A&P 1 Yung Su Exam 3

Temporomandibular (jaw) joint (TMJ)

articulation of the

condyle of the mandible with the mandibular fossa of the

temporal bone

TMJ lateral ligament

prevents posterior displacement of mandible

TMJ Sphenomandibular ligament

on the medial side

Glenohumeral joint

hemispherical head of humerus articulates with glenoid

cavity of scapula

Glenoid labrum

fibrocartilage ring that deepens glenoid

cavity

Shoulder separation

results from a hit to the superior surface of shoulder forcing the acromion of scapula inferiorly – dislocates the clavicle from scapula at the acromioclavicular joint

Elbow joint

hinge joint that includes two articulations:

• Humeroulnar joint

• Humeroradial joint

Humeroulnar joint

trochlea of the humerus joins trochlear notch of the ulna

Humeroradial joint

capitulum of humerus meets head

of radius

proximal radioulnar joint

Head of radius fits into radial notch of ulna, not involved in hinge, held in place by annular ligament encircling radial head, pivot joint

Coxal(hip) joint

head of femur inserts into acetabulum of hip bone

Round ligament (ligamentum teres) of coxal bone

attaches fovea capitis on the head of the femur to the acetabulum of the coxal bone; contains artery that supplies blood to head of femur

Tibiofemoral (knee) joint

hinge joint between femur and

tibia; largest and most complex diarthrosis of the body

• Flexion and extension, but also capable of slight rotation

and lateral gliding when knee is flexed

patellofemoral joint

Patella and patellar ligament articulate with femur

lateral and medial menisci

Two shock absorbing cartilages in joint cavity joined by transverse ligament

Arthritis

a broad term for pain and inflammation of joints;

most common crippling disease in the United States

Rheumatologists

physicians who treat arthritis and other

joint disorders

Osteoarthritis

most common form of arthritis

• “Wear-and-tear arthritis”; results from years of joint wear

• Articular cartilage softens and degenerates; bone spurs develop on

exposed bone tissue causing pain

• Accompanied by crackling sounds called crepitus

Gouty arthritis

Occurs when uric acid or calcium salt crystals form within synovial

fluid. More common in males than females. Causes: family history,

increased age, alcohol consumption, foods rich in purines (animal

sources that break down into urate), high fructose corn syrup – soda

Rheumatoid arthritis

autoimmune attack against the joint tissues

• Misguided antibodies (rheumatoid factor) attack synovial

membrane, enzymes in synovial fluid degrade the articular

cartilage, joint begins to ossify

Ankylosis

solidly fused, immobilized joint

Arthroplasty

replacement of diseased joint with artificial

device called prosthesis

Endocrine system

communicates by means of chemical

messengers (hormones) secreted into to the blood

Nervous system

utilizes neurons (nerve cells) to send

messages from cell to cell by electrical and chemical

means; occurs in three steps:

3 steps in neural signaling

1. It receives stimuli from external environment and transmits

messages to central nervous system (CNS)

2. The CNS processes the information and determines the response

3. CNS issues commands to muscle and/or gland cells to carry out

the response

nerve

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

tissue

ganglion

a knot-like swelling in a nerve where neuron cell bodies of the

PNS are concentrated

Sensory(afferent) division

carries signals from receptors (sense organs) to CNS

Somatic sensory division

carries signals from receptors in the

skin, muscles, bones, and joints

Visceral sensory division

carries signals from the viscera (heart,

lungs, stomach, and urinary bladder)

Motor(efferent) division

carries signals from CNS to

the effectors (glands and muscles that carry out the

body’s response)

Somatic motor division

carries signals to skeletal muscles;

causes voluntary muscle contraction and automatic reflexes

Visceral motor division (autonomic nervous system)

carries signals to glands, cardiac, and smooth muscle; no voluntary

control; responses called visceral reflexes

Sympathetic division of ANS

stimulates and prepares body for action (flight or fight)

Parasympathetic division of ANS

has a calming effect on body

Enteric plexus

within digestive tract wall,

enables coordination and communication within the digestive tract

tract

bundle of axons in CNS

nerve

A bundle of axons in PNS

nucleus

A cluster of neuronal cell bodies in CNS

ganglion

A cluster of neuronal cell bodies in PNS

Properties that allow neurons to communicate with other cells

Excitability, Conductivity, and Secretion

1. Excitability – ability to respond to stimuli

2. Conductivity – produce electrical signals that are

conducted to other cells

3. Secretion – when signal reaches end of the neuron’s

axon, the neuron secretes a neurotransmitter that signals

the next cell

Interneurons

receive signals from other neurons,

process this information, and make resulting “decisions”

Lies entirely within CNS, about 90% of all neurons

Na+/K+ pump

The Na+/K+ pump uses ATP energy to move 3 Na+ out and

2 K+ in, concentrating Na+ outside and K+ inside

Depolarization

is excitatory – makes a neuron more likely to fire an

action potential

Hyperpolarization

(membrane more negative) is inhibitory –

makes a neuron less likely to produce an action potential

Action potential

rapid up-and-down change in voltage

produced by the coordinated opening and closing of

voltage-gated ion channels

All or none

if threshold reached (-55 mV), neuron

fires up/depolarizes to the maximum voltage (+35 mV); if

threshold not reached, it does not fire an action potential

Non decremental

do not get weaker with distance. The

action potential is “regenerated” as it travels along the

axon

Irreversible

once started, an action potential travels all

the way down the axon and cannot be stopped by normal

means

Absolute refractory period

no stimulus of any strength will trigger another AP

• Caused by inactivation of voltage-gated Na+ channels – the

inactivation gate is insensitive to a change in membrane potential

Relative refractory period

an unusually strong

stimulus is needed to trigger a new AP

saltatory conduction/propagation

Action potentials seem to jump from node to node, move faster through myelinated regions, slows down when it reaches bare axon of nodes

two factors influencing nerve signal speed

diameter (wider axons have more surface area for faster conduction) and presence of absence of myelin (myelin speeds conduction)

Type A fiber

Myelinated, large diameter axons, FAST carries info to CNS quickly at 120 m/s

Type B fibers

Myelinated, medium diameter axons

• Carries intermediate info the CNS

• Ex: sensory info from viscera, motor output to peripheral

effectors

• Medium speed (18 m/sec)

Type C fibers

Unmyelinated, small diameter axons

• Carries slow info the CNS

• Ex: CNS output to involuntary muscles, glands

• Slow speed (1 m/sec)

Dendrites

most numerous neurites, resemble branching of a tree;

primary sites for receiving signals from other neurons

• Neurons can have one dendrite or thousands of dendrites

Axon

long, cylindrical extension; relatively unbranched

but may give off axon collaterals; specialized for rapid conduction of

nerve signals

Multipolar neuron

one axon and multiple dendrites;

most common type in body, most neurons in CNS

Bipolar neuron

one axon and one dendrite; examples

include olfactory cells, some neurons of retina, sensory

neurons of ear

Unipolar neuron

single process leading away from cell

body, splits into peripheral process and central process

• Both processes comprise the axon; only short receptive endings of

peripheral process are considered dendrites

Anaxonic neuron

many dendrites but no axon; found

in brain, retina, and adrenal gland

Axonal transport

two-way passage of materials along an

axon

Some materials (enzymes, ion channels) made in cell

body must be transported to the axon and terminal

Anterograde transport

movement away from cell body, down

the axon; driven by motor protein kinesin

Retrograde transport

movement up the axon toward the cell

body; driven by motor protein dynein

Rabies virus

bypasses CNS defenses by infecting the CNS through

retrograde transport – the virus is transported back to the CNS from the

infected nerve

Functions of neuroglia

Bind neurons together

• Form supportive tissue framework

• In fetus, guide migrating neurons to their destination

• Cover mature neurons (except at synapses)

• Prevents neurons from touching each other

• Gives precision to conduction pathways

Oligodendrocytes

form myelin sheaths in CNS

Ependymal cells

line internal cavities of brain;

secrete and circulate cerebrospinal fluid (CSF)

Microglia

macrophages; engulf debris, provide

defense against pathogens

Astrocytes

most abundant type; wide variety of

functions

• Provide framework for nervous tissue; extensions (perivascular

feet) contact capillaries and stimulate formation of blood-brain

barrier; adjust blood flow; supply neurons with lactate for energy;

secrete nerve growth factors; influence synaptic signaling;

regulate composition of tissue fluid; form scar tissue when

neurons are damaged, a process called astrocytosis or sclerosis

Schwann cells

envelop axons of PNS,

form myelin sheath, and assist in regeneration of damaged fibers

Satellite cells

surround nerve cell bodies in ganglia of PNS;

provide insulation around cell body and regulate chemical

environment

Brain tumors arise from

Meninges (protective membranes of CNS)

• Metastasis from nonneuronal tumors in other organs

• Glial cells that are mitotically active throughout life

Gliomas

tumors of glial cells; grow rapidly and are highly

malignant

Myelin sheath

spiral layers of insulation around an axon

• Formed by Schwann cells in PNS, oligodendrocytes in

CNS

• Sheath consists of the plasma membrane of these cells, 20%

protein and 80% lipid

Neurilemma

thick outermost coil of myelin, contains Schwann cell nucleus and most of its cytoplasm

Node of Ranvier

gap between segments

internodal segments

myelin covered segments

Initial segment

bare section of axon between the axon

hillock and the first glial cell

Trigger zone

axon hillock and initial segment of axon

• Plays important role in initiating nerve signal (the action potential)

Multiple sclerosis

Oligodendrocytes and myelin sheaths in CNS deteriorate

• Cause: may be autoimmune response that is triggered by a

virus

• Myelin replaced by hardened scar tissue

• Nerve conduction disrupted (double vision, tremors,

numbness, speech defects)

• Onset between 20 and 40 years of age and fatal from 25

to 30 years after diagnosis

Tay Sachs disease

Hereditary disorder seen mainly in infants of Eastern

European Jewish ancestry

• Usually fatal before age 4

• Abnormal accumulation of glycolipid called GM2 in the

myelin sheath

• Normally decomposed by lysosomal enzyme

• Enzyme missing in individuals homozygous for Tay–Sachs allele

• Accumulation of ganglioside disrupts conduction of nerve

signals

• Causes blindness, loss of coordination, dementia

Steps of nerve regeneration

Axon distal to the injury degenerates, macrophages clean

up tissue debris

2. Cell body swells, ER breaks up, and nucleus moves off

center

• Changes due to loss of nerve growth factors from target cell

3. Axon stump sprouts multiple growth processes

4. Schwann cell neurolemma, endoneurium, and basal

lamina form a regeneration tube

• Guides regrowth to original destination

5. Regeneration tube guides the growing axonal sprout back

to original target cells to re-establish their synapses

6. Once contact is re-established with original target, the

neurosoma shrinks and returns to its original appearance

• Nucleus returns to normal shape

• Atrophied muscle fibers regrow

Electric potential

difference in concentration of charged particles between one point and another

• Type of potential energy; measured in volts (V)

• Under some conditions, can produce a current

Current

flow of charged particle from one point to

another

• Example: flashlight battery

Resting membrane potential

charge difference across plasma membrane

• Typically −70 millivolts (mV) in an unstimulated, “resting”

neuron

• Negative value indicates more negatively charged particles on the

inside of the plasma membrane compared to outside

Leak/Passive channels

membrane channels that are always open. These channels are specific for their specific

ions (Ex: the Na+ leak channel only allows for Na+ to pass

through the channel down its concentration gradient)

Gated channels

channels that are normally closed, but can be stimulated to open These channels are also specific for its specific ion

Chemically gated channel

binding of a chemical (Ex: hormone, neurotransmitter, etc.) causes the channel to open. Found on neuron cell body, dendrites

Voltage gated channel

channel opens due to a change in the membrane potential. Found on neuron’s axon, skeletal and cardiac muscle membrane

Mechanically gated channel

channel opens due to physical stress/deformation on the cell’s plasma

membrane. Found on sensory receptors (touch, pressure, vibration)

Closed channel

closed but capable of opening

open channel

open and activated

inactivated channel

ions cannot pass through the channel, but

the channel is not considered “closed” – an “inactivation

gate” blocks the channel

Local potentials

Sensory neurons can be stimulated by chemicals, light, heat, or

mechanical forces. The stimulation triggers local, temporary

change in membrane potential.

• Example: chemical stimulant binds to a receptor on the neuron

• Opens Na+ chemically-gated channels to let Na+ enter the cell

• Influx of positively charged Na+ into the cell raises the membrane

potential (makes it less negative) – the cell depolarizes

local potential

the depolarization spreads from point of Na+ influx and gets diluted by ions and other solutes (like a ripple in a lake)

Synapse

point where an axon terminal meets the next cell

(another neuron, gland cell, muscle cell)

Electrical synapses

direct physical contact

between cells – links the cytoplasm of adjacent cells