Anatomy: Axial Skeleton and Nervous System

Question 1

What are the two main systems in the nervous system?

Answer 1

The nervous system is structurally divided into main two systems: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
The CNS is composed of the brain and spinal cord. The PNS is composed of all the nerves that branch off from the CNS such as the cranial nerves and the spinal nerves.

Question 2

What are the two divisions of the PNS and what do they innervate?

Answer 2

Somatic nervous system (motor function of skeletal muscles and sensory function of skin)
Visceral nervous system (motor function of organs and glands and sensory function of organs)

Question 3

What are the two divisions of the motor innervation to the organs and glands?

Answer 3

Sympathetic (fight or flight)

Parasympathetic (rest and digest)

Question 4

What are the components of a neuron?

Answer 4

Dendrite: receive signals from other neurons. At the end of these projections are the synapses, where information is transferred.
Cell body: contains the cell nucleus and connects the dendrites (which receive information from other neurons) and the axon (which sends information to other neurons).
Cell nucleus: found within the cell body or soma.
Axon terminal: consists of long, slender nerve fibres that conduct electrical signals to a nerve synapse.

Question 5

How is a sensory neuron different to a motor neuron?

Answer 5

Cell body is at end of axon in motor neuron, but is in middle of axon in sensory neuron.

Question 6

What is the brain? What does folding of the cerebral cortex create?

Answer 6

The brain is made up of billions of neurons and is a central component of the nervous system, a network that transmits signals to and from different parts of the body, and regulates involuntary and voluntary actions.
Folding of the cerebral cortex creates sulci (singular: sulcus) and gyri (singular: gyrus) which separate brain regions.

Question 7

What are the different parts of the brain?

Answer 7

Frontal lobe
Precentral gyrus (part of the frontal lobe and lying immediately anterior to the central sulcus, this is the site of the primary motor cortex)
Central sulcus (a prominent landmark of the brain. It separates the frontal lobe from the parietal lobe and the primary motor cortex from the primary somatosensory cortex)
Postcentral gyrus (part of the parietal lobe and lying immediately posterior to the central sulcus, this is the site of the primary somatosensory cortex)
Parietal lobe
Lateral sulcus (also called “Sylvian fissure” or “lateral fissure”. This sulcus separates the frontal and parietal lobes from the temporal lobes. The insular cortex lies deep within the lateral sulcus)
Temporal lobe
Occipital lobe
Cerebellum

Question 8

What is the brainstem and what are its three components?

Answer 8

The brainstem is the most distal part of the brain and is continuous with the spinal cord. It is composed of three components: the midbrain (1); the pons (2) and the medulla oblongata (3). Each of these components has its own unique structure and function. Cranial nerves III to XII emerge from the brainstem.

Question 9

Where is the spinal cord? What does it pass through and what is it covered by?

Answer 9

The spinal cord extends from the medulla oblongata to the lumbar regions. It passes through the bony vertebral canal and like the brain it is covered by the meninges and surrounding cerebrospinal fluid.

Question 10

What are the three layers of the meninges?

Answer 10

Surrounding the central nervous system are 3 protective layers. From the outer most layer to the inner most layer these include the dura mater, arachnoid mater and pia mater.

Question 11

When performing a lumbar puncture, where is the needle inserted?

Answer 11

When performing a lumbar puncture, the needle is inserted into the space between the arachnoid mater and the pia mater (the subarachnoid space).

Question 12

When performing an epidural, where is the needle inserted?

Answer 12

When administering an epidural, the needle is inserted into the space between the vertebrae and dura mater (the epidural space).

Question 13

What is grey matter of the spinal cord made up of?

Answer 13

Mainly composed of neuronal cell bodies and unmyelinated axons.

Question 14

What is grey matter of the spinal cord made up of?

Answer 14

Mainly composed of myelinated axons.

Question 15

What is the arrangement of which and grey matter within the spinal cord?

Answer 15

In the spinal cord, white matter surrounds the centrally distributed grey matter.

Question 16

What is the arrangement of which and grey matter within the brain?

Answer 16

In the brain, white matter is found in deeper areas with surrounding grey matter. Other grey matter structures, such as the basal ganglia, lie deeper with the grey matter.

Question 17

What does the centrally located grey matter of the spinal cord consist of?

Answer 17

The centrally located grey matter of the spinal cord. It consists of a dorsal horn (located here) and a ventral horn.

Question 18

What does the white matter form in the spinal cord?

Answer 18

The white matter that is surrounding the grey matter. The white matter forms the ascending and descending tracts that carry information to and from the CNS.

Question 19

What are dorsal rootlets?

Answer 19

The sensory information carried through the dorsal root branches into dorsal rootlets to enter the spinal cord.

Question 20

What are ventral rootlets?

Answer 20

The motor information carried to the ventral root exits the spinal cord via the ventral rootlets.

Question 21

What is the dorsal root?

Answer 21

The dorsal root contains sensory (afferent) fibres from the skin, subcutaneous and deep tissues and viscera.

Question 22

What is the ventral root?

Answer 22

The ventral root contains motor (efferent) fibres that carry motor innervation to skeletal muscles.

Question 23

What is the dorsal root ganglion?

Answer 23

The cell bodies of sensory neurons are located in the dorsal root ganglion.

Question 24

What is the spinal nerve?

Answer 24

A spinal nerve is a mixed nerve consisting of both motor and sensory information.

Question 25

What is the pathway from the spinal nerve to the spinal cord and back?

Answer 25

``` Spinal nerve Dorsal root ganglion Dorsal root Dorsal rootlets Grey matter Ventral rootlets Ventral root Spinal nerve ```

Question 26

What are efferent and afferent nerves? Where do they enter and exit the spinal cord?

Answer 26

– Information has to either exit the spinal cord to send signals to peripheral tissues or information from peripheral tissues needs to be carried into the spinal cord. This is done via afferent (green) and efferent (red) fibres. Sensory (afferent) and motor (efferent) fibres enter and exit the cord via rootlets that arise from both the posterior and anterior aspects of the spinal cord.

Question 27

What do the ventral and dorsal rootlets do? What do the merge to become?

Answer 27

Ventral (anterior) rootlets carry motor information out of the spinal cord (i.e. they contain efferent fibres) while the dorsal (posterior) rootlets carry sensory information into the spinal cord (i.e. they contain afferent fibres). Several dorsal rootlets merge together to form the dorsal root, while several ventral rootlets similarly converge to form the ventral root.

Question 28

What is the dorsal root ganglion? What do these become afterwards?

Answer 28

The dorsal root ganglion is a collection of cell bodies found in the dorsal root. The ventral root does not contain a ganglion. Ganglia are only found where neuron cell bodies are outside the CNS. Distal to the dorsal root ganglion, the fibres of the ventral and dorsal root merge together and pass through the dura to become the spinal nerve. Spinal nerves contain both sensory (afferent) and motor (efferent) fibres and are therefore a mixed nerve.

Question 29

What are the ascending tracts?

Answer 29

The ascending tracts transport sensory information from the body to the brain. There are three orders of neurons that carry this information to the brain.

Question 30

What are the three orders of neurons in the ascending tract?

Answer 30

The first order neurons conducts impulses from peripheral receptors to the spinal cord, where is will synapse with second order neurons in the spinal cord or brainstem. The second order neurons will carry impulses up the spinal cord to the brain, usually the thalamus. The third order neurons carry information from the thalamus to the primary sensory cortex.

Question 31

What are the descending tracts?

Answer 31

The descending tracts transport motor information from the brain to the skeletal muscles. There are two order neurons that carry this information to the skeletal muscles.

Question 32

What are the two orders of neurons in the descending tracts?

Answer 32

The first order neuron, also known as the upper motor neuron, descends from the brain to the spinal cord or brainstem. It will synapse with the second order neuron, also known as the lower motor neuron in the grey matter of the spinal cord or brainstem. The lower motor neuron will then travel to the skeletal muscles.

Question 33

Which part of the spinal cord transmits information from the spinal cord to the extremities of the body?

Answer 33

Ventral roots

Question 34

Which functional division of the nervous system would be responsible for the physiological changes seen during exercise (e.g., increased heart rate and sweating)?

Answer 34

Autonomic

Question 35

What is a spinal nerve?

Answer 35

A mixed nerve and contains sensory and motor fibres.

Question 36

How many pairs of spinal nerves are there?

Answer 36

There are 31 pairs of spinal nerves.

Question 37

What type of information is transmitted through the ventral roots?

Answer 37

Motor information

Question 38

What is the dorsal root ganglion?

Answer 38

It contains cell bodies of sensory neurons. These are cell bodies of first order neurons.

Question 39

What are the types of spinal nerves?

Answer 39

``` Spinal nerves are nerves originating from the spinal cord that contain sensory and motor neurons. Each spinal nerve travels to a specific region / segment of the body. There are 31 pairs of spinal nerves and are named according to their origin: 8 pairs cervical (C1-C8) 12 pairs thoracic (T1-T12) 5 pairs lumbar (L1-L5) 5 pairs sacral (S1-S5) 1 pair coccygeal (C0) ```

Question 40

Where does the spinal cord extend from and where does it terminate? What are its features along its length?

Answer 40

The spinal cord extends from the foramen magnum at the base of the skull to the L1/L2 vertebrae where it terminates as the conus medullaris (medullary cone). A thin thread called filum terminale extends from the tip of the conus medullaris all the way to the 1st coccygeal vertebra (Co1) and anchors the spinal cord in place. Below L1/L2 the spinal nerves are bunched together as the cauda equina. Along its length, the spinal cord has two defined enlargements; a cervical enlargement and a lumbosacral enlargement.

Question 41

Why are there two well-defined enlargements along the length of the spinal cord?

Answer 41

They provide innervation to the limbs.

Question 42

What is a dermatome?

Answer 42

A dermatome is an area of skin that is supplied by a single spinal nerve and these nerves transmit sensations, such as pain, from the skin to the CNS. Dermatomes have a segmented distribution throughout the body. The exact dermatome pattern can vary from person to person and some overlap between neighbouring dermatomes may also occur.

Question 43

A patient is experiencing numbness across the lateral aspect of their shoulder below the clavicle, what spinal level do you think the injury is at?

Answer 43

C5

Question 44

Where on the hand would you test dermatome C8?

Answer 44

Little finger (5th digit)

Question 45

What do spinal nerves contribute to the formation of?

Answer 45

Spinal nerves contribute to the formation of plexi (singular: plexus).

Question 46

What is a plexus?

Answer 46

A plexus is a network of nerves that intermingle and become redistributed so that the peripheral nerve leaving the plexus contains fibres from multiple spinal nerve roots. Each limb muscle receives motor innervation from multiple spinal nerve roots.

Question 47

How many plexus groups branch off the spinal cord?

Answer 47

There are four main plexus groups. These are found in the cervical, brachial, lumbar and sacral regions of the spinal cord.

Question 48

What is the arrangement of nerves in the thoracic region?

Answer 48

Spinal nerves in the thoracic region are arranged segmentally and generally do not contribute to the plexi.

Question 49

What plexus supplies the upper limbs?

Answer 49

The brachial plexus

Question 50

What plexus supplies the lower limbs?

Answer 50

The lumbosacral plexus

Question 51

What are the features of the somatic nervous system?

Answer 51

Sensory impulses from the skins are relayed to the CNS via this nervous system Mainly acts on skeletal muscle Responsible for voluntary control of body movements

Question 52

What are the features of the visceral nervous system?

Answer 52

Acts on glands Sensory information comes from the internal organs Responsible for the involuntary control of bodily functions Acts on cardiac and smooth muscle Autonomic nervous system is the motor part of this system

Question 53

What is the function of the autonomic nervous system?

Answer 53

The autonomic nervous system (ANS) regulates body homeostasis. It in involuntary control of body processes such as breathing, heart beat and digestive processes. It can be divided into the sympathetic nervous system and the parasympathetic nervous system. Generally, the sympathetic nervous system prepares the body for stressful or emergency situations i.e. the fight or flight response. Whereas the parasympathetic nervous system controls body processes during ordinary situations i.e. the rest and digest response.

Question 54

What regions do the sympathetic and parasympathetic systems emerge from?

Answer 54

The sympathetic nervous system emerges from thoracolumbar regions and parasympathetic emerges from from craniosacral regions.

Question 55

What are the effects of the sympathetic nervous system?

Answer 55

``` Increases blood flow to skeletal muscles Dilates pupils Increases heart rate Inhibits stomach, pancreas and intestines Inhibits urination Stimulates ejaculation (in males) ```

Question 56

What are the effects of the parasympathetic nervous system?

Answer 56

``` Stimulates urination Stimulates saliva production Stimulates erection (in males) Constricts pupils Stimulates stomach, pancreas and intestines Slows heart rate ```

Question 57

What are the 4 main bones of the neurocranium?

Answer 57

Sphenoid Occipital Temporal Frontal

Question 58

What are sutures? What do they do?

Answer 58

Between the different bones of the skull are fibrous joints, called sutures. These sutures limit movement between the bones and tightly adhere the bones together.

Question 59

What are the names of the cranial sutures?

Answer 59

``` Coronal suture Pterion Squamous suture Lambdoid suture Sagittal suture ```

Question 60

Which bones are in the neurocranium (protect the brain)?

Answer 60

Frontal Parietal Occipital Temporal

Question 61

Which bones are in the viscerocranium (facial skeleton)?

Answer 61

``` Vomer Mandible Maxilla Palatine Zygomatic Lacrimal Inferior conchae ```

Question 62

Which bones are in both the neurocranium and the viscerocranium?

Answer 62

Ethmoid | Sphenoid

Question 63

What are the cranial fossae?

Answer 63

On the internal aspect of the skull there are 3 regions, called the anterior, middle and posterior cranial fossa.

Question 64

What are the foramina?

Answer 64

The skull contains many foramina (holes) which allow the passage of structures, such as blood vessels and nerves into and out of the skull.

Question 65

What is the cribiform plate?

Answer 65

The cribiform plate is part of the ethmoid bone, and has lots of tiny perforations.

Question 66

What is the optic canal?

Answer 66

This is the hole for the optic nerve to pass through.

Question 67

What is the foramen ovale?

Answer 67

Literally means oval hole. This creates a passageway for a nerve.

Question 68

What is the jugular foramen?

Answer 68

This allows passage of the internal jugular vein

Question 69

What is the foramen rotundum?

Answer 69

Literally means round hole.

Question 70

What is the foramen mangum?

Answer 70

This is the largest foramen on the base of the skull and allows the passage of the brainstem.

Question 71

Which suture separates the frontal and parietal bones?

Answer 71

Coronal suture The coronal suture runs in the coronal plane (dividing the body into an anterior and posterior). Coronal means crown, and so is were you wear a crown (on top of your head) and divides the frontal and parietal bones.

Question 72

Which bone houses the inner ear?

Answer 72

Temporal The external acoustic meatus can be seen on the external surface of the temporal bone, this is the entrance to the middle and inner ear, which are located within the temporal bones.

Question 73

Which bone links the facial skeleton to the neurocranium?

Answer 73

Sphenoid

Question 74

What is the sternum? What are its different parts?

Answer 74

The sternum is the breastbone. It is made up of 3 parts. Superiorly is the manubrium, which articulates with the clavicles. The body of the sternum articulates with the costal cartilages of the ribs. Between the manubrium and the body is a prominent joint, the sternal angle (or angle of Louis) this forms a lump you can palpate on your chest. The xiphoid process is a small cartilaginous projection at the inferior aspect of the sternum. This often ossifies with age.

Question 75

How many pairs of ribs are there?

Answer 75

12

Question 76

What are the true ribs?

Answer 76

Ribs 1-7 attach to the sternum directly via their costal cartilage. These ribs are termed true ribs.

Question 77

What is the costal margin?

Answer 77

The boarder created by the costal cartilages of ribs 8-10 joining the 7th costal cartilage is called the costal margin. This is palpable.

Question 78

What are false ribs?

Answer 78

Ribs 8-10 attach to the sternum via the 7th costal cartilage. They are therefore called false ribs.

Question 79

What are floating ribs?

Answer 79

Ribs 11 and 12 do not attach to the sternum and so are called floating ribs.

Question 80

How many bones make up the vertebral column?

Answer 80

The vertebral column is typically made up of 33 Individual vertebral bones, articulating together to protect the spinal cord whilst allowing for movement of the column.

Question 81

What are the five regions of the vertebrae?

Answer 81

For descriptive purposes the vertebrae are divided into 5 regions; 1) Cervical (7 bones) 2) Thoracic (12 bones) 3) Lumbar (5 bones) 4) Sacral (5 bones, fused) 5) Coccygeal (4 bones)

Question 82

What

Answer 82

Cervical (rounded with a large foramen) Thoracic (looks like a giraffe) Lumbar (looks like an octopus) Sacral (has wings)