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- 1. ANATOMY & PHYSIOLOGY WEEKLY Anatomy and Physiology Weekly Volume 1, Issue 1 (Informational Section) 10.17.2012 Inside this issue: Organization of the Nervous System!! Organization of 1 The nervous system is a com- CNS to the rest of the body, the Nervous plex system that is mainly divid- send motor information to ef- System ed into two sections the Cen- fectors. Somatic motor volun- tral Nervous System (CNS) tary nervous system: innervates which is the brain and spinal skeletal muscle cord and the Peripheral Nerv- Nerve Impulses 1 Autonomic motor involun- ous System (PNS) which con- Part 1 tary nervous system innervates sists of the cranial nerves (1). cardiac muscle, smooth muscle, The nervous system glands . can be broken down into other Nerve Impulses 2 divisions and sub divisions. Sen- Part 2 sory (afferent) division transmits information from periphery to CNS, contains receptors. The Synapse 2 Somatic receives sensory information from skin, fascia, joints, skeletal, muscles, special Picture is © (3) senses. Visceral receives senso- Get ready to learn all about Cells of the 3 ry information from viscera. the nervous system in this Nervous System Motor (efferent) division trans- new issue of Anatomy and mits information from body Physiology Weekly! Reflex Arc 4 Nerve Impulses Part 1 Membrane potential is acid chains snake back and potential exits only across the when a neuron is adequately forth across the membrane. stimulated , an electrical im- Some channels , leakage or no membrane. (2) pulse is generated and conduct- leakage channels , are always ed along the length of its axon. open. Channels include : This is response , called the Chemically gate, Ligand-gated, action potential or nerve im- Voltage-gated, and Mechani- pulse , is always the same re- cally gated . (2) gardless of the source or type There is also Resting of stimulus , and it underlies Membrane Potential, which is virtually all functional activities The potential difference in a of the nervous system. (2) resting neuron and the mem- brane is said to be polarized. The value of the resting mem- Membrane channels brane potential varies from - are large proteins , often with 40mV to -90mV in different several subunits , whose amino types of neurons. The resting 1
- 2. Page 2 Anatomy and Physiology Weekly Nerve Impulses Part 2 Written by —Colton Membrane Potential: difference in electrical charge across their plasma membranes. 3. As more Na+ enters the cell through Resting Membrane Potential: the mem- voltage-gated Na+ channels, the membrane brane potential maintained by a noncon- depolarized even further. ducting neuron’s plasma membrane. 4. The magnitude of the action potential Local Potential: A slight shift away from the peaks (at +30 mV) when voltage-gated Na+ RMP in a specific region of the plasma mem- channels close. brane. 5. Repolarization begins when voltage-gated © (4) Action Potential: is, as the term suggests, K+ channels open, allowing outward diffu- the membrane potential of an active neu- sion of K+. rons, that is, one that is conducting an im- 6. After a brief period of Hyperpolarization, pulse. An example of this is shown below. the resting potential is restored by the sodi- 1. A stimulus triggers stimulus-gated Na+ um-potassium pump and the return of ion channels to open and allow inward Na+ channels to their resting state. diffusion. This causes the membrane to de- polarize. 2. As the threshold potential is reached, voltage-gated Na+ channel open. The Synapse Synapse: Functional membrane to mem- Neurotransmitters: chemicals that allow brane contacts of a nerve cell with an- the transmission of signals from one © (5) other nerve cell, muscle cell, gland, cell neuron to the next across synapses. or sensory receptor; functions in the They are found at the axon endings of transmission of action potenitals from motor neurons, where they stimulate one cell to another. the muscle fibers. They and their close relatives are produced by some glands “Summation is a Summation: Phenomena in which the such as the pituitary and the adrenal phenomena in degree of changing in membrane poten- tial directly correlates with stimulation glands . (1) which… degree of frequently. changing membrane potential directly correlates with stimulation” 2
- 3. Volume 1, Issue 1 (Informational Section) Page 3 Cells of the Nervous System The nervous system is Non-neural cells are also within the central nerv- a complex structure called glial cells. Neurons ous system, Ependymal that is composed of receive stimuli and con- –found lining the canals many different types of duct action potentials. of the spinal cord and “Help send out cells. These all help Glial cells support and brain, Oligodendrocyte send out impulses and protect neurons and – found around nerve impulses… in the appropriate mes- perform other functions. fibers in the CNS, order for the sages in order for the There are five kinds of Schwann – found human body to move. glial cells; Astrocyte- around nerve fibers in human body to found on the surfaces of the PNS, and Satellite – The nervous system is move.” neurons and blood ves- found around the neu- made up of neurons sels, Microglia – found ron cell body. (1) and non-neural cells. Bipolar neuron – two nerve fibers Unipolar neuron – one nerve fiber Multipolar neuron – multiple nerve fibers Neurons carry nerve impulses from body parts to the brain and spinal cord (Picture left is a neuron ©) (6) Satelite © (10) Ependymal (11) © Oligodendrocyte (below) (12) Astrocyte(7) © © Microglia(8) © Schwann(9) © 3
- 4. Reflex Arc Lab ANATOMY AND Some of our writers got the chance to go to a local high school and watched as PHYSIOLOGY they did a lab on neuromuscular reflexes. They used an EKG sensor to compare WEEKLY the speed of voluntary vs a reflex muscle action and to measure the speed of the impulse. Here is the information that they collected! Graph 1 An special 50 collaboration with 45 40 students from NISD 35 30 25 Series2 20 Series1 15 10 5 How much do 0 1 2 3 4 5 you know about Reflexes? Graph 2 60 50 40 30 Series2 Series1 20 10 0 1 2 3 4 5 After the lab was completed the students were able to answer some ques- tions, here are their answers! 1.) The contraction wasn’t as high in the volun- tary activation as in the involuntary activation because you were voluntarily contracting your muscle. 2.) 0.097 m/s is the speed at which the stimulus traveled in Agron’s leg. 3.) What could account for the differences is the measurements of the person, having the electrodes not directly on the nerves and the force of the hit from the hammer could differ. 4.) The speed Put together of a nerve impulse is a lot slower than the speed of electricity because it has many things to go through within the body while electricity in a copper wire by—Ashley B. just goes straight from end to end with no interruptions. 5.) The size of a person can effect the time it takes for the nerve pulses to get to the brain. 4