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Glial Cells
- 10-50 times more gila than neruons
- supporting cells
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roles of glia
- support
- clean up(dead cells and waste)
- regulation
- blood brain barrier
- nourishment
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(Glial)
Microglia
- folowing trauma they engulf and breakdown dead and dying neurons
- active following injuring, infection or stroke (like the wbc of the brain)
- little known of function at resting state
- role in diseases MS AIDS PD and Alzheimers
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Macroglia 3 types
- Oligodendroytes
- schwann cells
- astrocytes
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Olifodendrocytes and Schwann cells
- funtion: insulation of axons= myelin sheath
- Oligoes---CNS 15 axons
- schwann PNS only 1 axon
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Astrocytes
- function: Nutrients(provide and connect)
- BBB
- neurotransmitter removal
- clean up gets rid of scar tissue
- support
- CNS
- doesn't form mylien sheath
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Blood Brain barrier
semipermeable barrier produced by the cells walls of the capillaries in the brain
tight junctions between cells making it difficult for some substances to pass from the blood stream to the brain
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2 ways through BBB
Passive transport(diffusion)
- gases and water diffuse readily
- some drugs: loperamind vs morphine ...herion passes faster than morhpine
- alcohol
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through BBB
active transport
- energy sources: glucose, amino acids
- ions(na+ k+cl-)
- vitamins some hormones and peptiedes
- gets acrsoss through astroyctes
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BBB weak?
- BBB is weaker in some areas of the brains capillaries
- area postrem located in the brain stem(vomit reflex)
- pituitary gland(hormone release)
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Neurons
- basic unit of the nervous system
- specialized cells that recieve info and transmit it to other cells by conducting electrochemical impulses
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Neurons similarites to other cells
- Nucleus--dna
- endoplasmic reticulum--ribosomes
- mitochondrion--energy
- plasma membrane ---lipid bilayer studded with protein comples impermeable
- cytosketleton
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Shape (morphology) neruon
- Branching
- reflects communication property
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soma
cell body, nucleus, er, mitochondria
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dendrites
recipeients of messages from other neurons
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axon
simgle process that leaves the soma and carries messages to the trminal buttons (to other neurons )
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myelin sheath
insulation to carry message more efficeitly
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terminal buttons
branches at the end of the axon where neurotransmitters are releases
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synapse
junction between terminal button of one axon and teh membrane of anohter neroun
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Neurons: Energy requirement
- lots of mitochrodra
- need a lot of glucose and 02
- but have little ability to store enregy
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Neurons: Limited cell division
difference
- esp in adults
- don't replicate very often
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Nuerons functions
info processing an transmission
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Unipolor
- invertebraes --communication
- simpliest
- 1 primary process to many branches
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bipolor
- processing sensory neurons
- soma to 2 processes
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multipolar
- most common
- CNS spinal cord and brain
- single axon many dendrites
- multipolar interneuron don't have a defined axon signal motifiers to spinal cord
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sensory neurons
info from external environment
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motor neurons
CNS to muscles and glands
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Interneurons
- Lie completely in CNS
- Function: perceiving learning decision making complex behaviors
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Principle of dynamic polarization
electrical signals witin a neuron flow in one direction:from reveiving site to axon, From there AP is unidirectional axon to presynaptic terminal
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principle of connectional specificity
neurons do not connect indiscriminately with one another to form random networks each cell maes specific connections
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membrane potential
charge across the neurons membrane created by electrical polarization
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polariation
- outside of the neuron is postive inside is negative
- represented with - -(70mV)
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membrane potential
- resting membrane (-70mV)
- depolarization--increase in the membrane potential( inside becomes more like the outside ) towards 0 EXCITE
- hyperpolarization ---decrease in the membrane potential (inside becomes more negative) INHIBIT
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how is resting membrane potential created
- ions(charged particles) are balanced inside and outside of the cell
- cations:positvely charged
- anions negatively charged
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Passive diffusion
- membrane is somewhat permeable to NA=and K=
- na+ outside: force of diffusion want Na+ to come in
- k+ inside:force of diffusion want K+ to go out
- electostatic pressure: like repels like (electrostatic gradient )
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active transport
- na/k pump
- protein in cell membrane that moves k in 2 and na= in 3 using atp
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Resting Membrane potential
- net result of diffusion and na/k pump is resting membrane potential
- na outside wants in
- k inside wants out
- Na just waiting for the membrane permeability to increase
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action potential
- brief change in the permeability of the membrane such that the mebrane potential depolarizes
- stimuli from other neurons open ion channels
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Na in k out
- na channels open first and na rushed into the cell
- k channels open later and k rushes out of the cell
- the cell depolarizes
- (membrane potential becomes more positve more positive inside the neuron)
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return to resting potential
- when cell is depolarized
- na channels close
- k channels stay open though
- then the na/k pumps restores resting potential
- requires a lot of energy3 na go out 2 k pumped in
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Fun facts about neurotoxins and drugs
- na channels
- novocain, cocaine, lidocaine block na channels to prevent depolarzation (tempory and local)
- tetrodotoxin
- pufferfish, sewts and frogs
- permanent blockers of na channels
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cable properties
the passive conduction of electrical current in a decremental fashion, down the length of an axon
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saltatory conduction
conduction of action potentials by myelinated axons the action potential apperars to jump from one node of Ranvier to the next
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advantages of myelination
- energy
- a. less atp requried to pump na out and reset the system
- speed
- a. transmission under mylein sheath is much faster
- roughly 90 ms vs 10-20ms
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synaptic transmission
- when action potential reaches terminal buttons, what happens?
- electrochemical transmission ---electric=action potential
- chemical=neurotransmitters
- neurotransmitters chemicals that communicate between neurons at the synapse
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binding site
the location on a receptor protein to which a ligand binds
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ligand
a chemical that binds with the binding site of a receptor
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synaptic vesicle
a small hollow bead like structure found in terminal buttons, contains molecules of a transmitter
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ionotropic receptors
- ligand dependent ion channel
- ion channel that opens when a nT binds to it (fast) NT depended
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metabotropic receptor (G protein linked )
- receptor is adjacent to ion channels
- when nt binds it causes a cascade of intracellular events that open nearby ion channels (slower)
determine gender in babies ...digestion
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Turning off synaptic transmission
- reuptake=NT is taken up by the presynaptic cell via a membrane transporter
- metabolism(enzymatic degredation)=NT is broken down in the synapse
- autorecptors=resynaptic receptors that detect the level of NT in the synapse
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Communication between neurons
- intensity of nervous systems response is regulated by rate ( how many neryons fire )
- most neurons fire at a basal rate all the time (stimuli can excite--increase firing) or inhibit
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factors that influence firing rate
type of input
- excitatory post-synaptic potential(EPSP;+)
- inhibitory post-synaptic potential(IPSP;-)
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factors that influence firing rate
summation(temporal)
how many +- inputs the neruon recieves and whether they occur at the same time
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factors ......
Input's distance from axon
spatial summation
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dorsal
toward teh back, top of hand and back
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ventral
towards the belly
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rostral(anterior)
towards the face
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caudal(posterior)
towards the tail
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medial
toward the midline
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lateral
away from the midline
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coronal(transverse)
ear to ear
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sagittal
between the eyes
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horizontal
like taking off a hat
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contralateral
on opposite sides (vison)
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ipsilateral
on the same side
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CNS
brain and spinal cord
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PNS
- cranial nerves
- somatic ns
- autonomic ns
- sympatheicNS (fight or flight) increase pulse
- parasympathtic
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meninges
3 layers of protective sheaths around the CNS
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dura mater
- hard mother
- outer layer
- thick tough but flexible
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aracnoid membrane
- web like
- soft and spongy
- only in CNS
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pia matter
inner thin layer that continues around the NS
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PNS is covered with dura matter and pia mater only
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ventrical system
hollow spaces in the brain that contain CSF
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cerebrospinal fluid
clear fluid that fills the subarachnoi space and the ventricles of the brain and spinal cord
supports and protects teh brain from damage and its own weight
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Ventricular system
csf is produced by a special sturctre in the ventricles called the choroid plexus
- entire volume replaced every 6 hours
- fluid fills the ventricles and surrounds the brain
- desends into a tube in the center of the spinal cord central cannal
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flow of csf
- Choroid plexus
- lateral ventricle
- 3rd ventricle cerebral aqeduct
- 4th ventricle
- subaranoid space ---central canal
- arancoid villius /granulations
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spinal cord
links the pns to the brain(not the crainal nerves)
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white matter
axons carrying info up or down
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gray matter
cell bodies
Central canal=filled with CSF
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PNS
somatic body nervous system
- relay of sensory signals to cns and motor signals from cns to skeletal muscles
- sensory nerves--enter dorsal side of spinal cord
- motor nerves---exit ventral side of spinal cord
- cranial nerves--leave right to the brain
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PNS
Autonomic nervous system
- automatic
- regulates cardiac muslces smooth muscles and glands
- sympathetic NS fight or fligh energy use
- parasympathetic --resores/maintains homeostatis
- energy saving
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Endocrine system
System of glands that release hormones under the direction of the pituitary gland
Hormones --chemical messengers that travel through the bloodstrem(loose junctions..pitutary )
- Hormones can have effects on the CNS
- Can easily cross the BBB (feedback system)
- Bind to both
- Membrane-bound receptors
- Intracellular receptors (transcription factors… make new proteins)
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Hindbrain
Medulla
controling vital functions heart rat resp vomit cough sneeze reflexes muscle tones
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hindbrain
pons
- reticular formation--extends from medulla through the pons to midbrain
- controls sleep/wake cycle
- alterness to external stimuli
- norephinephrene projections throughout the brain
- raphe system(nuclie)--control of internal alertness
- mental vigilance
- serotonergic projections throughout the brain
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hindbrain
cerebellum
- coordinations of voluntary movement complicated motor movement
- imput from motor cortex spinal cord sensory neurons and inner ear
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midbrain
Tectum (above cerebral aqueduct)
Superior & inferoir colliculi--visual and auditory reflexes(something out of the corner of your eye)
Tegmentum (below cerebral aqueduct)
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Forebrain
- Cerebrum: cerebral cortex (bark)
- 4 lobes
- Frontal-judgement, iniciates movement
- Parietal--sensation
- Occipital--vison
- Temporal--hearing
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sulcus
- groove in the surface of teh cerebral hemisphere
- smaller than a fissure
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fissure
- major groove in teh surface of the brain
- long deep cut
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gyrus
- convoltion of the cortex of teh cerebral hemisphere separated by sulcus of fissure
- big bumps
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CNS
primary visual cortex
The region of the ___back of the brain upperand lower banks of calcarine fissure_ whose primary input is from the visual system.
primary auditory cortex
The region of the ___lower surface of lateral fissure__ whose primary input is from the auditory system.
lateral fissure--The fissure that separates the temporal lobe from the overlying frontal and parietal lobes.
primary somatosensory cortex
The region of the ___caudal to central suclus__ whose primary input is from the somatosensory system.
primary motor cortex
The region of the _posterial frontal lobe__ that contains neurons that control movements of skeletal muscles.
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Subcortical forebrain structures
- Corpus callosum = commissure
- connection between teh 2 cerebral hemisphers
Thalamus = sensory relay station (train station) connects body senses to the cerebrum
- Lateral geniculate nucleus = eye to CTX
- Medial geniculate nucleus = ear to CTX
- Hypothalamus
- involved in everything regulate temp and hormone production
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Subcortical forebrain structures
- limbic system(motivation, emotion, memory )
- amygdala( almond shaped, anterior temporal lobe)
- fear anger emotions defensive and agressive behavior at tip of hippocampus
hippocampus--learning declaritive momories shaped like a ram horn
fornix--connects hippocampus to other parts of the brain
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Subcortical forebrain structures
Basal Ganglia (3 seperate group of cells)
- Caudate nucleus
- Globus pallidus
- Putamen--important parts of the motor system control of balance and movement connected to substantia nigra
Connect to substantia nigra (nigrostriatal DA pathway) and motor areas of CTX
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