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Chapter 48 Nervous System

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Ibtisam Matta

on 4 February 2014

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Transcript of Chapter 48 Nervous System

Cassidy Splawn
Ibtisam Matta

Ch. 48 Nervous Systems
Enjoy :D
This took a lot of Nerve!!!
Organization of Nervous System
Two Parts:
Central Nervous System (CNS):
Brain and spinal cord
Peripheral Nervous System (PNS):
Nerves connecting CNS to the body
Neurons: fundamental unit of nervous system
Nerve Nets: weblike system of neurons
Nerves: tight bundle of neuron fibers
Ganglia: cluster of nerve cell bodies
Complexity of the nervous system increases based on the complexity of the organism
Information Processing
Sensory Neurons: detect external stimuli (five senses) & internal conditions
info sent to CNS
Interneurons: analyze info then trigger a response
Motor Neurons: communicate response to effector cells
Effector Cells: Perform body's response to stimuli
Ion Pumps &
Resting Potential
Basis of all electrical signals in the Nervous System
Membrane Potential: difference in electrical charge across membranes
Resting Potential: potential of neuron not transmitting signals
Equilibrium Potential: when electrical gradient is in balance with concentration gradient
Gated Ion Channels
Neuron Structure
Parts of Neuron
Cell Body: main part containing organelles
Dendrites: branches that receive signals
Axons: long extensions that transmit signals between cell bodies
Hillock: region where signals are generated
Myelin Sheath: Electrical insulation for axon
Synaptic Terminal: where foreign axon connects to a cell
Synapse: signal transmission point between neurons
Neurotransmitter: chemical messenger (signal)
Supporting Cells
Glia: form structure of nervous system (10:1)
Ex. Myelin Sheath
Astrocytes: regulate concentration of ions and neurotransmitters
blood brain barrier: restricts passage of substances into the CNS
Radial Glia: in embryo form track for CNS-forming neurons
Oligodendrocytes (CNS) and Schwann Cells (PNS): form myelin sheath
Open/Close in response to three types of Stimuli
Stretch Gated: detect membrane deformity
Ligand Gated: respond to specific chemical
Voltage Gated: respond to membrane potential changes
Action Potentials
and Axons
Production of Action Potential
Action Potential: quick change in membrane potential(depolarization) that transmits signals
Depolarization: stimuli causes inside of membrane to decrease negativity
Hyperpolarization: stimuli causes inside of membrane increase negativity
Graded Potentials: changes that vary with the strength of the stimulus
Conduction of Action Potentials
Action potentials begin at cell body and travel to the postsynaptic cell along the axon
The action potential regenerates by the domino effect of depolarization along an axon
Saltatory Conduction: Nodes (area between myelin sheaths) are the only locations where depolarization can occur
Insulation (myelin sheaths) speed up this domino effect
Synaptic Vesicles: neurotransmitters packaged inside them
Presynaptic Cell: cell sending signal
Postsynaptic Cell: cell receiving signal
Synaptic Cleft: location between neurons where neurotransmitters are transferred
2 Types
Electrical Synapses: electrical current transmitted from cell to cell
Chemical Synapses: more common transmission of chemical neurotransmitters
Direct Synapses: Ion channel is opened by neurotransmitter
Indirect Synapses: Neurotransmitter binds to receptor that is not part of an ion channel and activates a signal transduction pathway.
Chemical Synapses
Action potential depolarizes synaptic membrane
Voltage gated Ca2+ channels open allowing influx of Ca2+
High Ca2+ concentration causes synaptic vesicles to fuse with the presynaptic membrane
These vesicles release neurotransmitters into the synaptic cleft
The neurotransmitters attach to the ligand gated ion channels of postsynaptic cells. K+ and Na+ can diffuse through the now open channels
The neurotransmitters release and synaptic transmission ends
Direct Synapses
2 Types
Excitatory Post Synaptic Potentials (EPSPs): brings membrane potential toward the threshold. Continues action potential.
Inhibitory Post Synaptic Potentials (IPSPs): bring membrane potential away from threshold. Stops action potential.
Post synaptic potential is not regenerated and occurs on cell body and dendrites not axon
2 types
Temporal: two postsynaptic potentials hit synapsis in succession, possibly causing action potential
Spacial: two postsynaptic potentials hit at two synapsis at same time possibly causing action potential
However EPSPs and IPSPs can counter each other
Indirect Synapsis
Amplifies signal to open and close many channels
Slower then direct synapsis but last longer
Activates signal transduction pathways
5 types
Acetylcholine: one of the most common, used in direct synapsis can cause both inhibitory and excitatory synapsis
Biogenic Amines: derived from amino acids, used in indirect synapsis (CNS), can affect sleep, mood, attention and learning
Amino Acids : used in direct synapsis, major inhibitor in brain
Peptides: in CNS used in indirect synapsis, control pain and are endorphins
Gases: used in CNS and PNS, released as regulator
Vertebrate Nervous System
Formation of the Nervous System
Fetus's Hollow Nerve Cord becomes...
Central Canal of Spinal Cord
Four ventricles of Brains
Cerebrospinal Fluid: circulates around canal and ventricles supplying nutrients and waste
Axons mylein sheaths appear as white matter (CNS)
Dendrites appear as grey matter in the (CNS)
Peripheral Nervous System
transmits information between CNS and body , regulates vertebrates movement and internal environment
Consists of.....
Cranial Nerves: originate in brain connect to upper organs
Spinal Nerves: originate in spinal cord and connect to lower organs
PNS Continued...
2 Parts that cooperate to keep homeostasis
Somatic Nervous System: Controls voluntary movements in skeletal muscles
Autonomic Nervous System: regulates internal environment, involuntary with three divisions
Autonomic Nervous System
Sympathetic: arousal and energy generating
Parasympathetic: calming and self maintenance functions
Enteric: digestive tract
Embryonic Development of the Brain
3 parts
Midbrain-receives and integrates sensory info and sends to forebrain, part of auditory and visual systems, controls arousal
Pons- participates and regulates medulla's actions, transmits info to brain
Medulla Oblongata-controls autonomic and homeostatic functions, instructions traveling from brain to spine switch in medulla
All info into and out of brain must pass through medulla and pons
Both work to coordinate large scale body movements and regulate sleep
Controls coordination
Error checks motor, perceptual, and cognitive functions
Involved in learning and remembering motor skills
Receives sensory info from joints, muscles, and from auditory and visual systems and motor commands from the cerebrum
Coordinates movement and balance
3 Pieces:
Epithalamus-cluster of capillaries that produce cerobrospinal fluid
Thalamus-input and output center for sensory info and sends to specific center of cerebrum
Hypothalamus-homeostatic regulation, contains body's thermostat, regulates body's basic survival systems, regulates mating behaviors, fight or flight response, and pleasure.
Circadian Rhythm
Internal timekeeper
Regulates hormone release, hunger, and heightened sensitivity to stimuli
In mammals it is controlled by a pair of hypothalamic structures the suprachiasmatic nuclei (cluster of nerves in the CNS)
Relies on external ques to stay in sync with the environment
Supports auditory and visual processing
Divided into right and left hemispheres
Outside is gray matter
Cortex-internal white matter and groups of neurons called basal nuclei (centers for planning and learning movement sequences)
Cerebral Cortex
Cerebral Cortex
Controls voluntary movement and cognitive function
Split into two hemispheres, each with four lobes
Functional areas include primary sensory areas and association areas
Primary Sensory Areas: Receives and processes specific types of sensory info.
Association Areas: integrate information from diff. parts of brain
Info. Processing
Primary Sensors send info. to Association Areas
Then brain generates motor commands through action potentials
Action Potentials travel from axon>brain stem>spinal cord>neurons>skeletal muscle
Portion of brain controlling body part proportion it skill needed to control it
Separation of functions to different hemispheres
Left Hemisphere
Math, logic, processing detail, and language
Right Hemisphere
Pattern recognition, spacial relations, emotions, non-verbal thinking
Two hemispheres work together, trade info back and forth (corpus callosum)
Language and Speech
Lymbic System: ring around brainstem, largest contributor to emotions
Attaches feelings to survival skills & gives us distinct mammalian behavior
Contains 3 parts of Cerebral Cortex
Amygdala: emotional memories form physical signs
Hippocampus: recall
Olfactory Bulb: receives odor info from nasal cavity
Interact with neocortex to make emotions that become behaviors
Frontal lobe controls primary emotions and personality traits
Memory and Learning
Short term memory is in the frontal lobe
Long term memory is in the hippocampus
When it's being thought about it can move to short term memory
Association of new info with old info makes for constant transfer between short and long term memory
Sensory and Motor Association Areas
Anterior left temporal: recognition of humans
Lower middle left temporal: recognition of animals
Lower posterior left temporal: recognition of tools
Memory and Learning cont...
Memorization: a fast process of strengthening existing neural connections
Long term learning: slow creation of new neural connections
Long term potentiation(LTP): an increase in strength of synaptic transmission when high frequency actions potentials are produced by presynaptic neurons
May be key to process of learning and memory storage
Consciousness: the emergent property of brain that integrates activities from all over the cerbral cortex
Injuries and Diseases
Nerve Cell Developement
During CNS development axons elongate
Growth Cone: growing region of axon
Adhesion Molecules: (on Growth Cone) attach to complimentary molecules on surrounding cells
Stem Cells: unspecialized cells that can form new brain neurons
Diseases of the Brain
Schizopharenia: episodes where patient cannot distinguish reality from
hallucinations, delusions
Bipolar Disorder: mood swings
Major Depression: low mood
Alzheimers: dementia, confusion, and memory loss age related and progressive
Parkinsons: diffuculty and slowness with movements
Action Potential
1.) Resting Potential: small # of K+ channels open, membrane potential at equilibrium
2.)Threshold: depolarizing of membrane (stimulus), Na+ channel opens, membrane potential at which action potential can first be generated
3.)Rising phase: after threshold additional Na+ channels open causing neuron to become positive
4.)Falling phase:Some Na+ channels close and some K+ channels open allowing K+ to leave cell (becomes more - charged)
5.)Undershoot: Na+ channels close and all K+ channels open causing neuron to move towards resting potential, becomes to hyperpolarized
Thalamus Neurons
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