Human Physiology(Part I)

•Neurons and Nervous System

•Brain

•Spinal Chord

•Muscles

•Heart

Neurons and Nervous System•DefinitionA neuron is a specialized cell of the nervous system designed to rapidly communicate with other neurons and organs by sending chemical and electrical signals.Description•The nervous system contains two major types of cells, neurons and glia. Neurons are specialized cells of the central and peripheral nervous systems that play key roles in transmitting and propagating information from one neuron to another.

•The role of glial cells is less clear, but they are involved in supporting the functions of the neuron. •There are many different types of neurons, such as motor neurons, sensory neurons, and interneuron. Each class of neuron is specially designed to perform certain functions, and therefore neuronal populations differ in structure and chemical composition.

Neuron Animation

Nervous System Animation (synapses)

Brain• The cerebral is a structure within the brain with distinct structural and functional properties. It contains all of the centers that receive and interpret sensory information, initiate movement, analyze information, reason and experience emotions.

•The surface of the cerebral cortex is folded in large mammals where more than two thirds of the cortical surface is buried in the grooves, called "sulci". Association areasAssociation areas comprise three major groups:Parietal, temporal, and occipital lobes - all located in the posterior part of the brain - are involved in producing our perceptions resulting from what our eyes see, ears hear, and other sensory organs inform us about the position of different parts of our body and relate them to the position of other objects in the environment Frontal lobe - called prefrontal association complex and involved in planning actions and movement, as well as abstract thought Limbic association area - involved in emotion and memory.

•The cerebellum (Latin: "little brain") is a region of the brain that plays an important role in the integration of sensory perception and motor output . The cerebellum integrates these pathways, using the constant feedback on body position to fine-tune motor movements. (Learned-Programmed sequences)

Brain Function Animation

Motor areas•The motor areas are located in both hemispheres of the cortex.• They are shaped like a pair of headphones stretching from ear to ear. •The motor areas are very closely related to the control of voluntary movements, especially fine fragmented movements performed by the hand. The right half of the motor area controls the left side of your body and vice versa.

Brain (continued)

•The vertebral column is divided into the cervical, thoracic, and lumbar region. It provides structural support for the trunk and surrounds and protects the spinal cord. The vertebral column also provides attachment points for the muscles of the back and ribs.

•The vertebral column is divided into the cervical, thoracic, and lumbar region. It provides structural support for the trunk and surrounds and protects the spinal cord. The vertebral column also provides attachment points for the muscles of the back and ribs.

Spinal Chord

•These are twelve vertebra of the mid back.

• The last vertebra (on the left side of the picture) attaches to the lumbar (lower) spine, and the top vertebra (on the right) attaches to the cervical (neck) section of the back.

•The vertebra are broader and stronger than the cervical bones. This allows them to absorb the added pressure applied to the mid back, but they remain a common sight of injury.

•The vertebra are numbered from one to twelve and labeled T1, T2, T3 etc. from the upper most bones to the lowest.

Spinal Chord (continued)

Muscles perform four essential functions: They maintain body posture, stabilize joints, produce movement and generate heat we need to survive. This animation illustrates what different muscles do and how muscles work together.

Skeletal Muscles

Skeletal muscle, or striated muscle, is the type of muscle you can see and feel. Learn about skeletal muscle and its complex structure, from muscle. Skeletal muscle is also called striated muscle, because when it is viewed under polarized light or stained with an indicator, you can see alternating striations.

Cardiac and Smooth Muscles

Smooth muscle and cardiac muscle contract involuntarily. While most of the processes are similar, there are some notable differences between the actions of skeletal, cardiac and smooth muscle.

•Skeletal muscle is a well-organized body tissue. During muscle contractions, sections of muscle fiber fit together like pieces of a puzzle.

Muscles

Muscle Animation

Skeletal Muscle

Heart

•The heart is a pump

•The heart is made up of four main chambers, two ventricles and two atria. This animation illustrates the flow of blood through the heart, to and from the four main vessels that connect to it.

•Each chamber has a sort of one-way valve at its exit that prevents blood from flowing backwards. When each chamber contracts, the valve at its exit opens. When it is finished contracting, the valve closes so that blood does not flow backwards.

•The tricuspid valve is at the exit of the right atrium. •The pulmonary valve is at the exit of the right ventricle. •The mitral valve is at the exit of the left atrium. •The aortic valve is at the exit of the left ventricle.

Heart Pumping Simulation

Heart (continued)

•When the heart muscle contracts or beats (called systole), it pumps blood out of the heart. The heart contracts in two stages. In the first stage, the right and left atria contract at the same time, pumping blood to the right and left ventricles. Then the ventricles contract together to propel blood out of the heart. •Then the heart muscle relaxes (called diastole) before the next heartbeat. This allows blood to fill up the heart again.

The right and left sides of the heart have separate functions.

•The right side of the heart collects oxygen-poor blood from the body and pumps it to the lungs where it picks up oxygen and releases carbon dioxide.

•The left side of the heart then collects oxygen-rich blood from the lungs and pumps it to the body so that the cells throughout your body have the oxygen they need to function properly.

Blood Pressure Simulation

Heart (continued)Electrical System:

•A special group of cells that have the ability to generate electrical activity on their own are responsible for the heart beating.

•The natural pacemaker of the heart is called the sinoatrial node (SA node). It is located in the right atrium. The heart also contains specialized fibers that conduct the electrical impulse from the pacemaker (SA node) to the rest of the heart

•The electrical impulse leaves the SA node (1) and travels to the right and left atria, causing them to contract together. This takes .04 seconds. There is now a natural delay to allow the atria to contract and the ventricles to fill up with blood. The electrical impulse has now traveled to the atrioventricular node (AV node) (2). The electrical impulse now goes to the Bundle of His (3), then it divides into the right and left bundle branches (4) where it rapidly spreads using Purkinje fibers (5) to the muscles of the right and left ventricle, causing them to contract at the same time.

Heart Electrical Impulses Simulation

Heart (continued)

Although the pacemaker cells create the electrical impulse that causes the heart to beat, other nerves can change the rate at which the pacemaker cells fire and the how strongly the heart contracts. These nerves are part of the autonomic nervous system. The autonomic nervous system has two parts - The sympathetic nervous system and the parasympathetic nervous system. The sympathetic nerves increase the heart rate and increase the force of contraction. The parasympathetic nerves do the opposite.

All this activity produces electrical waves we can measure. The measurement is typically represented as a graph called an electrocardiogram (EKG). Here is an example of three heartbeats from an EKG

Each part of the tracing has a lettered name: • P wave - coincides with the spread of electrical activity over the atria and the beginning

of its contraction. • QRS complex - coincides with the spread of electrical activity over the ventricles and the

beginning of its contraction. • T wave - coincides with the recovery phase of the ventricles.

Heart (continued)Arrhythmia

•An irregular heartbeat, or arrhythmia, can result from a change in the heart's standard electrical conduction system. •A serious variety of arrhythmia is known as fibrillation. The muscle cells of the heart normally function together, creating a single contraction when stimulated. Fibrillation occurs when the heart muscle begins a quivering motion due to a disunity in contractile cell function. Fibrillation can affect the atrium (atrial fibrillation) or the ventricle (ventricular fibrillation); ventricular fibrillation is imminently life-threatening.•Atrial fibrillation is the quivering, chaotic motion in the upper chambers of the heart, known as the atria. •Ventricular fibrillation occurs in the ventricles (lower chambers) of the heart; it is always a medical emergency. If left untreated, ventricular fibrillation (VF, or V-fib) can lead to death within minutes. When a heart goes into V-fib, effective pumping of the blood stops. V-fib is considered a form of cardiac arrest, and an individual suffering from it will not survive unless cardiopulmonary resuscitation (CPR) and defibrillation are provided immediately.

•CPR can prolong the survival of the brain in the lack of a normal pulse, but defibrillation is the intervention which is most likely to restore a more healthy heart rhythm. It does this by applying an electric shock to the heart, after which sometimes the heart will revert to a rhythm that can once again pump blood.

Almost every person goes into ventricular fibrillation in the last few minutes of life as the heart muscle reacts to diminished oxygen or general blood flow, trauma, irritants, or depression of electrical impulses themselves from the brain.

Arrhythmia simulation

EYE

•Structures in the eye translate light into images. By way of refraction, the image is actually reversed and upside-down when it reaches the retina. The occipital lobe in the brain "rights the image" so we perceive it properly

•As light enters the eye, it strikes the receptor cells of the retina, called the rods and cones.

•A rod cell is sensitive enough to respond to a single photon of light, and is about 100 times more sensitive to a single photon than cones. Since rods require less light to function than cones, they are therefore the primary source of visual information at night (scotopic vision). (black and white)

• Cone cells, on the other hand, require tens to hundreds of photons to become activated. (color vision)

Eye (General) Simulation

Eye (rods and cones) shory