Nervous System Overview

Overview

• The human nervous system is a complex network of billions of nerve cells that coordinates actions and transmits signals throughout the body.
• It is primarily responsible for communication, control, and integration.
• It plays a crucial role in sensory perception, motor function, and cognitive processes.

Central Nervous System (CNS)

• Composed of the brain and spinal cord.
• The brain is the control center, responsible for higher-order functions (thinking, learning, memory).
• The spinal cord is a long, tubular structure that connects the brain to the peripheral nervous system.
• It transmits signals between the brain and the rest of the body.
• It also has a role in reflex actions.

Peripheral Nervous System (PNS)

• Consists of all nerves outside the CNS.
• It's divided into two parts based on function.

Somatic Nervous System

• Controls voluntary movements.
• This system carries signals from the CNS to skeletal muscles.
• It allows for conscious control over bodily actions.

Autonomic Nervous System

• Controls involuntary actions like heart rate, digestion, and blood pressure.
• Subdivided into two branches with opposing effects:
  • Sympathetic: Prepares the body for "fight or flight" response, such as increasing heart rate and blood pressure.
  • Parasympathetic: Calms the body after the stressful situation response, like lowering heart rate and blood pressure.

Neuron Structure

• Neurons are the fundamental units of the nervous system.
• They consist of cell body, dendrites, and axon.
• Dendrites: Receive signals from other neurons.
• Cell body: Contains the nucleus and other organelles.
• Axon: Transmits signals to other neurons or cells.
• Myelin sheath: Insulates the axon to speed up signal transmission.
• Synapse: Specialized junction between neurons where communication occurs.

Neurotransmitters

• Chemical messengers that transmit signals across synapses.
• Diverse functions, playing roles in cognition, emotions, memory, and behavior.
• Examples include dopamine, serotonin, acetylcholine, norepinephrine.

Brain Regions

• Cerebrum: Largest part of the brain. Involved in higher-order functions such as thought, memory, and language.
• Cerebellum: Responsible for coordination of movement and balance.
• Brainstem: Controls basic life functions like breathing, heart rate, and sleep-wake cycles.

Spinal Cord Function

• Relays signals between the brain and the rest of the body.
• Involved in simple reflexes: rapid, involuntary responses to stimuli.
• Composed of white matter (myelinated axons) and gray matter (cell bodies and dendrites).

Sensory Perception

• The nervous system receives and interprets information from the external world.
• This includes sight, sound, touch, taste, and smell.
• Specialized receptors detect stimuli and convert them into electrical signals that are sent to the brain.

Disorders of the Nervous System

• Many disorders can affect the nervous system.
• Some examples are Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy.
• These disorders can result in a range of symptoms depending on the specific area of the affected brain or the nerves.

Protection of Nervous System

• The brain and spinal cord are protected by:
  • Skull: Protects the brain.
  • Vertebrae: Protect the spinal cord.
  • Meninges: Three layers of membranes that cushion and protect the brain and spinal cord.
  • Cerebrospinal fluid (CSF): Acts as a shock absorber filling the spaces within the meninges.

Key Concepts

• Action Potential: Electrochemical signal that travels down a neuron.
• Synaptic Transmission: The process of communication between two neurons.
• Neurogenesis: The formation of new neurons, although limited in adults.
• Plasticity: The ability of the nervous system to adapt and change throughout life.