Unit 4: The interaction function
- Interaction in humans
The interaction function allows humans to detect and respond to changes in the environment
1.1. Perceiving of stimuli
It is carried out by cells called receptors which specialise in detecting changes (detect physical and chemical changes in the environment and send this information to the coordination centres)
1.2. Generating responses
It is carried out by the coordination centres. They analyse the information received by the receptors and generate a response to send to the effector organs
1.3. Executing responses
The nervous system is made up of a network of organs which send responses to the effector organs in the form of nerve impulses
The endocrine system is made up of a network of organs called endocrine glands. These send responses to the effector organs through the blood in the form of chemical substances called hormones
The effector organs is to execute responses
Muscles: When they receive a command, via nerve impulse, they can carry out voluntary or involuntary movements
Glands: Synthesise and release substances
Stimuli
are perceived by
The receptors
which send messages to
The coordination systems
such as
The nervous system
which generates commands in the form of electrical impulses and sends them to
The effectors
such as
The muscles and the bones
which execute
The responses
- Nervous coordination
It is carried out by the nervous system. This system is made up of nervous tissue containing cells called neurons which are capable of transmitting information through nerve impulses
6.1. Cells of the nervous system
Neurons are the structural and functional units of the nervous system. They are very diverse and have a complex morphology
The cell body houses the nucleus and the cytoplasmic organelles, which have short branching extensions called dendrites. One end of the cell body has a single and much longer extension called axon, which has wider endings callled axon terminals.
Axons of various neurons group together to make up nerve fibres, some of which in turn group together to form nerves
Types of neurons
Sensory neurons are connected via their dendrites to a receptor
Motor neurons are connected via their axon to an effector organ
Intermediate or associative neurons connect the sensory and motor neurons
In nervous tissue the neurons are accompanied by glial cells which are responsible for neuron nutrition, defence and support
Nerve impulses
Neurons can transmit information in the form of electrochemical messages called nerve impulses. The gap between each neuron (synaptic cleft). The transmitter neuron releases substances called neurotransmitters which reach the membrane of the receptor neuron and generate the same impulse there
6.2. The nervous system
Is a network of neurons which interprets messages or stimuli sent by the sense organs and generates commands which tell the effector organs how to respond. It is made up of the CNS and the PNS
6.3. The central nervous system
It coordinates all the functions of the body
The encephalon
It is protected by the skull and three membranes (meninges), between which circulates the cerebrospinal fluid
The brain: It is divided into 2 hemispheres. Its surface is the cerebral cortex and has folds and furrows called circumvolutions. It converts information into awareness and is responsible for advanced functions (memory, intelligence and will)
The cerebellum: has 2 hemispheres and a folded cortex. It is responsible for balance and pre-learnt voluntary movements (walking, writing, playing an instrument)
The brainstem: links the encephalon to the spinal cord and controls a range of involuntary functions
The spinal cord
It is a long bundle of nerves protected by the spine and connects the encephalon with the rest of the body. It coordinates simple responses calles reflex actions
6.4. The peripheral nervous system
It is made up of nerves which connect the CNS to the body's organs