Nervous System Overview

Nervous System

• The nervous system controls every action, thought and feeling
• The nervous system consists of two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS)

Central Nervous System (CNS)

• The CNS is comprised of the brain and the spinal cord
• The brain is the control center of the nervous system and is responsible for thoughts, emotions, memories and movements
• The spinal cord is a tube of nerves that connects the brain to the rest of the body
• All messages to and from the brain run through the spinal cord
• The spinal cord also processes some information, such as reflexes, without needing to consult the brain

Spinal Reflexes

• A reflex is a simple, automatic response by nerves in the spinal cord that doesn't require instructions from the brain
• Reflexes are quick because they do not need to be processed by the brain
• For example, when you touch a hot stove, you quickly pull your hand away before you feel the pain. This is because the spinal cord sends a signal to the muscles in your arm to withdraw, even before the pain signal reaches your brain; the pain is registered afterwards

Peripheral Nervous System (PNS)

• The PNS is the network of nerves that connects the CNS to the rest of the body
• The PNS receives information from the environment and sends it to the CNS
• The PNS also carries signals from the CNS to the muscles and glands, telling them what to do
• The PNS is divided into two systems: the somatic nervous system and the autonomic nervous system

Somatic Nervous System

• The somatic nervous system controls voluntary movement of the body’s skeletal muscles
• It is responsible for things like walking, talking, writing and other conscious movements

Autonomic Nervous System

• The autonomic nervous system controls glands and the internal organs
• The autonomic nervous system is responsible for automatic activities such as heartbeat, digestion, breathing, and temperature regulation
• The autonomic nervous system is further split into two branches: the sympathetic nervous system and the parasympathetic nervous system

Sympathetic Nervous System

• The sympathetic nervous system is responsible for the body’s “fight-or-flight” response, which is activated in stressful or dangerous situations
• The sympathetic nervous system increases heart rate, blood pressure and respiration
• It also diverts blood flow from the digestive system to the muscles, preparing the body for action

Parasympathetic Nervous System

• The parasympathetic nervous system works to calm the body down and conserve energy
• It is responsible for slowing the heart rate, lowering blood pressure, stimulating digestion, and relaxing the body
• The parasympathetic nervous system is responsible for restoring the body back to homeostasis (stability and balance) after stressful situations

Nervous System

• The nervous system is responsible for receiving and processing information from the environment, and for sending signals to muscles and glands.
• There are two major divisions of the nervous system: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

Central Nervous System (CNS)

• The CNS consists of the brain and the spinal cord.
• The brain is the control center of the nervous system, responsible for processing information, making decisions, and controlling movement.
• The spinal cord is a tube of nerves that connects the brain to the rest of the body.
• All messages to and from the brain run through the spinal cord.

Spinal Reflexes

• A reflex is a simple, automatic response by nerves in the spinal cord that doesn't require instructions from the brain.
• Spinal reflexes can occur before the brain registers pain because it takes longer for the pain signal to reach the brain.
• An example of a spinal reflex is pulling your hand away from a hot stove.

Peripheral Nervous System (PNS)

• The PNS is a network of nerves that connects the central nervous system to other parts of the body.
• The PNS contains sensory neurons, which carry information from the body to the CNS, and motor neurons, which carry information from the CNS to the body.

Somatic Nervous System

• The somatic nervous system controls voluntary movement of the body's skeletal muscles.

Autonomic Nervous System

• The autonomic nervous system controls glands and the internal organs.
• The autonomic nervous system is responsible for automatic activities such as heartbeat and digestion.
• It releases hormones into the bloodstream.

Sympathetic Nervous System

• The sympathetic nervous system prepares the body for stressful or dangerous situations.
• When activated, it increases blood pressure, accelerates heartbeat, slows digestion, and raises blood sugar.

Parasympathetic Nervous System

• The parasympathetic nervous system calms the body and conserves energy after stressful situations.
• When activated, it reduces heart rate, decreases blood pressure, and restores the body back to homeostasis (stability/balance).
• It can be thought of as the "rest and digest" system, as it slows digestion and prepares the body for rest.

Nervous System

• The nervous system is comprised of the central nervous system (CNS) and the peripheral nervous system (PNS)

Central Nervous System (CNS)

• The CNS is made up of the brain and the spinal cord
• The spinal cord is a tube of nerves that connects the brain to the rest of the body.
• All messages to&from the brain travel through the spinal cord

Spinal Reflexes

• A reflex is a simple, automatic response by nerves in the spinal cord that requires no input from the brain
• Pain is not registered until moments later because it takes time for the nerve impulses to reach the brain
• A classic example is when a person pulls their hand away from a hot stove

Peripheral Nervous System (PNS)

• The PNS is a network of nerves that connects the CNS to the rest of the body
• The PNS is further divided into the somatic nervous system and the autonomic nervous system

Somatic Nervous System

• The somatic nervous system controls voluntary movement of the body's skeletal muscles

Autonomic Nervous System

• The autonomic nervous system controls glands and internal organs, governing automatic activities such as heartbeat and digestion
• The autonomic nervous system releases hormones into the bloodstream

Autonomic Nervous System: Sympathetic vs. Parasympathetic

• The sympathetic nervous system arouses the body to mobilize during stressful or dangerous situations, preparing the body for "fight-or-flight"
  • This system increases blood pressure, accelerates heartbeat, slows digestion and raises blood sugar
• The parasympathetic nervous system calms the body and conserves energy after stressful situations, restoring the body to homeostasis (stability/balance)
  • This system reduces heart rate, decreases blood pressure, and slows digestion

Nervous System

• The nervous system is a complex network of specialized cells that coordinates all of the body's actions and reactions.
• It is responsible for receiving information from the environment, processing that information, and sending signals to the body's muscles and glands.
• The nervous system is comprised of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS).

Central Nervous System (CNS)

• The CNS includes the brain and the spinal cord.
• The brain is the control center of the nervous system, responsible for thought, emotion, and movement.
• The spinal cord is a tube of nerves that connects the brain to the rest of the body, relaying messages between the brain and the peripheral nervous system.
• All messages to and from the brain run through the spinal cord.

Spinal Reflexes

• Spinal reflexes are simple, automatic responses by nerves in the spinal cord that don't require instructions from the brain.
• These responses are triggered by sensory input and bypass the brain, enabling rapid reactions.
• A classic example is pulling your hand away from a hot stove.
• Pain isn't registered until moments later because the pain signal takes longer to reach the brain.

Peripheral Nervous System (PNS)

• The PNS is a network of nerves that connects the CNS to other parts of the body.
• It is responsible for carrying sensory information from the body to the CNS and motor commands from the CNS to the body.
• The PNS is further subdivided into the somatic nervous system and the autonomic nervous system.

Somatic Nervous System

• The somatic nervous system is the part of the PNS that controls voluntary movement of the body's skeletal muscles.
• It allows us to consciously move our limbs, torso, and facial muscles.

Autonomic Nervous System

• The autonomic nervous system is the part of the PNS that controls involuntary processes, including regulating the body's internal organs, glands, and smooth muscles.
• This system operates automatically, influencing heart rate, digestion, breathing, and other essential functions.
• It is further divided into the sympathetic and parasympathetic nervous systems.

Sympathetic Nervous System

• The sympathetic nervous system prepares the body for stressful or dangerous situations, also known as the "fight-or-flight" response.
• When activated, it triggers a cascade of physiological changes, including increased heart rate, accelerated breathing, elevated blood pressure, and dilation of pupils.
• It prepares the body to respond quickly and effectively to perceived threats.

Parasympathetic Nervous System

• The parasympathetic nervous system calms the body after a stressful situation and conserves energy.
• It counteracts the effects of the sympathetic nervous system, returning the body to homeostasis (stability and balance).
• It slows heart rate, lowers blood pressure, constricts pupils, and promotes digestion.

Nervous System

• The nervous system is responsible for receiving, processing, and responding to information from both the internal and external environments.
• It is divided into two main parts:
  • Central Nervous System (CNS): Includes brain and spinal cord.
  • Peripheral Nervous System (PNS): Network of nerves that connect the CNS to the rest of the body.

Central Nervous System (CNS)

• Brain: The control center of the body, responsible for higher cognitive functions, emotions, and movement.
• Spinal Cord: A tube of nerves that connects the brain to the rest of the body.
  • All messages to and from the brain travel through the spinal cord.

Spinal Reflexes

• Reflex: A simple, automatic response by nerves in the spinal cord without requiring instructions from the brain.
• Examples:
  • Pulling your hand away from a hot stove.
  • Knee-jerk reflex.
• Pain is registered later because the signal needs time to reach the brain.

Peripheral Nervous System (PNS)

• Consists of nerves that connect the CNS to the rest of the body.
• Contains sensory neurons that transmit information from the body to the CNS.
• Divided into two systems:
  • Somatic Nervous System: Controls voluntary movements of skeletal muscles.
  • Autonomic Nervous System: Controls involuntary actions of glands, internal organs, and smooth muscles.

Autonomic Nervous System

• Controls many automatic processes in the body, such as heartbeat, digestion, and breathing.
• Divided into two branches:
  • Sympathetic Nervous System: Arouses the body during stressful situations, increasing heart rate, blood pressure, and release of energy.
  • Parasympathetic Nervous System: Calms the body after stressful situations, decreasing heart rate, conserving energy, and helping the body return to homeostasis.

Sympathetic Nervous System

• Prepares the body for "fight or flight" responses.
• Increases heart rate, blood pressure, and blood sugar levels.
• Dilates pupils and airways.
• Diverts blood from digestion to muscles.

Parasympathetic Nervous System

• Conserves energy and promotes rest and relaxation.
• Slows heart rate, reduces blood pressure, and lowers blood sugar levels.
• Constricts pupils and airways.
• Stimulates digestion.