Nervous System

Central Nervous System (CNS) Organs

brain, spinal cord

Peripheral nervous system (PNS)

cranial nerves (12 pairs), spinal nerves (31 pairs), plexuses, peripheral nerves

Cranial and Spinal nerves

Afferent sensory nerves
Efferent motor nerves
Mixed nerves (carry sensory and motor fibers)

Autonomic Nervous System

carries impulses from the central nervous system to the organs
involuntary functions (sympathetic and parasympathetic)

Sympathetic nerves

stimulate body under stress (fight or flight)

Parasympathetic nerves

balance the sympathetic system (rest and digest)

2 types of neurvous cells

neurons and glia

Neurons

nerve cells that conduct impulses

Glia (neuroglia)

do not conduct impulses; support cells

Neuron structure

dendrite, cellbody (nucleus), axon

Dendrites

branches that conduct nerve impulses toward the cell body

Cell body

contains the nucleus, process nerve impulse

axon

conducts impulses away from cell body (meylin sheath, (schwan cells in PNS), Nodes of ranvier, neurilemma)

Ganglia

small clusters of nerve cell bodies

Terminal end fibers

secrete neurotransmitters

Synapse

space between one cells axon terminal and anothers dendrite, space where NTs pass

Sensory neurons

afferent, carry impulses to spinal cord and brain

Motor Neurons

efferent, carry impulses away from brain and spinal cord to muscles and glands

Interneurons

conduct impulses from sensory neurons to motor neurons or between other interneurons

Schwan cells

produce meylin for periferal neurons, outer membrane: neurilemma, not present in CNS

Neurilemma

outer membrane of schwann cells, essential for regeneration of cut and injured axons, schwann cells not present in CNS = less regeneration

types of glia

astrocytes, microglia, oligodendrocytes

Astrocytes

star-shaped cells that anchor small blood vessels to neurons

Microglia

small cells that move in inflamed brain tissue, do phagocytosis

Oligodendrocytes

form meylin sheath for CNS axons

Blood-Brain Barrier

two-layer structure formed when astrocyte branches attach to small blood vessels
seperates blood tissue and nervous tissue, protects brain

Nerve

bundle of peripheral axons

Tract

bundle of central axons, white matter and grey matter

White matter

tissue composed primarily of myelinated axons (nerves or tracts), transfers information

Grey matter

tissue composed primarily of cell bodies and unmyelinated fibers, possesses information

Nerve coverings

fibrous connective tissue
endoneurium, perineurium, epineurium

Endoneurium

surrounds individual fibers within a nerve

Perineurium

surrounds a group (fascicle) of nerve fibers

Epineurium

surrounds the entire nerve

Reflex arcs

nerve impulses conducted from RECEPTORS to EFFECTORS over neuron pathways

Two-Neuron Arc

simplest reflex arc, one sensory and one motor neuron

Three-Neuron Arc

second simplest reflex arc, involves sensory, interneurons and motor neurons

Ganglion

group of nerve cell bodies located in PNS, contains hundereds of cell bodies

Nerve impulses

self-propogating wave of electrical disturbance that travels along the surface of a neuron’s plasma membranes (aka action potential)

nerve impulses mechanism

• at rest neurons membrane + (polarized), slight excess of NA+

• stimulus triggers NA+ channels to open

• Inward movement of NA+ depolarizes membrane (inside more + than outside)

  • nerve impulse

• membrane repolarizes, next section of membrane already depolarizing, cascade of impulses down membrane

Saltatory conduction

action potential jumping gaps in myelin sheath, much faster than continuous conduction

Continuous conduction

conduction of action potentials in unmyelinated membranes, much slower than saltatory conduction

5 neurotransmitters

norepinephrin, serotonin, dopamine, GABA, acetylcholine

Cerebrum

largest section of the brain, cerebral cortex (surface nerve cells), manages speech, vision, smell, movement, hearing and thought

Cerebellum

coordinates voluntary movements
maintains balance, equilibrium, sustain posture

Thalamus

integrates and monitors impulses from skin (pain), relays sensory info, regulates level of conciousness, motor reflexes

Hypothalamus

controls body temp, sleep, appetite, sexual desire, and emotions
regulates release of hormones from pituitary gland
monitors sympathetic and parasympathetic nervous system

Brainstem

midbrain, pons, medulla

Midbrain

contains pathways connecting cerebrum with lower brain portions

Pons

bridges cerebrum and cerebellum with rest of brain, big role in respiration, houses nerves for face and eyes

Medulla Oblongata

connects spinal cord to brain, nerve tracts from side ot side
regulates: blood vessels, heart, respiratory system, vitals center

Spinal cord structure

columns of white matter, bundles of myelinated nerve fibers, tracts, interior composed of grey matter

Spinal Cord grey matter

mainly made of neuron dendrites and cell bodies

Spinal cord tracts

provide two-way conduction paths (ascending and descending)

Spinal cord functions

primary center for spinal cord reflexes, sensory tracts conduct impulses to brain, moter tracts conduct impulses from brain

Dermatome

skin surface area supplied by single spinal nerve
responsible for referred pain

CSF

carries oxygen and nutrients from blood to neurons/neuroglia and eliminate waste from them
in subarachnoid spaces of meninges, central canal inside cord, ventricles in brain

Autonomic Nervous System

motor neurons conduct impulses from the central nervous system to cardiac muscle, smooth muscle, glandular epithelial tissue
regulate body’s autonomic functions

Somatic nervous system

motor nerves that control the voluntary actions of skeletal muscles

Autonomic neurons

neurons that make up ANS

Preganglionic neurons

conduct impulses from spinal cord or brainstem to an autonomic ganglion

Postganglionic neurons

conduct from autonomic ganglia to cardiac muscle, smooth muscle, and glandular epithelial tissue

Autonomic/Visceral effectors

tissue to which autonomic neurons conduct impulses (cardiac and smooth muscle, smooth muscle, glandular epithelial tissue)

Sympathetic nervous system

emergency or stress system, controls visceral effectors under stress/strain, fight or flight response, increases HR, RR, BP, dilated pupils and bronchioles, decrease digestion and secretions

Adrenergic fibers

postganglionic axons release NOREPINEPHRINE
part of SNS

Parasympathetic Nervous System

balance the sympathetic system, rest and digest, decrease HR, RR, BP, constricts pupils and bronchioles, increases digestion and secretions

Cholinergic Fibers

preganglionic axons of parasympathetic and sympathetic systems, parasympathetic postganglionic axons release acetylcholine

Limbic System

responsible for our emotions, big role in formation of memories, emotions produce widespread changes in automatic functions

olfactory nerve

conducts impulses from nose to brain
sense of smell

optic nerve

conducts impulses from eye to brain
vision

oculomotor nerve

conduct impulses from brain to eye muscles
eye movement, pupil size, lense focusing

trochlear nerve

conducts impulses from brain to external eye muscles
eye movement

trigeminal nerve

conducts impulses from teeth, skin and mucous membrains of head to brain and from brain to chewing muscles
sensations of face, scalp, teeth; chewing movements

abducens nerve

conducts impulses from brain to external eye muscles
eye movement

facial nerve

conducts impulses from taste buds of tongue to brain and from brain to face muscles
sense of taste, contraction of face muscles (facial expressions)

vestibulocochlear nerve

conducts impulses from ear to brain
hearing, sense of balance

glossopharyngeal nerve

conducts impulses from throat and taste buds to brain and from brain to throat muscles and slivary glands
sensation of throat, taste, swallowing movements, secretion of saliva

vagus nerve

• conducts impulses from throat, larynx, and abdominal/thoracic organs to brain and vice versa

• sensations of throat, larynx and abdominal/thoracic organs, swallowing, voice production, slowing of heartbeat, acceleration or peristalsis (gut movement)

accessory nerve

conducts impulses from from brain to certain shoulder and neck muscles
shoulder movements, turning movement of head

hypoglossal nerve

conducts impulses from brain to muscles of tongue
tongue movements

meninges

three protective layers of connective tissue membranes enveloping brain and spinal cord
protects brain and spinal cord

dura mater

outer layer of meninges, tough and thick, closest to skull

arachnoid mater

middle layer of meninges, web-like,

pia mater

innermost layer of menignes, directly on brain and spinal cord tissue

epidural space

space outside/above dura mater

subdural space

space beneath dura mater

subarachnoid space

spce between arachnoid and pia layers, filled with CSF, helps cushion brain