neurophysiology, central nervous system, autonomic nervous system
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| graded potential | short-distance communication; at dendrites; initiated by a stimulus that opens an ion channel (usually Na+ or K+); stronger stimulus -> stronger graded potential; lose intensity over distance; spread by passive current flow
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| depolarizing ions | Na+, Ca2+
resting membrane potential becomes less negative, results in Excitatory Post-Synaptic Potential (EPSP) that can produce an action potential if threshold is reached
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| hyperpolarizing ions | K+, Cl-
resting membrane potential becomes more negative, results in Inhibitory Post-Synaptic Potential (IPSP) that is less likely to produce an action potential
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| EPSP | Excitatory Post-Synaptic Potential
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| IPSP | Inhibitory Post-Synaptic Potential
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| threshold | what needs to be reached in order for an action potential to be generated as a result of graded potentials; for human cells, the RMP is -70, average threshold is -55.
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| summation of graded potentials | adding up of all active synapses at one time;
two types of summation:
1. spatial
2. temporal
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| spatial summation | multiple synapses are active on different dendrites at the same time
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| temporal summation | synapses are active over a period of time
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| subthreshold graded potential | do not change the RMP to -55 and therefore do not result in an action potential
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| suprathreshold graded potential | change the RMP to -55 and produce an action potential
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| action potential | long-distance communication; initiated at the axon hillock if threshold is reached by activating voltage-gated channels; do not vary in magnitude or duration; do not degrade over distance; frequency determines strength
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| phases of the action potential | 1. depolarization phase
2. repolarization phase
3. hyperpolarization phase
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| depolarization phase of an action potential | voltage-gated Na+ channel is activated; phase ends when the inactivation gate closes
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| repolarization phase of an action potential | voltage-gated K+ opens; ends when cell returns to RMP but open K+ result in hyperpolarization immediately following this stage
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| hyperpolarization phase of an action potential | voltage-gated K+ channels are still open from previous phase; ends when cell returns to RMP and K+ gates close
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| resting voltage gate | activation gate is closed, inactivation gate is open
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| open voltage gate | both activation gate and inactivation gate are open
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| inactivated voltage gate | activation gate is open, inactivation gate is closed
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| refractory period | time at which a neuron cannot be triggered because channels are already open or inactive
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| absolute refractory period | impossible to produce another action potential
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| relative refractory period | possible to produce another action potential, but only with a stronger than normal stimulus
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| axon hillock | point at which the action potential is initiated; where the first voltage-gated channels are located
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| axon potential speed | determined by axon diameter and myelination of the axon; larger diameter -> faster travel; myelinated axons -> faster travel; action potentials can travel as fas as 120 m/s in a large, myelinated axon
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| saltatory conduction | travel through myelinated axons, action potential "jumps" from one node of Ranvier to the next
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| Multiple Sclerosis | affects oligodendricytes of the CNS; degradation of myelin sheath results in action potential not being able to travel entire length of the axon
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| Guillain-Barre Syndrome | affects Schwann cells in the PNS; body attacks myelin sheaths and signal is weaker through axon
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| myelin | protective, insulating material around the axon that prevents leakage of charge out of the axon; there are no channels under the myelin so signal can travel very quickly through this section of the axon
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| factors that affect neuronal signaling | alteration in ion permeability; alteration in ion homeostasis; channel properties
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| hypernatremia | too much sodium in the plasma; depolarizes; neurons are hyperexcitable
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| hyponatremia | too little sodium in the plasma; hyperpolarizes; neurons are hypoexcitable
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| hyperkalemia | too much potassium in the plasma; depolarizes; neurons are hyperexcitable
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| hypokalemia | not enough potassium in the plasma; hyperpolarizes; neurons are hypoexcitable
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| synapse | junction between two neurons, where communication between neurons occurs
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| electrical synapse | results in voltage changes in the post-synaptic cell
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| chemical synapse | neurotransmitters are released by the pre-synaptic cell; bind to receptors on the post-synaptic cell
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| termination of neurotransmission | 1. diffusion
2. enzymatic inactivation within the synaptic cleft
3. active transport into pre-synaptic terminal or glial cells
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| acetylcholine | only neurotransmitter that activates skeletal muscles
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| SSRI | Selective Seratonin Reuptake Inhibitor; found in many anti-depressants, anxiety meds; inhibits reuptake of seratonin so that more seratonin is available to bind to receptors
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| acetylcholinesterase | enzyme that disables acetylcholine
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| reuptake | active transport of a neurotransmitter back to the pre-synaptic cell
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| brain stem | medulla oblongata, pons, midbrain
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| medulla oblongata | controls involuntary functions such as heart rate, blood pressure, blood vessel dilation/diameter
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| pons | controls sleep/wake cycles, respiration
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| midbrain | plays a role in cranial nerve function, especially visual and auditory
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| cerebellum | motor control; precision and coordination of movements
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| diencephalon | contains the thalamus and hypothalamus
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| thalamus | sensory relay center
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| hypothalamus | endocrine regulation; controls pituitary gland; responsible for many ANS functions
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| cerebrum | controls voluntary actions; contains primary sensory and motor areas; divided into left and right hemispheres
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| hyperexcitable neuron | requires less change in RMP to reach threshold because it is already depolarized due to hypernatremia or hyperkalemia
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| 5 lobes of the brain | frontal, parietal, temporal, occipital, insula (inside the brain, no cranial bone associated with it)
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| primary sensory/motor areas | located in different lobes of the brain, each area has a specific task - ie, vision, hearing, motor function, etc.
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| associative areas | "fine tunes" primary area functions, also involved with higher order tasks such as thinking, planning, emotional response, memory, learning, etc.
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| corpus callosum | division between left and right hemispheres; where axons cross from one hemisphere to the other
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| gray matter | cell bodies and dendrites
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| cortex | sulci and fissures of the surface of the cerebrum
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| nuclei | collections of gray matter that are located deep in the brain
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| white matter | tracts, commissures, columns
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| cranium | skull; protects the brain
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| meninges | dura mater, arachnoid mater, pia mater
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| cerebrospinal fluid | between the pia mater and arachnoid mater (subarachnoid space); protects and nourishes; 150mL volume is replaced about 3x/day
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| blood brain barrier | prevents passage of certain types of molecules between the blood and the brain; molecules like oxygen, carbon dioxide, nicotine, alcohol can easily pass;
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| choroid plexus | located in the ventricles of the brain; where cerebrospinal fluid is produced
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| ventricles of the brain | fluid filled spaces in the brain; 2 lateral ventricles, third ventricle, fourth ventricle
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| gray matter areas of the spinal cord | dorsal horn, ventral horn, lateral horn
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| white matter areas of the spinal cord | dorsal column, ventral column, lateral column
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| spinal nerves | nerves that carry sensory (dorsal root) or motor information (ventral root) to and from the spinal cord
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| dorsal horn | gray matter area of the spinal cord; sensory function
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| ventral horn | gray matter area of the spinal cord; motor function
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| lateral horn | gray matter are of the spinal cord; contains autonomic system neurons
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| dorsal column | white matter area of the spinal cord, carries sensory information to the brain (except pain and temperature)
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| ventral column | white matter area of the spinal cord, carries motor information from the brain to the effectors
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| lateral column | white matter area of the spinal cord
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| collateral | carries sensory information to the brain after a reflex occurs; allows awareness of reflex
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| polysynaptic reflex arc | reflex arc that involves more than two neurons (multiple synapses); involves a sensory neuron, an interneuron, and a motor neuron
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| monosynaptic reflex arc | reflex arc that involves only two neurons (one synapse); involves only a sensory and motor neuron
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| upper motor neuron syndrome | type of spinal cord damage that results in spastic paralysis, hypereflexia, positive Babinski test
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| lower motor neuron syndrome | type of spinal cord damage that results in flaccid paralysis, areflexia, muscle atrophy
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| higher order functions for motor control | 1. motivation/idea
2. planning
3. execution
4. correction
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| higher order functions of the limbic system | 1. outputs - feeling, emotional responses
2. motivation - dopaminergic rewards
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| limbic system | group of structures responsible for emotions and motivation
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| dopamine | neurotransmitter that activates reward/pleasure centers; alcohol, nicotine, cocaine, amphetamines, etc. also activate the dopamine reward system
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| sleep | active process required by all mammals; most neurons that control sleep and wake cycle are located in the pons and midbrain; sleep is restorative and may help bolster the immune system and memory function
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| histamine | neurotransmitter that makes you wakeful
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| antihistamine | inhibits histamine, given for inflammatory response; anti-histamines that cross the blood brain barrier (eg, Benadryl) will cause drowsiness; newer antihistamines (eg, Clartie, Zyrtec) do not cross the blood brain barrier
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| stages of sleep | Stages 1-4, low amplitude, low frequency waves; stage 4 is deepest, happens about 2 times each night
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| REM sleep | high frequency, low amplitude waves; stage of sleep at which dreams occur; average 4 REM periods each night; resembles brain activity when awake
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| types of sensations | 1. conscious - somatic senses, special senses
2. subconscious - proprioception, visceral sensations
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| properties of sensation | conscious sensations - somatic, special senses
unconscious sensations - proprioception, visceral sensations
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| special senses | vision, hearing, smell, taste
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| sensory receptors | 1. photoreceptors
2. mechanoreceptors
3. chemoreceptors
4. thermoreceptors
5. nociceptors
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| photoreceptors | detect light; anaxonic (no axon); constantly releasing neurotransmitters
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| mechanoreceptors | respond to mechanical change, such as stretch, vibration, change in balance
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| chemoreceptors | respond to taste, odor, oxygen, carbon dioxide, changes in pH level of the blood
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| thermoreceptors | temperature, heat
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| nociceptors | pain, detection of potentially or actually harmful stimuli
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| sensory transduction | conversion of stimulus energy into a neuronal electrical signal; results in changes to membrane potential and possibly action potential if threshold is reached; all receptor potentials are depolarizing except photoreceptors
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| sensory receptor adaptation | decrease over time in the magnitude of the receptor potential when there is a constant stimulus;
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| receptive field of sensory neurons | physical location of sensory receptors; more receptors in an area results in greater sensitivity; larger fields have lower sensitivity than smaller fields; fingertips and lips are most sensitive
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| sensory integration | 3 neuron relay
1. first order neuron (detects stimulus)
2. second order neuron (first neuron entirely in CNS, crosses the midline)
3. third order neuron (thalamus, axon goes to appropriate primary sensory cortex
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| CNS role in sensation | processes sensory information and allows for response
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| tonic receptors | adapt slowly to constant stimulus; examples include proprioceptors, baroreceptors (blood pressure)
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| phasic receptors | adapt rapidly to constant stimulus
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| modality/labeled line coding | allows for dedicated, separate pathways for different sensations that do not share neurons
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| lateral inhibition | when an excited neuron inhibits its neighbors
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| nociception | detection of pain; sensation of noxious stimuli
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| noxious stimuli | chemical, mechanical or thermal stimuli that are harmful
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| neuropathy | loss or gain of sensation; can be either loss of sensation or gain in sensation (neuropathic pain)
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| Adelta fibers | fast transmitting, medium diameter, myelinated axons; phasic; result in sharp, intense, highly localized pain sensations
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| C fibers | slower transmitting, small diameter, unmyelinated axons; tonic; result in more delayed and persistent pain sensation or inflammatory response
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| pain response | 1. perception of pain
2. autonomic response (increased heart rate, sweating, blood pressure, dry mouth)
3. emotional response (fear, anxiety)
4. reflexive withdrawal
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| pain perception | fast/Adelta fibers; slow/C fibers
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| algesia | pain
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| hyperalgesia | increase in pain, overactive pain system (ex - shirt on sunburned skin)
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| analgesia | decrease in pain; can be due to natural pain suppression from periaqueductal gray, reticular formation and inhibitory interneurons or can be from a pharmaceutical analgesic
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| preiaqueductal gray | surrounds the cerebral aqueduct and releases endorphins and other internal opiode-type molecules
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| reticular formation | means by which pain sensations reach the cerebral cortex
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| referred pain | pain from visceral organs that is felt in other parts of the body; internal organs do not have own pain pathways, share wtih a second order neuron that is also stimulated by a somatic nociceptor
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| somatic motor neurons | motor neurons that are associated with voluntary actions
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| autonomic motor neurons | neurons associated with the Sympathetic Nervous System (SNS) and Parasympathetic Nervous System (pSNS)
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| Sympathetic Nervous System | "fight or flight" system; thoracolumbar division
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| Parasympathetic Nervous System | "rest and digest" system; craniosacral division
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| craniosacral division | Parasympathetic Nervous System; neurons are located in the brain stem and sacral region of the spinal cord
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| thoracolumbar division | Sympathetic Nervous System; neurons are located in the thoracic and lumbar regions of the spinal cord
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| autonomic reflexes | reflexes that affect internal organs; involves ganglia
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| ganglia | collection of cell bodies outside the CNS where information is transferred
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| preganglionic | cell body is located in the brain or spinal cord
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| postganglionic | cell body is located outside the CNS in a ganglion
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| target | cell that responds to a signal from a neuron; ganglion is located near the target in the pSNS, far from the target in the SNS
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| autonomic spinal reflexes | polysynaptic; includes micturation, defecation, penile erection
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| visceral functions that are not under antagonistic control | all under tonic control at rest; blood vessel dilation/constriction, sweat glands, liver/adipose tissue; penile erection and ejaculation is coordinated by both systems, but not antagonistic
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| neurotransmitters of SNS | pre-ganglionic: Acetylcholine
post-ganglionic: Norepinephrine
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| neurotransmitters of pSNS | pre-ganglionic: Acetlycholine
post-ganglionic: Acetlycholine
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| effectors of the autonomic nervous system | smooth muscle, cardiac muscle, exocrine glands, some endocrine glands, lymphoid tissue, adipose tissue
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| norepinephrine | released by postganglionic SNS neurons
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| adrengenic receptors | receptors that bind to epinephrine and norepinephrine; two types: alpha and beta
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| alpha receptors | type of adrenergic receptor (epinephrine or norepinephrine); broadly distributed in the body
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| beta receptors | type of adrenergic receptor (epinephrine or norepinephrine); not broadly distributed in the body; beta1 - heart, beta2 - respiratory system, bronchioles, beta3 - adipose tissue
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| examples of pharamcological substances that act as agonists for beta receptors | albuterol, isoproterenol
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| examples of pharamcological substances that act as antagonists for beta receptors | propranolol, metropolol
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| adrenal gland | located on the kidney; releases epinephrine when stimulated by a preganglionic sympathetic neuron
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| epinephrine | adrenaline
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| muscarinic receptor | type of cholinergic receptor (for Acetylcholine) that is found only in the pSNS; used by the target cell
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| variscosities | swellings of an axon that contain neurotransmitters; like beads on a string
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| hypoexcitable neuron | a hyperpolarized neuron that will require more than normal change to the resting membrane potential to reach threshold; due to hyponatremia nad hypokalemia
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| nicotinic receptor | type of cholinergic receptor (for Acetylcholine) that is found in both pSNS and SNS; used by the postganglionic neuron
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| examples of pharmacological substance that acts as an antagonist for a muscarinic cholinergic receptor | atropine
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