Spinal cord

Question 1

Which cervical vertebra does NOT have a bifid spinous process?

Answer 1

C1 has no spinous process

Note: Its chief peculiarity is that it has no body, and this is due to the fact that the body of the atlas has fused with that of the Axis– to form the dens or odontoid process of the Axis

Recall: process- sharp slender projection, process in general refers to something emerging or projecting from the surface of the bone

Question 2

Which ligament extends the length of the vertebral column and suports the vertebrae?

Answer 2

Anterior longitudinal ligament
The anterior longitudinal ligament runs down the vertebral bodies and intervertebral discs of all of the vertebrae on their ventral side

may become calcified, causing back pain

Question 3

What are the 6 ligaments of the vertebral column?

Answer 3

The major ligaments of the vertebral column include: the anterior and posterior longitudinal ligaments, ligamenta flava, supraspinatus ligament, ligamentum nuchae and the interspinous ligaments.

Question 4

Lumbar puncture is a diagnostic procedure most commonly used for collecting cerebrospinal fluid from the spinal canal, in order to analyze it for detecting pathological processes in several diseases such as multiple sclerosis or meningitis. Into which anatomical space is the needle inserted during lumbar puncture, in order to collect cerebrospinal fluid?

• pia mater
• arachanoid mater
• dura mater
• subdural space
• subarachnoid space
• epidural space

Answer 4

Subarachnoid space

The cranial arachnoid mater is a spiderweb-like meningeal layer, interposed between the dura and pia. The potential space between the arachnoid and dura is called the subdural space. The space between the arachnoid and pia is called the subarachnoid space and it is filled with the cerebrospinal fluid (CSF).

A lumbar puncture is an invasive procedure used to collect a sample of cerebrospinal fluid (CSF) from the subarachnoid space.

Question 5

Which structure of the brain is the continuation of the spinal cord cranially?

Answer 5

Medulla oblongata

medulla is continuation of SC cranially, sits in posterior cranial fossa

medulla is continuation of SC cranially, sits in posterior cranial fossa, below tentorium cerebelli.

The rostral medulla is continuous with the pons superiorly, with which it forms the pontomedullary junction. The caudal medulla continues onto the spinal cord inferiorly, just above the origin of the first pair of the cervical spinal nerves.

Question 6

Which part of the spinal cord (medulla spinalis) contains cell bodies of neurons and glial cells?

Answer 6

Grey matter - this is key, opposite of brain

N.b.The grey column, (as three regions of grey columns) in the center of the cord, is shaped like a butterfly and consists of cell bodies of interneurons, motor neurons, neuroglia cells and unmyelinated axons.

this is section presum. of lumbar spinal ord

Question 7

Cell bodies (perikarya) of which of the following structures send afferent nerve fibers to the posterior/dorsal horn of the spinal cord (medulla spinalis)?

In other words, where are cell bodies of afferent nerve fibres located?
- spinal ganglion
- white matter
- grey matter
- ventral horn
- ventral root of spinal cord

Answer 7

A - the spinal or dorsal root ganglion

Cell bodies of the spinal ganglion (ganglion spinale) send afferent nerve fibers to the posterior horn of the spinal cord.

Question 8

A 12-year-old boy quickly fatigues after short periods of walking and also suffers from pain in the lumbar region. After extensive neurological examinations a “Tethered-cord-syndrome” is suspected. In this disease the caudal end of the spinal cord is attached to the caudal end of the spinal canal and causes strain. What is the name of the caudal end of the spinal cord?

- cauda equina - dura mater - ventral horn - conus medullaris -ls

Answer 8

D - conus medullaris

The conus medullaris (medullary cone) is the cone-shaped terminal portion of the spinal cord. The tip of the conus medullaris is found between the L1 and L2 vertebra in the average adult. The conus medullaris is tethered to the coccyx by a fibrous cord called the filum terminale, which stabilizes the distal end of the spinal cord. it consists of the sacral (S2-S5) and coccygeal spinal cord segments.

NOTE: it is NOT the cauda equina, cauda equina is the continuation of these nerve roots in the lumbar and sacral region.

Question 9

extra stuff

Define and briefly describe cauda equina syndrome

Answer 9

Cauda equina syndrome is caused by a compression or irritation of lumbosacral spinal nerve roots, often due to lumbar disc herniation. The most common symptoms include low back pain that radiates into the sacral region and legs, and bilateral motor and sensory deficits, which present as asymmetric saddle anesthesia (S2-S5 dermatomes) and asymmetric lower limb weakness.

Note may also see dysfunction ofcontrol of genitourinaty system (fecal, urinary incontinence, erectile dysfunction

Question 10

Describe disc herniation

Answer 10

Herniated disc is a condition in which there is a lesion or rupture in the outer fibrous ring of the intervertebral disc (annulus), that leads to bulging of the inner portion (nucleus). The discs are fibrocartilaginous pads between the vertebrae which act as a shock absorber and allows for flexible movement of the vertebral column.

Risk factors include:

Age between 30-50 
Males are more commonly affected as compared to females
Heavy weight lifting
Obesity; increased body weight can place added stress on the lumbar spine
Sudden strain from twisting or quick movements/Trauma
Strenuous activity that is repeated over time
Smoking
Improper posture

Sites of herniation

There could be midline, paramedian, posterolateral and anterior disc herniation. It may be unilateral or bilateral. Sometimes there is an intravertebral herniation characterised by the herniation of the nucleus pulposus into the intervertebral body through a fracture, this is also known as Schmorl’s node.
Signs and symptoms

Depending on where the disc herniation has occurred in the spine will determine the symptoms patients present with.

Herniated disc symptoms of the lower back:

Lower back pain
Sharp, shooting pain down the back of the leg in conjunction with sciatica
Numbness in one leg or buttock or feet
Burning pain
Pins and needles sensation
Tingling in legs
Leg weakness
Muscle weakness
Loss of bladder or bowel control

Herniated disc symptoms of the neck:

Neck pain and back pain
Pain in trapezius muscle
Spasm of the neck muscles
Shooting pains down the arm
Burning pain in the arm, neck or shoulders
Arm weakness
Tingling in arms
Pins and needles in the arm
Loss of bladder or bowel control
Headache in the back of the head

Question 11

Through which openings do the nerve roots of the spinal cord exit the spinal canal?
- vertebral formamen
- trsnverse foramen
- intervertebral foramen
- intervertebral disc
- obturator foramen of hip

Answer 11

There are 31 bilateral pairs of spinal nerves, named from the vertebra they correspond to. For the most part, the spinal nerves exit the vertebral canal through the intervertebral foramen below their corresponding vertebra. Therefore, there are 12 pairs of thoracic spinal nerves, 5 pairs of lumbar spinal nerves, 5 pairs of sacral spinal nerves, and a coccygeal nerve.

- transverse foramen is for vertebral artery, vein, adn symp nerves

Question 12

Which part of the vertebra is located lateral to the spinal cord?

Answer 12

Pedicle of vertebral arch

Question 13

A 15-year-old patient with a 10-month history of generalized epilepsy is admitted to the hospital. A cranial MRI scan reveals a tumor in the area of the precentral gyrus. The integrity of which tract should be tested by the attending neurologist, as it originates in this part of the cerebral cortex?

• rubrospinal tract
• solitary tract
• tectospinal tract
• pyramidal tract
• spinocerebellar tract

Answer 13

Pyramidal tract

Question 14

Both the DCML and spinocerebellar tracts carry information on proprioception. What is the difference between them?

Answer 14

The ascending tracts refer to the neural pathways by which sensory information from the peripheral nerves is transmitted to the cerebral cortex. In some texts, ascending tracts are also known as somatosensory pathways or systems.

Functionally, the ascending tracts can be divided into the type of information they transmit – conscious or unconscious:

Conscious tracts – comprised of the dorsal column-medial lemniscal pathway and the anterolateral system.
Unconscious tracts – comprised of the spinocerebellar tracts.

Question 15

Complete the sentence: The third order neurones of the DCML ascend from the ___________ and synapse in the sensory cortex

Answer 15

thalamus

Question 16

Which of the following structure lies adjacent to the spinal cord (medulla spinalis) and forms its direct sheath?

Answer 16

pia mater

Order from ext to int: Dug A Pit

Pia mater is the innermost layer of the meninges, the connective tissue layers that surround the central nervous system. It is a thin, transparent, delicate sheath that hugs the surface of the brain and spinal cord, closely following its contours. The pia and arachnoid layers of the meninges are collectively called the leptomeninges. Located between these two layers is the cerebrospinal fluid containing subarachnoid space.

Question 17

Which tract in the posterior funiculus primarily transmits sensory information of the upper limb?

Answer 17

Cuneate fasciculus of DCML

Gracile is lumar/sacral. Cuneate of Cervical/thoracic

Question 18

Which of the following structures are the attachment points of the spinal dura mater?

Answer 18

Tectorial membrane, and posterior longitudinal lig.

Question 19

Which of the following structures occupy the posterior funiculus of the spinal cord?

Answer 19

Cuneate an Gracile funiculus

DCML , cunaeatecervical thoracic, gracile lumbar thoracic

Question 20

Which of the following arteries supplies blood to the spinal dura mater?

Answer 20

Meningeal branches of vertebral artery

Question 21

Which part of the spinal cord contains the preganglionic sympathetic neurons only present in the thoracic and upper lumbar segments of the spinal cord?

Answer 21

Lateral horn

Question 22

Which two tracts are part of the pyramidal tract?

Answer 22

Anterior and lateral corticospinal tracts

Question 23

What is the name of the thin strip of grey matter that surrounds the central canal of the spinal cord?

Answer 23

Ant. grey commissure

Question 24

Answer the question below.
A 7-year-old girl presenting with headache, vomiting, irritability and neck stiffness is suspected to have meningitis. To confirm the diagnosis, the doctor needs to perform a lumbar puncture to extract the cerebrospinal fluid (CSF) from the subarachnoid space of the spinal canal. In order to avoid damaging the spinal cord, the doctor must insert the needle below the termination of the spinal cord and above the termination of the dura mater. Between which of the following vertebra should the needle be inserted?

Answer 24

L3 and S2

Correct

A lumbar puncture (or colloquially, “spinal tap”) is a procedure of collecting the cerebrospinal fluid for further examinations. Because the spinal cord terminates at the L1/L2 vertebral level, lumbar puncture is performed at the lumbar cistern between two vertebrae at level L3/L4, or L4/L5, where there is virtually no risk of accidental injury to the spinal cord. One can locate L3/L4 disc space by following the iliac crest posteriorly (intercristal line).

Dura mater terminates at level of S2, filum terminale

Question 25

Discuss and describe blood supply to spinal cord

Answer 25

The anterior and two posterior spinal arteries are direct branches of the two vertebral arteries which merge rostrally to form a single artery - the basilar artery. Thus, the vertebral arteries are very important, as they serve as the primary source of blood to the brain and the spinal cord.

The spinal cord receives blood from three longitudinal arterial channels that extend along the length of the spinal cord. These longitudinal arteries are:

the anterior spinal artery, which runs along the anterior median fissure
two posterior spinal arteries, which run (one on each side of the midline) along the posterolateral sulcus (i.e., along the line of attachment of the dorsal nerve roots).

Question 26

Answer the question below.
A 30-year-old man suffers from recurrent pain in both arms and the shoulder region. Finally he is referred to a neurologist, who assumes that his symptoms might be caused by syringomyelia. This is a disease which can result in cerebrospinal fluid accumulation inside the spinal cord. Which part of the spinal cord contains cerebrospinal fluid and expands as a consequence of the accumulation?

Answer 26

Central canal of spinal cord

Question 27

What is the fibrous structure that extends inferiorly from the conus medullaris of the spinal cord to the coccyx?

Answer 27

Filum terminale

Question 28

Which part of the spinal cord contains motor neurons that project efferent fibers to the muscles of the body?

Answer 28

Ventral horn

Question 29

What is notable about thoracic vertebrae?

Answer 29

Extra articulating facets for ribs (costotransverse and * joints)

There are 6 facets per thoracic vertebrae: 2 on the transverse processes and 4 demifacets. The facets of the transverse processes articulate with the tubercle of the associated rib. The demifacets are bilaterally paired and located on the superior and inferior posterolateral aspects of the vertebrae. They are positioned so that the superior demifacet of inferior vertebrae articulates with the head of the same rib that articulates with the inferior demifacet of a superior rib. For example, the inferior demifacets of T4 and the superior demifacets of T5 articulate with the head of rib 5.

The costovertebral joints describe two groups of synovial plane joints which connect the proximal end of the ribs with their corresponding vertebrae, enclosing the thoracic cage from the posterior side. Precisely, these joints are described as;

The connection between the heads of the ribs with the sides of one, or two adjacent vertebral bodies are known as the costocorporeal joints/joints of head of ribs.
The articulations of the necks and tubercles of the ribs with the transverse processes of their corresponding thoracic vertebra are the costotransverse joints.

Question 30

Answer the question below.
A 55-year-old woman suffers from postural instability and insecurity while walking. She finds it difficult to stand steadily especially in the dark and therefore attends a neurologist. The neurologist finds out, that the patient is unable to perceive vibration on her right leg. Hence, the doctor considers an impairment of which ipsilateral spinal tract?

Answer 30

Gracile asciculus of DCML

Question 31

Answer the question below.
A 60-year-old man notices that the tactile sensation of his left arm is impaired. In addition to that, his neurologist asserts the patient’s inability of perceiving vibration with his left arm. The doctor thus considers the impairment of which ipsilateral spinal tract?

Answer 31

Cuneate fasciculus of DCML

Question 32

Which two spinal tracts in the white matter are part of the pyramidal tract?

Answer 32

Ant. and lat. corticospinal tract

Corticobulbar hangs in brainstem, does not descend

Question 33

List the ascending tracts

Answer 33

dorsal column-medial lemniscus system, spinothalamic (or anterolateral) system, and spinocerebellar system.

Question 34

List the descending tracts

Answer 34

lateral and anterior corticospinal tracts, the vestibulospinal, the rubrospinal (with lat corticospinal), and the reticulospinal tracts

Question 35

What are the extrapyramidal tracts?

hint 4

Answer 35

Originate in the brainstem, carrying motor fibres to the spinal cord. They are responsible for the unconscious, reflexive or responsive control of musculature, eg muscle tone, balance, posture and locomotion.
The four main pathways that connect the aforementioned structures are the reticulospinal, vestibulospinal, rubrospinal and tectospinal tracts

Question 36

Pyramidal tracts

Answer 36

Pyramidal tracts: Conscious control of muscles from the cerebral cortex to the muscles of the body and face.
Functionally, the Pyramidal tracts can be subdivided into two:

Corticospinal tracts – supplies the musculature of the body.
Corticobulbar tracts – supplies the musculature of the head and neck
	
	think: head is a bulb

Question 37

Describe the pathway of the dorsal column medial lemniscus pathway

Answer 37

see disstinguihs anser below

Question 38

Describe the pathway of the spinothalamic pathway

Answer 38

see distinguish answer below

Question 39

List some other ascending spinal tracts

Answer 39

• spino olivary: cutaneous and proprioceptive organs muscles and tendons
• both anterior and lateral
• decussate in cerebellum
• spinocerebellar, post, ant, and lateral
• ant decussate at spinal cord. lat

Overall: unconscious propriocepetion, cutaneous touch, pressure, from lowert limb and trunk (mainly post, ant also does uncosnscious proceotion form lower linb)

• nb cuneocerebellar: post sspino cerebellari.e.. (see above)

SPINOretucrilar: bahvioural awareness and modifies sensoyr and motor info

Spinotectal functional unclear , nociceptive?
travels close to ant/lat spinothalamic

Question 40

Distinguish between spinothalamic and DCML pathways and function

Answer 40

both spino thtalamic and DCML are ascending sensory motor tracts.

DCMl decussates in causal closed medulla (cranial to site of motor decussation)
Spinothalamic decussates at level of spinal cord, at or entry of 1st order neeuon from DRG.

Both travel in either gracile or cunaeate depnding on prgin of stimulus.
Example of organisation and informtion mapping in CNS
Gracile: if T7-Co1
Cunate if C1-T6

DCmL 1st order synaose in gracile and cunate nucleus of caudal closed medulla
SPino snapse near entry from DRG.

NB both have nuceloi in DRG

fianl synapse for both is thalamus, where it travesl to seomatosensory area of the parietal lobe of the cerebral cortex.

Functions:
spinothalamic:
- pain temperature, pressure, crude sensatuon, ictchiness
- anterior and lateral
- lateral responsible for prssure temperature a

anterir light or crude touch, also pressure

DCML:
- note: when DCML decussates in closed caudal medulla, (with arcuate fibres), frms mediaal lemniscus, thus is what travels up to thalamus
- function: fine touch, vibation, and proprioception

Conscious? Yes. Both

Question 41

List some other descending motor tracts

Answer 41

i.e. the extrapyramidals:
-** rubrospinal** : origin in rosttal midbrain, where it deccussates
- maintains and modulaes movements cooridinated by corticospinal tracy

reticulospina’
- medial and laterla
- medial inhibits flexion of muscles of trunk and limbs, allowing extension
- innervates alpha and gamma
decussates

• lateal opposes action of medial, inhibits alpha and hamma, thus inhibits extension, enables flexots of trunk and limb

olivospinal
no decurssation
existene debated

• vestibulospinal
• med and lat: neck and ul; extesnora nd body posture

TECTOspinal:
- cerf, upper limb, thoracic, llinks auditory adn visual stimuli with muscle movement

Question 42

What is found in the grey matter of the CNS?

Answer 42

gray matter contains a large number of cell somas and dendrites

Question 43

What is found in white matter of spinal cord?

Answer 43

white matter contains axons, neuronal fibres many of those myelinated giving the whitish tinge to the tissue. It is important to note, that the cortex of the brain and the cerebellum are grey matters and they are closest to the surface of these structures.

Question 44

Distinguish between location of grey matter and white matter in brain vs spinal cord

Answer 44

While the grey matter of the spinal cord is positioned deeper, and surrounded by the white matter on the surface. There are a number of grey matter structures deep inside the brain and cerebellum. These structures contain a large number of neurons that have similar functional roles. These collections of cell somas are called nuclei in the CNS (i.e. forebrain nuclei, deep cerebellar nuclei).

NB, in the PNS, cell somas are collected in ganglia.

Question 45

Define fascicles

Answer 45

The axons of nerves with similar function are bundled together within the white matter. These bundles are described as fasciculus, tract, leminscus, or pathway (i.e. Fasciculus gracilis, medial lemniscus, corticospinal tract, motor pathways).

Question 46

How are axons bundled in PNS?

Answer 46

in the PNS the axons are bundled together into individual peripheral nerves, or plexuses.

Question 47

Distinguish between types of fibres found in axon bundles

Answer 47

• Projection fibres are the longest ones, they connect the cortex with subcortical structures (i.e. thalamus, brainstem, spinal cord). Areas of the brain are also connected to allow the harmonic organization of cortical responses.
• Areas within the same hemisphere are described as association fibres.
• Commissural fibres are those that cross the midline to connect the two sides of the CNS. The action of crossing the midline is described as decussation

Question 48

Define and distinguish between CNS and PNS

Answer 48

Definitions
- The nervous system detects changes in the external or internal environment and responds to those through activation of muscles, glands or organs.
- The central nervous system are the components of the nervous system contained within the skull and the nervous system i.e. the brain (cerebrum, cerebellum, brain stem), spinal cord, retina
note: the CNS has poor capacity to regenerate

• The peripheral nervous system are the components of the nervous system distributed to organs and structures i.e. in the head and neck as the 12 cranial nerves attached to the brain, and throughout the rest of the body as ‘spinal’ and ‘peripheral’ nerves
  These nerves go on to become ‘named’ nerves
  n.b. the PNS has good regenerative capacities

Question 49

List the functions of the nervous system

Answer 49

• to transmit and process all general and special sensory information, from the periphery – afferent and sensory systems responsible
• controls movement and behaviour – motor and efferent systems responsible
• influences all ‘regulatory functions’ in the body
  
  • directly i.e. via ANS
  • indirectly via control of key hormones released by the pituitary gland i.e. endocrine system
• is the site of ‘higher functions’ or cognitive e.g. associations, decision making, creative processes, motivation, thought processes…
  ~ These include both conscious and sub/unconscious processes~

Question 50

Describe the neurons found in CNS and PNS

Answer 50

Recall that there are three broad categories of neurons:
- sensory: sensory neurons are usually pseudounipolar; cell bodies are typically found outside the CNS in peripheral ganglia; axon termini found in CNS.
The nerve endings of the sensory neuron include specialised sensory receptors e.g. in skin, mucous membranes, joints, tendons, muscles.

The cell bodies are located in peripheral ganglia such as the dorsal root ganglia of the spinal cord, sensory ganglia associated with the cranial nerves V, VII, VIII, IX and X (i.e. if coming from head or neck).

Sensory pathways are known as afferent systems or pathways. (Think afferent for approaching the spinal cord)

• inter-neuron: typically bipolar, entirety of neuron found in CNS ^[note that interneurons are also found in autonomic ganglia in PNS]
• motor: typically multipolar; cell bodies are typically found within the CNS, axon and termini found in PNS

Motor systems or efferent pathways convey either voluntary or involuntary signals from the centre i.e. the ‘motor cortex’ to the periphery to enable movement.
Think efferent, for exiting the CNS

Input and output can be either be somatic or autonomic:

Somatic motor output:
- In brain: input comes from motor cortex and motor centres i.e. upper motor neurons or UMN
- In brainstem from cranial nerve motor nuclei i.e. lower motor neurons or LMNs
- In spinal cord from ventral horn i.e. lower motor neurons or LMNs
somatic motor output is conveyed directly to motor nerve end-plate in skeletal muscle

Autonomic system
- In brain: input comes from hypothalamus
- In brainstem: from cranial nerve autonomic nuclei
- In spinal cord from lateral horn in certain segments
Autonomic motor output is conveyed indirectly ^[cv somatic , where brain stem/spinal cord goes all the way to muscle to control – only 1 synapse - the NMJ, while going to viscera 2 neurons needed, 1 leaves CNS, the 2nd reaches its target] to several sites:
- secretomotor nerve ending in glands
- smooth muscles in organs and vessels
- cardiac muscle

Question 51

Define and distinguish between general and special senses

Answer 51

General somatic senses include vibration, touch, pressure, pain, temperature, deep sensation e.g. proprioception ^[also includes discriminative touch e.g. reading Braille or feeling texture]. Sensory receptors in skin/muscle spindle, Golgi apparatus in muscle tendon
- Special senses i.e. smell, sight, hearing, balance, taste; carried out by particular cranial nerves, with direct input from the receptors to the brain

Question 52

Describe the non neuronal cells

Answer 52

These cells include:
1. Astrocytes or Muller cells: these are the largest glial cells, and have a stellate appearance for which they are named.
They are the primary glia in the retina.
Astrocytes are key for maintaining the nervous system ^[dead glia means dead neurons]
They have several functions include:
- providing support for neurons
- constituting a barrier against transmitter spread at synapses
- recycling neurotransmitters, that would otherwise be toxic to cells if buildup
- constitutes blood brain barrier, adding strength
- buffer against K+ increase ^ [how?]
- gliosis: a response to injury, trauma, infection, damage
2. Microglia: these are the smallest of the neuroglia; it serves as a tissue monitor and contributes to the immune response (via phagocytosis)
3. Oligodendrocytes ^[the analogous structure in the PNS is the Schwann cell] provide myelination for CNS neurons. They are smaller than astrocytes, and also have fewer and shorter processes. Note that one cell can myelinate multiple parts of one axon, or multiple axons ^[c.v. Schwann, where one axon is myelinated by multiple Schwann cells]
4. Ependyma form the lining of the ventricular system ^[‘like the mucosa of the ventricles’]

Question 53

Describe the organisation of the CNS/spinal cord

Answer 53

The CNS can be organised into
- grey matter: made up by neuronal cell bodies ad their dendrites
- white matter: made up by axons, most of which have an insulating layer of myelin (in the brain)
![[Pasted image 20230426154553.png]]
The spinal cord, the most primitive part of the nervous system, can be organised into
- grey matter
- which is found on the inside
- it can be further categorised into functional regions: the sensory region dorsally, the motor region ventrally, and the middle region containing bipolar interneurons and autonomic fibres
- white matter
- which is found on the outside
- is also further categorised into specific functional regions:
- sensory tracts, ascending
![[Pasted image 20230426155356.png]]
- motor tracts, descending
![[Pasted image 20230426155414.png]]
The point of the organisation of the spinal cord is to give the brain a clue as to where the information is coming from

Question 54

Define plexus

Answer 54

Segments that innervate the neck, upper and lower limbs sort themselves
into named peripheral nerves in the cervical (neck), brachial (upper limb)
and lumbo-sacral (lower limb) plexuses
From Netter Atlas of Human Anatomy
Brachial
Plexus
A plexus is an exchange
of fibres between the
ventral primary rami of
the mixed spinal nerves.
Named peripheral nerves
are branches of a plexus.
Example:
The named branches
innervate the skin of
the upper limb and the
muscles that move it

note equivalent on CNS = tracts

Question 55

Describe the source of dermatomes and myotomes

Answer 55

each segment innervates / ‘supplies’ a sensory territory (dermatome) and a motor
territory (myotome) on the trunk or limbs

Dermatomes & Myotomes - Some Important Principles
1. Dermatomes and myotomes do not (necessarily) overlap in adults,
but they still work together
1. Myotomes: Segments from the upper part of the plexus innervate the
proximal muscle groups; segments from the lower part of the group
innervate the distal muscle groups
2. Dermatomes: The most distal dermatomes (eg., for the upper limb,
the finger tips, C7), are supplied by segments in the middle of the
plexus (C5-T1)

Notes:
* C1 does not have a cutaneous
representation
* C2-Coccygeal nerves
innervate strips of skin down
the back, as far as the coccyx
- there are no sharp
boundaries - border regions are
innervated by adjacent nerves
* The muscles underlying these
dermatome segments on the
trunk are innervated by fibres
from the same segment. On the
limbs the dermatomes and
myotomes are not aligned.

Question 56

Define reflexes, types and components

Answer 56

REflexes: automatic or involuntary sterotyped pattern of response to a senosry stiumlus
No conscious thought*

The reflex arc
Ø Basic functional system of nervous system
Ø Simplest unit capable of receiving stimulus
and producing response
Ø Two types:
Exteroceptive (cutaneous)
Proprioceptive (stretch)
Ø Components:
sensory receptor
sensory neuron
interneurons
motor neuron
effector organ

*although will travel ip later i.e. you know

Question 57

Describe autonomic output of spinal cord

Answer 57

AUTONOMIC OUTPUT OF THE SPINAL CORD
n Autonomic motor nerves found only in certain segments
n Sympathetic neurons in T1-L2,
n Parasympathetic neurons at S2-4
n Autonomic motor neurons found in the lateral horn
n Autonomic system uses 2 neurons that synapse in a visceral
ganglion

Question 58

True or Flase: para and sympathetic divisions can be activated simultaneuously

Answer 58

FALSE
Parasympathetic and sympathetic subdivisions of autonomic nervous system are in dynamic baalnce
They have complementary roles
As such thye cannot be activated simultaneouly

n.b.Level of activity in each depends upon the local environment/circumstances
* Balance between the two can change very rapidly

Question 59

Cimpare and contrast functions of parasymp and symp

Answer 59

Para

Acts in favour of the
long-term well-being
of the organism
Conserves the
body’s resources
Regulates digestion,
growth, immune
responses, energy
storage.

Slows heart
Constrict airways
Stimulate digestion
Stimulate glands (salivation)
Stimulate bladder (urination)
Stimulate sexual arousa

Symp’
Active during criss
aall or nothing response
Accelerate heart rate
Relax airways(panting)
Stimulate sweating
Inhibit digestion and
glands
Dilates pupils
Relaxes the bladder (urine
retention)
Stimulates suprarenal
gland (A, NA release from
adrenal medulla)

Question 60

Distinguish between sy and psy ganglia

Answer 60

All autonomic nerve synapses in an autonomic motor ganglion (exc those
controlling the suprarenal gland)
* SY ganglia are close to the CNS
* PSY ganglia close to the target organ

Question 61

How does sympathetic output get to entire body?

Answer 61

SY output only present at T1-L2!
Getting sympathetic innervation to higher & lower
segments – the sympathetic chain

-The paravertebral ganglia are linked
together to form the sympathetic chain
- The ‘links’ between individual ganglia
comprise both pre- and post-ganglionic
fibres, that are ascending or descending in
the chain to reach spinal nerves below L2,
cervical nerves and cranial nerves.

As a result, the sympathetic chain extends the full length of v. volumn

Question 62

How to get sympathetic innervation to GIT

Answer 62

The pre-vertebral ganglia sit anterior
to the aorta,
- They get pre-ganglionic inputs from
the splanchnic nerves and innervate
the gut
greater splanchnic nerve ~T4-T8
lesser splanchnic nerve ~T9-T11
least/lower/lumbar splanchnic
nerve ~T12 – L2
-Post-ganglionic fibres are distributed
with branches of the aorta

Question 63

What do ‘mapped’ and ‘unmapped’ cortical regions do?

Answer 63

MAPPED REGIONS: Are the ‘first port­of-call’ for information coming into the cortex. They represent a ‘single modality’ (vision; somatosensory; auditory etc)
UNMAPPED REGIONS: Cross-reference all the information coming into the brain, so we can interpret it. They are ‘multi-modal’.

Question 64

Define dermatome

Answer 64

Area of skin that is served by a single spinal nerve

Question 65

Define myotome

Answer 65

A group of muscles innervated from a single spinal nerve