Lecture 9 - Reflexes Flashcards
Reflex
Rapid automatic response to a stimuli through the spinal cord (without the involvement of the brain).
Example: blinking, coughing, knee-jerk, salivation, shivering, pain response
Reflex Arc
Neural pathway that mediates in a reflex action.
5 components of a Reflex Arc
- Sensory receptor
- Sensory nerve (afferent neuron)
- Interneuron (synapse)
- Motor nerve (efferent neuron)
- Target organ (muscle or gland)
Sensory receptor
Receives information and generates impulses.
Primary (sensory receptor)
Neuron with the specialized region for stimulus transduction.
Secondary (sensory receptor)
Non-neuronal cell specialized for stimulus transduction, which stimulates neuronal cell through neurotransmitter.
Innate reflexes
Result from the connection of neurons that form during normal development, are genetically determined.
Ex: Withdrawal from pain, blinking and sucking
Acquired reflexes
Rapid and automatic but are learned responses.
Ex: Salivation when smelling food
Somatic reflexes
Control activities of the muscular system
Visceral reflexes
Autonomic involuntary reflexes, control the actions of smooth and cardiac muscles and glands
Spinal reflexes
Control the activities of the muscular system?
Cranial reflexes
Reflexes processed in the brain
Monosynaptic reflexes
Sensory neuron synapses directly with the motor neuron. There is little delay between sensory input and motor output. CONTROL THE MOST RAPID REFLEXES.
Polysynaptic reflexes
At least one interneuron between sensory afferent and motor efferent. Longer delay between stimulus and response.
Length of the delay is proportional to the # if synapses involved.
Can produce far more complicated responses than monosynaptic reflexes as the interneurons can control several muscle groups.
Unconditioned reflexes
Inborn reflex, inherited and are shown from birth onward, and present in all individuals and animals.
Example: withdrawal from pain.
Conditioned reflexes
Not inherited, learn by doing the same act several times
Ex. salivation when smelling food
Muscle spindles
Sensory receptors within the belly of a muscle that primarily detect changes in the length of the muscle. Detect stretch & protect the muscle.
Composed of 3-12 intrafusal muscle fibers.
Muscle spindle receptor
Encapsulated group of specialized (intrafusal) skeletal muscle fibers supplied with BOTH motor and sensory innervation.
Extrafusal fibers
Regular contractile tissue, innervated by alpha-motor neurons, stimulates contraction.
Intrafusal fibers
Sense organs within muscle fibers. Innervated by gamma-motor neurons.
Golgi tendon organ
Senses stretch in tendons - feeds back on alpha-motor neurons
alpha-motor neurons (from brain stem and spinal cord) innervate the ________ fibers.
extrafusal
Gamma-motor neurons (from pons) innervate the _______ fibers. Function to keeping muscle spindles _________ during muscle contraction. Serves as the volume control of muscle fibers.
- intrafusal
- stretched
With increases stretch, afferents from the muscle spindle stimulate _______ neurons to _________.
- alpha-motor
- contract and relieve the stretch
Golgi tendon reflex
Skeletal muscle contraction causes the agonist muscle to simultaneously lengthen and relax.
Reinforcement
facilitation that enhances spinal reflexes
Plantar reflex
causes a downward response (flexion)
Babinski reflex
upward response (extension)
Lower motor neurons
Classically defined as alpha-motor neurons. Originated from brainstem and spinal cord.
Disease: paralysis and/or atrophy. losses of sensory neurons.
Cell bodies and dendrites are in the CNS and whose axons extend to peripheral nerves and synapse on the _________.
extrafusal skeletal muscle fibers
Upper motor neurons
Neurons of the CNS that influence the lower motor neurons.
Disease: inappropriate movement (seizures, circling), exaggerated segmental reflexes such as crossed extensor reflexes.
