CSD 505 Comps Tossi

Central Nervous System Vs Peripheral Nervous System

CNS - Brain and Spinal Cord

PNS - everything outside of that

Two major functions of the brain (in and out):

Sensory (looking around with your eyes) = Ascending = Afferent = input to the brain

Motor (moving the muscles) = Descending = Efferent = output from the brain

Right motor/sensory jobs by the

left hemisphere

Left motor/sensory jobs by the

right hemisphere

Contralateral Control

Responsible for the other side of the body

Ipsilateral

belonging to or occurring on the same side of the body

Cranial Nerves are connected to:

Peripheral Nervous system (PNS) connected to the brainstem (beside one)

Cranial Nerve l

Olfactory
Sensory
Function: smell

Cranial Nerve ll

Optic
Sensory
Function: Sight

Cranial Nerve lll

Oculomotor

Motor
Function: pupil, eye movement

Cranial Nerve lV

Trochlear
Motor
Function: down/in eye movement

Cranial Nerve V

Trigeminal
Both
Function: facial sensation, chewing

Cranial Nerve Vl

Abducens

Motor

Function: side/out eye movement

Cranial Nerve Vll

Facial 

Both

Function: facial expression, taste (2/3)

Cranial Nerve Vlll

Vestibulocochlear (Acoustic)
Sensory
Function: hearing, balance

Cranial Nerve lX

Glossopharyngeal
Both
function: taste (1/3) ,swallow

Cranial Nerve X

Vagus
Both
Function: heart rate, digestion

Cranial Nerve Xl

Accessory
Motor
Function: neck/shoulder movement

Cranial Nerve Xll

Hypoglossal
Motor
Function: tongue movement

Cranial Nerve 3-8 are connected to the

pons

Cranial Nerve 9-12 are connected to the

medulla

Cranial Nerve Mnemonic

Oh

Oh

Oh

To

Take

A

Family

Vacation

Go

Vegas

After

Hours

Cranial Nerve Mnemonic sensory/motor

Some

Say

Marry

Money

But

My 

Brother

Says

Big

Boobs

Matter

More

How many cervical Nerves do we have?

8

The primary motor corttex

sends signals to the muscles in the body and head.

Which of the following is not a neurotransmitter?

Tetrahydrocannabinol
Dopamine
Norepinephrine
GABA
Glutamate

Tetrahydrocannabinol

Right order, from external to internal?

Dura mater, Arachinoid mater, Subarachinoid space, Pia mater.

What is part of the cerebral cortex?

Frontal lobe
Temporal lobe
Parietal lobe
Occipital Lobe

Which of the following is responsible for motor functions and decision making?

Frontal lobe

Which of the following is responsible for hearing and memory?

Temporal lobe

Which of the following is responsible for vision?

Occipital Lobe

Which of the following is responsible for somato-sensation and spacial navigation?

Parietal Lobe

Somato-sensation

the sense of touch

Basal Ganglia regions

Striatum: Globus Pallidus, Caudate Nucleus, Putamen

Substantia Niagra

Subthalamic Nucleus

Function of the basal ganglia

Motivation and Reward

Which of the following is not a description of the thalamus?

	Thalamus connects many places to many places. Therefore, thalamic damages can influence many functions togeter.
	Thalamus is connected to most part of the cerebral cortex.
	Thalamus produces memory.
	The cerebellum is connected to the (contralateral) thalamus, so that it can send signals to the primary motor cortex.
	The thalami are egg shaped structure that can be easy to find. It has left and right ones.

	Thalamus connects many places to many places. Therefore, thalamic damages can influence many functions togeter.
	Thalamus is connected to most part of the cerebral cortex.
Correct	Thalamus produces memory.
	The cerebellum is connected to the (contralateral) thalamus, so that it can send signals to the primary motor cortex.
	The thalami are egg shaped structure that can be easy to find. It has left and right ones.

The corticospinal tract

decussates at the bottom of the medulla

The spinothalamic sensory pathway (for pain and temperature)..

decussates at the spinal cord of its entry

descussates = 2 or more things intersect each other to form an X

The dorsal columns (for proprioception and vibration)..

decussates at the medulla

Broca’s and Werincke’s areas are

in the left side of the cerebral cortex. The right side homologues are not called as Broca’s and Wernike’s

Broca’s and Wernicke’s areas are

connected by the arcuate fasciculus

What are the criterion for assessing aphasia

Fluency

Comprehension

Repetition

In Broca’s aphasia, which of the following is typically intact?

Comprehension

In Wernicke’s aphasia, which of the following is typically intact?

Fluency

In transcortical sensory aphasia, which of the following is impaired

Comprehension

In transcortical motor aphasia, which of the following is impaired

Fluency

In conduction aphasia, which of the following is impaired?

Repetition

Apraxia of speech…

refers to the condition where motor planning in speech production is impaired.

What are the three kinds of tremor?

Intentional tremor
Resting tremor
Essential tremor

What is intentional tremor?

This tremor happens when someone points to something

What is resting tremors?

What is essential tremors

What is ataxia?

Inability to coordinate movement

In Dysmetria…

someone has difficulty in reaching the target

The Basillar Artery is right in front of…

The pons

Pons

Midbrain

Medulla

Thalamus

Which cerebral artery supplies to Broca’s and Wernicke’s area

Middle artery

Which cerebral artery supplies to the medial frontal lobe?

Anterior

What is part of the brainstem

Medulla
Midbrain
Pons

The Basillar artery is right in front of the

Pons

What are the cranial nerves that provide paratympathetic nerves?

The right eye (ball) is connected to 

both the left and right brain

The right brain is connected to

both the left and right eyeball

The left eyeball sees

both the left side (left visual field) and right side (right visual field)

The left brain sees

the right side (right visual field)

When CN VI is damaged, the affected eyeball stays

medially

Which statement about the trigeminal nerve is incorrect?

The CN V is responsible for mastication The CN V is responsible for moving ribs. The CN V is responsible for somato sensation in the face. The CN V is responsible for sensation in the upper lip.

The CN V is responsible for moving ribs.

To the midbrain which of the following cranial nerves are not connected?

l
ll
lll
lV

l

lll and lV are connected

To the pons, which of the following cranial nerve is NOT connected?

V
Vl
Vlll
lX

• lX
  
  V — connected to pons ✅

• VI — technically between pons and medulla, but still close

• VIII — pontomedullary junction, so still related

• IX — comes from the medulla, ❌ NOT connected to the pons

In the spinal cord,

In the superior/caudal portion of the spinal cord (such as cervical), greater volume of white matter is found compared to the inferior/rostral portion.

What is reflex?

Reflex is an involuntary activation of muscles, not involving higher brain order

In someone whose corpus callosum (the bridge connecting the left and right hemispheres) is cut, a word is seen in the left side

	has no access to language and therefore s/he cannot say the word, but cannot be drawn by left hand.
	has access to language and s/he can say the word.
	can be drawn by left hand, even s/he cannot name it.
	can be drawn by right hand but cannot be named.

can be drawn by left hand, even s/he cannot name it.

In someone whose corpus callosum (the bridge connecting the left and right hemispheres) is cut, a picture is seen in the left side

	has no access to language and therefore s/he cannot say the word, but cannot be drawn by left hand.
	has access to language and s/he can say the word.
	can be drawn by left hand, even s/he cannot name it.
	can be drawn by right hand but cannot be named.

can be drawn by left hand, even s/he cannot name it

In someone whose corpus callosum (the bridge connecting the left and right hemispheres) is cut, a picture is seen in the right side

	has no access to language and therefore s/he cannot say the word, but cannot be drawn by left hand.
	has access to language and s/he can say the word.
	can be drawn by left hand, even s/he cannot name it.
	can be drawn by right hand but cannot be named.

has access to language and s/he can say the word

In someone whose corpus callosum (the bridge connecting the left and right hemispheres) is cut, a word is seen in the right side

	has no access to language and therefore s/he cannot say the word, but cannot be drawn by left hand.
	has access to language and s/he can say the word.
	can be drawn by left hand, even s/he cannot name it.
	can be drawn by right hand but cannot be named.

has access to language and s/he can say the word.

What are all of the components of the auditory pathway (and therefore auditory brain response)?

• Auditory nerve (CN VIII)

  • Carries signals from the cochlea to the brainstem.

  • ABR: Wave I

• Cochlear nuclei

  • First central relay in the medulla/pontomedullary junction.

  • ABR: Wave II

• Superior olivary complex (SOC)

  • Located in the pons.

  • First site of binaural integration (sound localization).

  • ABR: Wave III

• Lateral lemniscus

  • A tract ascending through the pons and midbrain to the inferior colliculus.

  • ABR: Wave IV

• Inferior colliculus

  • Located in the midbrain, major integration center for auditory signals.

  • ABR: Wave IV/V

• Medial geniculate nucleus (MGN)

  • Relay in the thalamus, sends auditory information to cortex.

  • ABR: Not usually seen in standard brainstem ABR (cortical)

• Primary auditory cortex (Heschl’s gyrus)

  • Located in the temporal lobe; conscious perception of sound.

  • Beyond ABR, cortical response

A 64-year-old man had a stroke while sleeping and woke up in confusion and panic. He was taken to the emergency room where the examinating physician noticed the following.

- Complete left-side facial paralysis
- Inability to move the left eye laterally
- Hearing loss in the left ear
- Absence of pain and touch sensation on the left side of the face
- Some weakness in jaw movement

Which of the region is most likely be affected?

pons



🧠 Step 1: Look at the patient’s symptoms

Here’s what he has:

1. Complete left-side facial paralysis → affects muscles of facial expression → Cranial Nerve VII (Facial nerve).

2. Inability to move the left eye laterally → lateral rectus muscle, controlled by Cranial Nerve VI (Abducens).

3. Hearing loss in the left ear → Cranial Nerve VIII (Vestibulocochlear nerve).

4. Loss of pain and touch on left side of face → Cranial Nerve V (Trigeminal nerve) sensory fibers.

5. Some weakness in jaw movement → Cranial Nerve V (mandibular branch, V3) motor fibers.

---

🧩 Step 2: Identify which brainstem region contains all these cranial nerves

Cranial Nerve	Typical Brainstem Level
V (Trigeminal)	Pons
VI (Abducens)	Pontomedullary junction (lower pons)
VII (Facial)	Pontomedullary junction (lower pons)
VIII (Vestibulocochlear)	Pontomedullary junction (lower pons)

A 64-year-old man had a stroke while sleeping and woke up in confusion and panic. He was taken to the emergency room where the examinating physician noticed the following.

- Complete left-side facial paralysis
- Inability to move the left eye laterally
- Hearing loss in the left ear
- Absence of pain and touch sensation on the left isde of the face
- Some weakness in jaw movement

Which side of the brain is affected?

Left side of the brain


For brainstem cranial nerve lesions, facial and hearing deficits are usually ipsilateral.
Motor deficits of the body can be contralateral (pyramidal decussation in medulla), but here we’re talking mostly cranial nerves.

Lower Motor Neuron

These are the actual cranial nerve nuclei or the nerves themselves in the brainstem.

• Damage here = nerve can’t tell the muscle what to do → paralysis on the same side (ipsilateral).

• Example: lesion in left facial nerve nucleus (CN VII) → left face paralysis.

UMN (Upper Motor Neuron)

• These are the corticobulbar fibers from the cortex to the cranial nerve nuclei.

• Damage here = depends on which cranial nerve and which side of input it receives → often contralateral.

• Example: lesion in left cortex controlling lower face (CN VII) → weakness of right lower face.

When we talk about brainstem lesions, we are almost always talking about . That’s why most cranial nerves deficits in the brainstem are ___. Exceptions are

• LMN lesions (the nuclei or the nerves themselves)
  

• Ipsilateral
  

• CN IV → fibers cross inside the midbrain → lesion in nucleus → affects opposite side.

  • Some cranial nerves (like facial lower face or tongue) have special UMN bilateral/contralateral patterns, but that’s more relevant for cortical lesions, not brainstem.

We know it’s a brainstem lesion because:

• Several cranial nerves affected on the same side → not a peripheral nerve problem.

• The affected nerves’ nuclei all reside in the pons.

• Ipsilateral deficits match the LMN cranial nerve pattern.

A 44-year-old man fell while talking a shower and was found by his wife lying on the floor, fully conscious. Realizing that something was not right, she advised him to take a rest. Within a few hours, his speech became unintelligible and he told his wife about the pain and weakness he experienced in his right arm. At this point, the wife drove him to the hospital emergency room., where the attending physicians noted the following signs.

- Paresis in the right arm
- Severe pain in the right shoulder and arm
- Sensation of paresthesia (burning and pricking) in the right arm
- Lowered pain threshold (a slight touch caused a sharp pain sensation)
- Speech uninteligibility because of dysphonia and imprecise articulation
- Some emotional instability marked by frequent burst of crying and panic
- Some word-finding deficit
- Excellent comprehension for written and spoken language
- No (other) sign of aphasia

Which side of the brain is affected?

Left side of the brain

Step 1: Look at the body symptoms

• Right arm weakness and abnormal sensation (pain, burning, touch sensitivity)
  ✅ When the right side of the body is affected, the opposite (left) hemisphere of the brain is responsible.

Rule: Left brain controls right body, right brain controls left body.

---

Step 2: Look at the speech problem

• Speech is slurred/unintelligible (dysarthria)

• Comprehension is excellent

• Some word-finding problems, but no full aphasia

✅ This tells us:

• The problem is motor speech — the muscles that move your lips, tongue, jaw, and larynx are affected.

• It’s not classic Broca’s aphasia, because comprehension is fine.

So this points to a problem in the left motor cortex / premotor areas for speech.

---

Step 3: Emotional instability

• Sudden crying or panic is often seen with left frontal lobe lesions, because this region helps regulate emotional expression.

---

Step 4: Combine all the info

Symptom	Brain region likely affected
Right arm weakness	Left primary motor cortex
Right arm pain/paresthesia	Left primary somatosensory cortex
Slurred speech (dysarthria)	Left motor cortex/premotor areas controlling speech muscles
Emotional instability	Left frontal lobe

• Brainstem = _______ = ______

• Cortex = _____ = ____

• cranial nerve =ipsilateral (same side)

• body = contralateral (opposite side)

Dysarthria

muscle weakness affecting speech

When someone’s speech is unintelligible or slurred, it could be due to different causes:

Type	Cause	Features
Dysarthria	Weakness or incoordination of muscles used for speech (face, tongue, lips, larynx)	Speech is slurred, slow, imprecise, but language is normal (can understand & know what to say)
Apraxia of speech	Difficulty planning/programming speech movements	Effortful, inconsistent errors, but comprehension intact
Broca’s aphasia	Damage to Broca’s area in left frontal lobe	Non-fluent, effortful speech, word-finding problems, but comprehension mostly preserved; grammar is affected

“Can understand? → _____ → _________.”

“Can understand? → language is intact (they are able to comprehend) → problem is with muscles or speech planning, not aphasia.”

A 30-year -old window-washer fell from her ladder and injured her back. She showed the following symptoms.

- Spastic paralysis in the left leg.
- Positive Babinsky sign in the left leg.
- Loss of proprioception and vibration sensation in the left leg.
- Loss of pain and temparature sensation in the right leg. 
- Anywhere above the legs was intact.

Where could this damage be?

Spinal Cord (T11/T12)


Lower thoracic spinal cord (T11/T12)

• Part of the spinal cord in your back around the lower chest area.

• Controls the legs (motor + sensory).

• Damage here → leg problems only (like your window-washer patient).

---

2⃣ Cervical spinal cord (C1–C8)

• Part of the spinal cord in your neck.

• Controls arms, hands, and some upper body.

• Damage here → arm + hand weakness/sensory loss, maybe legs if large lesion.

---

3⃣ Internal capsule

• A brain structure, not spinal cord.

• Contains all the motor and sensory fibers traveling between the brain and spinal cord.

• Damage here → contralateral weakness or sensory loss in face, arm, and leg all together.

---

Simple way to remember:

Problem area	What’s affected
Lower thoracic cord	Legs only
Cervical cord	Arms + sometimes legs
Internal capsule	Contralateral face + arm + leg (whole side of body)

Babinski

Babinski sign is when stroking the sole of the foot makes the big toe stick up instead of curling down, which shows upper motor neuron damage.

Motor System Lesion

1⃣ Motor System

Feature	UMN Lesion (Brain/Spinal Cord)	LMN Lesion (Peripheral Nerve/Spinal Nerve)
Location	Brain or spinal cord (corticospinal tract)	Nerve fibers leaving spinal cord to muscle
Muscle tone	Increased (spastic)	Decreased (flaccid)
Reflexes	Increased (hyperreflexia)	Decreased or absent
Pathological signs	Babinski present	Babinski absent
Muscle wasting	Minimal early, may develop	Severe atrophy
Fasciculations	Rare	Present
Example	Stroke, spinal cord hemisection	Peripheral nerve injury, poliomyelitis

A 30-year -old window-washer fell from her ladder and injured her back. She showed the following symptoms.

- Spastic paralysis in the left leg.
- Positive Babinsky sign in the left leg.
- Loss of proprioception and vibration sensation in the left leg.
- Loss of pain and temparature sensation in the right leg. 
- Anywhere above the legs was intact.

Which side would the lesion be?

Left side

Step 1: Look at the UMN signs

• Spastic paralysis + positive Babinski → upper motor neuron (UMN) lesion

• UMN signs in the spinal cord are ipsilateral to the lesion (same side).

---

Step 2: Look at sensory loss

• Proprioception & vibration loss (dorsal column) on left leg → also ipsilateral, same side as lesion

• Pain & temperature loss (spinothalamic tract) on right leg → contralateral, because this tract crosses in the spinal cord

---

Step 3: Combine the info

• Ipsilateral UMN + dorsal column loss → left side lesion

• Contralateral spinothalamic loss is normal in Brown-Séquard syndrome

Ascending (Sensory) Pathways

Ascending (Sensory) Pathways

Pathway	Sensation carried	Side of body
Dorsal column–medial lemniscus (DCML)	Proprioception, vibration, fine touch	Ipsilateral in spinal cord, crosses in medulla
Spinothalamic tract (anterolateral system)	Pain, temperature, crude touch	Crosses in spinal cord → contralateral
Spinocerebellar tracts	Unconscious proprioception for coordination	Mostly ipsilateral to cerebellum

Descending (Motor) Pathways

Pathway	Function	Side of body
Corticospinal tract (pyramidal tract)	Voluntary movement	Crosses in medulla → contralateral body
Corticobulbar tract	Voluntary control of cranial nerves	Mostly bilateral, some contralateral dominance

A 60-year old man was taken to the emergency room for sensorimotor problems that developed abruptly while at work. The following symptoms were found:

-Dysarthric speech
-Lowered left side of the palate
-Dysphagia
-Sensation loss on the left side of the face
-Difficulty balancing with falling to the left
-Left-sided facial paralysis
-Weakness in the right leg and arm

Where can the lesion be? |

Pons and medulla

Cranial nerve signs (ipsilateral to lesion)

• Dysarthric speech + dysphagia + lowered left palate → CN IX & X involvement

• Left-sided facial paralysis → CN VII involvement

• Sensation loss on left side of face → CN V involvement

• Difficulty balancing, falling to left → cerebellar connections (inferior cerebellar peduncle) on left)

All these cranial nerve and cerebellar signs are on the left side, meaning the lesion is ipsilateral to them.

---

Body weakness (contralateral to lesion)

• Weakness in right arm and leg → UMN corticospinal tract damage

• Corticospinal fibers cross lower in the medulla, so lesion on the left brainstem affects the right body.

---

Step 2: Combine information

• Cranial nerve deficits + cerebellar signs ipsilateral

• Motor deficits contralateral

• This pattern is classic brainstem lesion, specifically pons + medulla, because:

1. Pons → CN V–VIII nuclei, corticospinal fibers start descending

2. Medulla → CN IX–X nuclei, corticospinal fibers cross (pyramidal decussation)

A 60-year old man was taken to the emergency room for sensorimotor problems that developed abruptly while at work. The following symptoms were found:

-Dysarthric speech
-Lowered left side of the palate
-Dysphagia
-Sensation loss on the left side of the face
-Difficulty balancing with falling to the left
-Left-sided facial paralysis
-Weakness in the right leg and arm

Where side the lesion be? 

Step 1: Cranial nerve and cerebellar signs

• Dysarthric speech, dysphagia, lowered left palate → CN IX & X

• Left-sided facial paralysis → CN VII

• Sensation loss on left side of face → CN V

• Difficulty balancing, falling to left → cerebellar connections (inferior cerebellar peduncle)

✅ All of these signs are on the left side → the lesion is ipsilateral to these deficits.

---

Step 2: Body weakness

• Weakness in right arm and leg → corticospinal tract (UMN)

• UMN fibers cross in the lower medulla → a lesion on the left side of the brainstem affects the right side of the body.

---

Step 3: Combine the info

• Cranial nerve + cerebellar deficits left side

• Contralateral body weakness right side

✅ Classic pattern of a left-sided brainstem lesion (pons + medulla).

Left side

What side are they on?

• Body (arm/leg) weakness or UMN signs → ______

• Cranial nerve signs → ______

• Cerebellar deficits → _______

• Body (arm/leg) weakness or UMN signs → opposite side of lesion

• Cranial nerve signs → same side as lesion

• Cerebellar deficits → same side as lesion

Difference between Hyperreflexia and Hyporeflexia

1⃣ Upper Motor Neuron (UMN) lesion

• UMNs normally inhibit spinal reflexes to keep them controlled.

• When UMNs are damaged → inhibition is lost → reflexes become overactive.

• Result: hyperreflexia (exaggerated reflexes)

• Often also see: spasticity, Babinski sign, weakness

Example: Stroke in the left brainstem → right arm & leg weakness + hyperactive reflexes

---

2⃣ Lower Motor Neuron (LMN) lesion

• LMNs carry the reflex arc from spinal cord to muscle.

• If LMN is damaged → reflex cannot happen because the pathway is broken.

• Result: hyporeflexia (weak or absent reflexes)

• Often also see: flaccid paralysis, muscle wasting, fasciculations

Example: Peripheral nerve injury → affected limb has weak reflexes

---

Quick memory trick

Lesion type	Reflexes
UMN	Hyperreflexia ↑
LMN	Hyporeflexia ↓