Nervous System: CNS and PNS

• The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
• The CNS consists of the brain and spinal cord.
• The PNS includes all neural tissue outside the CNS.

Central Nervous System (CNS)

• The CNS is responsible for integrating, processing, and coordinating sensory data and motor commands.
• It also controls higher functions such as intelligence, memory, learning, and emotion.
• The brain, a component of the CNS, performs complex integrative functions.
• The spinal cord relays information between the brain and the rest of the body, as well as reflexes.

Peripheral Nervous System (PNS)

• The PNS delivers sensory information to the CNS and carries motor commands to peripheral tissues and systems.
• It is further divided into the somatic nervous system (SNS) and the autonomic nervous system (ANS).
• The SNS controls skeletal muscle contractions, enabling voluntary movements.
• The ANS regulates involuntary functions, such as smooth muscle, cardiac muscle, and gland activity.

Autonomic Nervous System (ANS)

• The ANS, also known as the visceral motor system, regulates the body's internal environment.
• It operates without conscious control.
• The ANS is divided into the sympathetic and parasympathetic divisions.
• The sympathetic division is responsible for the "fight or flight" response.
• The parasympathetic division promotes "rest and digest" functions.

Neurons

• Neurons are the basic functional units of the nervous system.
• They are responsible for transmitting information throughout the body.
• Neurons have a cell body (soma), dendrites, and an axon.
• Dendrites receive signals from other neurons.
• The axon transmits signals to other neurons or target cells.
• Neurons communicate with each other at synapses.

Synapses

• Synapses are specialized junctions where neurons communicate.
• At a synapse, the presynaptic neuron releases neurotransmitters.
• Neurotransmitters bind to receptors on the postsynaptic neuron.
• This binding can either excite or inhibit the postsynaptic neuron.
• Electrical synapses involve direct physical connections between cells, allowing for rapid signal transmission.
• Chemical synapses rely on neurotransmitters to transmit signals across the synaptic cleft.

Motor Control

• The nervous system controls movement through a complex hierarchy.
• Higher brain centers plan and initiate movements.
• The motor cortex executes voluntary movements.
• The cerebellum coordinates movements and maintains balance.
• Basal ganglia are involved in motor control, particularly in initiating and terminating movements, and in procedural learning.
• The spinal cord contains motor neurons that directly innervate muscles.

Sensory Processing

• Sensory receptors detect stimuli from the environment.
• Sensory information is transmitted to the CNS for processing.
• Different types of sensory receptors detect different stimuli, such as light, sound, touch, temperature, and chemicals.
• Sensory pathways relay information from the receptors to the brain.
• The cerebral cortex interprets sensory information, allowing us to perceive the world around us.
• Sensory information from the body is processed in the somatosensory cortex.
• Visual information is processed in the visual cortex.
• Auditory information is processed in the auditory cortex.