L4Phisiological pt1

Overview of the Nervous System

• The nervous system is divided into two main parts:

  • Central Nervous System (CNS): Comprises the brain and spinal cord, responsible for processing, interpretation, and higher functions such as language and problem-solving.

  • Peripheral Nervous System (PNS): Extends beyond the CNS, facilitating communication between the body and the CNS by transmitting information in and out.

Central Nervous System (CNS)

• Components: Brain and spinal cord.

• Functions:

  • Processes information.

  • Interprets sensory data.

  • Engages in higher-level cognitive tasks (e.g., language, emotions).

Peripheral Nervous System (PNS)

• Definition: Refers to nerves that facilitate communication between the CNS and the rest of the body.

• Divisions:

  • Somatic Nervous System:

    • Governs voluntary behaviors.

    • Engages in sensory and motor activities.

    • Example: Walking across the room or feeling pain after touching something hot.

  • Autonomic Nervous System (ANS):

    • Controls involuntary actions.

    • Manages functions such as heart rate and digestion.

    • Further divided into sympathetic and parasympathetic systems:

      • Sympathetic Nervous System: Activates during emergencies (fight or flight response).

        • Prepares the body for quick action via physiological changes (e.g., increased heart rate, dilated pupils).

      • Parasympathetic Nervous System: Dominates during restful states (rest and digest).

        • Maintains bodily functions and conserves energy.

Sympathetic vs. Parasympathetic Activation

• Sympathetic Activation:

  • Occurs in response to threats or emergencies.

  • Triggers physiological changes: dilated pupils, accelerated heartbeat, increased respiration, inhibited digestion, and adrenaline release.

  • Responses:

    • Fight: confront the danger.

    • Flight: escape the danger.

    • Freeze: become immobile to avoid detection.

• Parasympathetic Activation:

  • Returns the body to a calm state after a threat has passed.

  • Restores normal physiological functions, such as digestion and reduced heart rate.

Neurons: The Basic Units of Communication

• Definition: Neurons are the fundamental working units of the nervous system responsible for transmitting messages throughout the body.

• Key Functions:

  • Carry signals between the CNS and peripheral areas (muscles and glands).

  • Facilitate higher order brain functions through communication with each other.

Anatomy of Neurons

• Cell Body (Soma): Contains the nucleus and is the site of chemical processing.

• Dendrites: Tree-like structures that receive incoming signals.

• Axon: Long structure that transmits signals away from the cell body to the next neuron, muscle, or gland.

• Myelin Sheath: Fatty insulation surrounding axons, enhancing signal speed and protecting the signal integrity.

• Synapse: The gap between two neurons where neurotransmitters are released and received.

Neural Communication

• Process: Involves both electrical and chemical signals.

• Electrical Phase:

  • Resting Potential: The state of a neuron when it is not firing (approximately -70mV).

    • More sodium ions outside than potassium ions inside.

  • Action Potential: Occurs when a neuron sends a message; sodium ions rapidly enter the cell, reversing its polarity.

    • The signal propagates down the axon like a ripple effect.

  • Repolarization: Restores the original polarization by pumping potassium ions out and sodium in.

  • Refractory Period: Time after firing when the neuron cannot fire again until returning to resting potential.

Chemical Phase: Neurotransmitters

• Neurotransmitters: Chemicals released at the synapse that transmit signals between neurons.

• Process: When an action potential reaches the axon terminal, neurotransmitters are released into the synaptic cleft and bind to receptors on the postsynaptic neuron.

  • Can have excitatory effects (activating the receiving neuron) or inhibitory effects (suppressing neural activity).

• Reuptake: Excess neurotransmitters that are not bound to receptors are reabsorbed into the presynaptic neuron, ensuring efficient recycling.

Conclusion

• Understanding the nervous system's organization and neurons' roles is crucial in physiological psychology.

• Future discussions will focus on specific neurotransmitters and methods for measuring brain activity.