Bi+12+Nervous+system


 * Unit 7 Nervous System**

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 * Nervous System -- Neuron, Impulse Generation and Reflex Arc**

Neuron: Dendrite- extension leading toward the cell body, recieving signals from other neurons. Axon- Fiber of a neuron that conducts nerve impulses away from the cell body. Cell Body- Portion of the neuron that contains a nucleus and from which dendrites and an axon extend.
 * 1. Identify and give functions fo each of the following: dendrite, cell body, axon.**

Sensory Neurons- a type of nerve cell that conducts an impulse from a receptor to the CNS; Have long dendrites and short axons and their cell bodies are located along the dorsal root at ganglia. Motor Neurons- the type of nerve cell that has a long axon and a short dendrite, and whose cell body is located in the CNS; the axon conducts an impulse out of CNS to an effector. Interneurons- Connect sensory neurons to motor neurons, carries nerve impulses within CNS.
 * 2. Distinguish among sensory, motor, and interneurons with respect to structure and function.**

http://www.youtube.com/watch?v=5uQZfaURU_Y
 * 3. Explain the transmissionof a nerve impulse through a neuron, using the following terms:

- Resting and Action potential** -when no impulse is going through a neuron it has resting potential, when an impulse is moving thorugh a neuron it is called action potential -an action potential is caused by positive ions moving in and then out of the neuron at a certain spot on the neuron membrane -an action potential is initiated by a stimulus above a certain intensity or threshold

- Depolarization is caused from the flow of Na+ ions diffusing into the membrane, causing the inside of the membrane to also become positively charged. - Repolarization is when K+ gates open and K+ diffuses to the outside of a neuron, restoring the polarity of the membrane
 * - Depolarization and Repolarization**

- The sodium gate will open, because there's more sodium on the outside than the inside of the membrane, sodium then diffuses rapidly into the nerve cell. - All these positively charged sodiums rushing in causes the membrane potential to become positive. - The sodium channels open only briefly, then close again. - The potassium gates then open, and, because there is more potassium inside the membrane than outside, positively charged potassium ions diffuse out. - As these positive ions go out, the inside of the membrane once again becomes negative with respect to the outside.
 * - Sodium and potassium gates**

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html -maintains the unequal concentration of sodium and potassium by actively transporting ions against their concentration gradients -Na/K pumps are use carrier proteins and moves Na+ out of the neuron and K+ back into the neuron (Refractory period)
 * - Sodium and Potassium pump**

When Na+ and K pumps restore the resting membrane by moving Na+ out and K+ back into the neuron - resets neuron so it can create the next AP (nerve impulse)
 * - Recovery or refractory period**

-a potential stimulus must reach a minimum level (threshold) in order for depolarization to occur -if threshold not reached, no impulse is created - a stronger stimulus does not create a larger impulse but instead more neurons will reach threshold level and conduct impuses to the central nervous system
 * - Threshold ("all or none response")**

-** If nerve fibre is myelinated, the impulse will travel faster because in these nerves action potential will have to occurs only at the nodes of ranvier. Otherwise in non-myelinated nerve fibre, action potential has to occur throughout the lenght. So in myelinated nerve fibre, the speed of impulse conduction will be much faster. http://www.youtube.com/watch?v=XgIaAs_ONG4
 * 4. Relate the structure of a myelinated nerve fibre to the speed of impulse conduction.

the major components of a synapse are the presynaptic neuron (contains synaptic vessels holding neurotransmitters, which are attached by contractile protein), the synaptic cleft (space between the two neurons) and post synaptic neuron (contains receptors that bind to neurotransmitters).
 * 5. Identify the major components of a synapse.**

http://www.youtube.com/watch?v=5uQZfaURU_Y&feature=related

-when an impulse reaches the end of an axon (endplate) calcium ions move into the endplate -this casues the contractile proteins to pull the synaptic vessicles toward the membrane - the synaptic vessicle merges with presynaptic membrane and exocytosis occurs which releases neurotransmitters - neurotransmitters then diffuse across the synaptic cleft and binds to the postsynaptic receptors
 * 6. Explain the process by which impulses travel across a synapse.**

Enzymes breakdown neurotransmitters left in the cleft. - one such enzyme is acetycholinesterase which breaks down the neurotrasmitter acetycholine
 * 7. Demonstrate knowledge of how neurotransmitters are broken down in the synaptic cleft.**

- the simplest neural pathway that's involuntary, fast and unconscious - occurs without any brain coordination or thought process eg. blinking, pulling away from heat -includes all three types of neurons (sensory, interneurons and motor neurons). http://www.youtube.com/watch?v=Y5nj3ZfeYDQ -receptors from a sense organ is designed to detect a stimulus -sensory neurons conduct nerve impulses to the interneurons in the spinal cord
 * 8. Relate the structure of a reflex arc to how it functions.**


 * Nervous System -- Divisions of the Nervous System and the Brain

1. Contrast the locations and functions of the central and peripheral nervous system. http://www.youtube.com/watch?v=cqvoV4R7T2g** -CNS includes the brain and the spinal cord -PNS all nerves going to/from the CNS -the PNS is divided into 2 sections:the Somatic & Autonomic NS -the CNS is composed of 2 types of nervous tissue: white matter contains mylinatea fibres and grey matter contains non-mylinated fibres. http://www.humanillnesses.com/images/hdc_0000_0001_0_img0007.jpg

Sympathetic prepares the body for stress, while Parasympathetic is the opposite and is a relax calming state. - in other words the sympathetic promotes active body functions while the parasympathetic controls the opposite(vegetative)bady functions such as sleeping and digesting food. - In the Parasympathetic NS the moter pathway has long preganglionic neurons and short postganglionic neurons, and in the Autonomic NS has short preganglionic neurons and long postganglionic neurons - Neurotransmitter in Sympathetic NS is Norepinephrine, and Acetylcholine in the Parasympathetic NS - the sympathetic nervous system increases heart rate and muscle strength whereas the parasympathetic nervous system slows the heart rate down. http://www.becomehealthynow.com/popups/sympth_parasympth.htm - nerves are located by spinal cord by the thoraic and lumbar regions of SC - nerves include a few cranial nerves such as the vagus nerve and nerves by the SC in the sacral region
 * 2. Differentiate between the function of the sympathetic and parasympathetic divisions of the autonomic nervous system.**

-Adrenalin is released from the Adrenal Medulla - it is the body's response to perceived danger. -it will stimulate the same responses as the sympathetic nervous system such as increased heart rate, alteration in blood flow, widened air passageways, widened pupils etc.
 * 3. Identify the source gland for adrenalin and explain its role in the "fight or flight" resonse.**

Parts of the Brain: - Medulla Oblongata** Closest to SC. Controls heart rate, breathing, bp, and controls the center Autonomic NS. It is also the control centre of nonconscious and involuntary actions
 * 4. Identify and give functions for each of the following:**
 * [[image:http://www.cartage.org.lb/en/themes/sciences/lifescience/generalbiology/Physiology/NervousSystem/Brain/brain_3.gif width="500" height="302" align="bottom"]]

http://www.student.britannica.com/eb/art-55626/The-cerebrum-is-the-largest-part-of-the-human-brain -Largest Portion of the brain - controls and coordinates higher thought processes eg: memory, vision, emotions, etc -communicates with and coordinates the activities of the other parts of the brain - the cerebral cortex can be divided into four sections:frontal lobes(movement,emotions), perietal lobes(speech production), occipital lobes(vision) and temporal lobes(memory,hearing). http://www.enchantedlearning.com/subjects/anatomy/brain/gifs/Brainlobes.GIF
 * - Cerebrum**

-**Relay station for sensory impulses -Receives sensory information from spinal cord and then it relay the impulses to the sorting center for the sensory info. - it is known as the "Sorting center" for incoming nerve impulses or sensory information
 * - Thalamus

-Controls balance, posture and coordinates muscle movements. -Part of the brain located posterior to the medulla oblongata and pons that coordinates skeletal muscles to produce smooth, graceful motions. It also coordinates balance and posture.
 * - Cerebellum**

-** Helps maintain the Body's internal environment. - controls the pituitary glands, for example controls the release of ADH) -serves as a link between the nervous system and the endocrine system http://www.youtube.com/watch?v=PMrPlCDGUwo - it regulates the temperature
 * - Hypothalamus

-**a band of myelinated fibres - it transmits information between hemispheres
 * - Corpus Callosum

- source of sensation and movement
 * Spinal Cord**

- ADH and oxytocin are hormones made by the hypothalamus but are stored in and released by the posterior pituitary glands - hormones form the anterior pituitary gland are made by itself but are stimulated by releasing factors that are sent by the hypothalamus. - the hypothalamus acts as a link between the Nervous System and Endocrine System
 * 5. Explain how the hypothalamus and pituitary gland interact as the neuroendocrine control centre.**