11/4 - Peripheral Muscle Receptors and Spinal Cord Reflexes Flashcards
Spinal Nerve Pathway
PERIPHERAL PROCESS >>> DORSAL ROOT >>> DORSAL ROOT GANGLION >>> DORSAL HORN >>> VENTRAL HORN >>> MOTOR NEURON >>> EFFERENT AXON >>> VENTRAL ROOT >>> SPINAL NERVE >>>
ALPHA MOTOR NEURONS
Innervate ____ muscle fibers: _____ portion of muscle
ALPHA MOTOR NEURONS Innervate extrafusal muscle fibers: Regular contractile portion of muscle
ORGANIZATION OF MOTOR NEURONS IN SPINAL CORD
MOTOR NEURONS FORM FUNCTIONAL CLUSTERS IN THE VENTRAL HORN
Motor Neurons are arranged in longitudinal columns.
All the neurons in one column go to the same one muscle.
Each column contains the motor neurons that innervate one muscle.
Column usually extends through more than 1 spinal cord segment.
TOPOGRAPHIC ORGANIZATION:
FLEXORS
DORSAL
TOPOGRAPHIC ORGANIZATION:
EXTENSORS
VENTRAL
TOPOGRAPHIC ORGANIZATION:
DISTAL LIMB Mucles
LATERAL
TOPOGRAPHIC ORGANIZATION:
PROXIMAL LIMB & TRUNK Muscles
MEDIAL
Skeletal muscle is made up of bundles of cylindrical ____ that vary in length from 1-40 mm and in diameter from 50–100 um.
Skeletal muscle is made up of bundles of cylindrical Muscle Fibers that vary in length from 1-40 mm and in diameter from 50–100 um.
Each muscle fiber is a _____ .
Each muscle fiber is a single, multinucleated cell
MOTOR UNIT
Defined as a single alpha motor neuron and ALL THE MUSCLE FIBERS it innervates
Each muscle fiber receives input from a _____ which synapses at the ______.
Each muscle fiber receives input from a single motorneuron which synapses at the single motor end plate.
A ____ may innervate more than one ____ .
A motor axon may innervate more than one muscle fiber.
Motor End-Plate
Site where axons make synaptic contact with muscle fiber.
The size of motor units varies from small (10–100 fibers/motor neuron) to large (600–several thousand fibers/motor neuron).
The size of motor units varies from small (10–100 fibers/motor neuron) to large (600–several thousand fibers/motor neuron).
Small motor units
Small motor units provide more Precise Control of motor activity.
These would be found in
muscles that control individual Digits or muscles that control movements of the Eye.
MUSCLE CONTRACTION
The force of contraction of individual muscle fibers is determined by the firing
frequency of the motor neuron
Total force of contraction of a muscle is determined by number of alpha motor neurons that are active.
The force of contraction of individual muscle fibers is determined by ______ .
The force of contraction of individual muscle fibers is determined by the firing
frequency of the motor neuron
Total force of contraction of a muscle is determined by ______.
Total force of contraction of a muscle is determined by the number of alpha motor
neurons that are active.
Tetany
a sustained muscular contraction caused by a series of stimuli repeated so rapidly that the individual muscular responses are fused.
The maximal force a muscle can generate.
Temporal summation.
TETANUS
- Binds to peripheral nerve terminals and transported within the axon to CNS.
- Binds to proteins at presynaptic inhibitory motor nerve endings and taken up into the neurons.
- Effect is to block release of inhibitory neurotransmitters (GABA, glycine).
- Results in uncontrolled firing of motor neurons resulting in muscular spasms.
- Acts by selective cleavage of a protein required for neurotransmitter release, synaptobrevin II
Clostridium tetani
A grampositive rod-shaped bacterium that is found worldwide in soil.
It is usually in its dormant form, spores, and becomes the rod-shaped bacterium when it multiplies.
AFFERENT SIDE OF SPINAL LOOP:
PROPRIOCEPTORS
Proprioceptors within the muscle that continually provide information about the Current State of muscle Contraction and Rate of Change in muscle length and tension.
