Human nervous system - biology

Function of the nervous system

Allows the body to react to its surroundings and coordinate an appropriate response

How does a stimulus lead to a response being carried out by the body?

• Stimulus is converted into an electrical impulse by the receptors

• The electrical impulse passes along sensory neurons to the CNS

• The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurons to the effector → which carries out the response

Sequence of the nervous system

Stimulus → receptor → coordinator → effector → response

Reflex action

An automatic and rapid response which does not involve any conscious input from the brain

Importance of reflex actions

Aid survival by preventing harm to the body

Describe how a reflex action occurs via a reflex arc

• The stimulus is detected by a receptor

• An electrical impulse passes along a sensory neuron to the spinal cord

• At a synapse between a sensory neuron and a relay neuron, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neuron

• The same process occurs at a synapse between a relay neuron and a motor neuron

• At the effector, an appropriate response is carried out

Reflex pathway

An automatic, involuntary nerve pathway that produces a protective response to a stimulus.

Within a reflex pathway, the coordination centre is a relay neuron found in the spinal cord / unconscious parts of the brain

Conscious pathway

A neural route that transmits information from receptors through the brain stream, resulting in conscious awareness and voluntary action

In a conscious pathway, the coordination centre is in the conscious part of the brain

Function of the cerebral cortex

Controls consciousness, intelligence, memory and language

Function of the cerebellum

Controls muscular coordination

Function of the medulla

Controls unconscious activities (breathing, heart rate)

Why is investigation and treatment of the brain difficult ?

• The brain is a complex and delicate organ

• The brain is easily damaged and destroyed

• Certain membranes prevent drugs from reaching the brain

Methods used to determine brain function

• Studying patients with brain damage

• Electrical stimulation of the brain

• MRI scans