Intro to Anatomy Final Chp 14 and 15 Nervous System

React to continuous changes in its internal and external environments, controls and integrates the various activities of the body, such as circulation and respiration

What are the functions of the nervous system?

Central Nervous System (CNS) and Peripheral Nervous System (PNS)

Nervous system is divided structurally into:

Brain and Spinal Cord

What does the Central Nervous system (CNS) Consist of?

The remainder of the nervous system outside of the CNS

What does the peripheral nervous system (PNS)?

Somatic nervous system (SNS) and Auto Nervous system (ANS)

Nervous System is divided functionally:

Neurons (Nerve Cells) and Neuroglia (Glial Cells), which support the neurons

Nervous tissue consists of two main cell types:

Neurons

The structural and functional units of the nervous system specialized for rapid communication?

Dendrites and Axons

A neuron is composed of a cell body with 2 processes (extensions):

Carry impulses to cell body

What do dendrites do?

Carry impulses away from cell body. Found around some axons, layers of lipid and protein material called myelin sheath, greatly increasing the velocity of impulse conduction

What do Axons do?

Have two or more dendrites and single axon that may have one or more collateral branches. The most common type of neuron in the nervous system (CNS and PNS). All motor neurons controlling skeletal muscle and comprising the efferent parts of ANS are multipolar neurons .

What are Multipolar neurons?

Specialised sensory neurons for the transmission of special senses. Have ONE dendrite and ONE axon. Comprise the sensory neurons of retina, olfactory epithelium, and inner ear which serve the senses of sight, smell and balance respectively

What are bipolar neurons?

Have a short, apparently single (but actually double) process extending from the cell body.

What are Pseudounipolar neurons?

A peripheral process and a central process

What are the processes included with the Pseudounipolar neurons?

Peripheral Process

Carry signals from receptor organs (touch, pain, or temperature senors in the skin, for example) toward the cell body.

Central Process

That continues from the cell body into the CNS

Sensory ganglia outside the CNS and are thus part of the CNS

Where are the cell bodies of the pseudounipolar neurons located?

Synapse

Site at which where neurons communicate?

Neurons communicate with each other by means of neurotransmitters which may excite or inhibit another neuron

What happens at synapses?

conducts signal toward synapse

At the presynaptic neuron….

Transmits electrical activity away from a synapse

At the the postsynaptic neuron….

on presynaptic side containing neurotransmitters

Where are the synaptic vesicles located?

Synaptic cleft

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

Neuroglia (Glial cells or Glia)

Are non-neuronal, non-excitable cells that form a major component of nervous tissue, supporting, insulating, and nourishing the neurons. they out number neurons in the CNS by about 10 to 1, and they make up about half the mass of the brain

glial cells can divide throughout life

Unlike neurons…..

Astrocytes, Oligodendrocytes, Ependymal cells, Microglia

What are the different types of neuroglia in the CNS?

Schwann cells, Satellite cells

What are the different types of neuroglia in the PNS?

Astrocytes

Maintain the environment of the nerve cells

Oligodendrocytes

Form a myelin sheath in the CNS

Ependymal Cells

Line the cavity of the brain

Microglia

Are macrophages in the CNS

Schwann cells

Form the myelin sheath in the PNS

Satellite Cells

Surround neuron cell bodies within ganglia

To integrate and coordinate incoming and outgoing neural signals, carry out higher mental functions, such as thinking and learning

What are the principal roles of the CNS?

The three membranes that envelop and protect the brain and the spinal cord.

What are the meninges?

The Pia Mater

(The delicate mother) The innermost,delicate and transparent meningeal layer which intimately covers the outer surface of the brain and spinal cord

Subarachnoid space

Where is the Cerebrospinal Fluid (CSF) located?

The arachnoid mater

(The spidery mother) the middle layer of the meninges, comes into direct contact with the dura mater above and is separated from the pia mater below by a cerebrospinal fluid (CSF) filled space known as the subarachnoid space.

CSF Cerebrospinal Fluid

Serves as a shock absorber for the central nervous system and circulates nutrients and chemicals filtered from the blood and removes waste products from the brain

The dura mater

(the tough mother) The thick outermost layer of meninges, intimately related to the internal aspect of the bone of the surrounding neurocranium (braincase)

Fat filled epidural space

How is the dura mater separated from the surrounding bone of the vertebral column?

Gray commissure, Dorsal horn, Ventral horn, Lateral horn

what makes up the gray matter?

Dorsal funiculus, Ventral funiculus, Lateral funiculus

What makes up the white columns?

The gray matter

Where do the nerve cell bodies lie?

Distributed at the surface of the cerebral hemispheres (cerebral cortex) and of the cerebellum (cerebellar cortex), as well as in the depths of the cerebrum the cerebellum and the brainstem in the form of nuclei

The brain grey matter is….

Nucleus

Is a collection of nerve cell bodies in the CNS

appears roughly as an H shaped area surrounded by white matter.

Spinal cord grey matter….

Posterior (dorsal) horn, Lateral (intermediolateral) horn, anterior (ventral) horn

What are the horns included in the gray matter of the spinal cord?

A tract

A bundle of nerve fibers (axons) within the CNS connecting neighboring or distant nuclei of the cerebral cortex

The white matter

The interconnecting fiber tract system form…

composed of axons that all have similar destinations and functions

The three funiculi contain many fiber tracts. each fiber tract is……..

Spinal Cord

The part of CNS from which spinal nerves arise. it provides a two-way conduction pathway from the brain to the body and vice versa. it is also a major center for reflexes

45 cm long, 14 mm wide

The spinal cord is about…..

vertebral canal extending from the foramen magnum at the base of the skull’s occipital bone superiorly to the level of the vertebra L1 or L2

The spinal cord runs through the….

Posterior median sulcus, Anterior median fissure

What are the two grooves that divide the spinal cord into symmetrical right and left sides?

on posterior side

Where is the posterior median sulcus located?

Deeper groove on anterior side

Where is the anterior median fissure located?

In sensory and motor nerves of limbs

where are enlargements of the spinal cord seen?

nerves of shoulders and upper limbs

Where are cervical enlargements?

nerves of pelvis and lower limbs

Where are lumbar enlargements?

Conus Medullaris

Thin, concial spinal cord below lumbar enlargement.

Filum Terminale

Thin thread of fibrous tissue at end of conus medullaris, attaches to coccygeal ligament

Cauda Equine

Nerve roots extending below conus medullaris

Spinal Cord segment

is the region of the spinal cord from whihc the nerve fibers that form a given spinal nerve emerge, designated by the spinal nerve that issues from it.

The Brain

Contains almost 97% of the body’s neural tissue. Average weight about 1.4 kg (3 Ib), Performs the most complex neural functions: consciousness, intelligence, memory, sensory-motor integration. Involved in innervation of the head.

Cerebrum, Cerebellum, Diencephalon, Brain stem

What are the regions of the brain?

Midbrain, pons, and medulla oblongata

What is included in the brain stem?

Peripheral Nervous System (PNS)

Consists of nerve fibers and cell bodies (in ganglia) outside the CNS that conduct impulses to or away from the CNS

Nerves

Is a bundle of nerve fibers (axons) wrapped in multiple layers of connective tissue. Emerge from The central nervous system through foramina of the skull and vertebral column. Carry signals to and from other organs of the body

Ganglion (plural, ganglia)

Is a knotlike swelling in a nerve where the cell bodies of peripheral neurons are concentrated. There are both motor (autonomic) and sensory ganglia?

Neurilemma

In the PNS nerve fibers (axons) are surrounded with a…..

Cell membranes of Schwann cells that immediately surround the axon, separating it from other axons

What does Neurilemma consist of?

Myelinated nerve fibers, Unmyelinated nerve fibers

What are the two forms of neurilemma?

Consists of schwann cells specific to an individual axon, organized into a continuous series of the enwrapping cells that form myelin

What are myelinated nerve fibers?

Composed of schwann cells engulfing multiple axons separately within their cytoplasm. these schwann cells do not produce myelin.

What are unmyelinated nerve fibers?

unmyelinated

Most fibers in cutaneous nerves (nerves supplying sensation to the skin) are….

Each nerve fiber (axon) with its neurilemma are wrapped with a delicate connective tissue layer called endoneurium.

A group of nerve fibers are bundled into a fasicle which is wrapped with a layer of dense connective tissue called perineurium

A bundle of fascicles is wrapped with a thick connective tissue sheath called epineurium forming the outermost coveringof the nerve, it includes fatty issue, blood vessels (Vasanervorum) and lymphatics

How are the peripheral nerves organized?

Endoneurium

Each nerve fiber (axon) with its neurilemma are wrapped with a delicate connective tissue layer called….

Perineurium

A group of nerve fibers are bundled into a fascicle which is wrapped with a layer of dense connective tissue called…

Epineurium

A bundle of fascicles is wrapped with a thick connective tissue sheath called _______________ forming the outermost covering of the nerve, it includes fatty tissue, blood vessels and lymphatics

Barrier against injury and penetration of the nerve fibers by foreign substances

The connective tissue wrapping around these axons provide an effective…

Spinal and Cranial

What are the types of nerves?

Spinal (segmental) nerves

Exit the vertebral column (spine) through the Intervertebral foramina. Arise in bilateral pairs from a specific segment of the spinal cord

8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal. identified by a letter and number designating the region of the spinal cord from which they arise

What are the 31 pairs of nerves?

rootlets

Spinal nerves intially arise from the spinal cord as ____________

Anterior (Ventral) nerve root and Posterior (dorsal) nerve root

Rootlets converge to form two nerve roots called?

Anterior (Ventral) nerve root

Consist of motor (effernet) fibers passing from nerve cell bodies in the anterior horn of spinal cord gray matter to effector organs located peripherally

Posterior (dorsal) nerve root

Consist of sensory (afferent) fibers from cell bodies in the spinal sensory or posterior (dorsal) root ganglion (DRG) that extend peripherally to sensory endings and centrally to the posterior horn of spinal cord gray matter

mixed spinal nerve (consisting both motor and sensory)

the posterior and anterior nerve roots unite, within or just proximal to the intervertebral foramen, to form……

Posterior (primary) rami of spinal nerves and Anterior (primary) rami of spinal nerves

what are the types of primary rami?

Posterior (primary) rami of spinal nerves

Supply nerve fibers to the synovial joints of the vertebral column, deep muscles of the back, and the overlying skin in a segmental pattern

Anterior (primary) rami of spinal nerves

Supply nerve fibers to the much larger remaining area, consisting of the anterior and lateral regions of the trunk and the upper and lower limbs

White and Gray Ramus

What are the secondary ramis?

White Ramus

The first branch from the spinal nerve, present at the levels of the spinal cord T1-L2 only, Carries visceral motor fibers to a nearby sympathetic ganglion. Also carries some visceral afferent fibers

Gray Ramus

Present at every level of the spinal cord, return from the sympathetic ganglion to rejoin spinal nerve

Because preganlionic axons are myelinated, this branch has a light color

Why are white ramus called the white ramus?

Postganglionic fibers that innervate glands and smooth muscles in teh body wall or limbs. these fibers are unmyelinated and have a dark gray color

Why are the gray ramus called the gray ramus?

Convey pain and proprioceptive information

What do the sensory fibers in motor nerves do?

Serve sweat glands and the smooth muscle of blood vessels and hair follicles

What do the motor fibers in sensory nerves do?

Dermatome

The unilateral area of the skin innervated by the sensory fibers of a single spinal nerve