test 4-nervous system

three functions of the nervous system

control and interpret sensations and muscle movements; primary communication and control system; integrate and regulate body functions

sensory - functionality division

specialized to detect stimuli

interneurons neurons

lie entirely within the CNS; receive signal from many neurons and carry out the integrative function

motor - functionality division

send signals out to muscles and gland cells to the effectors

somatic - sensory

sensory input that is consciously perceived from receptors (eyes, skin ears)

visceral - sensory

sensory input that is not consciously perceived from blood vessels and internal organs (heart)

somatic - motor

motor output that is consciously or voluntarily controlled; effector is skeletal muscle

autonomic - motor

motor output that is not consciously or is involuntarily controlled; effectors are cardiac muscle, smooth muscle, and glands

neurons

basic structural unit of the nervous system; excitable cells that transmit electrical signals

neuroglia

non excitable cells that primarily support and protect neurons

excitability

most respond only to binding of molecules, neurotransmitters

conductivity

electrical charges propagated along membrane; can be local and short-lived or self-propagating

secretion

release neurotransmitters in response to electrical charges; given neuron releasing only one type of neurotransmitter

extreme longevity

most formed before birth still present in advanced age

amitotic

mitotic activity lost in neurons, not always the case; occasionally the hippocampus

axon

longer process emanating from cell body making contact with other neurons, muscle cells, or glands

axon hillock

triangular region of the axon

axon collaterals

side branches emitting from axon

telodendria

terminal branches

cell body

enclosed by plasma membrane and does not have centrioles

unipolar

single process leading away from the soma; sensory from skin and organs to spinal cord

bipolar

one axon; one dendrite; olfactory cells, retina, and inner ear

multipolar

one axon; multiple dendrites; most common; in brain and spinal cord

sensory - neuron classification

specialized to detect stimuli

motor - neuron classification

send signals out to muscles and gland cells (to the effectors)

interneurons

lie entirely within the CNS; receive, process, and store information; facilitate communication between sensory and motor neurons; 99% of neurons

endoneurium

delicate layer of areolar connective tissue that separates and electrically insulates each axon

perineurium

layer of dense irregular connective tissue wrapping bundles of axons, fascicles

epineurium

thick layer of dense irregular connective tissue enclosing the entire nerve

cranial nerves

12 nerves that originate from the brain or brainstem; numbered consecutively with different functions

spinal nerves

extend from the spinal cord (31 pairs)

motor - nerve classification

contains primarily motor neurons

sensory - nerve classification

contains only sensory neurons

mixed - nerve classification

contains both sensory and motor neurons; most named nerves are in this category; individual neurons transmitting one type of information

astrocytes

most abundant glial cell in CNS; anchor neurons; cover entire brain surface and most non synaptic regions of neurons in gray matter of the CNS

ependymal cells

lines internal cavities of brain; cuboidal epithelium with cilia on apical surface; secretes and circulates CSF

microglia

small wandering macrophages that phagocytize foreign particles; thought to perform complete checkup on brain tissue several times a day

oligodendrocytes

produce myelin sheaths in CNS; each arm like process wraps around a nerve fiber forming an insulating layer that speeds up signal conduction

satellite cells

arranged around neuronal cell bodies in ganglion; physically separate cell bodies in ganglion from surrounding fluid; regulate the exchange of nutrients and waste products

neurolemmocytes

envelope nerve fibers in PNS; wind repeatedly around a nerve fiber; produce a myelin sheath similar to the ones produced by oligodendrocytes in CNS; assist in the regeneration of damaged fibers; allow faster action potentials propagation

gyri

ridges on the outer surface of the brain

sulci

depressions between ridges

fissures

deep sulci

rostral

anterior

caudal

posterior

prosencephalon

the forebrain

mesencephalon

midbrain

rhombencephalon

hindbrain

telencephalon

arises from the prosencephalon and eventually forms the cerebrum

diencephalon

posterior region of the forebrain; includes the epithalamus, thalamus, and hypothalamus

metencephalon

arises from the rhombencephalon and eventually forms pons and cerebellum

myelencephalon

derives from the rhombencephalon and eventually forms the medulla oblongata

dura mater

tough leathery outermost layer composed of dense irregular connective tissue

arachnoid mater

spider web like middle layer composed of collagen and elastic fibers

pia mater

very thin innermost layer of areolar connective tissue conforming to the shape and contours of the brain

cranial dural septa

double layers of dura mater; separate specific parts of the brain and provide additional support

falx cerebri

formed by invagination of dura mater into longitudinal fissure

falx cerebelli

largest of the four dura septa

diaphragma sellae

smallest of the dura septa

2 lateral ventricles

two large cavities in cerebrum; separated by medial partition , septum

septum pellucidum

thin medial partition dividing the two lateral ventricles

third ventricle in diencephalon

narrow space in middle of diencephalon; connected to each lateral ventricle by an interventricular foramen

fourth ventricle

sickle-shaped space between pons and cerebellum; connected to the third ventricle by cerebral aqueduct; opens to subarachnoid space medially and laterally; narrows before merging with central canal of spinal cord

cerebrospinal fluid

clear colorless liquid that fills the ventricles and canals of CNS and bathes external surfaces; brain produces and absorbs 500 mL/day

buoyancy

reduces brain’s apparent weight by 95%

protection

provides a liquid cushion

environmental stability

transport of nutrients/wastes and protects against fluctations

choroid plexus

special tissue in each ventricle; layer of ependymal calls and blood capillaries within pia; produces by secretion from ependymal cells; originates from blood plasma; composition somewhat similar to plasma

blood brain barrier

regulates which substances enter brain’s interstitial fluid; helps prevent neuron exposure to harmful substances; drugs waste and abnormal solute concentrations; some drugs can pass through and affect the brain (alcohol)

perivascular feet

astrocyte extensions

longitudinal fissure

divides right and left hemispheres that make up the cerebellum

corpus callosum

how hemispheres communicate

hemisphere lateralization

specialization of each hemisphere for certain functions; some higher order functions exhibit lateralization and are primarily controlled by one side of the brain; left hemisphere receives sensory signals from the right side and sends motor signals to the right side

frontal lobe

motor control, concentration, verbal communication, decision making, planning, personality

central sulcus

border posterior to the frontal lobe

lateral sulcus

separates inferior frontal lobe from temporal lobe

precentral gyrus

controls voluntary movement

parietal lobe

superoposterior side of the cerebrum; serves general sensory functions (evaluating shape and texture of object)

parietal occipital sulcus

border posterior to the parietal lobe

postcentral gyrus

ridge just posterior to the central sulcus

temporal lobe

functions include hearing and smell

occipital lobe

functions in vision and visual memory

insula

small lobe that can be observed by pulling away temporal lobe; functions in memory and sense of taste

diencephalon

includes the epithalamus, thalamus, and hypothalamus

epithalamus

forms posterior part of roof of diencephalon, covers third ventricle

pineal gland

melatonin and circadian rhythm

habenular nuclei

relay signals from the limbic system to the midbrain and are involved in visceral and emotional response to odors

thalamus

oval masses of gray matter on lateral sides of third ventricle; receives signals from all conscious senses except olfaction; relays some signals to appropriate part of cortex and filters out other signals distracting from subject of attention (background noise in a crowded room)

interthalamic adhesion

small midline mass of gray matter that connects the right and left thalamic bodies

hypothalamus

anteroinferior region of the diencephalon

infundibulum

extends inferiorly from the hypothalamus and attaches to the pituitary gland

master control of the autonomic nervous system

hypothalamus; projects descending axons to nuclei in the brainstem that influence heart rate, blood pressure, digestive activities, and respiration

master control of the endocrine system

hypothalamus; secretes hormones that control secondary activities in the pituitary gland

regulation of body temperature

hypothalamus

control of emotional behavior

hypothalamus at the center of the limbic system; controls pleasure, aggression, sex drive, fear, rage, and contentment

control of food intake

neurons in the ventromedial nucleus monitor glucose and amino acids in the blood and produce hunger sensations

control of water intake

neurons in the anterior nucleus of the hypothalamus monitor the concentration of dissolved substances in the blood to regulate thirst

regulation of circadian rhythms

hypothalamus; suprachiasmatic nucleus directs the pineal gland to secrete melatonin

pons

forms a bulge on the ventral side of the brainstem that contains tracts and nuclei

pontine respiratory center

the vital center; regulates skeletal muscle of breathing