However, the fluid outside the axon has a positive charge. Due to the different charges of the outside and inside of the axon, the axon is polarized. When a neuron is “fired”, several events take place to create an electrical impulse called an action potential. Sodium ions, which have a positive charge (Na+), enter the axon. This process depolarizes the axon, which changes the electrical charge inside the axon from negative to positive.
UNIVERSITY OF SHARJAH COLLEGE OF MEDICINE MUSCLOSKELETAL UNIT PHYSIOLOGY PRACTICAL HANDOUT PREPARED BY: DR SUNDUS AL-OMAR ACADEMIC YEAR (2011-2012) Nerve Conduction Velocity Theory background The nerve impulse is a wave of depolarization immediately followed by a wave of repolarization, collectively called an action potential, occurring on the plasma membrane of a nerve fiber. Changes in ion conductance across the nerve fiber membrane are responsible for the initiation and propagation of the action potential. Experimentally, these changes can be the result of electrical current applied through electrodes. Once initiated, an action potential is usually propagated without decrement in amplitude or velocity along the plasma membrane of a nerve fiber. In the peripheral nervous system, nerve fibers of various diameters and functions (motor and sensory) are bundled together by connective tissue to form nerves.
Controlled Variables: frequency of stimulation; stimulation voltage; temperature Effect of Stimulation Frequency on Contraction 1. Dependent Variable: contraction force 2. Independent Variable: frequency of stimulation 3. Controlled Variables: stimulation voltage; temperature 4. What structure was stimulated to cause a muscle contraction?
Change Blindness: A Vision Phenomenon Kayla Miller Morningside College Abstract This paper discusses the phenomenon of change blindness or inattentional blindness. Change blindness is the failure to notice obvious changes or events in our visual environment (Robinson- Riegler & Robinson-Riegler, 2008). In this study, a flicker paradigm was used. A flicker paradigm is when an original and a modified image continually alternate, one after the other, with a brief blank field between the two. The results clearly indicate that reaction time was quicker when the change appeared in the center of the screen rather than the marginal region of the screen.
It has a complex structure consisting of a transparent lens that focuses light on the retina. The retina is covered with two basic types of light-sensitive cells-rods and cones. The cone cells are sensitive to color and are located in the part of the retina called the fovea, where the light is focused by the lens. The rod cells are not sensitive to color, but have greater sensitivity to light than the cone cells. These cells are located around the fovea and are responsible for peripheral vision and night vision.
It protects the fluids inside and outside the neuron. The fluid that is inside and outside the neuron is a solution that has electrical charged particles called Ions. When the neurons are at rest there are more negative ions on the inside of the neuron than the outside, but, when a message is delivered, the membrane that is protecting the fluids, opens to receive the message and positive ions flow in. When information moves from one neuron to the next it has to cross what is called a synaptic space. A synaptic space is a tiny gap between neurons and dendrites.
Axon fibers from the nasal retina of each eye cross to the opposite side of the chiasm, while axon fibers from the temporal retina of each eye continue on the same side. The realigned axons emerge from the chiasm as the left and right optic tracts, ending in the left and right lateral geniculate bodies. From there the axons connect to the optic radiations, which travel to the right and left halves of the visual cortex of the brain. We all also have a blind spot. This blind spot is a small portion of the visual field of each eye that corresponds to the position of the optic nerve.
Neurotransmitters (NT) act as chemical messengers in the body. Specifically, they function to transmit signals from a neuron to a target cell across a potential space known as a synapse, or synaptic cleft. In effect, this allows one nerve cell to communicate with a second nerve cell. Some common neurotransmitters are acetylcholine, norepinephrine, dopamine, serotonin and gamma aminobutyric acid (GABA). Acetylcholine and norepinephrine are excitatory neurotransmitters while dopamine, serotonin, and GABA are inhibitory (Kau-Nu, 2011).
Being able to understand the visual system means being able to appreciate how we see and occasionally, why we see certain unusual things, such as visual illusions. Vision seems uncomplicated and effortless, by simply opening your eyes; the surrounding environment can be seen. The simplicity of such an easy task is an illusion in itself. A visual illusion is often known as a trick of the eye or the mind. Visual illusions are characterised by images that are seen but are actually different from the objective real world.
These imperfections in the focusing power of the eye are called refractive errors. There are four primary types of refractive errors: myopia, hyperopia, astigmatism and presbyopia. Persons with myopia (figure 2), or nearsightedness, have more difficulty seeing distant objects as clearly as near objects. Persons with hyperopia (figure 3), or farsightedness, have more difficulty seeing near objects as clearly as distant objects. Astigmatism (figure 4) is a distortion of the image on the retina caused by irregularities in the cornea or lens of the eye.