2.82 Communication

describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems

1. Nerves (Motor nerves)

Electrical impulse = nerve impulse

Carried down inside the nerve from the cell body [spine] to the synaptic knob [muscle/effector] through the axon

Axons are surrounded by Schwann cells

Schwann cells contain fat and form a myelin sheet (increases the speed of nerve conduction)

Source: http://www.wikimedia.org

==

2. Endocrine system

Endocrine gland (produces hormones; proteins or steroids)

e.g. Adrenal gland

Hormone is secreted into blood

e.g. Adrenaline into the blood

Sent to target tissue

e.g. Adrenaline sent to heart

Hormones can have multiple targets and multiple effects

==

3. Communication using nerves vs hormones

Nerves

- Fast

- Electrical impulses

- Travel through nerves

- Impulses only last a short time

Hormones

- Relatively slow

- Chemical messengers

- Travel through bloodstream

- Effects last longer