Biology
Human Nervous System
Human Nervous System
The human nervous system coordinates all involuntary and voluntary actions of the body by sending electrical signals (nerve impulses) to and from parts of the body. The nervous system sends information from the sensory receptors to the brain and spinal cord and sends the responses to the parts of the body. The neurons which are special nervous system cells transmit the nerve impulses.
Parts of the nervous system
• central nervous system (brain and spinal cord)
• peripheral nervous system (nerves that carry impulses to and from central nervous system)
Parts of Brain
• Cerebrum which is largest part of the brain that coordinates movement and regulates temperature. It is the front of brain
• Brainstem which is the middle of the brain connects the cerebrum with the spinal cord
• Cerebellum located at back of head coordinate voluntary muscle movements and helps to maintain posture and balance
Spinal cord
• Spinal cord is nerve tissue that runs from base of skull to centre of the back
• It is covered by membranes
• The vertebrae (back bones) surrounds the spinal cord and membranes
Peripheral nervous system
• The peripheral nervous system connects central nervous system with different parts of the body
• The two types of nerve fibres are afferent nerve fibres and efferent nerve fibres
• Afferent nerve fibres transmits messages from tissues and organs to the central nervous system
• Efferent nerve fibres transmits messages from the central nervous system to the organs
• It is divided into autonomic nervous system and somatic nervous system
• Somatic nervous system control activities under voluntary control
• Autonomic nervous system control activities that are involuntary
Autonomic nervous system
• It is divided into sympathetic nervous system, parasympathetic nervous system and enteric nervous system
• Sympathetic nervous system control fight response requirements. It puts the body systems on alert
• Parasympathetic nervous system controls the routine functions. It relaxes the body systems
• Enteric nervous system control motor functions, endocrine functions, local blood flow etc.
Nervous system signals
• Neurons (nerve cells) transmit the electrical signals (nerve impulses) sent by the nervous system
• Axons (long projections) carry nerve impulses directly to specific cells
• Dendrites (short projections) receive nerve impulses from other cells
• Synapse is the gap between adjacent neurons over which impulses pass between neurons
Diseases or disorders of Nervous System
• Alzheimer’s disease kills brain cells leading to loss of memory
• Cerebral palsy affects movement, balance and posture
• Epilepsy, which is a disorder of the central nervous system, causes seizures due to abnormal brain activity
• Multiple sclerosis, which is a disorder of the central nervous system affects brain or spinal cord
• Parkinson’s disease, which is a disorder of the central nervous system affects movement
• Sciatica, causes pain in the back and in the legs
• Stroke occurs when brains blood vessels get blocked or bursts.