Chapter 9 Flash cards
What does the central nervous system consist of?
the brain and spinal cord.
what does the peripheral nervous system consist of?
all nervous tissue outside the CNS.
Components include nerve and sensory receptors.
what is a nerve?
is a bundle of hundreds to thousands of axon plus associated connective tissue and blood vessels that lies outside the brain and spinal cord.
how many pairs of cranial nerves emerge from the brain?
12
how many nerves emerge from the spine
31
what is a structure of the nervous system that monitors changes in external or internal environment?
a sensory receptor
this division of the PNS, AKA the afferent division of the PNS conveys input into the CNS from the body.
the sensory division.
The afferent division/sensory division of the PNS provides the CNS with what?
sensory information about the somatic senses and special senses.
what is a somatic sense?
tactile, thermal, pain, and proprioceptive sensations.
what are the special senses?
smell, taste, vision, hearing, and equilibrium
Which division of the PNS conveys output from the CNS to effectors?
motor/efferent division
the motor or efferent division is subdivided into what two systems?
somatic nervous system and an autonomic nervous system
the somatic nervous system conveys output from the CNS to where?
skeletal muscles only.
where does the autonomic nervous system convey output from and to?
CNS to smooth muscle, cardiac muscle, and glands.
what are the two branches of the autonomic nervous system (ANS)?
sympathetic ad parasympathetic nervous system
what is the third branch of the ANS?
enteric nervous system (ENS) (enteron = intenstines).
an extensive network of 100 million neurons confined to the GI tract.
What are the three basic functions of the nervous system?
Sensory function
integrative function
Motor function
What are the three parts of a neuron?
cell body
dendrites
axon
whats another name for cell body
soma
what is a collection of neuron cell bodies outside the CNS called?
ganglion (GANGLION= KNOT)
What makes up the cell body?
nucleus, cytoplasm with typical organelles.
what is a highly branched structure that carries impulses to the cell body?
dendrites
what conducts away from the cell body toward another neuron, muscle or gland?
axon
what is the cone shaped elevation where the axon joins the cell body?
axon hillock (hillock = small hill)
what is the site called where two neurons or a neuron and an effector cell can communicate?
a synapse
what are the tiny sacs that store chemicals called neurotransmitters and are released?
synaptic vesicles
this structural classification of neuron usually have several dendrites and one axon. most neurons in the brain and spinal cord are of this type
multipolar neurons
this structural classification of neurons have one main dendrite and one axon. they are usually found in the retina of the eye, in the inner ear, and in the olfactory area of the brain.
bipolar neurons
this structural classification of neurons have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body?
unipolar neurons
the dendrites of most unipolar neurons function as what?
sensory receptors.
where are the cell bodies of most unipolar neurons located?
the ganglia of spinal and cranial nerves.
what are the three functional classifications of neurons
sensory
motor
interneurons
where is the action potential of sensory neurons conveyed into?
the CNS. Most sensory neurons are unipolar.
these mostly multipolar in structure neurons convey action potential AWAY from the CNS to effectors:
Motor neurons
Most of these neurons are multipolar in structure, integrate incoming sensory information from sensory neurons and then elicit a motor response.
interneurons
What makes up half the volume of the CNS, smaller and more numerous than neurons, and support, nourish, and protect neurons
neuroglia
What are the function of neuroglia?
support, nourish, and protect neurons. multiply to fill in the space formerly occupied by neurons.
these four neuroglia are found in the CNS
astrocytes, oligodendrocytes, microglial cells, and ependymal cells
what two neuroglia are found in the PNS?
schwann and satellite cells
what is the many layered covering composed of lipid and protein around an axon?
myelin sheath
how are myelin sheaths formed?
schwann cells in the PNS and oligodendrocytes in the CNS produce myelin sheaths by wrapping themselves around and around axons.
what is the gap in the myelin along the axon?
Nodes of Ranvier
two diseases that destroy myelin sheaths?
multiple sclerosis and tay sachs
Cluster of cell bodies in the PNS
ganglion
cluster of cell bodies in the CNS
nucleus
what is a bundle of axons that is located in the PNS
Nerve
a bundle of axons that is located in the CNS
a tract
this type of matter is composed primarily of myelinated axons:
white matter
this matter of the nervous system contains cell bodies, unmyelinated axons, terminals, and neuroglia.
gray matter
how is there regeneration of PNS neurons?
axons and dendrites in the PNS can be repaired if cell body is intact and Schwann cells functional, they can form a regeneration tube as long as scar tissue does not fill the tube,
regeneration of CNS neurons
very limited. inhibited by neuroglia and lack of fetal growth stimulator cues.
nerve impulses that allow for communication between neurons
action potential
what is a membrane potential
the difference in the amount of electrical chage on the inside of the plasma membrane as compared with the outside.
What is a cell that has membrane potential said to be be?
polarized.
what is the term for the voltage across the plasma membrane?
resting membrane potential
what are the channels that allow ions to move by diffusion from high to low concentration
ion channels
two types of ion channels
leakage channels- allow ions to leak through
voltage gated channels- open in response to a change in membrane potential (voltage)
What is the “threshold” when an action potential arises?
typically, about -55 mV
what are the two main phases of an action potential?
depolarizing phase
repolarizing phase
What is the phase where voltage gated Na+ channels open ~ as more Na+ enters cell, membrane potential rises and becomes positive? (-70 ~ 0 ~ +30 mv)
depolarizing phase
what is the phase where voltage gated K+ channels open, ~ as more K+ leaves cell, membrane potential is returned to the resting valuse. (+30 ~ 0 ~ -70 mv)
repolarizing phase
what is the term for when nerve impulses travel from where they arise (axon hillock) along the axon to the axon terminal?
propagation
what is the type of potential conduction that occurs in unmyelinated axons (and in muscle fibers) called?
continuous conduction
when current flows from one membrane only at the nodes, the impulses appear to leap from node to node. This type of impulse conduction is called what?
saltatory conduction
what are the two most important factors that determine the speed of nerve impulse conduction?
the diameter of the axon and and the presence or absence of a myelin sheath.
what is the neuron called sending the signal?
presynaptic neuron
what is the neuron receiving the message called?
postsynaptic neuron
what separates the presynaptic and postsynaptic neurons?
synaptic cleft, a tiny space filled with interstitial fluid.
what are the two types of synapses
electrical and chemical
what type of synapse do nerve impulses conduct directly between the plasma membrane of adjacent neurons through gap junctions?
electrical synapse
this type of synapse, the most common, nerve impulses in a presynaptic cause the release of neurotransmitter molecules into the synaptic cleft.
chemical synapse
three types of ways neurotransmitters are removed:
1) some diffuse away from the synaptic cleft
2) destroyed by enzymes
3) reuptaked back into the neuron that released them. some are transported into neighboring neuroglia (uptake)
Types of neurotransmitters
acetylcholine (ACh)- common in PNS
a) stimulatory on skeletal muscles
b) inhibitory (on cardiac muscle)
amino acids
a) glutamate, aspartate, GABA
Modified amino acids
a) norepinephrine, dopamine, serotonin
Neuropeptides such as endorphins
nitric oxide
