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Describe the Visual Central Pathway
Hyperpolarization ->action of rods-> alter synpatic activity with biopolar, amacrine, horizontal cell-> AP ganglion cells of optic N-> relay to thalamus nucleus LGN-> 1* visual cortex (occiptal lobe)
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Visual Transduction steps net result is a generation of ___________ in the ________ cells
- hyperpolarization via closing Na channels
- rod leading -> bipolar cells, amacrine cell, horizontal cells AP in the ganglion cells
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Tranduction of sound result in _________ of _________ cells which transmitt release _________ to fire AP to _________ nerve that synapse with____________
- depolarization of hairs cells
- spiral ganglion cells
- Cochlear branch of CN VIII (Vestibularchochlear N)
- Cochlear nuclei of medulla oblongota
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Prefrontal cortex
- on of the main Association cortex
- the homeostatic and sensorimotor systems are integrated into
- conscious thoughts
- Tertiary Motor Cortex- strating pt for output from the brain
- site of Working Memory ( short-term memory)
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Feedforward pathway
- 1>2>3>3>2>1
- sensory cortex > PTO> Prefrontal Cortex< 2* motor<1*motor cortexs(cerebal cortex highest motor heiarchy)> alpha motor neuron> skeletal muscle
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PTO
- posterior association cortex
- where parietal, temporal, occipital all abut each other
- association take the form of symbols & language
- "library"
- multimodal info process
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1* sensory input vs 2*
gets input from thalamus 2* doesn't
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Sensorimotor System
- perceiving the external world & moving the body (skeletal muscles) through the external world
- input - perception
- output- moving skeletal muscle through
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Homeostatic system
- perceiving the internal environment of the body & regulating the viscera via Endocrine & autonomic system
- input-perception of internal environment
- output- regulating via endocrine & autonomic
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Homeostatic adjustments effector organs
- cardiac muscles
- smooth muscles
- exocrine glands
- endocrine glands
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Gilia are ________. Ratio to neuron_________
- Astrocytes
- microglia
- Oligodendrocytes
- Schwann cells
- 10:1
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Astrocyte
- sustain neurons metabolically (nutrition) & trophically (growth)
- support them physically: structural function
- maintian extracellular fluid composition (uptake of K+)
- maintain blood-brain barrier
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microglia
scavenger immune cells in CNS
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Oligodendrocytes
myelination of CNS axon
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Schwann cells
myelination of PNS axons
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Blood Brain Barrier
tight junctions in capillaries prevent diffusion of substances from blood to brain extracellular space, except Water & Lipid soluble substances
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Dendrites
- input end
- reception of information as Graded potential
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Cell body
metabolisms, gene expression, protien synthesis, graded conduction
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Axon hiliock
site of generation of AP (action potential)
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Axon Terminal
- secretion of NT
- output end
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Cell that have the ability to conduct electricity along their plasma membrane
- neurons
- cardiac muscle cell
- skeletal muscle cell
- smooth muscle cell
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Neurons conduct electricity
- = change in membrane potential =flow of ions across the neuron's membrane
- because of ion channels
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Graded potential
- caused by ligand-gated channels (NT- ligand)
- take on any value
- come about b/c ligand gated ion channel stays open for a variable amout of time
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Action Potential (AP)
- fixed changes
- caused by voltage gated ion channels
- stay open for a fixed amount of time, allowing only the same amount of ions to pass each time the voltage gated channel is open
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What prevents the AP from propagating backward?
fast Na+ channels go to an inactive state after they close
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What are the steps in protein function during an AP
(Na+ and K+ channels)?
- high (-) V force keeps Na channel closed by 1st gate
- relatively (-) V force ( threshold) opens 1st gate Na+ enter
- high (+) V force close Na+ channel via 2nd gate Na channel is inactive
- relief of (-) V force open K gate hyperpolarization
- increase in (-) V force Na 2nd gate is replace by 1st gate
- High (-) V force membrane V keeps both Na & K closes
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Purpose of Myelin in comparison to nonmyelin
- to enhance the conduction of AP along the axon
- is an insulator
- depend on electric field and not on diffusion of ions
- fatty sheath
- nonmyelin is depend on distance of thershold to adjacent channels
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What keeps ion concentration constant on both sides a neuronal membrane__________? And at what point would this cease___________ ,what is the name of this condition?
- Na-K ATPase
- 3Na -out
- 2K -in
- requires ATP
- after 4 minute of brain deprived of blood flow Na and K are equilibrate
- ischemia --> why stroke cause death to neural tissue
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The greater the frequency of AP arrival to the synapse
- greater the influx of Ca2+
- more NT is released into synaptic cleft
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What is the sequence of events at a synapse
- Presynaptic ending - recieves AP ->increase perm. to Ca2+ ->exocytosis of NT from presynaptic vesiscles
- into Synaptic cleft-> interaction with NT with Postsynaptic cell NT receptors ->AP
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What is the difference between temporal & spatial summation?
- T- addition/subtraction of two synaptic inputs over a short time interval (happening sequentially)
- S- addition/subtraction of two synapt inputs occurring simultaneously but different location
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Excitatory vs. Inhibitory
- E- depolarization Na or Ca of postsynaptic cell
- I- hyperpolarization Cl influx or K efflux
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NT
- elicit EPSP or IPSP in postsyn. element via ligand gated ion channel
- Ach
- Glut- EPSP
- Asp-EPSP
- GABA -IPSP
- Gly
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Spine synapse
- post synaptic element forms a specialized extrusion
- cortical & hippocampal pyramidal neurons
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"En passant" synapse
- presyn element dose not terminate but exist along the course of the axon
- cerebellar granule cell axons
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Neuromodulator
- amplify or dampen the effectiveness of NT in either pre- or postsyn using 2nd messenger systemNO
- biogenic amines - NEPI, DO, EPI, histamine,
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Receptor subtypes
- Ultimately the body can use the same NT for different effects depending on where it binds in the NS or periphery
- Ex. EPI alpha1, alpha2, beta1, beta2
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Muscarinic vs Nicotinic
- both receptors Ach bind
- M-Gprotein receptor->everywhere else
- N- ion channel ->skeletal muscle
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Gray matter vs White matter
- G-structures made of cell bodies & dendrites
- clusters or sheets of neurons
- W-structures made of axons, fibrous texture,
- columns, nerves, commissures , fasciculus, lemniscus, peduncle
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Reticular Formation
- loose grouping of nuclei in brainstem involved in controlling levels of awareness and alertness of the brain
- make neuromodulators
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Brainstem
- involved w/ UNconscious reflexes of both a motor & homeostatic nature
- Pon
- Medulla
- Midbrain
- all 3 involved in motor coordination & organization of skeletal mus. movement
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Cerebellum
- exist @ level of brainstem
- involed in motor coordination & organization of skeletal mus. movement
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Thalamus
- Diencephalon
- relay station for conscious sensory input, regulation of states of arousal
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Hypothalamus
- Diencephalon
- regulation of endocrine system, autonomic system, & emotional rxns
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Subcortical Nuclei and their functions
- Basal ganglia- motor planning & conscious awareness
- Limibic system (Hippocampus & Amygdala) - memory
- emotions, drives (sex, hunger)
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What are visceral Inputs
- GI tract: Mechanoreceptors, gustatory sensation, chemoreceptors, nociceptors
- Cardio: bareoreceptors, stretch receptors, nociceptors, chemoreceptors
- Pulmonary system, Urogential system: stretch receptors
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What are the two main typees of procession for visceral inputs
- Reflex loop: mediate by spinal interneurons, relay to NTS, ->synapse w/ spinal cord, pontine, medulla-> efferents->ANS preganglia
- Central integration w/ senosrimotor system: relay to NTS->hypothalamus or limbic (amygdala) -> hormonal output
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Homeostatic outputs
- endocrine system via Hypothalamus
- ANS via NTS, hypothalamus, amygdala, & brainstem
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Thoracolumbar ANS
- Sympathetic NS
- preganglionic neurons at T & L level of spinal cord
- postganglionic neurons are in sympathetic trunck
- unified response
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Caniosacral ANS
- Parasympathetic NS
- preganglionic neurons is in Brainstem or Sacral spinal cord
- postganglionic neurons is close to effector organ
- localized/ discrete reponse
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Sensory Receptors
cells which transduce environmental energy into changes in membrane potential
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Stimulus
the energy form that activates the sensory receptor
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adequate stimulus
the type of energy to which a receptor best responds
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Doctrine of Specific Nerves Energies
activation of a specific type of receptor gives rise only to a single type of sensation
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Labeled-line Coding
sensory modalities are kept separate from one another in their assent to the brain
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Types of stimulus energy
- chemical -chemoreceptors
- light- photoreceptors
- thermal-thermoreceptors
- pressure, vibration, stretch, touch - mechanorecptors Ex. Somatosensation, auditory, vestibular
- pain- nociceptors
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The aspects of sensory input coded by the nervous system
- 1) Stimulus Type
- 2) Stimulus Location
- 3) Stimulus Duration
- 4) Stimulus Instensity
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Convergence vs Divergence
- C- many receptor axons synapse to a post-syn cell
- increase signal over a nosiy background
- D-single receptor axon synapses w/ many postsynaptic cells
- amplify the effect of the single receptor
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Lateral Inhibition
most active cells inhibit their neighbors, increases sensation contrast
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Somatosenstation
- Stretch
- Pain
- Temp
- Pressure
- Vibration
- Touch
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Dorsal Column Relay vs Anterolateral Tracts
- Both Ascending somatosensory tracts- sensations from R side body are processed in L side of Forebrain & vice versa
- D- cross-over in medulla
- touch, pressure, & vibration
- A-pain & temp cross-over in spinal cord
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Nucleus cuneatus
from arm, shoulders, neck
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Nucleus gracilis
legs & trunk
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Thalamus Nucleus of Auditory Relay vs Thalamus Nulecus of Visual Relay
- Vis- Lateral geniculate nucleus
- Aud- Medial geniculate nucleus
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Two component of Vestibular System
- Semicircular Canals- detects Angular acceleration of head
- Utricle & Saccule - detect Linear acceleration of head
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