Chapter 2: Structure and Function of NS Flashcards
Neurons have three major external features
Axon, soma and dendrites
_____ are critical for neuron function.
Characteristics of the cell membrane
_____ provide vital support for neurons.
Glial cells
_____ is responsible for the cell’s resting potential.
Ion distribution
_____ are small, transient changes in membrane potential.
Local potentials
Sufficient depolarization at the axon hillock opens _____, producing an _____.
Voltage-gated Na+ channels; action potential
Drugs and poisons alter _____.
Axon conduction
The nervous system breaks into
PNS and CNS
CNS functioning is dependent on _____
Structural features
The CNS has six distinct regions reflecting _____
Embryological development
The cerebral cortex is divided into _____, each having primary, secondary, and tertiary areas.
Four lobes
_____ provide energy for the metabolic work of the cell.
Mitochondria
Axon terminals contain _____ that are released into the synapse between cells when the action potential arrives.
Synaptic vesicles filled with neurotransmitter molecules
The dendrites of a neuron are covered with minute spines that increase the receiving _____ of the cell. These spines are reduced in SIZE in individuals with intellectual impairment and reduced in NUMBER in those with schizophrenia.
Surface area
Thousands of receptors that respond to neuro-transmitters released by other neurons are found on _____.
Dendrites, dendritic spines, and soma of the cell.
The _____ is located at the juncture of soma and axon and is responsible for summation (or integration) of the multiple signals required to generate an action potential.
Axon hillock
Conduction of the action potential along the axon is enhanced by the insulating property of the _____.
Myelin created by nearby glial cells.
The nucleus of the cell is located within the soma, and _____ occurs there.
Protein synthesis
Transcription of the genetic code for a specific protein by mRNA occurs within the _____, and translation of the “recipe,” carried by the mRNA, occurs on the _____.
Nucleus - transcription
Ribosomes in cytoplasm - translation
_____ increase or decrease the production of particular proteins by activating transcription factors in the nucleus.
Changes in synaptic activity
_____ is the study of how environmental demands such as diet, environmental toxins, stress, prenatal nutrition, and many others turn on or turn off the expression of specific genes.
Epigenetics
Although epigenetic markers do not modify DNA, they can last a lifetime and may be transmitted to future generations. Two common markers are _____
DNA methylation and chromatin remodeling.
Derived from very early-stage embryos
Valuable as research tools and potential treatment for many diseases
Embryonic stem cells
Undifferentiated cells
Able to proliferate
Can become many different specific cell types
Stem cells
Embryonic stem cells that form the nervous system become two primary cell types:
Neurons and Glial cells
Convert physical stimuli into electrical signals.
Sensory neurons
Found in brain and spinal cord
Form interacting neural circuits
Responsible for conscious sensations, recognition, memory, decision-making, cognition
Interneurons
Direct bio-behavioral responses appropriate for the situation
Motor neurons
Cell body; contains nucleus and other organelles.
Soma
Projections from the soma that receive information.
Dendrites
Extension that conducts electrical signals from the cell body to the terminal buttons.
Axon
Receive information from other cells across the gap between them, the synapse.
Dendrites and soma
There are thousands of receptors on the _____.
Dendrites and soma
Effect on receiving cell may be _____ or _____.
Excitatory or inhibitory.
Can change shape rapidly in response to changes in synaptic transmission.
Dendrites and their spines are constantly modified
Mental illness, mental impairment, and drug addiction are associated with _____.
Lessening of dendritic spines
“Decision point” for the generation of the action potential
Axon Hillock
Located near dendrites or soma of neighboring cells
Vesicles located here
*Contain neurotransmitter chemicals
Terminal Bouton
A fatty insulation created by layers of glial cells.
Found on most neurons
Myelin Sheath
Myelinated peripheral nerves that serve muscles, organs, and glands.
Schwann cells
Myelinated nerves in the brain and spinal cord.
Oligodendroglia
Breaks in the myelin sheath
Sites at which action potentials are regenerated.
The myelin sheath increases speed of conduction along the axon
Nodes of Ranvier
Which part of the neuron performs most metabolic functions?
Soma
Neurons synthesize enzymes specific to synthesizing _____
Neurotransmitters
_____ may explain some phenomena, such as:
differences in monozygotic and dizygotic twins
persistence of the drug-taking behavior
the link between early abuse or neglect, and clinical depression.
Epigenetics
Sites of action of neurotransmitters, hormones, and drugs.
Receptors
Proteins that form a channel and which allow molecules to selectively and passively move across the membrane.
Ion Channels
Opens when a ligand (NT) binds to a receptor.
Ligand-gated channel (Ionotropic Receptor)
Opens when the electrical potential across the membrane is altered.
Voltage-gated channel
Glial cells:
_____
Form myelin sheaths in peripheral nervous system (PNS)
_____
form myelin sheaths in central nervous system (CNS
Schwann cells; Oligodendrocytes/oligodendroglia
Provide structural support for neurons
take up excess neurotransmitters.
Astrocytes
Remove dying cells responsible for immune response.
Microglia
Difference in electrical charge between inside and outside of cell.
Resting membrane potential
Inside of cell is more negative than the outside
It is _____.
–70 millivolts (mV)
Polarized
Moves 3 Na+ to the outside for every 2 K+ moved to the inside
Ions are pumped against their concentration gradients
Requires energy
Na+ - K+ Pump
Helping to keep the inside of the cell negative.
Na+ - K+ Pump
Rapid depolarization (movement toward zero) Is propagated down the length of the axon
The Action Potential
Threshold membrane potential for the generation of an AP is _____.
–50 mV
Voltage-gated Na+ channels open at the _____, generating the rapid change down the axon.
Axon hillock
If Na+ channels open, Na+ enters cell and causes _____.
Local depolarization
The following are examples of _____.
Cl– channels are stimulated to open, Cl– enters cell and inside of cell becomes more negative
If gated K+ channels open, K+ leaves the cell, the cell becomes more negative.
Local Hyperpolarization
Because neurotransmitters act on the postsynaptic membrane, the effects are called:
Excitatory postsynaptic potentials (EPSPs)
Inhibitory postsynaptic potentials (IPSPs)
Local potentials are _____.
The larger the stimulus, the greater the magnitude of _____.
Graded; hyperpolarization or depolarization
The Na+ channels close and cannot be opened for a fixed period
Absolute refractory period
Action potential lasts only _____.
1 millisecond
When Na+ channels _____, K+ channels _____,
K+ moves out of the cell and the membrane …
close; open
Returns to resting potential
The membrane overshoots resting potential and is hyperpolarized until excess K+ diffuses away.
Relative Refractory Period
Action potentials are _____
Intensity/strength _____
_____ is unrelated to amount of stimulation.
“All or none”
Doesn’t ∆
Size
Describes the propagation of the AP in a myelinated neuron
Conduction “jumps” from one node of Ranvier to the next.
Less energy is needed because Na+–K+ pumps are only at the nodes.
Saltatory conduction
Local anesthesia Blocks \_\_\_\_\_ (ex: Novocaine)
Voltage-gated Na+ channels
Two parts that make up the forebrain
Telencephalon and Diencephalon
Diencephalon breaks down into
Hypothalamus and thalamus
Telencephalon breaks down into
Basal ganglia, limbic system, neocortex
The mesencephalon is also known as the
Midbrain
The hindbrain is made up of…
Metencephalon
Myelencephalon
Myelencephalon is also called the
medulla
Metencephalon is made up of
Cerebellum and pons
