Ch.11 The Nervous System Flashcards Preview

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Flashcards in Ch.11 The Nervous System Deck (60):
1

Nervous System

receive sensory input, interpret it,
and send out appropriate commands

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3 interconnected functions:

sensory input, integration, motor output

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sensory input

conduct signals from sensory receptors

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integration

interpret sensory signals and formulation of response.

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motor output

conduction of signals to effector cells

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CNS consists of:

brain, spinal cord

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PNS consists of:

cranial nerves, ganglia, spinal nerves

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CNS

interpretation

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PNS

relay messages. afferent (sensory info in) and efferent (motor commands out).

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Efferent leads to:

somatic (voluntary movement) EAT A BANANA and autonomic (unconscious responses) DIGEST BANANA

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autonomic leads to :

parasympathetic (rest and digest) and sympathetic (fight or flight/ getting excited)

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two main cell types:

glial cells and neurons

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glial cells (neuroglia)

supporting cells that wrap around neurons

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neurons

transmit electrical signals

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CNS neuroglial cells (4 types):

Astrocytes, Microglial, Ependymal, Oligodendroctyes

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astrocytes (star,big)

support, transport glucose, metabolize neurotransmitters

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Microglial (small)

branched (processes). Immunity, macrophages (digest/ engulf/ breakdown)

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Ependymal

cilia, circulates cerebrospinal fluid (CSF). Cuboidal columnar. (cushoning) inbetween skull and brain

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Oligodendrocytes

generates myelin sheath.

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PNS Neuroglial cells (2 types):

Shwann Cells, Satellite Cells

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Shwann cells: (no arms)

flattened cells, wrap around axons that form myelin sheath in PNS

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Satellite cells: (flat, no arms)

flattened cells surround cell bodies to provide support framework.

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Neurons

structural unit of nervous system

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Neurons consist of :

dendrites, axon, myelin sheath, cell body (nucleus/ nucleolus), axon terminals

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Cell body (soma/ perikaryon):

Amitotic nature (repair not divide), Axon hillock (axon originates), Neurofibrils (intermediate filaments maintain shape)

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dendrites:

short, branching, pass electrical impulse on to cell body. electrical signals passed along GRADED POTENTIAL.

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Axons:

slender long processes, conduct electrical impulses. (collaterals= side branches)

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Axons 2 movements:

anterograde (towards axon terminus), retrograde (towards cell body).

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synapse:

gap between dendrites of one neuron and axon terminals of another neuron

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Myelination:

myelin sheath (insulates to protect elecritcal impulse from shorting out). White matter.

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Two cells giving rise to myelin sheath:

shwann cells in PNS and Oligodendrocytes in CNS

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Nodes of Ranvier:

myelin sheath gaps

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structural classification (3):

Multipolar, Bipolar, Unipolar.

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Multipolar

many dendrties, one axon (Most in CNS). purkinje fibres (heart), pyrimidal cells, granule.

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Bipolar

one fused dendrite and axon.

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Unipolar

one process emerging from cell body

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Nuclei:

CNS cluster of cell bodies on the neurons

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ganglia :

PNS cluster of cell bodies on the neurons

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Afferent

sensory

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Efferent

motor

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Interneurons

association neurons

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membrane ion channels:

leakage (always open), Gated Channels (chemically, voltage, mechanically)

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chemically gated channels:

open with the binding of specific neurotransmitters (sodium/ potassium)

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voltage gated channels:

open and close in response to membrane potential

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mechanically gated channels:

open and close to physically deformation of receptors

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resting membrane potential

K+ greater intracellular and membrane more permeable to K+ so "leaks" or diffuse out of cell. SODIUM POTASSIUM PUMP (moves K+ back into cell) And sodium moves in (pump moves it out) . -70mv

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polar

unequal sharing of electrons. (opp charges at both ends)

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polarization:

-70mv (depolarization) -80mv (hyperpolarization) -60 (repolarization)

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2 types of electrical signals :

graded potential, action potentials

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graded potential

decreases with distance travelled.

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action potentials

occurs in muscle cells. always the same "wave" regardless of stimilus. (DOES NOT DECREASE OVER TIME) de-polarizing, hyperpolarizing, polarizaing.

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4 stages of action potential:

resting state, depolarization, repolarization, hyperpolarization

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Resting state:

Na and K channels closed. activation gates closed / inactivation gates open.

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Depolarization:

moving up. Na+permeability increases; membrane potential reverses. Na+ gates open; K+ gates remain closed.

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Repolarization:

dropping back down to close. Na+ gates close, K+ gates open.

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Hyperpolarization:

"undershoot" takes a little while to close. K+ gates close.

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propagation of action potential:

constantly being attracted to the negatives. impulses will only travel in one direction away from the trigger zone.

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speed up impulse:

temperature (warmer), myelin sheath (insulation/ prevent leakage), larger diameter

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Synapses

as

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neurotransmitters:

bind to receptors and trigger opening or closing of ion channels. Examples: Acetylcoholine, Dopamine, Serotoni, GABA, Epineprhine.