Nerves control the body’s functions including the vital organs, sensation, and movement. The nervous system receives information and initiates an appropriate response. It is affected by internal and external factors.

spinal cord, brain and neurons are all parts of your central nervous system (CNS). spinal cord is connected to medulla and is the connection center for the reflexes as well as the afferent (sensory motor) pathways for most of the body below the head and neck. The spinal cord begins at the brainstem and ends at about the second lumbar vertebra. Sensory neurons have their cell bodies in the spinal (dorsal root) ganglion. Their axons travel through the dorsal root into the gray matter of the cord.

Peripheral Nervous System (PNS) The CNS extends to the Peripheral Nervous System, a system of nerves that branch beyond the spinal cord, brain, and brainstem. The PNS carries information to and from the CNS. The PNS includes: 1.Somatic Nervous System (SNS) Nerves, skin 2. Autonomic Nervous System (ANS). i.The somatic nervous system includes the nerves serving the musculoskeletal system and the skin. It is voluntary and reacts to outside stimuli affecting the body. ii.The autonomic nervous system is involuntary automatically seeking to maintain homeostasis or normal function.

ventral root pia mater dura mater arachnoid grey matter dorsal root white matter spinal nerves

Cerebrospinal Fluid (CSF) It is a clear fluid found in the brain chambers Ventricles, spinal canal, and spinal cord. This fluid is secreted from the Choroids Plexus, a vascular part in the ventricles of the brain. Meninges Meninges are membranes that cover and protect the brain and spinal cord. There are three primary types: (1) Dura Mater, (2) Arachnoid Mater, (3) Pia Mater.

1.The dura mater, or dura, is the gray outer layer of the spinal cord and nerve roots. It is made of strong connective tissue. 2.The arachnoid mater, resembles a loosely woven fabric of arteries and veins. This layer is thinner than the dura mater. The Subarachnoid space is filled with cerebrospinal fluid. 3.The pia mater, is the innermost layer and is a delicate and highly vascular membrane providing blood to the neural structures.

sensory pathway motor pathway

ganglion - a collection of cell bodies located outside the C N S. The spinal ganglia or dorsal root ganglia contain the cell bodies of sensory neurons entering the cord at that region. nerve - a group of fibers (axons) outside the CNS. The spinal nerves contain the fibers of the sensory and motor neurons. A nerve does not contain cell bodies. They are located in the ganglion (sensory) or in the gray matter (motor). tract - a group of fibers inside the CNS. The spinal tracts carry information up or down the spinal cord, to or from the brain. Tracts within the brain carry information from one place to another within the brain. Tracts are always part of white matter.

Different levels of spine control different regions of the body.

Spinal nerves join in at plexuses which is aninterconnection of fibers which form new combinations as the "named" or peripheral nerves (PNS).There are four voluntary plexuses 1.cervical plexus:  phrenic nerve travels through the thorax to innervate the diaphragm 2.Thorachial plexus:  Axillary nerve - innervates the deltoid muscle and shoulder, along with the posterior aspect of the upper arm. Musculocutaneous nerve - innervates anterior skin of upper arm and elbow flexors.  Radial nerve - innervates dorsal aspect of the arm and extensors of the elbow, wrist, and fingers, abduction of thumb.  Median nerve - innervates the middle elbow, wrist and finger flexors, adducts the thumb.  Ulnar nerve - innervates the medial aspect wrist and finger flexors.

3. lumbar plexus:  genitofemoral - to the external genitalia  obturator - to the adductor muscles  femoral - innervates the skin, muscles of upper thigh, and quadriceps. 4. sacral plexus:  gluteal nerves (superior and inferior) - superior innervates the gluteus medius and minimus, inferior innervates the gluteus maximus.  sciatic nerve - the body's largest nerve, consisting of two major branches, the tibial and common peroneal. Together they innervate most all of leg including the flexors of the knee, part of adductor magnus, muscles for plantar flexion, dorsiflexion, and other movements of the foot and toes.

sensory neuron takes nerve impulses to the CNS, motor neurons take nerve impulses away from the CNS effectors carry out the responses to environmental changes. All neurons have cell body, dendrites, and an axon. A protective layer called a myelin sheath covers many axons and in the PNS this covering is formed by Schwann cells. The gaps in an axon where there is no myelin sheath are called nodes of Ranvier. Long axons are more likely to have a myelin sheath. The myelin sheath helps with nerve regeneration in the PNS.

Structure of a typical neuron

 It is a junction that permits a neuron to pass an electrical or chemical signal to another cell.  In many synapses, the presynaptic part is located on an axon, but some are located on a dendrite or soma.

There are two fundamentally different types of synapse: 1.In a chemical synapse, the presynaptic neuron releases a chemical called a neurotransmitter that binds to receptors located in the postsynaptic cell, usually embedded in the plasma membrane. 2.In an electrical synapse, the presynaptic and postsynaptic cell membranes are connected by channels that are capable of passing electrical current, causing voltage changes in the presynaptic cell to induce voltage changes in the postsynaptic cell.

Terms: The brainstem contains the midbrain and the medulla oblongata which regulates heartbeat, breathing, and blood pressure. A dorsal root ganglion is the cell body of a sensory neuron. The sympathetic division kicks in in emergency situations, accelerating the heartbeat and dilating the bronchi. The parasympathetic division promotes all of the internal responses coming from a relaxed state. Sensory receptors generate nerve impulses. synaptic cleft The very narrow gap that lies between two nerve cells at the synapse and a nerve impulse must cross (from the presynaptic to postsynaptic side) in order to stimulate the next nerve cell.

Terms: ganglion - a collection of cell bodies located outside the Central Nervous System. The spinal ganglia or dorsal root ganglia contain the cell bodies of sensory neurons entering the cord at that region. nerve - a group of fibers (axons) outside the CNS. The spinal nerves contain the fibers of the sensory and motor neurons. A nerve does not contain cell bodies. They are located in the ganglion (sensory) or in the gray matter (motor). tract - a group of fibers inside the CNS. The spinal tracts carry information up or down the spinal cord, to or from the brain. Tracts within the brain carry information from one place to another within the brain. Tracts are always part of white matter. gray matter - an area of unmyelinated neurons where cell bodies and synapses occur. In the spinal cord the synapses between sensory and motor and interneurons occurs in the gray matter. The cell bodies of the interneurons and motor neurons also are found in the gray matter. white matter - an area of myelinated fiber tracts. Myelination in the CNS differs from that in nerves.

The Spinal Cord is a very important part of the CNS. When Spinal Cord is damaged, then the sensory information going to, and the motor information going from the Spinal Cord can be damaged. Most Spinal injuries  spinal stenosis is a disease where the spinal cord and nerves are compressed. Spinal stenosis is caused by tumors, osteoporosis, and spinal disk herination. There are two types of spinal stenosis 1. Cervical spinal stenosis 2.Lumbar spinal stenosis.

9-The axon terminal contains synapses, specialized structures where chemicals are released in order to communicate with target neurons. A-Dopamine B-Neuromodulation C-Oxytocin D-Neurotransmitter 10- White matter is composed of bundles of myelinated nerve cell processes which connect various grey matter areas of the brain to each other, and carry nerve impulses between neurons. A-Alpha motor neuron B-Nervous system C-Schwann cell D-Axon 11- Neurons receive, send, and process information A-True B-False

1- dendrite 2- cell body 3- nucleus 4-axon 5-myelin sheath 6- schwann cell 7- node of ranvier 8- axon terminal 9-D 10-D 11-A