the nervous tissue Flashcards by Chloe Unknown

deals with normal functioning and disorders of the nervous system.

Neurology

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neurons enclosed within skull

brain

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bundles of many axons of neurons

nerves

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connects to brain and enclosed
within spinal cavity

Spinal cord

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groups of neuron cell bodies located outside of brain and spinal cord

Ganglia

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a physician who diagnoses and treats disorders of the nervous system.

Neurologist

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one of the smallest and yet the most complex of the 11 body systems

nervous system

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(12 pairs) emerge from brain

cranial nerves

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(31 pairs) emerge from spinal cord

Spinal nerves

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networks in digestive tract

Enteric plexuses

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monitor changes in internal or external environments

Sensory receptors

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Functions of the Nervous system

Sensory (input)
Integration (process)
Motor activity (output)

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Carry information into brain and spinal cord

Sensory

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Analyzing and storing information to help lead to appropriate responses

Integration

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awareness of sensory input

perception

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Signals to muscles and glands (effectors)

Motor activity

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Structural Classes of Neuron

Multipolar
Bipolar
Unipolar

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Organization of the Nervous System

Central nervous system (CNS)
Peripheral nervous system (PNS)

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Divisions of Peripheral nervous system (PNS)

Somatic (SNS)
Autonomic (ANS) nervous systems
Enteric nervous system (ENS)

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HISTOLOGY OF NERVOUS TISSUE
Two cell types

Neurons
Neuroglia cells

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Parts of a Neuron

Cell body (perikaryon or soma)
Dendrites
Axon

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Functional Classes of Neuron

Sensory (afferent)
Motor (efferent)
Interneurons (association neurons)

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Neuroglia of the CNS (4 types)

Astrocytes
Oligodendrocytes
Microglia.
Ependymal cells

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Structures of the Nervous System

Brain
Spinal cord
Nerves
Ganglia
Enteric plexuses
Sensory receptors

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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)