The Nervous System Chapter 35: Biology II
Anatomy and Physiology Anatomy: the study of structure Physiology: The study of how living organisms function, including such processes as nutrition, movement, and reproduction
Organization of the Body 11 organ systems work together to maintain homeostasis Nervous Skeletal Muscular Integumentary Circulatory Respiratory Digestive Excretory Endocrine Reproductive Immune
Organization of the Body What is an organ? FLASHBACK: Organ: group of tissues that work together to perform closely related functions Tissue: group of similar cells that perform a particular function
Muscle Tissue Controls: internal movement of materials of blood and food external movements of the entire body or parts of the body The heart is mainly muscle!
Epithelial Tissue Lines body surfaces (inside and out) Protects tissues Constantly being replaced
Connective Tissue Support Protects Insulates Fat, cartilage, bones, tendons, ligaments Keeps the walls of the heart flexible, but strong
Nervous Tissue Receives messages from the body s external and internal environments Analyzes the data Directs a response
The Nervous System Controls and coordinates functions throughout the body Responds to internal and external stimuli
The Neuron: The Nerve Cell
The Neuron Cell body/soma: largest part of a typical neuron Contains the nucleus and much of the cytoplasm
The Neuron Dendrites: extension of the cell body Carry impulses from the environment or from other neurons toward the cell body
Axon: long fiber that carries impulses away from the cell body of a neuron The Neuron
The Neuron Myelin sheath: insulating membrane surrounding the axon in some neurons Nodes of Ranvier: unmyelinated part of axon The nerve impulse moves faster because it can jump from node to node
The Neuron Axon Terminal: the end of the axon that forms a synapse with another neuron The point at which a neuron passes information to the neurons with which it is connected.
The Nerve Impulse Like electricity moving through a wire Depends on the movement of positively charged ions across a cell membrane
The Nerve Impulse A nerve impulse begins when a neuron is stimulated by another neuron or by its environment Resting Potential: difference in electrical charge across the cell membrane of a resting neuron (-70mV) Action Potential: reversal of charges across the cell membrane of a neuron (+30mV) Threshold: minimum level of a stimulus required to activate a neuron
The Nerve Impulse Polarized, Resting -70mv Inside - (high K +, low Na + ) Outside + (high Na +, low K + ) At rest, K + can move but Na + cannot K + moves outside by diffusion Depolarization Stimulus opens some Na + channels Na+ rushes in to the threshold +30mv ( All or None ) A wave of depolarization moves down the neuron Inside + Outside Repolarization K + rushes out to restore balance of the neuron Polarized Na + /K + pump actively bring K+ back in and Na+ out of the axon Neuron returns to resting condition
The Synapse Synapse: location at which a neuron can transfer an impulse to another cell Neurotransmitter: chemical used by a neuron to transmit an impulse across a synapse to another cell
Some Key Neurotransmitters at Work Acetylcholine: Excitatory makes cells more excitable. Causes muscle contractions and causes glands to secrete hormones GABA: Inhibitory makes cells less excitable. Helps control muscle activity and is important to the visual system. Serotonin: Inhibitory constricts blood vessels that bring on sleep. Also involved in behavior, mood, appetite, pain, and temperature regulation Dopamine: Inhibitory involved in mood and the control of complex movements
The Synapse
Death of the Neuron Parkinson s Disease: neurons that produces the neurotransmitter dopamine die in the basal ganglia, an area of the brain that controls body movement. Result: The brain can no longer control the body and people shake and jerk in spasms.
Death of the Neuron Huntington s Disease: genetic mutation causes over-production of a neurotransmitter called glutamate, which kills neurons in the basal ganglia. Result: People twist and writhe uncontrollably.
Death of the Neuron Alzheimer s Disease: unusual proteins build up in and around neurons in the neocortex and hippocampus, parts of the brain that control memory. Shortage of acetylcholine Result: People lose their capacity to remember and their ability to do everyday tasks.
Death of the Neuron Physical damage to the brain and other parts of the CNS can also kill or disable neurons Blows to the brain or the damage caused by a stroke: can kill neurons outright or slowly starve them of oxygen and nutrients Spinal cord injury: can disrupt communication between the brain and muscles when neurons lose their connection to axons located below the site of injury. These neurons live, but lose their ability to communicate.
Spinal Cord Injury
Drugs That Affect The Synapse Stimulants Marijuana Depressants Alcohol Cocaine Alcohol and Disease Opiates
Stimulants Increase the actions regulated by the nervous system Increase heart rate Raise blood pressure Increase breathing rate Increase the number of neurotransmitters at some synapses in the brain Examples: amphetamines, cocaine, nictotine, caffeine
Depressants Decrease the rate of functions regulated by the brain Decrease heart rate Decrease breathing rate Lower blood pressure Relax muscles Relieve tension Example: alcohol
Cocaine Causes the sudden release in the brain of a neurotransmitter: DOPAMINE Addiction: uncontrollable craving for more of a drug Powerful stimulant
Cocaine
Opiates Opium poppy produces a powerful class of painkillers: opiates Mimic natural chemicals in the brain known as endorphins, which normally help to overcome sensations of pain
Marijuana The most widely abused illegal drug Species of hemp plant THC: active ingredient (tetrahydrocannabinol)
Alcohol One of the most dangerous and abused depressant drugs Slows down the rate at which the CNS functions Can lead to the DISEASE: Alcoholism
Effects of Blood Alcohol Concentration
Psychoactive Drugs of Abuse
Drug Abuse Use of any drug in a way that most doctors would not approve
Divisions of the Nervous System Central Nervous System (CNS) Brain Spinal Cord Peripheral Nervous System (PNS) Somatic Nervous System Autonomic Nervous System
Central Nervous System (CNS) Relays messages, processes information, and analyzes information Meninges: 3 layers of CT in which the brain and spinal cord are wrapped Cerebrospinal Fluid: fluid in the space between the meninges that acts as a shock absorber that protects the CNS
The Brain Cerebrum: area of the brain responsible for all voluntary activities of the body Holds memories Enables imagining and thinking Lets you recognize friends, read books, play games Left: words, language Right: abstract reasoning skills
Cerebellum: region of the brain that coordinates body movements The Brain Play piano, hit tennis ball, etc Balance
The Brain Brain Stem: structure that connects the brain and spinal cord Medulla Oblongata: controls autonomic functions such as breathing, digestion, heart and blood vessel function, swallowing and sneezing Pons: communication and coordination center between the two hemispheres of the brain
Thalamus: receives messages from the sense organs and relays the information to the proper region of the cerebrum for further processing The Brain
Hypothalamus: control center for recognition and analysis of hunger, thirst, fatigue, anger and body temperature The Brain
The Brain
The Brain
Spinal Cord Main communication link between the brain and the rest of the body Reflex: quick automatic responses to a stimulus
Peripheral Nervous System (PNS) All the nerves and associated cells that are not a part of the brain and the spinal cord Cranial nerves, spinal nerves, ganglia Sensory (afferent): sense organs to CNS Motor (efferent): CNS to the muscles or glands
Peripheral Nervous System (PNS) Somatic Nervous System: regulates activities that are under conscious control Autonomic Nervous System: regulates activities that are automatic, or involuntary Parasympathetic Sympathetic
Example: Autonomic Nervous System
Physiological Effects of the Autonomic Nervous System
The Senses Sensory Receptors: located throughout the body but are concentrated in the sense organs Pain Receptors Thermoreceptors Mechanoreceptors Chemoreceptors Photoreceptors
Types of Sensory Receptors
The Senses Vision Hearing and Balance Smell Taste Touch and Related Senses
Vision Pupil: small opening in the middle of the iris through which light enters the eye Lens: transparent object behind the iris that changes shape to help adjust the eye s focus to see near or distant objects
Vision Retina: innermost layer of the eye Rod: photoreceptor in eye that is extremely sensitive to light Cone: in the retina of the eye, a photoreceptor that responds to light of different colors, producing color vision
Hearing and Balance Cochlea: fluid-filled part of the inner ear; sends nerve impulses to the brain through the cochlear nerve Semicircular Canal: one of three structures within the inner ear that help an organisms maintain balance
Smell and Taste Both: an ability to detect chemicals Taste Bud: sense organ that detects the flavor of a substance
Touch and Related Senses Your largest sense organ: SKIN! Skin has sensory receptors that respond to: Temperature Touch Pain The greatest density of touch receptors is found on your fingers, toes and face