Mammals have two communication systems that work together to coordinate responses: the nervous system and the endocrine (hormonal) system.Comparing the two systems
• Signal: the nervous system uses electrical impulses (action potentials) along neurones, with neurotransmitters at synapses; the endocrine system uses chemical signals, hormones, carried in the blood.
• Speed: nervous responses are very rapid; hormonal responses are usually slower.
• Duration: nervous responses are short-lived; hormonal effects are often long-lasting.
• Target: impulses go to specific cells, giving a localised response; hormones travel all around the body but affect only target cells with complementary receptors, often giving a widespread response.
• Permanence: nervous effects are usually temporary and reversible; hormones can cause permanent changes, such as growth.Working together
The hypothalamus links the two systems. In the fight or flight response it uses both: sympathetic neurones give an immediate response, while hormones such as adrenaline and corticosteroids spread the response through the body and keep it going.The nervous system also controls hormone release. The adrenal medulla is stimulated directly by sympathetic neurones, so adrenaline is released within seconds. The hypothalamus controls the anterior pituitary by releasing factors into the blood, and controls the posterior pituitary through neurosecretory cells.The combined response is both fast and long-lasting. For example, heart rate is first increased by impulses along the accelerator nerve and is then kept high by adrenaline in the blood.
• Signal: the nervous system uses electrical impulses (action potentials) along neurones, with neurotransmitters at synapses; the endocrine system uses chemical signals, hormones, carried in the blood.
• Speed: nervous responses are very rapid; hormonal responses are usually slower.
• Duration: nervous responses are short-lived; hormonal effects are often long-lasting.
• Target: impulses go to specific cells, giving a localised response; hormones travel all around the body but affect only target cells with complementary receptors, often giving a widespread response.
• Permanence: nervous effects are usually temporary and reversible; hormones can cause permanent changes, such as growth.Working together
The hypothalamus links the two systems. In the fight or flight response it uses both: sympathetic neurones give an immediate response, while hormones such as adrenaline and corticosteroids spread the response through the body and keep it going.The nervous system also controls hormone release. The adrenal medulla is stimulated directly by sympathetic neurones, so adrenaline is released within seconds. The hypothalamus controls the anterior pituitary by releasing factors into the blood, and controls the posterior pituitary through neurosecretory cells.The combined response is both fast and long-lasting. For example, heart rate is first increased by impulses along the accelerator nerve and is then kept high by adrenaline in the blood.