Nervous System Flashcards
What is the primary function of the nervous system?
communication
What are the two anatomical divisions of the nervous system and what are they composed of?
CNS- brain and spinal cord
PNS- all neural tissue outside PNS
What are the three functions of the CNS?
- sensory data
- motor commands
- higher function of brain
What are the two functions of the PNS?
deliver sensory info and carry motor commands
When referring to the PNS, what does the afferent division refer to? What about the efferent division?
Afferent= from PNS to CNS
Efferent= from CNS to PNS
What are the three divisions of the PNS? What do they control?
- Somatic nervous system: controls voluntary actions (skeletal muscles)
- Autonomic nervous system: controls involuntary action (visceral organs)
3.Enteric Nervous System: controls gastrointestinal tract
What are the two efferent subdivisions of the ANS?
Sympathetic= fight of flight
Parasympathetic= rest and digest
What are the two general types of cells in the nervous system and what are their functions?
Neurons: cells that send and receive signals
Neuroglial cells: cells that support, insulate, and provide nutrients for neurons.
Dendrites
branched extensions of cytoplasm that conducte electrical signals toward cell body
Cell Body
contains nucleus, perikaryon
Axon
conduct nerve impulses away from cell body to another neuron, muscle, or gland
Cell bodies inside CNS
Nucleus
Cell bodies outside CNS
Ganglion
Axons and Dendrites in cylindrical bodies within CNS
tract
Axons and Dendrites found in cylindrical bodies outside CNS
Nerve
Axon Hillock
Where cellbody meets axon
Initial Segment
Area adjacent axon hillock where action potential is initiated
Synaptic terminal
bulb-shaped structure that contain synaptic vesicles. Filled with neurotransmitters.
Thre functional classifications of neurons
- Sensory neurons (afferent)
- Motor neurons (efferent)
- Interneurons
Anaxonic Neurons
found in brain and special sense organs
bipolar neurons
special sensory neurons found in retina
unipolar neurons
general sensory neurons of PNS (afferent fibers)
Mulitpolar nuerons
motor neurons found in typical spinal nerve (efferent fibers)
What is more common in the nervous system, neurons or neuroglia?
neuroglia
PNS glial cells
schwann cells and satellite cells
CNS glial cells
astrocytes, microglia, ependymal cells, oligodendrocytes
Astrocytes
florm blood brain barrier
microglia
engulf wastes and destroy microbs
ependymal cells
line ventricles of brain and central canal of spinal cord; produce, monitors and circulates cerebralspinal fluid
oligodendrocytes
produce myeline sheath around axons of neurons in CNS
What is the function of myelin, and what are myelin sheaths?
increases speed of action potential; gives axon white color
Nodes of ranvier
gaps between myelin sheaths
multiple sclerosis?
autoimmune disease myelin sheath in CNS attacked
White and gray matter
White= region of CNS with many myelinated tracts
Gray= unmyelinated areas of CNS
Diptheria
Caused by corynebacterium diphtheriae. Infects respiratory tract or skin. Releases toxin that damages schwann cells and destroys myelinsheaths of PNS
Guillain-Barre Syndrome
autoimmune disease, damages myelin sheaths that are produced by schwann cells in the PNS
five main membrane potential processes involved in neural activity
- Resting potential
- graded potential
- action potential
- synaptic activity
- information processing
Transmembrane potential
potential difference that results from the uneven distribution of positive and negative ions across the plasma membrane
concentration difference in sodium and potasium at resting potential
potassium concentrated inside cell
sodium concentrated outside cell
what passive forces are involved in causing the resting membrane potential
chemical gradients, electrical gradients, electrochemical gradients
Which direction does each ion want to go with regard to each passive force?
chemical gradient= K out Na in
Electrical gradient= K in Na in
Electrochemical- K out Na in
In mV what is the normal resting membrane potential inside the plasma membrane?
-70
Which ion can cross the plasma membrane easier?
K
What is equilibrium potential?
the transmembrane potential at which there is no net movement of a particular ion across the cell membrane
What is the active force that acts to balance the passive forces to maintain resting potential?
sodium potasium exchange pump
Depolarization
more positive then resting potential
repolarization
coming back to resting potential after depolaraization
hyperpolarization
more negative then resting potential
how does sodium rush into cell to change resting membrane potential?
opening a specific membrane channel
Two types of gated channels
- chemically gated (dendrites and somas)
- voltage-gated channels (axon)
When are passive and gated channels open?
passive- always open
active- open and close in response to stimuli
what are graded potentials and where do they occur in a neuron
variable-strength electrical signals that travel over short distances and lose strength as they travel away from source. greater the stimulus the bigger the change in the transmembrane potential and greater the area affected
how are graded potentials at the opposite ends of neuron linked together?
action potential
What is an action potential?
large, uniform electric signal that can travel great distance without loosing strength. occur in axons.
in mV what is considered threshold?
-60 to -55
generation of action potential
- depolarization to threshold
- activation of Na channels
- closing of Na voltage gated channels, opening of K voltage gated channels
- return to normal resting potential
electrical synapses
direct physical contact between cells
chemical synapes
signal transmitted across gap by chemical neurotransmitters
Excitatory neurotransmitters
cause depolarization of postsynaptic membranes
inhibitory neurotransmitters
cause hyperpolarization of postsynaptic membranes
cholinergic synapse
any synapse that releases ach
Postsynaptic potentials
graded potentials developed in a postsynaptic cell in response to neurotransmitters
excitatory postsynaptic potential
graded depolarization of postsynaptic membrane
inhibitory postsynaptic potential
graded hyerpolarization of postsynaptic membrane
temporal summation
repeated stimuli at one synapse
spatial summation
many stimuli arrive at multiple synapse.
