Chapter 11 powerpoint Flashcards
sensory receptors
detects stimulus and sensory neurons convey message to control centers
integration
control center in brain/cord process/ interpret sensory input coordinate appropriate response to stimuli
motor
motor neurons send messages from control center to effectors to bring about response
neuroglia (supporting cells)
2 in PNS+ 4 in CNS
most have cell body w projections, each has a specific function
CNS Neuroglia
- Astrocytes
- Microglia
- Ependymal cells
- Oligodendrocytes
Astrocytes
- CNS
- most abundant
- act as scaffolding for neurons
- anchors neurons to capillaries
- maintain composition of interstitial fluid
- in embryos secrete chemicals that help neurons make connections
- recycle neurotransmitters
Microglia
- CNS
- small cells
- macrophages
oligodendrocytes
- CNS
- fewer projections
- projections form myelin sheath in CNS
Ependymal
- CNS
- Epithelium like
- simple cuboidal w/ cilia
- line the ventricles/central canals
- forms part of the choroid plexus (which produces cerebrospinal fluid)
- cilia beat and circulate CSF
PNS supporting cells
- satellite
- Schwann cell
Satellite cell
- PNS
- cling to surface of neuron cell bodies in ganglia
- function unclear
Schwann cells
- PNS
- form myelin in PNS
- insulate neuron axons- helps regenerate injured axon
- nodes of ranvier (1mm)
- neurolemma is outer nucleated cytoplasmic layer
myelinated
faster conduction of nerve impulse (white matter)
Neurons
nerve cells
- conduct electrical impulses
- extreme longevity
- amitotic (w/few except)
- fast rate of metabolism
cell body- Ganglia
collections of nerve cell bodies found in the PNS
cell body- Nuclei
collections of nerve cell bodies found in the CNS
processes- tracts
bundles of nerves cell processes found in the CNS
processes- nerves
bundles of nerve cell processes found in the PNS
- axons
- dendrites
axon
generate nerve impulses and transmits them
dendrites
main receptive or input regions
- 99% of neurons
- major neuron type in the CNS
- 3+ processes
multipolar neuron
- rare
- found in the special sense organs (eye, olfactory mucosa)
- 2 processes extending from opposite sides
Bipolar neurons
- found mainly in PNS
- most are sensory neurons
- single, short process extending from cell body and divides
unipolar neuron
neurons (functional classification)
- Sensory (afferent)
- message to CNs
- most unipolar - motor (efferent)
- message from CNS
- most unipolar - interneurons (association neurons)
- connect afferent and efferent neurons
- mostly multipolar
neurons communicate via?
electrical impulses and neurotransmitters
ion channels
allow ions to diffuse across membrane
Leakage channels
- never fully close, allows slow diffusion of specific ion
- there are more K+ leakage channels than there are NA+ leakage channels
gated channels
open and closed, when closed do not allow diffusion
- voltage
- gated
- mechanically
Voltage gated channels
open when membrane potential changes
Ligand gated channels
open when chemicals (like hormones/neurotransmitters) attach to them
mechanically gated channels
open and close in response to mechanical forces (like vibrations and pressure)
Graded potential
localized, short lived change in membrane potential occurs on dendrites and cell bodies
graded potential steps
- stimulus (heat, pressure) detected on cell body/ dendrites
- causes ligand or mechanically channels to open
- Depolarization or hyperpolarization of membrane
- change in potential ripples out from contact point
graded potential contl
- only initial stimulus open ion channel
- less effective as it moves away from contact point
- big stimulus causes more channels to open, bigger waves
- if change in potential reaches the axon hillock at enough strength, may cause action potential
action potential- nerve impulses
- graded potential reach hillock voltage gated channels to open
- Na+ rushes into cell
- membrane depolarizes that location
- @ -55mV potential propagates/ Na+ channels on adjacent membrane open
action potential (cont)
- Na+ channels open immediately followed by Na+ channel closing and K+ channel opens
- K+ rused out the cell
- membrane repolarizes
- repolarization (K+ channels on adjacent membrane open)
speed of transmission depends on
- Axon diameter
2. myelin sheath
Axon diameter
bigger diameter=faster transmission
A fibers
B fibers
C Fibers
A fibers
large diameter. go to skin, skeletal muscles, joints
B fibers
smaller diameter
- autonomic nervous system fibers
C fibers
smallest diameter
- autonomic nervous system
myelin sheath
Saltatory conduction faster (at nodes of ranvier)
- A& B myelinated, C is unmyelinated
synapses
(where neurons communicate w each other)
- electrical
- chemical
Electrical synapses
- neurons connected via gap junctions
- found in developing embryos and limited areas of adult brains
chemical synapses
-specialized for the release and reception of chemical neurotransmitters
activity at the chemical synapse
AP reaches axon terminal of presynaptic neuron
- Ca2+ voltage gated channels open
- Ca2_ floods into axon terminal
- exocytosis of neurotransmitters
- neurotransmitter crosses cleft and attaches to receptor
excitatory synapses
- Na+ and K+ channels open
- Na+ diffuses faster bc of higher gradient of Na+
- membrane depolarizes
- GRADED POTENTIAL
inhibitory synapses
-K+ channels open and K+ diffuses out or
Cl- channels open and Cl- diffuses in
neurotransmitters must be removed from cleft
- catalyzed by enzyme
- taken back up by presynaptic neuron or astrocyte
- diffuse away from cleft
(slowest part of neuron communication)
what is faster? a multisynaptic or single synaptic pathway faster?
SINGLE
neurotransmitters
Chemicals released by a presynaptic neuron into the
synaptic cleft and attaches to postsynaptic neuron where it causes some effect
Acetylcholine
used at skeletal neuromotor junctions and by autonomic and interneurons neurons
Dopamine ( a catecholamine)
Important in integrating emotions and skeletal muscle tone
Too little = Parkinson’s
Too much = schizophrenia
Serotonin (indolamine)
Involved in sensory reception, mood, appetite, sleep
endorphins-
-reduce our sense of pain
Provide the “runners high”
