All Autonomic impulses are afferent, meaning that they travel from the CNS to the PNS. The ANS can be broken down into two major divisions, the Parasympathetic and the Sympathetic divisions. The Parasympathetic division is responsible for all of the feed-and-breed or rest-and-digest functions of the body and is the restorer of homeostasis. The preganglionic axon is long and the post ganglionic axon is short. The Sympathetic division can be seen as the parasympathetic divisions opposite. The Sympathetic division carries out the fight-or-flight responses in our body. In this division, the preganglionic axon is shot and the post ganglionic axon is long. In both divisions, the target cells are smooth muscle, cardiac muscle and glands. Another commonality is that all preganglionic neurons release Ach and all receptors on the post ganglionic neurons are thus nicotinic.
There are two different categories of receptors for the ANS. Cholinergeric, which includes both Nicotinic and Muscarinic receptors and Adrenergic receptors. Nicotinic receptors always cause excitation or activation and perform as both the receptor and channel. They also only bind Ach. Muscarinic receptors can either cause excitation of inhibition and use either a PKA pathway or a PKC pathway to allow chemicals to enter the neuron. Both pathways utilize G-Proteins. Adrenergic receptors also utilize these pathways and are broken down into a1, a2, b1, b2, b3 receptors. The 1's refer to impulses that cause constriction or contraction and the 2's refer to impulses that cause dilation. B3 is the odd man out and its impulse causes heat production. Muscarinic and Adrenergic receptors are found on the cells of terminal targets.
I understood from lecture that the Adrenal gland, a gland that sits on top of the kidneys, is part of the sympathetic nervous system. This gland produces both epinephrine and norepinepherine by diffusing the hormones into the blood stream. This direct link into the blood stream allows for a fast regulation of the hormone throughout the body. That was as much as I was able to retain from lecture, so I researched a little more on the Internet. I learned that adrenal medulla is the central core of the Adrenal gland. The neurons within it (called Chromaffin cells) produce the hormones that are released into the blood stream instead of producing an impulse as all of the other neurons that we have learned about do. These hormones aid in the fight-or-flight response by increasing blood pressure, metabolic rate and or glucose concentration. The neurons in the Adrenal Medulla also produce dopamine, which low-levels of this hormone has been linked to Parkinson's diseases.
Friday, February 27, 2009
Wednesday, February 18, 2009
Automonic Nervous System
There are two motor neurons in an autonomic motor pathway. The first neuron is called a preganglionic neuron and its cell body is located in the brain or spinal chord. Its axon (very long) leaves the CNS and extends (as part of a spinal or cranial nerve) to an autonomic ganglion. The second neuron is called the post ganglionic neuron and its axon is short. The preganglionic neurons pass along nerve impulses from the CNS to the autonomic ganglia and the postganglionic neurons relay the impulse from the autonomic ganglia to the terminal target, which could be smooth muscle, cardiac muscle or a gland. The neurotransmitter that is released is always excitatory and is always Ach. The #2 neuron always produces an action potential. Wether the terminal target becomes excited depends on its receptors. They are usually cholinergeric and thus are either Nicotinic (excitatory) or muscarinic (inhibitory).
After browsing the internet, I learned that a malfunction in the autonimic system is called autonomic failure and is a result of the imbalance between the sympathetic and parasympathetic divisions of the autonomic nervous system. Signs that there is an imbalance include orthostatic hypotension and postprandial hypotension. These can cause dizzyness or lightheadedness. Elderly people are most likely to suffer from this condition and the drop in blood pressure is usually a result of the onset of a disease (diabetes, stroke) and the medications that are used to treat them. There is no cure for autonomic disorders, however there are medications that can treat the low blood pressure and the uncomfortableness that accompanies the episodes.
After browsing the internet, I learned that a malfunction in the autonimic system is called autonomic failure and is a result of the imbalance between the sympathetic and parasympathetic divisions of the autonomic nervous system. Signs that there is an imbalance include orthostatic hypotension and postprandial hypotension. These can cause dizzyness or lightheadedness. Elderly people are most likely to suffer from this condition and the drop in blood pressure is usually a result of the onset of a disease (diabetes, stroke) and the medications that are used to treat them. There is no cure for autonomic disorders, however there are medications that can treat the low blood pressure and the uncomfortableness that accompanies the episodes.
Sunday, February 8, 2009
The Thalamus and Hypothalamus
All incoming sensory information from periphery is relayed through the thalamus to an appropriate higher processing center. The Thalamus is segregated into several regions each pertaining to its nuclei and associated functions. The Anterior Group is part of the limbic system, the regulator of emotion. The Medial Group integrates sensory information and relays it to the frontal lobes. The Ventral Group is responsible for passing along information from the basal nuclei of the cerebrum and the cerebellum to the somatic motor areas of the cerebral cortex. It also passes along sensory information to the sensory areas of the cerebral cortex. The Posterior Group includes the Pulvinar, and the lateral and medial geniculate nuclei. The function of the Pulvinar is to process sensory information for projection to the cerebral cortex. The lateral geniculate nucleus passes along visual information to the visual cortex and the medial geniculate nuclei passes along auditory information to the auditory cortex. Lastly, the lateral group processes sensory information as well as effects emotional states.
I am particularly intrigued by mood disorders and the effect they have on the brain. I have a relative with Bi-Polar disorder and although I know what the definition is and how it is treated, I did not really understand physiologically how Bi-Polar Disorder interrupts normal brain activity. I learned that through structural imaging studies, scientist have found a decrease in overall brain volume in patients with Bi-Polar Disorder. They believe that this is in part due to the decreased number of neurons and glial cells in layers II and III (are they referring to the meninges?) in the forebrain. They also know that the frontal and temporal lobes, the pre-frontal cortex, basal ganlia and parts of the limbic system are all involved and effected by this disorder. Some scientist also believe that since the cerebral cortex is responsible for some thought process that it may also be involved in the negative thinking that are part of the negative episodes of the disorder. Some websites offered that it was an excess of neurotransmitters that causes the manic episodes and a decrease in neurotransmitters that causes the depressive episodes, while other websites claimed that it was not the amount of neurotransmitters but the "effectiveness of the cell's functioning" that was to blame.
I am particularly intrigued by mood disorders and the effect they have on the brain. I have a relative with Bi-Polar disorder and although I know what the definition is and how it is treated, I did not really understand physiologically how Bi-Polar Disorder interrupts normal brain activity. I learned that through structural imaging studies, scientist have found a decrease in overall brain volume in patients with Bi-Polar Disorder. They believe that this is in part due to the decreased number of neurons and glial cells in layers II and III (are they referring to the meninges?) in the forebrain. They also know that the frontal and temporal lobes, the pre-frontal cortex, basal ganlia and parts of the limbic system are all involved and effected by this disorder. Some scientist also believe that since the cerebral cortex is responsible for some thought process that it may also be involved in the negative thinking that are part of the negative episodes of the disorder. Some websites offered that it was an excess of neurotransmitters that causes the manic episodes and a decrease in neurotransmitters that causes the depressive episodes, while other websites claimed that it was not the amount of neurotransmitters but the "effectiveness of the cell's functioning" that was to blame.
Sunday, January 25, 2009
Ion channels
We learned that there are two different types of ion channels: chemically regulated and voltage regulated. Chemically Regulated Ion Channels open when a Neurotransmitter binds to a receptor in the membrane of the cell. and allow a chemical, such as a Na+ to pass through the membrane. In the case of Ach, the receptor is also the channel. These channels are much slower and much more controlled compared to voltage regulated channels. This is due to the need for each channel to be opened separately when a NT binds to a receptor instead of the gate/door effect for voltage channels. It is more of a trickle than a flood. Voltage Regulated Ion Channels are activated when a certain voltage threshold is reached and then all gates/doors are open and a surge of charge is released.
The topic that intrigued me the most during the lecture was the possibility of using an inhibitor drug to decrease stimulation or sensory information in patients who are hypersensitive to stimuli. At least for those who do not have triggers and for whom continual sensory overload is a problem. My brother is one of these people. He does not have certain tones or sensations that bother him, instead it is the multitude of sensory information that seems to attack him and gets worse in crowded rooms and such. It is though his brain does not have a filter. If it can work for schizophrenics why can't it work for PDD and autistic patients with this problem? Well, I googled and found no answers to my questions. I found sites discussing the use of inhibitors for heart failure and schizophrenia but nothing about its use for sensory integration. I think it is a problem of me knowing just enough to be dangerous.
The topic that intrigued me the most during the lecture was the possibility of using an inhibitor drug to decrease stimulation or sensory information in patients who are hypersensitive to stimuli. At least for those who do not have triggers and for whom continual sensory overload is a problem. My brother is one of these people. He does not have certain tones or sensations that bother him, instead it is the multitude of sensory information that seems to attack him and gets worse in crowded rooms and such. It is though his brain does not have a filter. If it can work for schizophrenics why can't it work for PDD and autistic patients with this problem? Well, I googled and found no answers to my questions. I found sites discussing the use of inhibitors for heart failure and schizophrenia but nothing about its use for sensory integration. I think it is a problem of me knowing just enough to be dangerous.
Saturday, January 17, 2009
The Nervous System
A large portion of our lecture included information on the neuron and how neurons communicate with eachother. A neuron is the fundamental cell of the nervous system and is a transmitter of electro-chemical signals. The neuron moves charged particles or ions from the soma down the axon to the synaptic terminal where it is then turned into a complete chemical signal called a neurotransmitter (protein). Neurons have several functions including to relay sensory information, to receive sensory information, to help maintain homeostasis and to regulate glandular secretions.
During lecture we drew a detailed neuron, which helped to understand how a neuron operates. A neuron contains a cell body//soma//perikaryon, which contains a nucleus and Nissl bodies (dense ribosomes) on which neurotransmitters are produced. Off of the body (in a multipolar neuron) are extensions called dendrites which have receptors embedded in their membranes so that neurotransmitters from other neurons can bind and communicate. This binding creates a change in the membranes permeability and Na+ is allowed to enter. There is also another extension from the body, called an axon, and it is usually longer than the dendrites. There is a region in front of the axon, in the cell body, in which there are no granules called the Axon Hillock. It is here that the Na+ will build up and upon reaching a critical density will diffuse down the axon, where it is moved by synaptic vesicles into synaptic bulbs//synaptic terminals. A massive influx of Na+ causes the permeability to change and Ca+ enters. This rush of Ca+ causes the vesicle to burst allowing the neurotransmitters to move out and make contact with another neurotransmitter. Those neurotransmitters not used will re-enter the synaptic bulbs and be transported back to the cell body where it will be recycled. A neuron can bind with a different neurotransmitter than it produces, but it cannot produce more than one kind of neurotransmitter.
We also discussed the three structural types of neurons; unipolar, bipolar, and multi polar as well as the three types of potential for neurons. Resting potential is an inactive state in which the Na+/K+/ATP pumps in the membrane produce a -70mv across the bilayer by pumping out 3 Na+ and pumping in 2 K+ simultaneously. The second potential known as Graded or local potential is the one that I understand the least. From what I do understand the neuron reaches this potential when the charge is between -70mv and -54 mv. Once the neuron reaches a -55 mv it hits a threshold and moves into Action Potential. In this state, due to the huge change in charge, there is an influx of Na+.
In lecture we briefly discussed the structure of the nervous system, which includes the CNS, which includes the brain and spinal chord, and the PNS, which includes the nerves that travel toward and away from the CNS. These can be broke down into cranial and spinal nerves. The Autonomic system also belongs to the PNS. Along with neurons there are four types of accessory cells called Neuroglia which are part of the nervous tissue as well. Astrocytes work as a screen and stop mutagens from killing neurons, which cannot undergo mitosis. Oligodendrites produce the myelin sheath which is wrapped around Schwann cells that are attached to the axon. The myelin allows the nerve impulse to move quicker and more efficiently. Microglia are the smallest and are an immune system cell that prevents the brain from becoming infected. And lastly there are the Ependymal cells which are the producers of CFS in our brain.
The part of the lecture that I connected with was the part about the astrocytes. These are known to be the most common cells identified in childhood tumors and a close friend's son has just been diagnosed with a brain tumor. He has had several MRI's since developing atypical episodes in which he stops breathing for 1 1/2 minutes and beyond. During these episodes he can respond to stimulation such as pinching but only when severe. Neurologists believed that he had an atypical seizure disorder but after 6 months of no change in his development as well as no changes on several MRIs, they have come to the conclusion that he has an early stage brain tumor. They were able to see a small area in his brain that contained an abnormal gelatinous material and they expect that this will slowly harden and optimistically they may be able to remove it at that time. As far as I know, they do not know the type of cells that make up the tumor, and after listening to your lecture, I am curious to see if they are in fact Astrocytes.
During lecture we drew a detailed neuron, which helped to understand how a neuron operates. A neuron contains a cell body//soma//perikaryon, which contains a nucleus and Nissl bodies (dense ribosomes) on which neurotransmitters are produced. Off of the body (in a multipolar neuron) are extensions called dendrites which have receptors embedded in their membranes so that neurotransmitters from other neurons can bind and communicate. This binding creates a change in the membranes permeability and Na+ is allowed to enter. There is also another extension from the body, called an axon, and it is usually longer than the dendrites. There is a region in front of the axon, in the cell body, in which there are no granules called the Axon Hillock. It is here that the Na+ will build up and upon reaching a critical density will diffuse down the axon, where it is moved by synaptic vesicles into synaptic bulbs//synaptic terminals. A massive influx of Na+ causes the permeability to change and Ca+ enters. This rush of Ca+ causes the vesicle to burst allowing the neurotransmitters to move out and make contact with another neurotransmitter. Those neurotransmitters not used will re-enter the synaptic bulbs and be transported back to the cell body where it will be recycled. A neuron can bind with a different neurotransmitter than it produces, but it cannot produce more than one kind of neurotransmitter.
We also discussed the three structural types of neurons; unipolar, bipolar, and multi polar as well as the three types of potential for neurons. Resting potential is an inactive state in which the Na+/K+/ATP pumps in the membrane produce a -70mv across the bilayer by pumping out 3 Na+ and pumping in 2 K+ simultaneously. The second potential known as Graded or local potential is the one that I understand the least. From what I do understand the neuron reaches this potential when the charge is between -70mv and -54 mv. Once the neuron reaches a -55 mv it hits a threshold and moves into Action Potential. In this state, due to the huge change in charge, there is an influx of Na+.
In lecture we briefly discussed the structure of the nervous system, which includes the CNS, which includes the brain and spinal chord, and the PNS, which includes the nerves that travel toward and away from the CNS. These can be broke down into cranial and spinal nerves. The Autonomic system also belongs to the PNS. Along with neurons there are four types of accessory cells called Neuroglia which are part of the nervous tissue as well. Astrocytes work as a screen and stop mutagens from killing neurons, which cannot undergo mitosis. Oligodendrites produce the myelin sheath which is wrapped around Schwann cells that are attached to the axon. The myelin allows the nerve impulse to move quicker and more efficiently. Microglia are the smallest and are an immune system cell that prevents the brain from becoming infected. And lastly there are the Ependymal cells which are the producers of CFS in our brain.
The part of the lecture that I connected with was the part about the astrocytes. These are known to be the most common cells identified in childhood tumors and a close friend's son has just been diagnosed with a brain tumor. He has had several MRI's since developing atypical episodes in which he stops breathing for 1 1/2 minutes and beyond. During these episodes he can respond to stimulation such as pinching but only when severe. Neurologists believed that he had an atypical seizure disorder but after 6 months of no change in his development as well as no changes on several MRIs, they have come to the conclusion that he has an early stage brain tumor. They were able to see a small area in his brain that contained an abnormal gelatinous material and they expect that this will slowly harden and optimistically they may be able to remove it at that time. As far as I know, they do not know the type of cells that make up the tumor, and after listening to your lecture, I am curious to see if they are in fact Astrocytes.
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