Brain Nerves

Cerebral Arteriosclerosis is the result of thickening and hardening of the walls of the arteries in the brain. Symptoms of cerebral arteriosclerosis include headache, facial pain, and impaired vision. If the walls of an artery are too thick, or a blood clot becomes caught in the narrow passage, blood flow to the brain can become blocked and cause an ischemic stroke. When the thickening and hardening is uneven, arterial walls can develop bulges (called aneurysms). If a bulge ruptures, bleeding in the brain can cause a hemorrhagic stroke. Both types of strokes can be fatal.

Cerebral arteriosclerosis is also related to a condition known as vascular dementia, in which small, symptom-free strokes cause cumulative damage and death to neurons (nerve cells) in the brain. Personality changes in the elderly, such as apathy, weeping, transient befuddlement, or irritability, might indicate that cerebral arteriosclerosis is present in the brain. Computer tomography (CT) and magnetic resonance imaging (MRI) of the brain can help reveal the presence of cerebral arteriosclerosis before ischemic strokes, hemorrhagic strokes, or vascular dementia develop.

Cranial Nerves  Spinal nerves emerge sequentially from the spinal cord with the spinal nerve closest to the head (C1) emerging in the space above the first cervical vertebra. The cranial nerves emerge from the central nervous system above this level.  Each cranial nerve is paired and is present on both sides. The numbering of the cranial nerves are based on the order in which they emerge from the brain, from the front to back of the brainstem.

The terminal nerves, olfactory nerves (I) and optic nerves (II) emerge from the cerebrum or forebrain, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain. The cranial nerves are considered components of the peripheral nervous system. However, on a structural level, the olfactory, optic, and terminal nerves are more accurately considered part of the central nervous system.

Cranial Nerve l, Olfactory; This nerve is instrumental for the sense of smell. It is one of the few nerves that are capable of regeneration.

Cranial Nerve II, Optic; This nerve carries visual information from the retina of the eye to the brain.

Cranial Nerve III, Oculomotor; This controls most of the eye’s movements, the constriction of the pupil, and maintains an open eyelid.

Cranial Nerve IV, Trochlear; A motor nerve that innervates the superior oblique muscle of the eye, which controls rotational movement.

Cranial Nerve V, Trigeminal; This is responsible for sensation and motor function in the face and mouth.

Cranial Nerve VI, Abducens; A motor nerve that innervates the lateral rectus muscle of the eye, which controls lateral movement.

Cranial Nerve VII, Facial; This controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity.

Cranial Nerve VIII, Vestibulocochlear; This is responsible for transmitting sound and equilibrium (balance) information from the inner ear to the brain.

Cranial Nerve IX, Glossopharyngeal; This nerve receives sensory information from the tonsils, the pharynx, the middle ear, and the rest of the tongue.

Cranial Nerve X, Vagus; The vagus nerve can be thought of a superhighway that connects your body and your brain. It innervates most organs in the body; the messages zip along its five lanes of traffic with four lanes delivering information from the body to the brain and one lane moving information from the brain to the body. This is the most obvious physical representation of the mind-body connection. The vagus nerve both senses your internal environment (via its sensory neurons) and affects it (via its motor neurons). Some of the functions of the vagus nerve have been long established, while others were discovered only recently.

Here is what we know about the vagus nerve so far:  

1. It is intimately involved in managing sympathetic/parasympathetic balance in the autonomic nervous system (ANS).  Here is a quick reminder how ANS works.

The vagus nerve provides 75% of all parasympathetic outflow. When the brain triggers parasympathetic activation, the vagus nerve carries the messages to the heart (decreasing the heart rate and blood pressure), to the lungs (to constrict the respiratory passageways), to every organ in the digestive system (to increase motility and blood flow to the digestive tract, to promote defecation), to the kidneys and bladder (to promote urination) and to reproductive organs (to aid in sexual arousal).

2. It communicates messages between the gut and the brain. 80% of the vagus nerve’s fibers (4 out of 5 traffic lanes) deliver information from the enteric nervous system (the second brain in the gut) to the brain.

3. It regulates the muscle movement necessary to keep you breathing. Your brain communicates with your diaphragm via the release of the neurotransmitter acetylcholine from the vagus nerve to keep you breathing. If the vagus nerve stops releasing acetylcholine, you will stop breathing.

4. It helps decrease inflammation. This occurs through the release of the neurotransmitter acetylcholine.

5. It has profound control over heart rate and blood pressure. For example, patients with heart failure, in which the heart fails to pump enough blood through the body, tend to have less active vagus nerves.

6. It helps improve your mood. Research shows that stimulation of the vagus nerve can be an effective treatment for chronic depression that has failed to respond to other treatments.

7. It is essential in fear management. Remember that “gut instinct” that tells you when something isn’t right? Turns out that the vagus nerve plays a major role in that. The signals from your gut get sent to the brain via the vagus nerve, and the signals from the brain travel back to the gut, forming a feedback loop. Healthy functioning of the vagus nerve helps us bounce back from stressful situations and overcome fear conditioning.

8. It plays a role in learning and memory. The vagus nerve facilitates learning and re-wiring, so to speak. New findings about the vagus nerve offer exciting possibilities for the treatment of post-traumatic stress disorder (PTSD). Stimulation of the vagus nerve might be able to speed up the process by which people with PTSD can learn to reassociate a non-threatening stimuli which triggers anxiety with a neutral and non-traumatic experience”. It can also help with healing sexual stress and trauma.

9. It can help relieve cluster headaches.

Cranial Nerve XI, Spinal accessory; This nerve controls specific muscles of the shoulder and neck.

Cranial Nerve XII, Hypoglossal nerve; This nerve controls the tongue movements of speech, food manipulation, and swallowing.

Memory Index (ZS); reflects the strength of a person’s memory. Cerebral arteriosclerosis, cerebral atrophy and others will lead to insufficient blood supply to the brain. The functional declination of hippocampal cells in the brain is the histological reason for memory decline in the elderly. Memory is divided into two kinds: one is auditory memory and visual memory.

Levels:  If the Memory Index readings are high this may indicate impaired short term memory.  If the Memory Index readings are low this may indicate impaired long term memory.

Parasymapthetic Nervous System function; (usually abbreviated PSNS, not PNS, to avoid confusion with the peripheral nervous system) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and enteric nervous system. The autonomic nervous system is responsible for regulating the body’s unconscious actions. The parasympathetic system is responsible for stimulation of “rest-and-digest” or “feed and breed” activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tears), urination, digestion and defecation. Its action is described as being complementary to that of the sympathetic nervous system, which is responsible for stimulating activities associated with the fight-or-flight response.

Nerve fibres of the parasympathetic nervous system arise from the central nervous system. Specific nerves include several cranial nerves, specifically the oculomotor nerve, facial nerve, glossopharyngeal nerve, and vagus nerve. Three spinal nerves in the sacrum (S2-4), commonly referred to as the pelvic splanchnic nerves, also act as parasympathetic nerves. Because of its location, the parasympathetic system is commonly referred to as having “craniosacral outflow”, which stands in contrast to the sympathetic nervous system, which is said to have “thoracolumbar outflow”.

Sympathetic Nervous System function; (SNS) is one of the two main divisions of the autonomic nervous system, the other being the parasympathetic nervous system (PSNS). The autonomic nervous system functions to regulate the body’s unconscious actions. The sympathetic nervous system’s primary process is to stimulate the body’s fight-or-flight response. It is, however, constantly active at a basic level to maintain homeostasis.