Nervous System

How does the size of the brain correspond to the body weight of an organism?

As the body gets bigger in weight so does the brain.

The PNS can be divided into two components. What are they and how do they differ from each other?

Somatic and autonomic systems of PNS. Somatic system contains nerves that carry sensory information to CNS and nerves that carry motor signals from the CNS to skeletal muscles. This is involved with voluntary movement. Brain to finger impulse to press keys to type is by way of somatic nervous system. THe autonomic nervous system is the involuntary nervous system and is involved with regulating internal environment of the body. It carries signals from organs to CNS and from the CNS to internal organs. WOrks with things such as heartbeat and digestion.

What is the role of the axon hillock?

THe axon hillock is the last part of a neuron's cell body before it goes into the axon. So when an action potential reaches the dendrite and is passing down to the axon hillock it will do it job by pushing the action potentials farther down into the axon where it will continue to the next neuron.

Describe the basic components of the vertebrate brain with help of a drawing. Briefly describe the function of each part of the brain.

diagram in docs

Explain the structure of the spinal cord. What is white matter? Gray matter?

31 pairs of spinal nerves rising from spinal cord. Each has two roots, ventral and dorsal root. Pairs of spinal nerves are grouped into positions on spinal cord. They are seperated into 8 cervical, 12 thoracic, 5 lumbar, 5 sacrial and 1 cocogial discs. Internal structures contain white and grey matter. Grey matter consists of motor neurons. Grey matter is surrounded by white matter which contains nerve fibers that connect the PNS to the CNS.

Explain the events that occur as an action potential moves along the membrane. How does the action potential propagate itself?

An action potential starts at an axon hillock and propagates away towards the synapse the axon ends at. from there it causes depolarization through contact with the next axon dendrite or soma of another neuron or itself. look at diagram in docs

Use a sea anemone to describe the basic structure and function of a nerve net. What kind of advantages does the nerve net give the organism?

Basic function of a nerve net is for the sea anemone to respond to its environment to be able to sense food as well as danger. The function is also the advantage because without this function they would be as simple as a sponge just filter feeding and staying in one spot. With the nerve net some can escape from predators as well as actively consume food and sense any physical contact. Also a nerve net is less taxing than our nervous system, so less energy requirements is an advantage.

What is the difference between the CNS and the PNS? Describe each part of these components of a vertebrate nervous system.

CNS coordinates all processes happening in the body and is placed in the dorsal cavity of animals, PNS is found outside the CNS and is not protected by anything and exposed to injury. CNS handles involuntary information while PNS handles voluntary information. Function of CNS is to process and gather information. PNS job is to integrate information gathered from CNS. PNS responsible for all movement of info into sensory, inter, and motor neurons. CNS consists of brain and spine. PNS is outside of those structures and connects to organs and limbs.

In animal biology we often discuss the concept of cephalization. What does cephalization refer to?

Cephalization refers to the centralization of a brain region in bilaterally symmetrical animals to their head region.

Explain the structure of a nerve? How does a nerve differ from a neuron?

Each nerve is a cord like structure with bundles of axons and protected by connective tissue. Groups of neurons are a nerve, a single cell is a neuron. Neurons are only sensory or motor, while nerves are afferent, efferent, and mixed. Nerves are found in PNS and are its primary structure., neurons are found in CNS as well as PNS. Nerves transmit information to parts of the body, neurons conduct nerve impulses. Nerve damage can lead to things such as carpal tunnel while neuron damage leads to things such as alzheimer's.

Describe the evolution of the nervous system beginning in invertebrates.

First eukaryotic cells have a brain cell for processing surroundings. Cnidarians then evolve a nerve net that works with their radial symmetry and is distributed throughout the whole body, they don't have many requirements so it only needs a simple system. Then Echinoderms (starfish) were the first to have a centralized nerve ring with radial nerves that extend to each arm, these are the first signs of a central nervous region. FLatworms then develop bilateral symmetry and through cephalization develop a brain in the head region with nerve cords going down the body for more efficient movement and sensing. The annelids and arthropods then have a brain a ventral nerve cords, like a noodle spine for more efficient use. The arthropods also have a segmented ganglia so each segment of the body has more distinct nerve endings that help to better control the body as well as sensing and responding.

Does the magnitude and the frequency of action potentials vary? Why or why not?

Frequency of the action potential may vary depending on the pathway that's being acted on. A higher frequency means a faster response and low frequency means a slow response. The magnitude of the action potential stays the same and can only be either turned on or off in an all or nothing type of response. This is because if an action potential is not reached it will not turn on, a certain threshold must be broken in order for it to proceed.

How do these different parts differ from each other as one compares fishes, amphibians, reptiles, birds and mammals?

In the evolution of vertebrates from fish to mammals, the most significant changes have occurred in the structure of the brain. Even in the earliest vertebrates, the brain had three divisions: the hindbrain, midbrain, and forebrain. In fish, the hindbrain is dominant and concerned mainly with motor reflexes. The largest section of the fish brain is the optic lobes in the midbrain, with the anterior of the brain (forebrain) composed of the olfactory lobes and the cerebrum. In the progression from fish to mammals, the hindbrain becomes less and less prominent, and the area of the brain used for receiving and integrating information becomes greater and greater as shown by an increase in the size and development of the cerebrum. The cerebrum is the part of the brain involved in learning voluntary movement as well as the interpretation of sensation. Birds and mammals have the largest brain mass relative to body size with the largest ratio found in man and porpoises. In man the brain weighs approximately 3 lb (1.4 kg) with the cerebrum making up 80% of the total brain mass.

Summarize: briefly describe the evolution of the nervous system in animals with an emphasis on the vertebrates.

In the evolution of vertebrates from fish to mammals, the most significant changes have occurred in the structure of the brain. Even in the earliest vertebrates, the brain had three divisions: the hindbrain, midbrain, and forebrain. In fish, the hindbrain is dominant and concerned mainly with motor reflexes. The largest section of the fish brain is the optic lobes in the midbrain, with the anterior of the brain (forebrain) composed of the olfactory lobes and the cerebrum. In the progression from fish to mammals, the hindbrain becomes less and less prominent, and the area of the brain used for receiving and integrating information becomes greater and greater as shown by an increase in the size and development of the cerebrum. The cerebrum is the part of the brain involved in learning voluntary movement as well as the interpretation of sensation. Birds and mammals have the largest brain mass relative to body size with the largest ratio found in man and porpoises. In man the brain weighs approximately 3 lb (1.4 kg) with the cerebrum making up 80% of the total brain mass.

What is the importance of ion channels and membrane proteins relative to the structure of the cell membrane as one tries to explain the concept of a membrane potential?

Ion channels and membrane proteins are the mechanisms that allow the electrical equilibrium between positive and negative cells to be disrupted causing an action potential. There are special pumps that work with ions to keep a balance, when a cell is at rest it is a negative energy potential (-70 mV) inside the cell and a higher positive energy potential outside the cell. This is because there is a high concentration of sodium outside the cell. When an action potential threshold is reached the sodium pump allows sodium to enter the cell making it positive and allowing the action potential to work.

What is the importance of understanding that there are many different types of neurotransmitters?

It is important to know which neurons perform which action. NT's can be described as inhibitory or excitatory. When an inhibitory NT such as serotonin or GABA get transported they are there to stop signals from firing and keep things under control. When an excitatory NT such as dopamine gets pushed along it tells the neurons to keep firing. Each group performs unique activities as well. Dopamine can be involved with attention, problem solving and memory while serotonin is involved in sleeping, pain control, and digestion.

What is an action potential? What kind of attributes does it have? What purpose does it serve?

It is the electrical impulse that gets passed from one neuron to the next. Action potentials are how we sense and perceive everything in the world. Every action potential is our body working to live and interpret what is happening.

What is a membrane potential? How does it form? What is the basis for this potential?

Membrane potential is the difference in electrical potential energy between the inside and outside of a cell. ALl animal cells are composed of a phospholipid bilayer that act as a barrier between the inside and outside of the cell. This is a barrier has proteins that are involved with active and inactive transport of ions across the membrane as well as diffusion of smaller ions straight across the membrane. The membrane potential has two basic functions. First, it allows a cell to function as a battery, providing power to operate a variety of "molecular devices" embedded in the membrane. Second, in electrically excitable cells such as neurons and muscle cells, it is used for transmitting signals between different parts of a cell. Signals are generated by opening or closing of ion channels at one point in the membrane, producing a local change in the membrane potential. This change in the electric field can be quickly affected by either adjacent or more distant ion channels in the membrane. Those ion channels can then open or close as a result of the potential change, reproducing the signal.

What is the function of myelin? How does it form? What happens if myelin is absent?

Myelin is an insulator of axons on a neuron that help to keep action potentials alive when they are received from a dendrite and passed from the axon terminal to another dendrite. Between each myelin there are sodium channels that help to keep the action potentials alive. These myelin are formed by glial cells, and myelin is different in CNS and PNS. Myelin makes up the white part of the brain showing how much myelin an animal can have. Without myelin action potentials cant stay alive and be passed at all, instead of pinching someone and them responding, it would be like pinching a dead body. Multiple Sclerosis is a myelin deficiency disease.

How do neurons connect with each other? How do they signal?

Neurons connect with each other through the dendrites and axons. When a neuron gets an impulse it will send it from its body through its axon then into the connecting neurons dendrite. The electrical impulse in the axon is transferred by neurotransmitters in the synaptic cleft to the next dendrite where the electrical impulse moves on.

Is an increase in brain size unique to humans?

No all animals that grow bigger also contain bigger brains, but the intelligence within the brain vary from size to size and isn't fully understood.

What is the function of a brain in a vertebrate?

Responsible for regulating involuntary bodily functions, muscle movement, consciousness, memory and thought. It uses the most energy of any organ, and the body could not function without the brain.

What is the role of neurotransmitters and receptors in this process?

Role of the neurotransmitters is to take the electrical impulse (action potential) and transfer it as a chemical signal (neurotransmitters) through the protein channel of presynaptic cell to postsynaptic cell where it is then turned into an electrical impulse once again.

What is the basic difference between Schwann cells and oligodendrocytes?

Schwann cells are myelin in the neurons of the PNS while Oligodendrocytes are the myelin of the CNS.

What is the importance of sensory neurons, motor neurons and interneurons?

Sensory neurons are what bring information into our body by being able to see or feel objects. Then sensory information then goes to the brain where interneurons decide what to do with the sensations and how to proceed.The motor neurons are then able to move the body to respond to the interneurons decisions.

What kind of feature in the bauplan in animals favored the evolution of a more complex nervous system? Explain your answer.

THe blueprint of an animal favored a more complex nervous system because the animal has certain needs and these needs have to be met for survival, and as animals keep evolving bigger and faster and as competition rises the animals body needs to be able to keep up by being able to avoid predators with greater speed or adapt a new way to attract mates as well adaptations to catch food. All these requirements can be met by having a more complex nervous system that allows the animals to respond quicker and coordinate its body in various ways that help for survival.

When does the nervous system develop in human?

THe nervous system develops in the embryo around 1 month into pregnancy.

Explain the events that occur in the presynaptic cell's terminal, the synaptic cleft as well as the membrane of the postsynaptic cell as an action potential reaches the terminal.

THe potential moves from cell to cell through neurotransmitters that are pushed from presynaptic cell to postsynaptic cell. THe neurotransmitter live in the ends of the presynaptic cell in small vesicles and when an action potential reaches them they fuse to the end of the cell through proteins that release the NT into the synaptic cleft and the postsynaptic neuron collects these with their proteins to keep response moving through.

How does the potential move from cell to cell?

THe potential moves from cell to cell through neurotransmitters that are pushed from presynaptic cell to postsynaptic cell. THe neurotransmitter live in the ends of the presynaptic cell in small vesicles and when an action potential reaches them they fuse to the end of the cell through proteins that release the NT into the synaptic cleft and the postsynaptic neuron collects these with their proteins to keep response moving through.

Describe the meninges. What is the function of the meninges?

The 3 membranes that surround the brain and spine. THey provide protection and support for the brain as well as containing cerebrospinal fluid. It attached the brain to the skull and the spinal cord to the vertebral column to keep them stable. IT also has openings for the blood to be able to leave the brain.

Discuss the role of the cerebral cortex in human. What kind of functions are associated with the different parts of the cerebral cortex?

The cerebral cortex is the outermost region of the brain and contains grey matter which is folded and wrinkled as well as having 4 lobes: the frontal lobe, parietal lobe, occipital lobe, and temporal lobe. Frontal lobe.

What is the function of the nervous system? What problem is solved?

The function of the nervous system is to respond to your surroundings and take in sensory information. The problem solved here is how do I know what's around me? And then when I know, how will I respond to them? how how efficient will I be?

What is the importance of understanding the differences between the sympathetic and parasympathetic components of the autonomic nervous system?

The sympathetic nerve fibers is used for stimulating energy resources to make body do things while parasympathetic nerves are there to conserve energy. Frightening situation will cause heart to race and blood pressure to increase using the sympathetic system. when eating a meal the peripheral system will cause salvation and help body to digest food in a relaxed state. It's the yin and yang of the body.

What is the importance of a threshold potential?

The threshold potential is important because it is the mechanism that controls and regulates responses in the body, if there was not a threshold the body would constantly be stimulated and that would be fatiguing as well as annoying. It also is a good mechanism for knowing when it needs to push an action potential. Without this people would just be ****ing all the time and punching people in the face.

Describe the reflex response in a vertebrate.

These are immediate unconscious responses to stimuli. The stimulus activates the sensory neurons that go to the spine, and instead of going to the brain first, it goes straight back out to motor neurons to react, this is called a reflex arc. THe brain still get the stimulus to decide what to do with response. There are unconscious reflexes built into us and there are conditioned responses like hearing you have an animal bio test and going to the bathroom to throw up because you have learned that tests suck. A real example might be touching something hot and instantly pulling your hand away.

Describe the parts of the forebrain, midbrain and hindbrain in a human. Briefly describe the parts of each component as well as their function/s.

diagram in docs

Describe the structure of a basic neuron. Draw the cell and label important parts.

diagram in docs

Make a drawing of an action potential as seen on an oscilloscope and link the events from your previous answer to the drawing.

in docs