Nerves and the brain

Nerve A nerve is a bundle of axons or neuronal fibres bound together like wires in a cable. Neurons or nerve cells are the functional units of the nervous system. They are specialized cells that transmit signals from one location in the body to another location by electrochemical changes in their membranes.

Nerve Neurone consists of three main parts:  Cell body - contains the nucleus and other cell organelles. High level of cellular activity - means there is a large amount of endoplasmic reticulum - secretes protein visible in cytoplasm  Dendrites - pick up messages using their extensive branches to increase the surface area of the ‘receiving end’ of the nerve cell  Axon - conducts messages away from the cell body. The axon has many vertebrates surrounded by schwann cells (supporting cell that forms insulating layer of myelin sheath)

Areas of the cerebrum involved in the perception and interpretation of light and sound Refer to the diagram of the cerebrum  Parietal lobe - at the top of the head towards the back - this area is important for interpreting sensory signals including sight and sound  Occipital lobe - located at the back of the head - concerned with vision as well as perception such as touch, pressure temperature and pain - site of visual cortex  Temporal lobe - located at the side of the head above the ears - interprets the impulses from the ears and give meaning to information - important region for the sense of hearing.

Using specific examples, the importance of correct interpretation of sensory signals by the brain for the coordination of animal behaviour The environment in which an organism lives is constantly changing. Sense organs such as the ear and the eye detect these changes and send information to the brain. The brain then interprets the information and sends an impulse to an effector organ such as a muscle. It is essential that the brain interpret signals from the sense organs correctly. The cerebral cortex is the most important association centre of the brain. Information comes to this area from our senses and the brain sorts it out in the light of past experiences. As a result, motor impulses are sent along the nerves to cause an appropriate action to take place.

Using specific examples, the importance of correct interpretation of sensory signals by the brain for the coordination of animal behaviour For example, the eyes and ears, receptors in muscles and tendons, pressure sensors on the feet all provide signals about the position of the body in space. The cerebrum of the brain interprets all of these signals and sends messages to various effectors to balance the body in space. Walking involves several receptors, including the eyes, gravity receptors in the ears, pressure sensors in the feet and position receptors in the joints. These receptors are connected to the brain by neurones and the brain interprets the signals it receives. The brain sends messages to the muscles and other effectors to coordinate the process of walking. The importance of the brain in the coordination of animal behaviour is highlighted when parts of it are damaged. The paralysis that follows a stroke, or the shaking movements of people with Parkinson’s disease, are signs of damage to the brain. In people with these conditions, muscular contractions are no longer coordinated by the brain