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| (from Greek glia, meaning glue) structurally and functionally support and protect the neurons. They outnumber neurons 10 to 1 but not directly involved in the transmission of info or impulses through the nervous system. Rather they are important parts of the infrastructure necessary for the neurons to do their jobs. |
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| – nerve cells – the basic, functional units of the nervous system. They are the smallest pieces of the system that show basic nervous system that show basic nervous system fxns, such as responding to stimuli and conducting impulses from one part of the cell to another. Very high requirement for O2, can’t go w/o more than a few min. this is why CPR must be started w/in a few minutes of cardiac arrest. The heart may start again after that but there could be brain damage if the neurons were w/o O2 for too long. |
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| nervous tissue containing many myelinated axons. Axons are covered with a fatty substance called myelin. Myelin grossly (w/o magnification) appears white |
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| nervous tissue that is made up of neuron cell bodies appears darker and thus is called gray matter. |
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| the cell membranes of specialized glial cells called oligodendrocytes in the brain and spinal cord, and Schwann cells in the nerves outside of the brain and spinal cord. |
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| specialized glial cells in the brain and spinal cord whose cellular membrane forms the myelin sheath for axons in the CNS. |
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| – glial cells associated with the peripheral nerves whose cellular membrane forms the myelin sheath for axons in the PNS. |
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| unmyelinated areas of the axon between two adjacent Schwann cells that are involved in rapid conduction of nerve impulses along the axon. |
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| Peripheral Nervous System (PNS |
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| nerves outside of the central nervous system (ie, outside of the brain and spinal cord) |
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| Central Nervous System (CNS) |
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| – the brain and the spinal cord |
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| nerve that carries impulses toward the CNS |
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| nerve that carries impulses away from the CNS |
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| – the part of the nervous system that controls smooth muscle, cardiac muscle, and endocrine glands automatically and w/o conscious control. |
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| conscious or voluntary nervous system controlling skeletal muscles; somatic motor fxn is the efferent branch and the somatic sensory fxn is the afferent branch. |
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| gray matter that makes up the outer layer of the cerebellum |
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| white fibers that connect and provide communication pathways between the two cerebral hemispheres |
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| (singular, gyrus) the folds that provide the wrinkled appearance f the surface of the cerebral hemispheres |
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| – (singular, sulcus) – grooves, esp shallow grooves in the cerebral cortex |
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| prominent groove that divides the cerebrum into right and left cerebral hemispheres |
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| the two halves of the cerebrum |
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| second largest component of the brain; allows the body to have coordinated movement, balance, posture, and complex reflexes |
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| serves as a nervous system passageway between the primitive brain stem and the cerebrum; three major structures of the diencephalon include the thalamus, the hypothalamus, and the pituitary |
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| – part of the diencephalons that acts as a relay station for regulating sensory impulses to the cerebrum |
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| a portion of the diencephalon that has extensive links to the brain and to the pituitary gland. It fxns as an important bridge between the nervous and the endocrine systems |
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| – the master endocrine gland. A pea-sized endocrine gland located at the base of the brain; made up of the anterior pituitary gland, which produces seven known hormones, and the posterior pituitary gland, which stores and releases two hormones from the hypothalamus; also called the hypophysis. |
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| the connection between the brain and the spinal cord; composed of the medulla oblongata, the pons, and the midbrain; heavily involved in autonomic control functions related to the heart, respiration, blood vessel diameter, swallowing, and vomiting |
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| – the part of the brain stem just above (cranial to) the spinal cord |
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| part of the brain stem located just rostral to the medulla oblongata |
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| set of connective tissues that surround the brain and spinal cord; the three layers of the meninges, from outside to innermost layer, are the dura mater, the arachnoid and the pia mater |
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| – the outermost layer of the meninges that covers the brain and spinal cord; it is considered to be the toughest of the meninges |
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| the innermost layer of the meninges |
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| – the delicate, weblike layer of the meninges between the dura mater and the pia mater |
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| (CSF) fluid that bathes and protects the brain and spinal cord from the hard inner surface of the skull and spinal vertebrae |
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| the functional barrier between the capillaries in the brain and the nervous tissue; anatomically composed of capillary walls w/o the openings found in other capillaries and glial cells |
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| set of 12 pairs of nerves originating directly from the brain; may be sensory or motor or may contain both sensory and motor nerves |
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| The Cranial Nerves (list of all twelve) |
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Definition
Name – Type - Key Functions
I. Olfactory - Sensory – Smell
II. Optic – Sensory – Vision
III. Oculomotor – Motor – Eye movement, pupil size, focusing lens
IV. Trochlear – Motor – Eye movement
V. Trigeminal – Both sensory and motor – Sensations from the head and teeth, chewing
VI. Abducent – Motor – Eye movement
VII. Facial – Both sensory and motor – Face and scalp movement, salivation, tears, taste
VIII. Vestibulocochlear – Sensory – Balance, hearing
IX. Gflossopharyngeal – Both – Tongue movement, swallowing, salivation, taste
X. Vagus (wanderer) – Both – sensory from gastrointestinal tract and respiratory tree; motor to the larynx, pharynx, parasympathetic; motor to the abdominal and thoracic organs,
XI. Accessory – Motor – Head movement, accessory motor with vagus
XII. Hypoglossal – Motor – Tongue movement |
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| (plural – ganglia) clusters of neuron cell bodies outside the CNS |
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| reflexes resulting in the stimulation or inhibition of skeletal muscle contraction |
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| – reflex initiated by stretch receptors w/in a muscle that results in contraction of the muscle to compensate for the stretching |
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| a reflex that results in stimulation or inhibition of smooth or cardiac muscle or endocrine gland fxn; mechanisms of homeostasis are autonomic reflexes |
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| – reflex arc in which painful stimulus on skin causes contraction of the affected limb; also called the flexor reflex |
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| – reflex initiated by a stimulation of a limb that results in extension of the limb on the other side of the body. |
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| – reflex response that is more pronounced than normal |
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| reflex response is less than normal |
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| – the animal blinks or retracts the globe when the cornea is touched. This reflex persists well into the deep levels of anesthesia. The corneal reflex is seldom used in monitoring anesthesia; it is used more often to help assess the point of death during euthanasia. |
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| as the anesthetic depth increases, the pupil constricts more slowly in response to a light shined at it |
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| – when a neuron is not being stimulated, not conducting impulse, just waiting. Still working to maintain resting state – cell membranes elec polarized at rest |
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| Resting membrane potential |
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Definition
| what a neuron in a resting state has - difference in electrical charge across neuronal membrane. Relatively more + charge on the outside than on the inside. This is because Na+ can’t readily diffuse or leak thru the cell memb on its own so the action of the sodium-potassium pump causes a higher concentration of Na+ to accumulate outside the cell. The action of the sodium-potassium pump and the – charges inside the cell cause a higher concentration of potassium to accumulate inside the cell. By keeping the sodium on one side of the memb (outside) and potassium on one side (inside), the cellular memb between the two is said to be polarized (because it has two distinct poles of ions on either side of the memb). |
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| specialized molecule that helps maintain cell resting state |
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Definition
a stimulus of sufficient intensity to generate a nerve impulse
when the stimulus is strong enough to cause complete depolarization, it is said to have reached the “threshold”, and this causes the cell to depolarize or “fire”
- stimulus must be sufficient to make the neuron respond and cause complete depolarization
- “all-or-nothing principle” – neuron depolarizes to its maximum strength or not at all
- conduction of the action potential – spreading wave of opening sodium channels in sufficient numbers to allow sodium influx and depolarization
wave of depolarization or nerve impulse |
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Term
| stages of neuron function |
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Definition
- resting state (w/resting membrane potential)
- depolarization
- repolarization
- refractory period |
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Term
| Resting membrane potential |
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Definition
what a neuron in a resting state has - difference in electrical charge across neuronal membrane. Relatively more + charge on the outside than on the inside. This is because Na+ can’t readily diffuse or leak thru the cell memb on its own so the action of the sodium-potassium pump causes a higher concentration of Na+ to accumulate outside the cell. The action of the sodium-potassium pump and the – charges inside the cell cause a higher concentration of potassium to accumulate inside the cell. By keeping the sodium on one side of the memb (outside) and potassium on one side (inside), the cellular memb between the two is said to be polarized (because it has two distinct poles of ions on either side of the memb).
results from differences in distribution of positive and negative charges from sodium, potassium, proteins, and other charges ions on either side of the neuronal membrane |
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| the 3 ways info reaches the CNS |
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Definition
(sensors that tell the brain what’s going on
- Somatic Nervous System (SNS) - Somatic receptors – let you know what’s going on from your arms/legs: Sensory receptors – eyes also hot/cold/etc
- Autonomic Nervous System (ANS) – info you might not be aware of like how often breathing, heart rate, etc
- Enteric nervous system (ENS) – particulary GI tract and enteric plexuses – tells what’s going on with abdo organs |
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| Once in the CNS, info goes to ... |
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Definition
Once in the CNS go to motor part of PNS (SMN, AMN, EMN) then to effectors (ex: skeletal muscle, smooth muscle, etc)
- Somatic Motor neurons – voluntary then send info to skeletal muscle (ex: if you are cold, you put on a coat) SNS – CNS – SMN – skeletal muscle
- Autonomic motor neurons (involuntary): sympathetic and parasympathetic divisions - then send message to smooth muscle, cardiac muscle and glands
- Enteric Nervous system sends message to both CNS and to Enteric Motor Neurons (involuntary) in enteric plexuses – then to smooth muscle, glands and endocrine cells of GI tract. Because can send to both CNS and EMN can make changes in the system w/o going through the CNS |
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Definition
SNS – CNS – SMN – skeletal muscle (ex: putting coat on when it’s cold)
ANS – CNS – AMN – smooth muscle, cardiac muscle and glands
ENS – CNS and EMN – smooth muscle, glands, and endocrine cells of GI tract
Very complex – relies on sending info, making decisions and responding to environment |
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Definition
- Afferent nerves (aka sensory nerves) – conduct impulses toward CNS
also called sensory nerves – conduct sensations from sensory receptors in the skin and other locations in the body to the CNS |
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| Somatic Nervous System (SNS) |
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Definition
| Somatic receptors – let you know what’s going on from your arms/legs: Sensory receptors – eyes also hot/cold/etc |
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| - Autonomic Nervous System (ANS) |
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| – info you might not be aware of like how often breathing, heart rate, etc |
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| - Enteric nervous system (ENS) |
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| – particulary GI tract and enteric plexuses – tells what’s going on with abdo organs |
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| - Efferent nerves(as in produce effect) |
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Definition
| ) (aka motor nerves) (cause movement, as in motoring down the road) – conducts impulses away from CNS - cause skeletal muscle contraction and movement |
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Term
| - Cranial and spinal nerves in the PNS and nerve tracts (bundles of axons) in the CNS |
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Definition
| - Cranial and spinal nerves in the PNS and nerve tracts (bundles of axons) in the CNS may carry nerve fibers that are sensory (carrying info toward the CNS), motor (carrying info away from the CNS), or both. They are large nerves. |
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Definition
| actions under conscious, or voluntary, control |
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| - autonomic nervous system |
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| – controls and coordinates autonomic functions (ex: slowing of the heart rate in response to an increased blood pressure) |
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Definition
- neuron receives external stimulus
- sodium channel opens on neuron cell membrane
- sodium ions flow into cell by passive diffusion
Action potential
- during depolarization, inside of the neuron goes from a negatively charged resting membrane potential to a net positive charge due to inflow of sodium ions
- creates large change in electrical charge from negative to positive |
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Definition
- sodium channels close
- K+ channels open
- K+ diffuses out of the cell
- Resting state restored
- As repolarization ends, sodium-potassium pump moves sodium and potassium ions back to their original sides
- Resting state restored |
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Term
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Definition
- time period during which a neuron is insensitive to additional stimuli
cell is still in depolarization/early repolarization
- absolute refractory period – during sodium influx and early potassium outflow
- relative refractory period – during end of the repolarization period
may be possible to stimulate another depolarization if stimulus is very large |
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Definition
| the strong influx of sodium ions during depolarization |
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Term
| Saltatory Conduction (Latin saltare “to leap”) |
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Definition
- rapid means of conducting an action potential
- Like a rubber coating on an electrical wire prevents shorts, the myelin sheath wrapped around the axons prevents sodium ions from flowing across the neuronal cell membrane
- Therefore depolarization in myelinated axons can only take place at the nodes of Ranvier – when the sodium influx at one node is sufficient to open adjacent sodium channels, the next available sodium channels is at the next node of ranvier.
- The depolarization wave in the myelinated axon skips from one NOR to the next, greatly accelerating the rate at which the depolarization wave moves from the neuron cell body to the other end of the axon.
- The rapid conduction of impulses through myelinated neurons by saltatory conduction makes processes such as vision and fine motor control possible in larger animals, such as humans, and many domestic animal species. |
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Term
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Definition
- Synapse – junction between two neurons or a neuron and a target cell
- Synaptic cleft – gap between adjacent neurons
- Presynaptic neuron – neuron bringing the depolarization wave to the synapse
releases neurotransmitter
- postsynaptic neuron – contains receptors for the neurotransmitter
- telodendron – branched structure on presynaptic neuron
terminal bouton – slightly enlarged bulb on each end of telodendron (synaptic end bulb, synaptic knob)
vesicles in the knob contain the neurotransmitter
- when depolarization wave reaches synaptic knob, vesicles fuse with the knob’s cellular membrane and dump neurotransmitter into the synaptic cleft
- neurotransmitters diffuse across the synaptic cleft toward the postsynaptic membrane
- receptors on the postsynaptic membrane bind the neurtransmitter |
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