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Nervous System By: Daniel Aleynick What does it do? Responsibilities: Receive signal Interpret signal Send signal to do an action The Nervous System control most of the actions your body performs Organization of Nervous System Nervous System: Central Nervous System (CNS): Consists of the brain and spinal cord. Peripheral Nervous System (PNS): Are the nerves that connect the CNS to the rest of the body Information Processing A sensor (example: eye or skin) picks up a signal, which is sends to the brain. The CNS processes the information, and sends another signal to a specific effector (example: muscle) Effector proceeds with an action, such as a movement. Neuron Structure Composed of: Cell Body Dendrites Axon Synaptic terminals Supporting Cells Supporting cells are known as Glia. Astrocytes: provide support for neurons and control concentration of ion levels The blood-brain barrier is formed by astrocytes creating a very tightly controlled extracelluar chemical environment. Radial Glia: Form tracks that newly formed neurons can travel. Also act as stems cells and can generated new neurons. Astrocytes Surrporting Cells Con’t Schwann Cells: They make up the myelin sheath which covers the axon of neurons. They act as an insulator and increase the speed of the action potentials. Resting Potential Membrane potential: The electrical difference between the inside and outside of a cell. Resting potential: The membrane potential when a cell is not transmitting a signal. Membrane Potential Gated Ion Channels There are three types ion channels: Stretch-gated ion channels Ligand-gated ion channels Voltage-gated ion channels Voltage and Lignad Ion Channels Voltage-gated Ion Channels: Are found in axons and open and close when the membrane potential changes. Stretch-gated Ion Channels: Open and close when the cells sense it is being stretch. This occurs when the cell becomes mechanically deformed. Ligand-gated Ion Channels Ligand-gated Ion Channels: Are ion channels that open and close when a specific molecule binds to the channel. This molecule is usually a neurotransmitter. Action Potential Useful Terms Hyperpolarization: An increase of the magnitude of membrane potential by becoming more negative. This is caused by K+ channels to opening up. Depolarization: A reducation in the magnitude of membrane potential. This occurred when Na+ channels open up. The changes in the membrane potential are called graded potentials. Production of Action Potentials Action Potentials What is an action potential? An action potential is a stimulus strong enough to produce depolarization past the threshold The threshold is the membrane potential limit that must be reached for an action to occur. This is a all or nothing event so nothing occur unless the limit is reached. Once reached, the whole action takes place. Conduction of Action Potentials An action potential starts in the axon hillock. From there a cascade effect takes place: As the axon hillock is depolarized, it depolarizes a neighboring region of axon membrane. This next region than depolarizes another nearby region until the action potential reaches the synaptic terminals Conduction Speed The faster the body can send out signals, the faster one can react. But how does the body increase the speed of conduction? The axon of some neurons is covered by Schwann cells. Since these cells are made from lipids, they are insulators. This causes the electrical signal to jump over the Schwann cells increase the speed of the signal. This is known as salutatory conduction. Neuron Communication A neuron pass a signal to another neuron by chemical synapses. Synaptic terminals produce a neurotransmitter and package then in synaptic vesicles. The neurotransmitter move across the synaptic cleft and active the ligand-gated ion channels on the nearby neuron. Neurotransmitters Acetylcholine: Is one of the most common neurotransmitters. Functional Class: Is an excitatory in vertebrate skeletal muscles and an inhibitory at other sites. It is secreted by the CNS, PNS, and neuromuscular junctions. Neurotransmitters Con’t The next group of neurotransmitters are the Biogenic Amines: Norepinephrine: Can be an excitatory or inhibitory and is produced in the CNS and PNS Dopamine: Is both an excitatory and inhibitory and is produced in the CNS and PNS Serotonin: Is generally a inhibitory and is produced by the CNS Neurotransmitters Con’t Amino Acids can also be used as neurotransmitters: Gamma Aminobutyric Acid: Is an inhibitory and is made in the CNS and neuromuscular junctions. Glycine: It is an inhibitory neurotransmitter and is created in the CNS Glutamate: Is an excitatory and is produced in the CNS and neuromuscular junction. Aspartate: An excitatory that is made in the CNS Neurotransmitters Final The last group of major neurotransmitters are Neuropeptides: Substance P (not a creative name): is an excitatory that is produce in both the CNS and PNS Met-enkephalin: Is generally an inhibitory that is made in the CNS Gases as Neurotransmitters Gases can be dissolved in fluids of the body and used as neurotransmitters as well. Common examples are: NO and CO Regions of the Nervous System The peripheral nervous system is made up of all the nerves connect the brain and spine to the rest of the body Cranial nerves extend from the brain and spread to organs of the head and upper body Spinal Nerves originate in the spinal cord and extend to parts of the body below the head. PNS The PNS can be divided into two functional components: The Somatic Nervous System (SNS) The Autonomic Nervous System (ANS) The Autonomic Nervous System can then be divided further into 3 more division Sympathetic division Parasympathetic division Enteric division Somatic Nervous System Is considered voluntary because it is subject to conscious control. Sends signals to and from the skeletal muscles of the body. ANS: Sympathetic The sympathetic division deals with arousal and energy generation of the body The “Fight or Flight” response: Digestions stops Energy production increases Adrenaline is released Faster Heart Rate Adrenaline RUSH ANS: Parasympathetic Self-maintenance functions known as “Rest and Digest” Digetionenchanced Heart Rated Slowed Glycogen production Resting and Digesting ANS: Enteric Division Is a network of neurons in the digestive tract, pancreas and gallbladder. They control the secretions and smooth muscle activities of the body, such as peristalsis, the uncontrolled movement of food through the body. Brain Structure In adults the brain consists of 5 structures: Cerebrum Dienceohalon Midbrain Cerebellum Medulla Oblongata Cerebrum Is divided into two different regions The Right Cerebral Hemisphere The Left Cerebral Hemisphere Each Hemisphere has an other cover of gray brain matter and an inner region, the cerebral cortex, that is white brain matter. Basal Nuclei are groups of neurons in the cerebrum that are centers for planning and learning movement A think band of axons known as the corpus callosum always the right and left hemisphere to communicate. Diencephalon Is divided into 3 regions: The Epithalamus The Thalamus The Hypothalamus The Epithalamus consists of the pineal gland and choroid plexus that produces cerebrospinal fluid. The Thalamus is the sensory center. All incoming information from sense is sorted here The Hypothalamus produced vital hormones and is the body’s thermostat, control temperature as well as hunger, thirst, and other survival mechanisms. Midbrain Acts as the rely stations for all auditory and visual information that brain receives. It also controls the eyes and how they move Cerebellum The cerebellum is important for coordination and error checking during motor, perceptual, and cognitive functions Is responsible for handeye coordination and balance. Good way to remember its function is “Cerebalance”. Medulla Oblongata Is the control central for some of the most vital body processes It controls automatic and homeostatic functions such as: Breathing Heart Beats Blood Vessel Activity Swallowing Vomiting Digestion Circadian Rhythms The biological clock of the body controlling cycles such as the sleep/wake cycle Uses cues from the environment to change cycles. Examples of cues are light intensity and hunger. Paired up with the hypothalamic structures call the Superchiasmatic nuclei, clusters of neurons in the CNS. Laterlization During brain development, different function segregate to either the left or the right cerebral hemisphere The Left side is more adept to language, math, logical operations, etc The Right side is stronger at pattern recognition, nonverbal thinking and emotion processes. Left side is factual information while right side is creativity. Memory and Learning The body is constantly making connection between what is happening to what has already happen. Short-term Memory is stored in the frontal lobe and are memories of what has recently happened. When these memories become irrelevant, the brain forgets them. Long-term Memory is aided by the hippocampus. These are short-term memories that were stored for later use. The more a memory is used the easier it is to remember, hence practice makes perfect Disease/Nervous Problems Schizophrenia: A mental disturbance where the patient can no longer distinguish between reality and imagination. Bipolar Disorder: Involves swings of mood from high to low and affects 1% of the population Alzheimer's Disease: Mental deterioration which results in confusion, memory loss, and other variable symptoms. Usually the results of old age