Maintaining Homeostasis using the Nervous System

Nervous System Regulates How Respiratory System Circulatory System Urinary System Digestive System Musculoskeletal System Reproductive system Breathing rate Heart rate and dilation of blood vessels Water balance Causes muscular contractions and secretion of enzymes movement Secretes hormones that control development of gametes

Nervous System Interactions

Functions Receive sensory input Integrate information Skin, other organs Internal or external Integrate information Sums up info Generate motor output Muscle contraction Cause glands to secrete hormones

Nervous System Central Nervous System Peripheral Nervous System Brain (skull) Spinal cord (vertebrae) All nerves outside CNS Sensory and motor Both Systems must work together!

Nerve Cells = Neurons Unique shape Conducts electrical impulses

Synapse – small gap between nerve cells, across which impulses pass by diffusion of a neurotransmitter.

Resting Neuron

Resting Neuron (ready to respond) Inside of Neuron Outside of Neuron Negative charge More Potassium (K+) ions Positive charge More Sodium (Na+) ions Polarized Membrane Imbalance is maintained by Active Transport - Sodium Potassium Pump

Polarized Na+ and K+ gates are closed

Action Potential Rapid change in polarity Caused by Stimulus Na+ gates open

Action Potential Must reach minimum amount = threshold Impulse is “All or none” Membrane becomes depolarized (positive on inside) Impulse travels in only one direction

After impulse - Membrane must be repolarized

Repolarization Sodium gates close Potassium gates open Potassium leaves Inside returns to negative charge

Activating next Neuron Reaches end of axon Triggers release of neurotransmitters These chemicals diffuse across synapse Bind to receptors on next neuron start impulse

Saltatory Conduction Impulse jumps from one node (N.O.R.) to next; speeds up impulse More myelin = faster impulse

Integration of Signals Different parts of the brain regulate responses of glands and muscles

Each part regulates specific functions

Functions Cerebrum: thinking Cerebellum: coordinate movement Medulla: breathing, heart rate, blood pressure Hypothalamus: regulates hunger, temperature, water balance Pineal Gland: daily rhythms Pituitary: endocrine gland that controls other glands

Destroying Nervous Systems Homeostasis Spinal cord injury – can’t be repaired Epilepsy – neurons don’t fire correctly Multiple sclerosis – destroys myelin sheath

Effects of Drugs Block receptor Activate neurotransmitters caffeine Activate neurotransmitters Nicotine - dopamine Block receptors Novacain Block normal breakdown of neurotransmitter Cocaine