Organization of the CNS

Question 1

What happens in the 3rd, 4th, and 6th week of development in the human brain?

Answer 1

3rd week: brain starts as a neural tube

4th week: Anterior portion of neural tube begins to specialize into forebrain, midbrain and hindbrain, and spinal cord.

6th week: forebrain specializes into cerebrum and diencephalon and hindbrain specializes into pons and cerebellum, and medulla oblongata. Spinal cord and midbrain keep their shape.

Question 2

What are brain ventricles?

Answer 2

Fluid filled cavities lined by ependymal cells that were remnants of the hollow tube from which the brain developed. Includes the two lateral ventricles and two descending ventricles.

Question 3

What is the central canal?

Answer 3

Hollow tube in spinal cord that is continuous with ventricles and lined with ependymal cells.

Question 4

What is the difference between white and gray matter?

Answer 4

White matter: myelinated axons that make up a large portion of the brain

Gray matter: unmyelinated somas, axon terminals and dendrites clustered into nuclei (CNS)/ganglia (PNS)/cerebral cortex (surface)

Question 5

What protects the CNS?

Answer 5

1. Bone: skull and vertebral column
2. Meninges: three protective and nourishing membranes
3. Cerebrospinal fluid (CSF)
4. Blood brain barrier

Question 6

What are the three layers of the meninges?

Answer 6

1. Dura mater: thickest and intimately associated with veins and sinuses that drain blood from the brain
2. Archanoid membrane: loosely tied to inner membrane and has a villus that projects into the sinus of the dura mater
3. Pia mater: soft and delicate membrane that is intimately associated with the surface of the brain and spinal cord and are associated with arteries that supply blood to the brain.

Question 7

What is meningitis?

Answer 7

Contagious bacterial, viral, or fungal infection of the meninges that cases swelling and pressure on the brain.

Question 8

What are the three types of bleeding that traumatic head injures may cause?

Answer 8

1. Epidural bleeding (between skull and dura)
2. Subdural bleeding (between dura and arachnoid)
3. Subarachnoid bleeding (between arachnoid membrane and pia mater)

Question 9

What are the two types of protection the cerebrospinal fluid provides?

Answer 9

Physical protection: shock absorber, buoyant force to keep gravitational pressure off the brain.

Chemical protection: maintains solute concentrations in interstitial fluid surrounding neurons and removes waste

Question 10

What is the choroid plexus?

Answer 10

Specialized region on the walls of ventricles that secretes cerebrospinal fluid into the vesicles and selectively pump sodium and other solutes from plasma into the ventricles to create osmotic gradient.

Question 11

What is the subarachnoid space?

Answer 11

Space between the pia mater and the arachnoid membrane which is where the cerebrospinal fluid flows.

Question 12

What are foramen?

Answer 12

The openings in the brain or skull that act as passageways for different structures of the nervous and circulatory system from one region to the other.

Question 13

What is the arachnoid villi?

Answer 13

Fingerlike projections on the arachnoid membrane that allow cerebrospinal fluid to be reabsorbed into the blood.

Question 14

What is the blood-brain barrier?

Answer 14

Functional barrier between interstitial fluid of the brain and the plasma characterized by the highly selective permeability of brain capillaries due to tight junctions

Question 15

How does the blood-brain barrier form?

Answer 15

Induced by paracrine signals from pericytes (adjacent contractile cells) and astrocytes (feet surround the capillary)

Question 16

How does the blood-brain barrier work?

Answer 16

Capillary endothelium uses selected membrane carriers and channels to move nutrients and other useful materials from the blood into the brain interstitial fluid, or waste from interstitial fluid to plasma. Any water-soluble molecule that is not transported in one of these carriers cannot cross the blood-brain barrier unless it is a small lipophilic/nonpolar molecules.

Question 17

What is the spinal cord?

Answer 17

Major pathway between brain and skin, muscle, joints, and organs that contain neural networks responsible for locomotion.

Question 18

How many pairs of spinal nerves are there in total, and what are the four levels it creates?

Answer 18

There are 31 pairs of spinal nerves in total that are separated into 4 levels: Cervical, thoracic, lumbar, and sacral (coccygeal)

Question 19

What are cauda equina?

Answer 19

Thick elongated nerve roots that spinal nerves separate into after lumbar nerve 1-2

Question 20

What is the difference between Dorsal and Ventral roots?

Answer 20

Dorsal: part of spinal nerve that joins the spinal cord to carry sensory (afferent) information to CNS

Ventral: part of spinal nerve that joins the spinal cord to carry motor (efferent) information to muscles and glands

Question 21

What is the dorsal root ganglia?

Answer 21

Swellings found on the dorsal roots just before they enter the cord that contain cell bodies of sensory neurons.

Question 22

What is found in the white matter of the spinal cord?

Answer 22

Dorsal ascending tracts that carry sensory info to the brain and ventral descending tracts that carry commands to motor neurons

Question 23

What is found in the gray matter of the spinal cord?

Answer 23

1. Somatic sensory nuclei: carry signals from temp, surface, vibration
2. Visceral sensory nuclei: carry signals from the organs of the thoracic and abdominal cavities
3. Autonomic efferent Nuclei
4. Somatic Motor Nuclei

Question 24

What is the brainstem?

Answer 24

Oldest and most primitive region of the brain consisting of the midbrain, pons and medulla.

Question 25

What are cranial nerves?

Answer 25

Pairs of nerves branching from the brain (not spinal cord) that are sensory, motor or both in function. 10/12 pairs arise from the brain stem.

Question 26

What is the Medulla’s structure and function?

Answer 26

Aka medulla oblongata;

structure: transition from spinal cord into brain proper and contains neuronal clusters

function: clusters control heart/blood vessel function, respiration and many digestive functions

Question 27

What is the Pons structure and function?

Answer 27

Structure: Bulbous protrusion above medulla and below midbrain

Function: relay station between cerebellum and cerebrum. Regulates muscle reflexes involved in equilibrium (balance) and posture.

Question 28

What is the midbrain structure and function?

Answer 28

Structure: Small area between lower brainstem (pons and medulla) and diencephalon.

Function: relay for visual and auditory info (in terms of balance), governs movement of eyes, gives rise to groups of modulatory neurons

Question 29

What is Reticular formation structure and function?

Answer 29

Structure: Interconnected groups of neurons in midbrain and medulla

Functions: receives and integrates sensory input that plays a critical role in wakefulness and attention and gives rise to modulatory neurons

Question 30

What are modulatory neurons?

Answer 30

Special neurons in midbrain and reticular formation that send neuromodulators (neurotransmitters) to bind to GPCR to initiate second messenger signalling and create subtle, long lasting changes.

Question 31

What is the cerebellum’s functions?

Answer 31

1. Processes sensory info from muscles, joints, vestibular system, and eyes.
2. Integrate position and movement of body with the intent to move body.
3. Maintains balance and controls eye movements
4. Enhances muscle tone and plans, initiates and coordinates voluntary activity
5. Stores procedurals important for motor learning

Question 32

What is the diencephalon?

Answer 32

Between brain stem and cerebrum, composed of hypothalamus and thalamus and acts as the primary integration centre.

Question 33

What is the thalamus?

Answer 33

Part of diencephalon that receives information from almost every area of the CNS and sends info to the same areas. Includes sensory/motor info, emotional info, and arousal.

Question 34

What is the hypothalamus?

Answer 34

Part of diencephalon most involved in directly regulating internal environment, including:

1. body temp
2. thirst/urine output
3. food intake
4. anterior pituitary hormone secretion
5. produces neuroendocrines vasopressin + oxytocin
6. Uterine contractions and milk ejection
7. major ANS coordinating center
8. emotional and behavioural patterns

Question 35

What is the cerebrum structure?

Answer 35

Largest, newest, most distinct part of the brain composed of two hemispheres connected at corpus callosum. Includes cortex, white matter, basal ganglia, and limbic system.

Question 36

What is the cerebral cortex?

Answer 36

Highest most complex integrating area of the brain that plays a key role in most sophisticated neural functions. Includes gray matter with sulci (furrows) and gyri (convolution) to be used as landmarks.

Question 37

What are the five major lobes of the cerebral cortex?

Answer 37

1. Frontal: skeletal muscle movement and executive functions (thinking)
2. Parietal: touch, taste, temperature
3. occipital: vision/visual processing
4. Temporal: hearing
5. Insular: taste/smell, interoception

Question 38

What is cerebral lateralization?

Answer 38

Left brain-right brain dominance that occurs
because functional specialization is not symmetrical across the cerebral cortex.

Question 39

What functions occur on the right and left side of the brain (typically)?

Answer 39

Left: Language and verbal skills, writing, mathematical calculation

Right: spatial recognition, face recognition, emotion processing, artistic functions

Question 40

How does language processing occur?

Answer 40

Input from the visual cortex (reading) or auditory cortex (listening) goes to Wernicke’s area and then broca’s area. After processing in broca’s area, information travels to motor cortex to initiate spoken or written action

Question 41

What is aphasia?

Answer 41

Inability to comprehend or formulate language due to damage to Wernicke’s area (recptive aphasia) or broca’s area (expressive aphasia)

Question 42

what is the difference between damage to Wernicke’s area and broca’s area?

Answer 42

Wernicke’s area: difficulty understanding spoken or visual language (receptive aphasia), nonsensical speech because of trouble connecting words with meaning (Jargon aphasia)

Broca’s area: Difficulty expressing complex ideas, distorted words, difficulty interpreting words or sentences with several elements.

Question 43

What is basal ganglia structure and function?

Answer 43

Structure: region of cell bodies (ganglia) that form a complex circuit between motor cortex, premotor cortex, cerebellum, thalamus, and other areas

Function: control of cognitive ability and movement.

Question 44

What is parkinson’s disease?

Answer 44

Loss of dopaminergic neurons (neuromodulatory neurons) in basal ganglia. Causes tremors, loss of ability to move, and cognitive deficits.

Huntington’s disease: loss of cholinergic neurons (neuromodulatory neurons) in basal ganglia that would have activated dopaminergic neurons. Causes uncontrollable movements, loss of coordination, dementia.

Question 45

What is the limbic system?

Answer 45

Structure: Oldest part of the cerebrum including amygdala, hippocampus, and cingulate gyrus. It is strongly connected with the diencephalon and parts of the midbrain.

Function: Links higher cognitive functions and primitive emotional responses such as fear, aggression, reward, social and sexual behaviour.

Question 46

What do each part of the limbic system play a role in?

Answer 46

Amygdala: emotion and memory

Hippocampus: learning and memory

Cingulate gyrus: emotion

Question 47

How does the Limbic System Pathway work?

Answer 47

1. Sensory stimuli from sensory neurons reach cerebral cortex
2. Cerebral cortex integrates signal and synapses with Limbic system
3. Limbic system creates emotion. Emotion moves to Cerebral cortex to create awareness of emotion, as well as to hypothalamus and brain stem.
4. Hypothalamus and brain stem initiate voluntary and unconscious motor responses, autonomic responses, endocrine responses, and immune responses.