✅involuntary Movement Flashcards
What is a reflex?
Involuntary motor response mediated by a neural arc in response to a sensory input; can be generated in spinal cord segments with commands from higher brain centres.
What is the reflex arc?
it is the neural pathway used in reflex action
What does the reflex arc consist of?
The afferent nerve input to the nerve centre.
The nerve centre that produces activity in the efferent nerves to an effector organ.
Where does the reflex arc begin?
A receptor
Where does the reflex arc end?
Peripheral effector
What are the three main points of neural reflexes?
- Rapid, automatic responses to specific stimuli
- Basic building blocks of neural function
- One neural reflex produces one motor response
What happens at Step 1: Arrival of stimulus, activation of receptor
Physical or chemical changes
What happens at Step 2: Activation of sensory neuron
Graded depolarization
What happens at Step 3: Information processing by postsynaptic cell
Triggered by neurotransmitters
What happens Step 4: Activation of motor neuron
Action potential
What happens at Step 5: Response of peripheral effector
Triggered by neurotransmitters
What are somatic reflexes?
-Involuntary control of muscle (posture and movement)
-Respond to afferent stimulation
(Eg. Knee-jerk)
What are visceral reflexes?
Control systems other than muscular system
E.g( coughing, sneezing etc)
What are cranial reflexes?
They occur in the brain
E.g. ( reflex movements in response to sudden loud noises, jumping when scared)
What are spinal reflexes?
They occurs in the spinal cord
E.g. ( walking, running, typing)
What reflexes range in complexity?
Spinal reflexes
What happens with the Monosynaptic Reflex (stretch reflex)?
There is little delay between sensory input and motor output.
What does muscle stretch lead to?
activation of Ia afferent
What does La Afferent make?
monosynaptic excitation of motoneurones from same and agonist muscles
How quickly does contraction in the spinal muscles occur?
20-40msec
What is contraction of the muscle?
compensation to stretch
What does reflex act to prevent?
Length change
What are the 4 points of Reciprocal Inhibition?
- Stretch reflex excites motoneurones from agonists
* but inhibits antagonists
• Ia inhibitory interneurone
• disynaptic inhibitory pathway
What does Afferent Inhibition prevents skeletal muscle from?
• Developing too much tension
• Tearing or breaking tendons
Where does the Afferent inhibition arise from?
from activation of Golgi Tendon Organ
How does the afferent inhibition act?
Acts via Ib inhibitory interneurone
When does the Afferent inhibition act?
Only operates in posture not during walking
What is the Polysynaptic Reflex (tendon reflex)?
A Complicated response (more than monosynaptic reflexes)
What controls more than one muscle group?
Interneurons
What can polysynaptic reflexes produce?
EPSPs or IPSPs
What can polysnyaptic reflexes cause?
Many spinal segments
What can polysynaptic reflexes do?
Move body part away from stimuli (pain or pressure)
What is Flexion Withdrawal Reflex?
Action to move part of body away from painful or harmful stimulus
What is the Crossed Extensor Reflex?
The stretch, tendon and withdrawal reflexes are ipsilateral reflex arcs (ipsi, same + lateral, side): sensory stimulus and motor response occur on the same side of the body. This is a contralateral reflex arc (motor response occurs on the side opposite the stimulus.
What happens when Flexor reflex causes leg to pull up
Crossed extensor reflex straightens other leg to receive body weight and stop person falling over
What is a flexor reflex?
The quick contraction of the flexor muscles resulting in the withdrawal of a limb from an injurious stimulus
What needs to happen for a flexor reflex?
Contraction of the flexors and relaxation of the extensors in that limb
What is a Polysynaptic reflexive arc
A pathway in which signals travel over many synapses on their way back to the muscle
What are Five General Characteristics of Polysynaptic Reflexes?
- Involve pools of interneurons
- Are intersegmental in distribution
- Involve reciprocal inhibition
- Can be long lasting
- Several reflexes cooperate
– To produce coordinated, control response
Reflexes adapt to the existing conditions and can be modified by sensory input at the spinal cord level
True or Flase?
True
How can Higher Centres can alter Spinal Reflexes?
Can facilitate or inhibit reflex motor patterns based in the spinal cord
– Example: Suppression of flexion reflex during walking
What is Spasticity?
Hyperactive stretch reflex leads to spasticity (long lasting uncontrolled
muscle contractions, sometimes rythmic – called clonus)
The Brain can Alter Spinal Reflexes.
T or F
True
What are Voluntary movements and reflex motor patterns?
• Higher centers of brain incoporate lower, reflexive motor patterns
• Automatic reflexes
– Can be activated by brain as needed
– Use few nerve impulses to control complex motor functions
• Examples: walking, running, jumping
