Nerves Flashcards
What are the 3 overlapping functions of the nervous system
Stimuli (sensory input)
Integration
Effects (motor output)
How do nerves send communication
Electrical impulses
Nervous system does not work alone. What does it work with and how do they differ
Endocrine system.
Nervous system is faster by effecting change through electrical impulses where as the endocrine system effects change by releasing hormones into the blood stream, a much slower process.
What are the 2 structural classifications which include all nervous system organs and explain the difference
CNS (central nervous system)- consists of only the brain and the spinal cord. They interpret incoming sensory information.
PNS (peripheral nervous system)- nervous system outside the CNS. consists mainly of the nerves that extend from the brain and spinal cord.
What are the 2 functional classifications of the PNS and what do they do
Sensory (afferent) division- has sensory receptors located in various parts of the body such as skin, skeletal muscles and joints which are somatic sensory and the visceral sensory fibers which transmit impulses from the visceral organs.
Motor (efferent) division- carries impulses from the CNS to the organ, muscle, gland that the effect it to bring a motor response (movement)
Sensory and Motor divisions have 2 subdivisions. What are they and what are the difference.
Sensory:
- Somatic sensory-located in skin, skeletal muscles and joints
- Visceral sensory- transmits impulses from the visceral organs.
Motor:
- Somatic- voluntary , or conscious control. Also known as the voluntary nervous system
- Autonomic- automatic or involuntary such as smooth muscle, cardiac, glands. Also known as involuntary nervous system
What are the 2 principal types of cells nervous tissue is made up of
Neurons and supporting cells
Supporting cells in the CNS are called???
Neuroglia (nerve glue)
What are the 4 functions of neuroglia
- To surround neurons and hold them in place
- To supply nutrients and oxygen to neurons
- To insulate one neuron from another
- To destroy pathogens and remove dead neurons
Name the 4 glia cells of the CNS and what they do
- Astrocytes -nearly half neural tissue. They form a living barrier between capillaries and neurons as well as the nutrient supply line making exchanges between the two. Also help control chemical environment by picking up excess ions and recapturing released neurotransmitters
- Microglia- spider-like phagocytes that dispose of debris (dead brain cells, bacteria)
- Ependymal cells- Lines the cavities of the brain and spinal cord (extracellular matrix). The beating of the cilia helps circulate the cerebrospinal fluid that fills those cavities that form a protective cushion
- Oligodendrocytes- wrap flat extensions around the nerve fiber producing a fatty insulation coverings (myelin sheath)
What are the 2 main difference between neuroglia and neurons
neurolgila do not transmit electrical impulses but do not lost the ability to divide
neurons do transmit electrical impulses but lose their ability to divide.
Neuroglia won’t come back though if neuron is dead
Two major varieties of supporting cells in the PNS
Schwann cells- form myelin sheaths around nerve fibers
Satellite cells- act as protective, cushioning cells
There are 2 cells of the CNS and of the PNS that do the same job in each area. What are they
Ependymal Cells (CNS)- Satellite cells (PNS) Oligodendrocytes (CNS) - Schwann cells (PNS)
Which part of the nerve cell brings impulses to the cell body and which carries them away
Dendrites bring impulses to the body
Axons conduct them away
Which is more plentiful on a nerve cell, axon or dendrite
There can be hundreds of dendrites but always only one axon
What is released at the axon terminals at the end of a nerve cell
Neurotransmitters are released into the extracellular space
What are neurons separated by and what is the junction called
Separated by a synaptic cleft, junction is called a synapse
What does the myelin sheath do
protects and insulates the fibers and increases the transmission rate of nerve impulses
Is the myelin sheath made of schwann cells a long continuous sheath??
No, it has gaps called Nodes of Ranvier at regular intervals
What happens when myelin sheaths are destroyed
they sheaths around the fibers are converted into hardened sheaths called sclerosis. The transmission is short circuited causing loss of muscle control
What are the names of the bundles of nerve fibers running through the CNS? PNS?
CNS=tracts
PNS=nerves
What is the main difference between white matter and gray matter in the CNS
White matter consists of dense collections of the myelinated fibers (tracts)
Gray matter contains mostly unmyelinated fibers and cell bodies
What are a small collection of cell bodies found in a few sites in the CNS and PNS called
Ganglia
What does the myelin sheath consist of
80% lipid 20%protein
What is the difference of the myelin sheath made by the Oligodendrocyte and the Schwann cells
One Oligodendrocyte is able to put covering on up to 60 axons where as the Schwann cell can only wrap around one
What does the Oligodendrocyte not have that the Schwann cells do
Neurilemma (the outermost nucleated cytoplasmic layer of Schwann cells)
What does the neurilemma help with in the PNS
If the neurilemma remains intact (for most part) when a peripheral nerve fiber is damaged, it plays an important role in fiber regeneration, something lacking in CNS
What are 5 of the sensory receptors found in the skin
Naked nerve endings ( Pain and temp receptors) Meissners corpuscle (touch receptor) Pacinian corpuscle (deep pressure receptor or vibration) Golgi tendon organ ( proprioceptor) Muscle spindle ( proprioceptor)
Which sensory receptor is the most numerous
Naked nerve endings (Pain receptors)
What is the main job of the proprioceptors
to constantly advise our brain of our own movements
Where are the cell bodies of the motor neurons located
CNS
What are the structural classifications of neurons
Multipolar -most common, usually in motor and association neurons
Bipolar- composed of an axon and a dendrite, found only in some special sense organs (eye,ear)
Unipolar - single process emerging from the cell body, very short and divides almost immediately into proximal (central) and distal (peripheral) fibers. Sensory neurons found in the PNS ganglia are unipolar
A resting neuron is polarized or depolarized and explain
polarized, there is more potassium on the inside and more salt ions on the outside. Until the plasma membrane is semi permeable to salt ions, it will remain at rest
Explain how transmitting a nerve impulse through irritability works
an inactive neuron is polarized with more potassium ions on the inside of the cell and more sodium ions in the tissue fluid on the outside of the cell. When the neuron is stimulated (neurotransmitters), the plasma membrane becomes permeable to sodium for a brief period. Sodium quickly diffuses into the cell causing the depolarization of the neuron so that it can transmit an action potential or nerve impulse. Almost immediately after the sodium ions rush into the neuron, the membrane changes and becomes impermeable to sodium ions again. The potassium ions at this time are able to rush out of the neuron to balance or restore the initial electrical conditions at the membrane bringing the neuron back to resting state called repolarization. After this, the original concentrations of sodium and potassium are restored by activation of sodium potassium pump which uses ATP
How does the electrical impulse traveling along one neuron get to the next neuron (or effector cell) to influence its activity
It doesn’t!!! When action potential reaches the axonal endings, the axonal terminals release the neurotransmitter chemical, which diffuses across the synapse and binds to receptors on the membrane of the next neuron.
How are neurotransmitters removed
Either by re-uptake into the axonal terminal or by enzymatic breakdown
What is the transmission of an impulse from one neuron to the next considered
electrochemical event
Define Reflexes
rapid, predictable and involuntary responses to stimuli
What are the two types of reflexes and explain
autonomic-regulate the activity of smooth muscles, hear and glands, eg: Secretion of saliva, changes in size of pupil
somatic relflexes- all reflexes that stimulate the skeletal muscles.
What are the 5 minimum elements all reflex arcs have
- a sensory receptor
- an effector organ
- afferent and efferent neurons that connect the two
- synapse between the afferent and efferent neurons that represents element
- CNS integration center
