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Neurons
Cells of the Nervous System
| Question | Answer |
|---|---|
| Central Nervous system (CNS) | brain and spinal cord |
| Peripheral Nervous system (PNS) | all nerves |
| Autonomic Nervous System(ANS) | |
| 1. Neurons 1. consist of three main parts | dendrites, cell body of neuron, and axon (8-2) |
| Dendrites | BRANCHING projections that conduct impulses to cell body of neuron |
| Axon | ENLONGATED projection that conducts impulses AWAY from cell body of neuron |
| Neurons classified according to three functions | Sensory(AFFERENT)neurons,Motor(EFFERENT)NEURONS,INTERNEURONS(CENTRAL OR CONNECTING NEURONS) |
| Sensory(AFFERENT)neurons | conduct impulses to the spinal cord and brain |
| Motor(EFFERENT)neurons | conduct impulses AWAY from brain and spinal cord to muscles and glands |
| Interneurons | conduct impulses from sensory neurons to motor neurons or among a network of interneurons; also known as central or connecting neurons |
| Glia(neuroglia) | SUPPORT cells, bringing the cells of nervous tissue together STRUCTURALLY and FUNCTIONALLY |
| Glial Cells Three Main Typesof the CNS | A. astrocytes, Microglia,Oligodendrocytes |
| Astrocytes(glial cells CNS) | STAR SHAPED cells that ANCHOR small blood vessels to neurons |
| Microglia(glial cells CNS) | small cells that move in INFLAMED brain tissue carrying on PHAGOCYTOSIS |
| Oligodendrocytes(glial cells CNS) | form MYELIN SHEATHS on axons in the CNS |
| A. Nerve(NERVES AND TRACTS 8-4) | bundle of peripheral axons |
| 1. Tract(NERVES AND TRACTS 8-4) | BUNDLE OF CENTRAL AXONS |
| 2. White Matter(NERVES AND TRACTS 8-4) | tissue composed of MYELINATED AXONS (NERVES AND TRACTS) |
| 3. Gray Matter(NERVES AND TRACTS 8-4) | tissue composed of primarily of UNMYELINATED FIBERS |
| B.Nerve Coverings | FIBROUS connective tissue |
| 1. Endoneurium(nerve covering) | surrounds individual fibers within a nerve |
| 2. Perineurium(nerve covering) | surrounds a group(fascicle) of nerve fibers |
| 3. Epineurium(nerve covering) | surrounds the entire nerve |
| A. Nerve impulses(reflex arcs) | are conducted from receptors to effectors over neuron pathways or reflex arcs; conduction by a reflex arc results in a reflex (that is, contraction by a muscle or secretion by a gland) |
| B. The two-neuron arcs- simplest reflex arcs(reflex arcs) | consisting of sensory neurons synapsing in the spinal cord with motor neurons |
| C. Three-neuron arcs(reflex arcs) | consist of sensory neurons synapsing in the spinal cord with interneurons that synapse with motor neurons see 8-5 |
| Nerve Impulses(ALSO ACTION POTENTIAL) | Definition self propagating wave of electrical disturbance that travels along the surface of a neuron membrane(called also action potential) |
| Mechanism(action potential/ nerve impulses) | 1.at rest, the neuron's membrane is slightly positive on the outside-polarized-from a slight excess of Na+ on the outside |
| Mechanism(action potential/nerve impulses) | A stimulus triggers the opening of of Na+ channels in the plasma membrane of the neuron |
| Mechanism(action potential/nerve impulses) | inward movement of Na+ depolarizes the membrane by making the inside more positive than the outside at the stimulated point; this depolarization is a nerve impulse(action potential) |
| Mechanism(action potential/nerve impulses) | The stimulated sec. of mem. immediately repolarizes, by bythat time the depolarization has already triggered next section of mem to depolarize, thus propagating a wave electrical disturbances all the way down the mem. |
| The Synapse | Definition the place where impulses are transmitted from one neuron to another(the postsynaptic neuron) 8-7 |
| The Synapse made of three structures | synaptic knob, synaptic cleft, plasma membrane |
| The Synapse Neurotransmitters | bind to specific receptor molecules in the membrane in the membrane of a postsynaptic neuron, opening ion channels and thereby stimulating impulse conduction by the membrane |
| The Synapse Names of Neurotransmitters | acetylcholine, catecholamines(norepinephrine, dopamine, and serotonin) endorphins, enkephalins, nitric oxide(NO) and other compunds |
| 1. The Brainstem consists of 3 main parts | A.in ascending order: medulla oblongata,pons, and midbrain |
| 1. The Brainstem Structure | B.white matter with bits of gray matter scattered through it |
| 1. The Brainstem Functions | 1) all three parts of brainstem are two-way conduction paths. a)Sensory tracts in the brainstem conduct impulses to the higher parts of the brain. b)Motor tracts conduct from higher parts of the brain to the spinal cord |
| 1. The Brainstem Functions cont... | Gray matter areas in the brainstem function as important reflex centers. |
| 1. Cerebellum Structure | 1)second largest part of the human brain |
| 2. Cerebellum Structure Gray matter | gray matter outter layer is thin but highly folded, forming a large surface area for processing infomration. |
| 3. Cerebellum Structure Arbor vitae | internal, treelike network of white matter tracts. |
| Cerebellum Function | helps control muscle contactions to produce coordinated movements so that we can maintain balance,move smoothly, and sustain normal postures |
| Cerebellum Function | variety of additional coordinating effects, assisting the cerebrum and other regions of the brain |
| Hypothalamus (Diencephalon) | consists mainly of the posterior pituitary gland, pituitary stalk, and gray matter |
| Hypothalamus(Diencephalon)) | acts acts as the major center for controlling the ANS, therefore it helps control the functioning of most internal organs |
| Hypothalamus (Diencephalon) | Controls hormone secretion by anterior and posterior pituitary glands; therefore it indirectly helps control hormone secretion by most other endocrine glands |
| Hypothalamus (Diencephalon) | contains centers for controlling body temperature, appetite, wakefulness, and pleasure |
| Thalamus (Diencephalon) | Dumbbell-shaped mass of gray matter extending toward each cerebral hemisphere |
| Thalamus (Diencephalon) | Relays sensory impulses to cerebral cortex sensory areas |
| Thalamus (Diencephalon) | In some way produces the emotions of pleasantness or unpleasantness associated with sensations |
| Pineal gland (pineal body) (Diencephalon) | small body resembling a pine nut behind the thalamus |
| Pineal gland (pineal body)(Diencephalon) | adjusts output of "timekeeping hormone" melatonin in response to changing levels of external light (sunlight and moonlight) |
Created by:
pbeverly
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