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Nervous system (Homeostasis (Regulating body temperature (The human body…
Nervous system
Homeostasis
The conditions inside our body must be very carefully controlled if the body is to function effectively. Homeostasis is the maintenance of a constant internal environment. The nervous system and hormones are responsible for this.
Body temperature
This is controlled to maintain the temperature at which the body’s enzymes work best, which is usually 37°C.
Blood sugar level
This is controlled to provide cells with a constant supply of glucose for respiration. It is controlled by the release and storage of glucose, which is in turn controlled by insulin
Water content
This is controlled to protect cells by stopping too much water from entering or leaving them. Water content is controlled by water loss from:
the lungs - when we exhale
the skin - by sweating
the body - in urine produced by the kidneys
Negative feedback
Homeostatic control is achieved using negative feedback mechanisms:
if the level of something rises, control systems reduce it again
if the level of something falls, control systems raise it again
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Nerve cells
Nerve cells are also called neurones. They are adapted to carry electrical impulses from one place to another
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Receptors to effectors
Receptors
Receptors are groups of specialised cells. They can detect a change in the environment (stimulus) and produce electrical impulses in response. Sense organs contain groups of receptors that respond to specific stimuli.
Effectors
Effectors are parts of the body - such as muscles and glands - that produce a response to a detected stimulus. For example:
a muscle contracting to move an arm
muscle squeezing saliva from the salivary gland
a gland releasing a hormone into the blood
Reflex actions
A reflex action is a way for the body to automatically and rapidly respond to a stimulus to minimise any further damage to the body. It follows this general sequence and does not involve the brain:
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The nerve pathway followed by a reflex action is called a reflex arc. For example, a simple reflex arc happens if we accidentally touch something hot.
Receptor in the skin detects a stimulus (the change in temperature).
Sensory neurone sends impulses to relay neurone.
Motor neurone sends impulses to effector.
Effector produces a response (muscle contracts to move hand away).
The human nervous system consists of:
the central nervous system (CNS) – the brain and spinal cord
the peripheral nervous system – nerve cells that carry information to or from the CNS