Human Nervous System PDF

HUMAN NERVOUS SYSTEM  The Nervous System The body system that primarily functions for control and regulation of body activities and processes together with the endocrine system. It is made up of: – Brain – Spinal Cord – Neurons / Nerve Cells Functions of the Nervous System...

HUMAN NERVOUS SYSTEM  The Nervous System The body system that primarily functions for control and regulation of body activities and processes together with the endocrine system. It is made up of: – Brain – Spinal Cord – Neurons / Nerve Cells Functions of the Nervous System Gathers information from the inside and outside world. Transmits information to the processing areas. Processes the information to determine the best response. Sends information to the muscles, glands or organs so they can respond correctly. Maintains internal balance (homeostasis). Body Activities or Processes Regulated by the Nervous System Walk Speak Swallow Breathe Learn A person has the ability to control, regulate and coordinate the different body activities and processes. A stimulus is a change in the environment (either external or internal) that is detected by a receptor. Receptors transform environmental stimuli into electrical nerve impulses. Example: A fly was moving toward your eye and you quickly and automatically blink to avoid damage to your eye. Stimulus - fly moving toward you Response - blinking  Reflex Action A reflex action is a way for the body to automatically and rapidly respond to a stimulus to minimize and further damage to the body. It follows this general sequence and does not involve the brain: Stimulus – Receptor – Sensory neuron – Relay neuron – Motor neuron – Effector – Response.  Reflex Action The nerve pathway followed by a reflex action is called a reflex arc. For example, a sample reflex arc happen if we accidentally touch something hot. 1. Receptor in the skin detects a stimulus (change in temperature). 2. Sensory neuron sends impulses to relay neuron. 3. Motor neuron sends impulses to effector. 4. Effector produces a response (muscle contracts to move hand away). Neuron: Basic Unit of the Nervous System  Neuron The basic structural and functional unit of the nervous system. Strings of special cells that carries information in the form of nerve impulses across the nervous system. Unique – Does not reproduce. Once damaged, it can no longer be replaced. NEURON/ NERVE CELL  Parts of a Neuron 1. Dendrites - tiny, thread like structures branching from the cell body that receive and carry information toward the cell body. 2. Cell body - Organizes and keeps the cell functioning.  Parts of a Neuron 3. Nucleus - controls the entire neuron. 4. Axon - long tail like fiber that extends from the cell body that carries information away from the cell body.  Parts of a Neuron Synapse – the junction between two neurons or between a neuron and a muscle, across which nerve impulses are transmitted. FUNCTIONAL CLASSIFICATION OF NEURONS  SENSORY NEURON Afferent neuron Receive initial stimuli from the sense organs. Transmits the impulse to the interneuron. Eventually to the spinal cord and brain.  INTERNEURON Connector neurons or association neuron Read impulses received from the sensory neuron. Located in the brain and spinal cord. Determines if a response is required. Transmits the impulse to the motor neuron.  MOTOR NEURON Efferent neuron Transmits impulses from the brain and spinal cord to muscles, glands or organs to generate the response. (Bipolar) Divisions of the Nervous System  MAJOR DIVISIONS Central Nervous System Peripheral Nervous System  The Central Nervous System Consists of brain and spinal cord Processes the information it receives from the sensory nerves and sends out responding action.  The Brain Control center of the human body. Protected by the skull. Immersed in cerebrospinal fluid which serves as the cushion for the brain. Parts can be grouped into three: – Forebrain – Midbrain – Hindbrain  The Forebrain Cerebrum Thalamus Hypothalamus  Cerebrum –Largest portion of the brain –Sensory functions, intelligence, personality, understanding language –Divided into left and right hemisphere connected by the corpus callosum Four Lobes  Frontal – reasoning, higher order cognition, Parietal – tactile sensory information BRAIN LOBES movement and language Occipital – interpreting visual information Temporal – interpreting sounds and language BRAIN HEMISPHERE  Thalamus – Relay station of the brain. – Directs signals coming from spinal cord to the appropriate area of the brain. – Consciousness, sleep and alertness.  Hypothalamus Internal conditions Portion of the brain that maintains internal balance. (Homeostasis) Link between the nervous and endocrine system Stimulates or inhibits: – Heart rate and blood pressure – Body temperature – Fluid and electrolyte balance, including thirst – Appetite and body weight – Glandular secretions of the stomach and intestines – Production of substances that influence the pituitary gland to release hormones – Sleep cycles  The Midbrain Brain stem – Relays information from the sense organ.  The Hindbrain Cerebellum Pons Medulla Oblongata  The Cerebellum Second largest part Receives information from the sensory systems, spinal cord and Coordinates muscle action and body balance.  The Pons Connects the upper and lower parts of the brain. Aids in relaying information to the different parts of the brain. Pons is Latin for “bridge”  The Medulla Oblongata Involuntary actions like heartbeat, breathing and blood pressure, digestion, swallowing, sneezing. Motor neurons from midbrain and forebrain travel through the medulla  The Spinal Cord It is nerve tissue that is protected by the vertebral column The Spinal Column Also called as backbone Somatic Nervous system Connects the CNS to the voluntary muscles Voluntary action Autonomic Nervous System Connects CNS to the glands, smooth muscles of different internal organs and cardiac muscles. Involuntary action Sympathetic Nervous system Functions when you are stressed afraid or something. Parasympathetic Nervous System returns the body functions to normal and maintains them in level. ( even when sleeping)