Biology 30 Chapter 13: Nervous System - PDF

Biology 30 Unit A: Nervous and Endocrine Systems Chapter 13 - Nervous System The Nervous system will be covering the following key learning ideas 1. describe the general structure and function of a neuron and myelin sheath, explaining the formation and transmission of an action potential, including all-or-none response and intensity of response; the transmission of a signal across a synapse; and the main chemicals and transmitters involved, i.e., norepinephrine, acetylcholine and cholinesterase 2. identify the principal structures of the central and peripheral nervous systems and explain their functions in regulating the voluntary (somatic) and involuntary (autonomic) systems of the human organism; i.e., cerebral hemispheres and lobes, cerebellum, pons, medulla oblongata, hypothalamus, spinal cord, sympathetic and parasympathetic nervous systems, and the sensory-somatic nervous system 3. describe, using an example, the organization of neurons into nerves and the composition and function of reﬂex arcs; e.g., the patellar reﬂex, the pupillary reﬂex A detailed list of the course outcomes has been provided to you with your day one materials, and can be found on the google classroom Next few Days 01 CNS / PNS 02 Nerve Cells and Microscopes Bodily organization of information, brain and spinal How to work with a cord composition , somatic microscope, calculate and autonomic functions ﬁndings, how a nerve cell is organized 03 Action Potential 04 Quiz A Summation of the chapter How nerve cells communicate 13 course material information, reﬂex arcs, synapses, and chemical transmitters How to Succeed Biology 30 is a bulky course. There is an immense amount of material to cover, for this reason it is suggested that students make it a nightly routine to read their textbook and review their notes. There is an outcome list posted to the google classroom with everything that the curriculum expects you to learn A general timeline to completion of those outcomes, alongside a reading list for each day of the course The powerpoints will be released the day that they are completed in class The Nervous System The nervous system is a highly complicated series of cells and chemicals that communicate information throughout the body. It is composed of both electrical impulses and multiple chemicals, neurotransmitters, and hormones - This requires an obscene amount of memorization. Divisions The Nervous system is divided into two primary groups The Central nervous System - CNS The Peripheral nervous system - PNS The central nervous system consists of your brain and your spinal cord. The Peripheral nervous system consists of the nerves that carry information between the organs of the body and the central nervous system. Systems CNS PNS Coordinates the body. Controls all mechanical All other parts of the and chemical actions; nervous system, excluding made up of the brain the brain and the spinal and the spinal cord cord, that relay information between the central nervou system and the other parts of the body. Going Futher PNS The PNS can further be divided into subgroups that serve different functions Somatic System Autonomic System The somatic system is the voluntary The Autonomic system is akin to the idea of an automatic system. The Autonomic system nervous system. The Somatic System controls internal organs, and reﬂexes - Things controls muscle movements, skeletal we do not actively think about, or do voluntarily. tissues, skin, and sensory inputs. Remember these We are going to brieﬂy depart from these systems as we are going to need some deeper structural knowledge to go further, however, as we continue consider how the information can be classiﬁed into CNS, PNS, Somatic, and Autonomic Nerve Cell Structures Nerve cells are categorized into two types Neurons The fundamental functional units of the nervous system. Neurons conduct electric current Glial Cells Non conductive cells that both structural support and metabolis for other nerve cells throughout the body to convey and process information Neurons Dendrite All Neurons contain Dendrites, Cell Bodies, and axons. The Dendrite receives stimulus, or information. This can come as sensory information from the environment or a signal from a neighboring neurons. You may want to make a copy of this diagram in your notes Neurons Cell Body The Cell Body houses the Nucleus; dendrites conduct the incoming signal towards the cell body where the signal is then redirected. The Cell body is similar to most other cells in that it is a housing, containing cytoplasm and the nucleus. You may want to make a copy of this diagram in your notes Neurons The Axon The axon directs signal away from the cell body towards a target organ/muscle or to another neuron. Each Neuron has only one axon, BUT the axon can divide and branch to many different terminus’ Axons are thin and very delicate, 100 human axons can ﬁt into a single human hair. You may want to make a copy of this diagram in your notes The terminals that axons end at are called effectors. Vocabulary Neurons, nerve Cells and Nerves all carry different meanings. A Neuron is a Nerve cell, a Nerve Cell could be a Neuron, or a Glial cell, and a nerve is a bundle of multiple neurons. The nerve is best thought of like a ﬁbre optic wire. Many neurons are bundled together to send large volumes of information. Fun Fact* Mr. Button can't spell Neuron right ever. Neurons The Myelin Sheath The Myelin Sheath is a coating of fatty white protein that covers the axon. The Myelin sheath insulates the axon. The process of covering cells with myelin is called myelination. The myelination of a cell is caused by a special glial cell called a Schwann cell. The insulation serves to prevent the loss of charged ions from the nerve cell. The area between the schwann cells is You may want to make a copy of this diagram called the Node of ranvier in your notes Neuron The nodes of Ranvier As a nerve impulse travels it leaps from one node to the next. This leaping effect accelerates the transmission of information. Unsurprisingly, myelinated axons transmit impulses much faster than unmyelinated cells. Size also plays a role in the speed of nerve transmission Neurilemma All nerve ﬁbres found within the peripheral nervous system have a thin outer membrane called the neurilemma. Neurilemma is also formed by schwann cells and facilitates the regeneration of damaged axons. Because of the relationship between neurilemma and myelin we call the ﬁbres in the brain that are myelinated white matter, for the white appearance. Fun Fact* Im talking to your nerves right now Important All nerve ﬁbres found in the PNS are myelinated and have neurilemma. Not all nerve ﬁbres in the CNS contain myelin and neurilemma. These nerves are called gray matter, as they have a grayish appearance. The absence of neurilemma in parts of the CNS lead to many injuries to the brain and spine being permanent. -- Check in -- What are the divisions of the nervous system What are the key parts of the neuron What is the difference between neurons and nerves What is the difference between somatic and autonomic nerves What are the two functions of the Glial Cell What are Schwann cells and what do they do What is Neurillemma, what does it do, where is it located? Application Question Multiple Sclerosis is a disease that affects normal transmission of impulses in the brain and spinal cord, often slowing them down. This causes symptoms of double vision, jerky movements, and speech difﬁculty. What component of the neuron is most likely affected? Talk it through with a partner - then we will discuss how to break down the information A. The myelin sheath, it hardens to a scar like tissue and inhibits transmission. Categories of Neurons 1. Sensory 2. Interneurons 3. Motor Neurons Sensory Neurons relay Interneurons exist in Motor Neurons relay information from a the CNS to transmit information to sensory receptors information from one effectors. about the environment group of neurons to to the CNS for the next. Effectors tell a cell, processing. organ, or muscle to Interneurons interpret respond to the Sensory Neurons tend information and stimulus. to cluster around the communicate spinal cord in groupings impulses to the motor Muscles, organs, and called ganglia neurons. glands are all (ganglion for one) classiﬁed as effectors. Sometimes called Sometimes they are associated neurons Motor neurons are called Afferent neurons sometimes called efferent neurons. Big Question Why does the Central nervous system not support nerve growth the way that the PNS does? As it turns out there is a glial limiting membrane in the CNS, that reduces the growth of schwann cells. No Schwann cells means no myelin and no neurilemma Consider why the CNS may opt not to develop myelin, and where myelin is present. This will become important in time Reﬂex Arc So consider you just touch a screaming hot pot or pan on the stove, you are likely not thinking about what your nervous system is telling you before reacting; You are reacting and then thinking about the information your hand has provided you with. Reﬂex Arc The reﬂex arc is a specialized pathway within the body to rapidly respond to dangerous stimulus. A reﬂex arc communicates the information about the danger directly to the effector, as it may take too long for the information to reach the CNS and instigate a voluntary response. The information is sent to both the effector and the CNS, but the effector will react well before the brain can process the stimuli. Why you react and ﬂinch well before you feel the In a reﬂex arc the signal is sent directly to the effector, and subsequently to pain of heat, or something sharp. the CNS for processing Reﬂex Arc Testing a reﬂex arc is a great way to test to overall health of the nervous system. There may be something wrong if the interneuron is not effectively transmitting the signal to the CNS, or the effector in a timely fashion. Above: The patellar Reﬂex arc. This can be tested at any time, have a friend lightly impact the area between the knee cap and shin bone. There should be a swift involuntary kick. A few Questions If your reﬂexes do not properly respond how can you tell which neurons are not working properly Would the reﬂex arc be the somatic or autonomic system Where is Gray and white matter located, What is the difference between gray and white matter. Is there a relationship between impulse speed and axon size? Work Time Learning through lecture, discussion, and presentation is excellent! However The brain does not encode without proper practice and use of information; for this reason there will be dedicated time to work and utilize your knowledge. This time slot is dedicated to one of the following - Developing ﬂashcards - Working through question booklets - Reading your textbook / answering textbook questions 404 - 414 Electrochemical Impulses Alright; we have been talking at length about how nerves and neurons transmit information and even alluded to the use of electricity being behind the transfer. Buckle up, we are going to learn how these impulses take place. Electrochemical Impulses We know that nerves communicate by electrochemical messages created by the movement of ions through the nerve cell membrane. Experimental evidence: When an electrode was implanted in a large nerve cell of a squid, there was a rapid change in the electrical potential difference - commonly called the potential - across the membrane. The membrane at rest measured -70mV, however at excited state measured at +40 mV Action potential This term describes the process of the electronegativity of a cell changing rapidly when stimulated. Action Potential The reversal of the cell electronegativity from its resting Resting potential potential to a positive electrical When the cell membrane returns to potential. its original -70mV electric potential The two diﬀerent states are diﬀerence sometimes lumped into one term. Resting potential The outer membrane of most cells is -70mV, in a neuron we call this resting potential Critical thinking: How can we generate a negative potential on the inside of a cell membrane? Ion Imbalance All cells in the human body have a ready supply of potassium ions (K+) and Sodium ions (Na+) By placing a higher concentration of one ion on one side of the cell membrane than the other we can create an electrical imbalance at the cell wall. This is the same as creating any form of imbalance by separating charges. - even though both of the charges are the same, there is a still a net charge across the membrane to restore balance. What is where? Inside the Cell Outside the cell Inside the cell at rest there Outside the cell is an area of concentrated there are K+ ions substantially more Na+ ions Due to the imbalance the potassium ions wish to The high imbalance leave the cell. means that the sodium wants to The future movement of the potassium ion is where enter the cell the electric discharge is attributed to. Keeping things in place Our cell walls are made up of a phospholipid bilayer, wherein the plasma membrane is only selectively permeable to ions at speciﬁc sites. This keeps the ions separated until chosen to move, the ions move via facilitated diffusion, passing through gated ion channels that span the bilayer. Ion channels are speciﬁc to each ion. equilibrium If given enough time, the cell would return to electric equilibrium, for this reason all cells contain a sodium/potassium pump that utilizes active transport to move potassium back into the cell and sodium back out. This pump works opposite to the diffusion gradient Creating Imbalance So far we have described the locality and imbalance of ions but not of the electrical potential. There is a large sum of negative ions already within a given cell. When the potassium leaves it generates a negative potential; the sodium entering attempts to balance this; however due to the limited rate of diffusion the membrane remains at a resting negative potential. Action potential The positive ions align with the exterior of the cell, while the excess negative ions accumulate on the inner wall. This diﬀerence creates a polarized membrane. The value -70mV denotes the diﬀerence between internal and external ion concentrations, the greater the number, the greater the diﬀerence. Outside ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -------------------------------------------------------------------------------------------------- Inside Action Potential Stimulus Concentration Depolarization When the neuron The Sodium ions that The overall process is receives stimulus, desperately want called depolarization as the cell membrane equilibrium ﬂood the we are no longer at a becomes more cell. resting potential with a 1 permeable to 3 5 polarized membrane sodium ions 2 4 Gate changes Charge Reversal To facilitate the Because of the rapid ﬂood of permeability change the sodium, the charge inside the cell sodium gates open and becomes positive, making the outer the potassium gates close surface of the membrane negatively charged. Action Potential To the left is a graph depicting an action potential; every action potential graph will contain the same key features. A rest potential A depolarization A repolarization And a hyperpolarization Resting potential As described earlier, the rest potential is the electric state by which the cell is polarized and ready to receive stimulus Although this graph does not show it, it is generally at -70mV Depolarization The upward trend represents depolarization. When stimulus is received, the sodium channels open and potassium channels close, and the electric potential difference rapidly becomes positive. Repolarization The Downward trend the follows is called repolarization. Once the cell becomes internally positively charged the sodium gates are shut. The potassium gates reopen and the natural diffusion begins to return to resting potential Hyperpolarization In the effort to return to equilibrium the potassium gates remain open longer than they should, and the outside becomes more positively charge, and the inside more negatively charged than the ordinary resting potential. Momentarily the potential is more negative than it should be. Restoring equilibrium The sodium potassium pump uses active transport to return the electric potential to resting potential. It does this by by returning potassium ions in, and sodium ions out of the cell. Refractory Period The cell action potential cannot ﬁre a second time until the cell returns to its resting potential. The time between ﬁring and returning to resting potential is roughly 1-10ms - which is astonishingly fast. CREDITS: This presentation template was created by Slidesgo, including icons by Flaticon, and infographics & images by Freepik. Please keep this slide for attribution. Movement of Action Potential Purpose of Depolarization Domino Eﬀect Hyperpolarization The huge shift in The hyperpolarized That electrical electronegativity point in the action disturbance causes a along the cellular potential forces the depolarization event at membrane creates electrical disturbance the adjacent part of the an electrical to travel in only one membrane. direction. disturbance along the cell. Causing another An action potential depolarization can only take place after the refractory period, and thus the disturbances only affect the leading edge of the signal Saltatory conduction Only in Myelinated In myelinated axons, the depolarization is isolated to the nodes of ranvier. Because of this the signal is forced to “jump” from node to node. The overall effect is that the wave of depolarization moves much faster. How much faster? Saltatory conduction sends signals at about 150m/s Unmyelinated axons send signals at about 0.5 - 10m/s Soooo.. Like 15 - 300 times faster depending on the axon. All or nothing Response Threshold value Every neuron has a threshold value. This value deﬁnes the minimum amount of stimulus required to warrant a depolarization event taking place. RESULTS Threshold values are different depending on the TLDR neuron or the animal, but each neuron has a response If the stimulus is not strong enough - nothing happens. Experimental Evidence A muscle tissue sample was isolated and subjected to electrical impulses of varying strength and then measured for its force of contraction. What 2 conclusions can be drawn from the data below. Stimulus Force 1mV 0 2mV 3N 3mV 3N 10mV 3N The all or nothing response A neuron only ﬁres when the threshold stimuli is met. Once the threshold has been crossed it will ﬁre with the same speed, and intensity. A higher input stimuli does not warrant a unique response. The neuron ﬁres either ﬁre to the absolute max, or not at all. Paradox If a neuron ﬁres at the same rate how can the brain differentiate between differences in stimuli. How do we tell the difference between warm and hot, and stubbed toe and a broken one? Provide a plausible hypothesis The all or nothing response Solution 1: Rates Solution 2: Types One solution to this apparent A second solution is variable paradox is to consider the rate at threshold values. which the impulses are being ﬁred. Consider that perhaps some If the impulse is being received by neurons will only depolarize if the brain rapidly, and the burned at 20C while others won't depolarizing rate is as fast as it will depolarize until 50C go, the brain will interpret this differently than if the impulses are Our body can now differentiate more casually depolarizing. between the two temperatures and their unique danger levels. Ex. text rate in an emergency A few Questions How does a neuron ﬁre an impulse How does saltatory conduction increase the speed of transmission What is the all or nothing response How can the brain tell different stimuli apart What is the purpose of the sodium-potassium ion pump What is active transport What is diffusion Which side of the membrane is negative at resting potential What is a threshold stimulus What ion starts inside/outside a cell at resting potential What happens at the end of an axon? We have now discussed the function of the neuron, and the way in which an electrical impulse travels, however what happens at the end of an axon? How does a neuron transfer information to the next neuron or effector in sequence? The answer is synaptic transmission. End of an Axon The Axon Terminal Synapses Sometimes referred to as the Synapses are the connection at the synaptic knob, axons end in a end of an axon terminal. terminal that connects to other components of the nervous system. Synapses use chemicals called neurotransmitters to propagate The connection may be between information from the axon terminal neurons or a neuron and an effector. to the effector or next dendrite Though rarely is the connection ecvlusively 2 neurons. Synapse The Diagram to the left illustrates the connection between two neurons. The presynaptic neuron propagates an electric signal stimulating the neurotransmitters to release to the next postsynaptic neuron Synapse The electric signal at the end plate triggers a Ca2+ channel that allows calcium into the synapse. Ca2+ triggers vesicles to release neurotransmitters across the synapse - into the synaptic cleft. The neurotransmitters are received by a specialized receptor that when stimulated will depolarize the postsynaptic membrane and propagate a new electrochemical signal. Synapse What is the speed of a synapse Synapses require diffusion across a space of approximately 20nm. Is diffusion of a chemical substance going to be faster or slower than the propagation of electrochemical impulse facilitated by saltatory conduction. Think about whether it is faster or slower, and why evolutionarily a body would choose to use this process. Answer: Slower than impulse, diffusion of neurotransmitters signiﬁcantly slows the process of signal transmission. More synapses in a path means slow signal. Neurotransmitters. Neurotransmitters are a classiﬁcation of chemical that alter the membrane potentials of post synaptic neurons. Neurotransmitters are classiﬁed into two primary groups; excitory and inhibitory. The confusing component is that many neurotransmitters can act in either category depending on the locality within the body Neurotransmitters Excitatory Inhibitory An excitatory neurotransmitter is a An inhibitory neurotransmitter acts chemical that opens the sodium in much the same way as an channels in a postsynaptic neuron. excitatory; though for the opposite ion. The opening of these channels depolarizes the membrane and Inhibitory neurotransmitters further initiated a new reversal of charge, open a potassium channel further and subsequently a new impulse. reinforcing the negative potential in the cellular membrane. This prevents an impulse from being sent. Problem Once a neurotransmitter has bonded with a neuroreceptor wouldnt the affected channel be permanently open? This would mean that once a synapse ﬁres it would never be able to ﬁre again - this would be bad. Propose a solution A solution - enzymes The body has a series of enzymes that facilitate the reuptake of neurotransmitters. After a neurotransmitter is released the presynaptic neuron releases these specialized enzymes to either absorb or destroy the neurotransmitter and close the open channel in the postsynaptic neuron. Acetylcholine Acetylcholine is common neurotransmitter that you will be expected to know by memory. Acetylcholine is generally found in the end plates of many nerve cells and is generally excitatory to skeletal and muscle tissues. Can be inhibitory in other localities; as it is found in both the CNS and PNS being used for neuromuscular functions. Cholinesterase Cholinesterase is the enzyme that pairs with acetylcholine, destroying it within the receptor site. You can tell enzymes as they end in a “ase” sufﬁx. Enzymes function by having very speciﬁc shapes that only bind to unique compounds in a highly speciﬁc orientation. Below shows a basic diagram Of how acetylcholine can be Dismantled into two non binding chemicals A quick review Electric impulses end at a synapse The synapse releases a neurotransmitter The neurotransmitter changes the membrane permeability to a speciﬁc ion This either initiates a new impulse or prevents one from taking place An enzyme is then released to destroy or absorb the neurotransmitter ending its effect on the receiving synapse. Summation The body uses a process called summation to inhibit or allow certain neurons to only ﬁre in particular cases. The diagram to the right shows a few ways the body differentiates signal strength and meaning using summation Summation Spatial Summation Temporal Summation Sometimes in order to create a In other cases a synapse may neurochemical impulse the require a presynaptic neuron to ﬁre postsynaptic neuron will require two multiple times in quick succession to or more synapses to ﬁre generate sufﬁcient permeability to simultaneously. create a new neurochemical impulse. If only one ﬁres in this case it will not elicit a response in the postsynaptic neuron In either case an inhibitory neurotransmitter may also be ﬁred to prevent an excitatory neurotransmitter; all in the name of speciﬁc communication. A few other neurotransmitters Neurotransmitter Action Secretion Site Major Effects Dopamine Generally CNS, PNS Voluntary movement/ emotions excitatory Norepinephrine Excititory or CNS, PNS Wakefulness Inhibitory Seratonin Generally CNS Sleep inhibitory GABA (gamma - inhibitory CNS Motor behaviour aminobutyric acid) For your consideration Drugs, whether pharmaceutical or illicit can cause effects on the nervous system. In many cases drugs will mimic the shape and function of neurotransmitters. Consider how a inhibitor or an excitatory neurotransmitter could instigate a disruption in the nervous system. Consider a positive and negative way this could impact your bodies function. Drugs continued Stimulants Depressant Drugs that are a stimulant can do A depressant can do the following one of three things - Block a receptor site from a - Mimic a neurotransmitter, and neurotransmitter stimulate a receptor - Decrease the creation and - Decrease the breakdown of secretion of a neurotransmitter neurotransmitters, causing a - Increase the breakdown rate of buildup of neurotransmitter a neurotransmitter - Increase the rate of release of neurotransmitters from the presynaptic neuron For more information on drug effects on your body please review pages 423 and 444 in the text Central nervous system Now that we know more about the way the system works let's return to the larger organizations of the system. The brain and the skull The brain is the ﬁrst component of the CNS and the primary coordinating centre of all information in the body. The brain is covered in a three layer protective membrane known as meninges. There is also a ﬂuid layer that ﬂows between the three layers called the cerebrospinal ﬂuid that both absorbs shocks, and transport nutrients throughout the brain. Sometimes samples of cerebrospinal ﬂuid are taken to look for viral/bacterial infection like meningitis. The Spinal cord The Spinal Cord carries sensory nerve messages from receptors to the brain - it is the bodily information superhighway. The spinal cord is located in the backbone (different things) The spinal cord contains white matter and gray matter. The white matter runs up and down to and from the brain, while the grey matter makes up the interneurons associated with the peripheral nervous system, sensory neurons, motor neurons and general body function. Brain Structure The brain as we know it divide certain processing functions to unique physiological localities within it. Experimental evidence: During open brain surgeries to test the function of the brain, an awake patient would be asked questions and observed while neurosurgeons would poke and prod at different parts of the brain. This lead to the conclusion that coordination of different functions was based on the location of neurons. The Cerebrum The Cerebrum is the foremost part of the brain. It is divided into two hemispheres that act independently as the major coordinating center of the brain. Sensory information, and accompanying motor function originates from this area as well as speech, reasoning, memory and personality. The surface of the cerebrum is called the cerebral cortex, and is composed of grey matter, and is covered in deep cerebral ﬁssures Lobes The brain is divided into 4 main lobes based on the unique processes in each locality. Each lobe is documented once more via the process of stimulating regions with electric probes to ﬁnd out what they do. Did you know: It requires many more neurons to control ﬁnger, thumb and wrist movements than arm, leg and foot movements. Why might this be? Frontal Lobe The frontal lobe controls voluntary movement of muscles. The frontal lobe is alos believed to be where personality, reasoning, and decision making take place. It also controls inhibition, aspects of memory, and is considered to be the area that active thought takes place in. The frontal lobe is very likely where “you” exist. But that has more to do with philosophy than Bio 30. Temporal Lobe The Temporal lobe is associated with vision and hearing. Associated areas are linked with memory and interpretation of sensory information. Fun Fact: Often in alzheimer's patients, and those with memory/dementia that music can unlock portions of memory. Could you draw a link to why this may be? Parietal Lobe Sensory areas are associated with touch and temperature awareness. The parietal lobe is linked to the emotions and interpreting speech, speciﬁcally speech. Why might these two things be linked together in the same lobe; remember form follows function. Occipital Lobe Sensory areas associated with all things vision. Processing, and interpreting vision both take place here. Consider its location, why might your vision be blurry when you fall on ice? Why would this lobe be located here? Cerebellum The cerebellum is the largest section of the “hindbrain” (back of brain) It controls limb movements, balance, and muscle tone. While the frontol lobe controls overall movements, the cerebellum ﬁne tunes those movements, controlling balance and the unique combination of inhibitory and excitatory responses required to execute actions. It also controls “limb awareness” Brain Communication The brain’s left and right hemispheres operate independently. The right side is associated with the tasks of visual patterns, and spatial awareness; the left is associated with the verbal skills. Learning abilities are thought to be related to the dominance of one hemisphere or the other, however their ability to communicate is key. Corpus Callosum The corpus callosum is the large bundle of nerve ﬁbres that connects the two hemispheres of the brain together, allowing communication between the two hemispheres. What would you expect the neuron composition of this part of the brain to look like? Each hemisphere is also though to coordinate the opposite side of the body, right controlling left and vice versa. Corpus Callosum Further Subdivisions of the brain The forebrain The midbrain The Hindbrain The forebrain As discussed in the The midbrain consists contains the earlier slides the of four spheres of grey structure called the hindbrain is in the matter, the midbrain thalamus, posterior of the brain. acts as a relay centre hypothalamus and for some eye and ear It contains the the olfactory bulb reﬂexes structures: cerebellum, pons, and medulla oblongata. Thalamus / Hypothalamus The Thalamus acts as a relay station directing incoming signals throughout the brain to their processing zone. The Hypothalamus is a small part of the brain that controls equilibrium; things like body temperature, eating and drinking. The hypothalamus having a direct link with the pituitary gland also gives the brain control over the endocrine system (later) Olfactory bulb The olfactory bulb is located at the bottom of the temporal lobe. It is responsible for processing information about smell. Consider its location in conjunction with its function. Pons The pons is located in the hindbrain, and the name literally means bridge. The pons acts as a relay station between he medulla and the cerebellum. The medulla oblongata The nerve tracks in the spine and higher brain function run through the medulla; this acts as a connection between the PNS, and the CNS. The medulla controls involuntary muscle action, like breathing, blinking, heartrate, diameter of blood vessels. It follows that this structure acts as a coordinating center for the autonomic nervous system. Contrary to popular belief, it has nothing to do with alligator aggression Give your medulla a break, you are now in control of your own breathing rate....sorry... Peripheral Nervous System Now that we have taken a deep dive into the CNS, let us revisit the PNS in detail. The Sensory Somatic System This system gathers information about the environment for the CNS, and transports instructions to the skeletal muscles. This system is generally considered voluntary as we control how we process our environments, and how we interact with them. The unique case with the sensory somatic is reﬂex arcs; although we do not control them directly they are considered under the sensory somatic Sensory Somatic This system Composed of 12 cranial nerves, and 31 pairs of spinal nerves. Some are sensory, others motor, and some do both. Collectively these nerves make up and control our vision, hearing, balance, taste, smell, facial and tongue movements, head muscular movements, and more. The spinal nerves innervate the movement of the body, and all our conscious thought and awareness operate in this system 12 Cranial Nerves We do not need to have each of these nerves memorized on function, however a few of them we should be able to understand just with our Biology vocabulary knowledge. The Autonomic System As we learned earlier in the course, the autonomic nervous system controls involuntary bodily functions. An example is our breathing cycle. We rarely are consciously controlling it, rather our body monitors the blood oxygen level, and should it drop too low, our body increases the breathing and heart rate seamlessly. The Autonomic System This system acts through a series of dedicated nerves that carry signals and information about the body’s internal environment. The nerves in the Autonomic system are unique as they have two groupings of motor neurons separated by a ganglion This system will control smooth muscle groups, which include cardiac muscle, internal organs, and glands. This system gets differentiated into two further subcategories based on stress impulse and the size of the pre/postganglionic nerves present. The sympathetic and parasympathetic. Autonomic System Sympathetic Parasympathetic. The Sympathetic nervous system is The parasympathetic nervous system designed to mitigate stress. is designed to cope with the stresses your body is put under. An example of the sympathetic system would be your adrenaline An example of the parasympathetic function. system is the storage of glucose, and decrease of blood ﬂow Quick you see a bear! - The sympathetic nervous system After your brush in with a bear, you releases chemicals that prepare ﬁnd your heart rate slower - your your body for combat, or ﬂight. stomach hungery, and your breathing relaxed, this is your parasympathetic system calming you Autonomic System System Organ Sympathetic Response Parasympathetic checks Response The chart to the Heart Increased Heart Rate Decreased Heart Rate right, contains sympathetic and Digestive Tract Decreased peristalsis Increases peristalsis parasympathetic system responses liver Increase glucose release Glucose storage rate in your body based on organs. Eyes Dilated pupils Constricted pupils Bladder Relaxes sphincter Constricts sphincter Skin Increased blood flow Decreased blood flow Adrenal gland Releases epinephrine No effect Pre/Post Ganglionic Length Sympathetic Parasympathetic. The sympathetic system differs from The parasympathetic nervous the parasympathetic in how it system uses a long preganglionic connects to the ganglia in the neuron and a short postganglionic autonomic system. neuron The sympathetic system uses a short preganglionic motor neuron There is a really great diagram on and a long postganglionic neuron page 434 about this. Pre/Post Ganglionic Length Neurotransmitters Both systems use the neurotransmitter acetylcholine in the preganglionic motor neuron. However the sympathetic system uses norepinephrine, while the parasympathetic system uses acetylcholine and nitric oxide. Why might these two separate systems use different neurotransmitters at the effector site? How might pharmaceuticals be able to target speciﬁc needs using this understanding. Shared nerve The cranial Vagus nerve, is shared between the sympathetic and parasympathetic system. It may be in our best interest to know that vagus means wandering, and this nerve does wander throughout the body. Branches of the vagus nerve innervate the heart, bronchi of the lungs, liver, pancreas, and digestive tract. Readings You have reached the end of Chapter 13 Ensure you have read through to page - 435 Once caught up there ensure you review using the chapter summary and review questions on 436 - 443 HEALTH ICONS HEALTH ICONS ALTERNATIVE RESOURCES

Biology 30 Chapter 13: Nervous System - PDF

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