neuro A + CNS

Question 1

Neural Tube Formation

Answer 1

• The neural plate invaginates, forming a neural groove with neural folds on either side.
• The neural folds fuse at the midline, closing the neural groove to form the neural tube.
• The neural tube later develops into the central nervous system (CNS) (brain and spinal cord).

Question 2

Cortical Mantle & Pallium

Answer 2

Cortical Mantle/crebral cortex: Composed of glutamatergic neurons, which are excitatory.

**Pallium: **Located below the cortical mantle and contains GABAergic, inhibitory neurons.

Question 3

Origin of Cortical GABAergic Inhibitory Neurons

Answer 3

Expansion of the Pallium:
- to produce a large number of these neurons needed for the growing cortical areas.
- Prevents overexcitation, which could lead to disorders like epilepsy.

Migration:
-neurons are not born exactly where they will function.
- so they must migrate from their origin to their final destination, such as the cortex.
- To ensure neurons are positioned correctly to form proper neural circuits.
- precise arrangement allows different brain regions to communicate effectively.

Cortical Infiltration:
- inhibitory neurons must embed themselves into the cortical layers where they can interact with excitatory neurons.

Synapse Maturation:
- Neurons initially form simple connections,
- but these must become more complex and specialized through a process called* synapse maturation.*
- To strengthen important connections through activity-dependent mechanisms
- Mature synapses are more efficient at transmitting signals.
- Supports long-term processes such as memory formation, learning, and adaptive behavior.

Question 4

Neurotransmitter Identity of Pallium & Cortex

Answer 4

Pallium → GABAergic (Inhibitory)
Cortex → Glutamatergic (Excitatory)

Question 5

Spinal Cord Segments
The spinal cord is divided into five regions:

Answer 5

Cervical (C1-C8)
Thoracic (T1-T12)
Lumbar (L1-L5)
Sacral (S1-S5)
Coccygeal (Co1)

Question 6

Major Areas of the CNS

Answer 6

Forebrain
Cerebrum – Higher cognitive functions, sensory processing, motor control
Diencephalon – Includes the thalamus (sensory relay) and hypothalamus (homeostasis, endocrine regulation)

Midbrain – Connects forebrain and hindbrain, involved in motor control and sensory processing

Hindbrain
Medulla Oblongata – Regulates vital functions (breathing, heart rate)
Pons – Relays signals between brain regions, controls breathing
Cerebellum – Coordination, balance, and motor learning

Question 7

Peripheral Nervous System (PNS) Overview

Answer 7

Cranial Nerves
12 pairs
Exit the skull through foramina
Associated with cranial ganglia

Spinal Nerves
31 pairs
Exit the vertebral column through intervertebral foramina

Segments:
8 Cervical
12 Thoracic
5 Lumbar
5 Sacral
1 Coccygeal

Question 8

Brain Orientation Terms

Answer 8

Anterior (Rostral) → Front of the brain
Posterior (Caudal) → Back of the brain
Superior → Above
Inferior → Below
Dorsal → Toward the top (back in the spinal cord)
Ventral → Toward the bottom (front in the spinal cord)

Question 9

Brain Planes of Section

Answer 9

Sagittal Plane → Vertical plane that divides the brain into left and right (midline = midsagittal)
Coronal Plane → Vertical plane from the crown, dividing the brain into front and back sections
Horizontal Plane → Divides the brain into top and bottom sections

Question 10

White Matter vs. Gray Matter

Answer 10

White Matter → Composed of myelinated axons
- Includes peduncles, fibers, fasciculi, funiculi, lemnisci, pathways, and tracts (axonal connections)

Gray Matter → Composed of nerve cell bodies and unmyelinated neurons
- Forms ganglia, nuclei, and central gray horns (processing centers)

Question 11

Cortex & Ventricles

Answer 11

• Cortex is made up of different lobes (e.g., frontal, parietal, temporal, occipital).
• CNS Empty Spaces are ventricles filled with cerebrospinal fluid (CSF), which cushions and nourishes the brain.

Question 12

Ventricular System & CSF Circulation

4th Ventricle:

Answer 12

• Medial, separates the cerebellum from the brainstem
• Connected to the 3rd ventricle via the cerebral aqueduct

Question 13

Ventricular System & CSF Circulation

3rd Ventricle

Answer 13

• More rostral, separates the hypothalamus from the rest of the forebrain
• Connected to lateral ventricles (L/R)

Question 14

Ventricular System & CSF Circulation

Lateral Ventricles:

Answer 14

Largest ventricles, located in cerebral hemispheres

Question 15

CSF Circulation

CSF Circulation & Absorption

Answer 15

• Sagittal Sinuses allow CSF to return to the blood
• Valves in the sagittal sinuses regulate CSF flow

Question 16

CSF Circulation

Hydrocephalus:

Answer 16

• Caused by obstruction (e.g., tumor, trauma, congenital malformation)
• Leads to CSF accumulation, increased intracranial pressure

Question 17

Spinal Tap & Meningitis Diagnosis

Answer 17

• Spinal Tap (Lumbar Puncture) is performed in the lumbar cistern
• Used to analyze cerebrospinal fluid (CSF)
• Helps diagnose bacterial vs. viral meningitis based on CSF composition

Question 18

Meninges Layers

Dura Mater (External)

Answer 18

• Tough, outermost layer
• Contains pain receptors

Question 19

Meninges Layers

Arachnoid Membrane (Intermediate)

Answer 19

• Connective tissue layer
• No pain receptors

Question 20

Meninges Layers

Pia Mater (Internal)

Answer 20

• Thin layer that follows brain folds (circumvolutions)
• Contains pain receptors

Question 21

Cranial Nerves (12 Pairs)

Answer 21

Olfactory (I) – Smell (Rostral)
Optic (II) – Vision (Rostral)
Oculomotor (III) – Up/down eye movement
Trochlear (IV) – Slanted eye movement
Trigeminal (V) – Facial sensation
Abducens (VI) – Lateral eye movement
Facial (VII) – Facial muscle movement
Vestibulocochlear (VIII) – Hearing & balance
Glossopharyngeal (IX) – Controls swallowing muscles
Vagus (X) – Stimulates parasympathetic nervous system (PNS)
Accessory (XI) – Motor movement of neck/shoulders
Hypoglossal (XII) – Tongue movement

Question 22

Nervous System Pathways

Answer 22

Afferent (Sensory) → Signals travel from periphery to brain

Efferent (Motor) → Signals travel from brain to periphery

Special → Dedicated function (e.g., vision, hearing)

General → Non-specific, common functions

Somatic → External body (voluntary control)

Visceral (Autonomic) → Internal body (involuntary control)

Question 23

Spinal Nerve Branching Structure:

Answer 23

Roots
Trunks
Divisions
Cords
Terminal Branches

Question 24

Spinal Cord Anatomy (Thoracic & Lower Regions)

Answer 24

**Thoracic Region (Transverse Section)
*** Shows anterior (ventral) and posterior (dorsal) roots of a spinal nerve
* Enclosed by the meninges (Dura mater, Arachnoid, Pia mater)

Lower End of Spinal Cord (Posterior View)
* Cauda Equina → Bundle of spinal nerves extending beyond the spinal cord
* Shows relationship with the lumbar vertebrae, sacrum, and coccyx
* Important for lumbar punctures (spinal taps) in the lumbar cistern

Question 25

Spinal Cord Functional Organization

Answer 25

Posterior (Dorsal) Root → Sensory (Afferent) signals enter the spinal cord Anterior (Ventral) Root → Motor (Efferent) signals exit the spinal cord

Question 26

Spinal Cord Horns & Funiculi

Answer 26

**Horns (Gray Matter): **Dorsal Horn → Sensory, contains Rexed layers 1-6 Ventral Horn → Motor, contains Rexed layers 7-9 **Funiculi (White Matter Columns): **Dorsal Funiculus Lateral Funiculus Ventral Funiculus

Question 27

Spinal Ascending Tracts (Sensory Pathways)

Answer 27

Dorsal Columns (Posterior Funiculi) → Deep touch, proprioception, vibration Lateral Spinothalamic Tract → Pain and temperature to CNS Ventral Spinothalamic Tract → Light touch Anterior Spinothalamic Tract → Light touch & pressure (pain pathways) Posterior White Column → Part of the Dorsal Column-Medial Lemniscal Pathway (fine touch, vibration, proprioception)

Question 28

Spinal Descending Tracts (Motor Pathways)

Answer 28

Lateral Corticospinal Tract → Main voluntary motor control ****Controls upper extremity & limb muscles - Contralateral cortical innervation - Pathways are more medial (central) Ventral Corticospinal Tract → Voluntary motor control Anterior Corticospinal Tract → Innervates trunk & axial muscles - Provides both ipsilateral & contralateral innervation

Question 29

Brainstem & Its Connection to the Cerebrum & Spinal Cord

Answer 29

**Brainstem serves as the link between the cerebrum and spinal cord** Composed of: Midbrain – Motor control, auditory & visual processing Pons – Relays signals between brain regions, controls breathing Medulla Oblongata – Regulates vital functions (heart rate, respiration)

Question 30

Blood Supply to the Brain

Answer 30

Basilar Artery → Formed by the merging of vertebral arteries, supplies the brainstem and cerebrum Vertebral Arteries → Arise from the subclavian arteries, supply the brainstem, cerebellum, and posterior brain

Question 31

Functions of the Brainstem

Answer 31

Conduit Function → Serves as a passageway for ascending (sensory) and descending (motor) tracts connecting the spinal cord to the forebrain. Reflex Centers → Regulates respiration, cardiovascular system, and consciousness. Cranial Nerve Nuclei → Contains nuclei for Cranial Nerves III through XII (responsible for motor and sensory functions).

Question 32

Main Systems & Functions of the Brainstem

Answer 32

Respiration → Regulates breathing Cough Reflex → Protective airway response Swallowing Reflex → Controls safe food/liquid passage Pupillary Response → Adjusts pupil size to light Sleep Activation → Plays a role in sleep regulation

Question 33

Sections of the Brainstem (Sagittal View)

Answer 33

Central Canal → Hollow space that connects to the ventricular system Dorsal Part → Located near the cerebellum Fourth Ventricle → Separates the cerebellum from the brainstem Positioned below the pons

Question 34

PAG area

Answer 34

Periaqueductal Gray (PAG) → Important ring-like area involved in pain modulation and autonomic functions Red Nucleus → Involved in motor coordination Substantia Nigra → Part of the pons, contains dopaminergic neurons - Degeneration of dopaminergic cells in the substantia nigra leads to Parkinson’s disease

Question 35

Reticular Formation Organization

Answer 35

- Reticular Formation (RF) → Diffuse network in the brainstem, involved in arousal, consciousness, and autonomic functions **Median RF (Midline)** - Composed of raphe nuclei - Serotonergic (involved in mood and sleep regulation) **Paramedian RF** - Contains magnocellular and gigantocellular neurons - Blends with central reticular nucleus - Involved in motor coordination **Lateral (Parvocellular) RF** - Receives input from all sensory pathways, including special senses - Plays a role in sensory integration and autonomic regulation

Question 36

Pontine Tegmentum & Neuromodulation

Answer 36

- Pontine Tegmentum → Major source of cerebral neuromodulation - Located in a transverse section of the upper pons - Contains elements of the reticular formation - Involved in arousal, sleep regulation, and autonomic functions

Question 37

Aminergic System & Functions

Answer 37

Aminergic Neurotransmitters → Includes dopamine, norepinephrine, serotonin (everything except acetylcholine) **Functions:** Sleep & Wake Cycles Reward & Punishment Axis → Modulated by dopamine & norepinephrine Mood Regulation → Controlled by serotonin Metabolism Regulation

Question 38

Catecholamine Synthesis Pathway

Answer 38

Tyrosine → Converted to L-DOPA L-DOPA → Converted to Dopamine (DA) Dopamine (DA) → Converted to Norepinephrine (NE) Norepinephrine (NE) → Converted to Epinephrine (EPI) **Key Functions:** Dopamine (DA) → Reward, motivation, motor control Norepinephrine (NE) → Attention, arousal, stress response Epinephrine (EPI) → Fight-or-flight response

Question 39

Thalamus: The Brain's Relay Center

Answer 39

Bilateral nucleus that connects with the cerebral cortex and other brain areas **Receives input from:** * Sensory systems (direct relay) * Cerebellum (motor coordination) * Basal ganglia (movement regulation) * Plays a key role in maintaining wakefulness * Interaction between the thalamus and cortex forms the basis of consciousness

Question 40

Olfactory Pathway (Exception to Thalamic Relay)

Answer 40

- Olfactory signals bypass the thalamus - Travel directly from sensory receptors to the olfactory cortex - Unique among sensory systems, providing a direct connection to higher brain areas (e.g., limbic system for smell-emotion link)

Question 41

GABAergic Neurons (Inhibitory Neurons)

Answer 41

**NT**: GABA (Gamma-Aminobutyric Acid) **Function:** Inhibitory—they reduce the activity of other neurons, making it less likely for them to fire action potentials. **Purpose:** * Maintain balance in brain activity (prevent overexcitement). * Regulate functions like anxiety control, muscle relaxation, and seizure prevention.

Question 42

Glutamatergic Neurons (Excitatory Neurons)

Answer 42

**NT**: Glutamate **Function**: Excitatory—they increase the activity of other neurons, making them more likely to fire action potentials. **Purpose:** * Responsible for learning, memory, and cognitive functions. * Promote neural plasticity, which helps the brain adapt and change with experiences.

Question 43

Cholinergic Neurons (Modulatory Neurons)

Answer 43

**NT**: Acetylcholine (ACh) **Function**: Modulatory—they can have both excitatory and inhibitory effects depending on the receptor they bind to. **Purpose:** * Control attention, learning, arousal, and memory. * Play a role in muscle contraction in the peripheral nervous system. * Example: Think of them like a gear shifter, helping to adjust the brain's activity levels to match different tasks.

Question 44

Exciatory vs inhibitory

Answer 44

***Excitatory Synapses ***(Glutamatergic & some Cholinergic): - Trigger Na⁺ and Ca²⁺ influx, leading to depolarization (action potential more likely). **Inhibitory Synapses **(GABAergic): - Trigger Cl⁻ influx or K⁺ efflux, causing hyperpolarization (action potential less likely).