Human Nervous System

Human Nervous System Overview

Coordinating Systems

• Systems that facilitate communication between the body's receptors and effectors.

• Essential for survival; allows organisms, including humans, to respond to environmental changes (stimuli).

• Two Human Coordinating Systems:

  • Nervous System

  • Endocrine System

• Both systems work synergistically to control bodily conditions and responses to stimuli.

Nervous Coordinating System

• Fast response system.

• Relies on electrical impulses traveling through nerves for immediate reactions.

Endocrine Coordinating System

• Slower system.

• Utilizes hormones transported in the blood for longer-term responses.

Functions of the Nervous System

• Acts as the body's control and communication center.

• Ensures a continuous flow of information between the brain, environment, and body parts, enhancing effective functioning.

How the Nervous System Functions

1. Sensory Function:

   • Sensory receptors detect changes in the environment (internal and external).

2. Integrative Function:

   • The central nervous system processes this information and determines necessary responses to stimuli.

3. Motor Function:

   • Effectors (muscles and glands) enact appropriate responses.

Example of Nervous System Functioning

• Riding a bike: sensing the red traffic light (sensory) -> central system interprets the stop command (integrative) -> applying brakes (motor).

Understanding Stimuli

• Stimuli: Physical or chemical changes in the environment that provoke a response from an organism.

• Examples of stimuli:

  • External: Light, Temperature, Sound, Atmospheric Pressure.

  • Internal: Blood pressure, Blood pH, Muscle tension.

Structure of the Human Nervous System

Divisions

• Central Nervous System (CNS): Composed of the brain and spinal cord responsible for integrating and processing information.

• Peripheral Nervous System (PNS): Comprises all nerves outside the CNS, linking CNS to the peripheral receptors and effectors.

Central Nervous System (CNS)

• Comprises interconnected neurons forming:

  • Brain: Conducts higher-order functions like movement, thought, and emotion.

  • Spinal Cord: Pathway for signals between the brain and body; responsible for reflex actions.

CNS Protection

• Surrounded by meninges (three protective membranes) and cerebrospinal fluid (cushioning fluid).

• Enclosed within the cranium (for the brain) and vertebral column (for the spinal cord).

Structures of CNS

• Cranium: Bone structure protecting the brain. Comprised of 8 skull bones interconnected.

• Vertebral Column: 33 vertebrae safeguard the spinal cord.

Brain Structure

• Located in the cranial cavity, resembles a mushroom (cerebrum as the cap, brainstem as the stalk) with the cerebellum at the back.

Brain Functionality

Lobes of the Brain

1. Frontal Lobe: Decision making, movement, and complex behavior.

2. Parietal Lobe: Processes sensory information; involved in perceptions.

3. Occipital Lobe: Visual processing.

4. Temporal Lobe: Memory, understanding, and language.

Functions of Each Lobe

• Frontal Lobe: Higher reasoning, planning, voluntary movements.

• Parietal Lobe: Manages sensory input, spatial orientation.

• Temporal Lobe: Responsible for auditory information, language comprehension.

• Occipital Lobe: Vision processing; visual memory.

Cerebral Cortex

• Outermost layer made of gray matter, responsible for processing information, including sensory and motor tasks.

White Matter & Gray Matter

• Gray Matter: Contains neuron cell bodies.

• White Matter: Composed of myelinated axons facilitating communication between different brain areas.

Neurotransmission

Synapses

• Neurons do not touch; separated by synaptic clefts.

• Neurotransmitters released from axon terminals carry signals across the synapse to the next neuron or muscle cell.

Importance of Synapses

• Ensures one-way transmission of impulses; disperses signals to multiple neurons; filters out unnecessary stimuli (e.g., sensation of clothes on skin).

Reflex Actions

• Reflex Arc: Pathway for reflex actions consisting of:

  • Receptor

  • Sensory Neuron

  • Connector Neuron

  • Motor Neuron

  • Effector

• Reflexes allow quick responses, often bypassing the brain for immediate action (e.g., pulling away from a hot surface).

Types of Reflexes

• Somatic Reflexes: Activate skeletal muscles.

• Autonomic Reflexes: Influence smooth and cardiac muscles and glands.

Disorders and Treatments

• Explore the effects of drugs on the CNS and investigate nervous system disorders as mentioned in assigned reading activities.