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Classes of joints
based on major connective tissue type that binds bones
three types of structural bones
CLASSES OF JOINTS
BASED ON THE DEGREE OF MOTION
NON-MOVABLE; MOST SYNARTHROSIS JOINTS ARE FIBROUS JOINTS
SLIGHTLY MOVEABLE; MOST AMPHIARTHROSIS JOINTS ARE CARTIAGINOUS JOINTS
FREELY MOVEABLE; ALL DIATHROSIS JOINTS ARE SYNOVIAL JOINTS
CHARACTARISTICS OF FIBROUS JOINTS
- UNITED BY FIBROUS CONNECTIVE TISSUE
- HAVE NO JOINT CAVITY
- MOVE LITTLE OR NONE
TYPES OF FIBEROUS JOINTS
Fibrous Joints: Sutures
- Opposing bones interdigitate.
- Periosteum of one bone is continuous with the periosteum of
- the other.
- Sutural ligament: two periostea plus dense, fibrous, connective tissue between.
- In adults may ossify completely: synostosis.
- Fontanels: membranous areas in the suture between bones. Allow change in shape of head during birth and rapid growth of the brain after birth.
- UNITES TWO BONES BY MEANS OF CARTILAGE
- TYPES: SYNCHONDROSES, SYMPHYSIS
- Joined by hyaline cartilage
- Little or no movement
- Some are temporary and are replaced by synostoses
- Some are permanent
- Examples: Epiphyseal plates, sternocostal
- Fibrocartilage uniting two bones
- Slightly movable
- Examples: symphysis pubis, between the manubrium sternum and the body of the sternum, intervertebral discs
- Contain synovial fluid
- Allow considerable movement
- Most joints that unite bones of appendicular skeleton reflecting greater mobility of appendicular skeleton compared to axial
hyaline; provides smooth surface
synovial; encloses articular surfaces
- Fibrous capsule: dense irregular connective tissue, continuous with fibrous layer of the periosteum.
- Portions may thicken to form ligaments.
Synovial membrane and fluid: membrane lines inside of joint capsule except at actual articulation of articular cartilages. Thin, delicate. Sometimes separated from fibrous capsule by areolar C.T. and fat, sometimes merged with fibrous
complex mixture of polysaccharides, proteins, fat and cells.
Nerves in capsule help brain know position of joints
Pockets of synovial membrane and fluid that extend from the joint. Found in areas of friction
Ligaments and tendons
fibrocartilaginous pads in knee
Synovial sacs that surround tendons as they pass near or over bone
Types of synovial joints
occuring around one axis
types of synovial joints
occuring around two axes at right angles to each other
occuring around several axes
Plane or gliding joints
- Uniaxial. some rotation possible but limited by surrounding structures
- Example: intervertebral
- Example: thumb (carpometacarpal pollicis)
- Convex cylinder in one bone; corresponding concavity in the other
- Example: elbow, interphalangeal
- Uniaxial. Rotation around a single axis.
- Cylindrical bony process rotating within a circle of bone and ligament
- Example: articulation between dens of axis and atlas (atlantoaxial), proximal radioulnar, distal radioulnar
- Examples: shoulder and hip joints
- Modified ball-and-socket; articular surfaces are ellipsoid
- Example: atlantooccipital
Types of Movement
- flexion and extension
- plantar and dorsiflexion
- abduction and adduction
Types of Movement
- Pronation and Supination
Standing on toes
foot lifted toward shin
Movement of a limb away from a bodies midline
Movement of a limb toward the midline of the body
Movement of a limb so that it describes a cone
Turning of a structure on its axis
Rotation of the forearm so the palm faces anteriorly
Rotaion of the forearm so palm faces posteriorly
Move a structure superior
moves a structure inferioir
Gliding motion anteriorly
moves structure back to anatomic position or further
- lateral: moving mandable to the right or the left
- medial: return mandable to the midline
movement of the thumb and little finger toward eachother
return to anatomical position
turning the ankle so the plantar surface of foot faces medially
Turning the ankle so the plantar surface of the foot faces laterally
Functions of the Nervous System
- Receiving sensory input. Monitor internal and external stimuli
- Integrating information. Brain and spinal cord process sensory input and initiate responses
- Controlling muscles and glands
- Maintaining homeostasis. Regulate and coordinate physiology
- Establishing and maintaining mental activity. Consciousness, thinking, memory, emotion
- Support and protect neurons
- Support cells of the brain, spinal cord and nerves
- Nourish, protect, and insulate neurons
Neurons or nerve cells
receive stimuli and transmit action potentials
- Cell body or soma
- Dendrites: input
- Axons: output
Neuroglia of the CNS: Astrocytes
- Processes form feet that cover the surfaces of neurons and blood vessels and the pia mater.
- Regulate what substances reach the CNS from the blood (blood-brain barrier).
- Produce chemicals that promote tight junctions to form blood-brain barrier
- Blood-brain barrier: protects neurons from toxic substances, allows the exchange of nutrients and waste products between neurons and blood, prevents fluctuations in the
- composition of the blood from affecting the functions of the brain.
- Regulate extracellular brain fluid composition
Neuroglia of the CNS: Ependymal Cells
- Line brain ventricles and spinal cord central canal.
- Specialized versions of ependymal form choroid plexuses.
- Choroid plexus within certain regions of ventricles. Secrete cerebrospinal fluid.
- Cilia help move fluid thru the cavities of the brain.
Neuroglia of the CNS: Microglia
- specialized macrophages. Respond to inflammation, phagocytize necrotic tissue, microorganisms, and foreign
- substances that invade the CNS
Neuroglia of the CNS: Oligodendrocytes
form myelin sheaths if surrounding axon. Single oligodendrocytes can form myelin sheaths around portions of several axons.
Neuroglia of the PNS
- Schwann cells
- Wrap around portion of only one axon to form myelin sheath.
- Wrap around many times.
- During development, as cells grow around axon, cytoplasm is squeezed out and multiple layers of cell membrane wrap the axon.
- Cell membrane primarily phospholipid
- Myelin protects and insulates axons from one another, speeds transmission, functions in repair of axons.
- Not continuous
- Nodes of Ranvier
- Completion of development of myelin sheaths at 1 yr.
- Degeneration of myelin sheaths occurs in multiple sclerosis and some cases of diabetes mellitus
- rest in invaginations of Schwann cells or oligodendrocytes.
- Not wrapped around the axon.
surround neuron cell bodies in sensory ganglia, provide support and nutrients
Nervous Tissue: Neurons
Neurons or nerve cells have the ability to produce action potentials
Cell body (soma):
cell process; conducts impulses away from cell body; usually only one per neuron
cell process; receive impulses from other neurons; can be many per neuron
Types of Neurons
Action potentials toward CNS
Types of Neurons
Action Potential away from CNS
Types of Neurons
within CNS from one neuron to another
Types of Neurons
Most neurons in CNS; motor neurons
Types of Neurons
Sensory in retina of the eye and nose
Types of Neurons
single process that divides into two branches. Part that extends to the periphery has dendrite-like sensory receptors
Concentration Differences Across the Plasma Membrane
- There is a high concentration of Na+ and Cl- ions outside and high concentration of K+ and proteins on inside.
- There is a steep concentration gradient of Na+
- and K+, but in opposite directions
Permeability Characteristics of the Plasma Membrane
- Cytoplasmic anions can not escape due to size or charge (phosphates, sulfates, small organic acids, proteins, ATP, and RNA)
- Gated ion channels open and close because
- of some sort of stimulus. When they open, they change the permeability of the cell membrane.
- Cells produce electrical signals called action potentials
- Transfer of information from one part of body to another
- Electrical properties result from ionic concentration differences across plasma membrane
- and permeability of membrane
Establishing the Resting Potential
- Potassium ions (K+) have the greatest influence on RMP
- Resting membrane potential (RMP): charge difference across the plasma membrane -70 mV in a resting, unstimulated neuron
- Negative value means there are more negatively charged particles on the inside of the membrane than on the outside
- Na+/K+ pumps out 3 Na+ for every 2 K+ it brings in
- Works continuously to compensate for Na+ and K+ leakage, and requires great deal of ATP
- 70% of the energy requirement of the nervous system Necessitates glucose and oxygen be supplied to nerve tissue (energy needed to create the resting potential)
Changes in Resting Membrane Potential: Na+
- Na+ membrane permeability.
- Change the concentration of Na+ inside or outside the cell, little effect because gates remain closed.
- But open gates (like when ACh attaches to receptors), Na+
- diffuses in, depolarizing the membrane.
- Results from:
- Ligands binding to receptors
- Changes in charge across membrane
- Mechanical stimulation
- Temperature changes
- Spontaneous change in permeability
- Magnitude varies from small to large depending on stimulus strength of frequency
- Spread(are conducted) over the plasma membrane in a decremental fashion: rapidly decrease in magnitude as they spread over the surface of the plasma membrane.
- Can cause generation of action potentials
- When threshold is reached (-55mV), neuron ‘fires’ and produces an action potential
- More and more Na+ channels open in in the trigger zone in a positive feedback cycle creating a rapid rise in membrane voltage
- When rising membrane potential passes 0 mV, Na+
- gates are inactivated
- Begin closing
- When all closed, the voltage peaks around +35 mV
- Membrane now positive on the inside and negative on the outside
- Polarity reversed from RMP - depolarization
- By the time the voltage peaks, the K+
- gates are fully open
- K+ repelled by the positive intracellular fluid now exit the cell
- Their outflow repolarizes the membrane
- Shifts the voltage back to negative numbers returning toward RMP
- K+ gates stay open longer than the Na+
- Slightly more K+ leaves the cell than Na+ entering
- Drops the membrane voltage 1 or 2 mV more negative than the original RMP – negative overshoot – hyperpolarization or afterpotential
- Na+ and K+ switch places across the membrane during an action potential
- An action potential follows an all-or-none law
- If threshold is reached, neuron fires at its maximum voltage
- If threshold is not reached it does not fire
- Nondecremental: do not get weaker with distance
- Irreversible: once started goes to completion and cannot be stopped
- Threshold stimulus: causes a graded potential that is great enough to initiate an action potential.
- Subthreshold stimulus: does not cause a graded potential that is great enough to initiate an action potential.
The Refractory Period
- During an action potential and for a few milliseconds after, it is difficult or impossible to stimulate that region of a neuron to fire again.
- Refractory period: the period of resistance to stimulation
- Two phases of the refractory period
- Absolute refractory period
- No stimulus of any strength will trigger AP
- As long as Na+ gates are open
- From action potential to RMP
- Relative refractory period
- Only especially strong stimulus will trigger new AP
- K+ gates are still open and any affect of incoming Na+ is
- opposed by the outgoing K+
- Refractory period is occurring only at a small patch of the neuron’s membrane at one time
- Other parts of the neuron can be stimulated while the small part is in refractory period
Signal Conduction in Unmyelinated Fibers
- Threshold graded current at trigger zone causes action potential
- Action potential in one site causes action potential at the next location. Cannot go backwards because initial action potential
- site is depolarized yielding one-way conduction of impulse.
Saltatory Conduction Myelinated Fibers
- Saltatory conduction: the nerve signal seems to jump from node to node
- Much faster than conduction in unmyelinated
Speed of Conduction
- Faster in myelinated than in non-myelinated
- In myelinated axons, lipids act as insulation forcing ionic currents to jump from node to node
- In myelinated, speed is affected by thickness of myelin sheath
- Diameter of axons: large-diameter conduct more rapidly
- than small-diameter. Large have greater surface area and more voltage-gated Na+ channels
- A nerve signal can go no further when it reaches the end of the axon
- Triggers the release of a neurotransmitter
- Stimulates a new wave of electrical activity in the next cell across the synapse
- Synapse between two neurons
- 1st neuron in the signal path is the presynaptic neuron
- Releases neurotransmitter
- 2nd neuron is the postsynaptic neuron
- Responds to neurotransmitter
- Presynaptic terminal
- Synaptic cleft
- Postsynaptic membrane
- Neurotransmitters released by action potentials in presynaptic terminal
- Synaptic knob of presynaptic neuron contains synaptic vesicles containing neurotransmitter
- Action potential causes Ca2+ to enter cell that causes neurotransmitter to be released from vesicles
- Diffusion of neurotransmitter across synapse
- Postsynaptic membrane: when ACh binds to receptor, ligand-gated Na+ channels open. If enough Na+ diffuses
- into postsynaptic cell, it fires