Nervous system Afraa,Sa7ab,Hind,Layla
The brain maintains homeostasis and is involved with almost all of the body’s activities. It is made up of 3 parts and a gland:
1- Cerebrum: Is the largest part of the brain and is divided into two halves called hemispheres. The cerebrum carries out thought processes involved with learning, memory, language, speech, voluntary body movements, and sensory perception The folds and grooves on the surface of the cerebrum increase the surface area and allow more complicated thought processes.
2- Cerebellum: Controls balance, posture, and coordination, and is located at the back of the brain. The cerebellum is responsible for the smooth and coordinated movement of skeletal muscles and is also involved with motor skills.
3- Brain stem: It connects the brain to the spinal cord and is made up of two regions that are:
3.1- Medulla oblongata: Relays signals between the brain and the spinal cord. It also helps control breathing rate, heart rate, and blood pressure. It contains the interneurons responsible for reflexes such as swallowing, gagging, vomiting, coughing, and sneezing.
3.2- Pons: Relays signals between the cerebrum and the cerebellum. They also help control the rate of breathing.
4- Hypothalamus: A gland that regulates body temperature, thirst, appetite, and water balance. It also partially regulates blood pressure, sleep, aggression, fear, and sexual behavior. It is about the size of a fingernail.
Types of neurons
It receive impulses from receptors in the skin and sense organs and send it to the brain and spinal cord.
Is a link between sensory and motor neurons and found in in the spinal cord and brain.
Which carries impulses or signals away from the brain and spinal cord to a gland or muscle, which results in secretion or movement.
The peripheral nervous system (PNS): consists of the sensory neurons and motor neurons that carry information to and from
The autonomic nervous system carries impulses from the central nervous sys- tem to the heart and other internal organs.
When you have a night- mare or find yourself in a scary situation, your body responds with what is known as a fight-or-flight response. When everything is calm, your body rests and digests.
The sympathetic nervous system is most active in times of emergency or stress, when the heart rate and breathing rate increase.
The parasympathetic nervous system is most active when the body is relaxed. It counterbalances the effects of the sympathetic system and restores the body to a resting state after a stress- ful experience.
The somatic nervous system relay information from external sensory receptors to the central nervous system. Somatic motor nerves relay information from the central nervous system to skeletal muscles
Not all reactions of the central nervous system are voluntary
Some responses are the result of a reflex which is a fast response to a change in the environment. Most signals in reflexes go only to the spinal cord and not the brain.
The interneurons of the brain and the spinal cord make up the central nervous system (CNS).
the coordination of all the body’s activi-
ties. It relays messages, processes information, and analyzes responses.
When sensory neurons carry information about the environment to the spinal cord, interneurons might respond via a reflex arc