Introduction to Neuroanatomy Flashcards
(114 cards)
1
Q
What is the diencephalon made up of?
A
- Thalamus
- Hypothalamus
2
Q
What are the 3 sections of the brain?
A
- Forebrain
- Midbrain
- Hindbrain
3
Q
What are the 2 parts which makes up the forebrain?
A
- Diencephalon
- Cerebral Hemispheres
4
Q
What makes up the brainstem?
A
- Midbrain
- Pons
- Medulla
5
Q
What are the different ventricles?
A
- 2x Lateral Ventricle
- Third Venitrcle
- Fourth Ventricle
Circulation of CSF –> called Hydrocephalus
NB: There is no such thing as a second ventricle
6
Q
What is the equivalent of a ‘nerve’ from the PNS in the CNS?
What is the equivalent of a ‘ganglion’ found in the PNS in the CNS?
A
- A nerve is called a ‘tract’ in the CNS
- A ganglion is called a ‘nucleus’ in the CNS
Ganglion = Nucleus –> these are a GROUP of NEURONAL CELL BODIES
NB: Synapses are always one way
7
Q
Which is inhibitory and which is excitatory between;
- Glutamate
- GABA
A
Glutamate –> EXCITATORY (+)
GABA –> INHIBITORY (-)
Glutamate is the most common excitatory neurotransmitter in the body
Glutamate –> is also what kills the neurones during old age due to excitotoxicity (too much)
Glutamate will INCREASE the CHANCES of a NEURONE being TRIGGERED (post-synaptic)
8
Q
What does a neurone projecting somewhere mean?
A
A neurone ‘projecting’ to somewhere is the same as a neurone ‘sending an axon’ to somewhere
9
Q
What is meant by a collateral?
A
Collateral - this is a branch of an axon
Dendrites –> these RECEIVE INFORMATION
Axons –> MOST have COLLATERALS which BRANCH therefore sending SIGNALS to 2 or MORE PLACES
10
Q
Briefly describe the development of the neural system
A
- Neural plate epithelium –> FOLDS
- This forms a GROOVE (becomes invaginated)
- The GROOVE then forms a NEURAL TUBE leaving NEURAL CRESTS and becoming DISCONNECTED from the EPITHELIUM
Neural Tube –> forms the CNS
Neural Crest –> forms the PNS (glial cells too)
NB: Neural Crests from from the EDGES
11
Q
What causes Anencephaly and Sina Bifida?
A
- When the neural tube does not close
- Should be closed in the 1st Month
- Folic Acid needs to be taken BEFORE pregnancy is confirmed to reduce risk (not helpful during pregnancy)
12
Q
What does the Neural Tube of the embryo form?
A
- Forms the CNS
- Rostral Head –> expands to form the brain
13
Q
Which part of the neural tube expands to form the head?
What 4 parts can this bit be split into?
A
Rostral (Head End)
- Forebrain Vesicle
- Midbrain Vesicle
- Hindbrain Vesicle
- Spinal Cord
Brain vesicles at rostral (head) end of the neural tube
NB: It is ‘Vesicle’ and not ‘Ventricle’
14
Q
There are 2 outgrowths from the forebrain vesicle. What are they?
A
- Telencephalon (with 2 outgrowths itself)
- Diencephalon (original forebrain)
15
Q
What are the 2 outgrowths from the telencephalon?
A
- These are the cerebral hemispheres
(Think of it like tele has 2 antennas)
16
Q
What is does the original forebrain vesicle become (other than outgrowths/telencephalone)?
A
- Diencephalon (hypothalamus & thalamus)
17
Q
Where is the lateral ventricle found?
A
- There is one in each cerebral hemisphere
- Lateral ventricle extends into each part of the hemispheres
- It opens into the 3rd ventricle via the Interventricular Foreamen
- Seen on a Median Sagital Sections (because it is within the hemispheres)
They each connect to the Third Vesicle via an Intraventricular Foramen
18
Q
Where is the third ventricle found?
A
- Found in the diencephalon (including hypothalamus & thalamus)
- Found in between THALAMUS & HYPOTHALAMUS
Diencephalon –> ANYTHING which has ‘Thalamus’ in it is part of this
Diencephalon –> part of the FOREBRAIN
19
Q
What is a ventricle?
A
This is a fluid-filled structure which contains Cerebral Spinal Fluid (CSF)
20
Q
In a summary, what are the different parts of the adult brain and their function?
A
- Brainstem (including pons & midbrain & medulla oblongata)
- Medulla = Medulla Oblongata
- Pons –> is SWOLLEN & BULKY compared to Medulla
*
21
Q
Give a summary of the pons
A
- Swollen
- More bulky than the Medulla
- Intimately linked to the cerebellum on the back of it
- Pons –> linked to cerebellum via middle peduncle
- Above it is the midbrain (from the midbrain vesicle)
NB: Midbrain is derived from the midbrain vesicle
22
Q
What does the Cerebellum do?
A
- Coordination of Movement (prime function)
- Other things (balance & posture)
23
Q
Summary of the brainstem
A
Brainstem is in charge of:
- Heart Rate
- Breathing
- Blood Pressure
- Most Main functions of life
- It also gives 10 of the 12 cranial nerves (therefore without brain stem we would be brain dead)
- Brainstem –> CONTINUOUS with the SPINAL CORD
24
Q
Describe CSF exit circulation.
A
- CSF enters subarachnoid space
- CSF goes to superior sagital sinus
- Superior sagital sinus goes around the top of the brain
- It leaves via the Arachnoid Villi (granulations) and drains into the blood vessel called Superior Sagital Sinus
25
What is the 4th Ventricle?
* Found between **Cerebellum** & **Brainstem (pons)**
* The 4th Ventricle has a median & lateral aperture
26
Where is CSF made?
* **CSF** is mainy made in the **Lateral Ventricle**
* It then goes **via** the **Interventricular Foramen** to the **3rd Ventricle**
* It then goes down a **tube** called the **cereberal aquaduct** to the **4th Ventricle**
* Made by **Choroid Plexuses** largely in Lateral Ventricle
* **_Lateral_ Ventricle** --\> found in both **Cerebral Hemispheres**
*
27
Where does the CSF exit?
* **CSF** goes to the **4th Ventricle**
* **CSF** goes to the **Subarachnoid Spaces**
* CSF then **exits** via **Arachnoid Villi/Granulations** in the **Superior Sagital Sinus**
* Some CSF will **leak** **out** to the **cranial spinal section & beyond**
* This provides the CSF for the **spinal cord**
28
What is special about the Superior Sagittal Sinus?
It is the **main** **vessel** for the **cerebral cortex drainage**
29
Importance of CSF functionally?
* Important for the **protection** of the brain
* CSF flows around the brain
30
What happens if there is a **blocked aqueduct**?
Who does this usually occur to?
* Stenosis of the Cerebral Aqueduct can occur in babies (born this way)
* CSF continues to be produced in the Lateral Ventricles (and other ventricles)
* This causes ventricles to expand
* Inability to flow down the aqueduct to the 4th ventricle
* Inability to go to the subarachnoid space
* This causes **hydrocephalus**
31
What is the condition that cerebral aqueduct stenosis can cause?
* Hydrocephalus (swelling of brain ventricles)
32
What must you be careful when doing surgery from behind?
* Superior Sagital Sinus (largest near the back)
* Therefore damage can occur here
* However operations from the back do not have as much CSF than when approaching from the cerebellum direction (below)
33
Hydrocephalus
Which ventricles would swell if aqueduct is blocked?
* Predominantely Lateral Ventricles (main ones that form CSF)
* Occurs due to Stenosis of Cerebral Aqueduct
34
What occurs in **Hydrocephalus**?
1. **Stenosis of Cerebral Aqueduct** --\> causing **blockage**
2. CSF **continues to be produced** in **lateral** **ventricles** (predominantely)
3. **Cannot** flow down **aqueduct**
4. Cannot reach the **sub-arachnoid space**
5. Causes **lateral ventricles** to **swell up**
6. Causing brain to get **squashed from the inside**
There is **no space** in the **extra-cranial cavity** --\> therefore brain tissue is **pushed out against skull bone**
* **Dark Spaces on Axial MRI --\>** shows the **Ventricles**
* **Lateral Ventricle** --\> shown as **L-FISSURE**
35
What is the solution for hydrocephalus?
What does it involve?
* Neurosurgery
* **Plastic Tube** called a **_shunt_** is placed into **lateral ventricle**
* This tube goes down to **peritoneal cavity**
* This allows **CSF** to **drain into peritoneal cavity**
It is important that this surgery is done soon after birth to prevent brain damage problems
36
What are the **cerebellar peduncles** and what do they do?
* Found on **either side** of the **midline** (para-sagittal)
* **Not seen in sagittal** (midline sections)
* Connect **_cerebellum_** and **parts of the brainstem** via **3 peduncles**
* Peduncle is like a **'stalk-like'** structure
* There is a **superior**, **middle** & **inferior** peduncle
Para-Sagital: Found on **either side** of the **midline**
Neurones go **_TO_** & **_FROM_** the **brainstem** & **cerebellum** via the **peduncles**
**NB**: Middle peduncle has 20 million axons going through it between the pons & cerebellum
37
Where are the **superior** & **inferior** **colliculus** located and what are their general functions?
* Found in the **midbrain**
* **_Superior_** **Colliculus** --\> Eye Movement
* **_Inferior_** **Colliclus** --\> Hearin
38
Which **peduncle** is linked to which **part of the brainstem**?
* **Superior** Cerebellar Peduncle --\> connects **MIDBRAIN** & CEREBELLUM
* **Middle** Cerebellar Peduncle --\> connects **PONS** & CEREBELLUM
* **Inferior** Cerebellar Peduncle --\> connects **MEDULLA** & CEREBELLUM
NB: Pons is a bit swollen and has its back in contact with cerebellum
The floor of the 4th ventricle on the brainstem is diamond-shaped
39
What are the **layers of the meninges** that cover the **_brain_** & **_spinal cord_**?
* **Dura** (outside) --\> very thick
* **Arachnoid** (middle) --\> attached to the inside of dura
* **Pia** (inside) --\> quite thin
**Dura & Arachnoid** --\> has no/little space --\> it is just **'potential space'** if something goes wrong (**middle meningeal bleed)**
40
What is the **denticulate ligament**?
* Sits between the **_ARACHNOID_** & **_PIA MATTER_**
* Between these two layers the **Subarachnoid** **Space** is formed
* Keeps the **PIA DURA** in place
* **Subarachnoid** **space** contains **CSF**
* **CNS** floats in **CSF**
* **Arteries** supplying the **CNS** --\> are in the **SUBARACHNOID** **SPACE** --\> which are **surrounded** by **CSF**
*
41
What is the subarachnoid space and why is it important?
* Space between **_PIA MATER_** & **_ARACHNOID_** LAYER
* Has lots of space for **Spinal Nerves**
* **Contains CSF** (similar composition to water + salts)
* **Arteries** supplying the **Spinal cord** are found in the **subarachnoid space** --\> therefore **bleeding** occurs in the s**ubarachnoid space** into the **CSF**
42
Where is the **dentrospinal** **artery** found and what does it do?
* Found in the **Subarachnoid Space**
* Supplies the **spinal cord**
* If it **bleeds** --\> goes into the **CSF**
43
What happens if there is **too** **much** **loss** of **CSF**?
* **Loss of Protection** (CSF needed for brain & spinal cord to be surrounded by to float in & keep them alive - content)
* Spinal cord would **collapse** **on itself** --\> the structure would **cave in** as it needs **something to float in**
CSF is soft and allows brain to sit in it
44
What happens if there is a **middle** **meningeal** **bleed**?
* Found between the **Dura** & **Arachnoid**
* There is **no real space** here but simply **'potential space'**
* **Blood** is found here if there is a **bleed** (usually nothing here)
45
What happens if there is **bleeding of arteries** supplying the **spinal** **cord**?
* These **arteries** are found in the **subarachnoid space**
* Therefore **bleeding** will cause blood to go into **CSF**
* This causes **murky CSF**
46
Myelination of spinal cord. What is myelinated and how does it appear?
* **Grey** Matter --\> contains **Neural Cell Bodies** (mainly)
* **White** Matter --\> contains **Myelinated Cell Axons** (mainly)
**Grey Matter** --\> is not stained but rather the myelin of oligendrocytes (CNS) surrounding the axons in the white matter are.
47
Why is white matter most abundant in the cervical cord and least in the sacral cord?
This is because nearer to the top there is a lot of axons which have come into the spinal cord by now. Therefore, there is going to be a lot of axons in the ascending & desending tracts making white matter a lot more here.
Sacral Region: Most axons would have either been given off by then or very few (just from lower reaches of body) have been inputted therefore little ascending & descending tracts in white matter here.
48
What does the **dorsal** horn & root contain?
Dorsal Horn & Root --\> contains SOMATOSENSORY
49
What does the **ventral** horn & root contain?
**Ventral** Horn & Root --\> contains MOTOR NEURONES
50
What is the **central** **canal** and why can it be helpful?
Where did it come from?
* **Middle** of Spinal Cord --\> is the **CENTRAL CANAL**
* This does **_not_** have **CSF** in it
* **Embryonic remnants** from what used to be the **neural tube**
* Find **stem cells** here --\> however they do **_not_** grow neurones if someone **damages their CNS** (spinal cord part)
51
What is **lateral** & **ventral** **white** **matter**?
* These are the **ascending** & **descending** **tracts** (depending on where abouts in the white matter)
* There are **_no_ physical barriers/boundaries** between them
52
What is the **distribution** of the **ventral (anterior) spinal artery**? (important)
Are **strokes** of this artery common?
Which parts of the spinal cord are **affected**?
* **_Not_** **common** but they **do** **occur**
**Stroke (lesion of artery)** can cause loss of blood to:
1. **Great Descending Motor Tracts** --\> therefore PARALYSES for THAT LEVEL & BELOW
2. **Ascending Pain Pathways** --\> LOSS of PAIN SENSATION (somatosensory)
Loss of Blood supply leads to death & destruction of the areas
53
What are **radicular** **arteries** and why are they important?
* Supply the **spinal** **arteries** (including ventral spinal artery)
* **Run** **along** the **spinal** **roots** (thus called radicular)
Blockages of these can cause problems for spinal arteries and have similar effect as a stroke in the ventral (anterior) spinal artery (i assume)
54
What is special about the **Left** **T10 level** in terms of **blood supply**?
* This **spinal** **artery** is **particularly large**
* Called **Adamkiewicz**
* Can be used as a **landmark**
* Need to ensure it is **_not_** **damaged** in **surgery**
55
What is **grey** **matter** in the spinal cord **divided into**?
* Divided into **Laminae of Rexed**
* These are **laminae form I-VI (6)** found in the **dorsal horn**
* Dorsal Horn --\> mainly **somatosensory**
56
Which layers does the **superficial dorsal horn** include and what **somatosensory function** is involved here?
* **Superfiical Dorsal Horn** --\> includes **Lamina I & II**
* These laminae are important for **Pain (nociception)**
57
What is another name for **Lamina II** and what is found there?
* **Substantia Gelatinosa**
* Contains lots of **small** **neurones**
* Found in **Superficial Dorsal Horn**
58
Why is the **cerebral** cortex important in **pain?**
* If you do **not** have **cerebral cortex** --\> you **_cannot_** **conceptualise** **pain** --\> so you **_cannot_** **feel it (perceive it)**
59
What are **nociceptors**?
* **Detection** of **Noxious Stimuli**
* This occurs **all** **over** the **body**
* This is **_not_** the same as pain
**Pain** is a **construct of the cerebral cortex** --\> whereas **nociception** is the **pain stimuli** --\> which is **conducted back to the brain** and interpreted as **'pain'**
60
What is found in **Lamina IX**?
Explain the **distribution**? (e.g. medial & lateral parts)
* **Lamina 9 (XI)**
* These are **Motor** **Neurones**
* Most **_Medial_** **Motor** **Neurones** --\> supply **TRUNK MUSCLES**
* Most **_Lateral_** **Motor** **Neurones** --\> supply **EXTREMITIES** (hands & feet)
Axons that **LEAVE** the **VENTRAL** **_ROOT_** --\> go into the **SPINAL** **NERVE** then head **DORSALLY** down the **DORSAL** **_RAMUS_** (mixed nerve) to the **BACK** **MUSCLES** (e.g. erector spinae)
61
Where are **pre-ganglionic sympathetic neurones** found?
- Lamina?
- Parts of Spinal Cord?
* Found in the **Lateral Horn**
* Found in **Lamina VII (7)**
* Only found in **Thoraco-Lumbar Parts**
62
What is a **Lower Motor Neurone Lesion**?
How can this occur?
What are **examples** of **nerve injury** which can cause a **LMNL**?
* **Injury** to **Peripheral** **Nerves**
* This can be caused by **poliomyelitis** (epidemics occur)
Can occur due to:
1. The **death** of the **cell body**
2. **Peripheral** **Damage** to **_Axon_** (along its course) at any part
63
What does Poliomyelitis do?
* **Virus**
* **Epidemics** can occur
* **Virus** kills the **_motor_** **neurones** causing **paralysis** if **_enough_** **neurones** are **killed**
Virus is usually found in the gut during normal health
64
How can the body **fix** **PNS** **damage**?
* **Damage** to **PNS** **Nerves**
* Any **surviving** **motor** **neurones** --\> can **_sprout_** --\> to **innervate** **target** & **take** **over** (from the ones that died)
65
What is the **_problem_** with **successfully regenerated nerves**?
* They **fatigue** **_earlier_** in **life** (problems arise earlier in life)
66
What is a motor unit made up of?
1. **Muscle Fibres**
2. **Nerves** (the somatosensory unit & axon)
67
What does a **LMNL (Lower Motor Neurone Lesion)** cause?
- What **type** of **paralysis**?
* Flaccid Paralysis
* Rapid Muscle Wasting
* Fibrillation
* Fasciculation
**Flaccid Paralysis:** If any muscle does not contract it will waste away --\> therefore you need electrical stimulation to stop them wasting away
**Fasciculation:** Little parts of muscle will twitch this is a common sign of LMNL
NB: **Poliomyelilitis** can cause **LMNL**
68
What is a **common** **sign** of **LMNL**?
**Fasciculation (twitching)**
69
Where does damage have to occur to be classed as a LMNL?
1. **Death** of **Cell Body**
2. **Injury** of **Axon** --\> **anywhere** along its course
70
What happens when **peripheral** **nerve** is **damaged**?
* Distal part of axon will die (whether motor or sensory)
* **Surviving** **axons** --\> will **sprout** from **injury** **site**
* They wil**l grow distally** to try and **find** a **target** which they can **stimulate**
* Axons **regenerate** along **course of pre-existing fibres** looking for something to innervate
*
If they find their target then regeneration is successful and patient will get better (regain control)
71
What happens when **CNS** **nerve** is **damaged**?
* Axons **_cannot_** regenerate
* Therefore there is no recovery
* Noone knows why not
*
72
What happens if **damage** is **_close_** to **cell body**?
* If **close** **enough** then **cell body may die**
* Otherwise --\> **axons regenerate**
73
What happens to muscles that are not innervated?
* muscles that are **_not_** **innervated** --\> **_cannot_** **contract** --\> they are **flaccid**
* Muscles that do **_not_** **contract** --\> **waste away**
**Electrical Stimulation** --\> can **_STOP_** them **WASTING AWAY**
**LMNL** --\> causes muscles to **_TWITCH_** & **_FIBRILLATE_**
74
What is the problem with regeneration?
* Innervation is **not** as good as it was before
75
How can we help peripheral nerves regenerate?
* **Repair** by **suturing** (stich nerves together)
* Axons can **regenerate** **_across the lesion_** & **_down the distal stump_**
* The damaged nerves are s**titched up together again** --\> however axons will **_not_** **join up again**
* However they will **line up** so that the **proximal stump can regenerate**
* **New regenerated axons** can **follow** the p**re-existing fibre down** **its** **path** to where the **distal dead neurone** was going --\> to find its **distal target**
**NB:** Axons do not join up but regenerate from the nerve stump (where damage is)
76
Problem with suturing?
* Only **50% of patients** with **repaired peripheral nerves** report **useful degree of functional recovery**
* However there is **regeneration of axons** in nearly **_every_** **case** (but some lost along the way)
* **Neuropathic pain** --\> this is a **consequence** of a **failed functional regeneration**
**Theory:** Axons are lost on their way down to regenerate the target they should be innervating (may not be correct)
77
Which tracts carry **voluntary motor neurones**?
- Where do they arise from?
- Where do they end?
* **Corticospinal (Lateral) Tracts**
* **Descending Motor instructions** are carried by **corticospinal tract**
* **Arise** from the **cerebral cortex**
* They **cross** the spinal cord
* **End** in **Spinal** **Cord**
*
78
Is brain control **ipsilateral** or **contralateral**?
* **Each side** of the **brain** --\> controls the **other side of the body**
* **Each side** of the **brain** --\> **receives sensory info** from the **other side of the body**
* Thus **sensory** & **motor** **tracts** in the brain come from **_contralateral_** **side** (decussate)
* The information **DECUSSATES (crosses the midline)**
79
What does ipsilateral & contralateral mean?
Ipsilateral --\> SAME SIDE
Contralateral --\> OPPOSITE SIDE
80
What is the **path** of the **corticospinal tract?**
What does the **corticospinal tract** do?
- What is its **function**?
- What is it called in the spinal cord (after decussation)?
Where does the **decussation** occur?
* It is the **main motor tract**
* Called the **Lateral Corticospinal Tract** in the **spinal** **cord** after decussation
* Decussation occurs in the **_LOWEST_ PART of the MEDULLA** (brainstem)
* Includes **_voluntary_ movement**
* **Cell of Origin** --\> came from the **_CONTRALATERAL_** **SIDE** to the **MOTOR** **ORGAN** it **CONTROLS**
Corticospinal tract needed to widdle your fingers
81
What is an **Upper Motor Neurone Lesion**?
How can it occur?
* This means **control from the brain** is **_lost_** --\> however **everything below** is **still intact**
* There is **NO CENTRAL BRAIN CONTROL**
* Occurs due to: **_SPINAL CORD INJURY_** or **_STROKE_** or **_BRAIN INJURY_**
*
82
What happens to **degenerated corticospinal tract?**
* Replaced by **astrocytes (glial cells)**
83
* What are the **signs** of **UMNL**?
Can occur due to SPINAL INJURY / STROKE / BRAIN DAMAGE
* **Spastic Paralysis**
* **Little Muscle Wasting**
* **Babinsky Sign**
84
What is **spastic reflex?**
- When does it occur
* Occurs in **UMNL (loss of brain input/control)**
* Contract **spontaneously** **_all_** the **time**
* Occurs due to **reflexes of the muscle spindle**
* **_No_** **brain** **control** therefore muscles **contract on its own**
* This means there is **no wasting**
* You get **babinsky reflex** (no inhibition from brain)
* Muscles **_cannot_** be **voluntarily moved (due to lost cortical connection)**
Spinal Reflexes --\> **_STILL_** **WORK** in **UMNL** --\> they are acting **_ALL_** the **TIME** --\> there is **_NO_** **MUSCLE** **WASTING** --\> due to these **ELECTRICAL STIMULATIONS from REFLEXES**
85
Will a **_baby_** **dorsiflex** or **plantar** **flex** when its foot is **stroked**?
Why?
* Baby --\> **_DORSIFELXION_**
This is called the **BABINSKI REFLEX**
* **This is NOT become of an UMNL (obviously)**
* Corticospinal Tract has **_not_** been **myelinated** in **babies** yet
* Usually these **supress** the **dorsiflexion** in **adults** and cause **_plantarflexion_**
* Seen until the **age of 2**
* Usually **corticospinal tract _supresses dorsiflexion_** however here it does **_not_** becuase it is **_not_** **myelinated** (not to do with UMNL)
86
Will an **adult** dorsiflex or plantar flex when its foot is stroked?
Why?
* See this when a patient has an **_UPPER MOTOR NEURONE LESION_**
87
What is the babinski sign?
* **Dorsiflexion** (not normal) when you **stroke a foot**
* Should be **plantarflexing**
It is a sign of either:
1. **Baby below 2**
2. **UMBL**
88
When do we see the Babinski reflex in adults?
89
Why is the corticospinal tract important in the context of the babinski reflex?
* Usually there is a signal that goes down the LATERAL CORTICOPSINAL TRACT
* This usually supresses the dorsiflexion
* Babies however do not have myelinated corticospinal tract --\> thus they do not have this supression to dorsiflexion
* This means they do dorsiflexion
It causes **_SUPRESSION_** of **DORSIFLEXION** when the **FOOT** is **STROKED**
**Non-Myelinated Corticospinal Tract** --\> will **_NOT_** be able to **SUPRESS BABINSKI SIGN**
90
Where do the **corticospinal tracts** arise from?
Does it pass down the **_ventral_** or **_dorsal_** part of the brainstem?
Where does it **decussate**?
* Cerebral Cortex
* Near **ventral surface** of **brainstem**
* Decussates on the **_anterior_** **surface** of the **Medulla** (**brainstem)**
* **_After_** **decussation** it forms the **corticospinal tract** in the **spinal cord**
It goes down the **FOREBRAIN** then down the **BRAINSTEM** then it crosses over at the **VENTRAL PART of the MEDULLA**
91
Here is a section of the **upper midbrain**
What is being pointed at?
**_Superior_ Colliculus** --\> important for **EYE MOVEMENTS**
92
**Section** through **Lower** **Pons**
93
What does the **basilar artery supply**?
**Basilar Artery** --\> supplies the **_PONS_**
Basilar Artery Branches:
* They **_ONLY_** supply the **MOTOR BUNDLES in PONS**
* They do **_NOT_** SUPPLY the **SENSORY BUNDLES**
94
What happens if a branch of the basilar artery is blocked & why?
* Basilar Artery --\> supplies the CORTICOSPINAL TRACTS in PONS
* Blocked --\> causes LOCKED IN SYNDROME
This is because they would **LOSE BLOOD SUPPLY** to the **_MOTOR_** **BUNDLES** but **_NOT_** the **_SENSORY_** **BUNDLES**
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What is locked in syndrome?
Sensory Tracts --\> INTACT
Motor Tracts --\> LOST
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What forms the **pyramids** in the **open medulla**?
* Corticospinal Tracts
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What is the **open medulla**?
* This is the top (rostral) part of the medulla
* Open --\> because it has 'opened up' to the 4th ventricle
* There is no central canal
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What is the **closed medulla**?
* **Bottom (caudal)** part of the **medulla**
* Contains a **central canal**
* It has still **_not_** **'opened up'** to the **4th ventricle**
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What does **selective** **damage** to the **pyramids (rare)** do?
* **Corticospinal tracts** travel in the **pyramids**
* These neurones go from the **cerebral cortex (**cell body in cortex) to the **brainstem**
* They go down to **spinal cord** and **control motor neurones**
* they bring about **voluntary movements**
**Corticospinal Tract --\>** where **cerebral** **cortex** can **produce** **voluntary** **movements**
Causes **DESTRUCTION** of the **_CORTICOSPINAL TRACT_**
100
What are the **2 types** of **strokes**?
1. **Haemorrhage** (blood leaking out somewhere where it shouldn't)
2. **Occlusion** (thrombus/embolism in the blood vessel)
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What is the difference between a **thrombus** and an **embolism**?
* Thrombus --\> **NON-MOVING CLOT**
* Embolism --\> **MOVING CLOT**
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What do the **aqueduct** and **central** **canal** have in common?
* They **both** open up to the **4th ventricle**
**Central Canal:** Goes up to the **medulla** and **opens up in the _rostral_ region** into the **4th ventricle**
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How does the **corticospinal tract** travel through the **pons**?
* It is **broken up** as **bundles** in the **_pons_**
* Travels as one in the **pyramids** in the **_medulla_**
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What does the **inferior cerebellar peduncle** connect?
Connection between **CEREBELLUM** & **BRAINSTEM** (medulla)
(There are 2 other peduncles)
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How does the **corticospinal** **tract** travel in the **_pons_** & **_medulla_**?
* **Pons** --\> BUNDLES
* **Medulla** --\> COMES TOGETHER --\> form LARGE BUNDLES called the PYRAMIDS (pyramidal tract)
**Pyramids** --\> contains **_only_** the **corticospinal** **tract**
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What is the **landmark** of the **_open_** **medulla**?
**Olives**
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What happens if someone has a **lesion** of the **corticospinal tract**?
* After Surgery Recovery
* Patients begins to **return voluntary movement command**s --\> despite **not** having **corticospinal tract**
* They can do **nearly all the actions** as before
* However --\> the one feature they **lose** is **precise control of the hands & fingers**
* They now have **clumsy hands (lose accurate finger control)**
This is because **accurate finger control** was **_solely controlled_** by the **corticospinal tract** (cannot be taken over)
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Does the **closed medulla** contain a **central canal** or **not**?
* **Yes** it does
* It has **not**'opened up' yet
* **Brainstem central canal** is **_continuous_** with **central canal in spinal cord**
* **Closed Medulla** --\> has **_no_** **4th ventricle** dorsal to it yet
* **Open medulla --\>** has a **4th ventricle** dorsal to it
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What happens in the **lowest part** of the **medulla**?
* **Lowest** **Part** of the **Medulla** --\> is **just** **before** spinal cord begins
* **Corticospinal Axons** --\> **cross the midline** (decussation of pyramids)
* **Ventral Surface** --\> where **CORTICOSPINAL TRACT** is found
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How does the decussation appear?
* **Bottom of the Pyramids:** There is an **obscurity** as the **bundles of axons** in the **corticospinal tract _cross over_** in the **lowest part of the medulla**
* They **partially fill** in the **ventral fissure** in the **ventral medullary surface**
* **Cross over** to **contralateral side** (one motor side controls contralateral side)
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Labelled picture of the brainstem
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What is the **alternative motor pathway** to the **corticospinal tract**?
What can it do?
What cant it do?
Where is it found in the spinal cord?
* Rubrospinal Tract
* It can **voluntary control movements** too (another voluntary motor pathway)
* it **_cannot_** do **accurate movements of the fingers**
* It overlaps the **descending** **corticospinal** **tract**
* Both tracts are **dorsal** to the **denticulate ligaments**
It is **another** **pathway** --\> where the **cerebral cortex** can **control voluntary motor neurones** --\> but it needs an **extra synapse** in the **_red nucleus_**
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What is the **rubrospinal tract pathway**?
1. Goes from the **forebrain** to the **red nucleus** (which has motor functions)
2. Axon leaves the **red nucleus** to **cross the midline** at the **level of the red nucleus**
3. **Descends** the **spinal tract**
4. **Synapses** at **interneurones/motorneurones**
5. **Interneurones** go to **motor neurones** --\> which **control muscle**
It **originates** from the **cerebral cortex** allowing you to make **voluntary movements**
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What are the locations of the **corticospinal tract** & **rubrospinal tract** in the **spinal cord**?
* **_Corticospinal Tract_** --\> runs in the **DORSAL-LATERAL WHITE COLUMN**
* **_Rubrospinal Tract_** --\> **OVERLAPS** the **CORTICOSPINAL TRACT** --\> it is **SLIGHTLY ANTERIOR**
