exam 3

100 billion neurons; trillions of synaptic connections

How many neurons make up how many synaptic connections

Depolarizing

Rising phase of neuronal action potential

Repolarizing

Falling phase of neuronal action potential

Neuromuscular junction

Junction between terminal branch of nerve fiber and muscle fiber

Precentral gyrus

Where is the primary motor cortex located?

Primary motor cortex motor Homunculus

Shows relative number of motor neurons devoted to different body muscles

Large Betz cells

Upper motor neurons in primary motor cortex that send long tons down towards the spinal cord

Basal ganglia motor loop

Helps select and and initiate movement

Huntington's Disease

Caudate lesion leads to

Huntington's Disease

Too much movement

Parkinson's

Substantia Nigra lesion

Parkinson's

Too little movement; jerky movement

Cerebellum

Coordinates muscle movement

Compares intended movement coming from the motor cortex with a actual movement sensation coming from the joints and muscles and makes corrections based on past experiences

How does the cerebellum coordinate movement?

Primary motor cortex

Whee does voluntary movement originate?

Synapse onto alpha motor neurons

Motor cortex axon pathway

In ventral horn of spinal cord

Where do alpha motor neurons synapse?

Muscle contraction

Action potentials in alpha motor neurons leads to what?

Motor unit

Motor neuron and all the muscle cells it innervates

Amyotrophic lateral sclerosis (ALS)

Loss of motor neurons causes what?

Motor neurons degenerate/die, which leads to muscle atrophy

What happens to muscle neurons in ALS?

Upper extremities

Spinal cord cervical enlargement affects

Lower extremities

Spinal cord lumbar enlargement affects

Spinal cord level

Simple reflex skeletal muscle movement is mediated at...

Reflex

Occurs without conscious intent for upper motor neuron

5. Effector organ (Muscle)

Reflex are of skeletal muscles

Tendon/muscle damage

Week/Absent reflexes could be a result of...

Hyperflexia

Too much reflex

Right side

Damage to the left side of brain will effect what side of the body?

Below site of spinal cord damage

An exaggerated reflex may occur where?

Cardiac Muscle

Three types of muscle tissue

precentral gyrus/motor cortex

Skeletal muscle characteristics

involuntary

no striations

surrounds internal organs

Smooth muscle characteristics

Heart

involuntary

striations

(mix between skeletal and smooth muscle)

Cardiac muscle characteristics

Skeletal muscles

help us move by having the ability to contract/shorter cell length

tendons

muscles are connected to bones via what?

myofibers

bundles of long multinucleate cells

myofibrils

extensive network of intracellular filament proteins

Actin and myosin

Myofibrils are composed primarily of what?

Intracellular protein filaments

Actin and myosin are considered what?

Sarcomeres

Shortening of what causes movement (within muscle)?

Actin

thin filament

Myosin

Thick filament

Sarcoplasmic reticulum

Endoplasmic reticulum within a muscle

Origin

Connection to stationary bone

Insertion

Connection to moveable bone

Antagonistic pairs

Skeletal muscles often work in...

Flexion

Bicep contraction causes...

Extension

Tricep contaction causes...

Isotonic muscle contractions

Result in muscle shortening

Lifting a barbell

Example of Isotonic muscle contraction action

Isometric Contractions

Create tension without muscle shortening

Load is too heavy

Sarcomere still shortens, but tendons lengthen, too

No net muscle shortening

No movement

Isometric characteristics

Acetylcholine (ACh)

What do Alpha motor neurons release onto target muscle in skeletal muscles?

Nicotinic ACh Receptor

What does ACh bind to in skeletal muscle?

Neuromuscular junction

Illustrates the precise alignment of presynaptic active zones with postsynaptic each receptors

Ligand gated ion channel

Nicotinic acetylcholine receptor is what kind of ion channel?

Curare

Plant toxin used by South American tribes to make poison arrows

Inhibits nACh receptor and stops NMJ signaling to paralyze prey

What does curare do?

Because it is too large and highly charged

Why doesn't curare pass through he digestive tract?

Auto-antibodies to the nACh

What is Myasthenia Gravis caused by?

Fatigue

Ptosis

What are the hallmark symptoms of Myasthenia Gravis?

Auto-immune disease

Myasthenia Gravis is what kind of disease?

Botox

Muscle relaxant

Clostridium botulinum

Botulinum is a neurotoxin protein produced by the bacterium...

Inhibits SNARE protein exocytosis machinery and ACh release (muscles then do not receive signal to contract--> muscles relaxed)

What does botulinum do?

Contractile proteins arranged in a series of row

Skeletal muscles are full of what?

Sarcomeres

Muscle fiber filaments are arranged into this

Actin

Myosin

Sarcomere muscle contractile unit is composed of what?

Actin

Scaffold for myosin

Myosin

Ratchet protein that binds/pushes actin

Tropomyosin

Covers actin binding sites during rest

Troponin

Binds Ca2+ and moves tropomyosin to allow myosin to bind actin

Repetitive structured sarcomeres

What gives skeletal muscles a striated look?

Cross-bridges

If allows, myosin forms what with actin?

Extracellularly

Calcium concentration is greater in the cytosol or extraceullarly?

Calcium ATPase

Pumps Ca2+ out of the cell

Circa

Pumps Ca2+ into the ER

Voltage-gated DHP Ryanodine Receptor

Mediate Ca2+ release from sarcoplasmic reticulum

Troponin

After Ca2+ is released from the SR, what does it bind to?

ATP

What is required to release myosin head from actin?

Rigor mortis

If no ATP is present and myosin head is stuck onto actin, this occurs

Mitochondria

Produces ATP for the cell

In cells with high energy demand

Where is there the most mitochondria?

Contraction of voluntary skeletal muscles

What allow the body to move?

-CA2+ reuptake into the SR

-Acetylcholinestrase breaks down ACh (into acetate and choline)

-Stop action potential

Three ways to get muscle to relax

-Myosin release from actin