Nervous System PDF

NERVOUS SYSTEM  NERVOUS SYSTEM → The master controlling and communicating system of the body → Every thought, action, and emotion reflects its activity → Its cells communicate by electrical and chemical signals, which are rapid and specific, and usually cause almost immedia...

NERVOUS SYSTEM  NERVOUS SYSTEM → The master controlling and communicating system of the body → Every thought, action, and emotion reflects its activity → Its cells communicate by electrical and chemical signals, which are rapid and specific, and usually cause almost immediate responses It is divided into two principal parts 1. Central Nervous System 2. Peripheral Nervous System  FUNCTIONS OF THE NERVOUS SYSTEM 1. Sensory input (Receptor) → Sensory receptors monitor changes occurring inside and outside the body 2. Integration (Control System) → Processes and interprets sensory input and decides what should be done at each moment 3. Motor output (Effector) → Activates effector organs–the muscles and glands–to cause a response *Note: This is the same as the Homeostatic Control System (if you remember) NEURONS  NEURONS → Neurons, or nerve cells, are highly specialized and amitotic cells. This means that if a neuron is destroyed, it cannot be replaced because neurons do not go through mitosis. → The structural units of nervous system Parts of a Neuron 1. Cell Body → Consists of a nucleus with a nucleolus and contains many of the typical cytoplasmic organelles → The major biosynthetic center of a neuron as it synthesize proteins and other chemicals  NEURONS → Neurons, or nerve cells, are highly specialized and amitotic cells. This means that if a neuron is destroyed, it cannot be replaced because neurons do not go through mitosis. → The structural units of nervous system Parts of a Neuron 2. Dendrites → All organelles present in the cell body also occur in dendrites → The main receptive or input regions → Convey incoming messages toward the cell body  NEURONS → Neurons, or nerve cells, are highly specialized and amitotic cells. This means that if a neuron is destroyed, it cannot be replaced because neurons do not go through mitosis. → The structural units of nervous system Parts of a Neuron 3. Axon → Each neuron has a single axon → The conducting region of the neuron → Send messages away from the cell body  CENTRAL NERVOUS SYSTEM  CENTRAL NERVOUS SYSTEM (CNS) → Consists of the brain and spinal cord, which occupy the dorsal body cavity → Control center of the nervous system Functions: Integrates Interprets sensory input Dictates motor output based on reflexes, current conditions, and experience  BRAIN → The average adult human brain has a mass of about 1500 g and is composed of about 100 billion neurons → It integrates all nervous system activity and “commands” all voluntary activities Three layers of meninges around the brain and spinal cord 1. Dura mater – Outer layer – Strongest matrix 2. Arachnoid – Middle layer which resembles a cobweb in appearance 3. Pia mater – Innermost layer, a thin and delicate membrane tightly bound to the surface of the brain and spinal cord  BRAIN → The average adult human brain has a mass of about 1500 g and is composed of about 100 billion neurons → It integrates all nervous system activity and “commands” all voluntary activities Brain Division 1. Cerebral hemispheres 2. Diencephalon 3. Brain stem (midbrain, pons, and medulla oblongata) 4. Cerebellum  BRAIN 1. Cerebral hemispheres → Form the superior part of the brain → It account for about 83% of total brain mass → All voluntary or conscious activities of the body Function: Site of intelligence, learning and judgment Voluntary motor control Sensation Reasoning Language and speech  BRAIN 2. Diencephalon → Consists of the thalamus, hypothalamus, and epithalamus 2.1 Thalamus → Is a Greek word meaning "inner room," which describes this deep, well-hidden brain region → Makes up 80% of the diencephalon Function: Relay station for information coming into the cerebral cortex Meditates sensation  BRAIN 2. Diencephalon → Consists of the thalamus, hypothalamus, and epithalamus 2.2 Hypothalamus → Despite its small size, it is the main visceral control center of the body and is vitally important to the overall body homeostasis Function: Control the autonomic nervous system Initiate physical responses to emotions  BRAIN 2. Diencephalon → Consists of the thalamus, hypothalamus, and epithalamus 2.3 Epithalamus → The most dorsal portion of the diencephalon Function: Helps regulate the sleep-wake cycle  BRAIN 3. Brain Stem → Consists of the midbrain, pons, and medulla oblongata 3.1 Midbrain → Located between the diencephalon and pons → The most superior portion of the brain stem Function: Coordinate head and eye movements Auditory relay from the hearing receptors  BRAIN 3. Brain Stem → Consists of the midbrain, pons, and medulla oblongata 3.2 Medulla Oblongata → The most inferior part of the brain stem → It blends imperceptibly into the spinal cord Function: Maintaining homeostasis Cardiovascular center Respiratory centers  BRAIN 4. Cerebellum → "small brain", exceeded in size only by the cerebrum, accounts for about 11% of total brain mass Function: Processes inputs received from the cerebral motor cortex Provides appropriate patterns of skeletal muscle contraction for smooth, coordinated movements and agility needed for our daily living  SPINAL CORD → Enclosed in the vertebral column → About 42 cm (17 inches) long and 1.8 cm (3/4 of an inch) thick → Like the brain, it is also surrounded by bone, meninges, and cerebrospinal fluid → Divided into 31 segments with each segment giving rise to a pair of spinal nerves Function: Serves as a conduction pathway for impulses going to and from the brain Serving as a reflex center  PERIPHERAL NERVOUS SYSTEM  PERIPHERAL NERVOUS SYSTEM (PNS) → Consists mainly of nerves that extend from the brain, spinal cord, and ganglia → The part of the nervous system outside the CNS Cranial Nerves → Carry impulses to and from the brain 12 Pairs (Oh Oh Oh To Touch And Feel A Girl’s Vagina Ah Heaven!) 1. Olfactory 7. Facial 2. Optic 8. Auditory 3. Oculomotor 9. Glossopharyngeal 4. Trochlear 10. Vagus 5. Trigeminal 11. Accessory 6. Abducens 12. Hypoglossal  PERIPHERAL NERVOUS SYSTEM (PNS) → Consists mainly of nerves that extend from the brain, spinal cord, and ganglia → The part of the nervous system outside the CNS Spinal Nerves → Carry impulses to and from the spinal cord 31 Pairs 1. Cervical nerves – 8 pairs (C1-C8) 2. Thoracic nerves – 12 pairs (T1-12) 3. Lumbar nerves – 5 pairs (L1-L5) 4. Sacral nerves – 5 pairs (S1-S5) 5. Coccygeal nerves – 1 pair (Co1)  PERIPHERAL NERVOUS SYSTEM (PNS) → Consists mainly of nerves that extend from the brain, spinal cord, and ganglia → The part of the nervous system outside the CNS Three Functional Subdivisions 1. Sensory (Afferent) → “Approaches“, carry impulses only toward the CNS 1.1 Somatic sensory fibers → Convey impulses from the skin, skeletal muscles, and joints 1.2 Visceral sensory fibers → Transmit impulses from the visceral organs (ventral body cavity organs)  PERIPHERAL NERVOUS SYSTEM (PNS) → Consists mainly of nerves that extend from the brain, spinal cord, and ganglia → The part of the nervous system outside the CNS Three Functional Subdivisions 2. Motor (Efferent) → “Exits“, carry impulses only away from the CNS 3. Interneurons → Contain both motor and sensory neurons and transmits impulses both to and from the CNS → Make up over 99% of the neurons of the body  PERIPHERAL NERVOUS SYSTEM (PNS) → Consists mainly of nerves that extend from the brain, spinal cord, and ganglia → The part of the nervous system outside the CNS Two Division of PNS 1. Somatic Nervous system → Composed of somatic motor nerve fibers that conduct impulses from the CNS to skeletal muscles → “Voluntary nervous system” because it allows us to consciously control our skeletal muscles  PERIPHERAL NERVOUS SYSTEM (PNS) → Consists mainly of nerves that extend from the brain, spinal cord, and ganglia → The part of the nervous system outside the CNS Two Division of PNS 2. Autonomic Nervous system → Consists of visceral motor nerve fibers that regulate the activity of smooth muscles, cardiac muscles, and glands → “Involuntary nervous system because we cannot control such activities as the pumping of our heart Sympathetic division – “Fight or flight” response Parasympathetic division – “Rest and digest” response CONGRATS! YOU MADE IT THIS FAR. NOW, REST.