Emily's A&P blogger

Cranial Nerve X The Vagus Nerve

2006-05-12T06:27:00.000-07:00

http://www.meddean.luc.edu/lumen/meded/GrossAnatomy/h_n/cn/cn1/cn10.htm

The Vagus Nerve- this is a mixed root nerve that is distributed from the head and neck into the thorax and abdomen. It has a more extensive course and distribution than any of the other cranial nerves

<---Here is a picture of where the vagus nerve, the longest cranial nerve, starts from. It is in the brain stem (in the medulla) and travels to organs in the neck, thorax and abdomen. What is the route of the nerve to leave the cranium? The route of the vagus nerve leaving the cranium is from the rootlets of the medulla oblongata. They arise from nuclei of the medulla.

Where does the nerve then travel? The nerves sensory axons arise at the skin of the external ear, a few taste buds in the epiglottis and pharynx, and in muscles of the neck and throat. (in prioreceptors). sensory axons also come from receptors in the carotid sinus, and carotid body, near the carotid arteries, receptors near the aortic body, and visceral receptors in most of the organs of the thoracic and abdominal cavities. What are the the targets or organs/structures that the vagus nerve serves? The organs that the vagus nerve serves are : The heart, lungs, liver and gallbladder, stomach, and the small and large intestine. All of these organs, as we already know are extremely important to human life.

http://en.wikipedia.org/wiki/Image:Gray793.png
Here is a picture that shows just how far the vagus nerve goes from the medulla stem all the way down to organs of the urinary system. ( hence it is the longest cranial nerve in the body)

What is the function of each of these targets? The Vagus nerve is responsible for such actions as: heart rate, peristalsis, sweating, a a few muscle movements, such as speech, and keeping the larynx open for breathing. For the heart- the parasympathetic part is medaited by the vagus nerve.

*(At the location of the left vagus: " Otto Loewi first proved that nerves secrete substances called neurotransmitters which have effects on receptors in target tissues. Loewi described the substance released by the vagus nerve as vagusstoff, which was later found to be acetylcholine.")*
From:http://en.wikipedia.org/wiki/Vagus_nerve

For each targets, are they sensory or motor neurons? Somatic or visceral neurons?

The vagus nerve consists of five components with distinct functions:
Brancial motor(special visceral efferent)
Supplies the voluntary muscles of the pharynx and most of the larynx, as well as one extrinsic muscle of the tongue.

Visceral motor(general visceral efferent)
Parasympathetic innervation of the smooth muscle and glands of the pharynx, larynx, and viscera of the thorax and abdomen.

Visceral sensory(general visceral afferent)
Provides visceral sensory information from the larynx, esophagus, trachea, and abdominal and thoracic viscera, as well as the stretch receptors of the aortic arch and chemoreceptors of the aortic bodies .

General sensory(general somatic afferent)
Provides general sensory information from the skin of the back of the ear and external auditory meatus, parts of the external surface of the tympanic membrane, and the pharynx.

Special sensory(special afferent)
A very minor component of CN X. Provides taste sensation from the epiglottic region. This component will not be discussed further.

The Upper Limb

2006-04-10T06:09:00.000-07:00

(here is a cross section of the upper limb)http://www.meddean.luc.edu/lumen/meded/GrossAnatomy/cross_section/vhpue/vhpue.html

What is the Upper Limb? It consists of thirty separate bones, several muscles, nerves, and joints.

The skeletal elements a.k.a. the bones form the framework of the upper body. These bones are described as the arm, forearm and hand.

(As previously learned: All bone is formed by osteoblasts. They serve 4 main purposes: Support & movement, protection, mineral storage and blood cell development-long bone marrow. Bony tissue is made up of 35% collageb and 65% inorganic calcium)

The bones of the upper limb are described regionally as a bone of the arm, forearm, or hand.

The Peripheral Nervous System

2006-03-20T05:00:00.000-08:00

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PNS.html

The NERVOUS SYSTEM is the master controlling and communicating system of the body. (brain and spinal column)

The PERIPHERAL NERVOUS SYSTEM (PNS) is the part of the nervous system outside the central nervous system (CNS) it consists mainly of the nerves that extend from the brain and spinal cord. Peripheral nerves are the communication lines that link all parts of the body to the CNS. (Human A&P 6th Ed. Elaine N. Marieb) They are the cranial and the spinal nerves.

2 Functional Subdivisions of the Peripheral Nervous Sytem:

1.Sensory (afferent) Division: consisting of nerve fibers that convey impulses to the CNS from sensory receptors located throughout the body.
The fibers that convey impulses from the skin, skeletal muscles, and joints are called somatic afferent fibers.
The fibers that transmit impulses from the visceral organs (within the ventral body cavity) are called visceral afferent fibers. The sensory fibers keep the CNS informed of the events going on both in and out of the body.

2. Motor (efferent) Division: transmits impulses from the CNS to effector organs, the muscles and the glands. Activation of muscle contraction and glands secreting is made by this division. They effect these organs in order to bring about a motor response.

The motor, or efferent Division also has 2 parts:
Somatic nervous system: composed of somatic nerve fibers that conduct impulses from the CNS to skeletal muscles. It is also often referred to as the voluntary nervous system; allowing us to consciously control our skeletal muscles.
Autonomic nervous system: visceral motor nerve fibers that regulate the activity of smooth muscles, cardiac muscles. and glands. It is also referred to as the involuntary nervous system
because we can not control activites like, the pumping of our heart and the movement of food through our digestive tract.
The ANS also has two functional subdivisions: Sympathetic and Parasympathetic; working in opposition to each other; what one division stimulates, the other inhibits.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CNS.html#White_Matter_vs._Gray_Matter

The Spinal Nerves: 31 pairs of spinal nerves all contain thousands of nerve fibers arise from the spinal cord and supply all parts of gthe body except for the head and some parts of the neck. These nerves are named according to their point of placement on the spinal cord: C1-C8 are cervical spinal nerves, T1-T12 are thoracic nerves, L1-L5 are Lumbar nerves, S1-S5 are sacral nerves, and 1 pair of coccygeal nerves C0.

Each spinal nerve connects to the spinal cord through a ventral and a dorsal root.
Ventral Roots: contain MOTOR (efferent) fibers that arise from the anterior horn of the nerve.
Dorsal roots: contain SENSORY (afferent) fibers thjat arise from the sensory neurons in the dorsal root ganglia.

All of the spinal nerves are "mixed"; that is, they contain both sensory and motor neurons.
All our conscious awareness of the external environment and all our motor activity to cope with it operate through the sensory-somatic division of the PNS.

all the sensory axons pass into the dorsal root ganglion where their cell bodies are located and then on into the spinal cord itself.
all the motor axons pass into the ventral roots before uniting with the sensory axons to form the mixed nerves.The spinal cord carries out two main functions:
It connects a large part of the peripheral nervous system to the brain. Information (nerve impulses) reaching the spinal cord through sensory neurons are transmitted up into the brain. Signals arising in the motor areas of the brain travel back down the cord and leave in the motor neurons.
The spinal cord also acts as a minor coordinating center responsible for some simple reflexes.http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CNS.html#White_Matter_vs._Gray_Matter

Tissues

2006-02-26T18:21:00.000-08:00

TISSUES OF THE HUMAN BODY

Tissues Cells group together in the body to form tissues - a collection of similar cells that group together to perform a specialized function. There are 4 primary tissue types in the human body: epithelial tissue, connective tissue, muscle tissue and nerve tissue.

Epithelial Tissue - The cells of epithelial tissue pack tightly together and form continuous sheets that serve as linings in different parts of the body. Epithelial tissue serve as membranes lining organs and helping to keep the body's organs separate, in place and protected. Some examples of epithelial tissue are the outer layer of the skin, the inside of the mouth and stomach, and the tissue surrounding the body's organs. Epithelia are tissues that serve as protective layers and/or secretory components of body organs and systems. Most epithelia possess common characteristics that contribute to their functional capabilities. There are many kinds of epithelial tissues having different shaped and sizes, below I have displayed a picture of the most simple tpye of epithelia.

Simple squamous epithelia: A single layer of flattened cells resting on connective tissues. These flattened cells are espescially found in thin barriers where the exchange of nutrients, wastes, or respiratory gases takes place.
Other types of epithelial tissues that have different shapes and size are:

Simple cuboidal epithelia, Simple columnar epithelia, Pseudostratified epithelium, etc...
All of these tissues line different places of the body such as the kidneys.

http://www.mhhe.com/biosci/ap/histology_mh/simpleep.html#simple hhe.com/biosci/ap/histology_mh/simpleep.html#simple

Connective Tissue - There are many types of connective tissue in the body. Generally speaking, connective tissue adds support and structure to the body. Most types of connective tissue contain fibrous strands of the protein collagen that add strength to connective tissue. Some examples of connective tissue include the inner layers of skin, tendons, ligaments, cartilage, bone and fat tissue. In addition to these more recognizable forms of connective tissue, blood is also considered a form of connective tissue.

Muscle Tissue - Muscle tissue is a specialized tissue that can contract. Muscle tissue contains the specialized proteins actin and myosin that slide past one another and allow movement. Examples of muscle tissue are contained in the muscles throughout your body. There are alos subtypes of the muscle tissues, they can either be, smooth, skeletal or cardiac.
Each of these subtypes serves a different function in the body.

Smooth Muscle Tissue- forms the muscle layers in the walls of hollow organs such as the digestive tract (lower part of the oesophagus, stomach and intestines), the walls of the bladder, the uterus, various ducts of glands and the walls of blood vessels .

Skeletal Muscle Tissue-Skeletal muscle is the most abundant tissue in the vertebrate body. These muscles are attached to and bring about the movement of the various bones of the skeleton, hence the name skeletal muscles.

Cardiac Muscle Tissue-This is a unique tissue found only in the walls of the heart.Cardiac muscle tissue plays the most important role in the contraction of the atria and ventricles of the heart.
It causes the rhythmical beating of the heart, circulating the blood and its contents throughout the body as a consequence.

Nerve Tissue - Nerve tissue contains two types of cells: neurons and glial cells. Nerve tissue has the ability to generate and conduct electrical signals in the body. These electrical messages are managed by nerve tissue in the brain and transmitted down the spinal cord to the body.Although the nervous system is very complex, there are only two main types of cells in nerve tissue. The actual nerve cell is the neuron. It is the "conducting" cell that transmits impulses and the structural unit of the nervous system. The other type of cell is neuroglia, or glial, cell. The word "neuroglia" means "nerve glue." These cells are nonconductive and provide a support system for the neurons. They are a special type of "connective tissue" for the nervous system. http://training.seer.cancer.gov/module_anatomy/unit5_2_nerve_tissue.html

The Basic Human Body plan

2006-02-26T13:13:00.000-08:00

The Systems of the Human Body.

There are 11 body systems throughout our body that all work together in a system called HOMEOSTASIS which is the ability to maintain stable internal conditions although there are constant outside changes.

The 11 systems are as follows:
(Text, ch.1 Elaine Marieb 6-7)

Integumentary System- Forms the external body coveringand protects deeper tissues from injury.

Skeletal system- Protects and supports body organs.

Muscular System- Allows manipulation of the environment, locomotion, and facial expression; maintains posture; produces heat.

Nervous System- The fast acting control system of the body.

Endocrine system- The glands that secrete hormones that regulate processes such as growth, reproduction, and nutrition.

Cardiovascular System- the blood vessels transport blood, which carries oxygen, co2, nutrients, wastes, and etc...

Lymphatic system- Picks up the fluid that leaks from blood vessels and returns it to the blood; disposes of debris, houses WBC's.

Respiratory system- Keeps the blood constantly supplied with o2 and removes co2.

Digestive System- Breaks down food into absorbable units that enter the blood for distribution to body cells.

Urinary System- Eliminates nitrogenous wastes from the body; regulates water, electrolyte and acid-base balanec of the blood.

Male/Female reproductive System- Overall function is producind offspring. Male testes produces sperm and male sex hormone; ducts and glands aid in delivery of sperm to the female reproductive tract. Ovaries produce eggs and female sex hormones; remaining structures serve as sites for fertilization and development of fetus.

The human body has certain levels of structural organization which go from simplest to largest: (for some reason I started with the larger body systems, rather than starting at the cellular level.)

In the CHEMICAL LEVEL (the smallest level) atoms form molecules. Examples are, water and proteins. These molecules turn to form organelles, these are all basic components in the the smallest units of living things we call cells. The CELLULAR LEVEL and the simplest living creatures are composed of single cells, but in the more complex organisms the heirarchy turns into the TISSUE LEVEL. Tissues are groups of similar cells that have a common function. The four basic types are: epithelium, muscle, connective, and nervous.
The next level of structural organization is the ORGAN LEVEL; an organ is a structure composed of at least two tissue types that performs a specific function for the body. The next level of organization is the ORGAN SYSTEM; these systems work together to accomplish a common purpose.

Microscpoic picture of a human epithelial cell.
(stained for keratin in green and DNA in the red)
http://en.wikipedia.org/wiki/Cell_%28biology%29

Cells are the basic component of human like, this is exactly what we are made up of and continue to grow and reproduce subconsciously. The growth begins at the point when the sperm meets the egg, it is then that you may say a human life exisits. Growth and human development occurs in every orgam system of the body.

The following statement comes from a great internet resource that explains the stages of growth.

"The changes occurring between implantation, a six-weeks embryo, a six months fetus, a one week-old child, or a mature adult are merely stages of development and maturation."—http://www.pathlights.com/abortion/abort03.htm

2006-01-23T07:31:00.000-08:00

Emily Kelley
Boston/Ma May 14, 1985
Alkaline Trio
Here for dental hygiene
I have 3 brothers, and 1 sister; I am the middle child of 5

digital native score: 8