AP - Nervous System Divisions

Peripheral Nervous System

consists of nerves that connect CNS to other body parts

Number of Cranial Nerves

12 pairs

Number of Spinal Nerves

31 pairs

Somatic NS

cranial and spinal nerves that connect CNS to the skin and skeletal muscles (conscious activites)

Autonomic NS

cranial and spinal nerves that connect CNA to viscera (subconscious activities)

Sensory Nerves

conduct impulses into brain or spinal cord

Motor nerves

conduct impulses from brain or spinal cord to effectors

Mixed Nerves

contain both sensory and motor nerve fibers - type most nerves are

Cranial Nerves

12 pairs numbered I-XII

underside of the brain, most attached to the brainstem

CN 1

Olfactory

Sense of Smell

CN II

Optic

Vision

CN III

Oculomotor

muscles that raise the eyelid, superior, medial, and inferior rectus and inferior oblique

CN IV

Trochlear

lateral rectus

CN V

Trigeminal

All of the sensation to the face, innervates muscles of mastication

CN VI

Abducens

Superior oblique

CN VII

Facial

muscles of facial expression

anterior 2/3 of tongue

autonomic control of tear glands, submandibular and sublingual salivary glands

CN VIII

Vestibulocochlear

Hearing and Balance

CN IX

Glossopharyngeal

Taste to posterior 1/3 of tongue

innervation of pharynx and tonsils

Autonomics to the parotid gland

CN X

Vagus

Muscles of larynx and pharynx

Swallowing and speech

autonomics to the organs of thorax and abdomen

CN XI

Spinal Accessory

innervates sternocleidomastoid and trapezius muscles

CN XII

Hypoglossal

movements of the tongue

number of cervical nerves

8 pairs

number of thoracic nerves

12 pairs

number of lumbar nerves

5 pairs

number of sacral nerves

5 pairs

number of coccygeal nerve

1 pair

cauda equina

formed by descending roots of lumbar, sacral, and coccygeal nerves

peripheral nerves

can be formed from one spinal nerve or they can be formed from a combination of spinal nerves

nerve plexus

when spinal nerves form a complex network

Largest and most complex part of the NS

the Brain

Brain controls

sensation, perception, movement, and thinking

what connects that brain and spinal cord

brainstem

meninges

membranes that protect brain and spinal cord. Made of 3 layers

Dura Mater

Superficial layer

Tough, dense connective tissue

supports and protects the brain

contains many blood vessels and nerves

Arachnoid Mater

Middle layer

weblike, no blood vessels

Subarachnoid space

space deep to the arachnoid mater

location of CSF

completely surrounds the brain and spinal cord

Pia mater

Deepest layer

attached to surface of brain/spinal cord

full of blood vessels that nourish the brain and spinal cord

Ventricles

4 interconnected spaces within the cerebral hemispheres and brainstem

Lateral Ventricles

two, c-shaped, located withing the cerebral hemispheres

Interventricular foramen

openings the allow for communication between the lateral ventricles and the third ventricle

Third ventricle

located between the cerebral hemispheres

Cerebral aqueduct

a narrow canal that connects the third ventricle to the fourth ventricle. It passes through the brainstem

fourth ventricle

located within the brainstem, just anterior to the cerebellum

Cerebrospinal Fluid

secreted by the choroid plexuses

location of the choroid plexuses

in each of the 4 ventricles

CSF Flow through Ventricles

lateral ventricles → through the interventricular foramen → to the third ventricle → through the cerebral aqueduct → to the fourth ventricle → subarachnoid space → reabsorbed through arachnoid granulations → recycled into blood

Hydrocephalus

accumulation of CSF in ventricles

“Water on the brain”

4 parts of the brain

cerebrum, diencephalon, brainstem, cerebellum

Cerebrum

superior, large part of the brain

higher mental functions: interprets sensory info, initiate voluntary movements, storing info as memories, retrieving stored info, reasoning, seat of intelligence and personality

Diencephalon

between cerebral hemispheres and above the brainstem, surrounds third ventricle

Brainstem

connects the brain to spinal cord

Cerebellum

inferior to occipital lobes, posterior to the brainstem

Proprioception, coordinates voluntary muscle movements, maintain posture

Structures of the Cerebrum

Corpus callosum, cerebral cortex, white matter

Corpus callosum

bundle of axons that connects the two cerebral hemispheres which allows communication between hemispheres

Cerebral cortex

thin layer of gray matter

Outermost layer of the cerebrum

75% of neuron cell bodies in the NS

White matter

lies under the cerebral cortex

Most of cerebrum

bundles of myelinated axons that connect to cell bodies in cerebral cortex to other portions

lobes of the cerebrum

frontal, parietal (2), occipital, temporal (2), insula (2)

frontal lobe

concentrating, planning, complex problem solving, judging the consequences of behavior. Movements of voluntary skeletal muscles

parietal lobes

paired. Sensations of temperature, touch, pressure, and pain involving the skin. Understanding speech and using words to express thoughts and feelings

occipital lobe

most posterior

processing vision and combining visual images with sensory experiences

temporal lobes

paired

hearing, interprets sensory experiences and remembers visual scenes, music, and other complex sensory patterns

Insula

paired, deep to temporal

associated with processing taste info, translating sensory info into appropriate emotional responses

Structures of the Diencephalon

thalamus, hypothalamus, optic chiasm, pituitary gland

Thalamus

selective gateway for sensory impulses ascending from other parts of the NS to the cerebral cortex. relays descending fibers from the cerebral cortex to other parts of the NS

Serves as a pit stop for many sensory and motor impulses

Hypothalamus

maintains homeostasis - body temp, water and electrolyte balance, hunger, body weight, links nervous and endocrine systems

Optic Chiasm

where some of the optic nerve fibers cross over

pituitary gland

sits in hypophyseal fossa. called master gland. secretes hormones that regulate other glands

structures of the brainstem

midbrain, pons, medulla oblongata

Midbrain

bundle of nerve fibers that join lower parts of the brainstem and spinal cord with superior parts of the brain

contains cerebral aqueduct

pons

appears as a rounded bulge

relays impulses between medulla oblongata and cerebrum and the cerebrum to cerebellum

works with medulla oblongata to control breathing

medulla oblongata

contains cardiac center, respiratory cent, and centers for nonvital reflexes

structures of the cerebellum

cerebellar cortex, arbor vitae, cerebellar peduncles

Cerebellar cortex

consists of two cerebellar hemispheres

Arbor vitae

tree of life in latin

treelike pattern of white matter deep to the gray matter

cerebellar peduncles

allows the cerebellum to communicate with the brainstem

Spinal Cord

slender column of nervous tissue continuous with brain and brainstem

extends downward through vertebral canal

begins at foramen magnum and terminates at the L1-L2 intervertebral space

31 segments

Cervical enlargement

a thickening of the spinal cord with nerve fibers that supply the upper limbs

Lumbar enlargement

a thickening of the spinal cord with nerve fibers that supply the lower limbs

conus medullaris

the tapering of the spinal cord just inferior the lumbar enlargement. At about the L1/L2 vertebral level

Filum terminale

a thin cord of pia mater that extends from the conus medullaris to the coccyx. It is responsible for anchoring the spinal cord inferiorly

Cauda equina

axons of motor and sensory neurons that extend downward within the vertebral canal to become the lumbar and sacral spinal nerves