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Anatomy & Physiology: Part 1
w/Janet Kluftinger
100
Biology
Undergraduate 1
01/09/2008

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Cards

Term
5 Functions of the Nervous System
Definition
  1. Sensory input
  2. Integration
  3. Homeostasis
  4. Mental activity
  5. Control of muscles and glands
Term
Central Nervous System (CNS)
Definition
Spinal cord and brain
Term
Peripheral Nervous Sytem (PNS)
Definition
All neural tissue outside CNS
Term
Where does the spinal cord connect to the brain?
Definition
Through the foramen magnum of the skull.
Term
What two regions of nerves make up the PNS?
Definition
Spinal nerves and cranial nerves.
Term
Afferent Division of PNS
Definition
Brings sensory information to CNS from receptors in peripheral tissues and organs
Term
Efferent Division of PNS
Definition
Carries motor commands from CNS to muscles and glands (aka effectors) via motor neurons (aka effector neurons)
Term
Neuron
Definition
Nerve cell, consisting of a cell body, dendrites, and an axon
Term
Sensory receptors
Definition
Ending of neurons or separate, specialized cells that detect such things as temperature, pain, touch, pressure, light, sound, odors
Term
Nerve
Definition
A bundle of axons plus associated connective tissue and blood vessels that connects CNS to sensory receptors, muscles, and glands
Term
How many pairs of brain-originating cranial nerves are there?
Definition
12 pairs
Term
How many pairs of spinal-cord-originating spinal nerves are there?
Definition
31 pairs
Term
Ganglion
Definition
Collection of neuron cell bodies outside CNS
Term
Plexus
Definition
Extensive network of axons, and sometimes neuron cell bodies, located outside CNS
Term
Synapse
Definition
Functional junction between two neurons or between a neuron and an effector, such as a muscle or gland; may be electrical or chemical
Term
Action Potential
Definition
An electrical signal that propagates along the membrane of a neuron or muscle fiber (cell)
Term
Myelin Sheath
Definition
Multilayered lipid & protein covering around some axons that insulates them & increases the speed of nerve impulse (action potential) conduction
Term
What does the Somatic Nervous System voluntarily control?
Definition
Skeletal muscle contractions.
Term
What does the Autonomic nervous system subconsciously control?
Definition
Regulation of smooth muscle, cardiac muscle, and glandular secretions.
Term
What system is a single neuron system that conducts impulses from the CNS?
Definition
Somatic
Term
What system is a two neuron system that conducts impulses from the CNS? What makes it two neurons?
Definition
Autonomic; first from CNS to ganglion; second from ganglion to effector
Term
Which division of the Autonomic Nervous System is responsible for elevation of metabolic rate and increased alertness (“flight, fright, or fight” reactions)?
Definition
Sympathetic
Term
Which division of the Autonomic Nervous System is responsible for activities that conserve energy and lower metabolic rate (“rest and digest” activities)
Definition
Parasympathetic
Term
What do the sensory neurons of the enteric division plexuses monitor?
Definition
Chemical changes within GI tract as well as stretching of its walls.
Term
Why would the Enteric division be considered separate from the PNS?
Definition
It can control the digestive tract (control contraction of GI tract smooth muscle; secretions of GI tract) independently of the CNS
Term
Neurons
Definition
Nerve cells receive stimuli and transmit action potentials
Term
What does the Cell Body contain?
Definition
Nucleus and Nissl bodies, which is rough endoplasmic reticulum
Term
What is the input-recieving portion of the neuron?
Definition
Short, often highly branched dendrites
Term
Dendritic Spines
Definition
Little bulge where axons synapse with dendrite
Term
What are axons responsible for?
Definition
The neuron output by transmission of impulses toward another neuron, muscle fiber, or gland cell
Term
Axon hillock
Definition
Cone-shaped area of cell body where axon arises from
Term
What part of the axon is closest to axon hillock?
Definition
Initial segment
Term
Trigger zone
Definition
Site where action potentials are generated; junction of axon hillock and initial segment
Term
Axoplasm
Definition
The cytoplasm of axon
Term
What is the plasma membrane of axon called?
Definition
Axolemma
Term
What are presynaptic terminals are also known as? What are they?
Definition
Terminal boutons; where axons terminate in small extensions with enlarged ends
Term
In the presynaptic terminals, what is the neurotransmitter contained in?
Definition
Synaptic vesicles
Term
Name two viruses that can infect the nervous system because of the transportation of material, taken in by endocytosis, up the axon to the cell body.
Definition
Rabies and herpes
Term
What are interneurons also known as? What is their function?
Definition
Associated neurons; they conduct action potentials from one neuron to another within the CNS
Term

What type of neuron is this? Where is it primarily found?

[image]

Definition
Multipolar; most neurons of CNS
Term

What type of neuron is this? Where is it primarily found?

[image]

Definition
Bipolar; special sense organs (in retina, inner ear, olfactory area of brain)
Term

What type of neuron is this? Where is it primarily found?

[image]

Definition
Unipolar; most sensory neurons of the PNS (touch, stretch)
Term
What are the four functions of neuroglia, the major support cells in the CNS?
Definition
  1. Form permeability barrier between blood and neurons
  2. Phagocytose foreign substances
  3. Produce cerebrospinal fluid
  4. Form myelin sheaths around axon
Term

What type of neuroglial cell is this? What is it's main function?

[image]

Definition
Astrocytes; form permeability barrier between blood and neurons
Term

What type of neuroglial cell is this? What is it's main function?

[image]
Definition
Ependymal; produce cerebrospinal fluid
Term

What type of neuroglial cell is this? What is it's main function?

[image]
Definition
Microglia; phagocytose foreign substances
Term

What type of neuroglial cell is this? What is it's main function?

[image]
Definition
Oligodendrocytes; form myelin sheaths around axon
Term
Pia mater
Definition
The membrane covering the outside of brain and spinal cord, which Astrocyte process feet cover the surface of.
Term
How do Astrocytes provide structural support and promote the blood-brain barrier?
Definition
They have lots of microfilaments to provide support; they produce chemicals which promote the formation of tight junctions between epithelial cells of capillaries
Term
What does the blood-brain barrier regulate in brain and blood fluid composition?
Definition
Protects neurons from toxic substances, allows exchange of nutrients and waste products between neurons and blood, prevents fluctuations in composition of blood from affecting functions of the brain
Term
Where are ependymal cells located?
Definition
Line brain ventricles and spinal cord central canal
Term
What is the function of choroid plexuses, which are specialized ependymal cells?
Definition
Secrete cerebrospinal fluid that circulates through ventricles of brain; have cilia which help move fluid thru cavities of the brain
Term
What do microglia respond to? phagocytose?
Definition
Inflammation; necrotic tissue, microorganisms, and foreign substances that invade the CNS
Term
Oligodendrocytes may form myelin sheath around several axons, name the cells that form sheaths around only one.
Definition
Schwann cells or neurolemmocytes
Term
How is the myelin sheath formed?
Definition
During development, as cells grow around axon, cytoplasm is squeezed out and multiple layers of cell membrane, which is primarily fatty phospholipid, wrap around the axon.
Term
Satellite cells
Definition
Surround neuron cell bodies in ganglia, provide support and nutrients
Term
Functions of myelin:
Definition
Protects and insulates axons from one another, speeds transmission, functions in repair of axons
Term
What interrupts the myelin-covered areas of the axon? What are these ares called?
Definition
Nodes of Ranvier; Internodes
Term
Unmyelinated axons
Definition

These rest in invaginations of Schwann cells or oligodendrocytes, so they're not fully sheathed by myelin

[image]

Term
White matter
Definition
Bundles of parallel axons with associated myelin sheaths
Term
Gray matter
Definition
Collections of neuron cell bodies, dendrites, and unmyelinated axons
Term
What do axons that make up white matter of CNS form to propagate action potentials from one area in the CNS to another?
Definition
Nerve tracts
Term
What do all living cells have across their plasma membrane?
Definition
An electral charge difference or voltage gradient.
Term
What is the purpose of selective ion channels?
Definition
Ions are charged and cannot diffuse through the plasma membrane on their own.
Term
Are cells more permeable to potassium or sodium?
Definition
There are more potassium channels than sodium, so potassium.
Term
Besides ion channels what else contributes to the ion chemical gradient?
Definition
The Sodium/Potassium exchange pump.
Term
Where is Cloride found and why?
Definition
Cl- ions are found in the extracellular fluid because they repel from the negatively charged proteins inside the cell and are able to move outside via non-gated channels.
Term
Which ions are moving when the cell is at rest?
Definition
Cl- moves out of the cell and K+ tends to move out as well. Na+ channels are closed so it stays outside the cell.
Term
What is the process of the Sodium/Potassium exchange pump?
Definition

Three intracellular Na+ and one ATP bind on inside of carrier molecule. Phosphorylation changes the shape of the carrier molecule, transporting Na+ outside the cell. Now two extracellular K+ bind to the carrier molecule, which gets dephosphorylated, resumes its orginal shape, and transports K+ inside the cell.

[image]

Term
Potential difference
Definition
Tthe unequal distribution of charge that exists between the immediate inside and immediate outside of the plasma membrane
Term
What is a cell that has this potential difference across its plasma membrane said to be?
Definition
Polarized
Term
What is the range of Resting Membrane Potential(mV) in neurons?
Definition
-40 to -90
Term
Characteristics Responsible for the Resting Membrane Potential
Definition
  1. The number of charged molecules and ions inside and outside the cell is nearly equal

  2. The concentration of K+ is higher inside than outside the cell, and the concentration of Na+ is higher outside than inside the cell.

  3. The plasma membrane is 50-100 times more permeable to K+ than to other positively charge ions such as Na+.

  4. The plasma membrane is impermeable to large intracellular negatively charged molecules such as proteins.

  5. K+ tend to diffuse across the plasma membrane from the inside to the outside of the cell.

  6. Because negatively charged molecules cannot follow the postively charged K+, a small negative charge develops just inside the plasma membrane.

  7. The negative charge inside the cell attracts positively charged K+. When the negative charge inside the cell through the plasma membrane, an equilibrium is established.

  8. The charge difference accross the plasma membrane at equilibrium is reflected as a difference in potential, which is measured in millivolts (MV).

  9. The resting membrane potential is proportional to the potential for K+ to diffuse out of the cell but not to the actual rate of flow for K+

  10. At equilibrium there is very little net movement of K+ or other ions across the plasma membrane.

Term
At resting potential most gated channels are ________, so that when they are ________ they change the permeability of the cell membrane.
Definition
closed; open
Term
What are the three types of gated ion channels and what do they respond to?
Definition
  1. Ligand-gated channels respond when a specific ligand binds to them
  2. Voltage-gated channels respond to small voltage changes across the cell membrane
  3. Mechanically-gated channels can respond to vibration, touch, temperature, or stretch
Term
How do alterations in [K+] change the membrane potential?
Definition

If extracellular [K+] increases, there is less of a gradient resulting in depolarization.

 If extracellular [K+] decreases, there is more of a gradient resulting in hyperpolarization.

Term
How do changes in K+ membrane permeability affect the membrane potential?
Definition
If gated K+ channels open, more K+ diffuses out resulting in hyperpolarization of charge.
Term
How do changes in Na+ membrane permeability affect the membrane potential?
Definition
If gated Na+ channels open, Na+ diffuses in resulting in depolarization.
Term
How do alterations in [Ca2+] change the membrane potential?
Definition

Voltage-gated Na+ channels are sensitive to [Ca2+] changes.

If extracellular [Ca2+] increases, Na+ gates close resulting in hyperpolarization.

If extracellular [Ca2+] decreases, Na+ gates open resulting in depolarization.

Term
What stimuli cause local potentials?
Definition
  • Ligands binding to their receptors
  • Changes in charge across plasma membrane
  • Mechanical stimulation
  • Temperature changes
  • Spontaneous changes in membrane permeability
Term
What does it mean for local potentials to be "graded"?
Definition

Their magnitude varies from small to large depending on stimulus strength or frequency.

[image]

Term
Local potentials rapidly decrease in magnitude as they spread over the surface of the plasma membrane but because they can summate or add onto each other a sufficiently large depolarizing local potential can ...
Definition

... cause the generation of an action potential.

[image]

Term
When local potential causes depolarization of plasma membrane to a level called the ________, a series of permeability changes occur that result in an ________.
Definition
Threshold; action potential
Term
Action Potential
Definition
A large change in membrane potential that propagates, without changing its magnitude, over long distances along the plasma membrane.
Term
List and describe the three phases of an action potential.
Definition
[image]
  1. Depolarization phase: membrane potential moves away from resting membrane potential and becomes less polar
  2. Repolarization phase: membrane potential returns toward the resting membrane state, becoming polarized again
  3. May get afterpotential: slight transient hyperpolarization, overshot of repolarization
Term
Explain in term of voltage-gated channels what goes on in the resting membrane potential.
Definition

[image]

Na+ activation gates are closed, but inactivation gates are open.

K+ channels are closed.

Term
Explain in term of voltage-gated channels what goes on in depolarization.[image][image]
Definition

[image]

Na+ channels open because activation gates open , Na+ diffuses in and the resulting voltage change causes further Na+ channels to open.

K+ channels start to open.

Term
Explain in term of voltage-gated channels what goes on in repolarization.
Definition

[image]

Na+ channels close because inactivation gates close, so diffusion of Na+ in stops.

K+ channels are now open and K+ diffuses out.

Term
Explain in term of voltage-gated channels what goes on in the end of repolarization and afterpotential.
Definition

[image]

Na+ channels are now in resting condition.

The continued diffusion of K+ produces the afterpotential.

The resting membrane potential is reestablished after the K+ channels close.

Term
Why can't another action potential be generated during  the absolute refractory period – no matter how strong the stimulus?
Definition
Because all voltage-regulated sodium channels either are already open or are inactivated.
Term
Why can only very strong stimuli initiate another action potential during the relative refractory period?
Definition
Many K+ channels are still open so the membrane is hyperpolarized and it will take a stronger signal to reach the threshold.
Term
How can you determine the difference in intensity between stimuli?
Definition
Number of sensory neurons activated by the stimulus and the frequency of impulses.
Term
What are the five classifications of stimulus strength?
Definition
  1. subthreshold
  2. threshold
  3. submaximal
  4. maximal
  5. supramaximal
Term
What determines the maximum frequency of action potentials?
Definition
The duration of the absolute refractory period.
Term
What are some methods of local anesthetics?
Definition
By blocking the opening of voltage-gated Na+ channels so impulses are stopped from reaching the CNS; by localized cooling so impulses propogate at lower speeds.
Term
How does positive feedback propagate an action potential?
Definition
When Na+ ions flow in, they cause voltage-gated Na+ channels in adjacent segments of membrane to open.
Term
Why can't an action potential normally go backwards?
Definition
Because the absolute refractory period of a previous action potential site prevents generation of action potential in reverse direction.
Term
Saltatory Conduction
Definition
The action potential is conducted from one node of Ranvier to another by generating local currents that flow through the extracellular fluid surrounding the myelin sheath and through the cytosol toward the next node of Ranvier.
Term
Internode
Definition
Where the myelin sheath covers the axolemma.
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