C11 1-8 Flashcards
List the basic functions of the nervous system.
SENSORY INPUT - INTEGRATION - MOTOR OUTPUT
Sensory input
sensory receptors detect changes in the internal and external environments.
Integration
the nervous system processes and interprets input and decides what should be done at each moment.
Output
the nervous system activates effector organs (muscles/glands) to cause a response
Two principle parts of NS?
CNS/PNS
CNS
Brain and spinal cord. The integrating and control center of the nervous system.
PNS
Nervous system outside of the CNS. The communication lines between the CNS and the rest of the body. Incl. cranial nerves - 12, and spinal nerves 31
Divisions of the PNS?
Sensory (afferent) division, Motor (efferent) division
Sensory division of PNS
Contains somatic and visceral sensory nerve fibers which conduct impulses from receptors TO the CNS. AFFERENT
Motor division of PNS
Contains motor nerve fibers which conduct impulses from the CNS to effectors (muscles/glands) EFFERENT
Divisions of Motor division?
Somatic/Autonomic
Somatic nervous system
Consists of somatic motor fibers that conduct impulses from the CNS to skeletal muscles. (aka voluntary NS)
Autonomic nervous system
Consists of visceral nerve fibers that regulate the activity of smooth and cardiac muscles, glands, adipose tissue and other involuntary tissue. (aka involuntary NS)
Divisions of the Autonomic NS?
Sympathetic, parasympathetic
Sympathetic?
Mobilizes body systems during activity (fight or flight, E division)
Parasympathetic?
Conserves energy, promotes housekeeping functions during rest. (rest and digest, salivation, lacrimation, urination, defacation)
Types of neuroglia in the CNS?
Astrocytes, microglia, ependymal cells, oligodendrocytes
Neuroglia?
(Or glial cells) Associated with neurons, provide a protective and supportive network
Astrocytes
-Most numerous -Control environment around neurons (mop up potassium, recapture and recycle neurotransmitters) -Make exchanges between capillaries and neurons helping determine cap permeability - form blood brain barrier
Microglia
-Defense cells - Processes touch nearby neurons monitoring their health - Perform immune functions (when invaders are present they transform into a special type of macrophage)
Ependymal cells
- Line the central cavities of the brain and spinal cord - Help in the production and circulation of CSF
Oligodendrocytes
- Wrap around neuron fibers forming myelin sheaths (fewer processes than astrocytes)
Satellite cells
Function largly unknown. Surround neuron cell bodies within ganglia. (PNS)
Schwann cells
(aka neurolemmocytes) Surround nerve fibers forming the myelin sheath. (PNS)
Types of neuroglia in the PNS?
Satellite cells, schwann cells
Six distinguishing features common to all neurons? Chasee
Conductivity, high metabolic rate, amitotic, secretion, excitability, extreme longevity
Define neuron
Specialized cells that conduct messages in the form of electrical impulses throughout the body
Structural components of a neuron?
Cell body, Neuron processes
What are clusters of neuron cell bodies called?
In the CNS, nuclei. In the PNS, ganglia.
Neuron processes?
Dendrites, axons
Cell body
aka perikaryon/soma. The major biosynthetic center containing the usual organelles except for centrioles.
Collections of axons are called?
Tracts in the CNS, Nerves in the PNS
Axon function
- Conducting region of the neuron.
- Generates nerve impulses and transmits them, typically away from the cell body.
- Secrete neurotransmitters.
Dendrite function
- Input regions that provide surface area for receiving signals from other neurons.
- Convey messages toward the cell body.
Describe Axon
1 Single axon per neuron
2 Starts with a axon hillock on the cell body, tapers into slender process, uniform for the rest of its length.
3 Occasionally has branches (axon collaterals)
4 Ends have terminal branches with synaptic knobs
Describe Dendrite
Short,
tapering,
diffusely branching extensions.
Anterograde movement
Movement away from the cell body.
Substances: mitochondria, cytoskeletal elements, membrane compnents.
Why: renew axon plasma membrane, and enzymes used to synthesize neurotransmitters (axon)
Retrograde movement
Movement toward the cell body.
Substances: organelles to be degraded or recycled.
Also intracellular communication to advise cell body of conditions at axon terminals and deliver cell body vesicles containing signal molecules. (axon)
Myelin sheath
Whitish, fatty, segmented covering
- protects
- electrically insulates fibers
- increases the transmission speed of nerve impulses. (axons only)
PNS myelin sheaths?
Formed by schwann cells, adjacent cells do not touch each other so there are gaps in the sheath (nodes of ravier)
CNS myelin sheaths?
Formed by oligodendrocytes, have multiple flat processes that can coil around as many as 60 axons at the same time. Myelinated fibers in CNS are “white matter”, grey matter cont. mostly cell bodies and nonmyelinated fibers.
Structural classes or neurons?
Multipolar, bipolar, unipolar
Functional classes of neurons?
Sensory/afferent, Motor/efferent, Interneurons/association
Multipolar neurons
Have 3 or more processes (brain and spinal cord)
Bipolar neurons
Single axon/single dendrite that extend from opposite sides of cell body. Rare, found in special sense organs (retina, inner ear, olfactory_)
Unipolar neurons
aka pseudounipolar, single process that branches - distal (peripheral) end is associated with a sensory receptor in PNS, the central process (proximal) enters the CNS. (touch, pain temp vibration)
Sensory/afferent neurons
Conduct impulses toward the CNS from receptors. Mostly unipolar with cell bodies that are located in sensory ganglia outside the CNS.
Motor/efferent neurons
Conduct impulses from the CNS to effectors. Multipolar
Interneurons/association neurons
Conduct impulses between sensory and motor neurons or in integration pathways. CNS only! 99% of neurons in body. Mostly multipolar, but lots of diversity in size and fiber-branch patterns.
