Lecture 2

Question 1

Corticospinal Tract

Answer 1

Descending Motor Pathway
Also called ‘Pyramidal Tract’
Decussation happens in the medulla

Question 2

Spinothalamic Tract

Answer 2

Ascending Sensory Pathway.
So from senses to the cortex via thalamus.
Decussation happens right away the nerve enters the spinal cord.

Question 3

The Meninges

Answer 3

The meninges are three membranes that envelop the brain and spinal cord.
1. Dura Matter
2. Arachnoid Membrane
3. Pia Mater (follows the surface of the brain).
Subarachnoid space is filled with cerebrospinal fluid.
Subarachnoid space between in between arachnoid membrane and Pia matter.
The function of meninges is protection.

Question 4

Choroid Plexus

Answer 4

Generates the cerebrospinal fluid.

Question 5

Cerebrospinal Fluid is important for ;

Answer 5

Protection of the brain and removal of the waste products of the brain.

Question 6

Cranial Nerves

Answer 6

Part of peripheral nervous system.
There are 12 cranial nerves and they mostly (but not exclusively) innervate the head and the neck.
Cranial nerves can be sensory or motor or mixed.

Question 7

Spinal Nerves

Answer 7

Spinal nerves belong to peripheral nervous system.
Innervates the whole body.
Innervates skin, joints and muscles also receives sensory information from the body.

Question 8

Dorsal Root Ganglia

Answer 8

Contain cell bodies of the peripheral sensory neurons of the spinal cord.

Question 9

Peripheral Nervous System consists of

Answer 9

Cranial Nerves (mostly originate from the brain stem?)
Spinal Nerves
Visceral Peripheral Nervous system = Sympathetic and Parasympathetic division.

Question 10

Visceral Peripheral Nervous System

Answer 10

Only consists of motor innervation therefore it is also called ‘Visceromotor system’. So it doesn’t pick up sensations from your organs but it just sends out motor commands.
It is divided into sympathetic and parasympathetic division.
Axons of the neurons in the visceral peripheral nervous system innervate smooth muscles of internal organs, blood vessels, glands etc..
Sympathetic system emanates the axons through ; spinal cord, mostly the middle part of the spinal cord.
Parasympathetic system emanates its axons from the brainstem and from the last part (sacral) part of the spinal cord.
Vagus Nerve (X) so nerve 10 : forms part of the parasympathetic system.
Vagus nerve emanates a lot of target organs

Question 11

Hypothalamus

Answer 11

coordinates the bodies basic physiology to make the body suited for what it is about to make.
homeostosis
Hypothalamus is important for the control of visceral nervous system (sympathetic and parasympathetic nervous system).

Question 12

Basal Ganglia

Answer 12

Important for activating certain movements while suppressing others.
Movement initiation
Strength of the movement.
Even though it receives cortical input from many areas in the cortex, it only projects to the supplementary motor area.
Dysfunctions of basal ganglia :
Parkinsons Disease
Huntingtons’ Disease
For tremors : subthalamic nucleus deep brain stimulation.
Basal ganglia is more rostral to thalamus and hypothalamus is below thalamus.
The more anterior you are the more you will see basal ganglia and small thalamus only in the middle, the more you go posterior the more you will see thalamus and hypothalamus.

Question 13

Layers of embryo

Answer 13

• Endoderm : forms internal organs
• Mesoderm : forms bones and muscle
• Ectoderm : forms nervous system and skin

Question 14

Ectoderm

Answer 14

Nervous system is formed from ectoderm.

Question 15

Formation of the Neural Tube

Answer 15

Embryo have neural plate and then it becomes neural groove and the walls of the neural groove is called neural folds.
Neural folds start to fuse dorsally and towards each other and they form ‘neural tube’ : and neural folds start to close.

Question 16

Neural Tube

Answer 16

Entire Central Nervous System develops from the neural tube (walls of it)
cerebrospinal fluid containing ventricular system develops from the fluid containing hole in the neural tube.

Question 17

Neuralation

Answer 17

From neural plate to neural tube

Question 18

Three Primary Vesicles

Answer 18

From the most rostral part of the neural tube 3 primary vesicles differentiate and then form the entire brain and from the rest of the neural tube spinal cord is formed. 
Three Primary Vesicles are :
1. Prosencephalon (Forebrain)
2. Mesencephalon (Midbrain)
3. Rhombencephalon (Hindbrain)

Question 19

Differentiation of the prosencephalon (forebrain)

Answer 19

Forebrain differentiates into ;
1. Telencephalon (which forms the cerebral hemispheres, olfactory bulbs, basal telencephalon(which includes basal ganglia))
2. Diencephalon (thalamus and hypothalamus)
3. Optic Cup and Optic Stalk
Optic cup will become retina and optic stalk will become optic nerve.
4. Major white matter systems will develop. So axons that develop from forebrain will extend to other parts of the nervous system.
- Cortical White Matter
- Corpus Callosum (Commissure Fiber)
- Internal Capsule

Question 20

Differentiation of the midbrain

Answer 20

Directly caudal to thalamus.
1. Tectum (dorsal part) :
- Superior colliculus (most anterior 2 colliculus) important for visual processing.
- Inferior Colliculus (auditory processing) caudal to superior colliculus.
2. Tegmentum :
- Substantia Nigra
- Red nucleus (important for the control of voluntary movement)
- Ventral Tegmental Area
In between tectum and tegmenjtum : cerebral aqueduct.

Since cerebral aqueduct is in between tectum and tegmentum and since tegmentum differentiates into substantia nigra, ventral tegmental area, and red nucleus, substantia nigra and VTA must be located caudally to cerebral aqueduct.
Cerebral aqueduct connects the 3rd ventricle with the 4th ventricle.
When you see cerebral aqueduct it means you are in the midbrain.

Question 21

Differentiation of the Hindbrain :

Answer 21

1. Metencephalon : Cerebellum + pons
2. Myelencephalon :
   Medulla

Pons : switchboard connecting cerebral cortex to cerebellum
Cochlear Nuclei also differentiates from the Hindbrain (auditory nuclei)
from Cochlea (inner organ of the ear)
Decussation of axons occur in the hindbrain-especially the medulla.