B1.6 Nervous System and Hormones Flashcards
Nervous system
The network of nerve cells and fibres that transmits nerve impulses between parts of the body
Neurones
Basic cells of the nervous system that carry electrical impulses around the body
Electrical impulses
The impulses or signals that are carried by neurones
Central nervous system (CNS)
Brain and spinal cord
Stimulus
A change in an organism’s surroundings
Receptors
Special structures that allow living organisms to sense the conditions of their internal or external environment
Sense organs
Clusters of receptor cells that respond to specific stimuli such as light, sound, touch, temperature, chemicals and then relay this information as electrical impulses along neurones to the central nervous system
Sensory neurone
A neurone that carries impulses from the sensory organs to the central nervous system
Coordinator
The central nervous system which formulates a response to a stimulus before sending impulses to an effector
Motor neurone
A neurone that sends impulses from the CNS to an effector
Effector
A structure that acts in response to a stimulus such as muscles which contract or glands which secrete hormones
Response
A reaction to a stimulus
Reflex arc
A shorter nerve pathway involved in a reflex action made up of a sensory neurone, relay neurone and a motor neurone
Association neurone
A short type of neurone that is involved in reflex actions and is found in the spinal cord
Reflex response
A quick and involuntary reaction to a stimulus such as moving a hand away from a hot object, blinking or pupil size adjusting in response to light changes
Voluntary versus reflex responses
Voluntary responses are conscious and involve the brain, reflex responses are not conscious and are much quicker than voluntary responses
Nature of message for the hormonal (endocrine) system
Chemical messengers known as hormones
Nature of message for the nervous system
Electrical impulses or signals known as nerve impulses
How hormones are transmitted
Hormones are secreted by specialised tissues and organs called glands, the hormones travel around the blood and reach many organs but only have an effect on target organs, which causes them to create a response
How nerve impulses are transmitted
Nerve impulses begin at receptor cells which pass on the electrical impulses across a series of nerve cells (called neurones) before reaching the brain or spinal cord, new impulses are then transmitted from the brain to target effectors to create a response
Duration of effect and speed of hormones
Hormones are much slower than nerve impulses but last for a very long time
Duration of effect and speed of nerve impulses
Nerve impulses travel incredibly fast but are relatively short-lived
