2025 Anatomy Test 4 Flashcards
Lectures 13-15: Nervous Tissue, Brain and ANS, Cranial + Peripheral Nerves
Nervous system characteristics
Controls and adjusts the activity of the body
Provides swift but brief responses
An Overview of the Nervous System
The nervous system consists of all the nervous tissue and includes:
Central Nervous System (CNS)
Associated with the brain and the spinal cord
Peripheral Nervous System (PNS)
Associated with the tissue outside the CNS
Central nervous system (CNS)
Responsible for integrating, processing, and coordinating sensory input
Responsible for integrating, processing, and coordinating motor output
It is the seat of intelligence, memory, learning, and emotion
Peripheral nervous system (PNS)
Provides sensory information to the CNS and carries motor commands away from the CNS
Can be divided into:
Afferent division
Brings sensory information to the CNS
Begins at the receptors
Efferent division
Carries motor commands to muscles and glands
Ends at the effectors
The peripheral nervous system (PNS) can be subdivided into:
Afferent
Can be further subdivided into somatic and visceral
Somatic - sensory from skin, skeletal muscles and joint
Visceral - internal organs, blood vessels and glands
Efferent
Can be further subdivided into somatic nervous system (SNS) and autonomic nervous system (ANS)
The autonomic nervous system can be further divided into: (Internal Viscera)
Parasympathetic division
Sympathetic division
Functional Overview of Nervous System
Nervous tissue consists of two cell types:
Neurons
Nerve cells that are responsible for the transfer and processing of information in the nervous system
Consist of a soma (cell body), axon, dendrites, perikaryon, dendritic spines, and axon terminals
Neuroglia (culmination of all other cells)
Supporting cells
Protect the neuron
** 5 Types
Types of Neuroglia of the CNS
Astrocytes: largest and most numerous/make up the blood brain barrier (BBB)
Oligodendrocytes: form myelin sheath/form internodes and myelin sheath gaps:
Areas with mostly myelinated axons are called white matter
Areas devoid of myelinated axons are called gray matter
Gray matter is also composed of cell bodies and dendrites
Microglia: these are phagocytic cells
Ependymal Cells: involved in cerebrospinal fluid (CSF) production
Make up a cellular lining called the ependyma
Peripheral Nervous System…
… has Schwan Cells as well = help make the myelin sheath of PNS
Histology of Nervous Tissue in CNS
Types of Neuroglia of the PNS
The cell bodies in the PNS are clustered in ganglia
Axons are bundled together to form peripheral nerves
There are two neuroglia types:
Satellite Cells: surround cell bodies
Schwann Cells: surround axons
Schwann cells are also called neurolemmocytes
Consists of:
Axolemma/neurolemma
Myelination
Nodes = Nodes of Ranvier
Neuron structure
Neurons consist of:
Perikaryon: neuron cytoplasm
Neurofilaments/Neurotubules: make up the neuron cytoskeleton
Neurofibrils: bundles of neurofilaments
Nissl bodies: clusters of free ribosomes
Axon hillock: area where the initial segment connects to the cell body
Axoplasm: cytoplasm of the axon
Collaterals: branches off the axon
Telodendria: ends of the axon and collaterals
Axon terminals: ends of the telodendrias
Axoplasmic transport: the movement of material between the cell body and the axons
Neuron Classification: Structural Classification of Neurons
Anaxonic
Has many processes but cannot differentiate between axons and dendrites
Found only in the CNS
Bipolar
The cell body is between the dendrite and axon
Axons are not myelinated
Structural Classification
Functional Classification of Neurons: Sensory (afferent division) Neurons
The axons are afferent fibers
Sends information from the PNS to the CNS
There are:
Somatic sensory neurons and visceral sensory neurons
There are three categories of receptors:
Interoceptors: monitor internal organ activity
Exteroceptors: provide information about the external environment
Proprioceptors: monitor position and movement
Functional Classification of Neurons: Motor Neurons
The axons are efferent fibers
Send information from the CNS to the periphery
Consist of two divisions:
Somatic nervous system (SNS): consists of somatic motor neurons
Autonomic nervous system (ANS): consists of visceral motor neurons
Also consists of: preganglionic fibers and postganglionic fibers
Functional Classification of Neurons: Interneurons
Located entirely in the CNS
Situated between the motor and sensory neurons
Analyze sensory input and coordinate motor outputs
Can be excitatory or inhibitory
Synaptic Communication
Nerves connect to other nerves
Nerves connect effector organ
A synapse is the junction between a neuron and another cell
Two major types of synapses:
Chemical synapse (vesicular)
Electrical synapse (nonvesicular)
Neuron Organization and Processing
Neurons can be organized into smaller organized groups called neuronal pools
The neuronal pools are identified by their neural circuit such as:
Divergence
Convergence
Serial processing
Parallel processing
Reverberation
Neuron Organization and Processing: Serial and Parallel
Neuron Organization and Processing: Reverberation
Anatomical Organization of the Nervous System
Neurons in the PNS
Consist of ganglia
Axons are bundled together in nerves
Neurons in the CNS
Collection of cell bodies called a center
If this center has a distinct boundary, it is called a nucleus
White matter consists of axons in bundles called tracts and columns
Autonomic nervous system (ANS)
The autonomic nervous system (ANS) functions outside of our conscious awareness
The autonomic nervous system makesroutine adjustments in our body’s systems
The autonomic nervous system:
Regulates body temperature
Coordinates cardiovascular, respiratory, digestive, excretory, and reproductive functions
A Comparison of the Somatic and Autonomic Nervous Systems
Autonomic nervous system
Has afferent and efferent neurons
Efferent axons innervate the visceral organs
Preganglionic axons synapse on postganglionic neurons at a ganglion
A ganglion is a group of neurons outside of the central nervous system
Autonomic nervous system
Afferent pathways originate at visceral sensory receptors
Somatic nervous system
Has afferent and efferent neurons
Efferent axons innervate the skeletal muscles
Somatic motor neurons do not involve ganglia
Somatic nervous system
Afferent pathways originate in the skeletal muscles, joints, and skin.
A Comparison of the Somatic and Autonomic Nervous Systems
Sympathetic and Parasympathetic Subdivisions of the ANS
The autonomic nervous system consists of two major subdivisions
Sympathetic division
Also called the thoracolumbar division
Most active during times of stress, exertion, or emergency
Parasympathetic division
Also called the craniosacral division (preganglionic axons leave the spinal cord at the cranial and sacral division of spinal cord)
Most active during resting conditions
ANS - Sympathetic Division
Dorsal and ventral horns???
But between T1 and L5 there is an addition of a lateral horn which is Grey Matter/cell bodies
Grey matter vs White matter???
Pre-ganglionic = short axons
Post-ganglionic nerve = long axons
Most in a row close to spinal cord = sympathetic ganglionic chain
ANS - Parasympathetic System
Live in the cranial and sacral section
Pre-ganglionic = long axons
Post-ganglionic nerve = short axons
ANS: ENS… the third system
The autonomic nervous system consists of a third division:
Enteric nervous system (ENS)
Neurons located in the walls of the digestive tract
Many visceral reflexes are initiated by the ENS, but receive input from the ANS
The Sympathetic Division
Sympathetic division consists of:
Preganglionic neurons between T1 and L2
Neuronal cell bodies in ganglia (ganglionic neurons) near the vertebral column
Sympathetic chain ganglia
Collateral ganglia
Specialized neurons in the interior of the adrenal gland
The Sympathetic Division Specifics
Sympathetic Chain Ganglia
Also called paravertebral ganglia or lateral ganglia
Located on both sides of the vertebral column
Postganglionic efferents control effectors in the body wall, head, neck, limbs, and thoracic cavity
Collateral Ganglia
Also called prevertebral ganglia
Neurons innervate effectors in the abdominopelvic cavity
Adrenal Medulla
Modified sympathetic ganglion—releases neurotransmitters into bloodstream
The Sympathetic Chain Ganglia
Preganglionic neurons
short and myelinated
only exit CNS via ventral roots of T1 to L2
Travel to ganglion via spinal nerve and white ramus communicans
Synapse with postganglionic neurons in chain ganglia
Postganglionic neurons
Long and unmyelinated
Exit chain ganglia via gray ramus communicans
Innervate glands and smooth muscle in the body wall and blood vessels, and viscera in the head and thorax.
Ventral Ramus???
Posterior Ramus???
Two rami communicans???
YOUTUBE this!!!!
Ganglionic Chain can go up or down…
Distribution of Sympathetic Post Ganglionic Fibers
A Summary of the Sympathetic Division
Consists of parallel chains on either side of the spinal cord
Preganglionic fibers are short, myelinated, and extend from the spinal cord to the sympathetic chain
Postganglionic fibers are long, unmyelinated, and extend to the effector organs
The Parasympathetic Division
Preganglionic neurons are in the brainstem and sacral segments (craniosacral)
Preganglionic neurons do not diverge as much as the sympathetic division
Therefore, the parasympathetic division is more localized and specific as compared to the sympathetic division
Synapses with postganglionic neurons occur either near the target organ (terminal) or within the target organ (intramural)
