Bell Work Materials Needed: writing utensil and A&P book Quietly pick up a Lesson 6.5 worksheet from the back table and work on it independently.
The Nervous System ANATOMY & PHYSIOLOGY
Overview Controls voluntary movement Directs involuntary functions Smooth muscle of internal organs Muscles of the heart Senses All dependent on sensory electrical input Structural and Functional subdivisions
Organization Central Nervous System Includes the brain & spinal cord Directs activity of the ENTIRE nervous system Peripheral Nervous System All other parts of nervous system Ex. Spinal nerves and cranial nerves Sensory receptors Specialized nerve endings which respond to stimuli such as pressure, pain, and temperature
Nerves Afferent (sensory) Nerves that transmit impulses from the sensory receptors in the skin, muscles, and joints to the CNS Efferent (motor) Nerves that carry impulses from the CNS out to the muscles and glands Two Functional subdivisions Somatic (voluntary): stimulates skeletal muscles causing them to develop tension Autonomic (involuntary): controls cardiac muscle of heart and smooth muscle of organs
Nervous Tissue Include specialized supporting cells called neuroglia and neurons Neuroglia (glial cells) perform support functions CNS Astrocytes Microglia Ependymal Oligodendrocytes PNS Schwann Satellite Neurons transmit information in the form of nerve impulses throughout the body
Neuroglia Central Nervous System PNS Astrocytes: link nutrient supplying capillaries to neurons, and control chemical environment Microglia: absorb and dispose of dead cells & bacteria Ependymal: form protective covering around the central cavities in the brain and spinal cord Oligodendrocytes: wrap around nerve fibers & produce fatty insulating material called myelin Schwann: form fatty myelin sheaths around nerve fibers Satellite: serve as cushioning support
Neurons
Neurons 3 Types Sensory (afferent) Carry impulses from skin and organs to spinal cord & brain Motor (efferent) Transmit impulses from the brain and spinal cord to the muscles & glands Interneurons (association) Form bridges to transport impulses between other neurons
Neuron Structures Bipolar Neurons 1 axon & 1 dendrite sensory processing cells found in eyes & nose Unipolar Neurons Single axon with dendrites on the peripheral end and axon terminals on the central end. Peripheral carries impulses to the cell body, and central processes carries impulses to the CNS Multipolar Neurons Have 1 axon and multiple dendrites all motor neurons and interneurons
Neuron Structures Multipolar Bipolar Unipolar
Behavioral Properties Irritability Ability to respond to a stimulus (similar to muscle) Conductivity Ability to convert a stimulus into a nerve impulse
Action Potentials K+ inside the cell, NA+ outside Inside = negatively charged = polarized When stimulus exceeds critical voltage, gated NA+ channels open and NA+ floods the cell Electrical charge inside cell becomes more + which leads to depolarization This electrical charge is known as a nerve impulse, or action potential https://www.youtube.com/watch?v=xnksofqn8_s
Action Potentials Repolarization following the action potential, the membrane becomes permeable to K+ which flood the cell and restores the membrane to its original polarized state Until the cell membrane is polarized it can not respond to another stimulus Refractory Period Time between the completion of the action potential and repolarization During this time the neuron is temporarily fatigued
Action Potentials
Impulse transmission Three factors influence speed of nerve impulses: Presence or absence of a myelin sheath Diameter of the axon: > the diameter the faster the impulse Body temperature: warmer temps increase impulse Saltatory Conduction Since the myelin sheaths are electrical insulators, action potentials jump over the myelinated regions of the axon faster impulse transmission than is possible in nonmyelinated axons
Synapses Communication between neurons occurs at the synapses (see page 204) AP reaches terminal Terminal depolarizes Ca+ gates open and Ca+ flows into the terminal Axon terminal is filled with neurotransmitters Ca+ causes vesicle to join the cell membrane adjacent to the synaptic cleft Pores form allowing neurotransmitters to diffuse across the synapse to receptors on the membrane of the joining neuron
Reflexes Simple, rapid, involuntary responses to stimuli Somatic Those that involve stimulation of skeletal muscles Withdrawing your hand from something hot Autonomic Those that send involuntary stimuli to the cardiac muscle of the heart and smooth muscle of internal organs Digestion, sweating, blood pressure
Functional Anatomy The brain Weighs between 2.25 3.25 lbs Contains approx. 100 billion neurons and even more glial cells Size of brain does have a 6.7% attribution to intelligence 4 major anatomic regions: Cerebrum Diencephalon Brain stem Cerebellum
Cerebrum Largest portion of the brain Left and right cerebral hemispheres Cerebral cortex: outer surface composed of nonmyelinated gray matter Internal tissue is myelinated white matter with small areas of gray matter known as basal nuclei
Cerebrum Sucli divide brain into 4 regions (lobes) Frontal, parietal, occipital, temporal Fissures are deep grooves in the brain Divide brain into left and right hemispheres Frontal: initiates and controls muscle tension Parietal: interprets sensory impulses received from skin Occipital: responsible for vision Temporal: speech, hearing, memory, emotion
Lobes of Brain
Diencephalon Interbrain located deep inside the brain surrounded by the cerebrum Includes 3 important structures: Thalamus: relay station for both sensory & motor information between body & cerebral cortex Also regulates sleep, wakefulness, and high alert consciousness. Hypothalamus: regulates HR, BP, thirst, hunger, energy, and body temp Epithalamus: includes pineal gland and regulates sleep cycle hormones
Brain Stem Includes 3 structures: Midbrain: relays info concerning vision, hearing, motor activity, sleep and wake cycles, and temp Pons: regulates breathing Medulla Oblongata: regulates HR, BP, breathing Also controls reflexes for coughing, sneezing & vomitting
Brain Stem
Cerebellum Found in the occipital lobe Coordinates body movements & balance Receives input from eyes, inner ears, and sensory receptors throughout the body Constantly monitoring body segment positions and motions
Meninges Surround the brain and spinal cord
Meninges of Spinal Cord
Nerve Structure
Cranial Nerves 12 pairs Referred to both by a name and number Some nerves contain only afferent fibers, some only efferent fibers, some both
Spinal Nerves 32 pairs of spinal nerves Named from the vertebral level from which it originates All spinal nerves are mixed, carrying both afferent and efferent info About ½ inches long, immediately dividing into a dorsal ramus and a ventral ramus https://www.youtube.com/watch?v=safataavmo8
Spinal Nerves
Ventral rami in the cervical and lumbar regions branch out to form complex interconnections Nerve Plexuses
Autonomic Nervous System Sympathetic Nerves Activate the fight or flight response by stimulating the adrenal gland to release epinephrine (adrenaline) Triggered by any type of situation that is perceived to be stressful Parasympathetic Nerves Controls the day in day out functions of the circulatory, respiratory, and digestive systems Resting & digesting system Calms the body after a flight or fight situation
Injuries & Disorders Traumatic Brain Injury (TBI) Classified at mild, moderate, or severe Can occur during violent impacts to the head Mild TBI symptoms: Headache, confusion, dizziness, disturbed vision Moderate to Severe: All of the above + prolonged headache, repeated nausea, convulsions, seizures, slurred speech 50% of TBI cases require surgical repair
Cerebral Palsy Group of nervous system disorders caused by damage to the brain before or during birth, or in early infancy Abnormal brain shape or structure, damaged nerve cells or tissues Symptoms: Varying degrees of motor function impairment Hearing, seeing, and cognitive impairment One or both sides of the body may be infected
Spinal Cord Injury C1-c3: usually fatal C1-C4: quadriplegia loss of function from neck down C5-C7: complete paralysis of the lower extremities, partial loss of trunk and upper extremities T1-L5: paraplegia loss of function in the trunk and legs Critical that head, neck and trunk be immobilized before moving someone with a cord injury
Meningitis Inflammation of the meninges surrounding the brain and spinal cord Swelling of the tissues is usually caused by infection, and produce headache, fever, and stiff neck Most infections that cause meningitis are viral, and can resolve on their own Bacterial meningitis is life-threatening, but can be treated with antibiotics
Multiple Sclerosis Autoimmune disease causing inflammation that destroys myelin sheaths of nerve cell axons Most common between 20-40 yr. old females Symptoms Impairments in motor function, sensory impairments, cognitive issues No known cure, however life expectancy can be normal with treatment
Epilepsy Group of brain disorders characterized by repeated seizures over time. Triggered by abnormal electrical activity in the brain Symptoms Changes in attention span or behavior, or uncontrolled convulsions Before a seizure, many experience a signal or aura Treatment Can be controlled by medication in most cases Surgery if caused by an observable problem
Parkinson s Disease Characterized by tremors, difficulty initiating movements, and deficits in coordination Progressive destruction of brain cells responsible for production of dopamine Without dopamine, cells can t initiate nerve impulses No cure exists, goal of treatment is to control symptoms
Dementia & Alzheimer s Dementia: loss of function in 2 or more areas of cognition Usually occurs after 60 Can be cause by disruption of blood supply to brain or by AD Alzheimer s (senile dementia): progressive loss of brain function with major consequences for memory, thinking, and behavior Early onset: before 60, believed to involve genetic predisposition Late onset: after 60
Dementia & Alzheimer s
Stations Olfactory essence A, B, & C Optic Nerve Eye chart Trigeminal cotton ball & ice water Glossopharyngeal cotton ball & tongue depressor Accessory Nerve Movement of tongue