Question

Describe a spinal reflex. In your answer use the following terms: Somatic motor neuron, sensory neuron, ascending signal, thalmus, sensory cortex.

Answer 1

. Spinal cord reflexes are simple behaviors produced by central nervous system (CNS) pathways that lie entirely within the spinal cord.

The path taken by the nerve impulses in a reflex is called a reflex arc.

Receptors in the muscles and tendons are stimulated by stretch, so initiating impulses which travel via the sensory neurones of the peripheral nerve to the posterior horn of the spinal cord. Within the spinal cord there may be a direct link with the motor cells in the anterior horn, but more often a connector neurone links the sensory and motor neurones. The impulse then travels out of the spinal cord along the Somatic motor neurones to the effector organ, a muscle, causing it to contract. Although these spinal reflexes do not need the brain for their action, sensory information is also sent to the brain via the ascending signals. Impulses from the brain may be inhibitory, so modifying the action of a reflex.

Pathway of Spinal Reflex:

Stimulation of receptors in a muscle by Stretch------Sensory Neuron-----Spinal Cord.

Spinal Cord has 3 Neurons.

1.Excitatory Inter Neuron----Somatic Motor Neuron----Muscle(Agonist)-Contraction

2.Inhibitory Inter Neuron-----inhibit motor neuron to triceps-Relaxation

3.InterNeurons-----Ascending Pathway----Thalamus-----Sensory Cortex.

Ascending Pathway-Dorsal Root Ganglion---Rostral Ventral Medulla---Peri Aqueductal Grey---Thalamus---Sensory Cortex

Thalamus:function of the thalamus is to relay motor and sensory signals to the cerebral cortex.