Ch.11 The Nervous System Flashcards
Nervous System
receive sensory input, interpret it,
and send out appropriate commands
3 interconnected functions:
sensory input, integration, motor output
sensory input
conduct signals from sensory receptors
integration
interpret sensory signals and formulation of response.
motor output
conduction of signals to effector cells
CNS consists of:
brain, spinal cord
PNS consists of:
cranial nerves, ganglia, spinal nerves
CNS
interpretation
PNS
relay messages. afferent (sensory info in) and efferent (motor commands out).
Efferent leads to:
somatic (voluntary movement) EAT A BANANA and autonomic (unconscious responses) DIGEST BANANA
autonomic leads to :
parasympathetic (rest and digest) and sympathetic (fight or flight/ getting excited)
two main cell types:
glial cells and neurons
glial cells (neuroglia)
supporting cells that wrap around neurons
neurons
transmit electrical signals
CNS neuroglial cells (4 types):
Astrocytes, Microglial, Ependymal, Oligodendroctyes
astrocytes (star,big)
support, transport glucose, metabolize neurotransmitters
Microglial (small)
branched (processes). Immunity, macrophages (digest/ engulf/ breakdown)
Ependymal
cilia, circulates cerebrospinal fluid (CSF). Cuboidal columnar. (cushoning) inbetween skull and brain
Oligodendrocytes
generates myelin sheath.
PNS Neuroglial cells (2 types):
Shwann Cells, Satellite Cells
Shwann cells: (no arms)
flattened cells, wrap around axons that form myelin sheath in PNS
Satellite cells: (flat, no arms)
flattened cells surround cell bodies to provide support framework.
Neurons
structural unit of nervous system
Neurons consist of :
dendrites, axon, myelin sheath, cell body (nucleus/ nucleolus), axon terminals
Cell body (soma/ perikaryon):
Amitotic nature (repair not divide), Axon hillock (axon originates), Neurofibrils (intermediate filaments maintain shape)
dendrites:
short, branching, pass electrical impulse on to cell body. electrical signals passed along GRADED POTENTIAL.
Axons:
slender long processes, conduct electrical impulses. (collaterals= side branches)
Axons 2 movements:
anterograde (towards axon terminus), retrograde (towards cell body).
synapse:
gap between dendrites of one neuron and axon terminals of another neuron
Myelination:
myelin sheath (insulates to protect elecritcal impulse from shorting out). White matter.
Two cells giving rise to myelin sheath:
shwann cells in PNS and Oligodendrocytes in CNS
Nodes of Ranvier:
myelin sheath gaps
structural classification (3):
Multipolar, Bipolar, Unipolar.
Multipolar
many dendrties, one axon (Most in CNS). purkinje fibres (heart), pyrimidal cells, granule.
Bipolar
one fused dendrite and axon.
Unipolar
one process emerging from cell body
Nuclei:
CNS cluster of cell bodies on the neurons
ganglia :
PNS cluster of cell bodies on the neurons
Afferent
sensory
Efferent
motor
Interneurons
association neurons
membrane ion channels:
leakage (always open), Gated Channels (chemically, voltage, mechanically)
chemically gated channels:
open with the binding of specific neurotransmitters (sodium/ potassium)
voltage gated channels:
open and close in response to membrane potential
mechanically gated channels:
open and close to physically deformation of receptors
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
polar
unequal sharing of electrons. (opp charges at both ends)
polarization:
-70mv (depolarization) -80mv (hyperpolarization) -60 (repolarization)
2 types of electrical signals :
graded potential, action potentials
graded potential
decreases with distance travelled.
action potentials
occurs in muscle cells. always the same “wave” regardless of stimilus. (DOES NOT DECREASE OVER TIME) de-polarizing, hyperpolarizing, polarizaing.
4 stages of action potential:
resting state, depolarization, repolarization, hyperpolarization
Resting state:
Na and K channels closed. activation gates closed / inactivation gates open.
Depolarization:
moving up. Na+permeability increases; membrane potential reverses. Na+ gates open; K+ gates remain closed.
Repolarization:
dropping back down to close. Na+ gates close, K+ gates open.
Hyperpolarization:
“undershoot” takes a little while to close. K+ gates close.
propagation of action potential:
constantly being attracted to the negatives. impulses will only travel in one direction away from the trigger zone.
speed up impulse:
temperature (warmer), myelin sheath (insulation/ prevent leakage), larger diameter
Synapses
as
neurotransmitters:
bind to receptors and trigger opening or closing of ion channels. Examples: Acetylcoholine, Dopamine, Serotoni, GABA, Epineprhine.
