Nervous/Endocrine Systems

Function of the Nervous System• Coordinates organ system activities to help maintain

homeostasis.– Homeostasis is the body’s ability to maintain a stable environment

while changes to the external environment take place.

• Nervous system is the most complex organ system.• Works closely with the endocrine system to maintain

homeostasis.– Nervous system controls the body with short, fast, electrical

impulses.– Endocrine system controls the body with long, slow, chemical

impulses (hormones).

Nervous System Divisions

• The nervous system is divided into two functional divisions.– Central Nervous System (CNS): Brain and Spinal Cord• Brain: where intelligence, memory, and emotion come from.• Spinal Cord: Integrates and coordinates the processing of

sensory data and the transmission of motor control (movement).

– Peripheral Nervous System (PNS): Nervous tissue outside the CNS…10 million in the body.• Controls the function of muscles and glands.

Peripheral Nervous System• Somatic nervous system– Overall control of skeletal muscles.

• Autonomic nervous system– Provides automatic involuntary regulation of smooth muscle

(digestive system), cardiac muscle (heart), and glands.

– Divided further into:• Sympathetic – under stressful

conditions• Parasympathetic - normal day-

to-day activities

Overview of the Nervous System

An Introduction to the Nervous System

• The nervous system sends electrical signals through special nervous tissue.

• Each nerve cell is also called a neuron: a cell that send and receive signals.

• The Structure of Neurons– Dendrites: hair like structures that receive nerve impulses.– Cell body: where organelles are found.– Axon: hair like structures that send nerve impulse to other

neurons.

Neurons

Neurons

• Nerve signals travel through neurons as electrical impulses, but when they reach the end (axon) of the nerve cell the signal is released as a chemical.– This chemical signal is called a neurotransmitter.– The chemical signal is released into the space between

adjacent nerve cells.– Synapse: the structure/open space that allows for nerve

cells to pass impulse to one another.

Reflex

• A reflex occurs when the body reacts to a stimulus without thinking about it.

• During a reflex the nerve signal goes to the spinal cord and right back out to the body to cause a reaction.– This is because we need/want to react quickly to

decrease injury.– Animation

Disorders• Paralysis occurs when a injury occurs to the spinal

cord that does not allow information from the brain to be transmitted to muscles.

ENDOCRINE SYSTEMPart 2

Function of Endocrine System

• The endocrine system controls long-term homeostasis, such as growth and development.

• It controls the body via chemical impulses called hormones.• These hormones are released from specialized organs

called glands.– Each gland releases one type of hormone, and those

hormones travel through the blood to the designated target cell or organ.

– These hormones then control the functioning of that target cell or organ.

Hormones

• Hormone control everything in our body:– Growth– Development– Reproduction– Cell metabolism– Blood sugar levels– Stress levels (both short-term and long-term)– Sleep cycle– Blood calcium levels and bone strength

Mechanism• Most hormones are under control by a process called

Negative Feedback.– Negative Feedback: • release of a hormone causes a change that suppresses

further release of that hormone• when hormone levels get too low in the blood the body

stimulates the designated gland to make and release the hormone until the levels reach homeostasis again.

– For example: in males if testosterone levels get too low in the blood, the brain signals the testes to make and release testosterone into the bloodstream, when the levels get back to normal the testes stop making and releasing the hormone.

Mechanism

• Some hormones are under Positive Control (though this is rare).– Positive Feedback: occurs when the release of a

hormone, causes more hormone to be released increasing the stimulus.

– For example: when a female is in labor, the hormones that control her labor increase as she moves through the labor process, making the uterine contractions stronger to deliver the baby.

Diabetes• One major type of endocrine disease that can occur is diabetes.– Diabetes: occurs when the body cannot control its blood

sugar levels.• When our blood sugar levels are high, our pancreas releases

insulin (a hormone) to tell our body cells to take sugar inside their cell membrane to store, this decreases the amount of sugar in our blood.– Type 1 diabetes occurs when a person’s pancreas does not make

enough insulin.– Type 2 diabetes occurs when a person’s body cells does not react to

insulin.