brain ch 3-4

central nervous system (CNS)

division of nervous system located within skull and spine

composed to 2 additional divisons: spinal cord and brain

peripheral nervous system (PNS)

division of nevous system located outside skull and spine

composed of 2 additional divisons: domantic and autonomic nervous system

somantic nervous system (SNS)

interacts with external environment

afferent nerves-SNS

carry sensory signals from skin, skeletal muscles, joint, eyes to central nervous system

efferent nerves-SNS

carry motor signals from central nervous system to skeletal mucsles

autonomic nervous system (ANS)

regulates the body’s internal enviornment

afferent nerves-ANS

carry sensory signals from internal organs to CNS

efferent nerves-ANS

carry motor signals from CNS to internal organs

sympathetic nerves

autonomic motor nerves that project from CNS in the lumbar (small of the back) and thoracic (chest area) regions of spinal cord

parasympathetic nerves

autonomic motor nerves that project from the brain and sacral (lower back) region of spinal cord

cranial nerves

most of the nerves of peripheral nervous system project from spinal cord, but there are 12 pairs of exceptions, which project from brain

meninges

The brain and the spinal cord (CNS) are the most protected organs in the body. They are incased in bone and are covered by three protective membranes

dura mater

outer meninx, tough membrane

arachnoid membrane

inside dura matter, fine spider-web-like membrane

subarachnoid space

beneath arachnoid membrane, containing many large blood vessels and cerebrospinal fluid

pia matter

innermost meninx, which is delicated and adheres to the surface of the CNS

cerebrospinal fluid (CSF)

protects CNS

filled in the subarachnoid space, central canal, cerebral ventricles

central canal

small central chanel that runs the lenght of spinal cord

cerebral ventricles

four large internal chambers of the brain

two lateral ventricles, third ventricle, and fourth ventricle

choroid plexuses

cerebrospinal fluid is produced by this, which are networks of capillaries or small blood vessels that protrude into the ventricles in pia matter

blood-brain barrier

mechanism impedes passage of many toxis substances from blood into the brain

neurons

cells thar are specilized for reception, conduction, and transmission of electrochemical signals

neuron cell membrane

composed of a lipid bilayer (two layers of fat molecules) that contain numerous protein molecules that are the basis of many cell membrane’s functional properties

some membrane proteins are channel proteins through which certain molecules pass, while others are __*s*__ignal proteins that transfer signals to the inside of the neuron when particular molecules bind to them on the outside of the membrane

multipolar neuron

neuron with more than two processes extending from its cell body

unipolar neuron

neuron with one process extending from its cell body

bipolar neuron

neuron with two processes extending from its cell body

interneuron

neurons with either a short or no axon that integrates neural activity within single brain structure, not to conduct signals from one structure to another

nuclei

clusters of cell bodies in CNS

ganglia

clusters of cell bodies in PNS

tracts

bundles of axons in CNS

nerves

bundles of axons in periheral system

cell membrane

semipermeable membrane that encloses neuron

dendrites

short processes emanating from cell body, which receive most of the snaptic contacts from other neurons

axon hillock

cone shaped region at the junction between axon and cell body

axon

long-narrow process that projects from cell body

myelin

fatty insulation around many axons

nodes of ranvier

gaps between sections of myelin

cell body

metabolic center of neuron

soma

buttons

buttonlike endings of axon branches, which release chemical into stnapses

synapses

gaps between adjacent neurons across which chemical signals are transmitted

oligodendrocytes

glial cell with extensions that wrap around axons of some neurons of CNS

schwann cells

similar to oligodendrocytes performed in PNS

microglia

smaller than other glial cells and respond to injury or disease by multipyling, engulfing cellular debris or even entire cells, and triggering inflammatory responses

astrocytes

largest glial cells shaped like star

extensions of some astrocytes cover the outer surface of blood vessels that course through brain, and making contact with neurons

golgi stain

commonly used when the overall shape of neurons is of interest and provides a view of the silhouettes of the few nurons that make up the stain. isnt indicative of the number of neurons in the area

nissl stain

often used to estimate the number of cell bodies in an area, by counting the number of nissl-stained dots

electron microcopy

information about detaşks of neuronal structure

neuroanatomical tracking techniques

consist of two types: anterograde (forward) tracing method and retrograde (backwards) tracking method

anterograde tracking method

used when one wants to trace the path of axons projecting away from cell bodies located in particular area

retrograde tracking method

used when one wants to trace the path of axons projecting into a particular area

anterior - posterior

nose end - tail end

dorsal - ventral

toward the surface of the back or top of the head - toward the surface of the chest or bottom of the head

medial - lateral

toward the midline of the body - away from the midline toward to body’s external surface

superior - inferior

refer to the top and bottom of primate head

proximal - distal

close - far

midsagittal section

a section cut down the center of the brain between two hemispheres

cross section

a section cut at a right angle to any long- narrow structure such as spinal cord or nerve

gray matter

spinal cord area, H-shaped

composed largely of cell bodies and unmyelinated interneurons

white matter

spinal cord

composed largely of myelinated axons

glossy white sheen is a result of the myelin

dorsal horns

two dorsal arms of the spinal gray matter

ventral horns

two ventral arms of spinal gray matter

spinal verves

attacked to the spinal cord, on the left and on the right at 31 different levels of spine each, 62 spinal nerves divide around the chord, and its axons are joined to the cord via dorsal and ventral root

dorsal root

all axons, whether somantic or autonomic, are sensory (afferent) unipolar neurons with their cell bodies grouped together just outside the cord to form dorsal root ganglia

many of their synaptic terminals are in the dorsla horns of the spinal gray matter

ventral root

neurons of this are motor (efferent) multipolar neurons with their cell bodies in the ventral horns

those that are part of the somatic nervous system project to skeletal muscles, while those a part of the autonomic nervous system project to ganglia, where they synapse on neurons that in turn, project to internal organs.

myelencephalon

medulla, part of brain stem

composed largely of tracts carrying signals between the rest of the brain and body

metencephalon

like the myelencephalon, houses may ascending and descending tracts and are part of reticular formation

two division: pons and cerebellum

pons

brain stem’s ventral surface

including the regulation of breathing, sleep, taste, facial movements, hearing, balance, eye movements, and facial sensation.

serves as a bridge connecting different parts of the brain, including the cerebellum, cerebral cortex, and spinal cord, and is involved in relaying sensory and motor information between these structures.

cerebellum

large, convoluted structure on brain stem’s dorsal surface

important sensorimotor structure; damage eliminates the ability to precisely control one’s movement and to adapt them to changing conditions

mesencephalon

two divisions: tectum and tegmentum

tectum

roof

dorsal surface of the midbrain

the posterior pair, the inferior colliculi, have auditory function. The anterior pair, the superior colliculi, have visual-motor function, specifically to direct the body’s orientation toward/away from a particular visual stimulus

in lower vertebrates, the function of the tectum is solely based on visual-motor functions

tegmentum

ventral to the tectum

reticular formation and tracts of passage, also contains 3 colourful structure; periaqueductal gray, substantia nigra, and red nucleus

periaqueductal gray

gray matter situated around the cerebral aqueduct, the duct containing the third and fourth ventricles

substantia nigra and red nucleus

impoartan to the sensorimotor system

diencephalon

composed of two structures; thalamus and hypothalamus

thalamus

large, two-lobed structure that constitutes the top of the brain stem

one lobe sits on each side of the third ventricle, wich are both joined by massa intermedia which runs through the ventricle

hypothalamus

located below the anterior thalamus

plays important role in regulation of several motivated behaviours; sleep, eat, sexual behaviour

pituitary gland

it exerts its effect in part by regulating the release of hormons from it

which dangles from ventral surface of the brain

two structures appear on inferior surface of hypothalamus; optic chiasm and mammillary bodies

optic chiasm

point at which optic nerves from each eye come together

an X shape is created become some of the axons of the optic nerve **decussate** (cross over to the other side of the brain) via the optic chiasm. The decussating fibers are said to be **contralateral** (projecting from one side of the body to the other), and the nondecussating fibers are said to be **ipsilateral** (staying on the same side of the body)

mammillar bodies

pair of spherical nuclei located on inferior surface of hypothalamus just behind the pituitary

telencephalon

the largest division of the human brain, mediates the brain’s most complex functions

it initiates voluntary movement, interprets sensory input, and mediates complex cognitive processes such as learning, speaking, etc.

central fissure and lateral fissure

divide each hemisphere into four lobes; frontal lobe, pariental lobe, temporal lobe, occipital lobe

fissures - sulci

large furrows in convoluted cortex - small one

gyri

ridges between the fissures and sulci

large gyri are precentral gyri (frontal lobe), postcentral gyri (pariental lobe), superior temporal gyri (temporal lobe)

neocortex

new cortex

six-layered cortex of relatively recent evolution

longitudinal fissure

the cerebraş hemisphere are almost completed seperately by largest of the fissure

corpus callosum

hemisphere are connected by few tracts spanning the longitudinal fissure

columnar organization

neurons in a given vertical column of neocortex often form a mini-circuit that performs a single function

hippocampus

one important area of cortex that is not neocortex

plays a major role in some kinds of memory, particular memory for spatial location

limbic system

circuit of midline structure that circle the thalamus

involved in regulation of motivated behaviours, including four F’s of motivation: fleeing, feeding, fighting, and sexual behaviour

basal ganglia

voluntary motor responses and decision making

amygdala

involve in emotion, particulary fear

membrane potential

difference in electrical charge between inside and outside of a cell

microelectrodes

intracellular electrodes

neuron’s resting potential

steady membrane potential of about -70 mV

polarized

in its resting state, with the -70mV charge built up across its membrane, a neuron is said to be

ions

salts in neural tissue sparate into positively and negatively charged particles

ion channels

in resting neurons, there are more Na+ ions outside the cell than isnide, and more K+ ions inside than outside

this unequal distribution is maintained throught specilised porese

electrostatic pressure

reason for substantial pressure on Na+ ions to enter the resting neurons

resting membrane potential

opposite charges attract, -70mV charge attract the positively charged Na+ ions into resting neurons

random motion

reason for substantial pressure on Na+ ions to enter the resting neurons

Na+ ions to move down their concentration gradient

makes ions more liekly to move down their concetration gradient than up them, that is why Na+ will tend to enter