Exam 1- Chapter 7 Flashcards
What is the nervous system divided into?
- CNS
2. PNS
What is within the CNS?
Brain and Spinal cord
What is within the PNS?
Cranial and Spinal nerves
What are the two types of cells found within the nervous system?
- Neurons
2. Glial/Supporting Cells
What are the functional units of the nervous system?
Neurons
What cells in the nervous system maintain homeostasis?
Glial Cells
How much more abundant are glial cells vs. neurons?
5X more abundant
How do neurons transmit information?
- Responding to stimuli
- Producing and sending electrochemical impulses
- Releasing chemical messages
What are the main parts of a neuron?
- Cell Body
- Dendrites
- Axons
What does the cell body of a neuron contain?
Nucleus
The cell body is the ____ center and makes _____.
- Nutritional Center
2. Macromolecules
What are groups of cell bodies in the CNS called?
Nuclei
What are groups of cell bodies in the PNS called?
Ganglia
What is the function of the dendrites?
Receive information and convey it to the cell body
What is the function of the axons?
Conduct impulses away from the cell body
What is a bundle of axons in the CNS called?
Tracts
What is a bundle of axons in the PNS called?
Nerves
What are the 2 types of transport system axons utilize?
- Axoplasmic Flow
2. Axonal Transport
Which is faster, axoplasmic flow or axonal transport?
Axonal Transport
Axoplasmic flow moves ___ compounds toward ____.
- Soluble compounds
2. Nerve endings
How does axoplasmic flow move soluble compounds?
Via rhythmic contractions
Axonal transport moves ____ and _____ compounds ______ along _______.
- Large
- Insoluble
- Bidirectionally
- Microtubules
Which is energy dependent, axoplasmic flow or axonal transport?
Axonal Transport
What are the two types of axonal transport?
- Anterograde Transport
2. Retrograde Transport
Where does anterograde transport move materials?
Away from cell body
What molecular motor does anterograde transport utilize?
Kinesin
Where does retrograde transport move materials?
Toward cell body
What molecular motor does retrograde transport utilize?
Dynein
How can viruses and toxins enter the CNS?
Via retrograde axonal transport
Sensory/Afferent neurons conduct impulses _____ the CNS
Into
Motor/Efferent neurons conduct impulses _____ the CNS
Out
Where are association/interneurons located?
Entirely inside the CNS
What is the function of association/interneurons?
Integrate nervous system activity
Somatic motor nerves are responsible for what?
- Reflexes
2. Voluntary control of skeletal muscle
Autonomic motor nerves are responsible for what?
Involuntary effectors:
- Smooth muscle
- Cardiac muscle
- Glands
In a pseudounipolar neuron, the cell body sits along side of a _____ _____.
Single Process
What is an example of a pseudounipolar neuron?
Sensory Neurons
In a bipolar neuron dendrites and axons arise form ______ ends of the cells body.
Opposite
What is an example of a bipolar neuron?
Retinal Neurons
Multipolar neurons have ____ dendrites and ____ axon.
- Many
2. Axon
What is an example of multipolar neuron?
Motor neurons
What are the supporting/glial cells of the PNS?
- Schwann Cells
2. Satellite Cells
What are the supporting/glial cells of the CNS?
- Oligodendrocytes
- Astrocytes
- Microglia
- Ependymal Cells
What myelinates PNS axons?
Schwann Cells
What myelinates CNS axons?
Oligodendrocytes
What is different about myelination of axons in the PNS vs. CNS?
Oligodendrocytes myelinate several CNS axons at once while Schwann cells only do one at a time in the PNS
What do ependymal cells appear to be?
Neural stem cells
What are other glial cells involved in?
Nervous system maintenance
Describe specifically how Schwann cells myelinate axons in the PNS.
In PNS each Schwann cell myelinates 1mm of 1 axon by wrapping round and round axon
Schwann cells _____ ____ the axon.
Electrically Insulate
What is the uninsulated gap between adjacent Schwann cells called?
Nodes of Ranvier
Does axon regeneration occur much more readily in the CNS or PNS?
PNS
Why does axon regeneration occur more readily in the PNS?
Oligodendrocytes in the CNS produce proteins that inhibit regrowth and form glial scar tissue that blocks regrowth
Describe nerve regeneration in the PNS specifically.
- Axon in PNS is severed
- Distal part of axon degenerates
- Schwann cells survive and from a regeneration tube
- The regeneration tube releases chemicals that attract growing axon
- The regeneration tube guides the regrowing axon to synaptic site
What are 3 things important about neurotrophins?
- Promote fetal nerve growth
- Required for survival of many adult neurons
- Important for regeneration
What is the most abundance glial cells?
Astrocytes
What are the 5 things astrocytes are involved in?
- Buffering K+ levels
- Recycling neurotransmitters
- Regulating adult neurogenesis
- Releasing transmitters that regulate neuronal activity
- Blood brain barrier
What is the function of blood brain barrier?
Allows only certain compounds to enter the brain
How is the blood brain barrier formed?
Capillary Specializations in the brain
What do the capillary specializations in the brain appear to be induced by?
Astrocytes
What is the difference between the capillaries in the brain and the capillaries in the body?
The capillaries in the brain are not as leaky
What allows the capillaries in the brain to be not as leaky as the ones in the body?
The gaps between adjacent cells are closed by tight junctions
At rest, cells have an ______ internal charge, and _____ distribution of ions
- Negative
2. Unequal
What 3 things does the negative internal charge, and unequal distribution of ions of cells at rest result from?
- Large anions being trapped inside cell
- Na+/K+ pump and limited permeability keep Na+ high outside cell
- K+ is very permeable and is high inside cell Attracted by negative charges inside
What can excitable cells do? How?
- Discharge their RMP quickly
2. Rapid changes in the permeability to ions
Which cells in the entire body can be classified as excitable? Why do they do this?
- Neurons and muscle cells
2. To generate and conduct impulses
How are membrane potential changes measured?
by placing 1 electrode inside cell and 1 outside
What is another name for depolarization?
Hypopolarization
Why is depolarization called depolarization?
Because the potential difference becomes REDUCED(MO becomes more positive)
When does depolariztaion occur?
When MP becomes more positive
When does hyperpolarization occur?
MP becomes more negative than RMP
When does repolarization occur?
MP returns to RMP
In terms of excitatory and inhibitory, what is depolarization and repolarization?
- Depolarization= excitatory
2. Repolarization= inhibitory
How do membrane potentials occur?
Ions flow through membrane channels
Some membrane ion channels are normally ____, while some are ____.
- Open
2. Closed
K+ leakage channels are always _____.
Open
Closed channels have ____ ____ that can be opened
molecular gates
How are voltage-gated (VG) channels opened?
By depolarization
Does K+ have leakage or VG channels?
Both
Does Na+ have leakage or VG channels?
VG channels
In resting cells, are VG K+ and Na+ closed or open?
Closed
Is the cell more permeable to K+ or Na+? Why?
K+ because of leakage channels
What is action potential?
Is a wave of MP change that sweeps along the axon from soma (cell body) to synapse
How is the action potential wave formed?
formed by rapid depolarization of the membrane by Na+ influx; followed by rapid repolarization by K+ efflux
Broadly list the 3 steps in the mechanism of an action potential.
- Depolarization
- Repolarization
- After action potential: Na+/K+ pump
Describe the depolarization step in detail in regards to the mechanism of an action potential.
- Threshold occurs: VG Na+ channels open
- Na+ is driven inward into cell by its electrochemical gradient (this occurs via diffusion)
- This stimulates a positive feedback loop, ADDING to depolarization, opening even more channels
- Change in MP from -70mV to +30mV occurs