Study Question Thirteen

• Q13. Describe the basis of reflexes and list all steps.
• Describe the basis of reflexes and list all steps.

  Reflexes are automatic, rapid responses to specific stimuli that help protect the body and maintain homeostasis. They occur without conscious thought and involve a simple neural pathway known as a reflex arc.
• Describe the basis of reflexes and list all steps.

  Reflexes are designed to produce quick reactions to potentially harmful stimuli, enabling the body to respond efficiently. They are typically processed in the spinal cord, allowing for faster responses compared to those that require involvement of the brain.
• Describe the basis of reflexes and list all steps.

  • First, the reflex arc start with the STIMULUS. A specific stimulus triggers a reflex, anything that causes a sensory response.
  • Secondly, a RECEPTOR in necessary. Specialized sensory receptors detect the stimulus and convert it into an electrical signal.
  • Thirdly, AFFERENT or SENSORY NEURONS. The electrical signal travels along the sensory neuron towards the spinal cord.
• Describe the basis of reflexes and list all the steps.

  • Fourth, INTEGRATION CENTER. Once the signal reaches the spinal cord, it enters the gray matter and synapses with an interneuron or a motor neuron. Here is the decision to respond.
  • Fifth, EFFERENT or MOTOR NEURONS. The motor neuron carries the signal away from the spinal cord to the effector.
• Describe the basis of reflexes and list all the steps.

  • Sixth, EFFECTOR. The effector, usually a muscle or gland, responds to the motor neuron’s signal. In a reflex, the muscle contracts, pulling the body away from the harmful stimulus.
  • Seventh, RESPONSE. The action occurs quickly, before the brain processes sensory input, leading to an immediate response.
• Reflexes can be classified by

  • development
  • response
  • complexity of circuit
  • processing site
• Reflexes of development

  • innate - genetically determined
  • acquired - learned
• Reflexes of response

  • somatic reflexes - control skeletal muscle contractions, include superficial and stretch reflexes
  • visceral (autonomic) reflexes - control actions of smooth and cardiac muscles, glands, adipose tissue
• Reflexes of complexity of circuit

  • monosynaptic - one synapse
  • polysynaptic - multiple synapses
• Reflexes of processing site

  • spinal reflexes - processing in the spinal cord
  • cranial reflexes - processing in the brain
• Label RED: stimulus

  
• Label ORANGE: receptor

  
• Label YELLOW: afferent

  
• Label GREEN: integrating center

  
• Label BLUE: efferent pathway

  
• Label PURPLE: effector

  
• Label UPPER BLACK: extero

  Label LOWER BLACK: intero

  
• Label UPPER GRAY: somatic sensory neuron in spinal nerve

  Label LOWER GRAY: visceral sensory neuron in spinal nerve

  
• Label WHITE: dorsal root ganglion

  
• Label BROWN: dorsal root

  
• Label UPPER DARK PINK: posterior gray horn

  Label LOWER DARK PINK: posterior gray horn

  
• Label UPPER MID PINK: anterior gray horn

  Label LOWER MID PINK: lateral gray horn

  
• Label UPPER MID BLUE: ventral root

  Label LOWER MID BLUE: ventral root

  
• Label UPPER TURQUOISE: somatic motor nerve

  Label LOWER TURQUOISE: autonomic preganglionic nerve

  
• Label UPPER GREEN: skeletal muscle

  Label LOWER GREEN: autonomic ganglion

  
• Label UPPER YELLOW: contraction

  Label LOWER YELLOW: ganglionic nerve or fiber

  
• Label ORANGE: adipose tissue, cardiac muscle, smooth muscle, gland

  
• Label RED: responses can vary

  
• General Functions

  • Starts with the STIMULUS
  • It then goes to the RECEPTOR
  • First pathway is AFFERENT
  • The center is called INTEGRATING CENTER
  • Second pathway is EFFERENT
  • Destination is the EFFECTOR
  • Finally, the RESPONSE
• Spinal Reflex - Somatic

  • Extero -(somatic sensory neuron in spinal nerve)->
  • Dorsal root ganglion -(dorsal root)->
  • Posterior gray horn ->
  • Anterior gray horn -(ventral root)->
  • Somatic motor nerve ->
  • Skeletal muscle ->
  • Contraction
• Spinal Reflex - Somatic

  • Extero -(somatic sensory neuron in spinal nerve)->
  • Dorsal root ganglion -(dorsal root)->
  • Posterior gray horn ->
  • Anterior gray horn -(ventral root)->
  • Somatic motor nerve ->
  • Skeletal muscle ->
  • Contraction
• Spinal Reflex - Somatic

  • Extero -(somatic sensory neuron in spinal nerve)->
  • Dorsal root ganglion -(dorsal root)->
  • Posterior gray horn ->
  • Anterior gray horn -(ventral root)->
  • Somatic motor nerve ->
  • Skeletal muscle ->
  • Contraction
• Spinal Reflex - Visceral

  • Intero -(visceral sensory neuron in spinal nerve)->
  • Dorsal root ganglion -(dorsal root)->
  • Posterior gray horn ->
  • Lateral gray horn -(ventral root)->
  • Autonomic preganglionic nerve ->
  • Autonomic ganglion ->
  • Ganglionic nerve or fiber ->
  • Adipose, cardiac muscle, smooth muscle, gland ->
  • Response can vary
• Spinal Reflex - Visceral

  • Intero -(visceral sensory neuron in spinal nerve)->
  • Dorsal root ganglion -(dorsal root)->
  • Posterior gray horn ->
  • Lateral gray horn -(ventral root)->
  • Autonomic preganglionic nerve ->
  • Autonomic ganglion ->
  • Ganglionic nerve or fiber ->
  • Adipose, cardiac muscle, smooth muscle, gland ->
  • Response can vary
• Spinal Reflex - Visceral

  • Intero -(visceral sensory neuron in spinal nerve)->
  • Dorsal root ganglion -(dorsal root)->
  • Posterior gray horn ->
  • Lateral gray horn -(ventral root)->
  • Autonomic preganglionic nerve ->
  • Autonomic ganglion ->
  • Ganglionic nerve or fiber ->
  • Adipose, cardiac muscle, smooth muscle, gland ->
  • Response can vary
• Cranial Reflex - Somatic

  • Extero -(somatic sensory neuron in cranial nerve)->
  • Cranial nerve nuclei (in brainstem, process sensory input) ->
  • Somatic motor neuron (in same or different cranial nerve) ->
  • Skeletal muscle also known as effectors (muscles for facial expressions or eye movement)
• Cranial Reflex - Somatic

  • Extero -(somatic sensory neuron in cranial nerve)->
  • Cranial nerve nuclei (in brainstem, process sensory input) ->
  • Somatic motor neuron (in same or different cranial nerve) ->
  • Skeletal muscle also known as effectors (muscles for facial expressions or eye movement)
• Cranial Reflex - Somatic

  • Extero -(somatic sensory neuron in cranial nerve)->
  • Cranial nerve nuclei (in brainstem, process sensory input) ->
  • Somatic motor neuron (in same or different cranial nerve) ->
  • Skeletal muscle also known as effectors (muscles for facial expressions or eye movement)
• Cranial Reflex - Visceral

  • Intero -(visceral sensory neuron in cranial nerve)->
  • Cranial nerve nuclei (contains all bodies of sensory neurons) ->
  • Nucleus of the solitary tract (in brainstem, processes visceral sensory input) ->
  • Autonomic preganglionic neuron (in brainstem) ->
  • Autonomic Ganglion (where synapses occur with postganglionic neurons)
  • Ganglionic nerve/fiber (carries signals to target organs)
  • Adipose, cardiac muscle, smooth muscle, gland (effectors)