STRUCTURAL AND FUNCTIONAL ORGANIZATION OF NERVOUS TISSUE Flashcards
Describe the main structures of the nervous system.
Brain
Spinal Cord
100 billion neurons
Brain
100 million neurons
Spinal Cord
CNS Parts
Brain
Spinal Cord
PNS Parts structural (5)
Cranial Nerves
Spinal Nerves
Sensory Receptors
Ganglia
Enteric Plexus
Cranial Nerves how many
12 pairs of cranial nerves numbered I-XII that emerge from the base of the brain
Spinal Nerves how many
31 pairs of spinal nerves that emerge from the spinal cord each serving a specific region of the body
Sensory Receptors
Specialized cells that monitor change in the internal and external
environment.
Example: Photoreceptors in the retina of the eye.
Ganglia
Small masses of nervous tissue consisting of neuronal cell bodies that
are located outside the brain and spinal cord.
Example: Dorsal root
ganglion
Enteric Plexus
are located in the walls of the
GI Track that help regulate the digestive system.
Three basic function of the Nervous system.
a. Sensory function afferent
b. Integrative function: Information processing
c. Motor function (Efferent)
What is Sensory function of afferent
internal and external stimuli and carry information into brain and spinal cord
Integrative function:
1) Perception = awareness of sensory input
2) Analyzing and storing information to help lead to appropriate responses
Motor function (Efferent)
brain may elicit motor response to muscles or
glands (effectors)
Nervous tissue consists of two cells
Neurons
Neuroglia
Neurons cells
Provide most of the unique functions of the nervous system
Neuroglia cells
Function to provide support, nourishment, and protection
Parts of a Neuron [3] structural
Cell body
Dendrites
Axon
Axon terminals
Axon emerge from what structure?
cone-shaped axon hillock
Structural Classes of Neurons 3 types
Multipolar
Bipolar
Unipolar
Multipolar
Most common type in brain and spinal cord
Bipolar neurons
1) Have one dendrite and one axon
2) Example: In retina of eye and inner ear
Unipolar
1) Have fused dendrite and axon
2) Sensory neurons of spinal nerves
What are the Functional Classes of Neurons 3 types
Sensory (afferent)
Motor (efferent)
Interneurons (association neurons)
Sensory (afferent) Neurons
Convey impulses into CNS (brain or spinal cord)
Motor (efferent) nerons
Convey impulses from brain or spinal cord out through the PNS to
effectors (muscles or glands)
Interneurons (association neurons)
1) Located within the CNS
2) Transmit impulses between neurons, such as between sensory and
motor neurons
Neuroglia Cell characteristics
(a) Support, nourish, and protect neurons
(b) Critical for homeostasis of interstitial fluid around neurons
(c) Cells smaller but much more numerous than neurons
(d) Make up about half the volume of the CNS
(e) Functions:
1) Do NOT generate or conduct nerve impulses
2) Support, nourish and protect neurons
3) In case of injury or disease, neuroglia can multiply to fill in space
formerly occupied by neurons
Types of Neuroglia Cells:
Oligodendrocytes
produce myelin in CNS (CNS)
Types of Neuroglia Cells (6)
1) Astrocytes
2) Oligodendrocytes
3) Microglia
4) Ependymal
5) Schwann cells
6) Satellite cells
Types of Neuroglia Cells:
Microglia
Protects CNS cells from disease (CNS)
Types of Neuroglia Cells:
Ependymal Cell
Ependymal cells form CSF in the ventricles (CNS)
Types of Neuroglia Cells:
Schwann Cell
Produce myelin around PNS neurons (PNS)
Types of Neuroglia Cells:
Satellite cells
Support neurons in PNS ganglia (PNS)
Types of Neuroglia Cells:
Astrocytes
Form a blood-brain barrier (CNS)
Myelination
(a) A myelin sheath surrounds most axons
(b) Insulates the axon and speeds up the nerve impulse
(c) Myelin increases from birth to maturity
(d) Nodes of Ranvier: Gaps in myelin along the axon
(e) Diseases such as Multiple Sclerosis and Tay-Sachs destroy myelin sheaths
What is the Clusters of neuron cell bodies in pns and cns
Ganglion: PNS
Nucleus: CNS
Bundles of axons
Nerve: PNS
Tract: CNS
What is White matter made of
Primarily myelinated axons
Gray matter
Cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia
Can PNS neurons regenerate?
Yes; with intact Schwann cells funtional
CNS neurons Regeneration?
1) Very limited even if cell body is intact
2) Inhibited by neuroglia and by lack of fetal growth-stimulator cues
Action Potential are?
nerve impulses, allow for communication between neurons
A resting membrane potential charge?
polarizated
Channels that allow ions to leak through
Leakage
channels open and close on command
Gate
What is the Action potentials series of events
STIMULUS
1.Triggers resting membrane to become more permeable to Sodium (Na+)
- Causes enough Na+ to enter cell so that cell membrane reaches threshold (~
–55 mv)
Depolarizing phase
3. Voltage gated Na+ channels open ~ as more Na+ enters cell, membrane
potential rises and becomes positive
Repolarizing phase
4. Voltage gated K+ channels open ~ as more K+ leave cell, membrane
potential is returned to resting value
- Hyperpolerizing occurs to -70mV
Types of conduction
Continuous conduction
Saltatory conduction
Continuous conduction
a) Unmyelinated axons, currents flow across adjacent portions of the
plasma membrane
b) Slower form
Saltatory conduction
Myelinated axons, Nodes of Ranvier allow impulses to “leap” from
Synaptic Transmission are?
Triggered by action potential (nerve impulse)
Synapses allow neurons to communicate with other neurons or effectors
Neuromuscular junction
(neuron-muscle fiber)
Neuroglandular junction
(neuron-gland)
Components of synapse:
1) Presynaptic neuron: Sending neuron (releases neurotransmitter)
2) Synaptic cleft: Space between neurons
3) Postsynaptic neuron: Receiving neuron (has receptors that bind to
neurotransmitter)
Synaptic Transmition Cycle
Neurotransmitters 5 types
(a) Acetylcholine (ACh): Common in PNS
(b) Amino acids
(c) Modified amino acids
1) Norepinephrine (NE), dopamine (DA), serotonin
(d) Neuropeptides such as endorphins
(e) Nitric oxide (NO)
Central Nervous Tissue location and function
(a) Consists of the brain and spinal cord
(b) Source of thoughts, emotions, and memories
Peripheral Nervous Tissues
Includes all the nervous tissue outside the central nervous system
1) Include the cranial nerves, spinal nerves, ganglia and sensory nerves
Somatic Nervous System
Autonomic nervous system
Enteric Nervous System
Somatic Nervous System
1) Sensory neurons: Convey info from head, body wall, and limbs
and from receptors for special senses (vision, hearing, taste smell)
to CNS
2) Motor neurons: Conduct impulses from CNS to skeletal muscles
(voluntary control)
Autonomic nervous system
1) Sensory neurons: Convey information from receptors in the
visceral organs (stomach and lungs) to CNS
2) Motor neurons: Conduct impulses from CNS to smooth muscles,
cardiac muscles, and glands (involuntary control)
PNS ANS Motor neruons are divided into wat 2
Sympathetic: “fight or flight”
Parasympathetic: “rest and digest”
