A&P 1 - Neuro- OCCC 26-27

Neuro

Purpose of Nervous System

aid body in maintaining homeostasis in a coordinated fashion

3 basic steps: receive info, CNS process and decides action, issues commands to carry out response

Central Nervous System

brain stem and spinal cord

processes information, initiate movement, and performs decision making functions

Peripheral Nervous System

nerves and ganglia that extend all over the body for sensory and motor function

Sensory/Afferent

carries signals from receptors to the CNS; Afferent=Arrive at CNS

Motor/Efferent

carries signal from CNS to glands, muscles, and other nerve cells; Efferent=exit the CNS

Somatic Sensory

arrives at CNS with info about skin, muscles, bones, joints

information about our bodies and position in the world

Visceral Sensory

arrives at CNS with information about organs

Somatic Motor

exits CNS with signals for skeletal muscles

Visceral Motor

exits CNS with signals to glands, cardiac muscle, and smooth muscle

Autonomic Nervous System

Sympathetic, Parasympathetic, and Enteric Plexus

Sympathetic Nervous System

excites body for immediate action and inhibits digestion

fight or flight response

Parasympathetic nervous system

inhibits fight or flight response and excites digestion

rest and digest response

Enteric plexus

lies in walls of digestive tract and has more neurons than the spinal cord

communicate and coordinate motility and secretion

Classes of neurons

afferent, efferent, interneuron

Interneuron

receives information from other neurons and passes it along

integrating control center

Soma

cell body containing nucleus, cytoskeleton, and extensive rough ER

Dendrites

receives signals from neurons and neurotransmitters; 1-1000s

Axon

only 1 per nerve

sends signals via rapid conduction of nerve signals to remote areas

Axon hillock

swelling of cell body that gives rise to axon

Axolemma

cell membrane of axon

Axon terminal

distal end of nerve that synapses with next cell via neurotransmitters

Receptor

cell that receives info from neurotransmitters via proteins on cell membrane

has ion channels and can cause second messengers to activate

Myeline sheath

spiral layers of insulation around the axon to increase speed of action potential

Schwann cell

PNS; myelin sheath with up to 100 spiralized layers

Neurolemma

thickest outermost layer of the myelin sheath

Nodes of Ranvier

gap between myelin sheath where action potentials propagate

Neuroglia

all cells of nervous tissue except neurons that have a supportive and protective function

6 types: Central, Peripheral, Oligodendrocytes, Ependymal, Microglia, Astrocytes,

Peripheral glia cells

only in PNS: satellite and schwann

Oligodendrocytes

has central nucleus and multiple “arms” that reach out to form many myelin sheaths

Ependymal cells

line internal cavities of brain and spinal cord, produce and circulate CSF

Microglia

small macrophages that remove cellular debris and foreign matter, aid in changing connections between neurons

Astrocytes

most abundant, form blood brain barrier (perivascular feet wrap capillaries), monitor neuron activity, secrete nerve growth factor, promotes synapse formation, regulate composition of tissue fluid, replace damaged neurons with hardened scar tissue

Satellite cells

similar to astrocytes but in PNS; surround nerve cell bodies to insulate and regulate chemical environment of neurons

Schwann cells

envelope axons to create myelin sheath in PNS

participate in regeneration of damaged axons

Resting membrane potential

Typically -70 mV

Maintained through diffusion of ions, selectively, permeable, membrane, and electrical attraction of cation and anions each other

Local potential

Graded

decremental

reversible

excitatory or inhibitory

Action potential

All or none in law

Non-decremental

Irreversible

Self propagating

Absolute refractory period

No new stimulus can trigger new action

Relative refractory period

Very strong stimulus can create new response during hyperpolarization

Synapse

Junction at the end of an axon where it stimulates another cell

Presynaptic neuron

Sends signal

Postsynaptic neuron

Receives signal

synaptic cleft

Gaps between neurons where electrical and chemical synapsis occur

Synaptic vesicle

organelle in an axon terminal containing neurotransmitters

Acetylcholine

Form from acetic acid and choline To activate, skeletal muscle used in autonomic, nervous system, ganglia, parasympathetic, and nicotine receptors

Monoamine

Serotonin

Epinephrine norepinephrine glutamate

Amino acids

GABA, Glycine, Glutamate

EPSP

causes more likely to fire by Sodium influx

IPSP

Inhibitory

Summation

All action potential cumulatively

Temporal summation

Time sensitive; one neuron can fire over and over quickly and cause an action

Spatial summation

many Neurons Fire and cause an action

Types of synopsis

Divergent, convergent, recurrent/reverberating

Anesthetic

Induces insensitivity to pain; general crosses brain barrier to block nervous tissue transmission; local does not cross blood brain barrier blocks voltage, gated Na+ channels

central canal

usually closed, central opening of the spinal cord

grey matter

site of synaptic contact between neurons

containing neurons, dendrites, and interneurons but not much myelin

white matter

composed of axon bundles that course up and down the spinal cord; white due to myelin sheaths

ventral (anterior) root

efferent fibers connecting to muscle

motor fibers

dorsal (posterior) root

afferent fibers carrying sensory information up spinal cord

posterior horn

sensory afferent neurons synapse location

anterior horn

motor efferent neurons synapse location

dorsal (posterior) root ganglion

cell bodies of sensory neurons entering spinal cord

ganglion

collection of cell bodies outside of the CNS

reflex

quick involuntary reaction to stimulus

Basic components of reflex arc

1) patellar ligament is stretched

2) stretch signals travel to spinal cord via primary afferent with cell body

3) stimulates alpha motor neurons in inhibit hamstring never and excite interneuron in quad

4) alpha motor neuron sends message to the quads to resist stretching by contracting - hamstring is inhibited

somatic reflexes

utilize skeletal musclescer

cerebrum

forebrain

area of higher thinking/processing

longitudinal fissure

divides left and right along saggital plane

central sulcus

separates frontal and parietal lobes

front associated with motor

rear associated with sensory

gyros

wrinkles or thick folds upward

sulcus

shallow grooves that separate gyri

corpus callosum

connects and communicates between left and right hemispheres

cerebellum

largest part of hindbrain

associated with movement, memory, balance

brainstem

midbrain, pons, and medulla

extends down from foramen magnum

associated with breathing, heart rate control, wakefulness, and carries afferent/efferent nerves between cerebrum and spinal cord

cerebral cortex

contains most of the grey matter of the cerebrum

ventricles

internal chambers filled with cerebrospinal fluid

choroid plexus

collection of blood capillaries that filter blood serum

meniges

3 protective layers between bone and nervous tissue

Deep to superficial: pia mater, arachnoid mater, dura mater

pia mater

thin delicate layer of meniges that covers brain over gyri and in sulci

arachnoid mater

weblike meniges that covers gyri and has CSF in subarachnoid space

dura mater

thickest and most durable layer of meniges that limits brain movement via falx and tentorium cerebral folds

has sinus to drain blood

2 layers: periosteum (fibrous) and menigeal

cerebrospinal fluid

clear colorless fluid that bathes external surfaces of the central nervous system

contains more sodium and chloride, less potassium, calcium, and very little protein

function: buoyancy, protection, and chemical stability

hindbrain

embryologically the oldest portion of the brain

medulla

lowest portion of the brainstem containing cranial nerve nucleis

functions: respiration and vasomotor control

CN: IX X XI XII

pons

between midbrain and medulla

function: controls eye movement, expression, taste, and posture

CN: V VI VII VIII

midbrain

highest part of the brainstem

function: vision, gaze control, and fine motor control

CN: III IV

cerebellum

develops with pons

largest portion of the hindbrain containing ½ of brains neurons

function: balance, coordination, fine motor, time management, and impulse control

diencephalon

lowest portion of the cerebrum

contains: thalamus, infundibulum, mammillary body

thalmus

central processing unit containing 23 nuclei grouped together

function: thought, emotion, sensation, and movement

hypothalmus

control center for endocrine and autonomic function (major role in homeostasis)

function: hormone secretion, thermoregulation, hunger/thirst, circadian rhythms, memory, and emotion

optic chiasm

“X” shaped crossing of optic nerves over each other and pituitary gland

pituitary gland

attached to the hypothalamus

function: hormone control

anterior secretes hormones in response to hypothalamus

posterior secrete short acting hormones from nerve endings

frontal lobe

seat of conciousness, abstract thought, declarative memory, cognition, emotion processing, mood, motivation, speech, voluntary control

parietal lobe

sensory integration, somatic processing, spatial awareness, body orientation, language and numerical processing

occipital

visual cortex

temporal lobe

separated from frontal and parietal by lateral sulcus

hearing, smell, emotion, learning, language comprehension, grammar, memory consolidation, storage of auditory verbal and visual memories

cranial nerve nmemonic

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Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, spinal Accessory, Hypoglossal

cranical nerve class nmenomic

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Sensory, Sensory, Motor, Motor, Both, Motor, Both, Both, Both, Both, Motor, Motor

Stroke

What: sudden death of brain tissue from bleeding or loss of blood flow

Cause: hemorrhagic: weaking of arteries with age/trauma/anuerysm

ischemic: thrombus being dislodged or lipid deposit

Prognosis: nerves cannot regenerate but new pathways can be formed, not perfect

hydrocephalus (HCP)

What: accumulation of excessive amounts of cerebrospinal fluid

Cause: flow obstructed by lesion or bleeding, reabsorption obstructed

Prognosis: asymptomatic if treated with shunt, quickly lethal otherwise