A&P 1 Exam 4

Nervous Tissue and Brain and Cranial Nerves

Neuron

Highly specialized cells that are the structural units of the nervous system

Neuroglia (Glial Cells)

smaller but more numerous than neurons, support the neuron and are essential for the survival and functionality of the neuron

Neuron Characteristics

Extreme longevity, large amitotic, and have a exceptionally high metabolic rate

Neuron Structure (Multipolar Neuron)

Cell body, dendrites, axon, and telodendria

Cell Body (Soma)

Contains the nucleus

Dendrites

Short and branched processes

Axon

A single long process

Telodendria

Terminal branches of the axon

Neurofibrils

Bundles of neruofilaments

Cytoskeleton of Soma Consists of

Neurofilaments (intermediate filaments), neurotubules (mircotubules), and microfilaments

Cytoskeleton

Is important in maintaining cell shape and structural integrity, and assist in moving materials between soma and axon (microtubules)

Nissl Bodies (gives soma gray color)

Free ribosomes and rough endoplasmic reticulum

Nuclei

Clusters of cell bodies in the central nervous system

Ganglia/Ganglion

Clusters of cell bodies in the peripheral nervous system

Dendrites (Contain many Receptors for Chemical Messengers)

Convey information toward the soma

Dendritic Spines (Points of Contact with other Neurons)

Thorny appendages having bulbous or spiky ends at the end of each dendritic branch

Graded Potentials

Short distance electrical signals that travel to soma

Axon

Capable of generating and propagating an action potential away from the soma

Axoplasm

Cytoplasm of axon

Axolemma

Plasma membrane of axon

Axon Hillock

Thickened cone shaped area of the soma that joins the initial segment of axon

Axon Collaterals (Collaterals)

Side branches along the length of the axon

Telodendria (Terminal Arborizations, Terminal Branches)

Branches of the axon

Synaptic Knob (Synaptic End Bulb, Axon Terminal, or Synaptic Terminal)

Ends of the axon that serve as the secretory component that exocytose neurotransmitters into the synaptic cleft

Trigger Zone (TZ)

Axon hillock and initial segment of axon

Axoplasmic Transport

Movement along the axon

Anterograde Movement (Anterograde Flow)

Movement toward the axonal terminal

What carries out Anterograde Movement

Kinesin a type of motor protein that travels along the microtubules

Retrograde Movement (Retrograde Flow)

Movement toward the cell body

What carries out Retrograde Movement

Dynein a type of motor protein that moves cargo back to the cell body along microtubules.

Sensory Input (Input = Afferent)

Gathering information from various sensory receptors inside and outside the body to monitor any changes

Integration

Processing and interpreting the incoming information from the sensory input

Motor Output (Output = Efferent)

Effects a response by activating or suppressing muscles, organs, glands, and tissues or effectors

Nervous System

Master controlling and communicating system of the body

Parts of Nervous System

Central nervous system and the peripheral nervous system

Central Nervous System

Consists of the brain and spinal cord

Peripheral Nervous System (All neural tissue outside of the CNS) Divisions

Afferent division and efferent division

Afferent Division of Peripheral Nervous System

Somatic afferent, special sense organs, and visceral afferent

Somatic Afferent

Sensory receptors from skin, skeletal muscle, and joints

Visceral Afferent

Sensory receptors from organs, tissues, and smooth muscle

Somatic Sensory Neurons

Monitor external environment and position within it

Visceral Sensory Neurons

Monitor internal environment and status of other organ systems

Efferent Division

Autonomic nervous system and somatic nervous system

Autonomic Nervous System

Involuntary nervous, visceral motor neurons

Autonomic Nervous System Divisions

Sympathetic division and parasympathetic division

Somatic Nervous System

Voluntary nervous system, somatic motor neurons

Sympathetic Division

Flight or fight

Parasympathetic Division

Rest and digest

Functions of the Central Nervous System

Process and coordinate, and is involved in higher brain functions

Peripheral Nervous System Function

Carry sensory information to the CNS and motor commands from the CNS

Cranial Nerve I

Olfactory nerve

Cranial Nerve II

Optic nerve

Cranial Nerve III

Oculomotor nerve

Cranial Nerve IV

Trochlear nerve

Cranial Nerve V

Trigeminal nerve

Cranial Nerve VI

Abducens nerve

Cranial Nerve VII

Facial nerve

Cranial Nerve VIII

Vestibulocochlear nerve

Cranial Nerve IX

Glossopharyngeal nerve

Cranial Nerve X

Vagus nerve

Cranial Nerve XI

Accessory nerve

Cranial Nerve XII

Hypoglossal nerve

Cervical Nerves

C 1-8

Thoracic Nerves

T 1-12

Lumbar Nerves

L 1-5

Sacral Nerves

S 1-5

Coccygeal Nerve

C0

Synapse

Cell to cell connection

3 types of Synapses

Neuromuscular junction, neuroglandular junction, and neuron to neuron synapses

3 Types of neuron to neuron synapses

Axodendritic, axosomatic, and axoaxonic (axoaxonal)

Synaptic Cleft

The small gap that separates the presynaptic membrane and the postsynaptic membrane

Multipolar Neuron (most common, all somatic motor neurons)

Have very long axons and have multiple dendrites but one axon

Bipolar Neurons (rarest)

Found in special sensory organs like in sight, smell, hearing, and taste

Unipolar Neurons (Pseudo-unipolar, soma to one side)

Found in sensory neurons of the PNS, have long axons that are fused to dendrites

Unipolar Neuron Peripheral Process

Part of axon before the soma, action potential towards soma

Unipolar Neuron Central Process

Part of the axon after the soma, action potential away from soma

Purkinje Cell (Multipolar Neuron)

Found in cerebellum

Pyramidal Cell (Multipolar Neuron)

Found in cerebral cortex

Functional Classification of Neurons

Sensory (afferent) neurons, motor (efferent) neurons, and interneurons (association neurons)

Sensory (Afferent) Neurons

Transmit impulses from sensory receptors, almost all are unipolar neurons with the exception of special sense organs which are bipolar

Motor (Efferent) Neurons

Carry impulses away from the CNS to effectors and are all multipolar neurons

Interneurons (Association Neurons)

Outnumber all other types of neurons combined, are mostly in the CNS and facilitate communication between sensory and motor neurons, mainly multipolar neurons but are diverse in size and branching patterns

Types of Sensory Receptors

Interoceptors, exteroceptors, and proprioceptors

Interoceptors

Provide information about internal environment

Exteroceptors

Provide information about external environment

Proprioceptors

Monitor position and movement

Nueroglia

Cells that support and protect neurons, they are small abundant, diverse and account for nearly half of the volume of the nervous system

Neuroglia type distribution

4 in the central nervous system and 2 in the peripheral nervous system

Neuroglia in the Central Nervous System

Ependymal cell, microglia, astrocyte, and oligodendrocyte

Ependymal Cells

Simple cuboidal or columnar epithelia (ependyma) that line the central canal and ventricles producing ependymal cerebrospinal fluid and form the blood CSF barrier

Cerebrospinal Fluid

Continuously circulates transporting nutrients and wastes, and provides cushion

Microglia

Smallest sparse phagocytic cells that monitor neuron health by touching them with long “thorny” processes, are mobile

Astrocytes

Neuroglia with processes that wrap around blood capillaries maintaining a blood brain barrier to control interstitial environment, they repair damaged neural tissue and have a role in influencing formation of neuronal synapses

Oligodendrocytes

Play a role in structural organization by tying clusters of axons together and improve function by wrapping axons forming a myelin sheath

Myelinated Axons

White matter of the central nervous system

Unmyelinated Axons

Gray matter of the central nervous system

Internodes

Myelinated segments of axon

Nodes (Nodes of Ranvier)

Gaps between internodes and site of where axons my branch known as collaterals

Neuroglia in the Peripheral Nervous System

Satellite Cells (Amphicytes), and Schwann Cells (Neurolemma Cells)

Satellite Cells (Amphicytes)

Surround cell bodies within ganglia regulate environment around neuron like astrocytes