Compare and contrast the propagation of electrical signals down the axon and the transmission of the signal across a synapse.
The nervous system is one of the most intricate and fundamental systems within the human body. It is constructed from specialised cells called neurons (Willmer, et al., 2005). Information from a stimulus is carried by neurons as chemical and electrical signals to the central nervous system or CNS, electrical signals in particular are imperative as they carry “time-sensitive information rapidly and over a long distance” (Kandel, et al., 2000). A neuron has a cell body, and within it is a nucleus. The cell body has dendrites which are short, branched cytoplasmic extensions and “usually one outgoing axon” (Willmer, et al.,
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(Stefan, 2006) . Nerve cells are classed as “excitable cells” (Londish, et al., 2012), this means that the interior of the cell is more negatively charged than the exterior. The voltage of the inside of the axon is – 70 mV with respect to the outside of the cell, this electrochemical equilibrium is what leads to a resting potential. The resting membrane potential arises due to the “distribution of ions in the intracellular and extracellular fluid” as the intracellular fluid has “low sodium and chloride ions but high potassium ions” and extracellular is the opposite it has “a high concentration of sodium ions and chloride ions” (Matthews, 2009). This can be calculated using the Nernst calculation. It results from the “small proportion of K+ ions leaving the inside of the cell and accumulating on its outside” (Willmer, et al., …show more content…
A graded potential is first produced to depolarise the axon, action potentials are all or nothing so if the electrical signal is weak it will not produce an action potential as it does not reach threshold value, “they are called acute subthreshold potentials” (Guyton & Hall, 2006); however graded potentials add together this is called summation and the axon hillock decides whether the potential as a whole is higher than the threshold value and if electrical signal reaches goes beyond threshold which is around -55 mV an action potential is generated (figure 2). This causes the cell to become slightly depolarised because Na+ ions flow through the few sodium voltage gated ions that are open, which causes more of the gated sodium channels to open; “ thus we get a positive feedback and an explosive self – amplifying depolarisation”, At this point the “membrane is more permeable to Na+” (Willmer, et al., 2005). The membrane potential changes from “-70 mv to +50 mV” (Willmer, et al., 2005), the sodium ion channels are inactivated and potassium ion channels are activated and K+ ions flow out of the cell which repolarises the membrane. The membrane becomes hyperpolarised as the potassium voltage- gated channels remain open, the resting potential is restored due to the sodium- potassium pump and voltage- gated potassium channels close. The signal then
In the beginning phases of muscle contraction, a “cocked” motor neuron in the spinal cord is activated to form a neuromuscular junction with each muscle fiber when it begins branching out to each cell. An action potential is passed down the nerve, releasing calcium, which simultaneously stimulates the release of acetylcholine onto the sarcolemma. As long as calcium and ATP are present, the contraction will continue. Acetylcholine then initiates the resting potential’s change under the motor end plate, stimulates the action potential, and passes along both directions on the surface of the muscle fiber. Sodium ions rush into the cell through the open channels to depolarize the sarcolemma. The depolarization spreads. The potassium channels open while the sodium channels close off, which repolarizes the entire cell. The action potential is dispersed throughout the cell through the transverse tubule, causing the sarcoplasmic reticulum to release
When a chemical signal is transmitted, the presynaptic neuron releases a neurotransmitter into the synapse. The signal is then sent to the postsynaptic neuron. Once the postsynaptic neuron has received the signal, additional neurotransmitter left in the synapse will be reabsorbed by the presynaptic
The pump exchanges three sodium molecules for two potassium molecules. In doing so an electrical gradient is formed across the basolateral membrane of the cell due to the imbalance of charge generated. The interior of the cell is negative by about 80mV in relation to the outside...
Let’s say that there is a mechanical sense. If someone touched your hand, your somatosensory system will detect various stimuli by your skin’s sensory receptors. The sensory information is then conveyed to the central nervous system by afferent neurons. The neuron’s dendrites will pass that information to the cell body, and on to its axon. From there it is passed onto the spinal cord or the brainstem. The neuron's ascending axons will cross to the opposite side either in the spinal cord or in the brainstem. The axons then terminates in the thalamus, and on into the Brodmann Area of the parietal lobe of the brain to process.
Between neurons are small gaps called as synapses which messages can go through, but without electrical impulses. When an impulse reaches a synapse, neurotransmitters are released and move across the gap to the other side for starting the electrical impulse all over again. Then, the neurotransmitter is broken down for new messages to be received.
Dendrites are located on either one or both ends of a cell.The peripheral nervous system then takes the sensory information from the outside and sends the messages by virtue of neurotransmitters. Neurotransmitters are chemicals that relay signals through the neural pathways of the spinal cord. The neurotransmitter chemicals are held by tiny membranous sacs located in the synaptic terminals. Synaptic terminals are located at the ends of nerve cells. The release of neurotransmitters from their sacs is stimulated once the electrical nerve impulse has finished travelling along a neuron and reaches the synaptic terminal. Afterward, neurotransmitters travel across synapses thus stimulating the production of an electrical charge that carries the nerve impulse onward. Synapses are junctions between neighboring neurons. This procedure is reiterated until either muscle movement occurs or the brain picks up on a sensory reaction. During this process, messages are being transmitted from one part of the body onto the next. The peripheral and central nervous system are two crucial subdivisions of the nervous system. The brain and spinal cord make up the central nervous
In their inactive state neurons have a negative potential, called the resting membrane potential. Action potentials changes the transmembrane potential from negative to positive. Action potentials are carried along axons, and are the basis for "information transportation" from one cell in the nervous system to another. Other types of electrical signals are possible, but we'll focus on action potentials. These electrical signals arise from ion fluxes produced by nerve cell membranes that are selectively permeable to different ions.
...ical impulse, repeating the mechanism described above. The neurons received signal, they crumble up the information passed it down until they get to the last one.
The neuron plays an important role in the occupation of the brain (Rollin Koscis). A neuron is...
As the human body goes through different experiences, the brain grows, develops, and changes according to the environmental situations it has been exposed to. Some of these factors include drugs, stress, hormones, diets, and sensory stimuli. [1] Neuroplasticity can be defined as the ability of the nervous system to respond to natural and abnormal stimuli experienced by the human body. The nervous system then reorganizes the brain’s structure and changes some of its function to theoretically repair itself by forming new neurons. [2] Neuroplasticity can occur during and in response to many different situations that occur throughout life. Some examples of these situations are learning, diseases, and going through therapy after an injury.
Synaptic transmission is the process of the communication of neurons. Communication between neurons and communication between neuron and muscle occurs at a specialized junction called synapses. The most common type of synapse is the chemical synapse. Synaptic transmission begins when the nerve impulse or action potential reaches the presynaptic axon terminal. The action potential causes depolarization of the presynaptic membrane and it will initiate the sequence of events leading to release the neurotransmitter and then, the neurotransmitter attaches to the receptor at the postsynaptic membrane and it will lead to the activation of the postsynaptic membrane and continue to send the impulse to other neurons or sending the signal to the muscle for contraction (Breedlove, Watson, & Rosenzweig, 2012; Barnes, 2013).
Biology The brain consists of both neurons and glia cells. The neurons, which are cells housed in a cell body called a Soma, have branches which extend from them, referred to as dendrites. From these dendrites extend axons which send and receive impulses, ending at junction points called synapses. It is at these synapse points that the transfer of information takes place. At the heart of neuroplasticity is the idea of synaptic pruning.
Within the human anatomy, an intricate and complex network of specialised nerve fibres and neurons works in collaboration with the central nervous system and peripheral system, designed to carry out the various actions humans perform every day. The nervous system is also known as the master control unit of the human body, as it operates other major functions such as the circulatory and respiratory systems (Jakab, 2006). It is composed of the central nervous system (CNS) and the peripheral nervous system (PNS). The neurons established within the various sections of the nervous system, is structured with three main parts: a dendrite which is a cluster of branches that operates by receiving information from the receptor and neurons and transferring nerve impulses to the cell body; furthermore, a cell body is composed of a nucleus, that works to provide energy and nutrients for the neuron; lastly is an axon, electrically conducted by the myelin sheath, the axon is a pathway nerve impulses pass through from the cell body. In addition, this is the process in which nerve impulses travel by to be able to access the rest of the system (Core Science, 2010). The correct function of the nervous system is vital to the daily survival of an individual, as it obtains a significant role in the control and co-ordination of the human body. Furthermore, if a situation occurs where the nervous system dysfunctions or develops a disease (such as multiple sclerosis), it would in that case threaten the current status of one’s health and cause havoc in the system.
[online] Available at: http://www.livescience.com/22665-nervous system.html [Accessed: 1 Oct 2013]. Reece, J. 2012. The. Campbell biology. San Francisco, CA. -.
The most basic elements of a neural network, the artificial neurons, are modeled after the neurons of the brain. The "real" neuron is composed of four parts: the dendrites, soma, axon, and the synapse. The dendrites receive input from other neuron's synapses, the soma processes the information received, the axon carries the action potential which fires the neuron when a threshold is breached, and the synapse is where the neuron sends its output, which are in the form of neurotransmitters, to the dendrites of other neurons. Each neuron in the human brain can connect with up to 200,000 other neurons. The power and processing of the human brain comes from multitude of these basic components and the many thousands of connections between them.