anatomy - unit 3

what organ systems deal with communications within the body? how do they differ?

the organ systems that deal with communication within the body are the nervous system and the endocrine system; the nervous system uses electrical and chemical signals (via neurons) to maintain homeostasis, while the endocrine system relies on hormones (chemical signals)

how is the nervous system divided structurally? what are the organs in each division? define them

the nervous system is divided into the central (CNS) and peripheral (PNS) nervous systems; the organs in the central nervous system are the brain, the spinal cord, nuclei (cell bodies) and tracts (bundles of axons); the organs in the peripheral nervous system are the nerves (bundles of nerve fibers), which include the cranial (from the brain) and spinal (from the spine) nerves, and the ganglia (bundles of cell bodies of neurons)

what are receptors?

cells or dendrite endings of neurons that detect stimuli (changes in the environment)

what are effectors? name some examples and which division they are a part of

effectors carry out responses or effects from motor neurons; some examples are skeletal muscles (in the somatic motor division), cardiac and smooth muscles, and glands (all in the visceral motor division)

how is the nervous system divided functionally?

the nervous system is divided into the sensory/afferent and motor/efferent divisions

components/organs of sensory/afferent division

somatic sensory division, which is further categorized into the general (touch, nociception, pressure, vibration, temperature, and proprioception) and special (taste, vision, hearing, equilibrium, and olfaction) senses, carries signals from receptors of skin, muscles, bones, and joints; visceral sensory division carries signals from the receptors of thoracic and abdominal viscera

components of motor/efferent division

somatic motor division carries signals to skeletal muscles; visceral motor division carries signals to glands, cardiac, and smooth muscles, and can be further categorized into the sympathetic (“fight or flight”) and parasympathetic (“rest and digest”) divisions

what are the properties of neurons and their functions?

excitability (responds to stimuli),

conductivity (electrical signals are produced in response to stimuli),

secretion (neurons secrete neurotransmitters after electrical signals go to axon terminal to stimulate other cell),

high metabolic rate (utilizing glucose and oxygen),

longevity (neurons functional for many years),

nonmitotic (for MOST neurons)

what are the structures of a neuron and its functions?

neuron: nerve cells that communicate using electrical and chemical signals

soma: control center of neuron, contains the nucleus where signals are received, integrated, and sent

dendrites: shorter processes from soma that receives signals from stimuli or other neurons

axon: longer single process from soma that sends signals to other cells

• axon hillock: mound where axon begins and action potential begins

• axon terminal: ends of the axon

synapse: junction between axon terminal and target cell’s plasma membrane

structurally, what are the different types of neurons and examples of where they are found?

multipolar neurons (most common in brain, spinal cord)

bipolar neurons (olfactory neurons, retina neurons, and inner ear neurons)

unipolar/pseudounipolar neurons (somas found in ganglia, most sensory neurons in PNS)

anaxonic neurons (retina, brain, medulla)

functionally, what are the different types of neurons and examples of where they are found?

sensory/afferent neurons (usually in posterior root ganglion); interneuron/ association neuron (found entirely in CNS); motor/efferent neuron (usually in spinal cord)

what are the different types of glial cells within the CNS? what are their functions and where are they found?

oligodendrocytes: one forms myelin sheath around many CNS axons, allowing quicker signal conduction

ependymal cells: lines the internal cavities of brain, spinal cord to produce CSF (cerebrospinal fluid), contains cilia to circulate CSF

microglia: macrophages that phagocytize dead tissues, microbes, foreign material

astrocytes: forms supportive framework, blood-brain barrier (prevents blood substances from entering brain), converts blood glucose to lactate, secretes nerve growth factor, regulates chemicals around neurons absorbing neurotransmitters and potassium ions, and forms scar tissue when damage presents

what are the different types of glial cells within the PNS? what are their functions and where are they found?

neurolemmocyte/ Schwann cells: many wrap around one axon in PNS, could form myelin sheath for quicker conduction

satellite cells: surrounds neurosomas or cell bodies in ganglia for electrical insulation around soma and regulate chemical environment, including nutrients and wastes

how are neurolemmocytes different from oligodendrocytes?

neurolemmocyte: multiple wrap around one axon

oligodendrocyte: one forms myelin sheath and wraps around multiple axons

what is a myelin sheath?

one oligodendrocyte or multiple neurolemmocytes that wrap around axons to insulate them

what is a neurilemma?

outermost layer of the myelin sheath

what are neurofibril nodes/ nodes of Ranvier/ myelin sheath gaps?

spaces between the myelin sheaths for nerve impulses

what is an endoneurium?

connective tissue that wraps around axon

what’s the differences of unmyelinated nerve fibers in the CNS vs PNS?

CNS: unmyelinated nerve fibers don’t have oligodendrocytes

PNS: unmyelinated nerve fibers have one Schwann cell that surrounds many nerve fibers but doesn’t wrap around many times

myelinated vs unmyelinated nerve fibers

myelinated nerve fibers: faster action potential, used by skeletal muscles

unmyelinated nerve fibers: slower action potential, used by pain and some cold stimuli

gray matter vs white matter. give examples

gray matter: unmyelinated components of neuron (dendrites, soma, unmyelinated axons)

white matter: myelinated axons

what is the difference between the brain and spinal cord in regards to their gray and white matter?

brain: gray matter (cerebral cortex) around white matter around gray matter (nuclei)

spinal cord: white matter (funiculi/fasciculata) around gray matter (horns)

nerve regeneration can occur in which division of the nervous system?

in the PNS

what is the connective tissue that surrounds the axons of neurons?

endoneurium (areolar connective tissue)

name the different types of nerves and how they are different

sensory nerves (afferent fibers); motor nerves (efferent fibers); mixed nerves (both afferent and efferent fibers)

what are the different types of soma?

ganglion; nuclei

what is a synapse?

location where axon terminal of neuron meets with target cell’s plasma membrane

what are the components of a synapse? define each of these terms

presynaptic neuron: neuron prior to synapse, innervates target cell

synaptic cleft: gap between axon terminals and target cell where neurotransmitters from presynaptic neuron diffuses across to target cell

target cell: cell that presynaptic neuron innervates;

• postsynaptic neuron: neuron after synapse and is target cell of presynaptic neuron

what are the different types of synapses? define them

CNS: neuron to neuron

• axodendritic: presynaptic axon synapse at postsynaptic dendrites

• axosomatic: presynaptic axon synapse at postsynaptic soma

• axoaxonic presynaptic axon synapse at postsynaptic axon

PNS: neuron to effector (muscle [neuromuscular/myoneural junction] or gland)

parts of the brain and their components

cerebrum

diencephalon

• epithalamus

• thalamus

• hypothalamus

• neurohypophysis

brainstem

• midbrain

• pons

• medulla oblongata

cerebellum

what structures make up the diencephalon?

epithalamus, thalamus, hypothalamus, neurohypophysis

what structures make up the brainstem?

what is rostral vs caudal?

rostral (towards the nose): superior and front part of brain

caudal (towards the tail): inferior and back part of brain

how gray matter is composed within the brain? what is within this area?

little myelin, mostly somas, dendrites, and proximal portions of axons

• cerebral cortex

• nuclei

how white matter is composed within the brain? what is within this area?

highly myelinated axons called tracts

what structures help support and protect the brain?

the cranium, meninges, cerebrospinal fluid, and the blood-brain barrier

what are meninges?

fibrous connective tissue that surrounds and protects the central nervous system (CNS)

what are the different meninges and spaces between them?

dura mater

• subdural space

arachnoid mater

• subarachnoid space

pia mater

what structures do they form?

the dura mater forms the dural sinus and the meningeal layer; the arachnoid mater forms the arachnoid villi

what are dural sinuses? name one dural sinus

dural sinuses are veins that pool blood and CSF to be emptied out from the brain into the internal jugular veins (ie. superior sagittal sinus)

what is the falx cerebri?

it separates the right and left hemisphere within the longitudinal fissure

what are arachnoid villi and what does it do?

arachnoid villi are extensions of arachnoid mater that passes CSF from subarachnoid space into the dural venous sinuses

what are the different ventricles of the brain?

• right and left lateral ventricles

• third ventricle

• fourth ventricle

what is the order that CSF flows through the ventricles?

from the lateral ventricles to the third ventricle, through the cerebral aqueduct, into the fourth ventricle