National 5 Biology | Unit 2 | Key Area 2: Control and Communication

The three components of the nervous system are:

The three components of the nervous system are:

Brain, spinal cord and nerves

The central nervous system (CNS) is made up of:

The brain and the spinal cord

What is the brain’s function?

Controls the whole body and coordinates all nerve impulses.

What is the spinal cord’s function?

-Relays impulses between nerves and the brain

-Controls reflex actions

What are the nerves’ function?

Carries impulses to and from the muscles and body organs

The brain is made up of 3 main regions:

Cerebrum, cerebellum, medulla

The cerebrum controls…

Conscious thought, reasoning, memory, action, personality

The cerebellum controls…

Balance, coordination, movement

The medulla controls…

Heart and breathing rate

Nerves

Nerves consist of the fibres of numerous nerve cells (neurons) running alongside each other.

There are three main types of nerve:

Sensory, inter, motor

Sensory neurons pass information from the _____ to the _____.

Senses; CNS

Inter neurons (also known as relay neurons) are located within the _____ and are involved in the flow of information between _____ and _____.

CNS; receptors; effectors

Motor neurons pass response messages from the _____ to the _____ organ.

CNS; effector

Synapse

The tiny space between neurons.

Explain how electrical impulses are passed along synapses:

1. Impulse reaches end of the presynaptic cell (first neuron)

2. Chemical transmitter diffuses across synapse to reach the postsynaptic cell (second neuron)

3. Impulse continues along second neuron

Describe the process of the flow of information:

1. Sense organs detect information from the surroundings (receptors)

2. The stimulus triggers the production of a nerve impulse

3. The impulse passes along a sensory nerve to the CNS

4. The information is processed (involvement of inter neurons)

5. Another impulse is passed along a motor neuron to an effector (eg. muscle)

6. Muscle contracts and responds to the original stimulus

Reflex arcs are very _____ responses that _____ the body from harm. Decisions are made at the level of the _____ _____ and not the _____ because it would take longer to travel.

Rapid; protect; spinal cord; brain

Describe the process of a reflex action:

1. Receptors in the skin detect a stimulus

2. Impulse travels to the CNS (spinal cord) along sensory neuron

3. Information is processed within the inter neuron

4. Impulse travels to an effector along motor neuron

5. Body reacts to original stimulus

Examples of reflex actions are:

-Coughing/sneezing reflex

-Blinking reflex

-Pupil reflex

-Withdrawal reflex

-Swallowing

-Salivation

Hormones are produced by _____ _____ and are carried in the _____. They act _____ than nerves and are useful for _____ sets of conditions over a prolonged period of time.

Endocrine glands; bloodstream; slower; maintaining

Target tissues have specific _____ _____ that only respond to a specific _____, ie. they are complimentary.

Receptor proteins; hormone

Insulin

A hormone secreted by the pancreas to stimulate the liver to convert excess glucose to glycogen.

Glucagon

A hormone secreted by the pancreas to stimulate the liver to convert glycogen to glucose.

Glucose

Glucose is a type of sugar.

Glycogen

Glycogen is a storage carbohydrate that is stored in the liver.

How does the body respond to an increase in blood glucose levels?

1. The pancreas detects a rise in blood glucose levels and secrets insulin

2. Insulin stimulates liver to take up excess glucose and convert it into glycogen

3. Blood glucose levels return to normal

How does the body respond to a decrease in blood glucose levels?

1. The pancreas detects a fall in blood glucose levels and secretes glucagon

2. Glucagon stimulates liver to convert stored glycogen to glucose

3. Blood glucose levels return to normal