KIN 310 6: nervous system

msu

Central Nervous System

Planning of voluntary movement. Responding to feedback.

Peripheral Nervous System

Motor (efferent) control of movement and organ system. Sensory (afferent) feedback during exercise.

Membrane potential depolarizes from ___ mV to ___ mV

-70, +30

Membrane potential repolarizes from ___ mV to ___ mV

+30, -70

Direction of Neuron to Neuron Communication

Presynaptic Neuron: Dendrites→Axon→Synapse→Postsynaptic Neuron: Dendrite→Axon→repeat

Communication between neurons occur at a ____

synapse

Presynaptic neuron _____ to postsynaptic ____.

end foot, dendrite

Synaptic Cleft

space in between neurons

Presynaptic neuron releases neurotransmitters that…

bind to receptor on postsynaptic neuron

Excitatory transmitters

Bind to receptor on target membrane and elicit graded depolarizations (excitatory postsynaptic potentials)

• Binding of neurotransmitters to receptors opens Na+ channels

• With sufficient neurotransmitters, depolarization to threshold is accomplished and an AP is generated

Excitatory postsynaptic potentials (EPSPs) can bring to threshold 2 ways:

1. Temporal summation

2. Spatial summation

Temporal Summation

EPSPs from single neuron

Spatial Summation

EPSPs from multiple neurons

Inhibitory transmitters

Bind to receptor on target membrane and elicit inhibitory postsynaptic potentials (IPSPs)

• Binding of neurotransmitter to receptors opens K+ or Cl- channels

• Movement of ions hyperpolarizes cells, resists depolarization

Final details on synaptic transmission

Common neurotransmitter = acetylcholine (ACh)

Neurotransmitter are broken down

• Prevents chronic depolarization

• Acetylcholine→acetyl and choline by acetylcholinesterase

Somatic Sensory Division of PNS

• Transmission of sensory information from receptors to CNS

• Afferent fibers

• Focus - sensory information and reflexes (relevant to exercise)

  • Reflexes refer to involuntary muscle movements

Proprioceptors

Located in joints and muscles

Joint Proprioceptors

Provide information about orientation of body parts and rates of limb movement

• Free nerve endings (most abundant)

• Golgi type receptors

• Pacinian corpuscles

Muscle Proprioceptors

Sensitive to changes in muscle length and tension

• Muscle spindles

• Golgi tendon organs

Muscle Spindle

Responds to changes in muscle length

Stretch reflex: stretch on muscle causes reflex contraction, ex. knee-jerk reflex

Muscle Spindles contains of:

• Intrafusal fibers that run parallel to normal muscle fibers (extrafusal fibers)

• Two sensory nerve endings: primary responds to dynamic changes, secondary provide continuous information about static muscle length

• Gamma motor neurons stimulate intrafusal fibers to contract with extrafusal fibers

Golgi Tendon Organ (GTO)

Located within tendon; in series with extrafusal fibers

• Monitors tension developed in muscle: prevents muscle damage during excessive force generation

• Stimulation results in reflex relaxation of muscle