Smooth

Cardiac

Skeletal 

A group of muscle fibers.

( skeletal muscle contains multiple)

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

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 

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

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. 

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

Fibers within the Sacromere

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

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

Fine protein  strands that form M-line.

Hold adjacent thick filaments together.

• 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

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

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

• 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

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

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

During contraction the Actin/Myosin overlap increases.

When stretched  the Actin/Myosin overlap is minimal.

• 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.

Functions of CNS and PNS

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

Central Nervous System

(CNS)

Peripheral Nervous System

(PNS)

Nerves not located in the CNS

hotlines to and from the CNS

spinal nerves

cranial nerves 

Afferent

(sensory)

Nerves send impulses to CNS

-Somatic Afferent Fibers: skin, muscles and joints

-Visceral Afferent Fibers: Organs in the visceral body cavity

Efferent

(Motor)

Nerves carry out impulses from CNS

-Somatic Nerves: voluntary

-Autonomic Nerves: involuntary 

Sympathetic -fight or flight

Parasympathetic - rest or digest 

Nerve Cells

(neurons)

Information messengers

Most diverse kind of cells in body.

Excitable- transmit an electrical current. 

Supporting Cells

(neuroglia)

Out number neurons by up to 9:1

Cells are densely packed-> little extra cellular space

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 

Protective role 

Sense microbes and debris

Transform into macrophages and phagocytes debris 

Line cavities of brain and spinal cord

Are ciliated- to circulate CSF

Wrap their branches around large nerve fibers.

Insulating cover or myelin sheath- for up to 60 axons 

-Function unknown

-Surround neuron cell bodies in ganglia

-Wrap around large nerves

-myelin sheath 

-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

-Contains usual organelles

-nucleus, ribosomes, ER, golgi, mitto.

-Neurofibrils- maintain cell shape and integrity 

-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.

-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

-Cell body to terminal

-Mitochondria 

-Replacement molecules for axolemma, NT synthesis

-Transported by the protein kinesin

-Terminal to cell body

- Molecules and organelles for degradation and recycling

-Transported by the protein dynein

-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

- 99% of neurons

-Numerous dendrites

- 3 or more cell processes 

-Have 2 processes (axon and dendrite)

- Rare. Found in sense organs

- Retina of eye, olfactory mucosa 

-1 process emerges from cell body

- most are sensory neurons in the PNS

-Electrical currents that travel through neurons

-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. 

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

- Inside cell is more negative than outside.

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

Myosin head attaches to its binding site on actin.

    Which of the following occur during contraction of a muscle?

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

    Which of the following molecules triggers relaxation of the muscle?

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

     Why are plasma membranes polarized?

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

    What is a depolarization?

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

    Which of the following are components of the Neuromuscular Junction?

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

   Which neurotransmitter is released at the Neuromuscular Junction?

• Info is carried by nerves in the form of electrical current
• 2 forms of electrical signals: graded response, action potential

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

• 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

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

    What is the function of acetycholinesterase?

It breaks down acetycholine 

What is believed to be the cause of Myasthenia Gravis?

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

• 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

     What is the shape of smooth muscle cells?

A.    In two separate sheets

B.    A longitudinal sheet of cells

C.    A circular sheet of cells

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

A.    Peristalsis

B.    Asthma

C.    Stomach cramps

     Which of the following is true regarding smooth muscle cells?

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

  What is the function of afferent nerves?

 What are Neuroglia?

• 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

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

Which of the following statements about neurons is FALSE?

     What is the function of dendrites?

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

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

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

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

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

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

    What happens during the Repolarization phase?

     What event leads to repolarization of the membrane?

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

   In which of the following nerves is impulse conduction fast?

 Where, in myelinated nerves, do action potentials occur?

     Which of the following applies to Multiple sclerosis?

A.    It is an autoimmune disease

B.    The immune system makes antibodies against myelin

C.    The myelin sheath is slowly destroyed

  Which of the following applies to multiple sclerosis?

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

   What is a function of a synapse?

  What is the function of the Axon Hillock?

A.    To receive graded responses from dendrites

B.    To initiate the firing of action potentials

C.    To initiate formation of the axon 

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

 What type of depolarizations occurs at the postsynaptic membrane?

What is a hyperpolarization?

     What type of effect do hyperpolarizations have on a membrane?