Nervous System

Nervous System

Prepared By: Maria Johanna Baguio Testa

Nervous System

Nervous System helps detect changes from inside the body and outside the environment and generate responses to the changes.

It controls the functions of other organs in our body system too.

Two components of nervous system:

• Central nervous system (CNS)
• Peripheral nervous system (PNS)

The central nervous system consists of:

• Brain
• Spinal cord

The peripheral nervous system consists of:

• Spinal nerves
• Cranial nerves

Central Nervous System (CNS)

The brain is encased in the bony skull, which protects it from injuries. It consists of the cerebrum, cerebellum, medulla oblongata, thalamus and hypothalamus.

The cerebrum is the largest part of the brain. It is the center for thinking, reasoning, speech and memory. It also initiates and controls all voluntary actions like walking, writing and jumping.

The cerebellum is located below the cerebrum near the top of the spinal cord. It coordinates body movements and maintains the body balance.

The medulla oblongata controls and coordinates all involuntary actions such as digestion, respiration and the beating of the heart.

The hypothalamus plays an important role in homeostasis regulation. It controls the body temperature, osmoregulation, sexual function, thirst, hunger, emotional activity and sleep.

The thalamus is responsible for the incoming and outgoing information in the brain.

The spinal cord is continuous with the brain and emerges from an opening at the base of the skull. The spinal cord is protected by the spinal column.

Peripheral Nervous System

The spinal nerves emerge at intervals along the spinal cord. The cranial nerves emerge from the brain.

What Does the Peripheral Nervous System Do?

• Connects the central nervous system to the organs, limbs, and skin

• Carries sensory and motor information to and from the central nervous system

• Allows the brain and spinal cord to receive and send information to other areas of the body

• Regulates involuntary body functions like heartbeat and breathing

Neuron

A neuron transmits information in the form of an electrical charges.

Axon - The long fiber that conducts impulses away from the cell body.

Dendron - The short fiber that conducts impulses towards the cell body.

Dendrites - The terminal branches found at the end of the axons and dendrons which receive or transmit impulses.

Myelin sheath - The layer of fatty substance surrounding the axons or dendrons that serves as an insulating layer.

Node of Ranvier - The intervals along the axon without myelin sheath that help to speed up the transmission of impulses.

Types of Neuron

• Sensory Neuron
• Interneuron
• Motor Neuron

Pathway of Transmission of Information

When a receptor (e.g., an eye) detects a stimulus (e.g., light), it generates nerve impulses. These impulses travel along the sensory neuron to the central nervous system (CNS).

The CNS processes the information and relays impulses via the interneuron to the motor neuron. The motor neuron then transmits the impulses to an effector (e.g., a muscle), which produces a response (e.g., moving a hand).

Key Components:

1. Stimulus (e.g., light)

2. Receptor (e.g., eye)

3. Sensory neuron (transmits impulses to CNS)

4. Central nervous system (interprets impulses)

5. Interneuron (relays within CNS)

6. Motor neuron (sends impulses to effector)

7. Effector (e.g., muscle/gland; executes response)

8. Flow of impulse (directional pathway)

Example:

• Stimulus → Receptor → Sensory neuron → CNS → Interneuron → Motor neuron → Effector → Response

For body coordination to take place, there must be:

• Stimulus (ex. Mosquito, hungry) 
• Receptor to pick up the stimulus (sensory neurons)
• An effector to carry out the response.

Pathway of Transmission of Information

Conceptual Map

END