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Final
Ch 11
56
Anatomy
Undergraduate 2
12/11/2007

Additional Anatomy Flashcards

 


 

Cards

Term
Sensory function of Nervous System
Definition

- receive information about external & internal surroundings
- transmitted to brain & spinal cord via sensory neurons

Term
Integrative Function of Nervous System
Definition

- process & store information
- make decisions
- in spinal cord and brain
- via interneurons: w/in brain & spinal cord that take incoming info and may decide to store info for later or induce a motor function

Term
Motor Function of Nervous System
Definition

- send commands to effectors
- via motor neurons

Term
CNS
Definition

- brain and spinal cord
- integration centers

Term
PNS
Definition

- cranial (12 pairs) & spinal (31 pairs) nerves part of neuron that sends signal

- ganglia

- sensory receptors

Term
Sensory Division of PNS
Definition

- signals to the CNS

 

i.  Somatic Sensory Division

 

ii.  Visceral Sensory Division: associated with organs; ie stomach is full and brain reacts with secretions etc

Term
Motor Division of PNS
Definition

- signals from CNS to effectors

i.  Somatic Nervous System (SNS)
- to skeletal muscles
- voluntary control & somatic reflexes

ii.  Autonomic Nervous System (ANS)

- to glands, cardiac muscle, & smooth muscle
- involuntary/visceral reflexes

a.  Sympathetic Division
- arouses body for action
- “ fight or flight”

b.  Parasympathetic Division

                   - calms the body
                   - “rest & digest”

Term
Enteric System of PNS
Definition
- enteric plexuses of digestive tract
- somewhat independent
- monitors digestive tract
- stimulates contraction of smooth muscle & glandular secretions of the digestive tract
Term
Functional Properties of Neuron
Definition

 

1.  Electrical Excitability: High degree of ability to respond to some kind of stimulus (external to the cell)

 

2.  Conductivity: convert response into an electrical signal; generate action potential

 

3.  Secretion: associate with synapse (place where signal is transferred from one cell to the next)

Term
Cell Body
Definition

- control center

- nucleus and other organelles

- Nissl bodies (rough ER): centers of protein synthesis; show up darkly

- neurofibrils

- cytoplasmic inclusions

- no mitosis

Term
Dendrites
Definition

-  branched processes: a lot of surface area

-  processes that emerge from cell body

-  primary sites for receiving signals

- may have 1-1000s
Term
Axon
Definition

- conducting zone

- mostly unbranched process
- emerges from cell body
- propagates nerve impulse: special ion channels that are not in the soma

- wide range in length
- no rough ER/no protein synthesis
- axoplasm & axolemma

- axon hillock where joins cell body
- initial segment & trigger zone

- axon collaterals may be present: branch offs at a 90 degree angle to activate more than one neuron

- axon terminals at distal end

- synaptic knobs/vesicles filled with neurotransmitter
Term
Axonal Transport
Definition
- anterograde transport from cell body into axon and along axon (neurotransmitters)
- retrograde transport to cell body – waste products
- travel occurs along microtubules
Term
Multipolar Neurons
Definition

one axon and multiple dendrites

 

- motor neurons & interneurons

Term
Bipolar Neurons
Definition
one axon and one dendrite

- neurons in some sense organs
Term
Unipolar Neurons
Definition

a single process leading away from cell body

 

- process branches
- both branches function as axon

- branches into dendrites at distal end

- axon terminals/synaptic knobs in CNS
- sensory neurons

Term
Anaxonic Neurons
Definition
multiple dendrites but no axon: do not produce action potentials; in brain, very limited
Term
Purkinje Neurons
Definition
that has a distinctively patterned dendrite
Term
Pyramidal cells
Definition
not sphere shaped; cerebral cortex
Term
Neuroglia
Definition

supportive cells


- protect neurons & assist in their function
- smaller & more numerous
- not electrically active
- can multiply & divide

Term
Gliomas
Definition
brain tumors
Term

Astrocytes in CNS

Neuroglia 

Definition
- many-branched
- most numerous type
- provide physical support for neurons
- involved in blood-brain barrier
- regulate embryonic development of brain
- maintain appropriate chemical environment
- may influence formation of neural synapses
Term

Oligodendrocytes in CNS

Neuroglia 

Definition

- forms myelin sheath around multiple neurons – cell wraps around neuron

- insulates axon

Term

Microglia in CNS

Neuroglia 

Definition
- macrophages - phagocytes
- phagocytize dead tissue, microbes, etc.
- concentrated in areas of damage
Term

Epindymal Cells in CNS

Neuroglia 

Definition

- lining of internal cavities of brain & canal of spinal cord

- produce & circulate cerebrospinal fluid – they secrete this

- cilia & microvilli on apical surface
- blood-cerebrospinal fluid barrier

Term

Schwann Cells in PNS

Neuroglia 

Definition
- forms myelin sheath around axons
- assists in regeneration of damaged axons
Term
Satellite Cells in PNS
Neuroglia
Definition

- surround cell bodies in ganglia
- may regulate exchange of materials with extracellular fluid

Term
Myelin Sheath in PNS
Definition

- electrically insulates axon

- consists of p.m. of glial cells

-  many Schwann cells per axon
- spiral repeatedly around the axon – like squeezing up a toothpaste tube, you wrap the outside as the inside stuff moves along

- neurilemma is thicker, outer layer
- nodes of Ranvier are gaps – regions of axon that are not insulated

- internodes are myelin-covered segments – are insulated

Term
Myelin Sheath in CNS
Definition

- electrically insulates axon

- consists of p.m. of glial cells

- each oligodendrocyte partially myelinates several axons

          - no neurilemma

- Nodes of Ranvier are present

Term
Multiple Schlerosis
Definition

degenerative disorder of myelin sheath in CNS

Oligodendrocytes are destroyed and replaced with sclerotic (scar) tissue, could be autoimmune

Term
White Matter
Definition
bundles of myelynated axons, on outside of spinal cord
Term
Gray Matter
Definition
neuron cell bodies and dendrites and unmyelynated axons
Term
Electrical Potential
Definition
difference in [  ]  of charged particles 
Term
Electrical Current
Definition
: flow of charged particles
Term
Resting Membrane Potential
Definition

- electrical voltage – degree of separation from + and - charge

 - enables electrical current/ion flow to occur

Term
Ion Channels
Definition

- some gated
- electrical currents can be turned on and off
- current flows across membrane thru ion channels

- electrochemical gradient

- can change membrane potential

Term
Leakage Channels
Definition

Ion Channel?

- more K+ leakage channels than Na+ leakage channels in p.m.
- membrane more permeability to K+ 

Term
Voltage Gated Channel
Definition

Ion Channel?

 

-Typically associated with axon

- respond to change in membrane potential

- participate in generation & conduction of action potentials

 

Term
Ligand Gated Channel
Definition

Ion Channel?

 

- respond to chemical stimuli

- such as neurotransmitters
- on dendrites & cell bodies of interneurons & motor neurons

 

Term
Mechanically Gated Channel
Definition
Ion Channel?

- respond to mechanical stimulation (ie sound waves, feelings in skin)
- typically associated with sensory receptors

Term
Resting Membrane Potential
Definition

- typical in a neuron is -70 mv

- due to unequal distribution of various ions in EC fluid & the cytosol:
- EC fluid rich in Na+ and Cl-
- cytosol rich in K+ and other anions (other ions that can’t pass through membrane
à too large, negative charge)

Term
Formation of Resting Membrane Potential
Definition

- K+ tends to diffuse out of the cell along concentration gradient (anions don’t go with)

 

- inside of membrane becomes increasingly negative

 

- K+ is attracted back in along its electrical gradient & reaches equilibrium


- inward leakage of Na+ is slow, but counteracts negative voltage

- Na+/K+ pumps offset the inward leakage of Na+ -- 3+’s out 2+’s in

- Na+/K+ pump has electrogenic effect

- net effect of ion flows & pump action produces a RMP of about –70 mV

Term
Graded Potentials
Definition

- small deviation from membrane potential


- response to ligand or mechanically-gated channels

 

- vary in amplitude & strength

 

- produces a localized flow of current that dies out quickly


- may be excitatory or inhibitory – hyperpolarize the cell; excitatory is something that depolarizes neuron

Term
Action Potentials
Definition

- sequence of rapidly occurring events
- 2 phases:  depolarizing and repolarizing
- during depolarizing phase: membrane potential becomes positive
- during repolarizing phase: resting membrane potential is restored -70
à +30, then back to -70
- involves 2 types of voltage-gated channels in p.m. of axolemma and axon terminals
- Na+ channels open first & allow Na+ to flow in - depolarize
- K+ channels open next & allow K+ to flow out - repolarize
- all-or-none principle applies – amplitude/strength is always the same
- travel long distances without dying out

Term
Depolarizing Phase
Definition

i.  Depolarizing graded potential causes membrane to depolarize to threshold (-55 mV)

ii.  Activation gates of voltage-gated Na+ channels open rapidly

iii.  Na+ flows into cell along favorable electrical and chemical gradient
à  causes further depolarization à more Na+ channels open (positive feedback)

 

iv.  Inactivation gates of voltage-gated Na+ channels close

 

Effect:  Membrane potential changes to +30 mV

Term
Repolarizing Phase
Definition

i.  Voltage-gated K+ channels begin to open at threshold but open slowly à become active when voltage-gated Na+ channels are closing

ii.  Na+ inflow slows and K+ outflow accelerates

Effect: Membrane potential changes to -70 mV

iv.  Outflow of K+ may lead to hyperpolarizing phase

 

Effect: Membrane potential drops to -90 mV


- Na+ voltage-gated channels return to resting state during repolarization

 

- Na+/K+ pump restores ionic concentrations associated with the resting state

Term
Refactory Period
Definition

-  time during which excitable cell cannot generate an AP
- absolute refractory period:

- no stimulus can initiate a second AP
- when voltage-gated Na+ channels are activated (both gates open)  and inactivated (inactivation gate closed)

- relative refractory period:
- stronger stimulus needed to initiate a second AP
- when voltage-gated K+ channels still open but voltage-gated Na+ channels are in resting state (inactivation gate open & activation gate closed)

Term
Propagation of Nerve Impulses
Definition

- nerve impulses arise at trigger zone
- propagated/conducted to axon terminal – like domino effect

- involves positive feedback:

depolarization in one region à triggers opening of voltage-regulated Na+ channels in adjacent segments à that segment depolarizes and produces AP à triggers opening of Na+ channels in adjacent segment à that segment depolarizes & produces AP à process repeated to distal end of the axon

-ion flow is not across the membrane, but along membrane

- refractory period prevents travel backwards

Continuous propagation:

- you trigger a.p.’s at very short distances away from previous a.p.

- occurs in muscle fibers & unmyelinated axons

- voltage-regulated ion gates along entire length of axon
Term
Saltatory Conduction
Definition

- occurs in myelinated axons – covered with myelin sheath w/occasional gaps
- voltage-gated channels unevenly distributed
- few in regions covered by myelin sheath

- many at nodes of Ranvier
- current flows across membrane & APs produced at nodes
- electrical current flows thru EC fluid & cytosol from node to node


- effects of saltatory conduction:

 

1.       faster conduction of signal – current is much faster than a.p.’s

2.  more energy-efficient method of conduction
Term
Removal of Neurotransmitter with Diffusion
Definition

- enzymatic degradation
- uptake by presynaptic neuron or neuroglia

- therapeutic drugs work by removing a neurotransmitter or blocking one
Term
Summation
Definition

- integration of inputs to postsynaptic neuron

- additive effect
- occurs at trigger zone
- spatial summation
- temporal summation

- may result in Excitatory Post-Synaptic Potential, nerve impulse, or Inhibitory Post-Synaptic Potential

Term
Neurotransmitters
Definition

- usually small, organic compounds such as

1.  Acetylcholine – at neuromuscular junctions, and in brain
2.  Amino acids
3.  Modified amino acids – Epinephrine, Norepinephrine, Adrenaline, Noradrenaline
4.  Neuropeptides – Chain of amino acids (2-40)

 

- characteristic features:

 

1.  synthesized by presynaptic neuron

2.  released in response to stimulation

3.  bind to specific receptors on postsynaptic cell

4.  alter physiology of postsynaptic cell

 

- effect of neurotransmitter varies with the type of receptor on postsynaptic cell
Term
Neuromodulators
Definition

Modifying the Effects of Neurotransmitters

- various chemicals may stimulate or inhibit

            i.    neurotransmitter synthesis

ii.                  neurotransmitter release

iii.                neurotransmitter receptors

iv.                 neurotransmitter removal

Term
Neural Circuits
Definition

- functional groups of neurons
- organized into types of networks

1.  Simple series circuit: linear

2.  Diverging circuit: single presynaptic neuron synapses with several postsynaptic neurons

3.  Converging circuit:  several presynaptic neurons synapse with a single postsynaptic neuron

4.  Reverbrating circuit:  simple series circuit with branches that synapse back to earlier neurons in circuit

5.  Parallel after-discharge circuit:  divergence followed by asynchronous convergence
- single presynaptic neuron synapses with several postsynaptic neurons
- this produces multiple separate circuits of differing length
- each circuit arrives at common postsynaptic neuron at a different time

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