PNS and CNS PDF

The Peripheral Nervous System: Structure and Functions The Nervous System is divided into: Central Nervous System(CNS) Peripheral Nervous System(PNS)  Introduction to the Peripheral Nervous System (PNS) The network of nerves outside the brain and spinal cord Acts as a co...

The Peripheral Nervous System: Structure and Functions The Nervous System is divided into: Central Nervous System(CNS) Peripheral Nervous System(PNS)  Introduction to the Peripheral Nervous System (PNS) The network of nerves outside the brain and spinal cord Acts as a communication bridge between the central nervous system and body Consists of two major divisions: somatic and autonomic nervous systems Contains approximately 100 billion neurons  Overview of PNS Divisions Main Divisions: Somatic Nervous System Autonomic Nervous System Each division serves distinct functions Work together to maintain homeostasis Different types of neurons and nerve fibers  Somatic Nervous System Controls voluntary movements Connects CNS to: Skeletal muscles Skin receptors Sense organs Responsible for conscious activities Uses motor and sensory neurons  Autonomic Nervous System (ANS) Basics Controls involuntary functions Regulates internal organs Two subdivisions: Sympathetic Parasympathetic Maintains body's automatic functions  Sympathetic Division "Fight or Flight" response Activates during stress Effects include: Increased heart rate Dilated pupils Enhanced metabolism Decreased digestion Uses norepinephrine as primary neurotransmitter  Parasympathetic Division "Rest and Digest" response Active during calm states Effects include: Decreased heart rate Constricted pupils Enhanced digestion Reduced blood pressure Uses acetylcholine as primary neurotransmitter  Types of Neurons in PNS Sensory (Afferent) Neurons Motor (Efferent) Neurons Mixed Nerves Interneurons Each type specialized for specific functions  Cranial Nerves 12 pairs total Connect directly to brain Control: Facial expressions Eye movement Hearing Taste Smell Spinal Nerves 31 pairs total Connect to spinal cord Organized by region: Cervical (8 pairs) Thoracic (12 pairs) Lumbar (5 pairs) Sacral (5 pairs) Coccygeal (1 pair)  Neurotransmitters in PNS Chemical messengers Key types: Acetylcholine Norepinephrine Epinephrine Substance P Different effects on target tissues The Central Nervous System: Structure and Function  Introduction to the Central Nervous System The central nervous system (CNS) is the control center of the body Consists of two main components: brain and spinal cord Processes and coordinates all bodily functions Protected by bones and specialized membranes called the meninges The CNS is composed of: myelinated neurons (called white matter) Unmyelinated neurons (called grey matter) In the spinal cord the white matter is on the outer surface, and the grey matter is at the centre In the brain the grey matter is on the outer surface, and the white matter is at the centre  Protection of the CNS Skull (cranium) protects the brain Vertebral column protects the spinal cord Three layers of meninges: Dura mater (outer layer) Arachnoid mater (middle layer) Pia mater (inner layer) Cerebrospinal fluid provides cushioning and transports nutrients to the brain and spinal cord from the blood  Major Brain Regions Four main regions: Forebrain – Cerebrum, thalamus, and hypothalamus Cerebellum Brain stem – pons, medulla oblongata Each region serves specific functions Regions work together in complex networks  The Cerebrum Largest part of the brain Divided into left and right hemispheres connected by a bridge of neurons called the Corpus callosum Four lobes: Frontal (movement, reasoning) Parietal (sensation, spatial awareness) Temporal (hearing, memory) Occipital (vision)  Also part of the Forebrain : Thalamus (sensory relay station) Hypothalamus (homeostasis control) Pineal gland (melatonin production) Pituitary gland (hormone control) Cerebral Functions Controls higher-order thinking Manages voluntary movement (motor cortex) Processes sensory information (sensory cortex) Houses language centers Regulates emotional responses Stores memories  The Cerebellum Located at the back of the brain Primary functions: Balance coordination Posture maintenance Fine motor control Movement timing Contains more neurons than rest of brain combined  The Brain Stem Three main parts: Midbrain Pons Medulla oblongata Controls vital functions: Breathing Heart rate Blood pressure Sleep cycles  The Spinal Cord Extends from brain stem to lower back 31 pairs of spinal nerves Functions: Information highway to/from brain Reflex center Movement control  Spinal Cord Structure Grey matter (butterfly shape) Contains neuron cell bodies White matter Contains axon tracts Central canal Contains cerebrospinal fluid  CNS Disorders Common conditions affecting the CNS: Multiple sclerosis Alzheimer's disease Parkinson's disease Epilepsy Spinal cord injuries  Protecting CNS Health Regular exercise Proper nutrition Adequate sleep Mental stimulation Avoiding harmful substances Wearing protective gear during activities  Review Questions Name the major regions of the brain Describe the three layers of meninges List three functions of the brain stem Explain the difference between grey and white matter Identify two ways to protect CNS health