chapter 11 Flashcards
Controls our perception and experience of the world
Nervous System
Includes brain and spinal cord
CNS
Made up of billions of nerve cells or neurons; protected by the bones of skull
Brain
begins at foramen magnum and continues through vertebral foramina of first cervical to first or second
lumbar vertebra
Spinal Cord
consists of all nerves in body outside protection of
skull and vertebral column
PNS
gather information about internal and external
environments of body; input is gathered by sensory or afferent division of PNS; further divided into somatic and visceral divisions; Sensory input from both divisions is carried from sensory receptors to spinal cord and/or brain by spinal and cranial nerves
Sensory Functions
consists of neurons that carry signals from skeletal muscles, bones, joints, and skin; also transmits signals from organs of vision, hearing, taste, smell, and balance; sometimes called special sensory division
Somatic Sensory Division
consists of neurons that transmit signals from viscera (organs) such as heart, lungs, stomach, kidneys, and urinary bladder
Visceral Sensory Division
analyze and interpret
incoming sensory information and determine an appropriate response
Integrative Functions
actions performed in response to integration; performed by motor or efferent division of
PNS; can be further subdivided into somatic and autonomic divisions, based on organs that neurons contact
Motor Functions
consists of neurons that transmit signals to skeletal muscle
Somatic motor division
Visceral motor division
Autonomic Nervous system
caused by poliovirus; infection that impacts CNS and especially spinal cord
Poliomyelitis
make up over 99% of all neurons
Multipolar Neurons
with one axon and one dendrite and a cell body between them; found in eye and olfactory epithelium in
nasal cavity
Bipolar Neurons
carry information toward CNS;
Sensory or afferent neurons
relay information within
CNS between sensory and motor neurons; make up most of neurons in body; multipolar, communicating with many other neurons
Interneurons or association neurons
carry information away from cell body in CNS to muscles and glands; mostly multipolar
Motor or efferent neurons
composed of repeating layers of plasma membrane
of Schwann cell or oligodendrocyte in PNS and CNS respectively
Myelin Sheath
process that forms myelin sheath from plasma
membranes of neuroglial cells; wrap themselves around axon
forming multiple layers of membrane
Myelination
segments of axon that are covered by
neuroglia
Internodes
gap between adjacent neuroglia; where myelin sheath is absent
Node of Ranvier
composed of myelinated axons that
appear white
White matter
originate
in brain; most are gliomas
Primary brain tumors
composed
of neuron cell bodies,
unmyelinated dendrites
and axons that appear gray
Gray matter
exposure to ionizing radiation
and certain diseases
Predisposing conditions
varies with tumor type, age, and health of patient;
generally involves surgical removal of mass with chemotherapy
and perhaps radiation therap
Treatment
travel short distances
Local Potentials
travel entire length of axon
Action Potentials
sodium channels open, allowing positively
charged sodium ions to flow into cell; membrane potential
becomes more positive
Depolarization
potassium ion channels open; allows
positively charged potassium ions to flow out of cell; cell
becomes more negative, returning to resting membrane
potential
Repolarization
cell becomes more negative than its
normal resting membrane potential due to loss of potassium
ions (cations) plus loss of anions such as chloride
Hyperpolarization
period of time, after neuron has
generated an action potential, when neuron cannot be
stimulated to generate another action potential; can be
divided into two phases
Refractory period
when no additional
stimulus (no matter how strong) is able to produce an
additional action potential
Absolute refractory period
follows immediately
after absolute refractory period; only a strong
stimulus can produce an action potential
Relative refractory period
rate of propagation; influenced
by both axon diameter and presence or absence of
myelination; conduction speed determines how rapidly
signaling can occur within nervous system
Conduction speed
in myelinated axons where
insulating properties of myelin sheath increase
efficiency and speed of signal conduction; action
potentials only depolarize nodes of Ranvier and “jump
over” internodes
Saltatory conduction
in unmyelinated axons
where every section of axolemma from trigger zone to
axon terminal must propagate action potential; slows
conduction speed as each successive section of axon
must depolarize
Continuous conduction
certain cells of immune system
attack myelin sheaths within CNS; type of autoimmune
disorder (patient’s own immune system attacks part of
body)
Multiple sclerosis (MS)
result from progressive slowing of action
potential propagation; exact symptoms depend on region
of CNS affected; most exhibit changes in sensation (e.g.,
numbness), alterations in behavior and cognitive abilities,
and motor dysfunction, including paralysis
Symptoms
where a neuron meets its target cell
Synapse
neuron sending message from its
axon terminals
Presynaptic neuron
neuron receiving message from
presynaptic neuron at its cell body, axon, or dendrites
Postsynaptic neuron
transfer of chemical or
electrical signals between neurons at a synapse;
fundamental process for most functions of nervous
system
Synaptic transmission
either neuron can be pre or
postsynaptic depending on which direction current is flowing between
them
Transmission is bidirectional
time gap between arrival of action potential at axon terminal and effect on postsynaptic
membrane
Synaptic delay
toxin causes massive
release of neurotransmitter leading to repetitive stimulation of
postsynaptic neuron
Female black widow
most lethal of 40 species in United States; venom
prevents postsynaptic sodium channels from closing; membrane remains
polarized and continues to fire action potential
Bark scorpion
muscle hyperexcitability, sweating, nausea and
vomiting, and difficulty breathing
Common symptoms
depends on amount of venom received and
availability of medical care; severe cases usually require antivenin to block
effects of toxin
Treatment and prognosis
small molecule
neurotransmitter widely used by nervous system
Acetylcholine
bind to ACh; found in
neuromuscular junction, within brain and spinal cord and
within autonomic nervous system
Cholinergic synapses
class of five
neurotransmitters synthesized from amino acids; used
throughout CNS and PNS for many functions such as
regulation of homeostasis and cognition; first three form
catecholamine subgroup, all of which are made from
amino acid tyrosine; mostly excitatory
Biogenic amines
found mainly in ANS where it influences
heart rate, blood pressure, and digestion; in CNS it regulates
sleep/wake cycle, attention, and feeding behaviors
Norepinephrine (catecholamine, also known as
noradrenalin)
also used in ANS; has similar functions as norepinephrine;
more widely used as a hormone by endocrine system.
Epinephrine (catecholamine, also known as adrenalin
used extensively by CNS;
helps to coordinate movement; involved in emotion and
motivation
DOPAMINE
synthesized from amino acid tryptophan;
most serotonin-secreting neurons are found in brainstem;
axons project into multiple areas of brain; functions
include mood regulation, emotions, attention, feeding
behaviors, and daily rhythms
Serotonin`
synthesized from amino acid histidine;
involved in regulation of arousal and attention
Histamine
most important excitatory neurotransmitter
in CNS; binds to its ionotropic postsynaptic receptors
and opens channels that allow for flow of both sodium
and calcium ions; generate EPSPs in postsynaptic neuron
Glutamate
both major inhibitory
neurotransmitters; induce IPSPs on postsynaptic neurons
by opening chloride ion channels; hyperpolarize
axolemma
Glycine and GABA
group of neurotransmitters that have a
wide variety of functions within nervous system; must be
synthesized in cell body and transported to axon
Neuropeptides
released from type C sensory afferents that
carry information about pain and temperature; also released
by other neurons in brain, spinal cord, and gu
Substance P
make up a group of more than 20 neuropeptides
that include endorphins, enkephalins, and dynorphins,
all of which elicit pain relief and are nervous system
depressants
Opioids
neuropeptide involved in feeding
behaviors and may mediate hunger or feeling full
Neuropeptide Y
affect thought processes; generally
treated by modifying synaptic transmission to change how
neurons communicate with each other
Psychiatric disorders
study of drugs that affect higher
brain functions) targets either action potential generation
or some aspect of neurotransmitter physiology
Psychopharmacology
characterized by repetitive psychotic
episodes
Schizophrenia
marked by disturbances in mood; thought
to result from deficiency in synaptic transmission of serotonin,
norepinephrine, and/or dopamine
Depressive disorders
characterized by exaggerated and
inappropriate fear responses
Anxiety disorders
characterized by episodes of abnormal
elevated mood (mania) followed by depression
Bipolar disorders
groups of
interneurons within CNS
Neuronal pools
patterns of synaptic connection
between neural pools; two basic types of neural circuits
Neural circuits
begin with a single input neuron axon
that branches out to make contact with multiple
postsynaptic neurons that follow same pattern
Diverging circuits
basically opposite configuration of
diverging circuits; axon terminals from multiple input neurons
converge on onto a single postsynaptic neuron
Converging circuits
recurrent episodes of abnormal, disorganized electrical
activity in brain (seizures)
Epilepsy
