Test 2 bookk - Summary Survey Of Human Anat&Phys; PDF

Preview

Summary

my "book"/guide for test 2...

Description

TEST 2 Bria Washington

[COMPANY NAME] [Company address]

Chapter 1: Muscles The three types of muscle tissue we discussed on test one were skeletal muscles, cardiac muscle and smooth muscle. All muscle cells can send action potentials along itself. We will focus mostly on skeletal muscle for this test. To be considered muscle tissue it must be capable of: excitability ( ability to be stimulated), contractibility (ability to shorten), extensibility (ability to pull out), elasticity (snap back after stretching out) and conductivity (stimulation causing local electrical excitation that sets off a wave of excitability that travels rapidly along the cell and initiates processed leading to contraction). The purpose of muscle is movement with conjunction with bone. It is important for posture and maintaining body temperature with heat production. The motor neuron is multipolar and usually exits the NS (efferent). To stimulate a muscle cell membrane (by chemical, temperature, pressure, etc) it must recognize and respond to the stimulus (excitability). A motor unit consists of a soma, dendrites, axon, axon terminals, neuromuscular junction, and skeletal muscle cells. At the ends of the axon terminals there is a knob that contains a neurotransmitter- in this case acetylcholine. It is important to understand that the skeletal muscle cell is not hooked to the axon terminals it is merely associated with them. Between this association is the neuromuscular junction which is a minute space where acetylcholine does its job. The fewer cells attached to the neuron, the finer control it has. For the motor unit to function we need a message. To turn on a muscle cell it needs to be provided a stimulus, ATP, blood supply, nutrients, glucose, amino acids, eater, etc. Right now, the cell is relaxed (because there is no message) but let’s say we have a message saying “We want these cells to constrict and do their thing”. Each of the skeletal cells will behave in the same way. The message travels down the dendrites to the soma where it is called a graded potential. When it reaches the axons, it is considered an action potential. Myelin sheaths can speed up the action potentials by reducing the amounts of action potentials it stimulates down the axon. Once it reaches the ends of the terminals it results in acetylcholine oozing out (exocytosis) and situating itself with a peripheral protein (ligand gated receptors) on the skeletal muscle cell. This causes voltage (the whole purpose of acetylcholine is to cause AP along the skeletal muscle cell if the threshold is strong enough). This allows an action potential to begin on each of the skeletal muscle. This action potential are considered electrical disturbance. It is depolarization followed by repolarization and that electrical disruption is what tells the stored calcium to slip out into the sarcoplasm. The result is that it will make the basic unit of structure and function-

sarcomere- undergo the sliding filament response. To get this skeletal muscle stimulates, each motor unit needs its own threshold of excitability. When your stimulus is not strong enough to excite the cell (ach oozes out and fixes itself on the peripheral protein but nothing happens) this can be referred to as subthreshold. It is very important to have the ability to vary in your response to a stimulus and what allows that is motor units having different levels of stimulation. For example, if you run fast you are more than likely turning almost every motor unit on in that muscle but if you are just standing straight up you are only using a handful of them. The variation in threshold means that not all motor units will be turned on at the same time. Looking at the calf, your skeletal muscle cells run parallel and a whole bunch of motor units all containing their own threshold within the calf. Taking a cross section of the calf you can see that the cell in not homogenous meaning not all the same. There are three types of connective tissue in skeletal muscle: epimysium, perimysium, and endomysium. Epimysium surrounds the entire skeletal muscle. Perimysium surrounds and separates fascicles. Endomysium surrounds and separates each individual skeletal muscle cell. Within this CT can be: macrophages, fibroblasts, mast cells, plasma cells, adiposcytes, etc. What is the role of the connective tissue to a big muscle? The CT anchors the whole muscle and provides a place where neurons can live (it anchors, secures, and holds the neurons so that when you need to shorten the muscle, they can zap it). This CT protects, nestles and anchors the blood vessels so that the muscle cell can get oxygen, glucose, amino acids, growth hormones, calcium etc… If Nervous System, blood vascular system and lymphatic system is compromised in patients it will influence their use of those muscles. Let’s say you are not taking in enough glucose because you are on a strict diet, you’re going to have to burn fats and proteins for fuel which is not very healthy. So it is always important that we make sure the parts that are feeding our neurons and muscle cells are healthy. Cardiovascular disease is the number one side effect of diabetes so often times diabetics cannot feed the neurons and muscle cells in their feet so the blood supply is limited. This could lead to loosing toes or making neurons insensitive. For example, a serious diabetic could walk outside and step on a splinter and not even know because they do not feel it. CT cells need nutrients in the form of blood so it house capillaries and delicate blood vessels. The lymphatic system is also very important in maintaining and retrieving fluid that cannot get back into the blood vascular system. And it also helps with contraction of skeletal muscle to help blood flow. Your muscle cells also need attachments (tendons, ligaments, and aponeurosis- look up what is in each one) because they need to be tied down to move bones.

The basic unit of structure and function in muscle is the sarcomere. Sarcomeres have limiting membranes and their membrane is called a sarcolemma. They are multi nucleated and nucleus are usually right under the sarcolemma. Holes that go all the way through to the other side of the cell are called t-tubules. T-tubules are lined with sarcolemma and contain extracellular fluid because they are outside the cell. Smooth muscle would not have t- tubules and cardiac muscle would have larger t tubules. We have numerous t-tubules extending along the muscle cell. The endoplasmic reticulum of pivotal cells will be called sarcoplasmic reticulum. It does exist scattered about but there are special places where they are stacked. The place where they are stacked (3D) is all around each t-tubule. Each stack is called a cisternae (like pancakes). In the cisternae will be a special storage of enzymes, raw materials, minerals, calcium ions. Calcium ions are stored here at rest because a high concentration of calcium ions in the cytosol can be lethal (can react with phosphate ions to precipitate as calcium phosphate crystals) and can trigger cell death by apoptosis. Cisternae and t-tubules make up a triad. Sarcomeres give muscles their striated appearance. Skeletal muscle contains a lot of mitochondria (even more in cardiac muscle). To make these mitochondria lots of ATP is needed and we get this energy from glucose that got into the cell because insulin was attached to it. Athletes have lots of mitochondria because there is DNA in the mitochondria that allow it to replicate itself, and athletes are more likely to work out and exercise which increases the amount of mitochondria production. Exercise demands more oxygen which encourages production of the protein that holds oxygen (myoglobin). So basically, when you exercise you take in more oxygen which encourages your cell to make more myoglobin. Myoglobin, glycogen and myofibrils are all found in the sarcoplasm. Glycogen is the storage form of carbohydrates for us, the more glycogen you have, the more opportunity you have for more energy. Myofibrils are what actually shorten and lengthen and can be dividend into thin and thick filaments. When the muscle is at rest you have an H zone. Sarcomeres are divided by Z lines which are close to t-tubules. Thin myofilaments will be composed of actin, troponin, tropomyosin, and ADP active sites. Thick myofilaments will be composed of myosin, ATP, and ATPase. Also stored on here is ATP energy and ATPase (which breaks down ATP to ADP and inorganic phosphate and heat and energy). Stacks of thin myofilaments are called I bands. Down the middle of the sarcomere is just thick myofilament bands, or A bands. The H zone is just thick myofilaments stacked on top of one another (at rest). It will be obliterated when the muscle contracts. Right through the center is the M line. We are going to try to get the sarcomere to “slide together”, and as a result the myofilaments will be sliding on top of one another. It is called the sliding filament theory of how

muscles shorten and lengthen. The left side will move to the right, while the right side moves to the left. Because of all the moving and sliding, the H zone will be obliterated. When shown in a cross section, each individual skeletal muscle cells have their own bundles of cells that resemble fascicles but are referred to as myofibrils. Myofibrils have thick and thin myofilaments. They are the contractile parts of a skeletal muscle cell. Now we can talk about the composition of thin and thick filaments. The main molecule of a thin myofilament will be chains of proteins called actin. The cell made actin by protein synthesis (review). It is made exactly how we make insulin but instead of going out of the cell it stays inside it. Embedded in between the actin will be special sites called ADP active sites. Think of these ADP sites as mini pieces of Velcro. When the sarcomere is at rest, the pieces of Velcro (ADP active sites) will be covered over by a special complex of molecules called the troponin-tropomyosin complex. At rest, the ADP active sites cannot be touched. Thick filaments consists of protein we call myosin. Myosin molecules have a main axis and globular heads. The globular heads are like oars and are versatile. The myosin filaments will eventually want to move towards the outer end of the sarcomere and pull the actin filaments closer to the middle, resulting in shortening the sarcomere (because the thin filaments are attached to the Z lines), and thus, muscle contraction. The ATP sitting on the globular head came from the mitochondria. ATPase came from the polyribosomes because it’s protein for the cell’s use. Say I want to move my arm, the brain sends an action potential along the motor neuron until it synapses with a muscle cell in my arm the receptors on that muscle cell are ligand gated so when our axon terminal knobs release acetylcholine into the synapse the sodium channels open and sodium rushes into the cell as a graded potential. If it becomes strong enough, it causes nearby voltage gated sodium channels to open. Action potentials zip down the sarcolemma and when it travels down one of those t-tubules, voltage sensitive proteins associated with calcium channels are released into the SR. When those channels open the stored calcium gets rushed into the cell and myosin gets very excited. The troponin/tropomyosin complex is blocking the actin (ADP active sites) so that myosin cannot attach but the calcium distracts troponin by binding to its surface causing it to dissociate with the ADP active site. The only myosin that can really bind to the active site are the ones that are attached to an ATP molecule and ATPase. Calcium goes over to the myosin molecule and hydrolyzes ATP (ADP P) creating energy. This energy is then released to do work and that work is that they myosin arms start to engage and disengage with the Velcro (footsies) making the sarcomere shorten. Myosin the moves into a stretched position and binds to actin. It pulls on the actin causing the Z- lines to come in and contraction of the muscle occurs. When it binds it releases all the stored

energy and changes shape. Because the energy is already used for its purpose, ADP and P unbind to myosin and in return a molecule of ATP binds to it. This causes they myosin molecule to dissociate with the actin and prepares itself to hydrolyze that ATP molecule and start the cycle all over again. This is called the sliding filament. Calcium can get back to storage by transport carrier molecules. Retrieval of energy means that you will be able to exercise if you have a source of energy. The following are backup mechanisms to retrieve energy: ADP +CP creatine phosphate, glycogen-myoglobin, anaerobic respiration of glucose- pyruvate lactic acid, and aerobic respiration: time; fatty acid burn: steady slate, glucose- internal action. Chapter 2: Nervous System Your nervous system includes the brain, spinal cord, sense organs, neurons, etc… The nervous system can be broken down into the central and peripheral nervous system. The CNS consists of the brain and the spinal cord. Parts of the brain include the cerebrum (cortex-grey matter & medulla (white matter), diencephalon (thalamus and hypothalamus), mesencephalon (midbrain), pons, medulla oblongota, etc… The PNS is everything but the brain and spinal cord. The PNS can be divided into the somatic and autonomic NS. Somatic relates to skeletal muscle action and autonomic breaks down further into the sympathetic and parasympathetic divisions. The basic unit of structure and function in the NS is the neuron. The spinal cord has 31 spinal nerve pairs. The first seven are cervical, thoracic, lumbar, sacral, and one or to cooygial. These are the nerves of the PNS. Cranial nerves connect to the brain and we have 12 cranial nerves to help communicate with the rest of our body. The spinal cord and brain are enclosed in three fibrous membranes called meninges. These membranes separate the soft tissue of the CNS from the bones of the vertebrae and skull. The three types are dura mater, arachnoid mater and pia mater. Dura mater forms a loose-fitting sleeve called the dural sheath around the spinal cord. It is a tough membrane composed of multiple layers of dense irregular CT. The space between the sheath and vertebral bones is called the epidural space. This space is occupied by blood vessels, adipose tissue and loose connective tissue. Arachnoid mater consists of the arachnoid membrane (five or six layers of squamous to cuboidal cells adhering to the inside of the dura) and a loose array of cells and collagenous and elastic fibers spanning the gap between the arachnoid membrane and the pia mater. The gap is called the subarachnoid space and is filled with cerebrospinal fluid (CSF). Pia mater is a delicate, transparent membranes composed of one or two layers of squamous to cuboidal cells and delicate collagenous and elastic fibers. Grey matter contains the somas, dendrites, and proximal parts of the axons of neurons. It is the site of synaptic contact between neurons making it the site of neural integration

in the spinal cord. This nervous tissue lacks myelin. White has an abundance of myelin and is composed of bundles of axons called tracts that carry signals from one level of the CNS to another. Both grey and whit matter have an abundance of glial cells. The spinal cord has a central core of grey matter that is butterfly shaped. The core consists of two posterior (dorsal) horns which extend toward the posterolateral surfaces of the cord and two thicker anterior (ventral) horns, which extend toward the anterolateral surfaces. The central canal remains open and is lined with ependymal cells (type of glial cell that lines CSF filled ventricles in the brain and the central canal of the SC) and filled with CSF. The posterior horn receives sensory nerve fibers from the spinal nerves, which usually synapse with networks of interneurons in the horn. The anterior horn contains the large neurosomas of motor neuron whose axons lead out to the skeletal muscles. There are an abundance of interneurons and motor neurons in the cervical and lumbar enlargements because these regions are related to motor control and sensation in the upper and lower limbs. Lateral horns contain neurons of the sympathetic NS, which send their axons out of the cord by way of the anterior root along with the somatic efferent fibers. The white matter surrounds the gray matter. It consists of bundles of axons that go up and down the cord and provide avenues of communication between different levels of the CNS. These bundles are arranged in three pairs called columns or funiculi ( a dorals, lateral or ventral column on each side. Each column consists of subdivisions called tracts or fasciculi. Ascending tracts carry sensory information up the cord and descending tracts conduct motor impulses down the cord. All nerve fibers in each tract have similar destination, origin, and function. Many of these fibers have their origin or destination in the brainstem. Several of these tracts undergo decussation (cross over from the left side of the body to the right or vise versa) when they pass up or down the brainstem and spinal cord. As a result the left side of the brain receives sensory information from the right side of the body and sends motor comm ands to that side while the right side of the brain senses and controls the left side of the body. When the origin and destination of a tract are on opposite sides of the body we say they are contralateral to each other. When the trace does not decussate, its origin and destination are on the same side od the body and we call that ipsilateral. The spinothalamic tract starts in the spinal cord and ends in the thalamus and responds to pain and temperature. The spinocerebellar tract starts in the spinal cord and end in the cerebellum by way of the inferior peduncle. Also know faciculus gracious (cuneatus), corticospinal, reticulospinal

The SC communicates with the rest of the body using spinal nerves. A nerve is a cordlike organ composed of numerous nerve fibers (axons) bound together by CT. As we move down the spinal nerves they divide into smaller branches called peripheral nerves. Nerve fibers of the PNS are surrounded by Schwann cells which form a neurilemma and often a myelin sheath around the axon. Each fiber is surrounded by a thin sheet of loose CT called endoneurium. In most Neves the fibers are gathered into fascicles each wrapped in perineurium. Several fascicles are bundled together and wrapped into epineurium to compose the nerve. Nerves have high metabolic rates and need a plentiful blood supply which is furnished by blood vessels that penetrate these connective tissue coverings. Peripheral nerve fibers can be sensory (afferent) that carry signals from sensory receptors in the CNS and motor (efferent) carrying signals from the CNS to muscles and glands. Most nerves are mixed meaning they consist of both afferent and efferent fibers and therefore conduct signals in two directions. A gangelion is a knot in the nerve that is a cluster of neurosomas outside the CNS. The dorsal root swells to form the dorsal root gangelion which contains somas of sensory neurons. The meningeal branch reenter the vertebral canal and innervates the meninges, vertebrae and spinal ligaments with sensory and motor fibers. The posterior branch carries information that supplies muscles and sensations to the back. The functions of the spinal cord include conduction, neural integration, locomotion and reflexes. The spinal cord contains bundles of nerve fibers that conduct info up and down the cord connecting different levels of the trunk with each other and with the brain enabling sensory information to reach the brain, motor commands to reach the effectors, and input received at one level of the cord to affect output from another level. Pools of spinal neurons receive input from multiple sources, integrate the information and execute an appropriate output. Spinal reflexes play vital roles in posture, motor coordination and protective responses to pain or injury. SENARIO I am standing in the kitchen in front of an electric stove and I put my left hand on top of the electric stove and all of a sudden my hand moves back (reflex; flex). QUESTION: What was the energy i...