Anatomy and Physiology Exam 2 Figueroa GOOD LUCK The Nervous System The nervous system controls our behaviors memories and movements Functions Sensory sense changes both internally and externally via sensory receptors Integrative allows us the ability to analyze the sensory info received store aspects and Motor function response via movement in reaction to stimuli by initiating action Afferent muscle brain make decisions Efferent brain muscle Easy way to remember which comes first A comes before E so the sensory neurons need to be stimulated first then it sends impulse to the brain which processes it then the brain says what to do by stimulating the motor neurons to give a reaction movement Synapse connection If reaction involves the brain it is NOT a reflex It is only a reflex when it is involuntary and the brain is not involved the Nervous system has 2 main divisions Central Nervous system CNS Central center of the body The brain midbrain and spinal cord are all in the center of the body Peripheral Nervous system PNS consists of cranial and spinal nerves these nerves contain both sensory and motor fibers connects CNS to muscles glands and all sensory receptors made up of 2 systems Somatic Nervous system SNS control muscles connected to bone soma body Autonomic Nervous system ANS controls internal organs Enteric Nervous system is part of the ANS do NOT focus on the ANS for exam 2 Sensory Afferent Somatic fibers brain Visceral fibers organ brain carry impulses FROM the skin skeletal muscles and joints TO the carry impulses FROM visceral organs TO the brain Motor Efferent impulses are sent FROM CNS TO effector organs brain organ Neurons a neuron is the main functional unit of the Nervous system produce action potential electrical signal excitability made up of a single nucleus with a prominent nucleolus 2 kinds sensory and motor sensory afferent neurons motor efferent neurons Structure have 2 propagations processes Dendrites receive signals Axons contains plasma membrane End in a axon terminals transmits electrical impulses produced by the soma Soma the body Everything organelles in a cell is in the soma neurotransmitters and electrical impulses Axon terminal where neurotransmitters are stored and released upon Action Potential the signal that will propagate travel transport receptive or input region contains receptors receives stimulus connected to dendrites produce stimulation can travel long distances Think of baseball player receptor ball neurotransmitter pitcher axon terminal Myelin a lipid fat increases the speed of nerve impulse conduction from the soma to the axon terminal myelinated axons are surrounded by myelin Unmyelinated axons have slower nerve conduction Myelin AND axon diameter are factors for how fast a neurotransmitter can travel the larger the diameter the faster the impulse fastest myelinated wide axon White matter mostly myelinated axons Gray matter neuronal cell bodies dendrites unmyelinated axons and axon terminals the different colors are caused by which part of the neurotransmitter is on the inside outside Soma is more dense therefore it makes up gray matter the brain consists of the gray matter surrounding the white matter the spinal cord consists of white matter surrounding the gray matter Neurons are excited due to the voltage difference across their membrane Types of Ion Channels Ligand gated channel open and close in response to a stimulus Figueroa gave the example of the teacher parking lots on campus Na car key card neurotransmitter Acetlycholine or Ach gate gate receptor the little box that reads the card the gate can only be opened when a neurotransmitter connects with a receptor in an instant doesn t need to stay then the gate opens and the Na can travel in Na diffuses into the cell Voltage gated channel open in response to a direct change in the membrane potential Resting Membrane Potential the electrical charge inside the membrane Negative ions ex Cl and sodium are inside the cell membrane Positive ions are outside the cell membrane Potential energy difference at REST is 70mV this is caused by the extracellular fluid containing a high amount of Cl and Na the cytosol containing a high amount of K organic phosphate and amino acids membrane permeability the membrane is 50 100 times more permeable for K Na K pump removes Na as soon as it leaks in K flows out of the cell at a higher rate than the flow of Na into the cell Action Potentials a nerve impulse stimulation triggers the release of neurotransmitters a sequence of events that causes the membrane potential to decrease so much that it reverses becomes positive and then it restores itself by becoming more negative until it reaches its resting state during an action potential voltage gated Na and K channels are OPEN a stronger stimulus will NOT cause a larger impulse REMEMBER polar means it is NEGATIVE Neurotransmitter opens the gate of the channel allowing Na to enter the cell Na goes into the cell causes depolarization once a cell becomes positive the K channels open and K leaves the cell Na channels have already closed repolarization this causes the cell to become more negative since potassium is positive and it is leaving REMEMBER even though Na is traveling into the cell there is ALWAYS more Na outside of the cell than inside Depolarization make less negative aka to more positive stimulus causes potential to exceed threshold 55mV become more positive than the threshold Na diffusion Positive Feedback process Repolarization to make more negative back to normal polarity Hyperpolarization more negative than at rest so more negative than 70mV is a part of the stimulation due to an action potential hyperpolarization occurs once the potential reaches 90mV causing the K channels to close and the membrane potential returns to resting potential Resting potential 70mV Threshold 55mV if it does not reach the threshold then the action potential doesn t occur Propagation moving or traveling of an action potential Synapses 2 types but only focus on chemical synapses Synapse communication between two neurons neuron 1 s axon terminal and neuron 2 s dendrite or soma form a synapse one way information transfer from a presynaptic neuron to a postsynaptic neuron PRE before POST after presynaptic works with axon terminal and postsynaptic is with dendrite or soma axodendritic from axon to dendrite axosomatic from axon to soma cell body Process 1 in the presynaptic neuron action potential nerve impulse causes the
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