The Nervous System: Chapter 8 Organs of the Nervous System Brain Spinal cord Numerous nerves Specialized sense organs such as eyes and ears Microscopic sense organs such as those found in the skin (touch receptors like Pacinian corpuscles) 1

Divisions of Nervous System Cool link to understanding the divisions of the Nervous System http://www.youtube.com/watch?v=dOYOdJG0E0s Central Nervous System Peripheral Nervous System CNS - Brain, spinal cord – processes information PNS - Nerves that extend to the periphery of body – send and receive information Autonomic nervous system - involuntary functions (breathing, heart beat, digestion etcs, etc) – smooth and cardiac muscle, glands Somatic - voluntary functions - skeletal muscle see next slide for details on PNS 2

Peripheral Nervous System Somatic Autonomic

Neurons What do they do? 3 parts: carry the impulses that make things happen.(action potentials) cell body, branching projections called dendrites and axons with branches called axon terminals. 4

3 Types of Supporting Cells (Neuroglia) 1. Astrocytes: Specialized connective tissue cells that support & protect neurons and are stem cells for nervous tissue 2. Microglia - smaller, microbe eating scavengers 3. Oligodendrocytes (CNS)/Schwann cells( PNS) - cells that insulate axons by producing a lipid called myelin 5

3 Kinds of Neurons Sensory neurons transmit impulses to the spinal cord and brain from all parts of the body. Motor neurons transmit impulses in the opposite direction - away from the brain and spinal cord toward muscles and glands to make things happen. Interneurons conduct impulses from sensory neurons to motor neurons. Conduct impulses between sensory and motor neurons in CNS 6

Axon is covered in ________________. Myelin is formed by ____________ __________. Myelin is white – myelin filled cells called ___________________ Nodes of Ranvier - Myelin Schwann cells/Oligodendrocytes gaps between adjacent Schwann cells that aid in quick transmission of signals 7

Nerve Bundle Organization Nerve cells are bundled together like muscle cells into bundles called fascicles. White matter - has myelin Each axon in a nerve is surrounded by fibrous connective tissue called endoneurium. Groups of these axons are called fascicles which are surrounded by perineurium Epineurium covers whole nerve (fibrous sheath) 8

Reflex Arcs - no brain involvement for super quick reaction Reflex – quick, automatic response Reflex Arc – the nerve pathway involved in a reflex action. 9

Saltatory conduction – “jumping” conduction – action potential moves very fast by jumpingover Schwann cells from node to node to node 10

Nerve Impulses/ Action Potentials Self propagating (self- spreading) wave of electrical disturbance that travels along the surface of a neuron’s plasma membrane. Resting Potential: Neuron at rest has a negative charge inside the membrane, a positive charge outside (______pump) Stimulus: occurs and ions move across membrane Depolarization: Action Potential reverses charges across the membrane ( ____________ channel opens) Charge reversal “travels” down the membrane of axon Repolarization: Electrical charges return to resting values (____________ channel opens) 6. Resting membrane potential restored. (_________ pump) Depol: sodium channel open to allow positive ions in - inner membrane becomes more positive. Repol: potassium channel open to let positive ions out and restore RMP) 11

Action Potential Action potential spreading down the axon of a neuron – its contagious! this is called “self-propogating” 12

Nerve Impulse Label sodium-potassium pump and sodium and potassium channels as review. 13

The Synapse Impulses must be transferred between neurons to convey information but action potential can’t “jump the gap” Synapse is the place where two neurons connect – but it’s a GAP – they don’t touch! Gap called synaptic cleft Impulse moves from the axon of the pre-synaptic cell to the dendrite of the post-synaptic cell Electric charge doesn’t cross gap; converted into chemical message called a neurotransmitter. 14

Neurotransmitters are chemicals that Carry Signal Across the Synapse

Action Potential Video http://highered.mheducation.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html 16

There are many Neurotransmitters Can turn neurons on or off (often both…) Acetylcholine - muscle contraction Norepinephrine – stress, fight-or-flight (aka adrenaline when made by adrenal gland) Serotonin – mood (Prozac, antidepressants) Dopamine - movement, and reward-behavior (cocaine, speed, ADHD meds, Facebook and Twitter all cause a “dopamine hit” ) Endorphins – like opiates – feeling of well- being (exercise releases them)

Nervous System Disorders Multiple sclerosis Alzheimer’s Disease Parkinson’s Disease ALS ADHD Some Depression/Psychiatric Disorders MS autoimmune disease where immune system attacks and destroys myelin. Interferes with neuron communication; nerves can be destroyed eventually and don’t regenerate. Can lead to loss of movement, speech. Symptoms are numbness, tingling, blurred or painful vision, slurred speech, tremor (write: autoimmune disease that destroys myelin; leads to loss of movement and speech) Alzheimer’s Disease is a degenerative brain disease – slow loss of memory and thinking skills. Protein deposits called amyloid plaques cause clumps and tangles in brain that cause problems. When damage spreads to hippocampus, memory formation is impeded. CVA/stroke – clot or bleed blocks blood supply to part of the brain, causing brain damage. Recovery prospects imrpoving… Parkinson’s Disease is caused by lack of dopamine. Neurons die that make dopamine, leading to tremor and slowed movements. Not sure of cause – small effects of genes and certain environmental toxins. ALS is a motor neuron disease where person loses ability to control the voluntary muscles. Muscles can’t function, and they gradually atrophy until person cannot move at all. When diaphragm muscle fails, person dies of respiratory failure. Most ALS patients die of respiratory failure within 3-5 yrs of onset of symptoms. Some cases connected to genetic mutation, most are mysterious. ADHD - some research shows possible genetic link; also linked to low dopamine system – meaning body needs prescription dopamine – aka stimulants like ritalin CVA/stroke – blood supply to brain reduced or interrupted’ leads to death of brain tissue. Medical emergency. Cerebral palsy - motor condition causing problems with movement. Usually occurs in infancy or early childhood. Usually caused by problems in pregnancy or birth injury. 18