psych lecture spinal cord and brain stem

Earthworm has slightly over 300 neurons (nerve cells) at one end, forming its brain.
These 300 interconnected neurons function similarly to switches, enabling a range of operations despite their simplicity.
Neurons also branch out to other segments in the body, facilitating communication along the length of the earthworm.

Humans possess a similar basic structure in the brain, protected within the skull (foramen magnum).
Spinal cord extends down the vertebrae, with critical areas for signaling located mainly around L1-L2 vertebrae.
The protection of the nervous system reflects its importance; damage can lead to loss of function.

Movement and Sensation: An earthworm can sense touch (sensation) and respond to stimuli, sending signals from sensory receptors to the brain and back out to muscles for movement.
Spinal Cord Injuries: Different injuries might affect either sensation or movement depending on whether the injury is to the front or back of the spinal cord.
Example: A spinal injury could result in numbness with preserved movement or sensation with compromised movement.

Digestion and Regulation: Earthworms digest food; this function is regulated through the nervous system.
Sensory Monitoring: Sensors monitor levels of glucose, salt, and oxygen in the earthworm's body, aiding in overall regulation.
Sleep Patterns: Earthworms exhibit sleep-like states to conserve energy, similar to humans.
Heart Function: Earthworms have a rudimentary heart system with seven aortic arches, regulated by neural connections and cardiac muscles that contract rhythmically.

Earthworms are hermaphrodites, possessing both male and female reproductive systems.
The mating behavior leads to the exchange of sperm and fertilization.

Brain Stem: Controls basic life functions (breathing, heart rate, digestion).
Reflex Arcs: Involve sensory neurons, influential in both sensation and movement.
Indirect Control: Functions like heartbeat and breathing can be modulated to some extent, indicating a mixture of voluntary and involuntary control.

Hippocampus: Essential for forming new memories, particularly short-term memory.
Damage to the hippocampus can result in an inability to form new memories while preserved memories pre-injury remain intact.
Amygdala: Involved in emotional responses, particularly fear and aggression; linked to basic emotional functions.
Memory Functions: Involves the transition from short-term to long-term memory, influenced by emotional context and repetition.
Cases of Brain Injury: Instances like viral infections affecting memory demonstrate how different brain functions can be impacted and lead to specific memory and behavioral changes.

Understanding the earthworm’s biology is foundational for comprehending complex human systems, particularly how neurons function in both organisms, the significance of our nervous system, and the interplay between different brain regions in regulating life functions.