Neuroscience: CSF and Limbic System

Study Notes

Cerebrospinal fluid (CSF) acts as a protective cushion around the central nervous system (CNS).
CSF is produced by ependymal cells located in the choroid plexuses within the ventricles of the brain.
CSF fills the ventricles of the brain, the central canal of the spinal cord, and the subarachnoid space.
CSF flows through the ventricles in a specific order: lateral ventricles, third ventricle, cerebral aqueduct, and fourth ventricle.
A small amount of CSF enters the central canal of the spinal cord.
CSF exits the fourth ventricle via openings in its walls and roof entering the subarachnoid space.
Arachnoid granulations penetrate the superior sagittal sinus, allowing CSF to pass from the subarachnoid space into the blood.

The limbic system is a group of structures in the brain that are involved in emotion, memory, and motivation.
Some important structures in the limbic system include the amygdala, hippocampus, and hypothalamus.
The amygdala is involved in processing emotions, especially fear.
The hippocampus is important for memory formation, particularly long-term memories.
The hypothalamus is involved in regulating basic bodily functions such as hunger, thirst, and temperature.

Cranial nerves are pairs of nerves that emerge directly from the brain.
There are 12 pairs of cranial nerves, each with specific functions.
Cranial Nerve VII (Facial): Sensory for taste and motor for facial expression.
Cranial Nerve VIII (Vestibulocochlear): Sensory for hearing and equilibrium.
Cranial Nerve IX (Glossopharyngeal): Sensory for taste and motor for swallowing.
Cranial Nerve X (Vagus): Sensory and motor for organs in the thoracic and abdominal cavities.
Cranial Nerve XI (Accessory): Motor for the trapezius, sternocleidomastoid, and muscles of the larynx.

The gray matter of the spinal cord has a letter H shape with horns.
The spinal cord contains fluid-filled cavities called ventricles.
The spinal cord is surrounded by meninges, which are protective membranes.
The spinal cord receives sensory information from the body and sends motor commands to muscles and glands.
The spinal cord is also involved in reflexes, such as the withdrawal reflex.

Spinal nerves arise from the spinal cord, connecting it to the rest of the body.
Spinal nerves contain axons of both sensory and motor neurons.
Spinal nerves are categorized by the region of the vertebral column from which they emerge (e.g., cervical, thoracic, lumbar, sacral).
There are 31 pairs of spinal nerves.
Spinal nerves are organized into three major plexuses: cervical, brachial, and lumbosacral.

A dermatome is the area of skin supplied with sensory innervation by a pair of spinal nerves.
Each spinal nerve (except C1) has a specific cutaneous sensory distribution, which is responsible for feeling sensations within a specific area of the skin.

The autonomic nervous system regulates involuntary bodily functions such as heart rate, digestion, and breathing.
It's divided into two branches: sympathetic and parasympathetic.
The sympathetic division prepares the body for physical activity ("fight or flight").
The parasympathetic division conserves energy and promotes bodily maintenance ("rest and digest").

Sympathetic preganglionic neurons originate in the lateral horn of the spinal cord between T1 and L2 segments.
Their axons travel through ventral roots to either sympathetic chain ganglia or collateral ganglia.

Some parasympathetic preganglionic neurons originate in the lateral part of the central gray matter of the spinal cord (S2-S4).
Others originate in brainstem nuclei associated with cranial nerves (oculomotor, facial, glossopharyngeal, vagus).
Axons extend to terminal ganglia near effector organs in the head, or embedded within the walls of effector organs in the thorax, abdomen, and pelvis.
The vagus nerve supplies most thoracic and abdominal organs.