the nervous system

• the nervous system is consisted of the central nervous system and the peripheral nervous system
• in the central nervous system there is the spinal cord and the brain
• in the peripheral nervous system there is the somatic nervous system and the autonomic nervous system, the autonomic nervous system then branches off into the sympathetic nervous system and the parasympathetic nervous system
• CNS: the CNS comprising of the brain and spinal cord has 2 main functions the control of behaviour and the regulation of the body's physiological processes
• CNS: in order to do this the brain must be able to receive information from the sensory receptors (eyes, ears, skin etc.) and be able to send messages to the muscles and glands of the body
• CNS: this involves the spinal cord a collection of nerve cells that are attached to the brain and run the length of the spinal column
• the spinal cord: the main function of the spinal cord is to relay information between the brain and the rest of the body
• the spinal cord: this allows the brain to monitor and regulate bodily processes such as digestion, breathing and coordinate voluntary movements
• the spinal cord: the spinal cord is connected to different parts of the body by pairs of spinal nerves which connect w/ specific muscles and glands
• the spinal cord: e.g. spinal nerves which branch off from the thoracic region of the spinal cord carry messages to and from the chest and parts of the abdomen
• the spinal cord: the spinal cord also contains circuits of nerve cells that enable us to perform some simple reflexes w/o direct involvement of the brain e.g. pulling your hand away from something that is hot
• the spinal cord: if the spinal cord is damaged areas supplied by spinal nerves below the damaged site will be cut off from the brain and will stop functioning
• the peripheral nervous system comprises the nerves leading to and from the CNS
• the brain: the brain can be divided into 4 main areas = the cerebrum, cerebellum, diencephalon and brain stem
• the brain: the cerebrum is the largest part of the brain and is further divided into 4 different lobes each of which has a different primary function e.g. the frontal lobe is involved in thought and the production of speech and the occipital lobe is involved in the processing of visual images
• the brain: the cerebrum is split down the middle into 2 halves called cerebral hemispheres
• the brain: each hemisphere is specialised for particular behaviours and the 2 halves communicate w/ each other through the corpus callosum
• the brain: the cerebellum sits beneath the back of the cerebrum, it is involved in controlling a person's motor skills and balance, coordinating the muscles to allow precise movements
• the brain: abnormalities of the cerebellum can result in a number of problems including speech and motor problems and epilepsy
• the brain: the diencephalon lies beneath the cerebrum and on top of the brain stem, within this area are 2 important structures = the thalamus and the hypothalamus
• the brain: the thalamus acts as a relay station for nerve impulses coming from the senses routing them to the appropriate part of the brain where they can be processed
• the brain: the hypothalamus has a number of important functions including the regulation of body temperature, hunger and thirst, it also acts as the link between the endocrine system and the nervous system controlling the release of hormones from the pituitary gland
• the brain: the brain stem is responsible for regulating the automatic functions that are essential for life, these include breathing, heartbeat and swallowing
• the brain: motor and sensory neurons travel through the brain stem allowing impulses to pass between the brain and the spinal cord
• PNS: all the nerves outside the CNS make up the peripheral nervous system
• PNS: the function of this part of the nervous system is to relay nerve impulses from the CNS (brain and the spinal cord) to the rest of the body and from the body back to the CNS
• PNS: there are 2 main divisions of the peripheral nervous system the somatic nervous system and the autonomic nervous system
• the somatic nervous system: the somatic nervous system is made up of 12 pairs of cranial nerves (nerves that emerge directly from the underside of the brain) and 31 pairs of spinal nerves (nerves that emerge from the spinal cord), these nerves have both sensory neurons and motor neurons
• the somatic nervous system: sensory neurons relay messages to the CNS and motor neurons relay information from the CNS to other areas of the body
• the somatic nervous system: the somatic system is also involved in reflex actions w/o the involvement of the CNS which allows the reflex to occur very quickly
• the autonomic nervous system: when you type on a keyboard or take a drink you are performing voluntary actions and are conscious of what you are doing
• the autonomic nervous system: however the body also carries out some actions w/o your conscious awareness e.g. your heart beats and your intestines digest food w/o you being consciously aware of this happening
• the autonomic nervous system: involuntary actions such as these are regulated by the ANS
• the autonomic nervous system: this system is necessary because vital bodily functions such as heartbeat and digestion would not work so efficiently if you had to think about them
• the autonomic nervous system: the ANS has 2 parts = the sympathetic and the parasympathetic, both of these divisions tend to regulate the same organs but have opposite effects this is because of the neurotransmitters associated w/ each division
• the autonomic nervous system: generally the sympathetic division uses the neurotransmitter noradrenaline which has stimulating effects and the parasympathetic division uses acetylcholine which has inhibiting effects
• the sympathetic nervous system: the sympathetic nervous system is primarily involved in responses that helps us to deal w/ emergencies (fight or flight) such as increasing heart rate, blood pressure and dilating blood vessels in the muscles
• the sympathetic nervous system: neurons from the SNS travel to virtually every organ and gland within the body preparing the body for the rapid action necessary when the person is under threat
• the sympathetic nervous system: e.g. SNS causes the body to release stored energy, pupils dilate and hair to stand on end, it slows bodily processes that are less important in emergencies such as digestion and urination
• effect of SNS activation on the body: increased pupil size lets in more light for better vision, increase in heart rate allows for greater flow to skeletal muscles, glycogen stored in the liver is converted to glucose for energy, bronchial tubes in lungs dilate for greater oxygen intake, sweat glands stimulated to produce more sweat, adrenal medulla stimulated to release adrenaline