Action PotentialNeurotransmittersEndocrine System

ACTION POTENTIAL

• A brief reversal of membrane charge that moves down the axon(a long extension of a nerve cell), causing an electrical impulse to be transmitted.

• Neuroscientist uses spike/impulse for the action potential.

TERMS:

1. Membrane Potential-is the electrical charge inside and outside of a neuron.

2. Ion-is a charged atom or molecule.3. Concentration Gradient- the difference of a

particular substance’s concentration between two areas.

Two Chief Ions that plays a significant role in the transmission of neural impulses:

• Sodium Ion- extracellular ion(Na+)• Potassium Ion- intracellular ion(K+)

Stages of Action Potential:

• Resting Potential• Threshold• Depolarization• Repolarization• Returning To Resting Potential

Resting Potential

• The outside of the neuron is positive when compared to the inside.

• The word potential refers to the fact that there is a potential for change here.

When a neuron is resting (not transmitting an electrical message) it is ready for stimulation and response.

Threshold

• The threshold is the minimum stimulus needed to cause an impulse to be carried. It must be of sufficient strength. Not all stimuli cause an impulse. A stimulus below the threshold has no effect on the neuron.

“All Or Nothing” Law

• The “All or Nothing” Law states that if the threshold is reached an impulse is carried, but if the threshold is not reached then there will be no impulse.

Depolarization

• Inside the cell becomes positive.

When potassium channel is closed, sodium rushes in and causes the cell interior to become more positive.

Repolarization

• Returning of the cell to the resting potential

When sodium channel is closed and the potassium channel is opened, potassium flows out of the cell and restores positive charge outside of the cell.

Return to Resting Potential

Soidum-Potassium Pump- membrane protein that is responsible for restoring the original concentrations of sodium and potassium.

TRIVIA:Animals use 1/3 of their energy because of the

sodium-potassium pump.

Neurotransmitter

• They are contained in synaptic vesicles which are found in synaptic knobs or terminals.

• Either excitatory or inhibitory.• brain chemicals that communicate

information throughout our brain and body. They relay signals between nerve cells, called “neurons.”

Neurotransmitter

• The brain uses neurotransmitters to tell your heart to beat, your lungs to breathe, and your stomach to digest. They can also affect mood, sleep, concentration, weight, and can cause adverse symptoms when they are out of balance.

Exocytosis- the process of releasing Neurotransmitter substances.

Some Neurotransmitter Substances

Neurotransmitter Functions

1.Dopamine “Pleasure” Neurotansmitter;too little in Parkinsons Disease.

2. Norepinephrine Affects Arousal level such as depression and hyperactivity.

3. Serotonin Lack of Serotonin makes going to sleep difficult;low level is implicated in aggression and depression.

4.GABA(gamma aminobutyric acid)

Lowers arousal level(inhibitory);an amino acid.

5.Endorphin Pain-relieving effect;a neuropeptide.

INHIBITORY NEUROTRANSMITTER

• Those that calm the brain and help create balance

• Inhibitory neurotransmitters balance mood and are easily depleted when the excitatory neurotransmitters are overactive.

• Prevents the conduction of Neural Impulses.• Seronin-GABA-Dopamine

Excitatory Neurotransmitters

• they are what stimulate the brain.• Increase the possibility of Neural Impulse

Firing.• Dopamine- Norepinephrine- Epinephrine

ENDOCRINE SYSTEM

• system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body.

• derived from the Greek words “endo” meaning inside, within, and “crinis” for secrete. The endocrine system is an information signal system.

PINEAL GLANDS• This gland is located near the center of the

brain in humans, and is stimulated by nerves from the eyes.

• The pineal gland secreted melatonin.Melatonin• It helps regulate other hormones and

maintains the body's circadian rhythm. (is an internal 24-hour “clock” that plays a critical role in when we fall asleep and when we wake up.)

PINEAL GLANDSWhen it is dark, your body produces more

melatonin; when it is light, the production of melatonin drops. Being exposed to bright lights in the evening or too little light during the day can disrupt the body' s normal melatonin cycles.

• SAD or seasonal affective disorder (syndrome) is a disorder in which too much melatonin is produced, especially during the long nights of winter, causing profound depression, oversleeping, weight gain, tiredness, and sadness.

HYPOTHALAMUS

• is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine via the pituitary gland.

Functions:

• Autonomic Function Control• Endocrine Function Control• Homeostasis(a state of psychological

equilibrium obtained when tension or a drive has been reduced or eliminated. )

• Motor Function Control• Food and Water Intake Regulation• Sleep-Wake Cycle Regulation

PITUITARY GLAND

• Located at the base of the brain.• Referred to as the master gland.• Controls the activities of the other endocrine

glands and secretes a growth hormone that has the crucial role of controlling body growth.

THYROID

• Located at the base of the throat near the Adam’s Apple in Males.

• Secretes hormones that control the basal metabolism.

HYPERTHYROIDISM- increased in metabolism resulting in rapid physiological processes that make the individual easily tired and irritable.

HYPOTHYROIDISM- arrest physical and mental growth in children. For adults, slows down or retards motor activities and speech.

Parathyroid gland• located behind the thyroid gland in the neck. • secretes a hormone called parathormone (or

parathyrin) that is critical to calcium and phosphorus metabolism. Although the number of parathyroid glands can vary, most people have four, one above the other on each side.

• Parathyroid glands control the calcium in our bodies--how much calcium is in our bones, and how much calcium is in our blood.

Thymus Gland

• The thymus gland is a pink-grey organ that lies underneath the top of the breast bone. In animals it is known as the sweetbreads.

• The thymus processes a type of white blood cell known as a T-lymphocyte. These T-lymphocytes govern cellular immunity which means they help cells recognize and destroy invading bacteria, virus, etc., abnormal cell growth such as cancer, and foreign tissue.

ADRENAL GLAND

• Lodged on top of each kidney.• Secretes Adrenalin or Epinephrine, which

gives extra energy very much needed during emergencies and prolonged stress.

PANCREAS

• is a long, tapered gland which lies across and behind the stomach

• This gland secretes digestive juices which break down fats, carbohydrates, proteins and acids; it also secretes bicarbonate, which neutralizes stomach acid as it enters the duodenum.

PANCREAS

• Islets of Langerhans- found in the pancreas secrete insulin, which prevents the accumulation of sugar in the blood.

OVARY

• Sex gland of females.• a pair of oval or almond-shaped glands which

lie on either side of the uterus and just below the opening to the fallopian tubes.

• Secrete estrogens (for the appearance of secondary sex characteristics)

• Secrete progesterone (for the thickening of the uterine wall in preparation for pregnancy and child birth)

TESTES

• male sex glands• They are located behind the penis in a pouch of

skin called the scrotum.• The testes produce and store sperm, and are

also the body's main source of male hormones, such as testosterone. These hormones control the development of the reproductive organs and other male characteristics, such as body and facial hair, low voice, and wide shoulders.

SOURCES:

• http://outreach.mcb.harvard.edu/animations/actionpotential.swf

• http://www.neurogistics.com/TheScience/WhatareNeurotransmi09CE.asp

• http://leavingbio.net/THE%20NERVOUS%20SYSTEM_files/THE%20NERVOUS%20SYSTEM.htm#All

• http://biology.clc.uc.edu/courses/bio105/endocrin.htm