Anatomy Exam 3

What is the endocrine system?

communicates by means of chemical messengers (hormones) secreted into the blood

What is the nervous system?

employs electrical and chemical means to send messages from cell to cell (neurotransmitters)

What are the 3 steps the nervous system carries out its tasks?

1) sense organs receive information about changes in the body and the external environment, and transits coded messages to the spinal cord and brain
2) brain and spinal cord processes information relates it to past experiences, and determines what response is appropriate to the circumstances
3) brain and spinal cord issue commands to muscles and gland cells to carry out such a response

Basic steps of the nervous system:

1) pick up/send
2) processing
3) response

What is the central nervous system (CNS) ?

the brain and spinal cord; the control center of the body

What is the peripheral nervous system (PNS) ?

all of the nervous system except the brain and the spinal cord

Which system cannot do repair?

Central nervous system

Which system can do repair?

Peripheral nervous system

What is a nerve?

a bundle of nerve fibers (axons) wrapped in fibrous connective tissue

What is a ganglion?

a knot-like swelling in a nerve where neuron cell bodies are concentrated

What is sensory (afferent) divison?

carries sensory signals from various receptors to the CNS

What is somatic sensory divison?

carries signals from receptors in the skin, muscle, bones, and joints

What is visceral sensory divison?

carries signals from the viscera of the thoracic/abdominal cavities (organs)

What is afferent?

bring inward

What is motor (efferent) division?

carries signals from the CNS to gland and muscle cells that carry out the body's response

What is somatic motor division?

carries signals to skeletal muscles

What are somatic reflexes?

involuntary muscle contractions

What is the visceral motor division (autonomic nervous sytem)?

carries signals to glands, cardiac muscles, and smooth muscle

What are visceral reflexes?

Unconscious, automatic responses to stimulation of glands, cardiac or smooth muscle

What is the sympathetic division?

tends to arouse body for action, acceleration heart beat and respiration, while inhibiting digestive/urinary - fight or flight

What is the parasympathetic division?

tends to have calming effect, slows heart/breathing, stimulates digestive/urinary systems - rest/digest (blood in organs)

What is efferent?

outward

What are the properties needed for neurons?

excitability (irritability) , conductivity (transmit), secretion (communicate)

What are sensory (afferent) neurons?

specialized to detect stimuli, transmit information about them to the CNS

What are interneurons (association) neurons?

lie entirely within the CNS, receive signals from many neurons and carry out the integrative function (process, store, and retrieve information and 'make decision' that determine how the body responds

What is the processing center?

the interneurons - lie between, and interconnect the incoming sensory pathways, and the outgoing motor pathways of the CNS

What are motor (efferent) neurons?

send signal out to muscles and glands (the effectors)

Interneurons neurons stop where?

in spinal cord

What is the soma?

the control center of the neuron (one central region/cell body with 1 neucles/organelles)

What else can a soma be called?

neurosoma, cell body, or perikaryon

What are dendrites?

vast number of branches coming from a few thick branches from the soma

What is the main function of dendrities?

primary site for receiving signals from other neurons

What are axons (nerve fibers)?

originates from a mound of one side of the soma, cylindrical, specialized for rapid conduction of nerve signals to point remote to the soma

What is the axon hillock?

the mound of the one side of the soma - beginning

What is the axon collateral?

branches formed after the axon leaves the cell body

What is the axoplasm?

cytoplasm of axon

What is the axolemma?

plasma membrane of axon

Neurons only have one...

soma and axon

What is the terminal arborization?

Fine branches that end in axon terminal/terminal button which will form a junction/synpase with the next cell

What wraps around the axon?

myelination

Where do axons start?

axon hillock or trigger zone

What is a multipolar neuron?

One axon and multiple dendrites
Most common - most neurons in CNS (somatic motor neurons)

What are bipolar neurons?

one axon and one dendrite (special sensory neurons- smell, sight, and hearing)

What are unipolar neurons?

single process of leading away from the soma (dendrite right into axon) sensory from skin and organs to spinal cord - any information is being sent right away

When the soma is between the dendrites and axon...

the information is picked up by dendrites and processed in the soma, a decision then causes an action potential into axon (can pick up information but does not need to respond to it)

With soma off the side...

any information is atomically send down the axon, sensory information, the soma doesn't make the decision

Proteins made in the soma must be...

transported

What is axonal transport?

two-way passage of proteins, organelles, and other material along an axon

What is anterograde transport?

movement down the axon away from soma

What is retrograde transport?

movement up the axon toward the soma

What do microtubules do?

guide materials along axon

What is fast axonal transport?

occurs at a rate of 20-400 mm/day (direct train - no stops)

What is fast anterograde transport?

organelles, enzymes, synaptic vesicles, and small molecules (moves down to something at the end of the axon)

What is fast retrograde transport?

for recycled materials/pathogens - rabies, herpes simples, tetanus, polio viruses (back up the axon toward soma)

What is slow axonal transport?

always anterograde (away), moves enzymes, cytoskeletal components, and new axoplasm down the axon during repair and regeneration of damaged axons (indirect train - stops)

What are neuroglial cells?

supporting cells - support/protect neurons, bind neurons together and form framework for nervous tissue, in fetus guides migrating neurons to their destination (to build synapses), if mature neuron is not in synaptic contact with another neuron is covered by glial cells

What are oligodendrocytes?

Form myelin sheaths in CNS, each arm-like process wraps around a nerve fiber formation an insulating layer that speeds up signal conduction (octopus tentacles) - can wrap around one cell forming myelination on axon and another cell

Myelination can...

speed up rate of neuron, isolate/insulate neurons from each other (so the neurons don't touch each other)

What are microglia?

small, wandering macrophages formed white blood cells called monocytes, thought to perform and complete checkup on the brain tissue several times/day, wander in search of cellular debris to phagocytize

What are ependymal cells?

lines internal cavities of the brain, cuboidal epithelium with cilia on apical surface, secretes/circulates cerebrospinal fluid (CSF)

What are astrocytes?

These are abundant, star-shaped cells that account for nearly half of the neural tissue. These brace neurons and form barrier between capillaries and neurons. These also help control the chemical environment of the brain. (supportive framework, blood-brain barrier)

When neurons is damaged the astrocytes do what?

astrocytosis or sclerosis, astrocytes form hardened scar tissue and fill space formerly occupied by the neuron

Neurons can not...

do mitosis (astrocytes form scar-tissue in the brain)

What are Schwann cells?

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 regeneration of damaged fibers

What are satellite cells?

surround the neurosomas in ganglia of the PNS, provide electrical insulation around the soma, regulate chemical environment of the neurons

What is the difference between CNS and PNS?

CNS - brain and spinal cord
PNS - everything else; Schwann cells and satellite cells

What do satellite cells do?

create layer of protection/insulation to protect somas (ganglia)

What are tumors?

masses of rapidly dividing cells
mature neurons have little or no capacity for mitosis and seldom form tumors - the astrocytes form a blood-brain barrier causing chemotherapy to not be able to pass into brain

What are brain tumors?

they arise from metastasis from non-neuronal tumors in other organs; meninges (protective membranes of CNS); from glial cells that are mitotically active throughout life

What is a glioma?

a cancerous brain tumor composed of one of several types of glial cells- grow rapidly and are highly malignant - blood-brain barrier decreased effectiveness of chemotherapy- treatment consists of radiation or surgery

The myelin sheath in the PNS is formed by

Schwann cells individually wrapping membrane repeatedly around the axon pushing the nucleus/organelles cytoplasm into a bulge on the top

What is the neurilemma?

remaining nucleus and cytoplasm of a Schwann cell that creates a bulge

What is the endoneurium?

connective tissue that goes overtop everything on the axon insulating/protecting

The myelin sheath in the CNS is formed by...

oligodendrocytes - not one cell wrapping but rather a central cell with extensions of cytoplasm (tentacles) that wrap around the axon repeatedly

There is no what in the CNS

endoneurium

What is a myelin sheath?

an insulating layer around a nerve fiber

The myelination creates...

separation between different axons to avoid touching, letting communication happen between neurons and help speed up the rate of impulse

What is myelination?

production of the myelin sheath
Begins at week 14 of fetal development
Proceeds rapidly during infancy
Completed in late adolescence
Dietary fat is important to CNS development

PNS neurons can do

regeneration

What are the nodes of Ranvier?

gaps between schwann cells

What are internodes?

myelin covered segments from one gap to the next (each schwann cell)

What is the initial segment?

short section of nerve fiber between the axon hillock and the first glial cell (unmyelinated)

What is the trigger zone?

the axon hillock and the initial segment

What is multiple sclerosis?

oligodendrocytes and myelin sheaths in the CNS deteriorate; myelin replaced by hardened scar tissue; nerve conduction disrupted; cause may be autoimmune triggered by virus

What is Tay-Sachs disease?

a hereditary disorder of infants of Eastern European Jewish ancestry; abnormal accumulation of glycolipid called GM2 in the myelin sheath - can't digest myelination which causes lysosomes to fill up and crush axons

What is a mesaxon?

neurilemma wrapping of unmyelinated nerve fibers (like water bed)

Speed at which a nerve signal travels along a nerve fiber depends on two factors

diameter of fiber and presence of myelin or absense

Which type of nerve fibers have the fastest conduction speed?

big and myelinated

Which type of nerve fibers have the slowest conduction speed?

small and unmyelinated

Regeneration in PNS can occur if:

its soma is intact
at least some neurilemma remains

What is the regeneration tube?

formed by Schwann cells, basal lamina, and the neurilemma near the injury

What is the process of regeneration within PNS fibers?

1) a part of the axon is cut, the soma provided the nutrients for the axon
2) because one end of the axon can not get nutrients it degenerates (dies) - the macrophages pick up pieces, the endoneurium/Swann cells do not die as they are independent - the soma swells with rough ER for repair - the endoneurium/Swann cells create regeneration tube
3)the axon creates shoots to try to hook on into regeneration tube
4)the one sprout reforms axon, the other sprouts degenerate

The Sodium - Potassium pump pumps what?

3 sodium out, 2 potassium in with the use of ATP

What type of gradient is created by Sodium-Potassium?

electrical- chemical gradient

What does sodium naturally want to move?

inside the cell

What does potassium want to do?

outside in the cell

What are leakage channels?

on the membrane and are highly specific channels that allow the free diffusion of specific ions across the membrane

What is the resting membrane potential?

-70mV

What are ligand gated channels?

highly specific channel that opens when a certain ligand binds to it and is closed when its not

What are voltage gated channels?

highly specific channel that opens/closes at certain voltages