neurobiology 205 - exam two

superior/cranial

superior/cranial

towards head end of body; upper

inferior/caudal

away from the head; lower

anterior/rostral

front (in rat, towards nose)

posterior/caudal

back (in rat, towards tail)

dorsal

back (in rat, towards spine)

ventral

front (in rat, towards belly)

midline

runs down middle of nervous system

medial

towards midline of body

lateral

away from midline of body

ipsilateral

two structures on same side of midline

contralateral

opposite sides of midline

midsagittal plane

split brain into equal right and left halves, rostral to caudal

sagittal plane

sections parallel to mid-sagittal plane

horizontal plane

parallel to ground

coronal plane

perpendicular to ground and sagittal plane, splits brain into anterior and posterior parts

cerebrum

rostral most and largest part of brain; right hemisphere receives sensations from and controls movements of left side; left hemisphere monitors sensations and movement from right side of body

deep sagittal fissure

splits cerebrum down the middle into two cerebral hemispheres

cerebellum

behind cerebrum; movement control center with extensive connections to cerebrum and spinal cord; left side cerebellum coordinates movements on left side of body; right side cerebellum coordinates movements on right side of body; though smaller, contains as many neurons as entire cerebrum

brain stem

fibers and cells relay information from cerebrum to spinal cord and cerebellum and vise versa; site where vital functions are regulated (breathing, consciousness, body temperature); damage to brain stem is usually fatal

spinal cord

attached to brain stem, encase in bony vertebral column; conduit of information from skin, joints, and muscles of body to the brain and vise versa; transection of spinal cord results in paralysis caudal to cut (muscles function but cannot be controlled by brain)

spinal nerves

how spinal cord communicates with body, exist spinal cord through notches between vertebra

dorsal root: brings information into spinal cord, sensory

ventral root: carries information away from spinal cord, motor

somatic PNS

spinal nerves that innervate skin, joints, and muscles under voluntary control

somatic motor neurons

command muscle contraction; derive from motor neurons in ventral spinal cord; cell bodies lie in CNS but axons lie in PNS

somatic sensory axons

innervate and collect information from skin, muscles, and joints, enter spinal cord via dorsal roots

dorsal root ganglia

somatic sensory cell bodies lie outside spinal cord in clusters; one for each spinal nerve

visceral PNS

involuntary, vegetative, or autonomic nervous system; consists of neurons that innervate internal organs, blood vessels, and glands and bring information about visceral function to CNS

visceral motor fibers

command contraction and relaxation of smooth muscles, rate of cardiac muscle contraction, and secretory function of glands

afferent neurons

bring information into CNS

efferent neurons

emerge from CNS to innervate muscles and glands

cranial nerves

12 pairs arise from spinal cord and innervate head; numbered anterior to posterior

I. olfactory

special sensory axons; sensation of smell

II. optic

special sensory axons; sensation of vision

III. oculomotor

somatic motor and visceral motor axons; movements of eye/eyelid and parasympathetic control of pupil size

IV. trochlear

somatic motor axons; movements of eye

V. trigeminal

somatic sensory and somatic motor axons; sensation of touch to face, movement of muscles of mastication

VI. abducens

somatic motor axons; movements of eye

VII. facial

somatic motor, special sensory axons; movement of muscles of facial expression and sensation of taste in anterior two-thirds of tongue

VIII. auditory-vestibular

special sensory axons; sensation of hearing and balance

IX. glossopharyngeal

somatic motor, visceral motor, special sensory, and visceral sensory axons; movement of muscles in throat, parasympathetic control of salivary glands, sensation of taste in posterior 1/3 of tongue, detection of blood pressure changes in aorta

X. vagus

visceral motor, visceral sensory, and somatic motor axons; parasympathetic control of heart, lungs, and abdominal organs; sensation of pain associated with viscera; movement of muscles in throat

XI. spinal accessory

somatic motor axons; movement of muscles in throat and neck

XII. hypoglossal

somatic motor axons; movement of tongue

meninges

three membranes protecting CNS from overlying bone

dura mater

“hard mother”, outermost covering; tough, inelastic bag surrounding brain and spinal cord

arachnoid membrane

under dura, has appearance and consistency resembling a spider web

subdural hematoma

ruptured blood vessels passing through dura are ruptured, blood collects and disrupts brain function due to compression of CNS

pia mater

“gentle mother”, thin membrane adheres to brain surface; many blood vessels dive into brain surface; separated from arachnoid by subarachnoid space filled with salty clear liquid (CSF)

ventricular system

fluid filled caverns and canals inside brain

choroid plexus

produces cerebral spinal fluid (CSF) in ventricles of cerebral hemispheres

flow of CSF

choroid plexus in lateral ventricles → interventrical foramina → third ventricle → cerebral aqueduct → fourth ventricle → median aperture → subarachnoid space → absorbed by blood vessels at arachnoid villi

gray matter

generic term for a collection of neuronal cell bodies in CNS

cortex

collection of neurons that form a thin sheet, usually at brain’s surface

nucleus

distinguishable mass of neurons, deep in brain

substantia

related neurons deep within brain, usually with less distinct border than those of nuclei

locus

small, well-defined group of cells

ganglion

collection of neurons in peripheral nervous system

nerve

bundle of axons in PNS

white matter

collection of CNS axons

tract

collection of CNS axons with common site of origin and common destination

bundle

collection of axons that run together but do not necessarily have same origin and destination

capsule

collection of axons connect cerebrum with brain stem

commissure

collection of axons that connect one side of brain with other side

lemniscus

tract meanders through brain like ribbon

sulci and gyri formation

result from expansion of cerebral cortex expansion during fetal development, which folds and wrinkles to fit into skull

cerebral cortex

thin sheets of neurons just under surface of cerebrum, parallel to brain surface; human reasoning and cognition: lack of cerebral cortex is blind, deaf, dumb and unable to initiate voluntary movement

cerebral cortex layer I

layer of neurons closest to surface (most superficial cell layer), separated from pia mater by a zone that lacks neurons

cerebral cortex apical dendrites

one cell layer contains pyramidal cells that extend to layer one to form branches

deep central sulcus

marks posterior border of frontal lobe, caudal to which lies the parietal lobe

frontal lobe

“action cortex”, emotion center, reasoning

parietal lobe

integrating sensory information

insula

sensation of pain is judged

occipital lobe

visual processing center

temporal lobe

sensory processing, long-term memory and modulation

hippocampus

medial to lateral ventricle; single cell layer; learning and memory; spatial memory and consolidation of declarative memory

amygdala

emotional learning, fear and behavior

corpus callosum

connects hemispheres

cingulate gyrus

links motivational outcomes to behavior

fornix

output tract on hippocampus (learning and memory)

thalamus

major sensory relay center

hypothalamus

body homeostasis, hormones release

pineal body

melatonin

midbrain

relay center, substantia nigra

pons

regulation of respiration, control of involuntary actions

medulla

transmitting signals between spinal cord and the brain, controls autonomic activities such as heartbeat and respiration

olfactory cortex

continuous with olfactory bulb; connected ventrally and laterally; two cell layers (connected to olfactory bulb, sits further anterior)

rhinal fissure

separates olfactory cortex from neocortex

neocortex

neocortex only found in mammals; cytoarchitectural map of neocortex divides into different zones; brodmann proposed that neocortex expanded by insertion of new areas

primordial neocortex of common mammalian ancestor

primary sensory areas, secondary sensory areas, motor areas

primary sensory areas

first to receive signals from ascending sensory pathways

secondary sensory areas

heavy interconnections with primary sensory areas

motor areas

intimately involved with control of voluntary movement; receive inputs from thalamic nuclei that relay information from basal telencephalon and cerebellum, send outputs to motor control neurons in brain stem and spinal cord

association areas

areas in frontal and temporal lobes remaining after primary/secondary sensory areas and motor area; more recent evolutionary development

flavor detection

unique combination of distinct tastes; flavors result from simultaneous taste and smell; sensory modalities such as temperature, texture, and pain sensations

organs of taste

tongue, palate, pharynx, epiglottis

papillae

small ridge, pimple or mushroom projections containing 1-several hundred taste buds; each taste bud has 50-150 taste receptor cells; each papilla has multiple types of taste receptor cells

taste receptor cells

apical end: near tongue surface, chemically sensitive part with microvilli that extend into taste pore

form synapses with endings of gustatory afferent axons near the bottom of the taste bud; electrical and chemical synapses onto basal cells which many then synapse onto sensory axons to form simple information-processing circuit within each taste bud

taste receptor membrane potential

voltage shift (depolarization) when appropriate chemical activates taste receptor may fire action potential, triggering synaptic transmission from taste cell to sensory axon and ultimately to brain stem

taste receptor transmitters

acetylcholine, GABA, glutamate: unknown functions

ATP: umami, sweet, bitter taste cells

serotonin: sour, salty