Module 3: reflexes Flashcards
what is a reflex?
an inborn, involuntary or hardwired rapid response to a stimulus
what do reflexes do?
- maintain posture
- control visceral organs/autonomic activities (heart beat, breathing)
- safety mechanism
can you change reflexes?
yes, by learning them and by concious effort
do reflexes go to the brain?
no
How would you describe the control of a reflex?
limited, top down voluntary control, lowest activity in flow of reactions
what are the 2 types of reflexes?
- somatic: skeletal muscle
- autonomic (visceral): cardiac muscles
what are the 5 components of the reflex arc?
- receptor
- sensory neuron
- integration centre
- motor neuron
- effector neuron
what does the receptor do?
senses change in their environment and change their properties in response to the stimuli
what does the sensory neuron do?
arises from receptors and synapses either directly or indirectly (interneurons) to the motor neuron in the spinal cord
what does the integration center do?
takes in sensory in the CNS and relays to motor, it can be either monosynaptic or polysynaptic (interneurons)
what does a motor neuron do?
conducts efferent impulses from integration centre to effector organ
what does an effector do?
the axons of the alphs motor neuraons form connections with the extrafusal muscle fibers via the neuromuscular junction to cause a rection
what does polysynaptic mean, give example
there are interneurons in the spinal cord combined to create the reaction, can be slower than monosynaptic.
e.g. withdrawl reflex
what does monosynaptic mean, give example
there is a direct synapse between the sensory neuron and motor neuron, it’s a very fast reaction
e.g. knee jerk
describe a receptor
- a very specialised structure adapted to their purpose
- come in a diversity of form due to specialisation
- do not perceive, they sense
what are the 5 different senses that receptors sense?
- mechanical: touch, vibration, stretch
- termperature: thermoreceptor
- light ( photoreceptor)
- chemical (chemoreceptor)
- painful (Nociceceptors)
describe a muscle spindle
- long (elongated) structure aligned in parrallel to skeletal muscle fiber
- embedded within the extrafusal muscle fiber
- has own muscle fibers called intrafusal muscle fibers
- has efferent and afferent neurons s attached to keep it sensitive to the extrafusal muscles.
- is encased in a capsule made from connective tissue
describe the Golgi tendon organ
- located within the tendon, near the junction
- aligned in a series
- responds to muscle tension by doing the opposite
how is the muscle spindle innervated?
by the gamma motor neuron
how are the extrafusal muscles innervated?
by the alpha neurons
how are sensory neurons classified?
by their diamter
which nerve groups are important for somatic reflexes?
group 1A
group 1B
group 2
which group is the fastest in somatic reflexes?
group 1A
which group is the slowest in somatic reflexes?
group 4
why is the size of the somatic nerve important?
the bigger it is the more myelinated sheets it has, so faster responses
what are the properties of interneurons
they are either excitory or inhibitory