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Exam 3
Muscles, Central and Peripheral Nervous system, and Signal conduction along nerves
112
Anatomy
Undergraduate 1
03/16/2010

Additional Anatomy Flashcards

 


 

Cards

Term
Types of Muscle 
Definition

Smooth

Cardiac

Skeletal 

Term
Epimysium
Definition
Covering that surrounds whole muscle; made of irregular CT
Term
Fasicle
Definition

A group of muscle fibers.

( skeletal muscle contains multiple)

Term
Perimysium 
Definition
covering around fasicle 
Term
Muscle Fiber/ Muscle Cells
Definition

  • long, cylindrical, multinucleate
  • plasma membrane of muscle       fibers is called the sarcolemma.

Term
Endomysium
Definition
connective tissue that surrounds each muscle fiber. 
Term
nerve and blood supply 
Definition

Each muscle has a nerve, an artery, one or more veins. These exit and enter near the central part of the muscle and branch profusely through CT sheaths 

Term
Myofibrils
Definition

  • Contractile element of muscle cell
  • Each muscle fiber contains 100's-1000 of myofibrils
  • Run parallel and fill entire cell (80% of cell vol)

 

Term
Myofibril Anatomy
Definition

Skeletal muscle is striated because of actin + myosin fibers of the myofibril. These striations are made from repeating series of dark A bands and light I band. 

Term
H-zone
Definition
Lighter stripe in middle of A band (relaxed muscles only)
Term
M- line
Definition
Bisects H-zone and A-band
Term
Z-disc
Definition
Bisects I-band 
Term
Sacromere
Definition

  • region between Z-discs
  • Is functional contractile unit
  • Sacromere units end to end are what form myobrils 

Term
Myofilaments
Definition

Fibers within the Sacromere

  • Thick filaments (myosin)
  • Thin filaments (actin)

Term
Thick Filaments
Definition
Form length of  A-band
Term
Thin Filaments 
Definition
Form I-band and extend to A-band
Term
Nebulin
Definition

  • Protein that forms Z-discs
  • Anchor thin filaments
  • Connect adjacent myofibrils

Term
Desmin
Definition

Fine protein  strands that form M-line.

Hold adjacent thick filaments together.

Term
Elastic Filaments
Definition

  • composed of giant protein, titin
  • Runs from the Z disc to myosin and on the M line
  • Holds thick filaments in place
  • Extensible when muscle stretching
  • Recoils when returns to original length

Term
Myosin
Definition

The protein that makes up the thick filaments.

Head- ends of heavy chains and 2 light polypeptide chains. Links thick and thin filaments together during contraction.

Tail- 2 twisted heavy polypeptide chains

Term
Thick Filament Structure
Definition

  • Myosin tails bundle together 
  • Myosin heads poke outwards
  • Myosin heads in contact with thin filaments
  • Binding site for actin for ATP

Term
Thin Filament Structure
Definition

  • Subunit is globular actin (G)
  • Attached in a long polypeptide chain (F actin)
  • F actin folds back on itself to make a twisted double strand
  • Stiffened by 2 strands of tropomyosin
  • In a relaxed  muscle tropomyosin blocks active sites of actin

 

Term
Troponin
Definition

3 polypeptide complex
TnI-bonds actin
TnT- binds to tropomyosin and positions it on actin
TnC- binds calcium ions
Shape determines position 
Position determines ability of muscle to contract

Term
Sarcoplasmic Reticulum 
Definition

Is the ER of muscle cells

Surrounds each myofibril

Network of tubules

A-I junction tubules thicker

-terminal Cisternae

Between Term. Cis are T- tubules

Term
T-tubule
Definition

  • Formed from SR
  • Are tubes that wrap around each myofibril
  • Lumen is continuous with extra cellular space
  • Conduct nerve impulses deep inside muscle cells 

Term
Sliding Filament Theory
Definition

During contraction the Actin/Myosin overlap increases.

When stretched  the Actin/Myosin overlap is minimal.

Term
Rigor Mortis
Definition

  • Muscles are contracted
  • Cell death decreases ATP supply ATP synthesis stops
  • Ca2+ influx into cell is "unstoppable" 
  • ATP is necessary for cross bridges detachment
  • Without ATP muscles stay contracted (peaks at 12 hours)
  • Rigor Mortis disappears as muscle proteins begin to breakdown.

Term

Functions of CNS and PNS

 

Definition

  • Gather sensory info both interal and external
  • Process info, filter, and interpret info
  • Produce a response: voluntary or involuntary

Term

Central Nervous System

(CNS)

Definition
Brain and spinal cord
Term

Peripheral Nervous System

(PNS)

Definition

Nerves not located in the CNS

hotlines to and from the CNS

spinal nerves

cranial nerves 

Term

Afferent

(sensory)

Definition

Nerves send impulses to CNS

-Somatic Afferent Fibers: skin, muscles and joints

-Visceral Afferent Fibers: Organs in the visceral body cavity

Term

Efferent

(Motor)

Definition

Nerves carry out impulses from CNS

-Somatic Nerves: voluntary

-Autonomic Nerves: involuntary 

Sympathetic -fight or flight

Parasympathetic - rest or digest 

 

Term

Nerve Cells

(neurons)

Definition

Information messengers

Most diverse kind of cells in body.

Excitable- transmit an electrical current. 

Term

Supporting Cells

(neuroglia)

Definition

Out number neurons by up to 9:1

Cells are densely packed-> little extra cellular space

Term
Astrocyte
Definition

Most abundant of glial cells

out number neurons by about ten to one

Help form a network on which neurons grow 

Anchor neurons to capillaries 

mop up 'leaked' NT's 

Term
Microglia
Definition

Protective role 

Sense microbes and debris

Transform into macrophages and phagocytes debris 

Term
Ependymal Cells
Definition

Line cavities of brain and spinal cord

Are ciliated- to circulate CSF

Term
Oligodendrocytes 
Definition

Wrap their branches around large nerve fibers.

Insulating cover or myelin sheath- for up to 60 axons 

 

Term
Satellite Cells
Definition

-Function unknown

-Surround neuron cell bodies in ganglia

Term
Schwann Cells
Definition

-Wrap around large nerves

-myelin sheath 

Term
Neurons
Definition

-Are~ 100 billion neurons in the CNS

-Specialized to conduct electrical impulses

-Normally 80 times per second

-In epilepsy can fire up to 500 times per second

-Longevity (>100)

-Amitotic- do not divide. Neurogenesis has been shown in other mammels but remains unproven in humans. 

-Very high metabolic rate; need constant supply of glucose and oxygen


Term
Cell Body
Definition

-Contains usual organelles

-nucleus, ribosomes, ER, golgi, mitto.

-Neurofibrils- maintain cell shape and integrity 

 

Term
Nuclei
Definition
Cluster of cell bodies (CNS)
Term
Ganglia
Definition
Cluster of cell bodies (PNS)
Term
Dendrites
Definition

-Branching extensions of cell body 

- also contain cytoplasm and organelles

- Provide increase in surface area for input signals

-Some are "thorny"- dendritic spines

-transmit incoming information to axon hillock by graded depolarizations.

 

Term
Axon
Definition

-one per neuron

-Is a projection of cell body

-Arises from axon hillock

-Short or long (nerve fiber)

-Can branch

-Usually has terminal branches ~10,000

-Are conduction component of neurons.

-Terminals are secretory component

-Contains organelles, but no ER or golgi

-Therefore axon relies on cell body for protein synthesis 

-Axons decay quickly when damaged

-Plasma membrane of axon- axolemma

-Constant 2 way traffic along axon

Term
Anterograde
Definition

-Cell body to terminal

-Mitochondria 

-Replacement molecules for axolemma, NT synthesis

-Transported by the protein kinesin

 

 

Term
Retrograde
Definition

-Terminal to cell body

- Molecules and organelles for degradation and recycling

-Transported by the protein dynein

 

Term
Myelin Sheath
Definition

-Large, long axons are covered in Myelin (fatty protein) electrically insulates axons

-Increases transmission of nerve impulses along axon.

-150x faster then unmyelinated axons

-Formed by schwann cells

-Cells wrap themselves around axon many times

-Tight coil of wrapped membranes

-A gap is left between adjacent Schwann cells called a Node of Ranvier. Therefore axon is exposed at node

Term
Multipolar
Definition

- 99% of neurons

-Numerous dendrites

- 3 or more cell processes 

Term
Bipolar
Definition

-Have 2 processes (axon and dendrite)

- Rare. Found in sense organs

- Retina of eye, olfactory mucosa 

Term
Unipolar
Definition

-1 process emerges from cell body

- most are sensory neurons in the PNS

Term
Nerve Impulses
Definition

-Electrical currents that travel through neurons

Term
Graded Response
Definition

-Short lived, local change in membrane potential (depolarization). This change causes current to flow that decreases in strength with distance. Found in dendrites and cell body. 

Term
Action Potential
Definition

A large, short depolarization event that does not decrease in strength with distance. They occur only in Axons, Sarcolemma and T-tubule.

Term
Polarized state
Definition

- Inside cell is more negative than outside.

 

 

Term
Depolarization
Definition

Change in resting membrane potential such that the inside now becomes more positive than it was when at rest.

Term
The formation of a cross bridge occurs when?
Definition

Myosin head attaches to its binding site on actin.

Term

    Which of the following occur during contraction of a muscle?

Definition
The thin filaments move towards the center of the sarcomere        
Term
What is the trigger for a muscle contraction? 
Definition
The binding of calcium to troponin         
Term

1.     In the sliding filament theory, what event is triggered by attachment of ATP to its binding site on the myosin head?

Definition
Cross-bridge detachment      
Term
Energy from the breakdown of ATP to ADP + Pi is stored in the myosin head for what purpose? 
Definition
Prepares myosin head for next attachment     
Term

    Which of the following molecules triggers relaxation of the muscle?

Definition
ATP 
Term
Which of the following contributes to the condition of Rigor Mortis 
Definition

  1. Cell death decreases the energy supply to the cell
  2. Cellular calcium concentrations are unregulated 
  3. Cross-bridge detachment has stopped

Term

Which of the following applies to polarized membranes? 

Definition
There is a voltage difference across the membrane     
Term

     Why are plasma membranes polarized?

Definition
Because of the pumping of unequal numbers of ions across the membrane 
Term

     Which ions play a major role in the formation of a polarized state?

Definition
. Sodium and potassium 
Term

    What is a depolarization?

Definition

  1. A change in the Resting Membrane Potential
  2. A decrease in the voltage difference across the membrane
  3. A change in the distribution of ions across the membrane

Term

    Which of the following are components of the Neuromuscular Junction?

Definition

  1. A nerve terminal
  2. A synaptic cleft
  3. A motor end plate

Term

   Which neurotransmitter is released at the Neuromuscular Junction?

Definition
Acetylcholine   
Term
Signal Conduction along Nerves
Definition
  • Info is carried by nerves in the form of electrical current
  • 2 forms of electrical signals: graded response, action potential
Term

   What happens immediately after a nerve impulse, traveling down a motor neuron, reaches the nerve terminal?

Definition
Ca2+ channels open and allow Ca2+ into the nerve terminal              
Term
Graded Response
Definition
  • occur at sensory receptor endings and dendrites
  • produced by a stimulus e.g. light in cells of retina sound waves in receptive cells in ears
  • are short lived, local changes in RPM
  • cause electrical current flow that DECREASES with distance i.e. it dies out as it travels
  • magnitude of change in membrane potential is related to magnitude of stimulus
Term

     What happens after acetylcholine is released into the synaptic cleft by exocytosis?

Definition
It binds to, and activates, acetylcholine receptors             
Term

    What is the function of acetycholinesterase?

 

Definition

It breaks down acetycholine 

Term

What is believed to be the cause of Myasthenia Gravis?

Definition

  1. Too few Ach receptors on the postsynaptic membrane
  2. The destruction of Ach receptors by antibodies
  3. A lack of muscle stimulation by Ach receptors

Term
What is the mechanism of action of the toxin produced by Clostridium Botulinum? 
Definition
Blocks Ach release from the nerve terminal      
Term
Mechanism
Definition
  • small region of membrane becomes depolarized
  • at point of stimulus inside cell has the charge
  • positive charge will flow laterally
  • outside cell positive charges flow to less positive regon created by depolarizaion
  • the greater the initial depolarization the greater the currents
  • as positive charges move laterallythe membrane becomes depolarized
  • this effect becomes weaker + weaker the further the current travels from site of initial stimulus
Term

     What is the shape of smooth muscle cells?

Definition
They are spindle shaped          
Term
How are smooth muscles arranged in a hollow organ? 
Definition

A.    In two separate sheets

B.    A longitudinal sheet of cells

C.    A circular sheet of cells

Term

 In which of the following is contraction of smooth muscle a contributing cause?

Definition

A.    Peristalsis

B.    Asthma

C.    Stomach cramps

Term

     Which of the following is true regarding smooth muscle cells?

Definition
They store Ca2+ in membrane pouches         
Term

   Which of the following make up the Central Nervous System (CNS)?

Definition
The brain and spinal cord           
Term

  What is the function of afferent nerves?

Definition
To send impulses to the CNS            
Term

 What are Neuroglia?

Definition
They are supporting cells in both the CNS and PNS         
Term
Action Potential
Definition
  • generated by excitable tissue
  • i.e. nerves + muscle cell
  • brief reversals of membrane potential
  • change in amplitude is by about 1000 mv
  • takes about 3 ms
  • is an all-none-event
  • voltage change travels along axon/sarcolemma/t-tubules
  • in a neuron the traveling voltage change is called a nerve impulse
Term

    Which of the following neuroglia is the most abundant in the CNS?

Definition
Astrocytes 
Term

Which of the following statements about neurons is FALSE?

Definition
They have a low metabolic rate             
Term

     What is the function of dendrites?

Definition

A.    To provide an increase in the surface area of the cell body

B.    To receive input signals

C.    To transmit graded depolarizations to the axon hillock

Term

What types of molecules might flow in an Anterograde direction along the axon?

Definition
Replacement proteins for the axolemma             
Term

    What type of neurons are the sensory neurons of the PNS?

Definition
Unipolar  
Term

     Which of the following are not properties of a GRADED response (depolarization)?

Definition
A threshold level of stimulus must be reached to produce a depolarization                 
Term

    Which of the following are not properties of an action potential?

 

Definition

The size of an action potential is determined by the size of the stimulus              

Term

    What happens during the Repolarization phase?

Definition
The neuron is refractory                   
Term

     What event leads to repolarization of the membrane?

Definition
The opening of potassium channels                    
Term

 What restores the ionic distribution (i.e. Na+/K+ ratio) across the resting membrane?

Definition
An increase in activity of the Na+/K+ pump         
Term

   In which of the following nerves is impulse conduction fast?

Definition
Large diameter, myelinated Group A fibers              
Term

 Where, in myelinated nerves, do action potentials occur?

Definition
At the Nodes of Ranvier only             
Term

     Which of the following applies to Multiple sclerosis?

Definition

A.    It is an autoimmune disease

B.    The immune system makes antibodies against myelin

C.    The myelin sheath is slowly destroyed

Term

  Which of the following applies to multiple sclerosis?

Definition
Muscular weakness and paralysis        
Term

     Which of the following are true for the neuromuscular junction but not for the nerve synapse?

Definition
The receptor region is a motor-end -plate                   
Term

   What is a function of a synapse?

Definition
To convert an electrical signal into a chemical signal  then back into an electrical signal         
Term

  What is the function of the Axon Hillock?

Definition

A.    To receive graded responses from dendrites

B.    To initiate the firing of action potentials

C.    To initiate formation of the axon 

Term

     Which of the following statements regarding all the synapses of the nervous system is true?

Definition
Some are excitatory and some are inhibitory          
Term

 What type of depolarizations occurs at the postsynaptic membrane?

Definition
Graded depolarizations 
Term

What is a hyperpolarization?

Definition
It is when the membrane potential becomes more negative than the Resting Membrane Potential 
Term

     What type of effect do hyperpolarizations have on a membrane?

Definition
It makes it harder to fire the next depolarization     
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