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Zoology, lecture 19
Vertebrates: Nervous system
| Question | Answer |
|---|---|
| How many control systems are there in the vertebrate body? | Two--Nervous system and hormonal system |
| Nervous system | Composed of brains found in the skull connected to a network of nerves that branch throughout the body. |
| Central nervous system | Brains and spinal cord. |
| Peripheral nervous system | Everything that branches from the central nervous system to the rest of the body. |
| Sensory nerves | םיתשוחת Nerves in the body that bring information from the periphery into the central nervous system. The information is senses. They allow for smelling/hearing/feeling etc. |
| Motory nerves | םייתעונת Nerves that carry information fro the central nervous system to other parts of the body (the periphery). Not just in control of movement--also in control of other bodily functions. |
| Hormonal system | The endocrine system is composed of glands that secrete chemicals and function within the organs. Secretion is into the circulatory system and distribution is general. They function at points where they have receptors. |
| Endocrine secretion | Secretes into the circulatory system. |
| What are the two types of hormones | Derivatives of amino acids/proteins, and steroids that are based on compound rings. |
| Advantages of the nervous system | It can control every part of the body (cause the nerves reach every spot) and it functions quickly. |
| Disadvantage of the nervous system | Requires the development of a very complex nerve web. Also if you want a continuous signal you have to constantly send the signal. |
| Advantage of the nervous system | Took advantage of the already existing circulatory system to control the body |
| Disadvantages of the nervous system | Once it releases a signal it no longer has control over it. It also doesn't control which regions the signal reaches. |
| Embryonic development of the nervous system | The first system that is prominent in embryonic development produced during neurulation. During gastrulation the notochord produced by the central mesoderm causes the sinking of the ectoderm above it producing a primary neural groove. |
| Primary structure of the nervous system in embryonic development | It's just a tube formed from ectoderm that closes in on itself producing a tube along the length of the body initially open but later closes at the front and back. |
| Amphioxus nervous development | The hollow dorsal nerve tube stops at the stage that it is a continuous tube along the length of the body. |
| Higher chordate nervous system development | The mesodermal notochord formation causes the sinking of the ectoderm producing a valley that closes in on itself to form the nerve chord. The dorso-lateral corners of the tube before it closes pop off and they are called the neural crest. |
| Neural canal | The initial canal that sinks in to form the neural tube. |
| Neural crest | The tips of the neural canal that closed to form the neural tube then detach. These cells have developed migration capabilities and are important in the development of other components in the body. |
| What is the structure of the lower chordate nervous system? | Just a simple neural tube with no brains |
| How does the neural tube seal itself? | It zips starting from the middle going backwards and forwards. |
| What is the structure of the cyclostoma nervous system? | Like the lower chordates they have the neural tube but they also develop expanded pockets that develop into 3 brains. |
| What is the structure of the fish brain? | They start like the cyclostoma but their frontal and rear brains split forming a total of five brains. |
| What are the five brains and in which group do they start to appear? | Cerebrum, diencephalon, mesencephalon, cerebellum, medulla oblongata and they continue down into the spinal cord. All of the cerebrospinal fluid is common. |
| Cerebrospinal fluid CSF | Liquid that is common to the brains and the spinal cord. |
| What is the germ layer origin of the brains? | The brains and the spinal cord start as ectoderm but the sclerotome provides wrapping both for the spine and the brains. |
| How many covers do cyclostoma have on their brains? | Just one (origin is mesodermal sclerotome) |
| What happens to the notochord in higher vertebrates? | It disappears and the sclerotome that formed the vertebrae grows upwards and covers the nerve cord protecting it for the entire length. |
| What happens during the development of the neural crest? | Segmentation takes place and the cells of the neural crest produce two masses in each segment producing spinal ganglia |
| Spinal ganglia | A pair of masses that develop from the migration of the neural crest cells. They sit right up against the spinal cord. When the vetebra develops the ganglia stay inside the bone. |
| Neural crest cell migration | Some form masses in the spinal vertebrae called spinal ganglia, some migrate just outside forming the sympathetic nervous system (not segmental) and some migrate much further to organs forming the parasympathetic nervous system. |
| Continued development of the nerve cord | The ectodermal walls get thicker on the inside and on the outside resulting in a thick walled tube of ectoderm with a narrow canal in the center. |
| Differentiation in the spinal cord | Cells either become neurons (nerve cells) or neuroglia (cells that support/protect neurons). |
| Neuroglia | Most of the nervous system cells become neuroglia--cells that support the neurons--of which there are numerous types |
| Astrocytes | Type of neuroglia that functions in filtering of the substances that enter the brain. |
| Blood brain barrier | Substances in the blood stream don't reach the spinal fluid because of the selective barrier put up by the astrocytes (a type of filtering neuroglia) |
| Oligodendrocytes | Type of neuroglia that function in protecting and supporting the brain cells and covering them in myelin |
| Myelin | An electrically insulating material that covers cell axons in the brain. It is made by the oligodendrocytes. |
| Microglia | Cells of the neuroglia that are very small and function in phagocytosis to clean the system. |
| Ependyma | Cells of neuroglia that cover the main canal of the spinal column. |
| Neuron characteristics | Neurons are cells with numerous extensions (one of which is especially long) |
| Dendrites | Neuron extension that brings the sensation from the tissue towards the cell body. |
| Axon | Neuron extension that brings the sensation from the cell body to the tissue. |
| Synapse | The place where the nerve cell extension connects to the tissue. |
| How do nervous messages transfer down to tissues? | The nerve cell has an extension that goes all the way from the spinal cord to the different body parts. The message is NOT transferred through synapses to other neural cells and then to the tissue. |
| Neural crest cells along the neuron extensions | They migrate and sit along the axons/dendrites in order to protect them (cause they have to go a long distance and be protected). |
| Neural crest protection of nerve extensions | They sit on the axon/dendrite and form spirals forming the myelin protective cover that is made of numerous schwann cells. |
| Schwann cells | Cells that originated in the neural crest and cover the nerve cells insulating them and therefore increasing the speed of message transfer by allowing the electrical signal to jump from intersection to intersection instead of continuous travel. |
| Bipolar nerve cells | Cells with one axon and one dendrite. |
| Multipolar nerve cell | Nerve cell with one axon and multiple dendrites |
| How is the message transferred from the synapse to the tissue? | Through chemical signal that is transferred from the synapse to the muscle. |
| Presynaptic bulb | Bulbs in nerve cell that contain chemical signals. They reach the synapse and jump to the tissue transferring the signal. |
| Functional Neuron differentiation | Some are sensory, some are motory. |
| Somatosensory cells | Cells that transfer messages from the limbs, or senses |
| Viscerosensory cells | Cells that transfer messages from internal parts to the nervous system (stomach ache, heart, uterus etc) |
| Somatomotory cells | Nerve cells that control functions like moving running etc. |
| Visceromotory cells | Nerve cells that give commands that are autonomic. |
| What do the wanted/autonomic nervous systems apply to? | Only to the motor functions. You will feel something whether you want to or not. Motor functions that are autonomic are internal functions like breathing etc. Wanted functions are running. |
| What is the arrangement of the neurons/nerve cells in the brain/spine? | The cell bodies are located in the center of the cord and the neural extensions are located around them. They are arranged in a butterfly shape. |
| Gray matter | The cell bodies of neurons that arrange in a butterfly structure in the center of the spinal column/brains. |
| What is the arrangement of the migration of nerve cells in their final arrangement in the spinal column? | The cell bodies are in the center and the motor neurons migrate to the ventral side with the sensory neurons closer to the dorsal side. |
| What is the arrangement of the neurons in each segment? | There is a pair of sensory and a pair of motor neurons in each segment. Each is paired and reach each body part together (more efficient than producing two networks). |
| Sensory SS VS | Dorsal concentration |
| Motor SM VM | Ventral concentration |
| Reflex network | Nerve function that goes straight from the sensory to the motor without passing through the brain first. It goes to the brain too but it makes the reflex function first. |
| Synapse development through the lifetime | Though cells disappear every day, synapses are formed every day. |
| Meninges | Layers that cover the brain that develop from the sclerotome. There are 3 layers in higher vertebrates. |
| Synapse development through the lifetime | Though cells disappear every day, synapses are formed every day. |
| Piamater | The internal first layer of meninges that covers the brain. It first appears in cyclostoma and up. (amphioxus have no brain!) |
| Duramater | The very hard second layer of meninges that covers the piamater and first shows up in fish. |
| Arachnoid | The spiderweb-like middle layer that develops between the piamater and duramater layers in vertebrates above the fish. |
| Sympathetic ganglia | Develop from the neural crest cells near the vertebrae but they are not segmental. |
| Autonomic (parasympathetic) ganglia | Migrate to further reaches of the body including the organs. Their origins are still in the neural crest. |
| What's the difference between the sympathetic and parasympathetic nervous system? | They are both part of the visceromotory system!! Sympathetic extensions leave from the chest and trunk (thoracolumbar) whereas parasympathetic leave from the brain and from the bottom (sacrum)--craniosacral. |
| Craniosacral nerves | The parasympathetic nerves that are part of the visceromotory system--called this cause they leave from the brain and the bottom of the spinal cord. |
| Thoracolumbar nerves | Nerves that make up the sympathetic nervous system that is part of the visceromotory system--called this cause they leave from the chest and trunk area of the spine. |
| What is the placement of ganglia in the sympathetic nervous system? | The sympathetic are close to the spine sending long extensions to different parts giving you a preganglian extension (short) and a long postganglian extension that goes to the organ. |
| Ganglia in the parasympathetic system | They are far from the spinal column meaning that there is a long preganglian extension and a short postganglian extension to the tissue. |
| Parasympathetic extension color | covered in myelin and therefore look white |
| Sympathetic extension color | Not covered in myelin and therefore look gray |
| Neurotransmitters | They each have two (to the ganglia, from the ganglia) in both the preganglia they secrete acetyl choline but in the post ganglial, parasympathetic continues with acetyl choline, sympathetic releases neuroadrenalin. |
| What is the consequence of the difference in postganglial neurotransmitters between the sympathetic and parasympathetic nervous systems? | The neuroadrenalin produced by the sympathetic nervous system has a different function raising heart rate, contraction of blood vessels whereas acetylcholine results in relaxation. |
| Antagonistic nervous systems | The sympathetic nervous system produces stimulated actions whereas the parasympathetic leads to common function. |
| When does sympathetic function | In stress states--it results in faster heart beats and a less functional digestive system (less absorption) |
Created by:
YaelNoa
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