A&P Chapter 11 Flashcards
Nervous System functions
- receiving sensory input
- integrating information
- controlling muscles and glands
- maintaining homeostasis
- establishing and maintaining mental activity
Central Nervous System
brain and spinal cord
Peripheral nervous system
all nervous tissue external to CNS
- everything else (neurons in fingers and arms)
PNS - Sensory receptors
- end of neurons that detect stimuli (hot,cold, rough, smooth)
PNS- Nerves
bundles of axons
PNS- Cranial nerves
12 total and originate form the brain
PNS- Spinal nerves
31 pairs; originate form the spinal cord (branch on to both sides)
PNS- Ganglion
collection of cell bodies outside the CNS
PNS- Plexus
Extensive network of axons outside the CNS
PNS- Sensory Division (afferent)
- transmits action potentials from sensory receptors to CNS.
- cell bodies located in the dorsal root ganglion.
PNS- Motor Division (efferent)
- Transmits action potential to effectors
- divided into somatic (voluntary) and automatic nervous system
Division of PNS
Sensory(afferent : transmits action potential from receptors to CNS.
Motor(efferent): transmits action potential from the CNS to effectors (muscles, gland).
Neuron cell body
- contains centrally located nucleus
- extensive rough ER (nucleus is found here)
- organelle rich
- neurofilaments organize cytoplasm into different regions
- Nissl bodies are primary site of protein synthesis (make Protein)
Dendrites (receive)
- highly branched cytoplasmic extensions
- tapered bases at neuron cell body tips
- receive input from other axons of other neurons
- stimulation generates electrical currents
- dendritic spines
_ axons of other neurons from synapses
Axon(send)
- Propagate action potential
- trigger zone generates action potential
- terminate by branching into presynaptic terminals
- presynaptic terminals contain neurotransmitters
Sensory neurons
conduct action potential to CNS
Motor Neurons
conduct action potential away from CNS to muscles or glands (brain -> effector)
Interneuron
conduct action potential from neuron to neuron within the CNS
multipolar neurons
many dendrites and a single axon (brain)
bipolar neurons
one dendrite and one axon (down the arm)
Pseudo-unipolar neurons
single process extending from cell body (fingers)
Neuroglia of the CNS (supporting)
- major supporting cells of the CNS
- barrier between blood and neurons
- phagocytizes foreign substance
- produce cerebrospinal fluid
- form myelin sheath around axons
Astrocytes
- cover surfaces of blood vessels, neurons, and pia mater.
- extensive cytoskelaton
- regulate extracellular composition of brain fluid (what comes in and out)
- regular synaptic activity
ependymal cells
- line brain ventricles and central canal of the spinal cord
- produce cerebrospinal fluid in brain ventricles
- Cilia aids circulation of cerebrospinal fluid (major protectant of the brain and spinal cord)
Microglia
(between the brain and spinal cord)
- phagocytic in response to inflammation
- targets
- necrotic tissue
- microorganism
- foreign substances
- dying tissue and bacteria in the brain
oligodendrocytes
- extensions surround axons
- form insulating material
- myelin sheaths (insulation)
- quick nerve impulses
Neuroglia of PNS
Schwann cells(outside CNS) - myelinate axons Satelite cells - surround cell bodies in sensory ganglia - absorb heavy metals to protect
Myelination
- cytoplasmic extension that wrap axons
- protects axons
- electrically insulates axons
- increase speed of action potential
- not continuous
- Node of Ranvier (gaps in the myelin sheath)
White Matter
because of myelinated axons. Nerve tracts propagate actin potentials from one areas in the CNS to another. outer in spinal cord and deeper in the brain
Gray matter
unmyelinated axons, cell bodies, dendrites, neuroglia. Integrative functions. deeper in spinal cord and outer in the brain.
Leak ion channels
always open and ion specific.
gated ion channels
closed until opened by a specific signal from sodium or potassium, ion specific.
potential difference
charge difference across membrane
Resting membrane potential
permeability of resting membrane; difference in ion concentration
Depolarization
decrease in membrane potential due to reduction in charge difference.
Inside= -
outside= +
Hyper-polarization
increase in membrane potential due to decrease in charge difference.
Summation
one graded potential added to another; essential for action potential generation. Stronger stimuli, greater change.
Action potentials
electrical signal conducted from neuron to its target(effectors, brain, spinal cord). travel 1-2 milliseconds to occur.
Phases: re-polarization and depolarization.
Strong grade potential
reaches threshold. all permeability changes proceed w/o stopping. Stronger stimuli, stronger graded potential.
Weak graded potential
doesn’t reach threshold. permeability changes stop; returns to resting potential. Not sent to next signal.
Absolute Refractory
complete insensitivity to stimuli.
Relative refractory period
a stronger than threshold response can induce action potential.
Propagation of action potentials
Unmyelinated cells: action potential adjacent to original.
Myelinated cells: action potentials conducted between nodes of Ranvier due to lipids(saltatory conduction) can jump form myelinated cell to myelinated cell.
Nerve Fiber Types - Type A
large diameter, myelinated. conduct at 15-120 m/s. Motor neurons supplying and most sensory neurons. (fingertips[heat,pressure, temp], balance and coordination)
Nerve Fiber Types- Type B
Medium diameter. lightly myelinated. Conduct at 3-15m/s. part of ANS. quickest sensory neuron.
Nerve Fiber Types - Type C
Small diameter, unmyelinated. Conduct at 2 m/s or less. Part of ANS. Autonomic digestive system and organs
Presynaptic cell
transmits signal to synapse (heart and intercalated disks.
Postsynaptic cells
cell that receives the signal.
Presynaptic terminal
end of an axon
Synaptic cleft
space separating axon and adjacent cell
postsynaptic membrane
membrane opposed postsynaptic cell.
Excitatory post-synaptic potential
when depolarization occurs;may meet threshold for action potential.
Inhibitory post-synaptic potential
hyperpolarization is inhibitory. Decreases likelihood of action potential.
Axoaxonic Synapses
axons synapse with presynaptic terminal of another .
one axon can modulate neurotransmitters of other axons.
Presynaptic inhibition
reduction in neurotransmitter
presynaptic facilitation
increase in neurotransmitter production.
Spatial summation
multiple presynaptic action potentials reach same postsynaptic neuron.
Temporal summation
multiple action potential at single presynaptic terminal.
Convergent pathways
many converge and synapse with smaller number of neurons
Divergent pathways
small number of presynaptic neurons synapse with larger number of post synaptic neurons
Oscillating circuit
outputs cause reciprocal activation
