Module 5 - Introduction to the neuroanatomy of the CNS and PNS - Original slides

Question 1

The nervous system is divided into two major subdivisions: the ____________________, that consists of the _________ and the ____________, and the __________________, the most obvious components of which are the_______________and _______________.

Answer 1

The nervous system is divided into two major subdivisions: the central nervous system (CNS), that consists of the brain and the spinal cord, and the peripheral nervous system (PNS), the most obvious components of which are the spinal and cranial nerves.

Question 2

The functional unit of both the CNS and PNS is the ______________. Neurons possess: ______________ that contains the _________ and ______________ and have projection either carrying electrical signals towards (___________) or away (___________) from the ______. Neurons communicate with each other via _________, with output at ___________and inputs onto __________.

Answer 2

The functional unit of both the CNS and PNS is the neuron (or nerve cell). Neurons possess: a soma (or cell body) that contains the nucleus of the cell and other cellular machinery and have projection either carrying electrical signals towards (dendrites) or away (an axon) from the soma. Neurons communicate with each other via synapses, with output at axon terminals and inputs onto dendrites.

Question 3

Many axons are covered in ______, formed by ____________. In the CNS the cells are ______________; in the PNS they are called _________. Myelin provides electrical insulation allowing the electrical signal in the cell body to reach the axon terminal (and do so quickly).

Answer 3

Many axons are covered in myelin, formed by glial cells. In the CNS the cells are oligodendrocytes; in the PNS they are called Schwann cells. Myelin provides electrical insulation allowing the electrical signal in the cell body to reach the axon terminal (and do so quickly).

Question 4

The relative amount of myelin within a region of the nervous system is indicative of the presence of axons. Regions with a lot of myelin indicate collection of fibres and, because of their appearance in dissected brains, came to be called __________________ In contrast, regions with little myelin generally indicate a greater density of somas, and came to be called ___________.

Answer 4

The relative amount of myelin within a region of the nervous system is indicative of the presence of axons. Regions with a lot of myelin indicate collection of fibres and, because of their appearance in dissected brains, came to be called white matter. In contrast, regions with little myelin generally indicate a greater density of somas, and came to be called gray matter.

Question 5

In the cerebral hemispheres gray matter is found on the ___________of the brain with white matter ____________.

In the spinal cord, gray matter is found _____________ and is ___________ by white matter.

Answer 5

in the cerebral hemispheres gray matter is found on the surface (cortex) of the brain with white matter beneath.

In the spinal cord, gray matter is found centrally and is surrounded by white matter.

Question 6

A collection of neurons with similar structure and function are called

1- _____________ (plural = ?) - within …..

2- _____________ (plural = ?) outside …..

Answer 6

A collection of neurons with similar structure and function are called

1- Nucleus (plural = nuclei) - within the CNS (but you can contain neurons that are part of the PNS)

2- Ganglion (plural = ganglia) outside the CNS and part of the PNS

Question 7

IDENTIFY.

Answer 7

Question 8

The outer surface (cortex) of both the cerebrum and the cerebellum can be thought of as sheets of tissue, but the sheets are extensively folded (_____________) allowing increased surface area within a three-dimensional space. In the cerebrum, the folds form ________(______ ________) separated by _______ (______ _______). In the cerebellum, the corresponding terms are ____________ and __________.

Answer 8

The outer surface (cortex) of both the cerebrum and the cerebellum can be thought of as sheets of tissue, but the sheets are extensively folded (convolutions) allowing increased surface area within a three-dimensional space. In the cerebrum, the folds form gyri (singular gyrus) separated by sulci (singular sulcus). In the cerebellum, the corresponding terms are folia and fissures.

Question 9

IDENTIFY.

Answer 9

Question 10

IDENTIFY.

Answer 10

Cerebrum
Cerebellum
Spinal cord
Brainstem
Medulla
Pons
Midbrain
Diencephalon
Thalamus
Hypothalamus

Question 11

IDENTIFY.

Answer 11

Question 12

Each cerebral hemisphere is subdivided into lobes. Visible laterally is: ____________that is separated from the ____________ by the ______________. The ______________ is inferior to the ___________ and portions of the __________and largely (but not completely) separated by the __________________(________________). Note that there is not always a sulcus that clearly or completely separates the lobes.

Answer 12

Each cerebral hemisphere is subdivided into lobes. Visible laterally is: the frontal lobe that is separated from the parietal lobe by the central sulcus (of Rolando). The temporal lobe is inferior to the frontal lobe and portions of the parietal lobe and largely (but not completely) separated by the Sylvian fissure (or lateral sulcus). Note that there is not always a sulcus that clearly or completely separates the lobes.

Question 13

On the medial surface there is a sulcus separating the parietal and occipital lobe. Sometimes anatomy is easy and obvious! This sulcus is called the ______________________.

But there is another lobe, more recently defined and more functionally than anatomically, _____________

Answer 13

on the medial surface there is a sulcus separating the parietal and occipital lobe. Sometimes anatomy is easy and obvious! This sulcus is called the parieto-occipital sulcus.

But there is another lobe, more recently defined and more functionally than anatomically, the limbic lobe.

Question 14

The ______________ is a large (in fact, the largest) collection of white matter that connects the cerebral hemispheres. If you were to place your finger into the medial longitudinal fissure your finger tips would touch the __________.

Answer 14

The corpus callosum is a large (in fact, the largest) collection of white matter that connects the cerebral hemispheres. If you were to place your finger into the medial longitudinal fissure your finger tips would touch the corpus callosum.

Question 15

The ____________ or __________, covered by _________ of frontal, parietal and temporal lobes. Consists of __________.

Answer 15

The insular lobe or insula, covered by opercula of frontal, parietal and temporal lobes. Consists of long and short gyri.

Question 16

IDENTIFY.

Answer 16

Question 17

IDENTIFY.

Answer 17

Question 18

The spinal cord gives rise to ____________________that are named in relation to the adjacent vertebrae (cervical, thoracic, lumbar, sacral) through which they exit (intervertebral foramina). There are two regions where the spinal cord is expanded, ______________________________. These regions are enlarged because at these levels the spinal nerves, that innervate the upper or lower limb, contain a lot of fibers.

Answer 18

The spinal cord gives rise to 31 pairs of spinal nerves that are named in relation to the adjacent vertebrae (cervical, thoracic, lumbar, sacral) through which they exit (intervertebral foramina). There are two regions where the spinal cord is expanded, the cervical and lumbar enlargements. These regions are enlarged because at these levels the spinal nerves, that innervate the upper or lower limb, contain a lot of fibers.

Question 19

What ends around L1/L2 vertebral level?

Answer 19

Spinal cord called conus medullaris

Question 20

Fibres (roots) that form spinal nerves below L1/L2 vertebral level that have exited from the spinal cord from levels at or above the conus medullaris, form the _____________.

Answer 20

Fibres (roots) that form spinal nerves below this level, that have exited from the spinal cord from levels at or above the conus medullaris, form the cauda equina.

Question 21

The cervical region of the spinal cord is adjacent to ________vertebrae; the thoracic region is adjacent to _______ vertebrae; the lumbar region is adjacent to ______; and the sacral region is adjacent to _______

Answer 21

the cervical region of the spinal cord (purple in the diagram) is adjacent to C1-C8 vertebrae; the thoracic (green) region is adjacent to T1-T11 vertebrae; the lumbar (blue) region is adjacent to T12; and the sacral (red) region is adjacent to L1/L2.

Question 22

What kind of fibres are found in spinal nerves?

In the peripheral nervous system, the most basic classification of fibres is ____________ (________) vs. _________ (__________). These can be further subdivided into __________ (___________________________) and ________ (_____________) components.

Answer 22

What kind of fibres are found in spinal nerves?

In the peripheral nervous system, the most basic classification of fibres is motor (efferent) vs. sensory (afferent). These can be further subdivided into somatic (outer part of the body, muscles, skin, mucosa) and visceral (inside the body) components.

Question 23

There are two kinds of motor (efferent) fibres in spinal nerves:

1. ____________________
2. _________________

The fibres that constitute the ________are also part of the autonomic nervous system.

Answer 23

There are two kinds of motor (efferent) fibres in spinal nerves:

1. General Somatic Efferent (GSE) fibres, that innervate skeletal muscle, and 2. General Visceral Efferent (GVE) fibres, that innervate smooth muscle (e.g. arteries, gut) and glands. The fibres that constitute the GVE are also part of the autonomic nervous system.

Question 24

Spinal nerves also contain two types of sensory (afferent) fibres.

First, ……???

Second, …..???

Answer 24

Spinal nerves also contain two types of sensory (afferent) fibres.

First, General Somatic Afferent (GSA) fibres (for the sensation of pain, temperature and touch and body position in
space, called proprioception). Mostly for conscious sensation, but proprioception also operates at an unconscious level to coordinate motor control.

Second, General Visceral Afferent (GVA) fibres, mostly unconscious (controlling internal visceral functions like, gut activity, but can be conscious (and even painful) under certain conditions (hunger, nausea, bladder fullness, etc.)

Question 25

GSE fibres arise from neurons in the _____________ of the spinal cord (gray matter). Although within the gray matter of the spinal cord, these neurons are part of the PNS. The axons exit as ________________ and join with the posterior (dorsal) roots (sensory fibres) as part of the spinal nerve.

Answer 25

GSE fibres arise from neurons in the anterior (ventral) horn of the spinal cord (gray matter). Although within the gray matter of the spinal cord, these neurons are part of the PNS. The axons exit as anterior (ventral) roots and join with the posterior (dorsal) roots (sensory fibres) as part of the spinal nerve.

Question 26

GSE neurons in the spinal cord are examples of what are called _____________________. They receive input from __________________that are located in the CNS (e.g. primary motor area in the frontal lobe of the cerebrum).

Answer 26

GSE neurons in the spinal cord are examples of what are called lower motor neurons (LMNs). They receive input from upper motor neurons (UMNs) that are located in the CNS (e.g. primary motor area in the frontal lobe of the cerebrum).

Question 27

FILL IN THE BLANKS

Answer 27

Question 28

Numerous posterior (dorsal) roots travel from the DRG to the spinal cord, but depending on the sensory modality, enter either spinal cord white matter (_______________) or gray matter (____________).

Answer 28

Numerous posterior (dorsal) roots travel from the DRG to the spinal cord, but depending on the sensory modality, enter either spinal cord white matter (to travel up the spinal cord) or gray matter (posterior horn).

Question 29

What about the visceral components?
I already mentioned that the GVE system is a part of the ____________________.This can be subdivided into two subdivisions: __________________ and _______________ In both cases, these involve a chain of two neurons: a _________________ that then contacts a ________________.

Answer 29

What about the visceral components?
I already mentioned that the GVE system is a part of the autonomic nervous system. This can be subdivided into two subdivisions: sympathetic and parasympathetic. In both cases, these involve a chain of two neurons: a pre-ganglionic neuron that then contacts a post-ganglionic neuron.

Question 30

All sympathetic arise from the spinal cord over levels ___________. Pre-ganglionic neurons are found in the________________ (sometimes called the ____________) of the spinal cord gray matter.

Answer 30

Let’s first look at the sympathetics. All sympathertics arise from the spinal cord over levels T1- L1/L2. Pre-ganglionic neurons are found in the intermediolateral nucleus (sometimes called the lateral horn) of the spinal cord gray matter.

Question 31

IDENTIFY.

Answer 31

Question 32

Axons from pre-ganglionic neurons exit the cord via ___________________, and join the spinal nerve. But they soon exit the spinal nerve via the ____________ and enter the _____________.

Answer 32

Axons from pre-ganglionic neurons exit the cord via the anterior (ventral) roots, and join the spinal nerve. But they soon exit the spinal nerve via the white ramus and enter the sympathetic chain ganglia.

*******The white ramus is so-named because the fibres here are myelinated.

Question 33

The _____________________ runs adjacent (on each side) the whole lengths of the vertebral column.

Answer 33

The sympathetic ganglia runs adjacent (on each side) the whole lengths of the vertebral column.

Question 34

At this point the anatomy of the sympathetic system depends on the ultimate target. In the simplest case, the __________axon synapses with a _________neuron within the sympathetic chain ganglion.

The axon of the _________neuron then returns to the spinal nerve via the _________ (_________) and these fibres travel to ______________ (to innervate ________, __________ and ___________).

Answer 34

At this point the anatomy of the sympathetic system depends on the ultimate target. In the simplest case, the pre-ganglionic axon synapses with a post-ganglionic neuron within the sympathetic chain ganglion.

The axon of the post-ganglionic neuron then returns to the spinal nerve via the gray ramus (unmyelinated) and these fibres travel to targets in the skin (to innervate glands, arteries, piloerector muscles).

Question 35

Alternatively, ____-ganglionic sympathetics exit the ganglia, projecting to the ___________(___________________) or …

…______-ganglionic sympathetics travel through the chain ganglion, without synapsing, and are
carried to ________via _________…

…where they synapse with post-ganglionic neurons within the visceral ganglia. Post-ganglionic neurons give rise to axons that project to ________ _________(inhibits ________ constricts __________ relaxes __________, stimulates ________, etc.)

Answer 35

Alternatively, post-ganglionic sympathetics exit the ganglia, projecting to the heart as cardiac nerves (that accelerates the heart) or …

…pre-ganglionic sympathetics travel through the chain ganglion, without synapsing, and are
carried to visceral ganglia via splanchnic nerves…
(Visceral ganglia include celiac, superior mesenteric, and inferior mesenteric ganglia.)

…where they synapse with post-ganglionic neurons within the visceral ganglia. Post-ganglionic neurons give rise to axons that project to target viscera (inhibits digestion, constricts gut arteries, relaxes urinary bladder, stimulates ejaculation, etc.)

Question 36

Lastly, _____-ganglionic sympathetics emerge from ________ of sympathetic chain ganglion (_________and _______ _________ganglia) and go to the head travelling with arteries (dilates pupil, inhibits salivary glands, etc.)

Answer 36

Lastly, POST-ganglionic sympathetics emerge from upper part of sympathetic chain ganglion (superior and inferior cervical ganglia) and go to the head travelling with arteries (dilates pupil, inhibits salivary glands, etc.)

Question 37

A few spinal nerves also have parasympathetic components: _______________________

Answer 37

A few spinal nerves also have parasympathetic components: the S2-S4 spinal nerves.

Question 38

Pre-ganglionic parasympathetics arise from neurons in the ___________ region of ________ spinal cord _______ matter. Their axons project via the ______________, join the spinal nerves…

… but then branch off and give rise to _______ ___________ ______ that form synapses with post- ganglionic neurons within ganglia near target end organs (dilates arteries in distal gut, stimulates urinary bladder contraction, stimulates erection, etc.)

Answer 38

Pre-ganglionic parasympathetics arise from neurons in the intermediate region of S2-S4 spinal cord gray matter. Their axons project via the anterior (ventral) roots, join the spinal nerves…

… but then branch off and give rise to pelvic splanchnic nerves that form synapses with post- ganglionic neurons within ganglia near target end organs (dilates arteries in distal gut, stimulates urinary bladder contraction, stimulates erection, etc.)

Question 39

The other major component of the PNS are the cranial nerves. Most (but not all) are connected with the ________ and associated with _________ _________.

For various reasons, CN II, the ______ _________, is actually considered to be part of the CNS. It really should be considered a _______ ________ _______. (There are some suggestions that CN I, the ____________ ______, is also part of the CNS.)
One other oddity is that CN XI, the ________ ___________ _________, contains fibres derived not from the brain but from the cervical spinal cord.

Answer 39

The other major component of the PNS are the cranial nerves. Most (but not all) are connected with the brainstem and associated with brainstem nuclei.
For various reasons, CN II, the optic nerve, is actually considered to be part of the CNS. It really should be considered a white matter tract. (There are some suggestions that CN I, the olfactory nerve, is also part of the CNS.)
One other oddity is that CN XI, the spinal accessory nerve, contains fibres derived not from the brain but from the cervical spinal cord.

Question 40

What are the 9 cranial nerves that are clearly associated with the brainstem?

Answer 40

CN III and IV = midbrain

CN V = pons
CN VI to VIII = pons-midbrain border

CN IX, X and XII = medulla

Question 41

Cranial nerves can contain one or more of the 4 functional fibres types associated with spinal nerves:

1.

2.

3.

4.

***Cranial nerves CAN contains one or more of each - but rarely all 4 types.

Answer 41

Cranial nerves can contain one or more of the 4 functional fibres types associated with spinal nerves:

1. GSE
2. GVE
3. GSA
4. GVA

***Cranial nerves CAN contains one or more of each - but rarely all 4 types.

Question 42

Certain cranial nerves also contain one or more of three additional “special” fibre types:

1. ___________________…
2. ___________________…
3. ___________________…

Answer 42

1. Special somatic afferents (SSA; vision, hearing, balance)
2. Special visceral afferents (SVA; smell, taste)
3. Special visceral efferents (SVE; sometimes called branchial motor; innervates certain muscles in the head & neck that have a different developmental origin than muscles of the trunk and limbs)

Question 43

There are some parallels of cranial nerves with spinal nerves.

• The motor neurons (GSE and SVE) that contribute axons to certain cranial nerves are considered __________ _________ ________ (__________________________________). They receive input from _________ __________ ___________.
• There are ______ associated with cranial nerves that carry sensory information (e.g. __________ _________).
• There are also_______ associated with cranial nerves that carry_____ (____example_________________……)

Answer 43

There are some parallels of cranial nerves with spinal nerves.

• The motor neurons (GSE and SVE) that contribute axons to certain cranial nerves are considered lower motor neurons (like the lower motor neurons of the spinal cord). They receive input from upper motor neurons.
• There are ganglia associated with cranial nerves that carry sensory information (e.g. trigeminal ganglia).
• There are also ganglia associated with cranial nerves that carry GVE (all parasympathetic, e.g. ciliary ganglion for innervation of the pupil by CN III).

Question 44

Please draw an image of the anatomy and explain the functions of the cranial nerves.

Answer 44

Question 45

What are the cranial nerves?

Answer 45

Mnemonic # 1 = On occasion our trusty truck acts funny, very good vehicle any how

***Some say marry money but my brother says big brains matter more