DG

Nervous System and Endocrine System Overview (PNS, ANS, Brain, Pituitary)

The Nervous System: overview

  • The nervous system is an electrochemical network that coordinates body activities through electrical signals and chemical messengers.

Peripheral Nervous System (PNS)

  • The PNS consists of sensory and motor neurons that connect the Central Nervous System (CNS) to the rest of the body.
  • Sensory neurons carry information from the body to the CNS; motor neurons carry commands from the CNS to muscles and glands.

Somatic vs. Autonomic Systems

  • Somatic nervous system: controls voluntary skeletal muscle movement.
  • Autonomic nervous system (ANS): controls glands and internal organs without conscious effort.

Autonomic Nervous System divisions

  • Sympathetic division (often linked to arousal and energy expenditure): prepares the body for action ("fight or flight").
  • Parasympathetic division (often linked to conserving energy): promotes rest and digestion ("rest-and-digest").

Endocrine System

  • The endocrine system is a set of glands that secrete hormones into the bloodstream.
  • Hormones travel through the bloodstream to affect distant tissues and organs, including those in the brain.
  • The endocrine system transmits and interacts with neural signaling to regulate body processes over longer timescales.

Pituitary gland and hormonal control

  • The pituitary gland is often described as the master gland.
  • It influences the release of hormones by other glands throughout the body.
  • Through its connections with the brain, it coordinates hormonal responses that affect multiple tissues.

Interaction between the Endocrine System and the Brain

  • Hormonal signaling complements neural signaling, enabling slower, long-lasting regulation of physiology and behavior.
  • Hormones can modulate brain function and influence cognitive and emotional processes, as well as bodily states.

The Brain: general facts

  • The brain contains about 86 \text{ billion} neurons.
  • The brain is composed of many parts; often described in terms of major divisions: forebrain, midbrain, and hindbrain.
  • The transcript mentions 53 parts of the brain; this likely refers to many distinct brain structures sometimes grouped into broader regions (forebrain, midbrain, hindbrain).

Brain Regions and Core Structures

  • The Brain Stem: the oldest and innermost brain region; essential for basic life-support functions and acting as a conduit between brain and spinal cord.
  • Thalamus: central control center; acts as a relay and processing hub for sensory and motor signals.
  • Reticular Formation: a network of neurons running through the brainstem; involved in arousal, attention, and regulation of wakefulness.

Notes on relationships (implicit in the transcript)

  • The CNS (brain and spinal cord) interfaces with the PNS to receive sensory input and send motor commands.
  • The hypothesized interactions between endocrine signals (pituitary and other glands) and brain activity contribute to overall regulation of behavior and homeostasis.