The Nervous System

Prepared by Mickelder Kercy, MD - Instructor

Central Nervous System(CNS) : Brain and Spinal Cord

Peripheral Nervous System(PNS) : Autonomic Nervous

System (Sympathetic and Parasympathetic Nervous

System) and the Somatic Nervous System

(The PNS is made up of Nerves connecting the CNS to

the rest of the body)

Structure of the Nervous System

Motor Neurons

Sensory Neurons

Interneurons

Types of nerve cells or fibers

Efferent nerves fibers/cells that cause muscles to

contract, glands to secrete and organs to function

properly

Motor Neurons

Afferent nerves cells/fibers that carry our feelings

(heat/ pain/ cold etc..) to the Central Nervous System

Sensory Neurons

Neurons that form a connection between other

neurons (e.g. in-between a motor and a sensory nerve

cell/fiber. They are neither motor nor sensory neurons

Interneurons

Junction where neurons pass neurotransmitters (chemical

signals) or electrical signals to other neurons, muscle

cells, or gland cells. Composed of:

- A presynaptic ending that contains mitochondria, other

cell organelles and neurotransmitters that are released

in the synaptic space

- A synaptic space or cleft between the presynaptic and

postsynaptic endings

- A postsynaptic ending on the target cell (other neuron/

muscle cells/gland cells) that contains receptor sites for

the neurotransmitters that crossed the synaptic space

Synapse

Several small molecules function as neurotransmitters.

- Glycine and glutamate (amino acids)

- Dopamine (DA), Norepinephrine (NE) & Dopamine

(DA) (cathecholamines derived from amino acids)

- Acetylcholine (ACh) & Serotonin (derived from

amino acids)

- Prostaglandins, Histamine and Y- Aminobutyric

acid (GABA) are other neurotransmitters

Brain : The outside is covered with gray matter and

the inside is filled with white matter

Spinal Cord : Gray matter forms an H shape in the

inside and white matter surrounds the gray matter

Central Nervous System

Protected by- Cranium/Skull

Meninges (Pia Mater, Arachnoid and

Dura Mater)

Cerebrospinal fluid (water, glucose,

protein, sodium, chloride and nutrients such as oxygen)

Blood brain barrier (glial astrocytes and

capillary cells)

Divided into the Cerebrum, the Diencephalon, the Brainstem and the Cerebellum

Brain

Divided into the right and left Cerebral Hemispheres

Contains convolutions/ gyri, sulcus and fissures

Controls all sensory and motor activity

Cortex is divided into the Frontal lobe, R & L

Parietal lobes, R & L Temporal lobes and the

Occipital lobe covered each by bones bearing the

same name

Cerebrum

Frontal Lobe : Executive function (speaking, learning,

reasoning, problem solving, judging, planning),

Voluntary motor activity, Emotion and Behavior

Parietal Lobe : Pain, Pressure, T°, Touch and Speech /

Language comprehension

Temporal Lobe : Memory, Hearing, Taste, Speech

Reading, Writing and Arithmetic

Occipital Lobe : Vision

Divided into the Thalamus (relays all sensory impulses

to the cerebrum) and the Hypothalamus (regulates body

temperature)

Diencephalon

Divided into the midbrain, the pons and the medulla

oblongata

Brainstem

Midbrain : Relays information for vision and hearing

Pons : Regulates the change from inspiration to expiration

Medulla Oblongata : Regulates several functions of the autonomic nervous system

- Respiration (chemoreceptors)

- Cardiac center (sympathetic, parasympathetic system)

- Vasomotor center (baroreceptors)

- Reflex centers of vomiting, coughing, sneezing, and

swallowing

Located in the back of the skull (coordination of

movement)

Cerebellum

Links the Brain with the rest of the body

Protected by – Vertebrae

Meninges (Pia mater, Arachnoid,

Dura mater)

Cerebrospinal fluid (water, glucose,

sodium, chloride and nutrients such as oxygen)

Blood-brain barrier (glial astrocytes

and capillary cells)

Spinal Cord

Somatic Nervous System : 12 pairs of cranial nerves,

8 pairs of cervical spinal nerves, 12 pairs of thoracic

spinal nerves, 5 pairs of lumbar spinal nerves, 5 pairs

of sacral spinal nerves and 1 pair of coccygeal nerves

Autonomic Nervous System : Divided into the

Sympathetic Nervous System and the

Parasympathetic Nervous

Peripheral Nervous System

Cranial Nerves

Cervical, Thoracic, Lumbar, Sacral & Coccygeal Nerves

SNS : Stimulates the adrenal gland to release epinephrine that prepares the body for Fight and Flight during stressful situation (Pupil dilation, Sweating, ↑RR, dilates bronchi, ↑HR and ↑BP)

PNS : Works during non-stressful situations

(Pupil constriction, not sweating, ↓RR, bronchi

constriction, ↓HR, ↓BP) and innervates the

digestive system (↑salivation, ↑ digestive

organs motility, ↑gallblader and bladder

contraction and relaxes the bladder sphincter )

Alzheimer’s Disease : Destruction of nerve cells in

the brain causing loss of recent memory

Amyotrophic Lateral Sclerosis : Destruction of the

motor nerves in the brain causing movement

impairment. Also called Lou Gehrig’s disease

Common Disorders associated with the Nervous System

Bell’s Palsy : Weakness or paralysis of the muscles that

control expression on one side of the face

Disk Disorders : When the intervertebral disks

deteriorate causing pain and shortening of height

Encephalitis : Inflammation of the brain

Epilepsy and seizures : Interference of electrical

impulses within the brain causing uncontrollable

movement of the limbs and body

Migraine Headache : flashes of light, blind spots,

tingling in your arm/leg or sensitivity to light/noise

often precedes the headache

Tension Headache : Due to stress

Cluster Headache : Felt behind the eyes or temples.

May last for weeks to months than stops (cycle)

Post-Traumatic Headache : Post trauma

Huntington’s Chorea : Hereditary disease affecting

the cerebral and basal ganglia causing imbalance,

lack of coordination, difficulty swallowing and

rigidity

Hydrocephalus : Excessive amount of Cerebro-

spinal fluid in the ventricles of the brain

Meningitis : Inflammation of the meninges that

surround the brain and the spinal cord

Multiple Sclerosis : Body’s antibodies become

confused and attack the myelin sheath surrounding

the nerves in the brain and spinal cord causing vision,

sensation and movement impairment

Neuralgia : Nerve pain

Parkinson’s Disease : Degeneration of nerves in the

basal ganglia causing a loss of dopamine resulting in

the lack of movement control

Sciatica : Pain running down the sciatic nerve

Spina Bifida : Failure of the spine to close properly

during the 1st month of pregnancy

Spinal cord Injuries : Quadriplegia, Paraplegia and

Hemiplegia

Stroke : Cerebro-vascular accident due to ↓ or

cessation of blood flow to the brain

Transient Ischemic attack : Mini-strokes lasting a few

minutes

Concussion : Injury caused by a blow to the head.

May lead to a loos of consciousness

Contusion : Bruising of the brain

The End