Lesson 3 – Nervous, Integumentary, and Digestive Systems

nervous system

most complex organ system in the body as it handles all-controlling, regulatory, and communications

integumentary system

comprises the skin and its layers.

digestive system

digestive system is responsible for digesting the food we eat and provide energy from it

Together with the endocrine system, the nervous system is responsible for

regulating and maintaining homeostasis.

nervous system is composed of

brain, spinal cord, nerves, and ganglia.

These, in turn, consist of various tissues, including nerve, blood, and connective tissue.

Central Nervous System and the Peripheral Nervous System

Central Nervous System

comprises the brain and the spinal cord

peripheral nervous system

includes the sensory and motor nerves.

includes the somatic and autonomic nervous systems.

somatic nervous system

responsible for transmitting signals from the brain to voluntary muscles

autonomic nervous system

responsible for the involuntary actions and is further divided into the sympathetic nervous system that is responsible for the fight or flight response and the parasympathetic nervous system that slows down the body’s metabolism when needed.

sympathetic nervous system

responsible for the fight or flight response

parasympathetic nervous system

that slows down the body’s metabolism when needed.

brain

controlling organ of the body

divided into the cerebrum, cerebellum, and the brain stem or the medulla oblongata.

spinal cord

continuation of the brain, and it is responsible for transmitting messages between the brain and the body

Two types of nerves carry out the activities of the peripheral nervous system

sensory nerves, motor nerves

sensory nerves

carry information from the body to the CNS

motor nerves

carry information from the CNS to the muscle

The various activities of the nervous system can be grouped as ___ overlapping functions:

3

Sensory

Integrative

Motor

sensory input

Millions of sensory receptors detect changes, called stimuli, which occur inside and outside the body. They monitor such things as temperature, light, and sound from the external environment. Inside the body, the internal environment, receptors detect variations in pressure, pH, carbon dioxide concentration, and the levels of various electrolytes.

Sensory input is converted into, this is called ____

integration

electrical signals called nerve impulses that are transmitted to the brain. There the signals are brought together to create sensations, to produce thoughts, or to add to memory; decisions are made each moment based on the sensory input.

Based on the sensory input and integration, the nervous system responds by

sending signals to muscles, causing them to contract, or to glands, causing them to produce secretions.

Muscles and glands are called ____

effectors because they cause an effect in response to directions from the nervous system. This is the motor output or motor function.

neurotransmitters

Nerve cells in the nervous system communicate using chemicals called neurotransmitters

multiple sclerosis,

body’s immune system attacks myelin, a fatty substance forming a sheath around nerves.

Nerve fibers

are wrapped in a layer of insulation, like the insulation around an electrical wire. This insulation is known as a myelin sheath which enables signals to be conducted with speed and accuracy.

synapse

The point at which two neurons meet

Skin

largest organ in the body and covers the body’s entire external surface.

It is made up of three layers, the epidermis, dermis, and the hypodermis,

barrier against pathogens, UV light, chemicals, mechanical injury

regulates temperature and the amount of water released into the environment.

first site of immunological defense.

skin preserves ___

homeostasis by regulating temperature and water loss, while also serving both endocrine and exocrine functions.

endocrine functions

include the production of vitamin D with the assistance of UV light from the sun.

macromolecules that can’t be absorbed intact

proteins, fats, and starch,

Regions of the digestive system can be divided into two main parts

the alimentary tract and accessory organs.

alimentary tract

composed of the mouth, pharynx, esophagus, stomach, small and large intestines, rectum, and anus.

accessory organs

salivary glands, liver, gallbladder, and pancreas.

abdomen

large cavity that houses these organs of digestion and excretion.

It is the second-largest cavity of the body and is divided into four quadrants for easy understanding and identification.

mouth

or oral cavity

first part of the digestive tract. It is adapted to receive food by ingestion, break it into small particles by mastication, and mix it with saliva.

lips, cheeks, and palate form the boundaries.

oral cavity contains

teeth and tongue and receives the secretions from the salivary glands.

Food is forced into the

by the tongue and the esophagus is a collapsible muscular tube that serves as a passageway between the pharynx and stomach.

stomach

responsible for receiving the food and mixing it with gastric juices present in it.

The stomach mixes food with acid to begin digestion.

stomach lining is protected from acid by a layer of mucus and bicarbonate. Stomach ulcers may occur when this layer is disrupted, resulting in painful inflammation.

small intestine

finishes the process of digestion, absorbs the nutrients, and passes the residue on to the large intestine.

Small finger-like structures called microvilli, increase the surface area for absorption

liver, gallbladder, and pancreas

accessory organs of the digestive system that are closely associated with the small intestine.

large intestine

produces no digestive enzymes. Chemical digestion is completed in the small intestine and the large intestine is responsible for the absorption of water and electrolytes and the elimination of feces.

last 2 to 3 cm of the digestive tract

anal canal, which continues from the rectum and opens to the outside at the anus.

liver

produces bile, a substance that helps absorb fats, into the gallbladder. Bile passes from the gallbladder into the intestine.

Bile carries toxins out of the body and contains substances that help absorb nutrients.

largest gland in the body and is divided into two major and minor lobes.

pancreas

releases enzymes into the small intestine that help the breakdown of food. Additionally, the pancreas releases hormones such as insulin into the bloodstream where the insulin helps control blood glucose levels.

salivary gland functions

produces saliva that in turn,

Has a cleansing action on the teeth.

Moistens and lubricates food during mastication and swallowing.

Dissolves certain molecules so that food can be tasted.

Begins the chemical digestion of starches through the action of amylase, which breaks down polysaccharides into disaccharides.

Liver functions include the following:

Secretion

Synthesis of bile salts

Synthesis of plasma protein

Storage

Detoxification

Excretion

Carbohydrate metabolism

Lipid metabolism

Protein metabolism, and

Filtering

gallbladder

storage reservoir for bile, a yellowish-green fluid produced by liver cells, and it is responsible for breaking down the food.

endocrine function of pancreas

consists of the scattered islets of Langerhans, which secrete the hormones insulin and glucagon into the blood.

exocrine portion

consists of pancreatic acinar cells that secrete digestive enzymes to break down the food.