Nervous and Muscle

Nervous system functions

Sensory input - monitoring stimuli
Integration - interpretation of sensory input
Motor output - response to stimuli

CNS

brain and spinal cord

PNS

cranial nerves and spinal nerves

PNS sensory (afferent) division

Nerve fibers that carry information to the central nervous system

PNS: motor (efferent) division

Nerve fibers that carry impulses away from the central nervous system

Somatic nervous system (motor)

voluntary, skeletal muscle

Autonomic nervous system (motor)

involuntary, cardiac and smooth muscle + glands

neuron characteristics

-Extreme Longevity
-Conduct messages
-Amitotic
-High metabolic rate: require continuous O2 and glucose
-Neuron death occurs within minutes without O2

Astrocytes

Form barrier between capillaries and neurons
. Control the chemical environment of the brain

Microglia

Act as phagocytes, eating damaged cells and bacteria, act as the brains immune system

ependymal cells

produce cerebrospinal fluid

Oligodendrocytes

branched cells that wrap CNS nerve fibers

Schwann cells

surround fibers of the PNS

Satellite cells

surround neuron cell bodies with ganglia

path of a nerve impulse

dendrite, cell body, axon

Step 1 of muscle contraction

A nerve impulse travels to the neuromuscular junction on a muscle cell. The neuromuscular junction is the point where the axons of the nerve meet with the muscle cell.

Step 2 of muscle contraction

Ach is released from the axon to receptors located on the sarcolemma

Step 3 of muscle contraction

The binding Ach causes depolarization of the sarcolemma by opening ion channels and allowing Na+ ions into the muscle cell.

Step 4 of muscle contraction

Na+ ions diffuse into the muscle fiber and depolarization occurs.

Step 5 of muscle contraction

Depolarization creates a wave of action potential (electrical current) across the sarcolemma

Step 6 of muscle contraction

Action potential travels across the sarcolemma and down the T-tubules which triggers the sarcoplasmic reticulum SR to release Ca+

Step 7 of muscle contraction

As Ca+ levels rise, Ca+ ions bind with Troponin which removes the blocking action of Tropomyosin from the Actin binding sites.

Step 8 of muscle contraction

Myosin is now ready to bind with the actin and form cross bridges which begins the contraction process

Step 9 of muscle contraction

In order to contract, ATP binds to the Myosin

Step 10 of muscle contraction

ATP is then hydrolyzed (broken down) to ADP and Pi, which gives the myosin the energy to "cock" its head to the high-energy position.

Step 11 of muscle contraction

Actin and myosin bind together to form a cross bridge

step 12 of muscle contraction

The myosin heads then pull the actin filaments inward and release the ADP and Pi and return to a low energy position.

Polarization - action potential

Resting state

threshold

the level of stimulation required to trigger a neural impulse

Depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

Repolarization

Return of the cell to resting state, caused by reentry of potassium into the cell while sodium exits the cell.

Hyperpolarization

The movement of the membrane potential of a cell away from rest potential in a more negative direction (temporary)

Reflex arc

direct route from a sensory neuron, to an interneuron, to an effector

Step 1 of reflex arc

arrival of stimulus and activation of receptor

Step 2 of reflex arc

activation of a sensory neuron

Step 3 of reflex arc

information processing in CNS

Step 4 of reflex arc

activation of a motor neuron

Step 5 of reflex arc

response by effector