Cns & Pns

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Two major parts of the mammalian nervous system

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Cns

Pns

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Consists of the brain and spinal cord

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Cns

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Consists of the cranial and spinal nerves

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Pns

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Layers of the meninges The outermost meningeal layer is the dura mater, a tough, strong, and thick layer of dense connective tissue fibers

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Pia

Arachnoid

Dura

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The outermost meningeal layer, a tough, strong, and thick layer of dense connective tissue fibers

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Dura mater

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Deep to the dura mater

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Arachnoid mater

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The innermost meningeal layer is the delicate connective tissue

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Pia mater

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This layer contains numerous blood vessels and adheres directly to the surfaces of the brain and spinal cord.

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Pia mater

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Between the arachnoid mater and the pia mater

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Subarachnoid space

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Circulating in the subarachnoid space that bathes and protects both the brain and spinal cord.

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Cerebrospinal fluid

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a clear, colorless fluid that cushions the brain and spinal cord, and gives them buoyancy as a means of protection from physical injuries. Wh

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Cerebrospinal fluid

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What produces the CSF

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Choroid plexus

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Where does CSF form

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Lateral

Third

Fourth ventricles

Cavities in the brain

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are small, vascular extensions of dilated and fenestrated capillaries that penetrate the interior of brain ventricles.

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Choroid plexus

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fills the central canal of the spinal cord.

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Csf

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important for homeostasis and brain metabolism. It brings nutrients to nourish brain cells

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Csf

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. After circulation, CSF is reabsorbed from the arachnoid space via the ______

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Arachnoid villi

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small, thin-walled arachnoid extensions that project into the venous sinuses located between the periosteal and meningeal layers of dura mater.

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Arachnoid villi

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The structural and functional cells of the nervous tissue

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Neurons

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Each neuron consists of three distinct structures

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Soma

Axon

Dendrites

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contains the nucleus, nucleolus, numerous different organelles, and the surrounding cytoplasm

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Soma

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Surrounding cytoplasm of a some

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Perikaryon

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Projecting from the cell body are numerous cytoplasmic extensions

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Dendrites

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Dendrites form what structure

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Dendritic tree

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Surrounding the neurons are the smaller and more numerous supportive cells collectively called _______

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Neuroglia

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These cells form the nonneural components of the CNS.

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Neuroglia

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Major types of neurons in the nervous system

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Unipolar

Bipolar

Multipolar

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These are the most common type in the CNS

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Multipolar

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Type of neuron that is found on all motor neurons and interneurons of the brain, cerebellum, and spinal cord

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Multipolar

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Projecting from the cell body of a multipolar neuron are numerous branched ________

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Dendrites

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How many axons are present in multipolar neuron

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One

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These are not as common and are purely sensory neurons

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Bipolar neurons

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a single dendrite and a single axon are associated with the cell body

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Bipolar neuron

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neurons are found in the retina of the eye, in the organs of hearing and equilibrium in the inner ear, and in the olfac- tory epithelium in the upper region of the nose

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Bipolar neuron

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Unipolar neurons are formerly called

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Pseudounipolar neurons

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Neuron that has a single process extending from its soma

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Unipolar neuron

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What function does unipolar neurons exhibit

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Sensory

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Location of unipolar neurons

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Sensroy ganglia of cranial and spinal nerves

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Highly specialized cells present in both the CNS and the PNS wrap around the axon numerous times to build up successive layers of modified cell membrane and form a lipid-rich, insulating sheath around the axon

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Myelin sheath

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Small gaps interspersed between myelinated axons

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Node of ranvier

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Axons in cns and pns can either be

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Myelinated

Unmyelinated

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In the PNS, all axons are surrounded by specialized cells that either myelinate the axons or envelope the unmyelinated axons

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Schwann cells

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myelinate individual peripheral axons and extend along their length, from their origin to their termination in the muscle or gland.

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Schwann cells

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do not show nodes of Ranvier because the Schwann cells form a continuous sheath.

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Unmyelinated xons

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Where can unmyelinated axons found

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Autonomic nervous system

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Schwann cells are exclusive where

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Pns

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What myelinates the axons in the cns

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Oligodendrocytes

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What kind of cell are oligodendrocytes

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Neurogial cells

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Difference of oligodenrocytes and schwann cells

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Oligodendrocytes; cns and envelops and myelinates multiple axons

Schwann cells; pns, covers a segment in a single axon

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The brain and the spinal cord may contain two types of matter

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White

Gray

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Supportive cells of the gray matter

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Neuroglia

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consists of neurons, their dendrites, and the supportive cells

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Gray matter

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This region represents the site of connections or synapses between a multitude of neurons and dendrites.

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Gray matter

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Four types of neuroglial cells

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Astrocytes

Oligodendrocytes

Microglia

Ependymal cells

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consists of neurons, their dendrites, and the supportive cells

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Gray matter

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What does the gray matter covers

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Brain

cerebrum

cerebellum

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What makes the the white matter white

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Myelin sheath in axons

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These cells do not become stimulated or conduct impulses, but are morphologically and functionally different from the neurons.

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Neuroglia

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The CNS contains approximately ____ more neuroglial cells than neurons.

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Tenfold

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Functionally, neurons are classified as

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Afferent, sensory

Efferent, motor

Interneurons

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The rate of conduction of the stimulus is dependent on what

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Size of axon and myelinition

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Axons that conduct impulses at a faster rate

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Myelinated axons

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are first synthesized in the cell body and transported in small tubules called microtubules to the region where the axon terminates or synapses with other dendrites, a cell body, or other axons.

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Neurotransmitters

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Termination of axon

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Synapse

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When are neurotransmitters released

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During a nerve stimulus

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What covers the surface of dendrites

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Dendritic spines

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specialized to receive and to integrate information from other dendrites, neurons, or axons.

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Surface membrane of the soma and dendrites

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conduct the received information away from the neuron to an interneuron, another neuron, or to an effector organ such as a muscle or gland.

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Axons

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What connects (synapse) with axon terminals from other neurons

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Dendritic spines

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largest and most abundant neuroglia cells in the gray matter

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Astrocytes

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conduct impulses from receptors in the internal organs or from the external environment to the CNS.

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Afferent, sensory

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Two types of astrocytes

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Fibrous astrocytes

Protoplasmic astocytes

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Abuts the surfce of capillaries and neurons

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Astrocytes

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which restricts the movement of molecules from the blood into the interstitium of the CNS

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Blood brain barrier

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_________of astrocytes cover the capillary basement membrane and form part of the blood-brain barrier,

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Perivascular feet

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The processes of astrocytes also extend to the basal lamina of the pia mater to form an impermeable barrier

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Glia limitans

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What structures does glia limitans surround

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Brain

Spinal cord

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control the chemical environ- ment around neurons by clearing intercellular spaces of increased potassium ions and released neurotransmitters, such as glutamate, at active synaptic sites to maintain a proper ionic environ- ment for their function.

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Astrocytes

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Astrocytes remove glutamate and convert it to ________

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Glutamine

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smaller than astrocytes with fewer cytoplasmic processes.

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Oligodendrocytes

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Smallest neuroglial cells

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Microglia

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convey impulses from the CNS to the effector muscles or glands in the periphery.

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Efferent, motor

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The dark-staining microglia are believed to be part of the ___________of the CNS that originates from precursor cells in the bone marrow.

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mononuclear phagocyte system

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main function is similar to that of the macrophages of the connective tissue.

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Microglia

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are simple cuboidal or low columnar epithelial cells that line the ventri- cles of the brain and the central canal in the spinal cord

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Ependymal cells

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The apices of ependymal cells has what structures

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Cillia

Microvilli

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facilitate the movement of the cerebrospinal fluid through the central canal of the spinal cord,

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Cilia

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Thoracic regions of the spinal cord contains what gray horns

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Anterior

Posterior

Lateral gray horns

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contain motor neurons of sympathetic division of autonomic nervous system

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Lateral gray horns

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contain motor neurons

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Anterior horns of gray matter

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Axons from _______ forms the anterior roots of spinal nerves

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Anterior horns

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contains closely packeda scending and descending axons

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White matter

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constitute the majority of the neurons in the CNS

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Interneurons

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Posterior columns of white matter contain

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Fasciculus gracilis

Fasciculus cuneatus

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connects two sides of the gray matter and

contains the central canal

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Gray commissure

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most superficial and covered by pia mater; contains neuroglial cells and horizontal cells of Cajal

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Molecular layer (1)

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contains neuroglial cells and

small pyramidal cells

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External granular layer (2)

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medium-sized pyramidal

cells predominant type

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External pyramidal layer (3)

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thin layer with small granule,

pyramidal cells, and neuroglia

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Internal granular layer (4)

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contains neuroglial cells and

largest pyramidal cells

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Internal pyramidal layer (5)

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deepest layer, adjacent to white matter

with various cell types

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Multiform layer (6)

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Deep folds in cortex

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Cerebellar folia

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• Deep folds in cortex called cerebellar folia separated by ______

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Sulci

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They serve as intermediaries or integrators of nerve impulses and connect neuronal circuits between sensory neurons, motor neurons

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Interneurons

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contains large Purkinje cells whose

dendrites branch in molecular layer

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Middle purkinje layer

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contains small granule cells, Golgi type II

cells, and empty spaces called glomeruli

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Granule cell layer

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Neurons are highly specialized for

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Irritability

Conductivity

And synthesis of neuroactive substances

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Neuroactive substances that neurons produce

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Neurotransmitters

Neurohormones

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Axons arise from the funnel-shaped region of the cell body called _______

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Axon hillock

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Where does the initial segment of axon located

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Between the axon hillock and where the myelination starts

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Segment of an axon where stimuli, whether inhibitory or stimulatory, are summated and the resulting nerve stimuli generated.

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Initial segment

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are small accumulations of neurons and supportive glial cells surrounded by a connective tissue capsule

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Ganglia

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provide structural support for the neuronal bodies, insulate them, and regulate the exchange of different metabolic substances between the neurons and the interstitial fluid.

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Satellite cells

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Location of peripheral ganglia

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Parallel to the vertebral column

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aggregations of neuron cell bodies that are located outside of the CNS.

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Dorsal root ganglia

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Where is the dorsal root ganglion stuated

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Dorsal nerve root

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Waht surrounds unipolar neurons

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Satellite cells

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partition the nerve into several nerve (axon) bundles

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Fascicles

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The outermost connective tissue layer is the strong sheath _________ that binds all fascicles together.

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Epineurium

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It consists of dense irregular connective tissue that completely surrounds the peripheral nerve

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Epineurium

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A thinner connective tissue layer called the ______ extends into the nerve and surrounds one or more individual nerve fascicles.

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Perineurium

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loose vascular connective tissue layer of thin reticular fibers that surrounds each myelinated axons with a schwann cell

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Endoneurium

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Supportive cell of the pns

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Schwann cell

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These nodes significantly accelerate the con- duction of nerve impulses (action potentials) along the axons.

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Nodes of ranvier

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Impulse propagation by which nerve impulse or action potential jumps from node to node, resulting in a more efficient and faster conduction of the impulse

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Saltatory conduction

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are small, flat cells that surround the neurons of PNS ganglia

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Satellite cells