On pg 83, Shubin discusses the head and its chaotic state with the complexity of the nerves. While head as whole provides many interesting discussions, studying brain bringings up even more possible discussions. Please discuss brain's role in the central nervous system, endocrine system, both, or any others which pertain to our study, and discuss from evolutionary perspective why the developement of the brain is more crucial in more complex organisms as opposed to early, primitive organisms.
Kevin jeon
bboybyung@gmail.com
The brain is one of the two most important parts of the central nervous system. In vertebrates, there are three anterior bulges of the neural tube that become evident as the embryo continues to develop: the forebrain, midbrain, and hindbrain. As embryonic development continues into the 5th week, 5 regions of the brain develop. The three regions derived from the midbrain and hindbrain turn into the brainstem, which forms the lower part of the brain. The region of the forebrain makes up the adult cerebrum.
ReplyDeleteThe brainstem is in charge of homeostasis, coordination of movement and conduction of information to and from different brain centers. An adult brainstem contains a midbrain (pons) and medulla oblongata, which function in transfer of information between the peripheral nervous system and the midbrain/forebrain. The medulla and pons also coordinate larger scale body movements like running or climbing. The midbrain has centers that are specialized in receiving and integrating different types of sensory information and sends coded sensory information to specific regions of the forebrain through neurons. The medulla also has many centers that control some automatic, homeostatic functions like breathing, heart and blood vessel activity, vomiting, swallowing, and digestion. The pons are also responsible for regulating breathing centers in the medulla.
The cerebellum, which is formed from the hindbrain, functions in coordinating movements and balance, receiving sensory information pertaining to joint positions and muscle lengths, as well as auditory and visual input. The cerebellum is responsible for hand-eye coordination and integrates the auditory and visual information while carrying out coordination and error checking during motor and perceptual functions.
The diencephalon, which is the division of the forebrain that evolved the earliest in the history of vertebrates, has developed into three parts: the thalamus, hypothalamus, and epithalamus. The thalamus and hypothalamus are the major integrating centers of the brain which act as relay stations for information flowing through the body. The thalamus is the main input center for sensory information that will go the cerebrum and the hypothalamus is the most important brain region for control of homeostasis.
The cerebrum is the main center for information processing. The cerebrum is divided into two hemispheres which are covered with gray matter and have white matter on the inside. Deep inside the white matter, neurons called the basal nuclei plan and learn movement sequences. If there is a defect in the cerebrum during development, disorders can occur where motor commands issued to muscles can be disrupted.
ReplyDeleteEvolution over millions of years and generations has brought animals very far, with humans having a very complex nervous system and brain. In more complex organisms, a more complex brain is necessary because they face more complex situations in which a brain is necessary to carry out functions depending on the surroundings and the situation. A complex brain is also necessary in order to carry out motor functions and are important in the functions of sensory information. Since more complex organisms have more of a need for more complex and detailed motor functions, like walking, running, swimming, and etc... (for humans), a more complex brain is necessary. Such motor functions can be important in avoiding prey and moving to different environments when the situation is dangerous, which is why having a brain gives humans a selective advantage over many animals. The very complex variety of sensory information that the brain is responsible for is also very important for organisms; for example: the brain is responsible for the automatic reflex humans have when coming in contact with fire. If the brain was not able to detect this through sensory information and immediately send out signals to move the hand away from the fire, then there would be extensive damage to the human. The automatic, homeostatic functions that the brain carries out, such as breathing, digestion, and heart and blood vessel activity, is vital in order for humans and other animals to survive. Because the brain provides these "more complex" organisms with all of these functions, they have a selective advantage over organisms that do not have a complex brain to carry out all of these functions.
Sujin Ko (sujinko93@gmail.com)
Sources: Shubin
Campbell
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CNS.html
After studying the nervous system, we can think of the brain as a central computer that controls all bodily functions, and the nervous system is like a network that relays messages from the brain to different parts of the body. It does this via the spinal cord, which runs from the brain down through the back and contains threadlike nerves that branch out to every organ and body part. When a message comes into the brain from anywhere in the body, the brain tells the body how to react. Using the example where we touch a hot stove, the nerves in your skin shoot a message of pain to your brain. The brain then sends a message back telling the muscles in your hand to pull away.
ReplyDeleteFurthermore,the endocrine system, which is instrumental in regulating mood, growth and development, tissue function, metabolism,sexual function and reproductive processes, is also controlled by the brain. The hypothalamus is the link, in the brain, between the nervous system and the endocrine system via the pituitary gland.
From an evolutionary standpoint, the brain doesn't have to be large for a larger organism, rather it must be more complex. The human brain weighs less than 5 poundsm but controls the most complex functions in any organisms. The human brain contains many folds which increase surface area, allowing for less space to be taken up while making it more functional. As seen in our daily lives, no animal can do math, compose songs or drive a car. The daily functions that we as complex organisms perform, involve a brain that is anotomically similiar to primates yet still having more neurons in our brain’s outermost layer. In conclusion, the evolutionary history of brains revolves directly around the functions it had to put out. The function of the brain and other systems it controls directly relates to its structure.
Eryk Fundakowski- arthur2446@comcast.net
http://www.scientificamerican.com/article.cfm?id=intelligence-evolved
http://en.wikipedia.org/wiki/Brain
http://psychology.about.com/od/biopsychology/p/NervousSystem.htm
To start off, the brain is composed of a network of billions of neurons. A neuron is a specialized cell transmitting nerve impulses (dictionary.com). It is composed to multiple essential parts boiled down to three: Dendrites, axon, and axon terminals. The dendrites receive chemical signals from the neurotransmitters sent for the presynaptic neuron; this is a chemical pathway. Once this happens, the message is passed down the axon and to the axon terminals with electrical current, called action potential. This is formed when ion channels are opened and closed. Na+ rushes into the neuron giving it a more positive charge and K+ rushes out later. This continues until it reaches the axon terminals. There, the current allows Ca2+ ions to rush in and allow the vesicles found in the axon terminals to undergo exocytosis, allowing neurotransmitters to enter the next synapse. (Campbell) The action potential travels at the rate of "1.2 to 250 miles per hour!" (http://webspace.ship.edu/cgboer/theneuron.html)
ReplyDeleteThe brain is composed to billions of these inter-connected webs and it makes a complex system. The first one I'm going to talk about is the nervous system. This is separated into the central nervous system (all inter neurons) and the Peripheral nervous system (sensory neurons and motor neurons). Sensory neurons send information to the spinal cord while motor neurons send information away from the spinal cord. Motor neurons then split into the somatic nervous system (voluntary) and the autonomic nervous system (involantary life functions like breaking, heart rate, digestion). And again, the autonomic nervous system breaks down into the parasympathetic (rest and digest) and the sympathetic (fight or flight). http://www.rhsmpsychology.com/Handouts/nervous_system_breakdown.htm
It was evolutionary selective to develop a brain because it does so many actions that make life so much easier. The first form of a brain comes from jellyfish which use it to co-ordinate their movements, so energy is used more efficiently. Later on, worms evolved and they contained a brain that exhibit more complex forms of behavior. "The brain becomes both much larger and still more complex as we move to vertebrates such as fish, amphibians, and reptiles." http://faculty.ed.uiuc.edu/g-cziko/wm/05.html The significance of the brain is that it controls everything that goes on in bodies, whether that is the necessary heart rate or just lifting up your hand to catch a fish. As organisms grew bigger and more complex, the brain had to do more functions to allow it to survive.
Nikhil Pereira (nikhil.pereira3@gmail.com)