Revision: The Immune and Nervous Systems Year 9 Biological Sciences Mrs. Foxbridge

The Immune System The immune system has two parts: The specific Immune System The non-specific immune system

Non-Specific Immunity The non specific immune system is innate and protects you from all pathogens It is made up of 1.Skin 2.Mucous lining our nasal passages and airways 3.An enzyme called lysozyme sound in tears 4.Urine – flushes germs from the bladder 5.Stomach – very acidic – also can include vomiting and diarrhoea to flush out

Specific Immunity Specific Immunity is the bodies next line of defence Involves the recognition of antigens and a reaction to eliminate them There are two main types of cells involves in specific immunity

B-Cells Found outside or between cells Covered in receptors which look for matching antigens Produce antibodies to target to specific antigen Antibodies bind to antigens and destroy them then attract macrophages

Anti-bodies Protein Molecules in a “Y” shape Bind to antigens – hands attach to the antigen and tail attaches to a phagocyte

T-Cells Begin life in the bone tissue and migrate to the thymus gland Attack cells that have become infected They signal the cell to self destruct Stimulate the formation of B-cells Response is not immediate, the body will suffer symptoms of the disease

T-helper cells Secrete cytokines which draw other immune cells to the site of infection – causes swelling and inflammation

Memory Cells Responsible for the bodies immunity

Phagocytosis When a cell engulfs a particle and absorbs it Macrophages are large immune cells that patrol the body for antigens or dead cells to consume Pus forms made of dead pathogens and white blood cells

The Nervous system Allows us to respond to stimuli in a coordinated way There are two main parts of the nervous system

Central Nervous System Consists of the brain and spinal cord

Peripheral Nervous System Consists of nerves that connect the sense organs with the central nervous system

Protection The brain and spinal cord are very well protected by the skull and spinal column The peripheral nervous system has some ability to regenerate The central nervous system cannot regenerate The cells are so specialised that they cannot divide and create new cells

Neurons Neurons – special cells that carry nerve impulses Impulses travel from the central nervous system to the peripheral nervous system or from the peripheral organs to the brain.

Three Types of Neurons 1.Sensory neurons Run from various stimuli receptors ie. Taste, sounds, sight, touch and vision 2. Interneurons Found exclusively in the spinal cord and brain Stimulated by sensory neurons or other interneurons 1.Motor Neurons Transport impulses from the central nervous system to the muscles and glands

Synapses Where the axon terminal ends and stimulates another structure Synapse may be with another neuron or with a muscle fibre or gland

Reflex Arc Receptors (sensitive nerve endings) are stimulated and send a nerve impulse along a sensory neuron to the spinal cord Then a connector neuron is stimulated to carry an impulse to a motor neuron Motor neuron stimulates a muscle or gland

Reflex Arc Response is rapid Does not involve the brain Protects us from injury Examples: blinking, vomiting, sneezing, startling