GETTING INFORMATION IN AND OUT OF THE BRAIN

GETTING INFORMATION IN AND OUT OF THE BRAIN

Getting information into and out of the brain relies on the Central Nervous System (CNS) and the Peripheral Nervous System (PNS) working together via specialized neural pathways.

The flow of information is categorized into two main directions:

1. Input (Afferent/Sensory): Information coming into the CNS (brain and spinal cord).

2. Output (Efferent/Motor): Information going out of the CNS to the body's effectors (muscles and glands).

---

👂 Input: Sensory (Afferent) Pathways

Sensory information from the environment (e.g., sight, touch, pain) travels toward the brain via sensory neurons.

• Peripheral Receptors: Specialized sensory receptors in the skin, eyes, ears, and internal organs detect stimuli (e.g., pressure, light, chemical signals).

• Transmission: This detection generates an electrical impulse (action potential) in a sensory neuron.

• Ascending Tracts: The impulse travels along the nerve fibers (axons) through peripheral nerves and then enters the spinal cord or brainstem. Once inside the spinal cord, it travels toward the brain in organized bundles called ascending tracts.

  • Body Below the Neck: Information ascends through the spinal cord. Major pathways, like the Spinothalamic Tract (for pain and temperature) and the Dorsal Column System (for fine touch and proprioception), carry the signal.

  • Head and Neck: Information is carried directly to the brainstem via the Cranial Nerves (e.g., the Optic Nerve for vision, the Vestibulocochlear Nerve for hearing/balance).

• Processing Centers: The sensory signal is typically relayed in the thalamus (the brain's major relay center) before reaching its final destination in the cerebral cortex (e.g., the Somatosensory Cortex in the parietal lobe for touch, the Visual Cortex in the occipital lobe for sight).

---

💪 Output: Motor (Efferent) Pathways

Instructions for movement and gland function travel away from the brain to the body's muscles and glands via motor neurons.

• Initiation: Voluntary movement instructions are typically initiated in the cerebral cortex, mainly the Primary Motor Cortex in the frontal lobe.

• Descending Tracts: The instructions travel down from the cortex as electrical impulses along upper motor neurons through the brainstem and into the spinal cord in bundles called descending tracts. The most famous of these is the Corticospinal Tract, which controls voluntary, skilled movements of the limbs.

• Relay in Spinal Cord: In the spinal cord, the upper motor neuron synapses (communicates) with a lower motor neuron.

• Final Destination: The lower motor neuron's axon exits the spinal cord and travels through peripheral nerves to connect directly with the muscle fiber or gland, causing it to contract or secrete.

This constant, rapid flow of input (sensory) and output (motor) allows the brain to perceive the environment, process the information, and execute appropriate and timely responses.

How does information come into the brain? 

A lot of information comes in through the spinal cord at the base of the brain. Think of a spinal cord as a thick phone cable with thousands of phone lines. If you cut that spinal cord, you won't be able to move or feel anything in your body. Information goes OUT from the brain to make body parts (arms and legs) do their job. 

There is also a great deal of INCOMING information (hot, cold, pain, joint sensation, etc.). Vision and hearing do not go through the spinal cord but go directly into the brain. That’s why people can be completely paralyzed (unable to move their arms and legs) but still see and hear with no problems.

Information enters from the spinal cord and comes up the middle of the brain. It branches out like a tree and goes to the surface of the brain. The surface of the brain is gray due to the color of the cell bodies (that's why it's called the gray matter). The wires or axons have a coating on them that's colored white (called white matter).

GETTING INFORMATION IN AND OUT OF THE BRAIN VIDEO :