Week 2 midterm 2 Flashcards
What is a reflex arc?
neural pathways for reflexes
What is the muscle spindle stretch reflex?
the reflex pathway in which muscle stretch initiates a contraction response
What are the 5 neural pathways of a reflex arc?
- stimulus*
1. sensor receptor
2. afferent neuron
3. integration center
4. efferent neuron
5. effector organ - response*
Spinal reflexes require what?
require NO input from the brain
Cranial reflexes require what?
require input from the brain (integrated from within)
Innate reflexes
Genetically programmed in everyones body
Conditioned reflexes
learned reflexes - acquired through experience
Monosynaptic reflexes
Have 2 neurons - afferent and efferent (only somatic motor reflexes)
Somatic motor reflexes
Controls the effector - controls skeletal muscles (efferent)
Autonomic reflexes
Controls the effector - control smooth and cardiac muscle, glands and adipose tissue (efferent)
Polysynaptic reflexes
One or more interneurons between afferent and efferent neurons (all autonomic reflexes – have 3 neurons)
What is the stretch reflex (aka knee-jerk reflex)
only known monosynpatic reflex
- receptor is a muscle spindle that detects lengthening of the muscle
- tapping the patellar tendon below the knee cap causes the quadriceps in the upper thigh to stretch which excites the muscle spindles, therefore generating AP’s that travel to the spinal cord
What are muscle spindles
stretch receptors that send info to the spinal cord and brain about muscle length and changes in it
What are proprioceptors?
sensory receptors in the subcutaneous tissues that detect motion and position of the body through a stimulus produced within the body (in muscles and joints)
What do extrafusal muscle fibers do?
receptor for stretch and force – most of the muscle and are the major force-generating structure (larger than intra)
What are intrafusal muscle fibers?
found within each muscle spindles, contain afferent receptors for stretch and contractile elements on the ends (smaller than extra)
- central region lacks myofibrils
What is the central region of an intrafusal muscle fiber composed of?
no myofibrils, wrapped with sensory nerve endings stimulated by stretch
What is muscle tone?
the amount of tension in muscles (even a little bit present at rest)
What do sensory neurons do? (X3)
- get activated by sensory input from the environment
- send AP’s to the spinal cord
- continuously activate motor neurons keeping the muscle at a tone
What happens when spindles/muscles stretch?
- causes sensory fibers to fire more rapidly
- more AP generated
- creates a reflex contraction to prevent damage
What keeps muscle spindles alive?
gamma motor neurons
What keeps muscle spindles alive/tense/give them tone?
gamma motor neurons
What do alpha motor neurons do?
largest neurons in the spinal cord, innervate (provide nerves) extrafusal muscle fibers and are directly responsible for initiating their contraction
What are the 4 key things for a successful completion of a voluntary motor task
- development of an idea to move
- putting together a program of motor commands for the movement
- executing the movement
- constant feedback to ensure it was smooth and successful