Biological Reasons for Behaviour

• Interoception = detecting changes in the body and organs.
• Chemoreceptors can detect chemical changes (CO2; nutrients; hormones) in body fluids.
• Mechanoreceptors are specialized neurons that are sensitive to mechanical deformation.
• Mechanoreceptors are found throughout the entire respiratory tract. They supply the brain with information about the mechanical status of the lungs and chest, contribute to the control of respiratory activity, and initiate protective reflexes such as cough.
• Chemoreceptors in the carotid blood vessels and in the brain increase firing rate in response to build up of CO2 which neuronal activity that increases ventilation that reduces CO2.
• Exteroception = detecting changes in the external environment.
• A stimulus (stimuli plural) causes a response or reaction in an animal. This does not require conscious thought.
• Olfactory nerves or olfactory receptor neurons (OFN) aid in chemoreception. Humans have 10-20 million which are bipolar. The surface of OFNs are covered with olfactory receptors which bind to chemicals entering the nose.
• Gustation is the action of taste. The tongue is the taste organ in vertebrates. It is covered with taste buds that can distinguish between 5 modalities. Taste bud receptors have similar physiology to olfactory neurones.
• Afferent nerves go to the brain. Efferent nerves go away from the brain.
• Sound vibrations are mechanically conducted from the eardrum through a series of tiny bones to the inner ear. The cochlea in the inner ear has over 30,000 hair cells that detect those vibrations and excite the nerve fibres of the cochlear or auditory nerve.
• Visible light is part of the electromagnetic spectrum. Photoreceptors are sensitive to photons in a reversible way. Rods are sensitive to very low light levels and have one photopigment to generate black and white vision. Cones are sensitive to high light levels and can have different photopigments hence they can generate colour vision.
• Sensation: The basic data from the senses e.g. the neural signals that emerge from chemoreceptors.
• Perception: The process of interpreting sensory information unconsciously and consciously.