Unit 5 Key Terms/Concepts

central nervous system (CNS)

• integration, processing, coordination

• brain and spinal cord

peripheral nervous system (PNS)

• sensory division (afferent): info from receptors to CNS

• motor division (efferent): from CNS to effector organs (muscle & glands)

• somatic: voluntary

• autonomic: involuntary (parasympathetic & sympathetic)

autonomic nervous system (PNS)

regulates involuntary bodily functions such as heart rate, digestion, and respiratory rate

parasympathetic division (ANS)

responsible for activities that conserve energy and lower metabolic rate

sympathetic division (ANS)

responsible for “fight or flight” reactions, elevation of metabolic rate and increased alertness

somatic nervous system (PNS)

controls voluntary movements of skeletal muscles

motor/efferent division (PNS)

carries motor commands from the CNS to peripheral tissues and systems

sensory/afferent division (PNS)

brings information to the CNS from receptors in peripheral tissues and organs

synaptic/axon terminals

an axon end where the neuron communicates with other cells

synapse

a specialized site where the neuron communicates with another cell

vesicles

small membrane-bound sacs that store and release neurotransmitters at the synapse

role of calcium in neurotransmitter release (AI)

Calcium ions trigger the fusion of vesicles with the presynaptic membrane, leading to the release of neurotransmitters into the synaptic cleft.

axon hillock

the origin of the axon from the cell body

dendrites

receive stimuli from the environment or from other neurons

cell body

contains the nucleus and other organelles 

axon

carries information toward other cells

axolemma

a specialized portion of the plasma membrane that surrounds the cytoplasm

axoplasm

the cytoplasm within an axon that contains organelles and proteins

neurofilaments

microfilaments in the cytoplasm of a neuron

neurofibrils

microfibrils in the cytoplasm of a neuron

telodendria

small branches at the end of an axon

anaxonic neurons

• small and lack anatomical features that distinguish dendrites from axons; all the cell processes look alike

• functions are poorly understood

bipolar neurons

• 2 distinct processes, one dendritic process that branches extensively at its distal tip and one axon with the cell body between the two

• rare, occurs in special sense organs where they relay information about sight, smell, or hearing from receptor cells to other neurons

unipolar neuron

a sensory neuron where the dendrites and axon are continuous and the cell body lies off to one side

multipolar neuron

• have 2 or more dendrites and a single axon

• most common in the CNS, all motor neurons that control skeletal muscles are multipolar neurons

ganglion

a collection of neuron cell bodies in the PNS

ependymal cells (CNS)

assist in producing, monitoring, and circulating CSF

microglia (CNS)

migrate into the CNS as the nervous system forms, removes cellular debris, wastes, and pathogens by phagocytosis

astrocytes (CNS)

maintains the blood-brain barrier, provides structural support, regulates ion, nutrient, and dissolved gas concentrations in the interstitial fluid surrounding the neurons

oligodendrocytes (CNS)

provides a structural framework within the CNS by stabilizing the positions of axons, produces myelin

myelin

a membranous wrapping around axons that increases the transmission speed of nerve impulses and insulates it

cerebrospinal fluid (CSF)

• acts as a shock absorber and a diffusion medium for dissolved gases, nutrients, chemical messengers, and wastes

• located in the spaces surrounding the brain and spinal cord

white matter

regions in the CNS that are dominated by myelinated axons

gray matter

areas in the CNS that are dominated by neuron cell bodies, neuroglia, and unmyelinated axons

Schwann cells (PNS)

cover peripheral axons in 2 different ways and participate in axon repair after injury

satellite cells (PNS)

surround peripheral cell bodies, regulates environment around the neurons

resting membrane potential

the membrane potential of an undisturbed cell, -70mV

Na/K Pump

uses ATP to move 3 Na+ out and 2 K+ into the cell, creates a differential in charges

ligand gated channels

neurotransmitters bind to these specific channels and open Na+ channels; Na+ diffuses down its gradient into the cell, making the inside more positive

voltage-gated channels

neuron reaches threshold resulting in the opening of these channels at the axon hillock/initial segment allowing Na+ to flow into the cell down its concentration

depolarization

a change in the membrane potential from a negative value toward 0 mV

hyperpolarization

the movement of the membrane potential away from the normal resting potential and farther from 0 mV

all-or-none principle

a given stimulus either triggers a typical action potential or triggers none at all

absolute refractory period

the membrane cannot respond to further stimulation

relative refractory period

the membrane can respond only to a larger-than-normal stimulus

regions and segments of spinal cord

8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal

conus medullaris

the conical tip of the spinal cord that gives rise to the filum terminale

cauda equina

spinal nerve roots distal to the tip of the adult spinal cord; extends caudally inside the vertebral canal en route to lumbar and sacral segments

meninges

a series of specialized membranes surrounding the spinal cord, provide the necessary physical stability and shock absorption

anterior gray horns

contains somatic motor nuclei

lateral gray horns

located only in thoracic and lumbar segments, contains visceral motor nuclei

endoneurium

innermost layer, consists of delicate connective tissues that extend from the perineurium and surround individual axons

perineurium

the middle layer, these connective tissue partitions divide the nerve into a series of compartments that contain bundles of axons called fascicles

epineurium

the outermost covering of the nerve, consists of a dense network of collagen fibers

shingles

a herpesvirus that attacks neurons within the posterior roots of spinal nerves and sensory ganglia of cranial nerves, causing painful rashes and blisters

gray commissures

posterior and anterior to the central canal, contain axons that across from one side of the cord to the other before they reach a destination in the gray matter

anterior white commissure

interconnects the anterior white columns, axons cross from one side of the spinal cord to the other

anterior root

contains the axons of motor neurons that extend into the periphery to control somatic and visceral effectors

posterior root

contains the axons of the neurons whose cell bodies are in the posterior root ganglion

cervical plexus (C1-C5)

innervates the muscles of the neck and diaphragm

brachial plexus (C5-T1)

innervates the pectoral girdles and upper limbs

lumbar plexus (T12-L4)

innervates the pelvic girdle and lower limbs

sacral plexus (L4-S4)

innervates the pelvic girdle and lower limbs

reflex

rapid, automatic responses to specific stimuli

gyri

folds in the cerebral hemispheres that increase its surface area

sulci

shallow grooves in the cerebral hemispheres that separate adjacent gyri

fissues

deep grooves that subdivide each cerebral hemisphere

pons

connects the cerebellum to the brainstem, contains nuclei that function in somatic and visceral motor control

midbrain

contains nuclei that process visual and auditory information and control reflexes triggered by these stimuli, helps maintain consciousness

medulla oblongata

relays sensory information to other portions of the brainstem and to the thalamus, regulates autonomic functions like HR and BP

lateral ventricle

a fluid-filled chamber within a cerebral hemisphere

interventricular foramen

the opening that permits fluid movement between the lateral and third ventricles of the brain

third ventricle

located in the diencephalon

cerebral aqueduct

a slender canal within the midbrain that connects the third ventricle to the fourth ventricle

fourth ventricle

begins in the metencephalon and extends into the superior portion of the medulla oblongata, then narrows and becomes the central canal of the spinal cord

arbor vitae

the central branching mass of white matter inside the cerebellum, “the tree of life”

substantia nigra

contains darkly pigmented cells that inhibit activity in the basal nuclei of the cerebrum, secretes dopamine

frontal lobe

executive function, somatic motor

temporal lobe

auditorypa

parietal lobe

somatic sensory

occipital lobe

visual

sensory receptors

specialized cells that inform your CNS about conditions inside or outside the body

receptive field

the area monitored by a single sensory receptor

proprioception

monitors the positions of joints and muscles

nociceptors

pain receptors that do not adapt quickly