Chapter 13: The Peripheral Nervous System and Reflex Activity

                The peripheral nervous system contains all the neural structures outside the brain and spinal cord. This includes the sensory receptors, peripheral nerves, associated ganglia, and motor endings. The peripheral nervous system provides links to and from the external environment.

                Sensory receptors are a big portion of the peripheral nervous system; they are special structures to respond to stimuli. The activation of sensory receptors results in the depolarization that triggers impulses to the CNS. The understanding of these stimuli, sensation and perception all occur in the brain. It is important to remember with sensory receptors is that is isn’t necessarily important where the information is coming from, but more so where the input goes in the brain is what is important. All the receptors can be classified by their type of stimulus.

a. Mechanoreceptors-  respond to touch, pressure, vibrations, stretch, and itch

b. Thermoreceptors- responds to change in temperature

c. Photoreceptors- responds to light energy, for example the retina

d. Chemoreceptors- responds to chemicals, for example, smells, taste, and also changes in blood chemistry

e. Nociceptors- sensitive to pain-causing stimuli

Not only can receptors be classified by stimulus type, but they can also be categorized by their location.

1.       Exteroceptors (outside the body)- these type of receptors respond to stimuli arising outside the body, these are usually found near the body’s surface. They are sensitive to touch, pressure, pain, and temperature, this classification includes the special sense organs.

2.       Interoceptors (within the body)- these receptors are found in internal viscera and blood vessels. These are sensitive to chemical changes, stretch, and temperature changes.

3.       Proprioceptors- these receptors respond to degree of stretch of the organs that they occupy. These are found in the skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles. It helps to think of these receptors as “advising” the brain of one’s movement. Because of these receptors, is why you know where your legs or arms are for example without even looking at them. But on the other hand, you make “know” where certain organs are in your body because you have studied diagrams but your brain can’t really distinguish exactly where they are.

Check back next week for a book review on "The Spirit Catches You and You Fall Down" by Anne Fadiman and also key points of chapter 14 in your anatomy book!

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Chapter 12: The Central Nervous System

                This week we’re discussing the central nervous system in more detail. The central nervous system is made up of the brain and spinal cord. A vocabulary word you may want to be familiar with is cephalization. This is the evolution of the brain and how the elaboration of the anterior portion of the central nervous system, it also increases in neurons in the head and the highest level of this is shown in the human brain.

                The brain is composed of wrinkled, pinkish gray matter. The adult brain structure is broken up into 3 surface structures, the forebrain, midbrain, and hindbrain. These structures are further broken down into smaller categories; this can get confusing to understand so I am going to try and break it down, also you can find a handy diagram on page 429 of the text book that gives you a good visual of the structures of the brain.

1.     1.  Prosencephalon (forebrain)

a.       Telencephalon- contains the cerebrum: cortex, white matter and basal nuclei (derived from the lateral ventricles)

b.      Diencephalon- contains the thalamus, hypothalamus, and epithalamus (derived from the third ventricle)

2.     2.  Mesencephalon (midbrain)

a.       Mesencephalon- contains the brain stem and the midbrain (derived from the cerebral aqueduct)

3.    3.   Rhombencephalon (hindbrain)

a.       Metencephalon- contains the brain stem and pons (derived from the fourth ventricle)

b.      Myelencephalon- contains the medulla oblongata (derived from the fourth ventricle)

The two cerebral hemispheres are the biggest structure of the brain and most likely what you think of when you think of the brain. The brain contains ridges which are referred to as the gyri. The cerebral hemispheres contain shallow grooves called sulci. Lastly, it contains contain deep grooves called fissures. The fissures divide the large regions of the brain. The sulci divide the hemispheres into five lobes; frontal, parietal, temporal, occipital, and insula.

The cerebral cortex is make of superficial gray matter and this portion of the brain accounts for 40% of the mass of the brain. The main function of the cortex is that is enables us to be aware of ourselves, sensations, to communicate, to remember, and also to initiates voluntary movements. There are three types of functional areas are: Motor areas (control voluntary movements), sensory areas (conscious awareness of sensation), and association area (integrates diverse information). You need to be able to identify these areas on the brain and on page 434 there is a diagram with these areas as well as other structures of the brain that you need to know.

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Chapter 11: The Nervous System

                The nervous system has a lot of information involved! It is the master controlling system of the body. Its major functions are monitoring stimuli, interpreting sensory input, and responding to stimuli.  It is broken down into the Central Nervous System which is the brain and spinal cord and the Peripheral Nervous System which is the nerves outside of the central nervous system.

The PNS has two functional divisions which include the sensory (afferent) division and motor (efferent) division. The afferent division is further divided sensory afferent fibers (carries impulses from the sensory receptors to CNS) and visceral afferent fibers which transmit impulses from visceral organs. The motor division transmits impulses from the CNS to effector organs and is also divided into two main parts, one, is the somatic nervous system which is the conscious control of the skeletal muscles and the automatic nervous system which regulates the activity of smooth and cardiac muscles as well as glands.

The nervous system is also broken up into two different cell divisions: neurons and neuroglia. Neurons are excitable cells that transmit electrical signals. Neuroglia, or glial cells, are the glue and support for neurons.  Other functions of the Neuroglia include: segregating and insulating neurons, guide young neurons to the proper connections, and promote health and growth. There are multiple types of glial cells that we are responsible for knowing.

1.       Astrocytes- these cells are the most abundant and versatile of all the glial cells and are highly branched.  These cells cling to neurons and their synaptic endings and covers capillaries. There major functions include: support and brace neurons, anchor neurons to their nutrient supplies, guide migration of young neurons, and control the chemical environment of the cell.

2.       Microglia- these cells are small, ovoid shapes with spiny processes. These types of cell act as phagocytes that monitor the health of neurons

3.       Ependymal- these cells range in shape from squamous to columnar. These function for lining the central cavities of the brain and spinal column

4.       Oligodendrocytes- these cells are branched cells that wrap CNS nerve fiber.

The nervous system has a ton of information and large vocabulary words. I wouldn’t waste time on making notecards for every single bolded word, I would check back at the end of the chapter to do the review quiz and go over the summary points!

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Chapter 10: More on the Muscle system!

This week we are discussing chapter 10 goes into greater detail about the muscles as an organ.  Muscles have four functional groups: prime movers, antagonist, synergists, and fixators.  The prime movers are also known as agonists and provide the major force for creating muscle contractions. The antagonist opposes a particular movement. The synergists add force to a movement and also reduce undesirable or unnecessary movement.  Lastly, the fixators are synergists that immobilize a bone or also the muscle’s origin. An example of these functions would be flexion of the arm. In this scenario, the bicep brachii would be the prime mover or agonist and the tricep brachii would be the antagonist.

Also, there are several types of arrangements that muscles can be in which make them function in different ways. First, parallel are fascicles that run parallel to the long axis of the muscle, a good example of this is the Sartorius which is one of the main muscles of the quadriceps.  Then we have the fusiform, which is spindle-shaped muscle, an example of this type of muscle would be the biceps brachii. The pennate arrangement are short fascicles that attach diagonally to the central tendon running through the length of that muscle, an example of this would be the rectus femoris, also found in the quadriceps.  Next, convergent are when the fascicles converge from a broad origin to a single tendon insertion; this looks like the pectoralis major muscles. Lastly, the circular arrangements are when the fascicles are arranged in rings, such is the muscle around your mouth called the orbicularis oris.

The majority of chapter 10 has a ton of diagrams of the muscles and their names. For the test, try and focus on not only where they are located, but also their function because there will be a little description in the exam question that might give away the muscle even if you don’t know exactly what the diagram is pointing to. Also, remember muscles and their agonist and antagonists. Another helpful study tip for this section is flex or extend the muscle being discussed so you can know the movement and an idea of where the location is on you actual body. These tips helped me for studying for the exam so I hope that it helps you! Check back next week for more study tips!

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Chapter 9: The Muscle System

Chapter 9 is all about the Muscle System. This chapter can be a lot of memorizing! It helps me to remember the skeletal system; a lot of the names of muscles have the name of the bone in it! Prefixes such as sacro, myo, and mys all mean flesh aka muscle! So, during your exam you can use process of elimination by finding words you are already familiar with!

 There are 3 types of muscle tissues: skeletal, smooth, and cardiac. My blog this week is going to focus on these 3 types and break down there different characteristics. But first let’s talk a little bit about their similarities. Skeletal and smooth muscle cells are elongated and called muscle fibers. Actin and myosin are two kinds of myofilaments that are used in muscle contractions. There are also similar terminologies used in all muscle types. Sarcolemma is the muscle plasma membrane and sarcoplasm is the cytoplasm of a muscle cell.

Skeletal Muscle Tissue- This type of muscle tissue has striations and its voluntary. It can contract extremely fast but it also tries easily. This type of tissue is responsible for overall body movement. It is very adaptable and can handle a wide range of forces. Each muscle is a distinct organ with muscle tissue, blood vessels, nerve fibers, and also connective tissue.

Cardiac Muscle Tissue- Is found only in the heart, what a surprise being called cardiac muscle! This type of tissue is also striated like skeletal muscle.  This type of muscle tissue is involuntary (you don’t have to consciously make your heart pump). There are 54 sinoatrial nodes rhythmicity control and acts of the pacemaker in the heart. The central nervous system controls the rate of the heart pump.

Smooth Muscle Tissue- This type of tissue is found in the walls of hallow organs: stomach, urinary bladder, respiratory passages. This muscle’s main function is to force food and other substances through the internal body channels. This type of tissue is striated and is also involuntary, much like cardiac muscle tissue.

There are four main functional characteristics of muscle tissue: excitability/irritability (ability to receive and respond to stimuli), contractility (ability to shorten forcibly), extensibility (the ability to be stretched or extended), and elasticity (ability to recoil and resume the original resting length).

The muscle system can be a lot of information! So I suggest reviewing the muscles a little each day so when it comes to studying for the test, the muscle memorizing will already be done! 

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Chapter 8: Joints

                This week I am going to go over Chapter 8 from our book which is all about joints! Joints are articulations with the bones of the skeleton and are the weakest part of the actual skeleton. The main functions of the joints are to give the skeleton mobility and also hold the skeleton together, two very important aspects in anatomy and physiology! Joints can be classified into 3 functional classes; Synarthroses, Amphiarthroses (slightly movable), and Diarthroses (freely movable). There are also three types of fibrous structural joints…

1.  Sutures- This type of joints occurs in the skill between the different bones. It is made up of interlocking junctions that is completely filled with connective tissue fiber. This connective tissue fiber helps bind these bones extremely tightly together but yet still allow growth during youth. In the middle age when the skull bones fuse together they are then called synostoses.

2. Synarthroses- these joints are when bone is connected by a fibrous tissue ligament. These types of joints are immovable. Examples of these types of joints are the tibia and fibula in your leg as well as your radius and ulna in your forearm.  The joint between the tibia and fibula don’t move the skeleton however, they still articulate together in order to support each other.

3. Gomphoses- This fibrous structural joint is better described with the name “peg-in-socket.”  An example of this joint is like a tooth and the way it articulates with the alveolar socket. Remember that the fibrous connection in this joint is the periodontal ligament.

Next, I want to discuss the differences between the two types of cartilaginous joints; synchondroses and symphyses. Synchrondroses is a plate of hyaline cartilage brings the bone together. I like to use the root word chrond- to remember that it means cartilage. An example of the synchrondroses cartilaginous joint is the epiphyseal plate of children. This joint in the bone is made of hyaline cartilage so the bone has room to grow outside of the womb. Another example is the joint between the costal cartilage of the first rib and the sternum. Next, the Symphyses cartilaginous joint is when hyaline cartilage covers the bones where they meet and is fused to an pad of fibrocartilage. An example of symphyses joint is the intervertebral joints and also the pubic symphysis of the pelvis. This type of joint is tricky to visualize, I like to picture it almost like a sandwich. You have your fibrocartilage sandwiched by two pieces of hyaline cartilage and then that is sandwiched by 2 bones.

Check back next week for review on chapter 9!

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Chapter 6: The Skeletal System

Welcome back! This week we are focusing in on the skeletal system which is discussed in GREAT detail in Chapter 6 of our Anatomy & Physiology book.  Bones are classified by the axial skeleton and the appendicular skeleton.  Then, they are further broken down into different classifications by their shape (long, short, flat and irregular bones).  The main functions of the skeletal system are support, protection, movement, mineral/growth factor storage, and blood cell formation.

There are a lot of different types of bone markings, bulges, depressions, and holes that are used for muscle, ligament, and tendon attachment, as joint surfaces, and lastly conduits for blood vessels and nerves. There are a bunch of names for there are different markings, I would recommend making notecards of all these terms for the test because these marking names seem like easy exam questions that you don’t want to miss! Here is a list of all the vocabulary that you should make sure you have memorized!

• ·         Process- any bony prominence
• ·         Tuberosity- rounded projection
• ·         Crest- narrow, prominent ridge of bone
• ·         Trochanter- large, blunt, irregular surface
• ·         Line- narrow ridge of bone
• ·         Tubercle- small rounded projection
• ·         Epicondyle- raised area above a condyle
• ·         Spine- sharp, slender projection
• ·         Head- bony expansion carried on a narrow neck
• ·         Facet- smooth, nearly flat articular surface
• ·         Condyle- rounded articular projection
• ·         Ramus- arm-like bar of bone
• ·         Meatus- canal-like passageway
• ·         Sinus- cavity within a bone
• ·         Fossa- shallow, basin-like depression
• ·         Groove- furrow
• ·         Fissure- narrow, slit-like opening
• ·         Foramen- round or oval opening through a bone

If you memorize these terms, it will be easier to be able to point out certain markings on specific bones during the exam. If you look at the structure that is being asked to identify, you will have these terms memorized and could use process of elimination to figure out the correct answer!

Next, I am briefly going to discuss the 2 different types of bone texture. The first is compact bone. This texture of bone is found right on the inside of the articular cartilage of the bone. It is mostly there for protection. The second texture of bone is spongy bone. This is like honeycomb of trabeculae foiled and it contains red or yellow bone marrow. It is located in the center of the bone.

Remember to keep reviewing and reading for more studying tips and key points from the book!

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