Nervous Tissue Flashcards
What are the 3 steps of nervous function?
- Sensory input
- Integration
- Motor output
(SIM)
What are the 2 basic parts of the whole (integrated) nervous system?
CNS and PNS
central nervous system and peripheral nervous system
What are nerves made of?
Bundles of axons
What are ganglia?
Small clusters of neuron cell bodies OUTSIDE the CNS
What are the 2 divisions of the peripheral nervous system (PNS)?
- Afferent (sensory)
2. Efferent (motor)
What are the 2 divisions of the motor (efferent) division of the PNS?
- Somatic nervous system
2. Autonomic nervous system (ANS)
What are the 2 divisions of the autonomic nervous system (ANS)?
Sympathetic and parasympathetic divisions
What does the PNS (peripheral nervous system) do?
What is it made of?
Communicates btw the CNS and the rest of the body
Made of cranial nerves and spinal nerves
What is the sensory (afferent) difision of the PNS made of?
Somatic and visceral sensory nerve fibers
What is the motor (efferent) division of the PNS made of?
Motor nerve fibers
How do the sensory (afferent) division and the motor (efferent) division of the peripheral nervous system work together?
Sensory (afferent) picks up messages in receptors and transmits signals to the CNS
Motor (efferent) takes messages from CNS to effectors (muscles and glands) if action is required
Is the somatic nervous system voluntary or involuntary?
Voluntary
What is the function of the somatic nervous system?
It conducts impulses from the central nervous system to the skeletal muscles
CNS –> skeletal muscles
Is the autonomic nervous system voluntary or involuntary?
Involuntary
What is the function of the autonomic nervous system (ANS)?
Conducts impulses from the CNS to involuntary muscles, e.g. cardiac muscles, smooth muscles, and glands
What does the sympathetic division of the autonomic nervous system (ANS) do?
It mobilizes body systems during activity
What does the parasympathetic division of the autonomic nervous system (ANS) do?
It conserves energy - housekeeping functions performed at rest
What is the enteric nervous system (ENS)?
The “brain of the gut”
Senses change in GI tract and controls GI smooth muscle and glands involuntarily
What are the 3 basic parts of a neuron?
- Cell body
- Dendrites
- Axon
What are Nissl bodies? What part of the neuron are they found in?
Clusters of endoplasmic reticulum - sites of protein synthesis
In the cell body of a neuron
What do microtubules do in the cell body of a neuron?
Microtubules move materials between the cell body and the axon
What part of the axon is the trigger zone?
Initial segment of axon where impulses arise
What is a synapse?
The communication site between
- a neuron and
- an effector cell (another neuron, a muscle fiber, a gland, etc.)
What is the difference between unipolar, bipolar, and multipolar neurons?
of dendrites/processes
Unipolar - one process formed by fusion of axon and dendrite (pain receptors of skin)
Bipolar - one dendrite and one axon (special senses)
Multipolar - multiple dendrites (brain and spinal cord)
Astrocytes, oligodendrocytes, microglia, and ependymal cells are all example of cells found in the CNS or PNS?
CNS
What do astrocytes do?
Support metabolic and functional needs of neurons
Forms blood-brain barrier (protects neurons)
What do oligodendrocytes do?
Produce myelin sheath in CNS
What do microglia do?
Phagocytic cells of CNS
What do ependymal cells do?
They line fluid-filled cavities and help produce and circulate cerebrospinal fluid
What are the 2 types of neuroglia found in the peripheral nervous system?
- Schwann cells
2. Satellite cells
What do Schwann cells do in the PNS?
They cover axons or produce myelin sheath in the PNS
What do satellite cells do?
Satellite cells surround the cell bodies in ganglia, maintaining the proper environment for neurons
What are the Nodes of Ranvier?
Spaces btw myelin sheaths
Increases speed of impulse conduction
Saltatory effect (jumping)
Why is white matter white?
Myelin sheaths
What is gray matter made of?
Cell bodies (of neurons)
Dendrites
Unmyelinated axons
Spinal cord vs. brain - gray/white matter superficial/deep?
Spinal cord: gray = deep, white = superficial
Brain: white = deep, gray = superficial
What are axon collaterals?
Branches off of the main the axon of a neuron - the branches go to other cells. These axon collaterals end in axon terminals of their own.
What are axon terminals? Aka telodendria?
telo-dendria
Branched ENDS of axons
When dendrites receive incoming messages TOWARD the cell body of the neuron, what kind of electrical signals are they? Action potential or graded potential?
Graded potential
What is a nerve fiber?
A long axon, like the ones that stretch from your spinal cord to your feet
What is the axolemma of an axon?
The plasma membrane of the axon
What is the synaptic end bulb of an axon?
It’s the bulb-shaped end of the axon terminal that forms synapses with the effectors/post-synaptic neurons
What do synaptic vesicles carry?
Neurotransmitters
What is axonal transport?
Recycling trucks - transport of used materials back to cell body for recycling
What special neurological ability does the hippocampus have in the brain that distinguishes it from other areas of the brain and spine (CNS)?
Hippocampus can generate new neurons - important for learning
Rest of CNS can’t generate new neurons
What is Wallerian degeneration?
Part of axon repair - distal axon deteriorates and cell eats itself (macrophages)
What is resting membrane potential?
Electrical voltage difference across a membrane
- Due to differing concentration of ions
- Lipid bilayer is such a good insulator that it keeps the charges separate
What type of ion channels are leakage channels?
They open channels for specific ions
What type of ion channels are chemically-gated channels?
Open or close in response to particular chemical stimulus, e.g. neurotransmitters or hormones
What type of ion channels are mechanic-gated channels?
Open or close in response to mechanical forces (pressure, sound waves, stretching…)
What type of ion channels are voltage-gated channels?
They open or close in response to a change in membrane potential.
Is a resting neuron more negative on the inside, or more positive on the inside (as compared to the outside environment)?
Neuron is more negative inside
What is the resting membrane potential? What is the average value of it in mV?
Difference in charge btw inside and outside the axon of neuron
-70 mV
Outside of neuron, do we see more sodium or potassium?
Sodium ions (positive)
Inside of the axon of a neuron, do we see more sodium or potassium?
Potassium ions (positive) with bigger negatively charged protein, so overall charge is negative
Sodium potassium pump - which goes ion goes into the cell, and which goes out?
2 potassium ions in
3 sodium ions out
Overall positive flow outward
What is an action potential?
When there is a big enough difference in membrane potential to trigger voltage gated channels
Achieved by depolarizing resting neuron
What is the threshold voltage?
-55 mV
What is depolarization?
So much sodium rushes in b/c voltage-gated sodium channels have opened that the cell becomes depolarized (goes positive inside)
What is repolarization?
After depolarization, voltage-gated potassium ions open, potassium flows out, but too much to hyperpolarization, then sodium potassium pumps kick in and bring things back to resting
What are the 2 ways that action potentials can be propagated? Which is faster?
Continuous propagation or saltatory (leaping) propogation. Saltatory is faster b/c it jumps from one Node of Ranvier to another
What is the difference between A, B, and C nerve fibers? Relative size (small-med-large)? Speed? Are they myelinated?
A - largest, myelinated, fastest
B - medium, myelinated
C - smallest, unmyelinated, slowest
Do excitatory postsynaptic potentials (EPSP) depolarize or hyperpolarize the cell membrane?
ESPS depolarizes
Do inhibitory postsynaptic potentials (ISPS) depolarize or hyperpolarize the cell membrane?
ISPS hyperpolarizes
What is the synaptic delay?
The time lag between conversion from electrical to chemical signal and then back again
