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What two systems is the nervous system divided into? |
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The nervous system is divided into the peripheral nervous system, and the central nervous system. |
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What does the central nervous system consist of? |
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The central nervous system consists of the brain and spinal cord. |
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What does the peripheral nervous system consist of? |
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The peripheral nervous system consists of all of the nerves that extend to outlying parts of the body, includes spinal and cranial nerves. |
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What are the general functions of the nervous system? |
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Nervous system general functions: Sensory function, Integrative function, and Motor function. |
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What does the 'sensory function' of the nervous system consist of? |
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The 'sensory function' of the nervous system consists of sensory receptors and the ends of peripheral neurons the detect changes in the external or internal environment and convert that information in the form of impulses and are transmitted to the CNS. |
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When is the integrative function used? |
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The integrative function is used when the signals reach the CNS and are immediately used and/or stored in memory------->makes a decision------>decision sent by means of motor function. |
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What is the motor function used for? |
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The motor function is used to carry impulses from the CNS to effectors. |
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What are the two types of nervous tissue and their functions? |
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The two types of nervous tissue and their functions:
1. Neurons - transmit impulses
2. Neuroglia - supportive accessory cells. |
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What does the cell body of a neuron contain? |
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The cell body of a neuron contains the nucleus and other organelles and may serve as a receptor surface for other neurons to communicate with. |
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What does the chromatophilic substance consist of? |
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The chromatophilic substance consist of rough endoplasmic reticulum and is the site of protein synthesis. |
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What can't neurons reproduce? |
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Neurons do not reproduce because they lack centrioles, important components of mitosis. |
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What are dendrites? |
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Dendrites are projections for the cell body that carry signals from presynaptic neurons toward the cell body. |
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What does an axon do? |
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An axon serves to conduct impulses away from the body. |
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What is the general direction of an impulse? |
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The general direction of an impulse:
Dendrite----> Cell body----> Axon----> Nerve terminals. |
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What is a synapse? |
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A synapse is the junction betweentwo neurons where the action potential in the pre-synaptic neuron influences the membrane potential of the post-synaptic neuron by release of a neurotransmitter. |
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What does an axon begin as? |
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Axons begin as a single fiber, but can branch off to form collaterals that can connect with many cells. |
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What does an action potential cause? |
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An action potential causes an electric current that stimulates more action potentials to adjacent portions of neuronal membrane. |
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What is the propagation of the action potential along an axon called? |
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The propagation of the action potential along an axon is a nerve impulse. |
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What is an unstimulated neuron? |
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An unstimulated neuron is said to be polarized. |
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What causes polarization? |
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Polarization is due to the unequal distribution of ions across the membrane (inside is more negative and has a higher concentration of potassium and the outside is more positive and has a higher concentration of sodium). |
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What is the high concentration of positive ions caused and maintained by? |
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The high concentration of positive ions is due to and maintained by the sodium potassium pump. |
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What is the resting membrane potential? |
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The resting membrane potential is an unstimulated neuron. |
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What is graded potential a result of? |
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A graded potential is a result of stimulation, but not enough to hit threshold or can become more negative. Also is local, it does not affect propagation. |
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When is an action potential reached? |
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An action potential is reached when enough sodium channels open allowing for enough depolarization to hit threshold. |
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Is action potential an all or nothing response? |
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An action potential IS an all or nothing response (once threshold is reached, sodium channels will continue to open until a complete action potential is reached). |
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Define:
Depolarization |
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Depolarization: means the membrane potential becomes less negative. |
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Define:
Hyperpolarized |
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Hyperpolarized: means the membrane potential becomes more negative. |
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Define:
Repolarization |
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Repolarization: occurs after an action potential when the resting membrane potential is established. |
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What happens if sodium channels open? |
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If sodium channels open the membrane depolarizes. |
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What happens if potassium channels open? |
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If potassium channels open the membrane hyperpolarizes or helps return to resting potential. |
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What is synapse? |
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A synapse is the junction between two neurons; a presynaptic neuron (transmitting neuron) and a post synaptic neuron (receiving neuron). |
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What is the synaptic cleft? |
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The synaptic cleft is the gap between part of the two neurons at the synapse. |
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When can a synapse occur? |
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A synapse may occur between an axon and either a dendrite or a cell body. |
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What are synaptic knobs? |
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Synaptic knobs are the round 'buttons' at the end of axons and contain the synaptic vesicles, which house the neurotransmitters. |
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How is a neurotransmitter realeased and how does it 'transfer' the signal to the next neuron? |
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How a neurotransmitter is realased and 'transfers' the signal to the next neuron: An impulse reaches the ends of the axon at the synaptic knobs----> Calcium ion channels open-----> Calcium diffuses inward-----> The increase in intracellular calcium causes the synaptic vesicles to fuse with the cell membrane----->Neurotransmitters are released by exocytosis-----> Diffuse across the synaptic cleft-----> react with receptors on the post synaptic membrane. |
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How is an action potential generated? |
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An action potential is generated by the release of neurotransmitters, the peptide neurotransmitters are synthesized in the rough endoplasmic reticulum of the neuron cell bodies and transported in vesicles down the axon to the nerve terminal. |
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What can neurotransmitters cause ion channels to do? |
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Some neurotransmitters can cause ion channels to either open or close at the post synaptic membrane. |
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What happens when the neurotransmitter causes the sodium ion channels to open? |
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When the neurotransmitters cause the sodium ion channels to open, it is called a excitatory post synaptic potential (EPSP) because it may propagate an action potential. |
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What happens when the neurotransmitter causes the potassium ion channels to open? |
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When neurotransmitters cause the potassium ion channels to open, it is called an inhibitory post synaptic potential (IPSP), because the membrane becomes hyperpolarized and harder for an action potential to be achieved. |
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What is an example of an excitatory neurotransmitter and what does it do? |
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Acetylcholine is an example of an excitatory neurotransmitter and serves to stimulate muscle contractions. |
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Can epinephrine be an excitatory neurotransmitte? |
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Epinephrine can be an excitatory or an inhibitory depending on the receptor type. |
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What is the amount of neurotransmitter released related to? |
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The amount of neurotransmitter released is directly related to the amount of calcium influx (higher calcium = more neurotransmitter) |
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What are the mechanisms of neurotransmitter termination? |
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The mechanisms of neurotransmitter termination is decomposition, reuptake and diffusion. |
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What is a myelinated neuron and what does it serve to do? |
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A myelinated neuron is a neuron in which the axon is intermittently encased in multiple layers of myelin and serves to increase the conduction speed of an impulse. |
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What is saltatory conduction? |
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Saltatory conduction is a type of conduction in a myelinated neuron. |
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Why is conduction speed increased? |
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Conduction speed is increased because the myelinated fibers insulate the axons, which cause the impulse to jump from gap to gap, reduces the overall length of travel (the gaps are called nodes of ranvier). |
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What if the diameter is larger? |
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The larger the diameter, the faster the transmission. |
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What is myelin made from? |
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Myelin is made from multiple layers of a glial cell (accessory nerve cell). |
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What are oligodendrocytes? |
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Oligodendrocytes are the glial cells the serve myelinate the neurons in the CNS and schwann cells are the glial cells that serve to myelinate the neurons in the PNS. |
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What is the function of astrocytes? |
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Astrocytes:
Maintaining blood brain barrier, perform repairs, guiding neuron development, controlling composition of the extraceullar fluid |
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What is the function of oligodendrocytes? |
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Oligodendrocytes:
Myelination of neurons in the CNS. |
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What is the function of microglia? |
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Microglia:
Specialized immune cells of the CNS. |
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What is the function of Ependymal cells? |
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Ependymal Cells:
Line the chambers and passage filled with CSF; assist in circulation of CSF. |
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What is the function of Schwann cells |
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Schwann Cells:
Myelination of neurons in PNS. |
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What color do myelinated neurons appear? |
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Myelinated neurons appear white. |
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What color do unmyelinated neurons appear? |
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Unmyelinated neurons appear gray. |
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What do sensory neurons (afferent neurons) do? |
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Sensory neurons (afferent neurons) carry impulsews into the CNS and either have receptor ends at the tip of their dendrites or they have dendrites near the receptor cells (most sensory are unipolar). |
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Where so interneurons lie? |
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Interneurons lie within the brain and spinal cord (CNS), are multipolar and transmit impulses in three ways: from one part of the brain or spinal cord to another, 'directing traffic' : sends impulse to appropriate region of to motor neurons. |
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What do motor neurons do? |
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Motor neurons carry impulses out of the CNS to effectors (muscles or glands). |
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