Compendium Topic Two

Skeletal and Muscular System

I.  Skeletal System

    Function and Anatomy

    Bone Growth, Remodeling and Repair

    Bones of the Axial Skeleton

    Bones of the Appendicular Skeleton

    Articulations

II.  Muscular System

    Types and Function

     Skeletal muscle Fiber Contraction

     Whole Muscle Contraction

     Muscular Disorder

      Homeostasis

I.  SKELETAL SYSTEM

The skeletal system provides the shape and form for our bodies. It is also important in supporting, protecting, facilitating movement, producing blood for the body, and storing minerals and fat. Bone, cartilage, and fibrous tissue make up this framework.    

Function and Anatomy

It's 206 bones form the basic frame from which soft tissue and organs are attached. As we stand the skeleton supports the body from the legs up. Support comes from the legs bones, to the pelvic girdle, and through the abdominal cavity. The organs in the body are protected by the skeleton. The spinal cord is protected by the vertebrae, the brain by the skull, and the heart and lungs by the rib cage and sternum. Blood cells are produced in the bone marrow. Bones sore minerals such as calcium and phosphorous, and fat is stored in the yellow marrow. 

The long bone is encased by periosteum a connective tissue layer containing blood vessels, lymphatic vessels, and nerves. The length of the bone, the main portion called the diaphysis has a large medullary cavity filled with yellow marrow. The widened areas at the end of the bone are epiphysis, spongy bone containing red bone marrow. It is covered by hyaline cartilage. This is where red bone marrow is made. Along it's length long bone is composed of compact bone. It is made of organized tubular units known as osteocytes. Osteocytes exchange nutrients and wastes with the blood vessels.

Softer than bone cartilage is gel like and contains no blood vessels and nerves. There are three types. Hyaline is found at the ends of long bones, in the nose, ribs, larynx and trachea, and is firm and flexible. In the knees and vertebrae fibrocartilage provides support. Elastic cartilage is the most flexible located in the ear flaps.

The ligaments that connect bone to bone are made of fibrous connective tissue and are also called articulations.

Bone Growth, Remodeling, and Repair

The growth of bone starts at about six weeks and can last till 25. However it can continue to change due to factors of external stress. It's change in shape, size and strength is called remodeling. Different cells are involved in growth, remodeling, and repair. Osteoblasts are bone forming cells and osteocytes are mature bone cells derived from osteoblasts. Osteoclasts break down bone assisting in depositing calcium and phosphate to the blood.

There are two forms of ossification, formation of bone.  In Intramembraneous ossification bones develop between sheets of fibroooous connective tissue. Endochondral ossification replaces cartilage with bone. This is how most of the bones are formed. The stages of ossification change cartilage to bone, then spongy bone is created by osteoblasts further creating the medullary cavity. As the bone lengthens so does the diameter. Once the epiphyseal plates close growth stops.

Specific  hormones are important to the growth of bone. Vitamin D is converted to a hormone in the intestinal tract and is important to the absorption of calcium and growth hormone is essential for overall growth.

The functioning of bone remodeling also promotes homeostasis. The renewal of bone lets the body regulate the amount of calcium in the blood. This is also accomplished by specific hormones. Remodeling happens because osteoblasts form bone and osteoclasts break down bone.

Bone repair is similar to bone growth except in it's first stage. There are four stages. Hematoma, the place of injury where blood clots. Fibrocartilaginous callus then fills the space which eventually becomes bony callus. And the last stage remodeling occurs when new compact bone is built.

Bones of the Axial Skeleton

The axial skeleton lie in the mid- line of the body. These include the skull, hyoid bone, vertebral column, and the rib cage. The skull is made of eight cranial and fourteen facial bones. Cranial bones protect the brain and they are easy to remember because  the major bones bones share the same names as the lobes of the brain. The frontal, parietal, occipital and foramen magnum where the spinal cord joins the base of the skull. Below the parietal bone lies the temporal bone and the sphenoid bone spans the cranium behind the eye sockets. The facial bones consist of the two jaw bones, the mandable and maxillae, the zygomatic bones of the cheekbone, and the nasal bones. 

Within the larynx sits the hyoid bone. It' s purpose is to secure the tongue and is involved in the muscle that allow swallowing.

The vertebral column protects and houses the spinal column. It consists of 33 vertebrae named according to their location and has 4 curvatures to provide resilience and strength. Fibrocartilage can be found between the disks. The cartilage cushions the spine to reduce friction caused by movement.

The rib cage or thoracic cage consists of 12 thoracic vertebrae and 12 pairs of ribs. The upper seven pairs connect to the sternum. The cartilage connecting the ribs to the sternum expand and contract as the lungs breathe.   

      

 Bones of the Appendicular Skeleton

The appendicular skeleton are the appendages that attach to the axial skeleton. It consists of 126 bones functioning to produce movement. The pectoral girdle and upper limb produce flexibility and the lower pelvic girdle and lower limbs stabilize the body and are the strongest bones in the body. For each part there is a left side and a right side. 

  

 Articulations

Where bones meet it forms a joint. there are three types. Fibrous joints cannot move such as in the cranium. Cartilaginous joints in the ribs move slightly and synovial joints are filled with synovial fluid which enables it to move freely. Sacs called bursae  cushion bone and muscle movement. 

II.  MUSCULAR SYSTEM

The human body contains more than 650 muscles which attached to the skeleton which provides us with movement. Each muscle fiber has several nuclei. Skeletal muscle can make up 40% of an adults body weight.

Types and Function

All muscles are able to contract. There are three types of muscle. Smooth muscle is involuntary and has striations and are found in the walls of organs and veins. The heart walls contain cardiac muscle that is striated. Intercalated disks in the membrane have gaps to enable the heart to contract and relax. Skeletal muscle attach to the skeleton made of bundles of muscle fibers and are voluntary. They function to support posture and provide movement. Contraction of the muscle produces heat caused by ATP breakdown, and the pressure created by contraction keep the blood and lymph moving. The muscles also protect the organs as well. The contraction of these muscles at death is called rigor mortis. Whole muscles are made up of bundles of muscle fibers called fascicles. These muscle fibers are surrounded by connective tissue that extends beyond the muscle creating tendons. Skeletal muscles operate in pairs and the nervous system stimulates the group of muscles to provide the right balance of movement.. Thus one muscle that is performing the most work is called the prime mover and the supporting muscles are called the synergists. An example of this is the biceps brachii and the triceps brachii.   

Skeletal muscle Fiber Contraction

The striated features of skeletal muscle  represent the  arrangement of myofilaments in the muscle fiber. There are special  names for the cell components in muscle fiber. The plasma membrane is called the sarcolemma, the cytoplasma is sarcoplasma, and the endoplasmic reticulm is the sarcoplasmic reticulum. A unique feature to the the cell is it's T-tubules that dip into the cell. The expanded areas of the reticulum are calcium storage sites important to muscle contraction. The sarcoplasmic reticulum contains hundreds to thousands of myofibrils, and interestingly contains glycogen and myoglobin. The units of myofibrils make up sacromeres that contain myosinand actin. The filaments act in different ways. Thick filaments are made of myosin and contain myosin heads. The thin filaments are made up of intertwined strands of actin and troponin and tropomyosin. Muscle contraction is created when when the sacromere shortens due to the sliding effect of the actin and myosin filaments. 

Nerve impulses carried by motor neurons can stimulate several muscle fibers because of it's branched  ends. Between the axon terminal and a muscle fiber there is a gap called the synaptic cleft. When the impulse arrives at the axon terminal neurotransmitters are released and diffuses binding to receptors in the sarcolemma. The impulse is then spread over the sarcolemma, down the t-tubules to the sarcoplasmic reticulum. As calcium is released it binds to troponin creating myosin binding sites. ATP is then split  to ADP and P as the myosin head attaches to the actin filament forming a cross bridge. The release of ADP and P creates the pulling action and when ATP again binds to myosin the cycle is repeated. 

Whole Muscle Contraction

Whole muscle contraction is dependent on motor units. It includes the components of nerve fiber with all the muscle fibers it is effecting. Because of this there is a all-or-none law. From the impulse they either contract or they do not. Infrequent impulses cause muscle twitches. Sumation  is increased muscle contraction and tetnus is the maximal sustained motor unit contraction. Intensifying nervous stimulation activates more muscle units. In order to sustain contraction some motor units contract maximally while others are relaxed.

Muscles  have four energy sources. They are triglycerides, fatty acids, glucose, and glycogen. Glycogen and triglycerides are stored i the blood. Muscles require ATP for contraction. There are three ways that muscles to get ATP. One way is by formationof ATP by the creatine phosphate pathway. The second is by fermentation and the third is by cellular respiration. The creatine phosphate pathway is the easiest  and quickest way but is limited in it's storage and available for short term high intensity activities. Fermentationis also fast acting but creates lactate buldup. It creates two ATP from the breakdown of glucose. For lower intesity activities cellular respiration doesn't immediately supply ATP. It is slower because it must be carried through the blood. This process also burns fatty acids and glucose.    

Muscular Disorder

Muscular disorders can be mild or serious. Common conditions include include spasms, cramps, convulsions, and sprains and strains. Inflammation in the joint is known as tendinitis. Conditions that require medical attention are fibromyalgia, muscular dystrophy, myasthenia gravis, and amyotrophic lateral sclerosis.  

Homeostasis

The muscular skeletal system plays an important part in the homeostasis. It's many functions enable the body to move, regenerate, store nutrients, protect the body, maintain body temperature, and aid in the movement of fluid. 

References:

http://www.mnsu.edu/emuseum/biology/humananatomy/skeletal/skeletalsystem.html

http://en.wikipedia.org/wiki/Muscle

Movable Limb Lab

materials used for lab

The working model I chose for this lab is the upper forearm limb. The forearm limb shown includes the humerus, radius, ulna, and bicep muscle. The bicep muscle works with the humerus bone and radius bone. When the muscle contracts it pulls on the radius and makes the elbow flex. The following photos will illustrate the steps involved in muscle contraction.

I used a 4x4 to represent the humerus and two 2x2's to represent the radius and ulna. The red scarf represents the bicep muscle. Wire was used for the dendrites, axons, sarcomere and actin filaments. The pink string are myosin filaments and head. The brown milk duds are neurotransmitters, the white tic tac's are sodium, and the brown speckled snow caps are potassium.

The sacromere is made much larger to show the myosin and actin filaments. 

This is the overview

Neuron with schwann cells

Movement of charged sodium and potassium ions across membrane

Propagation of action potential along axon

Sarcolemma and T-tubule membrane tubes going into muscle to carry action potential throughout cell

Sacromere or single actin-myosin unit

Release of calcium from sacrcoplasmic reticulm.

Conclusion

The model shows the action potential of a motor neuron conducting an impulse through the axon arriving at the axon terminal, causing the release of neurotransmitters (acetycholine) to cross the synaptic cleft and diffuse through the muscle membrane. The action potential is then carried through the T-tubule membrane and through the sarcoplasmic reticulum releasing calcium that creates muscle contraction within the sarcomere. This is where the actual contraction takes place. The released calcium combines with the troponin opening a site for the myosin to bind with actin. The strand of actin is pulled toward the center like a rubber band contracting. This is done by a walking action from the head of the myosin strand forming cross bridges.

The result of putting together the parts surely helped to answer so questions and filled in parts of the puzzle. Part of the challenge was finding a scale where everything might fit together. I enjoyed the project and have  a better understanding of how these processes come together. 

Ethical Essay

Exercise for the Fun of It

Exercise is important to physical and mental health. Moderate exercise enables the body to function better on many levels. It improves functions like, increased blood supply to the muscles,  decreased body fat and cholesterol, increased bone density, and many other health benefits. The long term benefits are reduced health risks later on in life.

I do feel the the environment plays a big part in the community activities that take place. I think our culture is moving toward a more sedentary lifestyle whether at work or at play. I'm hoping not to point the finger, but I think one of the factors is our use of the computer. With computer games and entertainment  we can satisfy our senses without more than a click of the finger. Oftentimes parents are very busy and to keep their kids occupied they play videos for them. I sometimes see this as a daily routine and as the child gets older they are fixed on the television as their source of entertainment. 

I believe that physical activity is an integral part of life. Our bodies require it to stay healthy. The renewed intake of oxygen is important to so many basic functions. 

There is a difference that environment plays in either promoting or curbing physical activity. I think that community structures and accessibility play a role in inviting outdoor activity. I also think that daily activities learned in school influence habits later on in life. Physical activity is natural for children and if  they learn early to have fun, they will find their own means to engage in meaningful activity later on and hopefully throughout life. 

Nevertheless, it helps to live in an environment that promotes a healthy lifestyle such as parks, biking trails, and gyms and programs that are readily available to the community.  In areas where there are parks people tend to gather  to socialize and take leisurely walks.  This type of environment encourages people of all ages to step outside and to enjoy the outdoors. When I lived near a park there were regulars who would show up to do their walk or exercise. The community seemed livelier.  It was great to see a group in their seventies and eighties doing their morning stretch and exercise and daily walk.  Just being around them gave me an optimistic feeling. I was hoping I'd have the same health at their age.

The guidelines presented by the Scottish government provide a helpful and hopeful means of promoting healthy lifestyles. If diabetes , heart disease, and obesity are on the rise, then perhaps our lifestyle changes in food, activity do play a part in the prevention of these diseases. I would think that  the sedentary lifestyle that leads to greater risk of heart and other diseases would not be a healthy scenario to follow. In part the benefits of exercise is to reduce stress. It improves our mental and physical functioning. So exercise has the potential to reduce stress in our lives and improve our immune system.

The essay on obesity and the environment stressed that if there is sufficient pressure to adopt new behaviors individuals are apt to change for the sense of belonging. The article used recycling as a example that created a trend in educating  children about it's importance. I think by setting healthy examples at a young age it helps to instill habits and behaviors that will be beneficial for a lifetime. The difficulty will be in implementing a course that will create significant change due to our current perceptions. I also agree with the article that our current culture can make it difficult to promote these changes. We are very convenience oriented. Thus there has to be a incentive for change.  Unfortunately illness has become the primary motivator. Such that it has become a national epidemic. Another challenge is many people also lack the time in their lives to add additional activities to their already busy lives. So I feel that changes in the environment might lend more enthusiasm for physical activity and changes in eating habits. If it is implemented on a community level it invites others to participate. It appears that lifestyles have changed greatly in the past fifty years or so it might take incremental steps to see what results will transpire.    

The Fun In Seven program started in Hong Kong sounds like a great program because it's emphasis is to provide knowledge and skills and awareness of health issues in a fun way that can be applied in life. 

I wonder if adopting similar programs in the US will have such an impact.

References:

http://www.ehponline.org/docs/2005/7812/7812.html

http://octopus.bch.cuhk.edu.hk/fun7/english/about_us.shtml

Topic II Lab

Movement Lab

Introduction

The purpose of this lab experiment is to determine if cold and fatigue can adversely affect muscle strength. First by observing how muscle works. Then determining what effects take place.

Hypothesis

Cold and fatigue will reduce the number of repetitions that can be completed.

 

Procedure

The first test will test muscle action and how it effects the size of the muscle. We will measure the circumference of the bicep at rest and the bicep when it is clenched. 

In the next experiment we will perform the task of making as many clenched fists as possible in twenty seconds. This is done twice. Once in regular temperature and the other after the hand is submerged in ice for at least a minute.  

In our final experiment fatigue to the muscle will be induced by repetitive action of the biceps, the large muscle of the upper arm. We will do this by squeezing a rubber ball. The idea is to get as many squeezes as possible within twenty seconds. By recording ten sets we'll have a comparison of numbers.

Conclusion

A contracted bicep is larger in circumference to a relaxed bicep. 

In the second experiment the task was accomplished with 62 repetitions. However, after placing the hand in ice water the same activity of squeezing a ball produced only half of the the amount of repetitions, 31. The cold dramatically affected the functioning of the muscles.

The third experiment produced an unusual result. The amount of repetitions actually increased within the ten sets performed. The assumption is that the muscles are warming up and are able to do more. By the third round of ten sets is where change started to occur or muscle fatigue started to set in. The numbers below reflect the the round of ten sets. 

What are the three changes you observed in a muscle while it is working (contracted)?

As the muscle is working contracted it gets tighter and tighter and the muscles shorten.

Also it seems that it effects the range of motion in the fingers and it relaxes less. 

The muscles in the fingers and palm get thicker.

What effect did the cold temperature have on the action of your hand muscles? 

Wow. The cold temperature greatly affected the number of repetition that could be completed. Due to the numbing of the hand the muscles were slow to respond and coordination was more difficult. It was near to impossible to get the muscles to relax.  In repeating the repetition of squeezing the ball, the muscles did not contract and relax fully. It seems like the constriction from the cold limited blood circulation to the muscles. muscles work more effectively when there is sufficient heat and circulation.

What effect did fatigue have on the action of the hand muscles?

The effect of fatigue reduced the number of repetition that could be completed. As the movements became more difficult to complete it became harder to contract the muscles and easier the to relax the muscles although the muscles felt contracted.  

Circumference of Bicep

 

At Rest            11 inches

Clenched       12 inches

Temperature     Number of Fists

Normal                       62

Ice Water                   31

Trial     # of squeezes in 20 sec.                  9 more x's

1                      55                                                     64

2                      55                                                     64

3                      56                                                     65

4                      54                                                     63

5                      52                                                     61

6                      52                                                     61

7                      52                                                     61

8                      50                                                     59

9                      47                                                     56

10                    47                                                    56

http://www.troy.k12.ny.us/thsbiology/labs_online/home_labs/muscle_lab_home.html

Sensory Receptors in Skin

Human Biology, Sylvia Mader

Saltatory Conduction

Human Biology, Sylvia Mader

 

Reflex Arc

Human Biology, Sylvia Mader

Compendium Topic One

Nervous System & Sensory Receptors

I. Nervous System

    

    Central Nervous System

    

    Limbic System and Higher Mental Functions

    Peripheral Nervous System

    Drug Abuse

II.  Sense and Sensation 

     Sensory Receptors and Sensations

     Proprioceptors and Cutaneous Receptors

        

     Senses of Taste and Smell

     Sense of Vision

     Sense of Hearing

     Sense of Equilibrium

    

I. THE NERVOUS SYSTEM

The nervous system recieves sensory input by stimuli, processes it through the brain and spinal cord, producing an output of muscle movement or glandular secretion. There are two systems, the central nervous system (CNS) and the peripheral nervous system (PNS). The brain and spinal cord make up the central nervous system and the nerves outside the central nervous system make up the peripheral nervous system. 

Nervous tissue consists of two types of cells. Neurons carry "messages" through an electrochemical process known as action potential. And neuroglia support and nourish the neurons. Neurons come in different shapes and sizes. There are three types of neurons, that perform different functions. Sensory neurons receive external stimuli by the sensory receptors which relay impulses going to the CNS. Within the CNS an interneuron integrates all nerve impulses. The third type motor neurons carry impulses from the CNS to an effector, muscle or gland that actualizes the response. 

Neurons have a cell body consisting of a nucleus containing genes, cytoplasm, mitochondria and other organelles. A neuron differs from other cells because they have extensions called dendrites and axons. Dendrites bring information from sensory receptors and the axoms conducts nerve impulses away from the cell body.

The myelin sheath is a covering protecting the axom made of Schwann cells a kind of neuroglia.The spaces in sheathing is called nodes of Ranvier. The sheathing is found along long axoms and not on short axoms. The myelin serves as an protector and insulator since it has poor conductivity. Nerve areas that are not covered appear gray and areas that are covered with the sheathing appear white.

Loss of the myelin sheathing can result in the disease of multiple sclerosis an immune system impairment and luekodystrophies caused by a genetic defect.

Nerve impulses carry information within the nervous system by way of an electrochemical process. This is how neurons communicate with each other. The impulse can be measured  by a voltmeter and the reading is called potential. There is a resting potential and a action potential. As it's name suggests, resting potential is when there is no impulse and the inside is more negative than the outside. The concentration of sodium ions is greater on the outside of the axon, and the concentration of potassium is greater on the inside. This unequal distribution of ions is maintained by the sodium-potassium pump. The pump works to transport sodium out and potassium into the axon. The polarity is also helped by negatively charged organic ions in the axoplasm. The rapid transmission of info is known as action potential. As this occurs there is a quick change in polarity. During an action potential depolarization is followed by repolarization. There are two types of gated channel proteins that allow an action potential to occur. First the sodium gates open to allow sodium to enter the axon. it depolarizes since the charge on the inside changes from negative to positive. Next the potassium gates open allowing Potassium to leave the axon. As the inside resumes it's negative charge it repolarizes. Nerve impulse can jump from one node to another it is known as saltatory conduction. This happens very quickly and with thick myelinated axons the rate is more than 100m/sec. Because an action potential generates another it is self propagating.

The amount of impulses generated within a fixed time determines it's intensity. A refractory period assures that the impulse passes along its intended path and does not move backwards. 

The ends of the axon branch into endings called axon terminals. It is in close distance to a dendrite or cell body. The distance between the two is called a synapse and the gap is called a synaptic cleft. The signal cannot make it across, so neurotransmitters are needed to carry the message across. These molecules diffuse across through the receiving membrane and bind with receptor proteins. Different neurotransmitters produce different responses. The life of neurotransmitters at a synapse is short. This lets cells respond to new signals. 

Some neurotransmitters are acetycholine, norepinephrine, dopamine, serotonin, glutamate, and GABA.

Other molecules called neuromodulators block the release of neurotransmitters or modify it's response. Substance P and endorphins are neuromodulators. They are natural painkillers.

The result of incoming signals to produce potential change are summed up in the process called synaptic integration. If the excitatory impulses surpass the inhibitory impulses threshold, action potential can occur. And if the inhibitory outweigh the excitatory the synaptic integration might prohibit the axon from firing. 

Central Nervous System 

Enclosed in the skull and vertabrae are the brain and spinal cord, the main components of the CNS where information is received. This is also where motor control is initiated. specific functions are performed in different parts of the brain. The spinal cord woks like a communication channel, sending and receiving  info from the brain to the body. The brain and spinal cord is protected by a membrane called meninges with spacings of cerebrospinal fluid. Cerebrofluid is found in the center of the spinal cord and in the  four ventricles of the brain. Fluid normally drains into the cardiovascular system. If accumulation occurs it can cause pressure. 

Two types of nervous tissue are found in the CNS. Cell bodies that are nonmyelinated are known as gray matter and myelinated axons are known and white matter.

The spinal cord is a bundle of nerves that starts at the base of the brain and extends into the vertebral canal. It serves as the main pathway for information from the brain to the PNS. It is protected by the vertebral column. The nerves extend from the spinal cord and out beyond the vertebrae. The spinal cord has gray matter, white matter and a central canal. The central canal and the meninges contain cerebrospinal fluid. Sensory and motor neurons are also found here, and interneurons which communicate with the other two. There are sensory fibers in the dorsal root of the spinal nerve and the ventral root contains motor fibers. The two are joined as a mixed nerve as it leaves the vertebral canal. Spinal nerves are part of the peripheral nervous system.

Within the white matter of the spinal cord information travels to and from the brain. The left side of the brain controls the right side of the body and vise versa. 

Different parts of the brain perform specific functions. The largest area known as the cerebrum integrates info which then produces motor responses. The cerebrum is divided by the corpus callosum into halves called the right and left  cerebral hemispheres. Grooves known as sulci make distinct the lobe areas such as the frontal, parietal, occipital and temporal. Thus there are four lobes per hemisphere. These are the areas where movement, reasoning, somatic, sensing, hearing, and vision take place. The cerebral cortex is the outer layer of the cerebrum. Wernicke's area and Broca's area are two centers  important to our ability to speak and are located in the left cerebral cortex. The diencephalon area in the third ventricle contains the hypothalamus and thalamus. The hypothalamus is important to several functions such as homeostasis and controls the pituitary gland. The thalmus is important to functions such as memory and emotions thus it receives visual, auditory, and somasensory information. The cerebellum is important to posture and balance. It integrates and sends impulses to the muscles. The brain stem contains axon bundles known as pon which link the cerebellum to the central nervous system. Within the brain stem the midbrain works as a relay, the medulla oblongata above the spinal cord is a reflex center performing many functions such as the regulation of heartbeat, breathing, and blood pressure. Along the brain stem is a mass of fibers and nuclei called reticular formation which receives and sends sensory signals.

Limbic System and Higher Mental Functions

This system is involved in the process and functioning of emotions, memory, and learning resulting in our behaviors. There are two main structures. Through the amygdala we experience emotions. And the hippocampus is an area important to learning and memory. Learning and speech require memory thus the three functions are interrelated.

Peripheral Nervous System

This system consists of cranial nerves and spinal nerves and carries impulses to and from the central nervous system. Cranial nerves project from the brain and spinal nerves from the spinal cord. Nerves are made up of axons. Cranial nerves come in twelve pairs consisting of sensory, motor, or mixed fibers and are attached to the brain. Spinal nerves come in thirty one pairs containing both sensory and motor fibers.

The peripheral nervous system is comprised of the somatic and autonomic system. The somatic carries impulses to the central nervous system and away form the central nervous system to the skeletal muscles, skin and tendons. Involuntary actions that are produced are called reflexes. A reflex arc describes the path of the spinal reflex. The autonomic system is connected to the activity of the cardiac and smooth muscle glands. Within this system there are two complimentary involuntary pathways called the sympathetic and parasympathetic. The sympathetic produces responses associated with an alert state and the parasympathetic produces responses associated with a relaxed state. Norepinepherine and adrenaline are produced in a sympathetic response and acetycholine is producced in a parasympathetic response.  

Drug Abuse

Neurological drugs block or activate the action of neurotransmitteres at a synapse, and can alter the nervous system. Drug abuse can lead to psychological or physical dependency on the drug. once it becomes a dependency it can lead to addiction. The most common forms of drug abuse is alcohol, nicotine, cocaine, methamphetamine, heroine, and marijuana.   

II.  SENSE 

The human body consists of a variety of sensory receptors that are able to detect different stimuli. These impulses are carried to the central nervous system.

Sensory Receptors and Sensations

Sensory receptors carry impulses to the spinal cord and brain. There are four kinds of sensory receptors. They are called chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors. Chemoreceptors respond to chemical substances as pain receptors are a type of chemoreceptor. Photoreceptors respond to light, mechanoreceptors respond to forces such as pressure, and thermoreceptors such as in the skin are sensitive to temperature. When impulses reach the cerebral cortex it registers a sensation. Our interpretation of the sensation creates our perception.

Proprioceptors and Cutaneous Receptors

Proprioceptors are helpful to equilibrium and posture. They are mechanoreceptors important to reflex and muscle tone. Muscle tone is controlled by the action of the muscle spindle which increases contraction and the golgi tendon organ which deceases contraction. Cutaneous receptors are another type found in the dermis layer of the skin. They enable us to feel touch, pressure, pain, and temperature. The skin also contain pain receptors known as nociceptors that are sensitive to chemicals from the release of damaged tissues. 

Senses of Taste and Smell

The act of tasting and smelling is made possible by chemoreceptors. They are able to respond to direct and distant stimuli. The receptors are able to bind to molecules. Different areas of the tongue sense various tastes and flavors. our sense of smell is produced by the olfactory cells in the nasal cavity. olfactory cells are neuronsthat transmit this info to the cerebral cortex.

Sense of Vision

The eye, optic nerves and areas of the cerebral cortex are all involved in the visual process. The eyeball has three layers. The sclera, choroid, and retina. The retina is where the sensory receptors cones and rods are located. The lens and the cornea work to focus light on the retina. The image is then carried by the optic nerves to the thalmus and on to the occipital lobe of the brain. Common disorders of the eye are nearsightedness, farsightedness, and astigmatism. These conditions involve the changing shape of the eyeball. Color blindness is normally hereditary and affects the cones ability to perceive light and colors. Other problems that can develop with age are cataracts, clouding of the lens, and glaucoma, fluid pressure in the eyes.

Sense of Hearing

Sensory receptors for the hearing are mechanoreceptors located in the inner ear. The are important to hearing and balance and involve the ear, cochlear nerve, and the cerebral cortex. There are three parts to the ear, The outer, middle, and inner. The structure serves to amplify and direct sound waves to the inner ear. It is within the inner ear where we find the mechanoreceptors which are hair cells. Nerve impulses travel from the receptor to the cochlear nerve on to the cerebral cortex.      

Sense of Equilibrium

The ear is also the responsible for maintaining equilibrium. Within the inner ear mechanoreceptors in the semicircular canals help to sense the heads rotational equilibrium and gravitational equiliibrium. also within the inner ear the utricle is sensitive to horizontal and vertical movements.  

References:

http://www.sciencedaily.com/articles/s/sensory_neuron.htm

http://en.wikipedia.org/wiki/Spinal_cord

http://faculty.washington.edu/chudler/cells.html

Nervous Function Lab

Nervous Function Lab

1.  What is the electrode measuring?

The electrode is measuring the activity within the neuron. The resting/action potential of the neuron.

2.  Why use leeches in neurophysiology experiments?

Leeches are used in these experiments because the neurons in their nerve cord are large and easy to get to.

3.  What is the difference between a sensory and motor neuron?

A sensory neuron transmits nerve impulses to the central nervous system and a motor neuron carries nerve impulses away from the central nervous system to the muscles or glands.

4.  How do you think a leech experiences pain? What is pain?

Pain is experienced  by the signals sent by a specific kind of sensory neurons called pain receptors. I would think that leeches feel pain because they have a nervous system and sensory receptors.

5.  What are the two most interesting things about doing this lab? 

I found that actually seeing how the electrode measurement worked gave me a better idea of what is involved in measuring potential. The next was clicking through the different cell types to see what they looked like under the microscope.

6.  Anything you found confusing or did not like about the lab? 

I didn't find it confusing. I was actually glad that this lab was done in a virtual setting.