Question 24

Dorsal/Posterior columns - Medial lemniscus pathway:

Consists of 2 parts:

1. The dorsal (posterior) column, which runs from the spinal cord to the ———
2. The ———- ——— pathway, which runs as a continuation of the dorsal column, from the medulla to the cortex.

Answer 24

medulla
medial lemniscus

Question 25

Dorsal/Posterior columns; spinal cord to medulla: The dorsal columns are located between the ----------- ---------- -------- and the ------------- ---------- 2 tracts are recognized; the ------- ----------- situated medially and the fasciculus cuneatus situated laterally. The tracts carry impulses concerned with proprioception and discriminative touch. The dorsal columns contain the axons of primary afferent neurons that have entered the core through the ------- --------- of spinal nerves. The -------- ------------ consists of fibres that join the cord at sacral lumbar and lower thoracic levels and thus includes those from the lower limb. Fibres of the ----------- --------- enter via the upper thoracic and cervical dorsal roots and thus involve those from the upper limb. Since the dorsal columns contain primary afferent neurons they carry information relating to the ---------l side of the body.

Answer 25

dorsal median sulcus and the dorsal horn. fasciculus gracilis dorsal root fasciculus gracilis fasciculus cuneatus ipsilateral

Question 26

Medial lemniscus pathway; medulla to cortex: Fibres ascend without interruption to the medulla oblongata where they terminate upon 2nd order neurons, the cell bodies of which are located in the nucleus ----------and nucleus ----------. The axons of the 2nd order neurons decussate in the medulla as internal --------- ------s and thereafter ascend through the brain stem as the medial lemniscus. The medial lemniscus terminates in the ventral posterior nucleus of the thalamus upon 3rd order ----------- -----------s. These in turn project to the somatosensory cortex located in the postcentral gyrus of the parietal lobe.

Answer 26

gracillis cuneatus arcuate fibers thalamocortical neurons

Question 27

The spinothalamic tract lies lateral and ventral to the ------- horn of the spinal --------- matter.

Answer 27

ventral grey

Question 28

The spinothalamic tract carries information related to ------ and ----------- sensations and also non discriminative touch and pressure

Answer 28

pain thermal

Question 29

Distinct lateral and ventral spinal thalamic tracts conveying pain and temperature or touch and pressure, respectively, have been identified. However, fibres carrying these modalities are probably ----------- to some extent.

Answer 29

intermingled

Question 30

The spinothalamic tract contains second order neurons, the cell bodies of which lie in the -------------- dorsal horn and receive input from primary --------- fibres that terminate in this region

Answer 30

contralateral afferent

Question 31

After leaving the parent cell bodies spinothalamic -------s decussate to the opposite side of the cord by passing through the ventral white ------------ which lies ventral to the central canal of the cord and thus enter the contralateral spinothalamic ----------.

Answer 31

axons commissure tract

Question 32

Axons carrying pain and temperature decussate promptly within one segment of their -------- while those carrying touch and pressure may ascend for -----------segments before crossing.

Answer 32

origin several

Question 33

In the brainstem the spinothalamic fibers run in close proximity to the -------- ----------- and are known as the spinal lemniscus

Answer 33

medial lemniscus

Question 34

The majority of fibres terminate in the ventral posterior nucleus of the thalamus, contacting 3rd order thalamocortical neurons that project to the s----------- --------

Answer 34

somatosensory cortex.

Question 35

The spinothalamic tract is thought to be the root via which sharp pricking pain sometimes called -------- pain is conducted.

Answer 35

fast

Question 36

Interoception, exteroception and proprioception from trunk and limbs are delivered to the CNS by -------- -------- neurons (PNS) to the spinal cord.

Answer 36

first order

Question 37

Ascending tracts: Pain, temperature and crude touch decussate in the spinal cord and ascend contralaterally via the STT to the primary ------------ -------------

Answer 37

somatosensory cortex.

Question 38

Ascending Tracts: Tactile and proprioceptive pathways ascend ---------ally via the fasciculus -------- and the fasciculus ---------- before decussating in the brainstem to ascend contralaterally to the primary somatosensory cortex.

Answer 38

ipsilaterally gracilis cuneatus

Question 39

Ascending Tracts: Spinocerebellar pathway (proprioception from skeletal muscle to cerebellum) is ipsilateral with the ventral spinocerebellar pathway ----------- crossing and the dorsal spinocerebellar pathway does not cross

Answer 39

double

Question 40

Motor and Sensory Cortex: The medial lemniscus terminates in the ------------ posterior nucleus of the thalamus upon 3rd order ------------- neurons

Answer 40

ventral thalamocortical

Question 41

Motor and Sensory Cortex: The majority of STT fibres terminate in the ventral --------- nucleus of the thalamus, contacting 3rd order ------------ neurons. These in turn project to the somatosensory cortex located in the ---------- ------------ of the parietal lobe i.e. the somatic sensory cortex.

Answer 41

posterior thalamocortical postcentral gyrus

Question 42

Motor and sensory cortex: The sensory --------------- is a map along the cerebral cortex of where each part of the body is processed, allows us to recall the sensory regions in the cortex!

Answer 42

homunculus

Question 43

----------------- tract provides somatic sensation to the face and head

Answer 43

Trigeminothalamic

Question 44

Peripheral Receptors and Sensation Structures served by trigeminal system Name 4

Answer 44

1. Cornea 2. Mucocutaneous tissues around mouth and nostrils 3. Oral and nasal mucosae 4. Paranasal sinuses 5. Tongue (anterior 2/3rds) 6. Teeth and gums 7. Dura of anterior and middle cranial fossae 8. Skin of face to the vertex except angle of jaw 9. Parts of external ear

Question 45

Primary Sensory Neurons: The sensory fibres of the trigeminal nerve are primary sensory neurons with peripheral processes distributed via the ---------------, ------------ and ----------- divisions of the trigeminal to numerous structures of the head.

Answer 45

ophthalmic, maxillary and mandibular

Question 46

Primary Sensory Neurons: Sensations of touch, pressure, pain and temperature are relayed from the face and scalp, the cornea, the nasal and oral cavities, including the teeth and gums and the ------------- sinuses.

Answer 46

paranasal

Question 47

Primary Sensory Neurons: The trigeminal nerve also innervates the ------------ -------- mater and ----------- arteries.

Answer 47

intracranial dura intracranial

Question 48

Primary Sensory Neurons: Proprioceptive fibres are carried from the muscles of -------------- and the --.---.---

Answer 48

mastication TMJ

Question 49

Primary Sensory Neurons: The cell bodies of afferents in the trigeminal nerve (with the exception of those conveying proprioception) are located in the ----------- ganglion, located at the convergence of the -----------, ---------- and ---------- nerves. The central processes of these cells terminate in the ------------ sensory nucleus.

Answer 49

trigeminal ophthalmic, maxillary and mandibular trigeminal

Question 50

The trigeminal sensory nucleus is a large nucleus that extends throughout the length of the ------- --------- and into the upper cervical spinal cord

Answer 50

brain stem

Question 51

The chief sensory nucleus lies in the ----------- ---------- close to the entry of the trigeminal nerve. It mediates fine touch stimuli, joint position and vibration.

Answer 51

pontine tegmentum

Question 52

The mesencephalic nucleus extends rostrally into the ------------

Answer 52

midbrain

Question 53

The spinal nucleus (nucleus of the spinal tract of the trigeminal) extends caudally through the ---------- and into the cord. It mediates ------------- and ------------

Answer 53

medulla pain and temperature.

Question 54

Those afferent fibres carrying pain and temperature end in the spinal nucleus reaching their termination by descending in the spinal tract of the trigeminal -------- of fibres lying immediately superficial to the nucleus.

Answer 54

fascicle

Question 55

Proprioceptive afferents from the muscles of mastication and the temporomandibular joint have their cell bodies not in the ----------- ----------- as might be expected but in the ------------ ----------- of the trigeminal. They are the only primary afferents to have their cell bodies located within the CNS.

Answer 55

trigeminal ganglion mesencephalic nucleus

Question 56

Axons of 2nd order neurons in the trigeminal nucleus decussate to form the contralateral trigeminothalamic tract to the ------------------------ (VPM) nucleus of the thalamus.

Answer 56

ventroposteromedial

Question 57

3rd order neurons in the thalamus project to the ------------- ------------- i.e. primary sensory cortex.

Answer 57

postcentral gyrus

Question 58

Clinical perspectives: Sensory system lesions Name the example

Answer 58

Peripheral Nerve Lesions

Question 59

Peripheral Nerve Lesions What order neurons affected?

Answer 59

primary

Question 60

Peripheral Nerve Lesions can be caused by ?

Answer 60

Neuritis

Question 61

Peripheral Nerve Lesions can result in ....?

Answer 61

diseases or dysfunctions of their nerves can present with problems in any of the normal nerve functions

Question 62

Peripheral Nerve Lesions: Sensory Function effects? (Name one positive and one negative)

Answer 62

- Loss of function (negative) Symptoms: numbness, tremor, and gait abnormality - Gain of function (positive) Symptoms: tingling, pain, itching, crawling, pins and needles - Skin can become so hypersensitive that patients are prohibited from having anything touch certain parts of their body, especially feet

Question 63

Clinical perspectives: Neuritis (inflammation of the PNS): Causes?

Answer 63

- Physical injury - Infection such as herpes simplex, shingles, leprosy, lyme disease, Bells Palsy - Chemical injury - Radiation - Nutritional deficiencies

Question 64

Clinical System Lesions: Dissociated sensory loss Lesions of the spinal cord or brainstem may only affect one ------- Dissociated sensory loss: - deficit in the modality of pain/temp OR touch/propoception - N.B. all ascending axons decussate in the -------- ---------- (STT) or lower ----------- (MLP), so lesions in the upper brainstem result in a loss of all sensation on the ------------ side of the body

Answer 64

pathway spinal cord brainstem contralateral

Question 65

Clinical Perspectives: Sensory System Lesions: ------------------- - --------------- disrupts the decussating fibres of the spinothalamic system - Most common in cervical and upper thoracic regions, less common in the ascending fibres of the dorsal column medial lemniscal system - Cape like distribution of loss of pain, temp, crude touch sensation from above lesion

Answer 65

Syringomyelia x2

Question 66

Clinical Perspectives: Sensory System Lesions ----------- ------------ ---------- - Spinal cord injuries are rarely limited to a particular tract - BSS may be caused by * a spinal tumor * trauma (such as a puncture to the neck or back) * ischemia (obstruction of blood vessel) * infectious or inflammatory diseases such as tuberculosis, or multiple sclerosis - Incomplete spinal cord lesion characterised by a hemisection of the spinal cord - Contralateral loss of pain and temperature (STT) sensation, and an ipsilateral loss of position and vibration sensation, as well as paresthesia (tingling)

Answer 66

Brown Sequard Syndrome

Question 67

Clinical Perspectives: Sensory System Lesions: ------------------ --------------- pain/Referred pain - Neuropathic pain is a complex, chronic pain state that usually is accompanied by tissue affecting the STT - Nerve fibres themselves may be damaged, dysfunctional or injured - Referred pain is pain perceived at a location other than the site of the painful stimulus - Zone of reference of the pain from an int organ coincides with the part of the body served by the somatic sensory neurons - The heart is supplied with pain fibres that overlap with somatic sensory neurons of chest and inner left arm - STT and somatosensory cortex does not clearly discern whether the pain is coming from the body or wall or from the viscera

Answer 67

Central Neuropathic Pain