Mod 4(part2)

The Nervous System Overview

• The nervous system functions as an electrochemical communication network encompassing all nerve cells.

• Central Nervous System (CNS):

  • Comprised of the brain and spinal cord.

  • Acts as the body’s decision-making center.

• Peripheral Nervous System (PNS):

  • Comprises sensory and motor neurons.

  • Connects the CNS to the rest of the body, facilitating sensory information gathering and motor action.

Components of the Nervous System

• Nerves vs. Neurons:

  • Neurons are the basic nerve cells responsible for transmitting information.

  • Nerves are bundles of axons that serve as electrical cables linking the CNS to sensory receptors, muscles, and glands.

• Functional Divisions:

  • CNS (Central Nervous System): Brain and spinal cord (depicted in green).

  • PNS (Peripheral Nervous System): Everything else in the body (depicted in red).

Divisions of the Peripheral Nervous System

• Somatic Nervous System:

  • Controls voluntary movements and the skeletal muscles.

  • Involves sensory input and motor output.

• Autonomic Nervous System (ANS):

  • Regulates involuntary functions and internal organs.

  • Divided into:

    • Sympathetic Nervous System:

      • Prepares body for arousal and 'fight or flight' responses.

      • Increases heart rate, inhibits digestion, and releases energy.

    • Parasympathetic Nervous System:

      • Promotes calming and conservation of energy.

      • Slows down heart rate, stimulates digestion, and promotes relaxation.

Functions of Neurons

• Types of Neurons:

  • Afferent Neurons (Sensory Neurons):

    • Transmit sensory information from the body to the CNS.

  • Efferent Neurons (Motor Neurons):

    • Carry outgoing signals from the CNS to muscles and glands.

  • Interneurons:

    • Connect sensory and motor pathways within the CNS; process information internally.

Reflex Actions

• Simple Reflexes:

  • Involuntary responses that bypass the brain initially (e.g., pain reflex).

  • Example:

    • When touching a flame, sensory neurons activate, sending signals to the spinal cord, which quickly relays signals through interneurons to motor neurons, causing an immediate withdrawal of the hand before the brain registers the pain.

The Endocrine System Overview

• The endocrine system comprises glands that secrete hormones into the bloodstream.

• Hormones travel through the body, influencing various tissues, including the brain.

Feedback System

• Master Gland: Pituitary gland, influenced by the hypothalamus, controls other glands such as the adrenal glands, thyroid, parathyroid, pancreas, and sex organs (ovaries and testes).

• This system maintains homeostasis and regulates hormone levels.

Stress Responses

• Stress activates the hypothalamus, prompting the pituitary gland to release hormones that stimulate the adrenal glands to produce cortisol, a stress hormone that raises blood sugar levels.

• Link between stress and mental health: Experiencing prejudice can trigger stress responses, contributing to later depression.

• The physiological effects of hormone release can persist longer than nerve signals, leading to prolonged stress reactions.