Nervous system

• The nervous system controls and coordinates movement, interaction with surroundings through receptors and effectors, and autonomic functions of the body
• The brain is compared to a computer, receiving, translating, and sending messages; the nervous system is described as a mass system of information highways
• The Central Nervous System (CNS) is made up of the brain and spinal cord, controlling body systems, processing memories, while the Peripheral Nervous System (PNS) consists of neurons connecting the CNS to the rest of the body
• In the nervous system, sensory neurons carry nerve impulses towards the CNS, while motor neurons send impulses to effector organs like muscles or glands
• Neurons include sensory neurons that take messages TO the CNS and brain, motor neurons that send messages FROM the CNS and brain to effectors, and interneurons that connect spinal motor and sensory neurons
• Motor neurons carry electrical signals away from the CNS to organs like the heart, blood vessels, and muscles for movement
• The myelin sheath is an insulating layer allowing quick transmission of electrical impulses along nerve cells, while nodes of Ranvier speed up the impulse
• Axon terminals are where the electrical impulse travels and leaves to reach the next neuron's dendrites, crossing a gap called the synaptic gap
• In synaptic transmission, a chemical called neurotransmitter acts as a bridge for the message to pass across the synaptic gap to the next neuron
• Nerve impulses involve a rapid change in membrane potential, known as an action potential, which is propagated along the axon as a nerve impulse
• Motor neurons are myelinated, allowing the action potential to jump from one node of Ranvier to the next, making the propagation of the nerve impulse faster
• Connections between neurons at synapses involve the transmission of nerve impulses by neurotransmitters due to the gap between neurons
• Motor neurones are known as myelinated because they have a myelin sheath
• In myelinated neurones, the action potential jumps from one node of Ranvier to the next, making propagation of the nerve impulse much faster
• Connections between neurones are known as synapses
• Electrical transmissions of the nerve impulse across a synapse are not possible because there is a gap between the neurones
• The nerve impulse is carried across the synapse by chemicals known as neurotransmitters
• The synaptic knob makes a connection with a muscle or another neurone
• When the nerve impulse arrives at the synaptic knob, it causes the release of neurotransmitters from membrane-bound vesicles
• The most common neurotransmitter is acetylcholine, which diffuses across the synaptic cleft and then binds to receptors on the membrane of the muscle or next neurone
• If enough neurotransmitter binds, then the post-synaptic membrane will become depolarised and a new nerve impulse will be generated in the next neurone
• The cerebellum coordinates muscle actions for smooth body movement and voluntary actions
• The medulla oblongata, located at the bottom-most part of the brain, controls vital processes like heartbeat, breathing, and blood pressure
• The somatic nervous system consists of nerves that go to the skin and muscles and is involved in conscious activities
• The autonomic nervous system consists of nerves that connect the CNS to visceral organs such as the heart, stomach, and intestines, responsible for unconscious activities
• Parasympathetic system: relax, calm down, sleep; sympathetic system: alert, prepared, stressed
• The hypothalamus receives messages via its receptors and secretes the hormone Corticotropin-releasing hormone (CRH) in response to stimuli
• The pituitary gland receives messages and sends ACTH, adrenocorticotropic hormone, which activates other hormones like adrenaline and cortisol
• Adrenaline prepares the body for flight or rest by triggering various responses, while cortisol speeds up energy release
• Long-term stress can lead to exhaustion due to continuous production of adrenaline, and cortisol can cause gastrointestinal problems and suppress the immune system