Chapter 11 Biology Exam
Define continuous propagation and saltatory propagation
Continuous- propagation of an action potential alone an unmyelinated axon. Saltatory- the relatively rapid propagation of an action potential between successive nodes of a myelinated axon.
Describe depolarization, repolarization, and hyerpolarization
De- a shift form resting membrane potential toward positive value. Re- return of depolarized membrane potential Hyper- a shift from the resting membrane potential toward negative value.
What effect would decreasing the concentration of extracellular potassium ions have on the resting membrane potential of a neuron?
Decreasing the concentration of extracellular potassium ions would cause more potassium ions to leave the cell through potassium leak channels
Describe the all or none principle
Refers to the fact that all stimuli that bring the membrane to threshhold generate identical action potentials.
Compare the absolute refractory period with the relative refractory period
Refractory- The time between the initiation of an action potential and the restoration of the normal resting membrane potential
Compare presynaptic and postsynaptic cells.
Presynaptic- usually a neuron Postsynaptic- can be a neuron or other type of cell such as a skeletal muscle fiber or gland cell.
Define graded potential
A change in the membrane potential that cannot spread far from the site of stimulation.
Define gated ion channels
Active channels in the plasma membrane that open or close in response to specific stimuli
Classify neurons based on their function
As sensory neurons, interneurons, or motor neurons
Which glial cell protects the CNS from chemicals and hormones circulating in the blood?
Astrocytes protect the CNS
Identify the three types of gated ion channels, and state the conditions under which each operates
Chemically gated ions operate when they bind specific chemicals such as ACh. Voltage gated ion channels operate in response to change in the membrane potential. Mechanically gated ions operate in response to physical distortion of the membrane surface.
List the events involved in the generation of an action potential
Depolarization, inactivation of voltage gated potassium ion channels, and closing of voltage gated potassium ion channels
Define excitatory postsynaptic potential(EPSP) and inhibitory postsynaptic potential (IPSP)
EPSP- a graded depolarization of a postsynaptic membrane by a neurotransmitter released by a presynaptic cell IPSP-a graded hyperpolarization of a postsynaptic membrane after the arrival of a neurotransmitter
Name the neuroglia of the CNS
Epydymal cells, microglia, astrocytes, and oligodendrocytes
Describe the role of regulatory neurons
Facilitate or inhibit the activities of presynaptic neurons by affecting the plasma membrane of the cell body.
Compare a graded potential with an action potential
Graded- temporary, localized changes Action- generated and begin in one location
Which neuroglia appear in increased numbers in a person with a brain infection?
In a person with brain infection
In which part of a neuron does Walerian degeneration occur?
In axons of the PNS neurons
What happens at the sodium-potassium exchange pump?
Maintains the cells resting membrane potential by ejecting 3 sodium ions from the cell for every 2 potassium ions it recovers from extracellular fluid
Are unipolar neurons in a tissue sample of the PNS more likely to have a sensory or a motor function?
More likely to have a sensory function.
Why is a CNS neuron not usually replaced after its injured?
Most CNS neurons lack centrioles which organize the microtubules of the spindle apparatus during mitosis, so these cels cannot divide and replace themselves
What factors account for the local currents associated with graded potentials?
Movement of sodium ions parallel to the inner and outer surfaces of the plasma membrane accounts for the local currents.
What event must occur in the postsynaptic cell before it generates an action potential?
Must reach threshold to generate an action potential
Classify neurons based on their structure
Neurons are structurally classified as anaxonic, bipolar, unipolar, or multipolar
Identify the neuroglia of the PNS
Satellite cells and Schwann cells
Name the effectors of the ANS
Smooth muscle, cardiac muscle, glands, and adipose tissue
What effect would a chemical that blocks voltage-gated sodium ion channels in a neurons plasma membrane have on its membrane potential?
Sodium ions could not rush into the ell and its membrane potential will not change.
Compare temporal summation with spatial summation
Temporal- addition of a rapid succession of stimuli occuring at a single synapse. Spatial- the addition of stimultaneous stimuli applied at different locations
Compare the central and peripheral nervous system
The CNS consists of the brain and spinal cord. It integrates, processes, and coordinates sensory data and motor commands. The PNSincludes all nervous tissue outside the CNS.
What determines the frequency of action potential generation?
The degree of sustained depolarization at the axon hillock determines the frequency of action potential generation
The greater degree of sustained depolarization at the axon hillock, the ___ (higher or lower) the frequency of action potentials generated
The greater the degree of sustained depolarization at the axon hillock, the higher the frequency of generation of action potentials.
Define information processing
The integration of stimuli by an individual cell
Define resting potential
The membrane potential of an undisturbed cell
Describe the neurilemma of a myelinating and nonmyelinating Schwann cell
The outer surface of the myelin sheath covering an internode of one axon.
What is the relationship between myelin and the propagation speed of action potential?
The presence of myeline greatly increases the propagation speed of action potentials
Define action potential
The propagated changes the membrane potential of excitable cells
Which division of the PNS brings info to the CNS?
The sensory division of the PNS
Describe a synapse
The site where a neuron communicates with another cell. It involves a presynaptic cell and a postsynaptic cell.
Define membrane potential
The unequal charge distribution between the inner and outer surfaces of the plasma membrane.
Contrast the white matter and gray matter in the CNS
White matter of the CNS is dominated by myelinated axons. The gray matter includes areas containing neuron cell bodies, dendrites, and unmyelinated axons
Name the structural components of a typical neuron
cell body, axon, and dendrites
Contrast an electrical synapse with a chemical synapse
in chemical synapses a neurotransmitter crosses a narrow synaptic cleft
Describe synaptic fatigue
occurs in an axon terminal when neurotransmitters are released into the synaptic cleft at a faster rate than they can be reabsorbed or recycled
Describe the components of a chemical synapse
the site where a neuron communicates with another neuron or with a cell of a different type- are a presynaptic cell and a postsynatic cell whose plasma membranes are seperated by a narrow gap called the synaptic cleft.
