Chapters 10-12 Study Guide Flashcards
What are the four general functions of the nervous system?
-Detect changes (sensory)
-Make decisions (integrative)
-Stimulate muscles and glands to respond (motor response)
-Maintain homeostasis
Describe the sensory division?
Utilizes sensory receptors to receive information and the relays that information to the CNS
Describe the motor division?
It is comprised of the somatic and the autonomic divisions. It puts decisions into action by carrying impulses to effectors (muscles/glands)
What are the names of the cell body of a neuron?
-Cell body
-Soma
-Perikaryon
What are the 9 structures of a neuron?
-Cell body
-Dendrites
-Axon hillock
-Axon
-Synaptic knob
-Schwann cell
-Myelin
-Myelin sheath
-Node of Ranvier
What are the five roles of neuroglia?
-Provide structural support
-Guide embryonic neurons into position
-Produce growth factors to nourish neurons
-Assists in the formation of synapses
-Clears excess ions and neurotransmitters
What are the four neuroglia of the CNS?
-Astrocytes
-Oligodendrocytes
-Microglia
-Ependyma
What are the two neuroglia of the PNS?
-Schwann cells
-Satellite cells
What are the five functions of astrocytes?
-Connects neurons to blood vessels
-Exchange nutrients and growth factors
-Form scar tissue
-Regulate ion concentration
-Part of BBB
What are the two functions of oligodendrocytes?
-Myelinate CNS axons
-Provide structural support
Describe microglia?
-Phagocytic cell
-Provide structural support
Describe ependyma?
-Line central canal of the spinal cord
-Line ventricles of the brain
-Regulates composition of cerebrospinal fluid (CSF)
-Made of ciliated cuboidal/columnar cells
What is the function of schwann cells?
Produce the myelin sheath found on some peripheral axons which speeds up nerve impulse transmission
What is the function of satellite cells?
Support clusters of neuron cells bodies (ganglia)
Describe sensory neurons?
Afferent neurons that carry impulses to the CNS. (unipolar but some are bipolar)
How are neurons classified?
By the number of extensions radiating from their cell body
What are the different classifications of neurons by type?
-Multipolar
-Bipolar
-Unipolar
Describe multipolar neurons?
-99% of neurons
-Many processes
-Most neurons of the CNS
Describe bipolar neurons?
-Two process
-associated with special senses (eyes, ears, nose)
Describe unipolar neurons?
-One process
-Cell bodies are in ganglia
-Sensory
What are the three classes of neurons by function?
-Sensory
-Interneurons
-Motor neurons
Describe sensory neurons?
-Afferent neurons
-Carry impulses to CNS
-Some are bipolar
Describe interneurons?
-Links neurons together
-multipolar
-located within the CNS
Describe motor neurons?
-Efferent
-Multipolar
-Carry impulses away from the CNS
-Deliver signals to effectors
How do neurons respond to stimuli?
-Neurons are excitable cells
-They detect stimuli and respond by changing their resting potential
-The common response is the opening of a gated ion channel
-The causes the resting potential to become less negative (depolarization)
-If depolarization reaches -55mV then the threshold potential has been reached and an action potential results
What are the five phases of neurons responding to stimuli?
-Resting potential
-Depolarization
-Repolarization
-Hyperpolarization
-Resting potential reestablished
Describe membrane potential and distribution of ions?
The resting membrane potential is the potential difference in charge across the axon membrane which is the -70mV being on the inside which means the membrane is polarized. The inside contains K+ (potassium) while the outside contains Na+ (Sodium) and Cl- (chlorine)
What are the eight steps that lead to an impulse conduction or the generation of an action potential?
- Nerve cell membrane maintains resting potential by diffusion of Na+ and K+ down their concentration gradients as the cell pumps them up the gradeints
- Neurons receive stimulation, causing local potentials, which may sum to reach a threshold
- Sodium channels in the trigger zone of the axon open
- Sodium ions diffuse inward, depolarizing the membrane
- Potassium channels in the membrane open
- Potassium ions diffuse outward, repolarizing the membrane
- The resulting action potential causes an electric current that stimulates adjacent portions of the membrane
- Action potentials occur sequentially along the length of the axon
What does all-or-none response mean?
If an axon responds at all, it responds completely with an action potential
All impulses carried on an axon are the ____ ____?
Same strength
Stimulus of greater intensity produces ____ ___ of action potentials, not stronger impulses?
Higher frequency
Threshold potential?
Level of potential at which an action potential is triggered in a neuron or muscle fiber.
Saltatory conduction?
Impulse conduction along a myelinated axon that seems to jump from one node to the next
How does conduction in myelinated and unmyelinated neurons vary?
Myelin helps increase the conduction velocity of a nerve impulse and uses saltatory conduction
Depolarization?
The membrane of a neuron becoming less negative (more positive) than the resting potential
Repolarization?
The process of a membrane becoming polarized once again
What are the two refractory periods?
Absolute refractory period and relative refractory period
Absolute refractory period?
Time when threshold stimulus cannot generate another action potential due to voltage-gated Na+ channels being unresponsive
Relative refractory period?
The time when only high-intensity stimulus can generate another action potential. This is when repolarisation is not complete and the membrane is still re-establishing resting potential
Neurotransmitter?
A chemical that an axon secretes into a synapse that stimulates or inhibits an effort (muscle or gland) or other neuron
Excitatory neurotransmitter?
A neurotransmitter that increases postsynaptic membrane permeability to sodium ions which bring the postsynaptic membrane closer to threshold
Inhibitory neurotransmitter?
A neurotransmitter that makes an impulse less likely to occur
Synapse?
A site at which a neuron transmits a nerve impulse to another neuron
Synaptic potential?
A change in the membrane potential of the postsynaptic cell
What is convergence?
Two or more presynaptic neurons forming synapses with the same postsynaptic neuron
What is divergence?
A single neuron having synapses with two or more post synaptic cells
Describe the structure of the spinal cord longitudinally?
The spinal cord is a slender column of nervous tissue that runs continuously with the brainstem.
-Begins at the foramen magnum
-Has a cervical enlargement
-Extends down through the vertebral canal and has 31 segments each of which branches into a pair of spinal nerves
-Has a lumbar enlargement
-Conus medullaris: terminates at L1 & L2 vertebrae
-Cauda equina: horse’s tail
-Filum terminale
Describe the structure of the spinal cord from a cross-sectional view?
Composed of gray and white matter and divided which looks like a butterfly in the center.
Center
-Anterior median fissure
-Central canal
-Gray commissure
-Posterior median sulcus
Gray (butterfly)
-Anterior horn
-Lateral horn
-Posterior horn
White (outside)
-Anterior funiculus
-Lateral funiculus
-Posterior funiculus
Surronding structures
-Ventral root
-Dorsal root
-Dorsal root ganglion
Functions of the spinal cord?
-Pathway for impulses to and from the brain
-Center for spinal reflexes
What is a refelx?
An automatic, subconscious response to stimuli within or outside the body
What is a reflex arc?
A neural pathway that consists of a sensory receptor + 2 or more neurons + an effector