Chapter Eleven: Functional Organization of Nervous Tissue Flashcards
What are the five functions of the Nervous System?
- Maintaining Homeostasis
- Receiving Sensory Input
- Integrating Information
- Controlling Muscles and Glands
- Establishing and Maintaining
Name the Four things that compose the Nervous System:
- Brain
- Spinal Cord
- Nerves
- Sensory Receptors
The Central Nervous System is composed of what two things?
Brain and Spinal Cord
The Peripheral Nervous System is composed of what two things?
Sensory Receptors and Nerves
What is this?
- ending of neurons or separate, specialized cells
- detect temperature, pain, touch, pressure, light, sound, and odors
Sensory Receptors
What is this?
- a bundle of axons and their sheaths that connects CNS to sensory receptors, muscles, and glands
Nerve
What type of nerve?
- originate from the brain; 12 pairs
Cranial Nerves
What kind of nerve?
- originate from spinal cord; 31 pairs
Spinal nerves
What is this?
- Collection of neuron cell bodies outside CNS
Ganglion
What is this?
- extensive network of axons, and sometimes neuron cell bodies, located outside CNS
Plexus
What are the two divisions of the PNS?
Sensory and Motor
What division of the PNS?
- transmits action potentials from receptors to CNS
Sensory
What division of the PNS?
- transmits action potentials from CNS to effectors (muscles, glands)
Motor
The sensory division of the PNS is also known as…
afferent
The motor division of the PNS is also knows as the…
Efferent
What is this?
- from CNS to skeletal muscles
- voluntary
- cell body in CNS and axon extends muscle
- Single Neuron System
- Synapse
Somatic Nervous System
What is this?
- one neuron runs from CNS to effector
Single Neuron System
What is this?
- junction of a nerve cell with another cell. E.g., neuromuscular junction is a synapse between a neuron and skeletal muscle cell
Synapse
What is this?
- from CNS to smooth muscle, cardiac muscle, and certain glands
- subconscious or involuntary control
Autonomic Nervous System
What Nervous system is the Two neuron system a part of?
Autonomic Nervous System
What is this?
- first neuron from CNS to ganglion
- second neuron from ganglion to effector
Two Neuron System
What are the two divisions of the ANS?
Sympathetic and Parasympathetic
What division of ANS?
- prepares body for physical activity
Sympathetic
What division of ANS?
- regulates resting or vegetative functions such as digesting food or emptying of the urinary bladder
Parasympathetic
What is this?
- plexuses within the wall of the digestive tract
- can control the digestive tract independently of the CNS
- considered part of ANS because parasympathetic and sympathetic neurons contribute to the plexi
Enteric Nervous System
What type of cell?
- support and protect neurons
Glial Cells
What is this?
- also known as nerve cells
- receive stimuli and transmit action potentials
Neurons
What are the three parts of the neuron?
- Cell Body
- Dendrites
- Axons
What part of the neuron is responsible for input?
Dendrites
What part of a neuron is responsible for output?
Axons
What part of the Neuron Cell Body (Soma)?
- short, often highly branched
Dendrites
What part of the Neuron Cell Body?
- has rough E.R: primary site of protein synthesis
Nissl Substance
What part of the Neuron Cell Body?
- small protuberance where axons synapse with dendrite
Dendritic Spines
What are the five parts of the Axon?
- Trigger Zone
- Axoplasm
- Axolemma
- Presynaptic Terminals
- Synaptic Vesicles
What part of the axon?
- site where action potentials are generated
- axon hillock
- initial segment: beginning of axon
Trigger Zone
What part of the axon?
- cytoplasm
Axoplasm
What part of the axon?
- Plasma Membrane
Axolemma
What are the three types of neurons?
- Sensory
- Motor
- Interneurons
What type of neuron?
- action potentials toward CNS
Sensory or Afferent
What type of neuron?
- action potentials away from CNS
Motor or Efferent
What type of neuron?
- located within CNS and connect one neuron to another
Interneurons or Association Neurons
What are the three structural classifications of neurons?
- Multipolar
- Bipolar
- Pseudo-unipolar
What structural classification of neurons?
- most neurons in CNS; motor neurons
Multipolar
What structural classification of neurons?
- sensory neurons in retina of the eye and nose
Bipolar
What structural classification of neurons?
- sensory neuron of peripheral nervous system
Pseudo-unipolar
Glial Cells if the CNS: Astrocytes
- processes form _________ that cover the surfaces of neurons and blood vessels and the pia matter
feet
Glial Cells of the CNS: Astrocytes
- Regulate what substances reach the CNS from the…
blood
Glial Cells of the CNS: Astrocytes
- produce chemicals that promote __________ _______________ to form blood-brain barrier
tight junctions
Glial Cells of the CNS: Astrocytes
- regulate extracellular brain __________ composition
fluid
Glial cells of the CNS: Astrocytes
- integral in healing following damage and stores…
Glycogen
Glial Cells of the CNS: Ependymal Cells
- Lines brain ventricles and ___________ _________ central canal
spinal cord
Glial Cells of the CNS: Ependymal Cells
- specialized versions of ependymal form choroid….
plexuses
What part of Ependymal Cells secretes cerebrospinal fluid?
Choroid Plexus
Glial Cells of the CNS: Ependymal Cells
- ___________ help move fluid through the cavities of the brain
Cilia
Glial Cells of the CNS: Ependymal Cells
- Have long processes on basal surface that extend within the __________ tissue, may have astrocyte-like functions
brain
What type of Glial Cell of the CNS?
- specialized macrophages
- responds to inflammation, phagocytize necrotic tissue, microorganisms, and foreign substances that invade the CNS
Microglia
What type of Glial Cell of the CNS?
- have cytoplasmic extensions that surround axons
- form myelin sheaths if surrounding axon
- single (of these) can form myelin sheaths around portions of several axons
Oligodendrocytes
What type of Glial Cell of the PNS?
- wrap around portion of only one axon to form myelin sheath
- wrap around many times
- during developments, as cells grow around axon, cytoplasm is squeezed out and multiple layers of cell membrane wrap the axon
Schwann Cells
What type of Glial Cell of the PNS?
- surround neuron cell bodies in sensory and autonomic ganglia
- provide support and nutrients
- help control microenvironment
- protect neurons from heavy metals
Satellite Cells
What type of axon?
- myelin protects and insulates axons from one another, speeds transmission, functions in repair of axons
- not continuous - nodes of ranvier
- degeneration of myelin sheaths occur in multiple sclerosis and some cases of diabetes mellitus
Myelinated Axons
What type of axon?
- rest in invaginations of Schwann cells or oligodendrocyytes
- not wrapped around the axon
- gray matter
Unmyelinated Axon
What nervous system?
- capable of axon regeneration following injury
- Schwann cells secrete substances required for regeneration
PNS
What nervous system?
- axon regeneration is very limited
CNS
What type of matter?
- unmyelinated axons, cell bodies, dendrites, glia
- PNS
- Brain
- Spine
Gray Matter
What type of matter?
- myelinated axons
- CNS
- Brain
- Spine
White Matter
Gray matter, in the brain, is located in the…
outer cortex and inner nuclei
Gray matter in the spine is in the…
deeper portion
Gray matter in the PNS is in the….
ganglia
White matter, in the CNS, is located in….
nerve tracts that propagate action potentials from one area to another
White matter in the brain is located….
deeper
White matter in the spine is located more…
superficial
Cells produce electrical signals called….
Action Potentials
Electrical properties result from what two things?
- Ionic concentration differences across plasma membrane
- Permeability of membrane
Ion concentrations are a result of what two processes?
- Na+/K+ pump
- membrane permeability
High concentration of Na and Cl- ions __________ and high concentration of K+ and proteins on the inside
outside
Steep concentration gradient of Na+ and K+, but in ____________ directions
opposite
Proteins are synthesized ________ the cell
inside
Proteins are ____________ charged
negatively
Gated ion channels open and close because of some sort of ____________
stimulus
When gated ion channels open, they change the __________________ of the cell membrane
permeability
In Leaky Ion Channels, protein repels Cl-, they move…
out
In Leaky Ion Channels, the concentration of K+ is higher inside than out; move…
out
In Leaky Ion Channels, the concentration of Na+ is higher outside than in; move….
in
Leaky Ion channels:
always open and responsible for permeability when membrane is at….
rest
To establish resting membrane potential, the number of charged molecules ions inside and outside the cell need to be nearly…
equal
To establish resting membrane potential, the concentration of K+ needs to be higher _________ than __________ the cell and the opposite for Na+
inside
outside
What is this?
- unequal distribution of charge exists between the immediate inside and immediate outside of the plasma membrane: 70 to -90mV
Potential Difference
At equilibrium, there is very __________ movement of K+ or other ions across the plasma membrane
little
Establishing the Resting Potential:
K+ leaks out down…
concentration gradient
Establishing the Resting Potential:
K+ leaks in due to attraction to…
proteins
What three things do not have a great effect on resting potential since there are very few leakage channels for these ions?
- Na+
- Cl-
- Ca2+
Ion concentrations are maintained by what kind of pump?
Na/K
Establishing the Resting Potential:
For each ATP that is consumes, three ____ moved out, two ____ moved in
Na
K+
Establishing the Resting Potential:
Outside of the plasma membrane is slightly…
positive
Gated Ion channels open and close because of some sort of….
stimulus
Gated Ion Channels influence the _____________ of the cell membrane
permeability
What kind of gated ion channel?
- open or close in response to ligand such as ACh binding to receptor protein
- receptor proteins are usually glycoproteins. E.g., acetylcholine binds to acetylcholine receptor on a Na+ channel
- Channel opens, Na+ enters the cell
Ligand-gated
What kind of gated ion channel?
- open or close in response to small voltage changes across the cell membrane
- at rest, membrane is (-) on the inside compared to outside
- when cell is stimulated, that relative charge changes and these channels either open or close
- Types: Na+, K+, Ca2+
Voltage-gated
What kind of gated ion channel?
- respond to touch and other forms of mechanical stimulation of the skin
Mechanically-gated channels
What kind of gated ion channel?
- respond to temperature changes in the skin
Temperature-gated
What is this?
- potential difference becomes smaller or less polar
Depolarization
What is this?
- potential difference returns to normal
Repolarization
What is this?
- Potential difference becomes greater or more polar
Hyperpolarization
Changing the resting membrane potential: K+
- in resting membrane, K+ movement in and out through the leakage channels is…
equal
Changing the Resting Membrane Potential: K+
- If gated K+ channels open, more K+ diffuses out but this is opposed by the negative charge that starts to develop as the K+ diffuses out which causes…
Hyperpolarization
Changing the Resting Membrane Potential: Na+
- Change the concentration of Na+ inside or outside the cell -> little effect because few leak and gated channels remain…
closed
Changing the Resting Membrane Potential: Na+
- when gates open, Na+ diffuses in, ________________ the membrane
depolarizing
Changing the Resting Membrane Potential: Ca2+
- If extracellular Ca2+ concentration decreases -> Na+ gates open ->….
depolarization
Changing the Resting Membrane Potential: Ca2+
- If extracellular concentration of Ca2+ increases -> Na+ gates close -> ______________ or __________________
repolarization
hyperpolarization
Changing the Resting Membrane Potential: Ca2+
- If gated Ca2+ channels open, Ca2+ diffuses into the cell, causing…
depolarization
What five things do graded (local) potentials result from?
- Ligands binding to receptors
- Changes in charge across membrane
- Mechanical Stimulation
- Temperature Changes
- Spontaneous change in permeability
Graded potentials:
- magnitude varies from small to large can depend on one of these three things…
- Stimulus
- Strength
- Frequency
Graded (local) potentials can ________ or add onto each other
summate
Graded (local) potentials can cause…
action potentials
Depolarization phase is followed by the….
repolarization phase
Depolarization, in terms of action potentials, is more…
positive
Repolarization, in terms of action potentials, is more…
negative
Afterpotential, in terms of action potentials, has slight…
hyperpolarization
A large enough graded potential may cause the membrane to reach…
Threshold
What is this?
- no matter how strong the stimulus, as long as it is greater than threshold, then an action potential will occur
All-or-none principle
Depolarization Phase:
What kind of Voltage gated channels open rapidly as the threshold is reached?
Na+
Depolarization Phase: Voltage-gated Na+ channels
- activation gate: allows Na+ to diffuse in; opens at…
threshold
Depolarization Phase: Voltage-gated Na+ channels
- inactivation gate: open during rest and depolarization; closed during _______________ to prevent passage of Na+
repolarization
Depolarization Phase:
What is this?
- Na+ diffuses into cell, causing depolarization
- Depolarization causes more voltage-gated Na+ channels to open -> more Na+ diffuses into the cell
Positive Feedback
Voltage-gated K+ channels open at threshold and open at the same time as Na+ but more ____________. More Na+ diffuses into the cell than K+ diffuses out
slowly
Repolarization phase:
Inactivation gates of voltage-gated Na+ channels close -> decreased Na+ into cell ->…
repolarization
Repolarization Phase:
- Voltage-gated K+ channels continue to open > increased K+ out of the cell —>…
Repolarization
Repolarization Phase:
Return of resting membrane potential causes activation gates in voltage-gated Na+ channels to __________ and inactivation gated to __________
close
open
What is this?
- sensitivity of area to further stimulation decreases for a time
Refractory Period
What are the two types of Refractory Periods?
Absolute and Relative
What type of Refractory Period?
- complete insensitivity exists to another stimulus
from beginning of action potential until near end of repolarization
- no matter how strong the stimulus, a send action potential cannot be produced
Absolute
What type of Refractory Period?
- period of hyperpolarization
- voltage-gated K+ channels still open
- A stronger-than-threshold stimulus can initiate another action potential
Relative
Action Potential Frequency:
Threshold stimulus generates a…
single action potential
Action Potential Frequency:
Strength of stimulus is measured by ____________ and ______________ of action potentials
frequency and duration
Action Potential Frequency:
Stronger stimulus -> increased…
action potential frequency
Graded potentials at trigger zone cause action potential if they reach…
threshold
Action potential in one site causes action potential at the next location. It cannot go backwards because initial action potential site is in a _____________ period which ensures one-way conduction of impulse
Refractory Period
Saltatory Conduction occurs in myelinated…
axons
Saltatory Conduction:
Action potentials form at one node of…
Ranvier
Saltatory Conduction
Current travels through _______________ region
myelinated
Saltatory Conduction
Action potentials form at each successive node of…
Ranvier
The speed of conduction is faster in ____________ than in non-myelinated
myelinated
In myelinated axons, _________ act as insulation forcing ionic currents to jump from node to node
lipids
In myelinated axons, speed is affected by thickness of the…
myelin sheath
The diameter of axons is large and conducts ____________ than small-diameter
faster