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Peripheral Nervous System: The Peripheral nervous system (PNS) is the division of the nervous system containing all the nerves that lie outside of the central nervous system (CNS). The primary role of the PNS is to connect the CNS to the organs, limbs, and skin. These nerves extend from the central nervous  system to the outermost areas of the body. The peripheral system allows the brain and spinal cord to receive and send information to other areas of the body, which allows us to react to stimuli in our environment. The nerves that make up the peripheral nervous system are actually the axons or bundles of axons from neuron cells. In some cases, these nerves are very small but some nerve bundles are so large that they can be easily seen by the human eye.  

Skeletal Muscle Structure Skeletal muscles are composed of a large number of muscle fibers. Each muscle fiber has no one or more nuclei which lie in the periphery. The cytoplasm of the muscle cell is as sarcoplasm. Skeletal muscles are composed primarily of contractile material. Skeletal muscle is a composite tissue of connective tissue, blood vessels, and nerves as well as contractile material, these “minor” tissues may strongly influence muscle function. Myofibrils are very small parallel filaments which lie in the cytoplasm. The membrane of the muscle fiber is called as sarcolemma. Each muscle fiber is embedded in a connective tissue called endomysium. The fibers within a muscle are arranged in bundles. Each bundle is enclosed in a sheath called perimysium.  

Conducting system of the heart Conducting system of the heart: the impulse for cardiac contraction is transmitted through the conduction system of the heart. This system is made of : Sino atrial node (SA-node) Atrioventricular node (AV-node) Bundle of his Purkinje fibers. Heart sounds:  Totally 4 sounds are produced by the heart. The first sound as LUB and the second sound as DUB can be heard with a stethoscope. The third and fourth sounds cannot be heard. The “ lub” is the first heart sound, commonly termed S1, and is caused by turbulence caused by the closure of mitral and tricuspid valves at the start of systole. The second sound, “dub” or S2, is caused by the closure of aortic and pulmonic valves, marking the end of systole. Heart Murmurs. The most common abnormal heart sound is a heart murmur. A murmur is a blowing, whooshing, or rasping sound that occurs during your heartbeat. Pulse: its throbbing sensation felt over the walls of arteries. It’s defined as the pressure difference transmitted in the form of a wave over the arterial walls. Heart Rate: the normal resting heart rate for adults ranges from 60 to 100 beats a minute. The wrist is the common site where the pulse is usually felt. At this site, the radial artery is very superficial. This pulse is called as a radial pulse. Other arteries where a pulse can be felt are a carotid artery. Facial artery and temporal artery. In case of fever, the rate of pulse increases at the rate of 10 per every rise of 1F.Generally, veins don’t exhibit pulsation. The only vein which exhibits pulsation is jugular vein which is nearer to the heart.  

Classification of Bones according to shape Long bones: Long bones are characterized by a long tubular shaft and an articular surface at each end of the bone where ligaments and tendons attach. They’re found in the limbs to facilitate movement and support the weight of the body. These bones include the major bones of the arms and legs such as the humerus and femur, tibia and fibula, and the radius and ulna. Short bones: Short bones are roughly cube shaped and are as long as they are wide. It has no shaft but it contains a spongy substance covered by a shell of the compact. Helps to provide stability and movement within the ankle and wrist joints. They provide little to no movement. Examples of this type of bone include the carpals and metacarpals in the wrists and ankles. Flat bones: The primary purpose of this type of bone is to protect internal organs such as the brain, heart, and lungs. It also provides a large surface area for muscles to attach to. Examples of this type of bone include the cranium (skull), the thoracic cage (sternum and ribs) and the ilium (pelvis).  These contain two layers of compact bone with a spongy substance in between. Irregular bones: This type doesn’t fall in any category e.g. vertebrae and the bones of the face. These bones vary in size and structure with the shape usually being very complex. Irregular bones serve different functions depending on location. Sesamoid bones: they are small bones which develop in the tendons of muscles e.g. patella of the knee joint. The function of this bone is to protect tendons and diminish friction and wear on joint surfaces.  

Pulmonary Ventilation Smooth muscle cells in the walls of the bronchioles adjust their diameter and help to control the flow of air into the alveoli of the lungs. The muscles of the thoracic cavity, including the diaphragm and intercostal muscles, change the volume of the thoracic cavity to force air into and out of the lungs. The diaphragm contracts and pushes itself into the abdominal cavity, increasing the volume of the thoracic cavity and expanding the lungs to draw in fresh atmospheric air. When it relaxes, the diaphragm returns to its original position and forces air out of the lungs during exhalation. The intercostal muscles also aid in respiration by lifting the ribs during deep inhalation to increase the size of the thoracic cavity and by pushing the ribs together during deep exhalation to decrease the thoracic cavity.  

Nervous System The nervous system has been divided into two components: The central nervous system which is composed of the brain and the spinal cord, and the peripheral nervous system, which is composed of ganglia and peripheral nerves that lie outside the brain and spinal cord. The peripheral nervous system has been, in turn, divided into two subsystems: Somatic and autonomic. Somatic Nervous system (SNS): The somatic nervous system is responsible for the movement of voluntary muscles and the process known as a reflex arc. This system carries nerve impulses back and forth between the central nervous system and the skeletal muscle’s, skin and the sense organs. Autonomic Nervous system (ANS): The Autonomic Nervous system controls and regulates the internal organs without any conscious recognition or effort by the organism.  

CHARACTERISTICS OF SKELETAL MUSCLES The four major functional characteristics of skeletal muscle are: Contractility    – The ability to shorten which causes movement of the structures to which the muscles are attached. Excitability      – The ability to respond or contract in response to chemical and/or electrical signals. Extensibility     –  The capacity to stretch to the normal resting length after contracting Elasticity          – The ability to return to the original resting length after a muscle has been stretched. Functions of Muscles: Movement: Skeletal muscles move bones by pulling on them and work together to produce smooth movements of our limbs. Mobility is your muscular system’s simplest and most crucial function. Your skeletal muscles are largely responsible for the movements and motions you make. Skeletal muscles are attached to your bones. Maintaining posture, muscle tone, and Stabilizing joints: Skeletal muscles also control posture, from your head down to your toes. Flexibility and strength are keys to maintaining proper posture. Stiff neck muscles, weak back muscles, and tight hip muscles, among other ailments, can throw off your alignment. Producing Heat & Temperature Regulation: most of the heat required for this is produced by muscles, which generate heat as they contract. Skeletal muscle accounts for at least 40% of body mass and is the muscle type responsible for generating most body heat. Circulation: The involuntary cardiac and smooth muscles help your heart beat and blood flow through your body. The cardiac muscle, known as the myocardium, is found in the walls of the heart. The cardiac muscle is controlled by the autonomic nervous system, which is responsible for most bodily functions.  

Cardiac Output The cardiac output is simply the amount of blood pumped by the heart per minute. Necessarily, the cardiac output is the product of the heart rate, which is the number of beats per minute, and the stroke volume, which is amount pumped per beat. Stroke volume is the amount of blood ejected per beat of the heart. It’s about 70ml. so every mixture about 5040 ml nearly 5 liters of blood is pumped by the heart. Cardiac output depends on the following factors:  

Bone structure and formation: Bone is the hardest of the connective tissues. Compact bone (Cortical Bone) and Spongy bone (Spongy Bone) are the two types of osseous tissue or bone tissue that make up bones. The bones are mostly composed of an outer layer of compact bone and an inner layer of spongy bone. Ossification is the process of bone formation. Parts of the skeleton form during the first few weeks after conception. By the end of the eighth week after conception, the skeletal pattern is formed in cartilage and connective tissue membranes and ossification begins.   Compact bone (Cortical Bone): Due to the strength of compact bone, its main functions is to support the entire body. Compact pact bone also stores calcium. While calcium is being stored in the bone it is also the principle molecule that hardens compact bone. Cancellous bone (Spongy Bone): It looks spongy and found in the ends of the long bones, short bones and in between two layers of compact tissue of flat bones. Due to the sponge-like or porous nature of spongy or cancellous bone, spongy bone has a greater surface area compared to compact bone.  This allows the bone marrow to develop in the region of the spongy bone. The branching nature of spongy bone also makes it a prime target in diseases such as osteoporosis.  

Lungs Volume The total air volume of the lungs is about 4 to 6 liters and varies with a person’s size, age, gender, and respiratory health.   Normal shallow breathing only moves a small fraction of the lungs’ total volume into and out of the body with each breath. This volume of air, known as tidal volume, usually measures only around 0.5 liters. Deep breathing can force more air into and out of the lungs than during shallow breathing. The volume of air exchanged during deep breathing is known as vital capacity and ranges between 3 to 5 liters, depending on the lung capacity of the individual. There is a residual volume of around 1 liter of air that remains in the lungs at all times, even during a deep exhalation.  

The Central Nervous System: The Central Nervous System comprises of the Brain and the Spinal cord: The Brain plays a central role in the control of most bodily functions, which includes awareness, movements, sensations, thoughts, speech, and memory. The brain takes in sensory information, organizes and synthesizes this input, then provides instructions for motor output to the rest of the body. The brain is the main data center of the body, consisting of the cerebrum (which regulates Cognitive functions) and the cerebellum (which regulates coordination and muscular skeletal functions). The Spinal cord consists of nerves that carry incoming and outgoing messages between the brain and the rest of the body. Spinal cord acts as the center for reflexes. Brain: The human brain is the command center for the human nervous system. It receives input from the sensory organs and sends output to the muscles. The Human Brain weighs about 1.5 kilograms, it makes up about 2 percent of a human’s body weight. The cerebrum makes up 85 percent of the brain’s weight composing of nearly 86 billion neurons. The neurons are the structural and functional unit of the nervous system. The brain develops from 3 sections, they are as follows. Forebrain: also known as prosencephalon, is the anterior part of the brain, includes the cerebral hemispheres, the thalamus forebrain develops into the cerebrum and underlying structures. Midbrain: also known as mesencephalon becomes part of the brainstem, serves important functions like motor activity and sensory functions. Hindbrain: the lower part of the brain stem, comprising the cerebellum, pons cerebelli, and medulla oblongata. Parts of the Brain and functions: AMYGDALA: Lying deep in the center of the limbic emotional brain, this powerful structure, the size, and shape of an almond, is constantly alert to the needs of basic survival. BRAIN STEM: The part of the brain that connects to the spinal cord. The brain stem controls function basic to the survival of all animals, such as heart rate, breathing, digesting foods, and sleeping. It also plays a role in learning. CEREBRUM: This is the largest brain structure in humans and accounts for about two-thirds of the brain’s mass. The two hemispheres of the cerebrum are connected by long neuron branches called the corpus callosum. The cerebrum control most of our body functions such as the state of consciousness, the senses, the body’s motor skills, reasoning, and language. CEREBELLUM: Two peach-size mounds of folded tissue located at the top of the brain stem. It controls most of the learning pathways and coordinated skilled movements. The Frontal Lobe is the most recently-evolved part of the brain. The frontal lobe is dorsolateral prefrontal circuit is the brain’s top executive. It organizes responses to complex problems, plans steps to an objective, searches memory for relevant experience, adapts strategies to accommodate new data, guides behavior with verbal skills and houses working memory. The Temporal Lobe controls memory storage area, emotion, hearing, and, on the left side, language. The Parietal Lobe receives and processes sensory information from the body including calculating location and speed of objects. The Occipital Lobe processes visual data and routes it to other parts of the brain for identification and storage. HIPPOCAMPUS: located deep within the brain, it processes new memories for long-term storage. If you didn’t have it, you couldn’t live in the present, you’d be stuck in the past of old memories. It is among the first functions to falter in Alzheimer’s. HYPOTHALAMUS: Located at the base of the brain where signals from the brain and the body’s hormonal system interact, the hypothalamus maintains the body’s status quo. It monitors numerous bodily functions such as blood pressure and body temperature, as well as controlling body weight and appetite. THALAMUS: Located at the top of the brain stem, the thalamus acts as a two-way relay station, sorting, processing, and directing signals from the spinal cord and midbrain structures up to the cerebrum, and, conversely, from the cerebrum down the spinal cord to the nervous system. Spinal Cord: The spinal cord is a long, fragile tube-like structure that begins at the spinal cord extends from the foramen magnum where it is continuous with the medulla to the level of the first or second lumbar vertebrae. Spinal Cord is a vital link between the brain and the body, and from the body to the brain, which is 40 to 50 cm long and 1 cm to 1.5 cm in diameter. Two consecutive rows of nerve roots emerge on each of its sides, these nerve roots join distally to form 31 pairs of spinal nerves. The spinal cord is a cylindrical structure of nervous tissue composed of white and gray matter, is uniformly organized and is divided into four regions: cervical (C), thoracic (T), lumbar (L) and sacral (S). The spinal cord consists of nerves that carry incoming and outgoing messages between the brain and the rest of the body. It is also the center for reflexes, such as the knee jerk reflex. The spinal nerve roots are formed by the union of dorsal and ventral roots within the intervertebral foramen, resulting in a mixed nerve joined together and forming the spinal nerve. The arterial blood supply to the spinal cord in the upper cervical regions is derived from two branches of the vertebral arteries, the anterior spinal artery, and the posterior spinal arteries. At the level of the medulla, the paired anterior spinal arteries join to form a single artery that lies in the anterior median fissure of the spinal cord. The posterior spinal arteries are paired and form an anastomotic chain over the posterior aspect of the spinal cord. A plexus of small arteries, the arterial vasocorona, on the surface of the cord constitutes an anastomotic connection between the anterior and posterior spinal arteries. This arrangement provides uninterrupted blood supplies along the entire length of the spinal cord. Functions: conducts sensory information from the peripheral nervous system (both somatic and autonomic) to the brain, the spinal nerves carry sensory information (sensations) from the

Muscular tissues can be classified into: Smooth, non-striated or involuntary muscles. Cardiac muscle or myocardium. Skeletal, striated or voluntary muscles. Skeletal muscles: Skeletal muscle comes in different shapes and sizes and allows movement of the body and body parts. These muscles have the longest fibers. Skeletal muscles have striations and can be controlled voluntarily. Skeletal muscles are able to contract very rapidly but they tire easily; they must also rest after relatively short periods of activity otherwise physical damage and muscle fatigue will occur. Skeletal muscles can exert tremendous power and are remarkably adaptable. Skeletal muscle is attached to the skeleton. The movement of these muscles also cannot be controlled by will. Smooth muscle Smooth muscle tissue is found in the walls of the hollow visceral organs such as the respiratory passages, intestinal tract and urinary bladder. This is not striated and is involuntary. Contractions of smooth muscles are slow and sustained. The contraction of most of these muscles forces fluid and other substances through the internal body channels. Smooth muscle contractions are involuntary movements triggered by impulses that travel through the autonomic nervous system to the smooth muscle tissue. The arrangement of cells within smooth muscle tissue allows for contraction and relaxation with great elasticity. The smooth muscle in the walls of organs like the urinary bladder and the uterus allow those organs to expand and relax as needed. The smooth muscle of the alimentary canal (the digestive tract) facilitates the peristaltic waves that move swallowed food and nutrients. In the eye, smooth muscle changes the shape of the lens to bring objects into focus. Artery walls include smooth muscle that relaxes and contracts to move blood through the body. Cardiac muscle:             Cardiac muscle makes up most of the heart walls. The muscles are striated and are involuntary – we have almost no conscious control over how our heart beats. The heart wall is composed of three layers. The middle layer, the myocardium, is responsible for the heart’s pumping action. Cardiac muscle found only in the myocardium, contracts in response to signals from the cardiac conduction system to make the heartbeat. Cardiac muscle is made from cells called cardiocytes. Cardiac muscle cells usually contract at a steady pace set by the heart’s pacemaker cells, though nerves can influence them to speed up or slow down. The cardiac muscle tissue forms many branches, which then recombine to form a continuous sheet. This enables the tissue to contract as a unit and improves its efficiency. Cardiac muscle never rests – to do so would be fatal. Contractions of cardiac muscle move blood through the heart and around the body.  

Cardiovascular system Humans have a closed circulatory system. You may remember that in a closed system blood is contained within vessels and that the main components of a closed circulatory system are the heart, blood vessels, and blood. Heart The heart is a conical, hollow, musculotendinous organ. It lies in the thorax between the lungs and behind the sternum. It’s about 10cm long and weighs about 300 gram. The base of the heart is above and the apex is below. The heart lies in the thorax between the lungs and behind the sternum. Two-thirds of the heart is on the left side. It lies obliquely. It’s directed more towards the left side than on the right side. The apex of the heart lies at the level of 5th intercostals space, 9cm to the left of midline. The base extends to the level of the second rib. The 3 Layers of Heart: The heart is surrounded by an outer covering called pericardium. It contains two layers called visceral pericardium and parietal pericardium. Pericardial fluid is present between these two layers. The middle layer is made of heart muscle fibers. It’s called as myocardium The inner lining is called as endocardium. Chambers of the heart: The Human heart has four chambers: two atria and two ventricles. The 2 chambers on the right side are known as Right Atrium, Right Ventricle. The 2 chambers on the left side are called Left Atrium, Left Ventricle. The 4 chambers are divided by 2 septa, the interatrial septum, and Inter-Ventricular septum. Valves of the heart: The heart has 4 valves: they are as follows The mitral valve and tricuspid valve, which controls blood flow from the atria to the ventricles. The aortic valve and pulmonary valve, which control blood flow out of the ventricles.  Some tendinous cords arise from the lower border of these valves. They’re called chordate tendinae. The chordate tendinae in turn attached to papillary muscle which arises from ventricular walls. Blood vessels attached to heart: the right atrium receives superior vena cava vein and inferior vena cava vein. They carry venous blood to the heart. From the right ventricle, arise the pulmonary artery. It carries venous blood to lungs for oxygenation. The left atrium receives 4 pulmonary veins. They carry oxygenated blood to the heart. From the left ventricle. Arise the aorta. It delivers pure-blood to all parts of the body. Blood supply to the heart: The heart receives its blood supply through right and left coronary arteries. They’re the first branches of the aorta. Venous blood heart is collected by the coronary sinus. It opens directly into the right atrium. Nerve supply to the heart: The heart is supplied by sympathetic and vagus nerves. Branches from these nerves pass through the sino auricular node.  

Blood pressure (BP) It’s the lateral pressure excreted by blood on blood vessels. It’s normally expressed as arterial pressure. It has 2 phases: Systolic blood pressure: it’s the maximum pressure occurs during the systole of the heart range from 100 to 120 mm Diastolic blood pressure: it’s the minimum pressure occurs during the diastole of the heart range between 60 to 80 mm Hg. Pulse pressure is the difference between systolic and diastolic blood pressure and it’s nearly 40 mm Hg.