Chapter 48

 Recognizes and coordinates the body’s response to changes in its internal and external environments. ◦ Sensory input – vision, hearing, balance, smell, taste, and touch ◦ Motor output – muscle contraction and movement ◦ Memory and integration of information

 All animals except sponges have a nervous system  What distinguishes nervous systems of different animal groups is how neurons are organized into circuits

 Specialized cells that carry electrical signals called impulses  3 Types of Neurons: ◦ Sensory – carry impulses from the sense organs to the spinal cord and brain ◦ Motor – carry impulses from brain and spinal cord to muscles and glands ◦ Interneurons – Connect sensory and motor neurons and carry impulses between them

 Automatic responses to stimuli  Controlled by 5-part reflex arc: ◦ 1. Sensory receptor reacts to stimulus (heat on finger) ◦ 2. Impulse is carried to the spinal cord by a sensory neuron ◦ 3. In the spinal cord, the impulse is transferred to a motor neuron ◦ 4. Motor neuron conducts a nerve impulse to an effector (arm muscles) ◦ 5. Effector responds to the impulses by contracting (hand gets pulled away from the heat)

 Cnidarians, sea stars ◦ Nerve nets  Flatworms, leeches ◦ Relatively simple cephalization, have a central nervous system (CNS)  Annelids, arthropods ◦ Ganglia (arranged clusters of neurons) connect to CNS, making a peripheral nervous system (PNS)

 At rest, the outside of the cell has a net positive charge, and the inside has a net negative charge. ◦ This charge difference is called the resting potential (-70mVolts).  This charge difference is due to active transport by the sodium-potassium pump.  The sodium-potassium pump moves sodium (Na + ) outside the cell, and potassium (K + ) inside the cell.

 1. An impulse begins when a neuron is stimulated by another neuron or by the environment.  2. Sodium pores open on the membrane and sodium ions diffuse into the neuron.  3. The internal charge goes from -70 mVolts to +30 mVolts.  4. This is called the action potential.

 5. The influx of sodium stimulates the opening of potassium pores and (K+) flows out.  6. This restores the resting potential to normal.  7. But now all of the sodium is inside and the potassium is outside.  How does the cell go back to its original condition? ◦ The sodium/potassium pump kicks in.  8. The depolarization on one segment starts a domino effect down the neuron.

 The gap between the axon of one neuron and the dendrites or cell body of the next neuron.  When the impulse reaches the end of the axon, chemicals called neurotransmitters are released and carry the impulse to the next neuron.

 Cerebrum ◦ Largest region; folds and grooves increase surface area ◦ Controls voluntary activities and all higher brain functions (intelligence, learning and judgment) ◦ Right and left hemispheres are connected by corpus callosum

 Cerebellum ◦ Center for balance and coordination of voluntary muscle movements.  Brain Stem ◦ Relays information between brain and spinal cord ◦ Comprised of the pons and medulla oblongata ◦ Work together to control involuntary processes like breathing, heart rate, blood pressure, digestion, and swallowing

 Thalamus ◦ Relay station for all sensory input to the cerebrum.  Hypothalamus ◦ Homeostatic center that controls endocrine system (hormones), body temperature, thirst, hunger, fatigue, etc.

 Two main functions: ◦ Reflex center ◦ Carries info to and from brain to body

 Receives information from the environment and relays to and from CNS and sensory, motor and gland cells  Two divisions: Sensory and Motor  Motor is divided into: ◦ Somatic NS (voluntary) responds to external stimuli.  1.Regulates activities that are under conscious control (e.g. picking your nose)  2.Some reflex control ◦ Autonomic (involuntary) NS respond to internal stimuli; two divisions:  Sympathetic ↑energy consumption (increase HR)  Parasympathetic ↓energy consumption (decrease HR)  Both help maintain homeostasis by having opposing effects

 Bell’s Palsy – unexplained episode of facial weakness or paralysis  Dementia - damaged brain cells caused by injury or disease (Alzheimer’s); memory loss, confusion and personality change  Migraine Headaches – caused by a drop in serotonin levels? (triggered by stress, hormones, certain foods)  Multiple sclerosis (MS) – myelin sheaths deteriorate resulting in progressive loss of coordination  Parkinson’s – uncontrollable shaking caused by damage to dopamine transmitters; no cure  Tay-Sachs – fatal genetic lipid storage disorder where fat builds up on brain tissues and neurons during the first few months of life causing mental and physical deterioration

 Stimulants  Accelerate HR, BP, and breathing rate  Increases the release of neurotransmitters; leads to release of energy and feeling of well- being  When effect wears off, brain’s supply is depleted leaving the user depressed and fatigued ◦ Caffeine – prevents binding of adenosine ◦ Cocaine – sudden release of dopamine ◦ Methamphetamines – same effect as cocaine

 Depressants  Slow down HR, lower BP and breathing rate, relax muscles and relieves anxiety ◦ Alcohol – physical and mental impairment, depression, liver damage ◦ Marijuana – more lung damage than cigarettes; memory loss, reduced levels of testosterone in males ◦ Sleeping Pills