BSF Chapter 9: NS Spinal Cord + Nerves

Central Nervous System (CNS)

brain and spinal cord

primary command center of body

Peripheral Nervous System (PNS)

12 Cranial Nerves that carry messages to and from the brain

31 Spinal nerves (mixed) that carry messages to spinal cord to parts of body

Somatic NS

Voluntary; skeletal muscle

Autonomic NS (ANS)

sympathetic + parasympathetic NS; involuntary (smooth + cardiac muscles, glands)

Neurons

functional cells of NS, highly specialized

Cell body

main portion contains nucleus + other organelles

Cell fibers

what distinguish the cells (nerves)

Dendrites

multiple branches carry impulses to cell body, neurons receive stimuli via dendrites

postsynaptic cell, binds neurotransmitters via protein receptors

Axons

single fiber carry impulses AWAY from cell body

presynaptic cells, releases neurotransmitter

Sensory Messages

carries TOWARDS CNS (AFFERENT)

conduct impulses to spinal cord + brain

(“S”ent Central)

Motor Messages

carries AWAY from CNS (EFFERENT)

impulses from CNS to muscle + glands

(“Moved Away”)

Neurilemma

outermost nucleated cytoplasmic layer of Schwann cells that surround axons + neurons

covering in PNS + helps peripheral nerves regenerate

Myelin Sheath

PNS has MYSH (neurilemma)

CNS DOES NOT! Once damaged, there is no fixing it

Myelinated axons

white matter

Unmylienated axons

gray matter

PNS CNS relations

PNS relays messages to CNS

Interneurons (central or associated neurons)

relay info from place to place w/in CNS

what are the 3 layers of a nerve (Superior/Top to Inferior/Bottom)

Epineurium (around entire nerve)

Perineurium (around fascicle)

Endoneurium (around nerve fiber

Nerve

fiber bundles in PNS

Tract

fiber bundles in CNS (train tract)

Neuroglia (glial cells)

protects, supports, + nourish nervous tiss

aid in cell repair, remove pathogens + impurities

continues to multiply throughout life

DO NOT CONDUCT IMPULSES

Examples of Neuroglia

Schwann cells, Oligodendroytes, Astrocytes, Ependymal cells

Synapse

tiny gap or junction b/w 2 nerves cells where messages pass from one cells to another

NS works by means of electric impulses sent along fibers + transmitted, specialized junctions

Plasma membrane

polarized (has negative charge)

Resting State

a stable electrical charge across cell mem when it is not actively sending signals

how are ions transported?

ATP

Action Potential

a rapid temporary shift/electrical charge at the membrane

Depolarization (AP)

Na+ flows into cell changing the electrical charge inside the mem (before)

Repolarization

ATP is used to return Na+ + K+ back to original resting state (Na+ more concentrated on inside)

role of myelin

enables impulse to jump from node to node thus speeding up impulse

Synaptic cleft

tiny gap

Neurotransmitters

chemicals released from nerve fibers to allow impulses over synaptic junction

Epinephrine (adrenaline), Norepinephrine (noradrenaline), Serotonin, Dopamine, Acetylcholine

Review for Synapse

Dendrites bring info to cell body

Axons take info away from cell body

info from 1 neuron flows to another across SYNAPSE (small gap separating neurons) which consists of:

Postsynaptic ending that contains receptor sites for neurotrans

synaptic celft or space between post and pre synaptic endings

Structure of Spinal Cord

links PNS + brain

SC extends from medulla to below the thoracic vertebrae b/w 1st + 2nd lumbar vertebrae

h-shapped section of gray matter is located internally + white matter is located around it

Inner Gray Matter

unmyelinated axons

dorsal end extends up and down on both sides

central canal in center of gray horn contains CSF (cerebral spinal fluid)

Outer White Matter

Myelinated axons

divided into right + left portions of white matter

anterior median fissure deeper groove that separates the anterior white matter

tracts in wm of sc carry impulses to + from brain

asending (afferent pathways to brain) and desending tracts (efferent pathways away from brain towards PNS)

31 pairs

according to level of spinal cord from where it arises

all 31 are mixed (both sensory + motor)

each nerve is attached to spinal cord by which two roots?

Dorsal root w dorsal root ganglion (sensory) afferent fibers from sensory receptors throughout body

Ventral root/ ventral root ganglion (motor) efferent fibers carry mess to muscles + glands

Cervical plexus

supplies motor impulses to neck muscles + receive sensory impulses from neck + back of head

phrenic nerve activates diaphragm

Brachial plexus

sends branches to shoulder, arm, forearm, wrist + hand (radial nerve originates from here)

Lumbosacral plexus

supplies nerves to pelvis + legs (sciatic nerve originates here)

Dermatones

sensory neurons from skin (expect face + scalp that feed info via spinal nerves)

Reflex Arc

spinal cord relay center for coordinating neural pathways

Receptor

detects stimuli

sensory neuron

transmits nerve impulses to CNS

CNS interneuron

coordinates nerve impulses + organizes response

Effector

muscle or gland outside CNS recieves nerve impulses from CNS + carries out response

Simple reflex

involves a few neurons (rapid, uncomplicated, automatic)

sympathetic NS

fight or flight

preganglionic motor neurons originate in spinal cord w/ cell bodies in thoracic + lumbar areas (L1-L2)

postganglionic neurons are adrenergic (activated by norepinephrine/adrenaline)

parasympathetic NS

rest + digest

SLUDD (Salvation, Lacrimation, Urination, Digestion, + Defecation)

Preganglionic neurons sacral part of spinal cord

Postganglionic neurons are choliengeric (activated by acetlycholine)

Lumbar puncture (spinal tap)

CSF removed for testing

done between L3-L4 vertebrae

Drug administration

Anesthetic (epideral)

Pain medi

Multiple Sclerosis (MS)

degenerative of nerve fiber due to destruction of MYSH

amyotrophic lateral sclerosis (ALS)

disease that destroys motor neurons

poliomyelitis

viral disease of NS

tumors

often arise in support tiss in + around SC

Monoplegia

paralysis of one limb

Diplegia

paralysis of both upper or lower limbs

Paralegia

paralysis of both lower limbs

Hemiplegia

paralysis of one side

tetraplegia

paralysis of all 4 limbs

Neuorpathy

any disease of nerves

Mononeuropathy

affect a sinlg enerve

polyneuropathy

impacts more than 1 nerve