Chapter 11 pt 1) Fundamentals of Nervous System Flashcards
1
Q
The Nervous System (Overview and Functions)
A
- Master control of the body
- Communicate via Electrical and Chemical Signals
- Signals are Rapid and Specific
- Response is usually immediate
- Three Functions of Nervous system
- Sensory Input) Gather information and through sensory receptores (affrent pathway)
- Integration) Processing and interpretation of sensory input (Control center)
- Motor Output) Activation of effector organs (muscles/glands). Produces a response. (effrent pathway).
2
Q
Two Divisions of the Nervous System
A
- CNS) Central Nervous System
- Brain and Spinal cord
- Inegration and Control Center. Determines motor output
- Prepherial Nervous System
- Any nervous tissue ouside of CNS
- Consists of nerves that extend from the brain and spinal chord
- Spinal nerve) connects to spine
- Cranial nerve) connects to brain.
3
Q
Prepherial Nervous System (Two Divisions)
A
- Sensory (Afferent) Division
- Somatic sensory fibers) convay inpulses from skin, muscles, and joints to CNS.
- Viseral Sensory Fibers) Convay Impules from visceral (internal) organs.
- Motor (Efferent) Division
- Transmits Impules from CNS to motor nuerons.
- Two divisions) Somatic and Autonomic
4
Q
Somatic Nervous System
A
- Nerve Fibers conduct impules from CNS to skeletal muscles
- Called the Voluntary Nervous System
- Concious Control of Skeletal Muscles.
5
Q
Autonomic Nervous System
A
- Visceral Motor Nerve Fibers
- Regulates smooth muscles, cardiac muscles, and glands
- Called the Involuntary Nervous system
- Two divisions
- Sympathetic) Fight Or Flight System
- Parasympathetic) Rest and Digest System.
- Two systems work oppiosite to eachother
6
Q
Histology of Nervous Tissue
A
- Nuerons) Excitible cells that transmit signals
- Nurogalieal cells) Support, protect and insulate Nuerons
- Four main types in CNS
- Astrocytes
- Microglial Cells
- Ependymal Cells
- Oligodendrocytes
- Four main types in CNS
7
Q
Astrocytes
A
- Most abundant, versitile, and highly branched galial ce;;s/
- Cling to nuerons, synaptic endings, and capaliries
- Many functions which include
- Support and Bracing of Nuerons
- Exchanges between capaleries and nuerons
- Guide Migration of Young Nuerons
- Control enviornment around nuerons
- Respomd to nerve impules and nuerotransmiters
8
Q
Microgalial cells
A
- Small, Ovoid Cells with thorny processes that touch and moniter nuerons.
- Migrate toward injured nuerons and can transform and phagocytize (remove) microrganisms and nueronal debris.
9
Q
Epedymal cells
A
- Line fluid filled cavities in CNS and provide a barrier between cerebrospinal fluid and other fluid
- Can be columnar or squamous, some are cilliated
10
Q
Oligodendrocytes
A
- Form thick Myelin Sheaths which insulare nerve fibers.
11
Q
Nueroglia In PNS
A
- Sataleite Cells) Surround nueron cell bodies in PNS
- Similar function to Astrocytes
- Schwann Cells) Completely surround prepherial nerve fibers and form mylin sheaths
- Similar function to oligodendrocytes
12
Q
Nuerons
A
- Structural Units of nervous system
- Last for a persons entire lifspan without dividing. (olfactory eptheliam does)
- All have a Cell body and one or more processes
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13
Q
Cell Body (Perikaryon or Soma)
A
- Biosynthetic Center
- Synthesises Protiens, Membranes, And Chemicals
- Done in Rough ER (Also called Nissil Bodies)
- Most are located in CNS
- Nuclei) Clusters of nueron cell bodies in CNA
- Ganglia) Clusters of Nueron Bodies in PNS
14
Q
Nueron Processes
A
- Extend from the body of the nerve
- CNS) Contains cell bodies and processes
- PNS) mostly cell processes
- Tracts) Bundels of nueron processes in the CNS
- Nerves) Bundles of nueron processes in the PNS
- Two types
- Axons and Dendrites
15
Q
Dendrites
A
- Short, tapering, branched processes
- Contain same organelles as cell body
- Recive (input) regoin of the nueron
- Never goes out
- Convay messages to cell body as Graded Potential
- Contain Dendric spines
- bulbous or spiky
- point of contact (synapse) with other nueron.
16
Q
The Axon (Structure)
A
- Only one per nueron. Attached to cone shaped area called Axon Hitchcock.
- Axon can be short or almost the entire length of the cell
- Some over 1 meter long
- Occasionally branched at a place called axon collaterals.
- At the ends of axons there are thousands of branches
- These brances are called Axon Terminals
17
Q
Axon (Funtions and Charcteristics)
A
- Conduction region of nueron
- Nuerons generate nerve impules and then transmit them along the cell membrane (axolemma) to Axon Terminal.
- Terminal) place that secretes nurotransmitters
- Nuerotransmiters excite or inhibit nuerons
- Lack Golgi apperatus and ER
18
Q
Transport On the Axon (2 ways)
A
- Molecules and Organelles are moved along axons by motor protiens in two directions
- Anterograde) away from the cell body
- EX) Midochondria, Cytoskeletal elements, membrane componants, enzymes.
- Retrograde) Toward Cell body
- EX) organelles that need to be destroyed, signal molecules, viruses, and toxins (to be destroyed)
19
Q
Myelin Sheath
A
- Myelin) protien-lipid substance that protects and electrically insulates the axon.
- Increases nerve tansmission speed
- Mylinated Fibers) Most long or large diamater Axons
- Nonmylinated Fibers) conduct impules more slowly.
20
Q
Mylenation in PNS
A
- Function of Schwarnn cells
- Cell coils around Axon and wraps itself tight
- Outer collar of Perinuclar Cytoplasm contains nucleus
- No protien channels or carriers so they are good at electrical insulation.
- Signal Jumps on Nodes of Ravier (gaps between adjacent Schwann cells)
21
Q
Myelination in CNS
A
- Formed by Oligodendrocytes but not the whole cell
- Each cell can wrap 60 axons at once
- Myelin sheath gap is present
22
Q
Structural Classification of Nuerons (3 types)
A
- Multipolar) Have three or more processes (one axon)
- Most common; major in CNS
- Bipolar) 2 processes, 1 axon and one dendrite
- Rare, (Retina and Olfactory Mucosa)
- Unipolar) 1 short T like process, 2 axons
- Also called psuedounipolar
- Prepherial Process) Associated with Sensory Receptor
- Central Process) Enter the CNS
- Found in Ganglia.
23
Q
Functional Classification of Nuerons
A
- Sensory (afferent) Transmit impulses from sensory receptors to CNS
- Motor (Efferent) Carry impulses from CNS to effectors.
- Multipolar. Most cell bodies are located in CNS
- Internuerons) Association Nuerons
- Between sensory and motor nuerons
- Shuttle signals through the CNS pathway. Most are in CNS
- 99% of the bodies nuerons are internuerons.
24
Q
Membrane Potentials
A
- Nuerons have a resting membrane potential that they can rapidly change
- Nerves respond to stimilus by creating an action potential (nerve impulse).
- Impulse is the same regardless of the channel it came through.
25
Roles of Membrane Ion Channels
* Leakage (nongated) channels) Always open
* Gated Channels) Protien changes shape to open
* When channels are open ions diffuse quicky across membrane.
* Diffuse doen chemical and electrical gradients. (electrochemical gradient)
* Three types
* Chemically Gated) Open when chemical binds
* Voltage Gated) Open in response to changes in membrane potential
* Mechanically Gated) open in close in response to receptors.
26
Resting Membrane Potential
* Of a resting nueron) -70mV
* cytoplamsic side is slightly negative
* actual voltage varries from -40 to -90 mV
* Membrane is said to be polarized
* Potential is made by
* Diffrences in ionic compisition of ECF and ICF
* Diffrences in plasma membrane permabiltiy.
27
Diffrences in Ionic Compisition
* ECF) has more Na+ than ICF
* Balanced by clorine ions (Cl-)
* ICF has higher concentration of K+ than ECF
* Balanced by negativly charged protiens.
* K+ plays the most improtant role in RMP
28
Diffrences in Membrane Permiability
* Impermiable to large, anionic protiens.
* Slightly Permiable to Na+
* Sodium diffuses into cell down concentration gradient
* Membrane is 25 times more permiable to K+ than sodium
* Potassium diffuses out of cell
* Permiable to Cl-
* More potassium diffused out than sodium goes in
* As a result the inside of the cell is more negavitve
* This charge makes RMP
* Sodium Potassium Pump
* Mantains concentration gradient of Na+ and K+
* Three Na+ pumped out and two K+ pumped in
29
Changing Membrane Potential
* Membrane Potential Changes when
* Ion concentration changes
* Membrane permiabilty to ions change
* Changes produce two signals
* Graded Potential) short distance signals
* Action Potential) long-distance axons
* Changes in RMP send, inegrate, and recive information.
* Changes in membrane potential are relative to RMP
* Deplorization) decrese in membrane potential
* Inside is less negative
* Impulse probability increases
* Hyperpolarization) Increase in membrane potential
* Inside is more negative
* Impule probability decreses.
30
Action Potential
* Long distance signal sending
* Occurs in mucle cells and Axons of nuerons
* Breif reversal of membrane potential with change in voltage. Carries signal long way
* Also refered to as a Nerve Impulse.
31
Four Steps of Action Potential
1. Resting State) All Na+ and K+ channels are closed
* Only leakage channels are open.
* Na+ channels have two voltage sensitive gates
* Activation gates) closed at rest
* Inactivation gates) open at rest, channel is blocked so Na+ can't enter
* K+ channel is closed at rrst
2. Deplorization) Na+ channels open
* Na+ rushes in and gates open
* Eventually all channels open (at -55 to -50 mv) and ICF is less negative.
3. Repolarization) Na+ channels inactivate and K+ channels open
* K+ exits cell down concentration graident
4. Hyperpolarization) Some K+ channels remain open
* Inside of membrane becomes more nagative
* causes slight hyperpolarization
* Once channels close Na+/K+ pumps restore orginal balance.
32
Graded Potentials
* Short Lived, Local messages that can die off
* Stronger the stimulus, the more voltage changes and the further the current flows.
* Trigegred by the stimulius that opens gated ion channels.
* Once channel opens, deplorization spread
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