The Nervous System
- Central nervous system -->Consists of the brain, spinal chord, linked by nerves
- Uses information from the sensory organs to coordinate reflexes and other actions
- Stimulus --> Receptor --> coordinator --> effector --> response
- An individual nerve cell is a neuron, it responds to a stimuli and can conduct electrical impulses. A bunch of neurons is called a nerve
- Peripheral nervous system --> consists of nerves and nerve networks throughout the body
- The nerve system is actually made up of bundles of axons. The axon is a thread like structure that conducts the electrical impulses and passes them on to other cells or the muscle fibres.
- In a motor neuron the connection between the axon and the muscle fiber is called the nerve-muscle-junction
- One way of connecting the coordinator to the effector is through Schwann Cells. These contain fat that cover the axon, the fat forms the myelin sheath. The Myelin sheath also increases the speed of nerve conduction
The Endocrine System
- Involves the endocrine gland which produces hormones. EG. adrenal gland producing adrenaline and insulin.
- The hormones are secreted into the blood and affect the organs with the correct receptors, sometimes known as the target tissues
The difference between the two
- Nerve system travel along neurons
- Chemical messages travel in the blood
- Hormonal system sends messages slower, Chemical is very fast
- Chemical take longer to have effect
- Sometimes, chemical effects are widespread throughout the body, unlike nerves
- Chemical effects last long
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