Intro to psychology 1

The nervous system is essential for communication within the body.
- It facilitates the movement of nutrients, oxygen, and other significant components from one part of the body to another.
Major systems involved:
- Skeletal muscular system: Responsible for movement.
- Digestive system: Concerned with breakdown and absorption of nutrients.
- Nervous system: Aids in communication and coordination between different body parts.

Central Nervous System (CNS):
- Comprises the brain and spinal cord (illustrated in red).
- Functions as the decision-making unit, often referred to as 'executive functions.'
- Examples include reacting quickly to touching a hot stove by moving the hand away.
Peripheral Nervous System (PNS):
- Encompasses all other neurons and nerves outside the CNS.
- Responsible for sending messages to muscles and relaying external information to the CNS.

The CNS makes decisions while the PNS executes these decisions through muscle movement.
Interdependence:
- The CNS relies on the PNS to gather data about the environment, such as pain or stimuli.
- The brain does not directly perceive external sensations and requires input from the PNS to function effectively.

Neurons: Basic units of communication in the nervous system.
- Types of neurons:
  - Sensory neurons: Collect external data (e.g., temperature, potential skin damage).
  - Interneurons: Process information in the spinal cord and decide appropriate motor responses.
  - Motor neurons: Act on muscle fibers to initiate movement.

Definition: Automatic responses to certain stimuli, managed largely by the spinal cord without direct input from the brain.
- Example: Touching a hot surface causes an involuntary reflex to pull the hand away quickly, protecting from injury.
The reflex arc involves:
- Sensory neurons sending information to the interneurons in the spinal cord.
- Interneurons activating motor neurons to carry out the immediate response.

Understanding pain:
- The brain itself lacks pain receptors; hence, procedures like brain surgery can occur without anesthesia.
- Pain perception arises in the brain when it interprets signals from the PNS.
The experience of pain drives behavioral responses, such as seeking treatment for an injury.

Neuron Anatomy:
- Dendrites: Receive information from other neurons through specialized receptor sites.
- Axon: Sends out neural impulses to communicate with other neurons at axon terminals.
- Myelin Sheath: Insulates the axon and speeds up neural impulse transmission.

Neurochemical Interaction:
- Neurotransmitters from one neuron interact with receptors of another, leading to changes in internal charge (graded potentials).
Graded potentials ascertain when the neuron has reached a threshold (around -55 mV) to trigger an action potential (a quick influx of sodium ions).
Action Potential: A rapid shift of the neuron's electrical state that travels down the axon, leading to neurotransmitter release at the axon terminals.

Resting potential: Neurons maintain a charge of approximately -70 mV until stimulated.
When stimulated, sodium ions flood in, causing depolarization to about +30 mV as action potentials initiate.
Recruitment of sodium channels propagates the signal along the axon via wave-like depolarization.

Myelin accelerates the transmission of electrical impulses along the axon, enhancing neural communication.
Myelination: The process occurs prenatally and continues into adolescence, improving neural efficiency over time and contributing to coordinated action and faster responses.

The integration of these systems and components forms a complex network facilitating communication and behavior execution throughout the body.