Physio/Sensation Senior Assesment
Which part of the neuron transmits information?
Axon
Describe the difference between efferent and afferent nerve fibers.
15. The Efferent (motor) nervous system consists of all the nerve pathways carrying signals OUT of the brain and/or spinal cord.
Be familiar with the different brain structures and their 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 including sex, emotional reactions such as anger and fear. Consequently it inspires aversive cues, such as sweaty palms, and has recently been associated with a range of mental conditions including depression to even autism. It is larger in male brains, often enlarged in the brains of sociopaths and it shrinks in the elderly. BRAIN STEM: The part of the brain that connects to the spinal cord. The brain stem controls functions basic to the survival of all animals, such as heart rate, breathing, digesting foods, and sleeping. It is the lowest, most primitive area of the human brain. CEREBELLUM: Two peach-size mounds of folded tissue located at the top of the brain stem, the cerebellum is the guru of skilled, coordinated movement (e.g., returning a tennis serve or throwing a slider down and in) and is involved in some learning pathways. CEREBRUM: This is the largest brain structure in humans and accounts for about two-thirds of the brain's mass. It is divided into two sides — the left and right hemispheres—that are separated by a deep groove down the center from the back of the brain to the forehead. These two halves are connected by long neuron branches called the corpuscallosum which is relatively larger in women's brains than in men's. The cerebrum is positioned over and around most other brain structures, and its four lobes are specialized by function but are richly connected. The outer 3 millimeters of "gray matter" is the cerebral cortex which consists of closely packed neurons that control most of our body functions, including the mysterious state of consciousness, the senses, the body's motor skills, reasoning and language. The Frontal Lobe is the most recently-evolved part of the brain and the last to develop in young adulthood. Its dorso-lateral 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, and guides behavior with verbal skills and houses working memory. Its orbit frontal circuit manages emotional impulses in socially appropriate ways for productive behaviors including empathy, altruism, and interpretation of facial expressions. Stroke in this area typically releases foul language and fatuous behavior patterns. 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 mid-brain structures up to the cerebrum, and, conversely, from the cerebrum down the spinal cord to the nervous system.
Describe the function of an agonist.
An agonist is a chemical that binds to a receptor and activates the receptor to produce a biological response. Whereas an agonist causes an action,
What is the function of inhibitory post synaptic potentials?
An inhibitory postsynaptic potential (IPSP) is a kind of synaptic potential that makes a postsynaptic neuron less likely to generate a potential. The opposite of an inhibitory postsynaptic potential is an Excitatory postsynaptic potential (EPSP), which is a synaptic potential that makes a postsynaptic neuron more likely to generate an action potential. They can take place at all chemical synapses which use the secretion of neurotransmitters to create cell to cell signaling. Inhibitory presynaptic neurons release neurotransmitters which then bind to the postsynaptic receptors; this induces a postsynaptic conductance change as ion channels open or close. An electrical current is generated which changes the postsynaptic membrane potential to create a more negative postsynaptic potential. Depolarization can also occur due to an IPSP if the reverse potential is between the resting threshold and the action potential threshold. Another way to look at inhibitory postsynaptic potentials is that they are also a chloride conductance change in the neuronal cell because it decreases the driving Force. Microelectrodes can be used to measure postsynaptic potentials at either excitatory or inhibitory synapses. In general, a postsynaptic potential is dependent on the type and combination of receptor channel, reverse potential of the postsynaptic potential, action potential threshold voltage, ionic permeability of the ion channel, as well as the concentrations of the ions in and out of the cell; this determines if it is excitatory or inhibitory. IPSPs always want to keep the membrane potential more negative than the action potential threshold and can be seen as a "transient hyper polarization". EPSPs and IPSPs compete with each other at numerous synapses of a neuron; this determines whether or not the action potential at the presynaptic terminal will regenerate at the postsynaptic membrane. Some common neurotransmitters involved in IPSPs are GABA and glycine.
Which part of the neuron receives information?
Dendrites
What is the function of the myelin sheath?
Myelin is a dielectric (electrically insulating) material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. It is an outgrowth of a type of glial cell. The Myelin Sheath has several functions within the body. Its three main functions include: protection of the nerve fiber, insulation of the nerve fiber and increasing the rate of conduction of nerve impulses. The Myelin Sheath is usually located around the axons of certain neurons. makes white matter white/
Describe the functions of different neurotransmitters.
Neurotransmitters can be classified by function: Excitatory neurotransmitters: These types of neurotransmitters have excitatory effects on the neuron; they increase the likelihood that the neuron will fire an action potential. Some of the major excitatory neurotransmitters include epinephrine and Norepinephrine. ***Inhibitory neurotransmitters: These types of neurotransmitters have inhibitory effects on the neuron; they decrease the likelihood that the neuron will fire an action potential. Some of the major inhibitory neurotransmitters include serotonin and GABA
What are the roles of the nervous system and subsystems, including central and peripheral nervous systems, somatic and autonomic nervous systems, and the sympathetic and parasympathetic nervous systems?
The Nervous System is an anatomical system that consists of neurons and nerves that is responsible for visceral regulation, sensory perception, and controlling actions, such as movement. Central Nervous System (CNS): includes the brain and spinal cord. Peripheral Nervous System (PNS): the nerves that make the movements and control the internal organs. The Somatic Nervous System is responsible for coordinating the body's movements, and also for receiving external stimuli. It is the system that regulates activities that are under conscious control. It controls from the esophag to stomach, small intestine and colon. The Autonomic Nervous System makes the functions that do not need consciousness like heart beat, some digestion functions like that of the pancreas, the control of adrenaline and noradrenaline, among others. It is divided in two: Sympathetic: it stimulates organs ** Parasympathetic: it inhibits organs ***The Peripheral Nervous System is divided into two sub-systems. The Somatic Nervous System - primary function is to regulate the actions of the skeletal muscles. Often thought of as mediating voluntary activity. The other sub-system, called the Autonomic Nervous System, regulates primarily involuntary activity such as heart rate, breathing, blood pressure, and digestion. Although these activities are considered involuntary, they can be altered either through specific events or through changing our perceptions about a specific experience. This system is further broken down into two complimentary systems: Sympathetic and Parasympathetic Nervous Systems. The Sympathetic Nervous System controls what has been called the "Fight or Flight" phenomenon because of its control over the necessary bodily changes needed when we are faced with a situation where we may need to defend ourselves or escape. The Parasympathetic Nervous System kicks in. This system is slow acting, unlike its counterpart, and may take several minutes or even longer to get your body back to where it was before the scare.
What is the function of glial cells?
The central nervous system consists of neurons and glial cells. Neurons constitute about half the volume of the CNS and glial cells make up the rest. Glial cells provide support and protection for neurons. They are thus known as the "supporting cells" of the nervous system. The four main functions of glial cells are: to surround neurons and hold them in place, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and to destroy and remove the carcasses of dead neurons (clean up). The three types of CNS supporting cells are Astrocytes,Oligodendrocytes, and Microglia. The supporting cells of the PNS are known as Schwann Cells.
What is action potential?
The change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell. An action potential occurs when a neuron sends information down an axon, away from the cell body. The action potential occurs as a result of a stimulus to the neuron this means that some event (a stimulus) causes the resting potential to move toward 0 mV when a neuron is not sending a signal; it is "at rest." This is called a resting potential. When a neuron is at rest, the inside of the neuron is negative relative to the outside Action potentials are caused by an exchange of ions across the neuron membrane. A stimulus first causes sodium channels to open. Because there are many more sodium ions on the outside, and the inside of the neuron is negative relative to the outside, sodium ions rush into the neuron. Remember, sodium has a positive charge, so the neuron becomes more positive and becomes depolarized. It takes longer for potassium channels to open. When they do open, potassium rushes out of the cell, reversing the depolarization. Also at about this time, sodium channels start to close. This causes the action potential to go back toward -70 mV (a repolarization).
What is resting potential?
The electrical potential of a neuron or other excitable cell relative to its surroundings when not stimulated or involved in passage of an impulse. When a neuron is not sending a signal, it is "at rest." When a neuron is at rest, the inside of the neuron is negative relative to the outside. Although the concentrations of the different ions attempt to balance out on both sides of the membrane, they cannot because the cell membrane allows only some ions to pass through channels (ion channels). At rest, potassium ions (K+) can cross through the membrane easily. Also at rest, chloride ions (Cl-) and sodium ions (Na+) have a more difficult time crossing. The negatively charged protein molecules (A-) inside the neuron cannot cross the membrane. In addition to these selective ion channels, there is a pump that uses energy to move three sodium ions out of the neuron for every two potassium ions it puts in. Finally, when all these forces balance out, and the difference in the voltage between the inside and outside of the neuron is measured, you have the resting potential. The resting membrane potential of a neuron is about -70 mV (mV=millivolt) - this means that the inside of the neuron is 70 mV less than the outside. At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron.
Describe the neruons action potential as it ravels through the neuron. What does it travel along?
Why does an action potential travel down an axon? The basic unit of nerve transmission is the action potential. An action potential is a brief electrical signal that travels along an axon at great speed. The action potential is a rapid change in the relative ion concentrations on either side of the cellular membrane and a rapid return to the original concentrations. The change in ion concentration is called a depolarization of the membrane. The transmission of the action potential is caused by three properties of the system. The depolarization spreads to adjacent areas, the depolarization is self-correcting, and during the recovery period depolarization cannot re-occur. Therefore when an action potential starts it triggers further depolarization but only in the direction along the axon in which depolarization has not already occurred.
How are neurontransmitters recycled between neurons?
With the help of a new method, neuroscientists have now discovered that neurons systematically recycle the protein components necessary for transmitter release and in this way guarantee the reliability of signal transmission in the brain. Neurons communicate via chemical transmitters which they store in the bubble-like synaptic vesicles and release as required. To be able to react reliably to stimulation, neurons must have a certain number of "acutely releasable" vesicles. If this process is disrupted, the communication between the neurons quickly comes to a standstill and vital processes that rely on the rapid transmission of information, for example seeing or the instant identification of a sound source, become impossible to carry out. Neurons transmit signals to each other via specialized contacts known as synapses. When a transmitting neuron is excited, it releases chemical transmitters that are discharged by tiny membrane-enclosed vesicles and then reach the recipient cell. The release of the transmitters is carried out through the fusion of the vesicles with the cell membrane -- a process that requires the interaction of different protein components in the cell. Before the transmitter vesicles can fuse with the neuronal membrane they must first be transformed into an active state. The corresponding biochemical process is referred to as priming. During this process, a structure known as a SNARE complex is constructed from protein components that are required for the rapid fusion of the vesicles with the cell membrane.
Describe the all or none law.
a principle that states that the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus. If a stimulus is above a certain threshold, a nerve or muscle fiber will fire. Essentially, there will either be a full response or there will be no response at all.
Describe the function of an antagonist.
an antagonist blocks the action of the agonist **** antagonists have affinity but no efficacy for their cognate receptors, and binding will disrupt the interaction and inhibit the function of an agonist or inverse agonist at receptors. Antagonists mediate their effects by binding to the active (orthostatic = right place) site or to allosteric (= other place) sites on receptors, or they may interact at unique binding sites not normally involved in the biological regulation of the receptor's activity. Antagonist activity may be reversible or irreversible depending on the longevity of the antagonist-receptor complex, which, in turn, depends on the nature of antagonist-receptor binding.
