Unit 5.4 Exploring the Nervous System

How is the nervous system related to both internal and eternal?

The nervous system senses the external environment then acts to restore optimal internal conditions

What is the “definition” of the nervous system?

“Specialized organ system that connects the external environment to the internal environment and helps maintain homeostasis

What kinds of things does the nervous system sense?

Depth of breathing, pressure on skin, temperature, light, odour

What two types of movements does the nervous system control?

Unconscious and conscious

Give an example of unconscious movements

Blinking, breathing

Give an example of a conscious movement

Scratching an itch

Besides breathing, scratching, what are more complicated functions the nervous system controls?

Memory, thought, language

Name the 2 main divisions of the nervous system

1. Central nervous system

2. Peripheral nervous system

What parts of the body make up the central nervous system? What is the function of the CNS?

Brain and spinal cord; it is the coordinating centre for incoming and outgoing information

What parts of the body make up the peripheral nervous system? What is the function of the PNS?

Nerves; carries information between the CNS and the organs

The peripheral nervous system is further subdivided into what 2 divisions?

1. Somatic nervous system

2. Autonomic nervous system

The somatic nervous system of the PNS consists of what parts of the body?

Skeletal muscles, bones, skin, sensory nerves, motor nerves

The autonomic nervous system of the PNS controls what parts of the body?

The internal organs

The autonomic nervous system of the PNS is further subdivided into 2 divisions. Name them

1. Sympathetic nervous system (“fight or flight”)

2. Parasympathetic nervous system (“rest and digest”)

Name the 2 types of nerve cells

1. Glial cells

2. Neurons

Are glial cells conducting or non-conducting?

Non-conducting

What is the function of glial cells?

To provide structural support

What is an example of a glial cells and how does it function?

Myelin sheath surrounds nerves like insulation, ensures efficient transmission of electric charge

Neurons are the _____ of the nervous system

Functional units

Name the 3 types of neurons

1. Sensory neurons

2. Interneurons

3. Motor neurons

Define sensory neurons. Describe them physically

Sense and relay information from the environment to the CNS for processing; located in clusters and ganglia

Define interneurons. Where are they mostly found?

Neurons that link neurons. Integrate and interpret the sensory information and connect neurons to outgoing motor neurons; found in the brain and spinal cord

What is another name for motor neurons?

Efferent neurons

Define motor neurons

Neurons that send information to the “effectors” meaning the muscles/organs/glands

Name the 3 main parts of a neuron

1. Dendrites

2. Cell body

3. Axon

Define dendrites

Part of the neuron that receives information from sensory receptors or other nerve cells. Conducts nerve impulses toward the cell body

Define cell body

Part of the neuron that contains the nucleus and the majority of the cytoplasm

Define axon

Extension of the neuron that carries nerve impulses away from the cells body towards other neurons or effectors.

The axon is thin and is covered in what? Why?

Myelin sheath; for insulation to prevent the loss of charges ions from the nerve cell

The axon is formed by glial cells called ______

Schwann cells

The areas between the sections of myelin sheath are called _____

The nodes of Ranvier

What happens with these nodes?

Nerve impulses jump from node to node which speeds up the conduction process

Which is faster for conduction- myelinated or non-myelinated?

Myelinated

How are neural circuits made?

Created when nerves communicate

Are neural circuits simple or complex?

Both!

What is a reflex? Give an example

When an action must be immediate without thinking. Occurs even before the brain gets the message; touching a hot stove

What is a reflex arc?

A neural circuit that runs through the spinal cord and provides a way for a reflex action to occur

What are the 5 steps (with arrows) of a reflex arc?

Stimulus → Sensory neuron → Interneuron → Motor neuron → Response

After the stimulus of burning your hand, describe the 4 steps in more detail

1. Heat triggers sensory receptors in the skin. Sends to the spinal cord

2. Interneurons in the spinal cord receive the information and immediately send a signal to the motor neurons

3. Motor neurons activate an effector organ (i.e. muscles)

4. Effector organ causes an immediate response (i.e. pulling your hand away)

Are reflex arcs voluntary or involuntary?

Involuntary

What is the “definition” of nerve impulses?

“Nerve impulses are electrochemical messages created by the movement of ions through the nerve cell membrane”

What is a more basic definition of nerve impulse?

An electrical current, generated in the nerves and muscles, that is carried through the body in nerve impulses that travel along neurons

When a nerve gets stimulated, what changes?

A rapid change occurs in the electrical potential difference across the nerve membrane