Central Nervous System

spinal cord

spinal cord

• part of central nervous system and is the continuation of the medulla oblongata (lowest part of the brain).

• runs through the vertebral canal of the vertebral column.  Extends from the foramen magnum (skull) to the level of the L1 or L2 vertebrae. 

functions of spinal cord

• through spinal nerves that attached to it, the spinal cord is involved in sensory and motor innervation of the entire body inferior to the head.

• provides a two way conduction pathway for signals between the body and the brain.

• major center for reflexes.

conus medullaris

termination of the spinal cord (around L1 or L2)

cerebrospinal fluid (CSF) of the subarachnoid space

inferior to the spinal cord, the lumbar and sacral spinal nerve roots float in the _ before exiting through their appropriate intervertebral foramen in the lumbar and sacral regions

cauda equina

nerve roots; resemble a horse’s tail

cervical and lumbar enlargements

in cervical and lumbar regions of the spinal cord, where the nerves to the upper and lower limbs arise, the spinal cord shows obvious enlargements called the _

spinal tap/lumbar tap/puncture

area inferior to the spinal cord provides clinicians with an area of accessible CSF that can be withdrawn without damaging the spinal cord

white matter

• outer region composed of myelinated and unmyelinated axons

• allows communication between different parts of the spinal cord

• allows communication between cord and the brain

gray matter

• inner region consists of mixture of neuronal cell bodies

• in cross section, the _ matter of the spinal cord is shaped like the letter H.

• in _ matter is a narrow central cavity called the central canal

dorsal (posterior) horns

two posterior arms of the H that consist entirely of interneurons that receive information from sensory neurons

ventral (anterior) horns

two anterior arms of the H and contain cell bodies of motor neurons that send their axons out of the spinal cord

lateral horns

small lateral gray columns and contain cell bodies of motor neurons that send axons out of spinal cord (only located in the thoracic and superior segments of the spinal cord)

meninges

are three connective tissue membranes that lie just external to the brain and spinal cord

- functions are to cover and protect the CNS, enclose and protect blood vessels that supply the CNS and contain the cerebrospinal fluid.

• dura mater - most external

• arachnoid mater 

• pia mater - most internal

protection of spinal cord

• neural tissue of the spinal cord is protected by the vertebrae

• protection also occurs by surrounding membranes called meninges and by a watery cushion of cerebrospinal fluid

spinal dura mater

outermost layer and is also called the "tough mother" because it is the strongest layer of the meninges; it is composed of dense fibrous connective tissue and forms a tough protective covering around the spinal cord

epidural space

• Just external to the spinal dura

  filled with fat and a network of veins; anesthetics are often injected here to numb the spinal cord and thereby relieve pain in body regions inferior to the injection site

spinal arachnoid mater 

 lies just deep to the dura mater

subdural space

between the spinal arachnoid mater and then dura mater; is referred to a potential space because although normally thin, it has potential to fill with fluid or blood as a result of disease or trauma

subarachnoid space

deep to the arachnoid membrane and is spanned by weblike threads that hold the arachnoid mater to the underlying layer, the pia mater; filled with cerebrospinal fluid.

pia mater

the innermost layer and is also called the "soft mother" because it is the delicate layer; unlike the other meninges, it clings tightly to the surface of the spinal cord

denticulate ligaments

lateral extensions of pia mater that function to anchor the spinal cord laterally

film terminale

inferior extension of pia mater from the conus medullaris that anchors the spinal cord vertically

cerebrospinal fluid

a watery broth that fills the subarachnoid space and central hollow cavities in the brain and spinal cord that provides a liquid cushion that gives buoyancy to the CNS

brain

• stimulates movement

• maintains homeostasis  

• origin of conceptual thought

cerebrum

 the large brain

cerebellum

the little brain because it shows an organization similar to the cerebrum

• gray matter is located on the outside of the cerebellar cortex with the white matter underlying

brain stem

Regulates visceral activity of the body and houses the reticular activating system (RAS) which is involved in maintaining consciousness and sleep cycle

• is formed by midbrain, pons, and medulla oblongata

cerebral cortex

• occupies most of the cranium

• composed of two hemispheres separated by a longitudinal fissure

gray matter of cerebral cortex/cerebrum

 (mostly cell bodies and supporting tissue) near the surface of the cerebrum and is organized into gyri (folds) and sulci (grooves).

white matter of cerebral cortex/cerebrum

found underlying the cerebral cortex and appears white because of the myelination of the nerve fibers.

association fibers

transmit impulses between gyri in same hemisphere

commissural fibers

transmit impulses to gyri in the other hemisphere

corpus callosum

major group of commissural fibers between hemispheres; projection fibers transmit impulses from cerebrum to other brain and spinal cord regions

occipital lobes

primary visual area

Temporal lobes 

primary auditory area

Parietal lobes 

language and association

Postcentral gyri

(in parietal lobes) - general sensory area

Precentral gyri

(in frontal lobes) - general motor area

Frontal lobe

personality

cerebellar nuclei

embedded in cerebellum white matter

• located behind the pons and medulla and below the occipital lobes of cerebrum

subconscious skeletal movements

required for coordination, balance, and posture maintenance

midbrain

extends from base of diencephalon to the pons

cerebral peduncles 

contain motor fibers connecting the cerebral cortex to the pons and spinal cord as well as sensory fibers connecting the spinal cord to the thalamus.

colliculi

reflex centers for eye, head, and trunk movements in response to visual and auditory stimuli are located on the dorsal aspect of the midbrain.

pons

located above the medulla and in front of the cerebellum

• means bridge and it serves to send relay to nerve fibers to the cerebellum, as well as CNS structures superior and inferior to the pons. It also contains part of respiratory center for control of breathing.

medulla oblongata

is continuous with the spinal cord

• pyramids located on the ventral surface near the midline. They represent the decussation (crossing over) of the motor pathway that controls voluntary movement in the body

diencephalon

• located in center of the brain, lateral to the midline third ventricle.

• consists of several subdivisions; the thalamus and hypothalamus are most important.

thalamus

contains groups of nuclei above the midbrain that relay or interpret sensory impulses ascending from the spinal cord

hypothalamus

• ies between the thalamus and pituitary gland, controls and integrates the autonomic nervous system (ANS), connects CNS with endocrine system, controls body temperature, hunger, and thirst.

limbic system

• made up of nuclei and tracts that are located around the diencephalon and basal nuclei

• word limbic means border

• primary function is in emotions such as pain, pleasure, anger, rage, fear, sorrow, sexual feelings, docility, and affection.

• also involved in memory formation.