Pathways to the Brain

Question 1

What are the two key pathways where info goes from outside to inside the brain?

Answer 1

Dorsal spinothalamatic tract

Ventral spinothalamic tract

Question 2

What is the Dosral spinothalamic tract?

Answer 2

Carries haptic and proprioceptive information
Axons from the dorsal-root neurons enter the spinal cord and ascend un till the synapse in the dorsal column nuclei
Axons from the dorsal column nuclei cross over to the opposite side of the brain and project up through the brainstem
Axons synapse with neurons located in the ventrolateral nucleus of the thalamus which projects to the somatosensory cortex and motor cortex

Question 3

What is the ventral spinothalamic tract?

Answer 3

Carries nociceptive information
Axons from the dorsal route ganglion neurons enter the spinal cord and cross over right away and synapse onto neurons on the contralateral side. Axons from the contralateral spinal cord then ascend to the brain, where they join with other axons forming the medial lemniscus, synapsing with neurons located in the thalamus. Neurons from the thalamus then project to the somatosensory cortex

Question 4

What do the two separate pathways do?

Answer 4

Convey somatosensory information about different things, so that unilateral (damage) spinal cord damage results in distinctive sensory loses to other sides of the body below the site of injury

Question 5

What happens when there is unilateral (one side) damage to the spinal cord?

Answer 5

Damage causes loss of fine touch and pressure sensation on the same side of the body below the cut and loss of pain and temperature sensation on the opposite side of the body below the cut

Question 6

What actions don’t require information going to the brain?

Answer 6

Reflexes - making sure you are functioning well

Question 7

What is the monosynaptic reflex?

Answer 7

Reflex requiring one synapse between sensory input and movement - e.g. knee jerk reflex - involving 2 neurons

tap on tendon stretches muscle
sensory nerve responds by sending a signal t spinal cord, connects to neuron. Motor neuron stimulates the quadriceps muscle to contract and reduce the strength. Quads contracts

Question 8

What do complex reflexes involve?

Answer 8

More connections among sensory neurons, interneurons and motor neurons