The Brain

how the brain receives and interprets

information from the environment

• The brain uses nerve signals to make sense of the world.

• Nerve signals travel to the brain from various sense receptors.

• The brain combines these signals with information from other parts of the brain.

The Nervous System

• What you see coming out of the brain are the nerves that are connected to the brain.

• Inside the human brain there are about 50 billion nerves; many more nerves in the brain than in the rest of the body.

• Together the brain and the nerves make up the Nervous System

• The nerves in our body and in our brain send signals. Most of these signals go from one nerve to another. Whenever we move, this is a nerve sending out a signal to a muscle.

• When we feel or see or hear or taste something, this is because of we have our receptors in our skin, eyes, ears, tongue and nose. Different receptors will detect different things.

• Signals are sent from receptors in our eyes, ears, skin, tongue and nose through nerves to our brains. The brain then has to make sense of the nerve signals it gets.

We can lose our ability to see or hear or taste or touch things in three ways:

1. We can damage the part of our body that sends the signals to our brains,

2. we can damage the parts of our brain that receive these nerve signals, or

3. we can damage the nerves somewhere in the path from the receptor to the brain.

If someone loses their sight or has problems seeing, the problem could be in their eyes or in the part of the brain

that receives nerve signals from our eyes.

If we lose our sense of touch, it could be that: a. we have damaged the touch receptors that send

signals to the brain, or b. we could have damaged a nerve between the

receptor and brain or c. we could have damaged the part of the brain that

receives these nerve signals

Somatosensory & Pain Neural Pathway

• Merkel’s Receptor – pressure & texture• Meissner Corpuscle – light touch• Ruffini Corpuscle – stretching/heavy pressure• Pacinian Corpuscle – deep pressure, high frequency

vibration• Free nerve endings sense pain and temperature.

Human skin contains several different sense receptors that respond to mechanical and thermal stimuli (e.g., touch, pressure, pain, cold, and heat). These receptors help us explore and determine the characteristics of our external environment.

Most sensory neurons have their cell bodies in spinal (dorsal root) ganglia

• Most of the information about touch centers in a thin, convoluted surface layer of the cerebrum of the human brain called the somatosensory cortex.

• Each point on this band of sensory cortex contains densely packed cells that correspond to sensory receptors from different parts of the body.

• The specific amount of space on the somatosensory cortex of the brain that is dedicated to sensing each body part is proportional to the density of the sensory receptors in that particular body region.

Pain

• Pain is very important to our survival.• Pain provides humans with information about

tissue-damaging stimuli, and thus enables them to protect themselves from greater damage.

Pain is protective in two ways:

1. First, it removes a person from stimuli that cause tissue damage through withdrawal reflexes.

2. Second, learning associated with pain causes the person to avoid stimuli that previously caused pain.

A nociceptor is a sensory neuron that responds to potentially damaging stimuli by sending nerve signals to the spinal cord and brain. This process, called nociception, usually causes the perception of pain. (Wikipedia)

The spinal and spinothalamic pathways for carrying pain signals

Two things happen once the message reaches the spinal cord: • Spinal interneurons transmit the

message to motor neurons that synapse with muscles involved in withdrawal reflexes. This reflex circuit removes the injured limb from the stimulus.

• Simultaneously, a message travels to the thalamus, which relays the message to the somatosensory cortex. Because of the difference in distance in these two pathways, nociceptive reflexes occur before pain messages reach the brain.

• Nerve impulses travel at between 6 – 30 m/s between sensory receptors and the brain, depending on the type of neuron

Assuming that the average Canadian female is1.6m tall and the average male is 1.76m, it wouldtake approximately .1s for your brain to“sense” a stubbed toe and roughly twice that time to send a message back to your leg to get out of the way.

In the case of serious burns, damage to skinreceptors can occur faster than they cantransmit a pain signal to the brain, resultingIn more damage than might otherwise be thecase (eg. Electrical burns)

NSAID

Non-Steroidal Anti-Inflammatory Druga class of drugs that provide analgesic and antipyretic (fever-reducing) effects, and, in higher doses, anti-inflammatory effects

The most prominent members of this group of drugs are aspirin, ibuprofen, and naproxen, all of which are available over the counter in most countries

Analgesicany member of the group of drugs used to achieve analgesia, relief from pain(Wikipedia)

Drugs that affect pain pathwaysPhysicians may treat severe pain with opiates such as morphine or codeine. These drugs bind to opioid receptors in the CNS to relieve pain

Physicians can also treat pain by blocking nerve conduction with anesthetics or by surgically cutting a nerve

Simply rubbing the injury, applying ice, or taking aspirin or other over-the-counter painkillers often reduces mild pains. These mechanisms work by reducing neural transmission either indirectly via inhibiting inflammation (e.g., aspirin, cold water) or via interfering with nociceptive messages in the spinal cord (e.g., rubbing the skin activates touch fibers that inhibit nociceptive neurons in the spinal cord).