Compendium Review Unit 3/ Topic 2- Movement

Compendium Review- Unit 3- Environmental Interactions- Topic 2-Movement

Chapter 11- Skeletal System

11.1- Overview of Skeletal System
11.2- Bone Growth, Remodeling, and Repair
11.3- Bones of the Axial Skeleton
11.4- Bones of the Appendicular Skeleton
11.5- Articulations

11.1- Overview of Skeletal System
There are 206 bones in the adult body. The skeleton is what supports the body, produces blood cells, protects soft body parts, stores minerals and fat, and permits flexible body movement. The main part of the bone is the diaphysis which has a medullary cavity that’s walls are composed of compact bone. The cavity is filled with yellow bone marrow that stores fat. The part of the bone that’s at the end of a long bone is the epiphyses which is made of spongy bone that has red bone marrow, where blood cells are made. Articular cartilage occurs at a joint. Periosteum is the connective tissue that covers the long bone, besides at the ends. Osteons are the tubular units that make up compact bone. Osteocytes are the bone cells that pass on nutrients and collect wastes from other cells. Spongy bone has thin plates separated by unequal space, this bone is better for strength. Red bone marrow is what fills the spaces in spongy bone. Cartilage is gel like, has no nerves and makes good padding for joints. Cartilage doesn’t heal fast because it has no blood vessels. There are three types- Hyaline cartilage- firm and flexible, Fibrocartilage- stronger, withholds tension and pressure and elastic cartilage- more flexible than hyaline cartilage. Fibrous connective tissue makes up ligaments and tendons.
Anatomy of a long bone shown below:








11.2- Bone Growth, Remodeling, and Repair
Some bones grow in length and width through adolescence but some continue until the age of 25, at six weeks the embryo skeleton starts to form. Some cells that help in bone growth, remodeling and repair are osteoblasts, osteocytes, and osteoclasts. Osteoclasts remove matrix from the bone and osteoblasts build it up, these turn in to osteocytes when surrounded by calcified matix. Formation of the bone is known as ossification. Intramembranous ossification are bones that develop between sheets of fibrous connective tissue. Endochondral ossification is what most of the bones of the skeleton are formed by. The growth plate or the epiphyseal plate is a band of cartilage. Four layers make up the plate, layer closest to the plate is the resting zone where cartilage remains. Next is the proliferating zone where chondrocytes produce new cartilage cells. Third layer is the degenerating zone where the cartilage cells die and the final layer is the ossification zone where bone is forming (this is what makes the bone length increase.) Hormones are chemical messengers that act on different parts of the body that have an affect on bone growth. Growth hormone (GH) is what stimulates bones growth, too little can lead to being a dwarf and too much can lead to being a giant.
Bone remodeling is the process of bone renewal, 18% of bone is recycled each year. This process keeps bones strong and the recycling helps the body to regulate the amount of calcium in the blood. The parathyroid hormone and calcitonin hormone help to regulate this level. Parathyroid speeds up bone recycling and calcitonin acts opposite of that.
After a bone suffers a break or fracture a repair is needed. There are four steps for a fracture repair that takes place during a few months 1- hematoma which is a mass where blood escapes from a ruptured blood vessel after a fracture, 2- fibrocartilaginous callus which is where tissue repair begins, 3- bony callus which joins the broken bones together and 4- remodeling spongy bone is absorbed and compact bone is built.
Bone fracture and repair shown below
















11.3- Bones of the Axial Skeleton
The axial skeleton is in the midline of the body consisting of the skull, hyoid bone, vertebral column and the rib cage. The braincase and facial bones form the skull. Eight bones make up the cranium or braincase. Major bones of the cranium are the frontal bone- forms the forehead, parietal bones- extend to the sides, occipital bone- curves to form the base of the skull and the foramen magnum- where the spinal cord passes and becomes the brain stem. The temporal bone leads to the middle ear. Sphenoid bone is the keystone of cranial bones- all other bones articulate with it. This bon makes the eye sockets and sides of the skull. Lower jaw bone is the mandible an is the only moveable bone of the skull. Tooth sockets are located here and on the maxillae- the bones that form the upper jaw. Zygomatic bones are the cheekbone prominences and the nasal bones make the bridge of the nose. The only bone in the body that does not articulate with another bone is known as the hyoid bone, which is part of the axial skeleton but not the skull.
33 vertebrae make up the vertebral column. Four curves of the column provide strength and resilience. When vertebrae join the column is formed. Spinal nerves control skeletal muscle contractions. Cervical vertebrae are in the neck, first one is the atlas which holds up the neck. Second one is the axis which allows the rotation of the neck. Intervertebral disks are in between the vertebrae and act as padding. The disks help us bend either way and move side to side.
Thoracic vertebrae make up the rib cage which is part of the axial skeleton. The rib cage protects the heart and lungs. Flattened bones make up the ribs, there are twelve pairs connected to the thoracic vertebrae in the back. The top seven pairs connect to the sternum by way costal cartilage, known as true ribs. Next three pairs are false ribs, they connect to the sternum by way of common cartilage. Last two pairs are floating ribs because they don’t attach to the sternum, they attach to the vertebrae T12. Midline of the body is the sternum, which also helps protect the lungs and the heart. Three bones make up the sternum the manubrium, the body, and the xiphoid process. Manubrium occurs at the level of the second rib which allows the ribs to be counted. Apex of the heart is located between the fifth and sixth ribs.

11.4- Bones of the Appendicular Skeleton
Bones of the pectoral and pelvic girdles and the attached limbs make up the appendicular skeleton. Pectoral girdles are on both side of the body and are made up of a scapula and a clavicle. Clavicle goes across the top of the thorax, scapula is a visible bone in he back. Rotator cuff is made of tendons extending to the humerus from four small muscles. Eight carpal bones make up the wrist, five metacarpal bones form the palm. Phalanges are the finger and thumb bones.
Hip bones make up the pelvic girdle. The pelvis bears the weight of the body, protects organs with the pelvic cavity and is what attaches the legs. Three parts make up the coxal bone, the ilium, ischium, and the pubis. Hip socket occurs where these three meet. Ilium is the largest part. Ischium is what we sit on. Pubic bone is the anterior part of the coxal bone. Thighbone is known as the femur and is the longest and strongest bone in the body. Tibia is the region of the knee and kneecap. Quadriceps tendon is what holds the kneecap in place. Slender bone in the leg is the fibula, forms at the outer bulge of the ankle. Seven tarsal bones make up the ankle, one of these the talus, can move freely where it joins the tibula and fibula. Heel bone is known as the calcaneus is considered part of the ankle. This and the talus support the weight of our bodies.

11.5- Articulations

Bones joined at the joints are classified as fibrous cartilaginous. Fibrous joints like the sutures in between the cranial bones are immoveable. Hyaline cartilage is what connects the cartilaginous joints. These joints are slightly moveable. Synovial fluid fills the synovial joint which is freely moveable. This fluid is a lubricant for the joint.
Synovial joints shown below:






Ball and socket joints at the hips and the shoulders allow movement in all planes. Elbow and knee joints are synovial joint known as hinge joints, they allow movement only one way. Tendons are what attach intact skeletal muscles to bones.

Chapter 12- Muscular System

12.1- Overview of Muscular System
12.2- Skeletal Muscle Fiber Contraction
12.3- Whole Muscle Contraction
12.4- Muscular Disorders
12.5- Homeostasis

12.1- Overview of Muscular System
There are three types of muscle tissue first there is smooth muscle which has muscle fibers that are spindle shaped cells and is located in the walls of the hollow internal organs. Contraction of this muscle in involuntary. Second type is cardiac muscle which forms the heart walls. This muscle contracting is involuntary as well. Last there is the skeletal muscle which can be long. This type of muscle is voluntary. This muscle supports the body, helps keep a regular body temperature, is responsible for making the body move, and this muscle keeps blood moving through the cardiovascular veins and lymph moving through lymphatic vessels. Skeletal muscles also assist in keeping internal organs safe and joints stabilized.
Fascicles are skeletal muscle fibers that make up a whole muscle. Connective tissue surrounds the fascicles inside and out. Tendons are the fascia, a connective tissue that covers muscles that extend beyond the muscles. Tendons anchor muscles to bones. Muscles contract-pulling on the tendon-bone moves. Muscles work in pairs but the one that does most of the work in known as the prime mover. Synergists are the muscles that help the prime mover. Muscles pull not push, they become shorter when contracted. Antagonist are the muscles that work opposite the prime mover.

12.2- Skeletal Muscle Fiber Contraction
The plasma membrane for muscle fibers is known as sarcolemma, cytoplasm known as sarcoplasmic reticulum. Myofibrils are in the reticulum and are the contractile portions of a muscle. Sarcomeres are the units responsible for muscle contraction. Two protein myofilaments myosin and actin make up sarcomeres. Myosin is thick filament while actin is thin filament. When a muscle contraction occurs sarcomeres shorten allowing actin filaments to slide past myosin filaments. Energy for muscle contraction is supplied by ATP. Myosin does the work, it breaks down ATP. Motor neurons are what stimulate contraction in muscle fiber. ACh fills synaptic vesicles in axon terminals. ACh is release when nerve impulses moving down a motor neuron arrive at the axon terminal. Once it is released it diffuses across the cleft and binds to receptors in the sarcolemma. Calcium being released from the reticulum leads to sarcomere contraction. Tropomyosin is a protein that winds about an actin filament while troponin, another protein occurs along the threads. Myosin can bind to actin when calcium is released and combines with troponin.

12.3- Whole Muscle Contraction
Motor units are made up of nerve fiber and muscle fiber. The all or none law is what motor units go by, once a motor unit is stimulated they either all contract or not. Muscle twitches are a response to infrequent electrical impulses. Three stages make up a twitch, first the latent period which is the time between stimulation and initiation of the contraction, next the contraction period, shortening of the muscle and last the relaxation period which is the muscle going back to the previous length. Tetanus is maximal sustained contraction and continues until the muscle fatigues. Sustained contractions occur when some motor units contract maximally while others are resting to keep all muscles from fatiguing at once. Four types of energy sources for muscles are muscle triglycerides, plasma fatty acids, blood glucose and muscle glycogen. Glycogen and triglycerides are stored in muscle the other two come from blood. A limited amount of ATP is stored in muscle cells and if more is needed they can get it from formation of ATP by creatine phosphate pathway, formation of ATP by fermentation and/or formation of ATP cellular respiration.
Slow twitch fibers prefer cellular respiration while fast twitch prefer fermentation and creatine phosphate pathway for ATP. Fast twitch muscle fibers are anaerobic, fatigue easily and have huge power. Slow twitch is aerobic, has steady power and endurance. Delayed onset muscle soreness can occur 24-48 hours after hard exercise. This can be avoided with stretching before exercising and when starting something new to take it slow building up your strength and endurance avoiding straining yourself.

12.4- Muscular Disorders
Sudden and involuntary muscle contractions that can sometimes be painful are known as spasms. If this occurs in the intestinal tract a bellyache can occur. If these come in multiples then seizures or convulsions can result. Long painful spasms are known as cramps. With a lot of effort a person can control facial tics. If a muscle is stretched or torn a strain can occur. If a joint is twisted a sprain can occur. If a tendon becomes injured or inflamed movement of a joint can be painful and tendonitis can result. Myalgia and fibromyalgia are two types of muscular diseases. Myalgia can result from overstretching or overworking muscles or can come from viral infections. The result is achy muscles. Fibromyalgia is chronic and causes achy pain, tenderness and stiffness of muscles. A progression of degenerating and weakening muscles is muscular dystrophy. Lou Gehrig’s disease has no cure and causes the inability to chew, talk, walk and swallow.

12.5- Homeostasis
Skeletal and muscular systems work together in maintain homeostasis, one assists the other with eating and moving, keeping the heart pumping, and breathing. While the skeletal system protects the soft organs the muscular system protects the abdominal organs. The skeletal system produces red bone marrow and regulates blood calcium while the muscular system helps regulate the body temperature, keeping it stable.

Unit 3- Ethical Issue Essay- Exercise

What Is It Going To Take?

In a world where obesity has become such an epidemic, what will it take for a change to take place? It is hard to see how anyone or group can be organizing exercise groups or physical activity pyramids and putting them to use. This sort of thing doesn't make the news or even the discovery channel, instead we see "World's Fattest Man" and "World's Fattest Man Gets Married." The way they have made this man some kind of celebrity is just sick to me!

I think it's great that Scotland promotes a more active lifestyle and that Island County has the physical activity pyramid, now if we could get people to go by this all over the world we might have a fighting chance. I believe that today people are so busy in their lives working and getting food on the table that come some down time, the thought of physical activity is exhausting let alone actually doing it. I work full time and I am taking three classes, so to squeeze exercise in there I thought I'd get up thirty minutes early every morning, I made it twice before giving up, so I get how finding the time can be hard. But at least eat right and put in a little physical activity throughout the day. You can do exercises while sitting at your desk.

So, if we could adopt the traits that it takes to stick to a physical activity pyramid or maybe bike to work or school and eat healthy we might be able to beat this epidemic, but as it sits right now I only see the problem getting worse. Maybe more people should use the MyPyramid Tracker, maybe that'll give them a wake up call.

Unit 3- Online Lab 2- Muscle Lab

Introduction: The purpose of this lab is to observe the muscles contracting before temperatures and fatigue and then to observe them once they are cold or fatigued to see the difference. Also this lab will help to recognize how the muscles are at resting and once contracted.

The supplies for this lab are:
bowl of water
ice or snow
timer or watch
paper
rubber ball or clothespin

This is a picture of my supplies:

This is a picture of my hand in the freeing cold water! You can't see it throbbing, but I felt it!!! :)

Temperature------ Number of Fists
Normal----------- 36

Ice Water--------- 22


Trial ----- # of Squeezes in 20 seconds

1------------ 40
2------------ 39
3------------ 36
4------------ 35

5------------ 32
6------------ 29
7------------ 30
8------------ 27

9------------ 26
10----------- 24



1. The three changes I noticed when my muscles were contracted were my muscle getting fatigued, it became shorter and stuck out a little bit more or bulged.

2. The cold water made my hand throb and caused my muscles to slow down, I was unable to clench my fist as many times as before putting my hand in the cold water.

3. The fatigue of my hand made it slower to clench my fist and to clench the ball.

Unit 3- Online Lab 1- Leech Neurons

1. The electrode is measuring resting potential and action potential of the neuron.

2. The leech is used for this because they are large and easy enough to get access to. They attach themselves to the host without the host realizing it.

3. A motor neuron conducts nerve impulses away from the central nervous system, while a sensory neuron transmits nerve impulses to the central nervous system.

4. I think the leech experiences pain even if its only a tiny bit. The leech has sensory receptors like us making it sensitive to chemicals that are released when the tissue is damaged.

5. It was interesting cutting the leech up and being able to probe around on the tissue before turning the UV light on.

6. The only confusing part about the lab was computer being junky for a minute :) But once that was fixed I actually enjoyed doing this online lab.

Unit 3- Lab Project- Build a Limb

For this lab project I had to build a human limb, bones that meet at a joint, a muscle pulling on that bone, muscle cell showing how actin-myosin filaments make it contract and neurons that go to muscle cells triggering contraction. For the limb I chose a human leg. The supplies for my project included clay to show the muscle, skeleton bones left over from halloween, pipe cleaners for the neurons and actin-myosin, crazy eyes to show sodium ions and potassium ions, construction paper for labeling, pieces of a straw to show schwann cells and grape stems.

This is a picture of the supplies I used:
This is my human limb, the leg. The red clay on it is showing the muscle.

This is the leg laying down so that I could label the parts:

This is my version of an axon with the schwann cells. The little red pieces are the straw and the grape stem is the axon terminal and the dendrites.

Here I am showing the propagation of action potential along the axon:

This is the muscle cell, the sarcomeres are relaxed here, they are shorten:

And here the sarcomeres are contracted:

This picture is of the sodium ions (Na+) gates opening and starting to move inside the axon. Na+ goes before K+.

This is what happens next, the Na+ gates close allowing potassium ions (K+) to move out of the axon.

So in conclusion my models show the human limb and the muscle on it, the action potential and actin-myosin filaments that are required to get a limb to move and the axon with the schwann cells. This project has helped me to understand how our limbs move and what makes muscles contract. Without action potentials and actin-myosin filaments how would are limbs move?

Compendium Review Unit 3/ Topic 1: Enviromental Interactions

Compendium Review Unit 3- The Body- Topic 1- Environmental Interactions

Chapter 13- Nervous System

13.1- Overview of the Nervous System
13.2- The Central Nervous System
13.3- The Limbic System and Higher Mental Functions
13.4- The Peripheral Nervous System
13.5- Drug Abuse

13.1 Overview of the Nervous System
The nervous system has 2 major divisions that are connected and work together they are the central nervous system (CNS) and the peripheral nervous system (PNS). PNS consists of nerves while CNS consists of the brain and spinal cord. The three specific functions of the nervous system are 1- the nervous system gets sensory input, 2- CNS adds up all the input it gets from the body and 3- generates motor output, nerve impulses go from CNS by way of the PNS to the muscles and glands.
Neurons are cells that transmit nerve impulses and neuroglia are what support and nourish neurons. Both are cells that make up nervous tissue. Sensory neurons, interneurons an motor neurons are the three types of neurons. The sensory neuron takes messages from a sensory receptor to the CNS. Special structures that detect changes in the environment are sensory receptors. Interneurons lie entirely within the CNS. They get input from both sensory neurons and other interneurons. They add up all the received info before communicating with motor neurons. Motor neurons take nerve impulses from the CNS to an effector or muscle fiber or gland. Effectors are what carry out responses to environment changes. Neurons are made up of three parts- cell boy, dendrites and an axon. Nucleus and other organelles make up the cell body. Short extensions that get signals from sensory receptors and neurons make up dendrites. The portion of the neuron which conducts nerve impulses is known as the axon.
Types of neurons are shown below:

Myelin sheath is what protects axons. For the PNS it is made b neuroglia known as schwann cells- contact myelin in plasma membranes. Oligodendrocytes in the CNS do this. When cells wrap around axons the myelin sheath is made. Nodes of ranvier are the gaps where no myelin sheath is. Short axons do not have myelin sheath. White matter in CNS has myelinated axons, gray area does not. Loss of myelin sheath can result in MS or leukodystrophies.
Resting potential occurs when the axon is not conducting an impulse. -65 mV inside the neuron is more negative than outside.
Sodium-potassium pump transports sodium ions (Na+) out of potassium ions (K+) into the axon. This is what maintains unequal distribution of both across the membrane. Always more positive ions outside the membrane. Rapid change in polarity is action potential- this happens if the axonal membrane depolarizes to threshold. Gates will open letting K+ and Na+ pass through the membrane. Sodium gates open first- Na+ goes to the axon causing potential changes -65mV to +40mV which is depolarization- the inside of the neuron goes negative to positive. Potassium gates open next and K+ goes to the axon and repolarization occurs +40 mV back to -65mV. Nerve impulses going from nerve to nerve is called salutatory conduction. The refractory period keeps the sodium gates closed keeping action potential from going backwards.
Axon terminals are small swellings at the end of axon branches. The synapse is the region of the close proximity, small gaps that separate sending neurons from receiving neurons are the synaptic cleft. Neurotransmitters are what helps get nerve impulses over the cleft. Once neurotransmitters initiate responses they leave the cleft. Acetylcholinesterase is an enzyme that inactivates neurotransmitters.
Synapse structure & function shown below:


Serotonin is a neurotransmitter that is involved with sleeping, emotions and perception, norepinephrine is too but it is involved with waking, dreaming and mood. Lower levels of these are linked with depression. Neuromodulators are molecules that block the release of neurotransmitters. Substance P is released when in pain, endorphins block the release of this. Both are neuromodulators.

13.2- The Central Nervous System
The spinal cord and the brain which make up the CNS are protected by bone; the vertebrae protects the spine the skull protects the brain. Protective membranes that wrap and protect both of these are known as meninges. Cerebrospinal fluid fills the spaces between the meninges and it cushions and protects the central nervous system. Interconnecting chambers that produce and serve as a reservoir for the fluid are known as ventricles. The brain has four of these. Water on the brain is a condition called hydrocephalus. Gray matter is one type of nervous tissue that contains cell bodies and short nonmyelineated fibers. The other type is known as white matter which contains mylineated axons that run together in bundled called tracts.
The meninges and central canal contain cerebrospinal fluid that protects the spinal cord. Spinal nerves are part of the peripheral nervous system. The right side of the brain controls the left side of the body, left side of the brain controls the right side of the body. Communication between the brain and peripheral nerves leaving the cord is provided with the spinal cord. Endorphins can stop pain otherwise the pain messages will pass through the gates to the brain. Paralysis occurs if the spinal cord is severed, meaning no voluntary muscle control. If the cord is severed in the thoracic area then the lower body is affected- the legs are paralyzed, which makes the person a paraplegic. Quadriplegic is when the injury happens in the neck area making all four limps paralyzed. Thousands of reflexes happen in the spinal cord.
The largest part of the brain is the cerebrum, which is the last part to receive sensory input and carry out integration before commanding voluntary motor responses. The cerebrum consists of two halves, the right cerebral hemisphere and the left hemisphere. It is split in half by a deep groove known as the longitudinal fissure. The hemispheres are divided into lobes by shallow grooves known as sulci.
The lobes of the hemisphere are shown below:

The cerebral cortex is known as an outer layer of gray matter that covers the cerebral hemispheres. Over one billion cell bodies are in the cortex. This part of the brain is associated with sensation, voluntary movement and the thought processes. Motor and sensory areas are in the cerebral cortex. The frontal lobe has the primary motor area. Sensory info from the skin and skeletal muscle goes to the primary somatosensory area. Integration occurs in association areas. The premotor area organizes motor functions like walking and talking at the same time. The processing centers of the cortex receive info from association areas and perform higher level functions. Prefrontal area gets info and plans our actions, the ability to think critically and formulate appropriate behaviors is because of integration in this area. Wernicke’s area and Broca’s area are partly responsible for humans speaking, both areas are found in the left cerebral cortex. Wernicke’s helps us to understand written and spoken words sending the info to Broca’s. White matter makes up most of the rest of the cerebrum. A region that encircles the third ventricle is known as the diencephalon. This is where the hypothalamus and thalamus are located. The hypothalamus helps in maintaining homeostasis and also is a link between the nervous system and the endocrine system. The thalamus receives all sensory input except smell. The thalamus integrates the info and sends it to the right part of the cerebrum. Also the thalamus helps in higher mental functions like memory and emotions. The fourth ventricle is what separates the cerebellum from the brain stem. Sensory input from the eyes, ears, joints and muscles is received from the cerebellum once this information is integrated the cerebellum sends motor impulses to the skeletal muscles. The relay station for the tracts passing between the cerebrum and spinal cord is the midbrain. Pons contains bundles of axons traveling between the cerebellum and the central nervous system. Reflex centers that regulate heart beat and breathing are in the medulla oblongata. The reticular formation is the network of nuclei and fibers that extend the length of the brain stem. The reticular activating system gets sensory signals and sends them up to higher centers.

13.3- The Limbic System and Higher Mental Functions
The limbic system is responsible for why sexual behavior and eating seem pleasurable and why mental stress can cause high blood pressure. The amygdala which can cause experiences to have emotional overtones is part of the limbic system. Also the hippocampus is another part to the limbic system, which is crucial to learning and memory. The prefrontal area of our brains is responsible for short term memory, once something is memorized it is put into long term memory. Semantic memory is a mixture, like numbers, words, etc. Episodic memory is related to people or events. Skill memory is used in performing motor activities. Memories are stored in the hippocampus and are utilized in the prefrontal area. Language depends on semantic memory.

13.4- The Peripheral Nervous System
Nerves are designated as cranial nerves when they arise from the brain and spinal nerves when they arise from the spinal cord. Nerves are made up of axons. Twelve pairs of cranial nerves attached to the brain, some have only motor fibers, some only sensory fibers and others have both. The cell body of a sensory neuron is in a dorsal root ganglion. A collection of cell bodies outside the CNS is known as a ganglion. Spinal nerves consist of sensory and motor fibers and therefore are mixed nerves. The somatic system nerves serve the skin, skeletal muscles and tendons. Reflexes occur when automatic responses to a stimulus in the somatic system. Pain is not felt until the brain receives and interprets the information.

A reflex arc is shown below:

The autonomic system is what regulates the activity of cardiac and smooth muscles and glands. This system is in the PNS. Sympathetic and parasympathetic divisions make up the autonomic system. Both function automatically and involuntary, they innervate all internal organs, and they utilize two neurons and one ganglion for each impulse. Preganglionic fibers of the sympathetic division come from the middle of the spinal cord and terminate in ganglia that lie near the cord. This division is important in emergency situations. The parasympathetic division consists of cranial nerves and fibers that come from the bottom part of the spinal cord. All the internal responses we associate with a relaxed state is in this division, also known as the housekeeper division. Both the somatic system and autonomic system are in the peripheral nervous system.

13.5- Drug Abuse
Drugs which consist of natural molecules or synthetically derived affect the nervous system, they alter the mood and our emotional state. They increase or decrease the action of a particular neurotransmitter and affect the limbic system. Dopamine has a role in mood. Psychological dependence on a drug is obvious when a person craves a drug, spends time looking for the drug and uses it regularly. The person is shows physical dependence or is addicted when they need more and more to reach the same high and they show withdrawal symptoms when they stop taking the drug. The most socially excepted form of drug use is alcoholism. A long time use of alcohol can harm the liver and make it function less. If alcohol blood level gets to high coma or death can result. Alcohol acts as a depressant in the CNS. Brain size can decrease with chronic use of alcohol. Nicotine is a stimulant, when it reaches the CNS it binds to the neurons and dopamine is released. In the PNS skeletal muscle activity increases. Cocaine use leads to a rush of well being that can last five to thirty minutes. The use of this drug brings on lack of appetite, sleeplessness and an increased sex drive. Crack is the street name for cocaine and is the form of smoking it. Dopamine is made less to make up for the excess of synapses with continued use. Methamphetamine is known as speed, which is powder form or crystal meth or ice which is in crystal form. Heroin acts as a depressant in the nervous system. Heroin is delivered to the brain and converted to morphine. Heroin can be smoked, injected or snorted. When marijuana reaches the CNS mild euphoria can occur. Regular use of marijuana can lead o cravings. This can have an effect on memory, balance, motor coordination and orientation.


Chapter 14: Senses

14.1- Sensory Receptors and Sensations
14.2- Proprioceptors and Cutaneous Receptors
14.3- Senses of Taste and Smell
14.4- Sense of Vision
14.5- Sense of Hearing
14.6- Sense of Equilibrium

14.1- Sensory Receptors and Sensations
The dendrites specialized to detect certain types of stimuli are known as sensory receptors. Sensory receptors that detect stimuli from outside the body are known as exterocceptors. Interoceptors get stimuli from inside the body and are involved in homeostasis. Four types of sensory receptors are chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors. A response to chemical substances is chemoreceptors. Pain receptors are a type of chemoreceptors, they alert us to possible danger. Response to light energy is photoreceptors which are in our eyes. Mechanical forces stimulate our mechanoreceptors (located in our ear) usually with some kind of pressure. They also help to keep our balance. Thermoreceptors are located in the hypothalamus and the skin and respond in temperature changes. Warmth receptors respond when temperatures rise and cold receptors respond in lower temperatures.
Sensations occur when nerve impulses get to the cerebral cortex. All sensory receptors initiate nerve impulses but the sensation depends on what part of the brain receives the impulse. Integration is carried out before the sensory receptors initiate the nerve impulse. A decrease in response to a stimulus is known as sensory adaptation. Sensory receptors functioning helps maintain homeostasis.

14.2- Proprioceptors and Cutaneous Receptors
Three types of general sensory receptors are known as proprioceptors, cutaneous receptors and pain receptors. Maintaining muscle tone and the body’s equilibrium and posture is due to proprioceptors which are mechanoreceptors involved in reflex. Nerve impulses occur when the muscle relaxes and undue stretching of the muscle spindle occurs. The dermis, which is a layer of the skin, contains cutaneous receptors. This makes the skin sensitive to touch, pain, pressure and temperature. Pain receptors are in the skin and many internal organs. Referred pain is when stimulation of internal pain receptors is felt as pain from the skin as well as internal organs.

14.3- Senses of Taste and Smell
Chemical senses are taste and smell. Chemoreceptors are present in taste cells. Four primary types of taste are sweet, salty, sour and bitter. Taste cells end in microvilli, this helps distinguish the taste. Adults have about 3,000 taste buds. 80-90% of what we taste is due to smell. High in the roof of the nasal cavity is where 10 and 20 million olfactory cells are located, our sense of smell depends on these cells. Olfactory cells are connected with the limbic system, certain smells can take us back to a person or place.

14.4- Sense of Vision
There are three layers to the eyeball which is 2.5 cm in diameter. The layers are the sclera which is the outer layer made of white and fibrous except the cornea, the choroid which is the middle layer that absorbs light rays that have not yet been absorbed by photoreceptors and the retina which is what helps us to see black and white, color and acute vision. The iris is what the choroid becomes toward the front of the eyeball and is what regulates the pupil. The pupil is what allows light in. The shape of the lens for near and far vision is controlled by the ciliary body. The posterior compartment of the eye (behind the lens) is separated from the anterior compartment (in front of the lens) by the lens. Aqueous humor is a clear watery fluid that fills the anterior compartment, this fluid is made daily. Tiny ducts are how this fluid is released, if they become blocked then glaucoma can occur, this can lead to blindness. A clear gelatin material known as vitreous humor is located in the posterior compartment. The fovea centralis is located in the retina and is where cone cells are packed. The optic nerve is what takes nerve impulses to the visual cortex. The lens, humors and cornea help focus things on the retina. Visual accommodation involves the lens rounding up bringing the image to focus on the retina during close vision. Rod cells and cone cells are photoreceptors. Rhodopsin is a molecule made of protein opsin and retinal, a light absorbing molecule. Rods help with peripheral vision and perception of motion. Carrots, being high in vitamin A help our night vision. The three kinds of cones that help us with color vision are the B (blue), G (green) and R (red) pigments. The retina is made up of three layers of neurons. Layer closest to the choroid has rod cells and cone cells, middle layer is bipolar cells and the inner layer has ganglion cells.
Structure & function of the retina is shown below:

A blind spot occurs for the left eye left of center and for the right eye right of center. Blind spots occur because there are no rods or cones where the optic nerve exits making no vision possible. The blind spot only happens for one eye, not when using both eyes. Optic nerves carry nerve impulses from the eyes to the optic chiasma, which is X shapped, crossing over optic nerves.
Some abnormalities of the eye include color blindness and misshapen eyeballs, 5-8% of males are affected with color blindness. Also nearsighted which means you can see better close up than at a distance, and farsighted which means you can see better at a distance than close up. When light rays cannot be evenly focused on the retina it is known as astigmatism.

14.5- Sense of Hearing
Hearing and balance are the two sensory functions of the ear. Hair cells located in the inner ear are the sensory receptors, mechanoreceptors. Three divisions of the ear include the outer ear, pinna the external flap and auditory canal, the middle ear at the tympanic membrane or the eardrum and the inner ear which unlike the first two divisions contains fluid instead of air.
Anatomy of the human ear is shown below:

The semicircular canals and vestibule of the inner ear work for equilibrium and the cochlea works for hearing. The outer ear gets the sound, middle ear magnifies the sound and strikes the oval window causing a vibration making pressure pass to the fluid in the cochlea.

14.6- Sense of Equilibrium
Nerve impulses are taken to the brain stem and the cerebellum by way of the vestibular nerve. The vestibular nerve helps maintain equilibrium. Rotational equilibrium is detected by the mechanoreceptors in the semicircular canals when movement of the head occurs. Gravitational equilibrium is when the mechanoreceptors in the utricle and saccule detect movement of the head.
Mechanoreceptors for equilibrium are shown below:

Work Cited:

Mader, Sylvia S. Human Biology 1oth ed. McGraw Hill Companies, 2008.

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