the nervous tissue Flashcards
deals with normal functioning and disorders of the nervous system.
Neurology
neurons enclosed within skull
brain
bundles of many axons of neurons
nerves
connects to brain and enclosed
within spinal cavity
Spinal cord
groups of neuron cell bodies located outside of brain and spinal cord
Ganglia
a physician who diagnoses and treats disorders of the nervous system.
Neurologist
one of the smallest and yet the most complex of the 11 body systems
nervous system
(12 pairs) emerge from brain
cranial nerves
(31 pairs) emerge from spinal cord
Spinal nerves
networks in digestive tract
Enteric plexuses
monitor changes in internal or external environments
Sensory receptors
Functions of the Nervous system
Sensory (input)
Integration (process)
Motor activity (output)
Carry information into brain and spinal cord
Sensory
Analyzing and storing information to help lead to appropriate responses
Integration
awareness of sensory input
perception
Signals to muscles and glands (effectors)
Motor activity
Structural Classes of Neuron
Multipolar
Bipolar
Unipolar
Organization of the Nervous System
Central nervous system (CNS)
Peripheral nervous system (PNS)
Divisions of Peripheral nervous system (PNS)
Somatic (SNS)
Autonomic (ANS) nervous systems
Enteric nervous system (ENS)
HISTOLOGY OF NERVOUS TISSUE
Two cell types
Neurons
Neuroglia cells
Parts of a Neuron
Cell body (perikaryon or soma)
Dendrites
Axon
Functional Classes of Neuron
Sensory (afferent)
Motor (efferent)
Interneurons (association neurons)
Neuroglia of the CNS (4 types)
Astrocytes
Oligodendrocytes
Microglia.
Ependymal cells
Structures of the Nervous System
Brain
Spinal cord
Nerves
Ganglia
Enteric plexuses
Sensory receptors
nervous system have mass of _____ and total body weight of ______
2 kg (4.5 lb), about 3%
100 billion neurons
brain
100 millionneurons
spinal cord
> all nervous system structures outside of the CNS
-includes nerves, ganglia, enteric plexuses, and sensory receptors
Peripheral Nervous System (PNS)
source of thoughts, emotions, and memories. and signals that stimulate muscles to contract and glands to secrete
Central Nervous System (CNS)
Can respond to stimuli and convert stimuli toelectrical signals (nerve impulses or actionpotentials) that travel along neurons
Neurons
support, nourish, and protect neurons
critical for homeostasis of interstitial fluid around neurons
continues to divide throughout an individual’s lifetime
Neuroglia cells
nucleus, cytoplasmwith typical organelles
Cell body
highly branched structures that carryimpulses to the cell body
> receiving or input portions of a neuron
Dendrites
conducts away from cell body toward another neuron, muscle or gland
Axon
contain synaptic vesicles that can releaseneurotransmitters
Axon terminals
> Have several or many dendrites and one axon
Most common type in brain and spinal cord
Multipolar
> Have one dendrite and one axon
Example: in retina of eye and inner ear
Bipolar
> Have fused dendrite and axon
Sensory neurons of spinal nerves
Unipolar
forms an action potential in its axon and theaction potential is conveyed into the CNS through cranial orspinal nerves. (unipolar)
Sensory (afferent)
convey action potentials away from the CNS to effectors (muscles and glands) in the periphery (PNS)through cranial or spinal nerves. (multipolar)
Motor (efferent)
integrate (process) incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate motor neurons. (multipolar)
Interneurons (association neurons)
Cells smaller but much more numerous than neurons
Neuroglia
brain tumors derived from neuroglia
gliomas
> Do not conduct nerve impulses
Do support, nourish and protect neurons
Neuroglia
Neuroglia of the CNS (4 types)
Astrocytes, Oligodendrocytes, Microglia, and Ependymal cells
help form blood brain barrier
Astrocytes
Two types of Astrocytes
> Protoplasmic astrocytes
-have many short branchingprocesses and are found in gray matter.
> Fibrous astrocytes
-have many long unbranched processesand are located mainly in white matter.
produce myelin in CNS
Oligodendrocytes
protect CNS cells from disease
> function as phagocytes
Microglia
form CSF in ventricles
Ependymal cells
important for rapid signal conduction
nodes
Axons covered with a myelin sheath
> Many layers of lipid and protein: insulates neurons
> Increases speed of nerve conduction
> Appears white (in white matter)
Myelination
bundle of axons in PNS
nerve
bundle to axons in CNS
tract
cluster of cell bodies in CNS
nucleus
cluster of cell bodies in PNS
ganglion
Clusters of neuron cell bodies
Ganglion
Nucleus
Bundles of axons
Nerve
&
Tract
cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia
Gray matter
primarily myelinated axons
White matter
Locations of gray and white matter
Spinal cord: white matter
Brain: gray matter
can be repaired if cell body is intact and Schwann cells functional
Regeneration of PNS neurons
Very limited even if cell body is intact
Regeneration of CNS neurons
a charge difference across cell membrane (polarization)
membrane potential
allow ions to move by diffusion from high to low concentration
Ion channels
four types of ion channels
> leak channels
ligand-gated channels
mechanically gated channels
voltage-gated channels
allow ions to leak through membrane
Leakage channels
opens and closes in response to the binding of a ligand (chemical) stimulus
Ligand-gated channel
opens or closes in response to mechanical stimulation in the form of vibration (such as sound waves), touch, pressure, or tissue stretching.
Mechanically gated channel
Resting Membrane Potential
-70mV
opens in response to a change in membrane potential (voltage). Participate in the generation and conduction of action potentials in the axons of all types of neurons.
voltage-gated channel
Neurotransmitters
Biogenic Amines
Acetylcholine (ACh)
Neuropeptides
Amino acids
Nitric oxide (NO)
on cardiac muscle
inhibitory
on skeletal muscles
stimulatory
Types of Conduction Nerve Impulses
Continuous conduction
> In unmyelinated fibers; a slower form of conduction
Saltatory conduction
> In myelinated fibers; faster as impulses “leap” between nodes of Ranvier
rest-and-digest
Parasympathetic
“fight-or-flight” or “fight-fright-flight”
Sympathetic
Sensory neurons from head, body wall, limbs, specialsense organs
Somatic (SNS)
Sensory neurons from viscera
Autonomic (ANS)
> “brain of the gut”
govern contraction of GI tract smooth muscle to propel food, secretions of the GI tract organs such as acid from the stomach, and activity of GI tract endocrine cells, which secrete hormones(involuntary
Enteric (ENS)