1. The Digestive and Nervous Systems
Lesson 16
February 10th, 2011

2. QUIZ on monday

3. The Digestive system
Animals rely on the digestive system to break down food into nutrients, which are then absorbed and transported by the circulatory system.
Body cells require nutrients for growth, maintenance, and repair.

4. There are four stages of food processing.
Ingestion – the taking in of nutrients
Digestion – The breakdown of complex organic molecules into smaller components by physical and chemical means
Absorption – the taking up of digested materials into the cells of the digestive tract
Egestion – the removal of waste food materials from the body.

5. The digestive tract is also responsible for the detection and expulsion (vomiting) of foods that release certain bacteria (poisonous, rotten or spoiled foods).

6. In humans the digestive system is really one long tube, open at both ends, called the gastrointestinal tract.
It includes the following parts:
- next slide

7. Mouth
Esophagus
Stomach
Intestines
Liver
Pancreas
Gall Bladder

8. In humans the digestive system is really one long tube, open at both ends, called the gastrointestinal tract.
It includes the following parts:
- next slide

9. Mouth
Esophagus
Stomach
Intestines
Liver
Pancreas
Gall Bladder

10. The Mouth – Ingestion and Digestion
Digestive processes begins in the mouth
Teeth physically breakdown food into smaller pieces
The structure of teeth determines its function.
Molars crush and grind
Incisors cut food
Bicuspids and canines pierce and tear

11. The Mouth – Ingestion and Digestion
Salivary glands secrete saliva (water, mucus and amylase) which chemically breaks down food.

12. Esophagus
The esophagus is a muscular tube connecting your mouth to your stomach. The lining is a smooth muscle tissue which can relax and contract involuntarily to swallow food (peristalsis).

13. Stomach – Digestion
Muscles called sphincters control the movement of food in and out of the stomach
The stomach contracts and relaxes muscles to churn and break down food.

14. Stomach – Digestion
Hydrochloric acid and enzymes are secreted, these break down fibrous tissue.
Mucus protects the stomach lining from the gastric juices
Only a small amount of absorption is done in the stomach

15. Small intestine - Digestion
7 meter long ( almost 4 times the length of your body)
2.5 cm in diameter
Most digestion is done in the duodenum
Due to secretions of the pancreas and liver

16. Liver produces bile which breaks down fat
Bile is stored in the Gallbladder
The liver also stores carbohydrates, vitamins and detoxifies toxins.

17. Pancreas Produces sodium bicarbonate (buffer)
Raises the pH to protect the small intestine
Releases enzymes which break
down fat and protein.

18. Small Intestine and Large Intestine – Absorption
Small projections in the small intestine called Villi increase the surface area to help absorption into the blood stream.

19. Small Intestine and Large Intestine – Absorption
The large intestine is 1.5 meters long
Absorbs water
Bacteria in the intestine produce vitamin K and B

20. Large Intestine ­– Egestion
Cellulose cannot be digested in humans and is the main component of feces
As waste builds up the body prompts the large intestine to void the waste.
This is important as feces contains toxins that are potential harmful to the body.

21. The Nervous System

22. The Nervous System
As the most complex system, the nervous system serves as the body control center and communications electrical-chemical wiring network.
It detects, interprets, and responds to changes in internal and external conditions.
The nervous system integrates countless bits of information and generates appropriate reactions by sending electrochemical impulses through nerves to effector organs such as muscles and glands

23. The Nervous System
As the most complex system, the nervous system serves as the body control center and communications electrical-chemical wiring network.
It detects, interprets, and responds to changes in internal and external conditions.
The nervous system integrates countless bits of information and generates appropriate reactions by sending electrochemical impulses through nerves to effector organs such as muscles and glands

24. The Nervous System
A change in the environment is detected by your body is called a stimulus. The control system that enables animals to detect a stimulus and coordinate a response is called the nervous system.

25. The nervous system in our body has 2 main parts
CNS – Central Nervous System (brain and spinal cord)
PNS – Peripheral Nervous System ( All other nerves in the body)

26. PNS 1. Somatic Nervous system (voluntary)
2. Autonomic Nervous system (involuntary)

28. Brain
The brain has billions of neurons that receive, analyze, and store information about internal and external conditions. It is also the source of conscious and unconscious thoughts, moods, and emotions.

29. Brain The brain controls Muscle co-ordination Vital body functions
Thought
Information co-ordinated from our senses
Internal control (balance) of our systems

30. Spinal cord
Controls two way information between the brain (CNS) and our sensory and motor nerves (PNS)

31. Peripheral Nervous System
The peripheral nervous system (PNS) connects the central nervous system (CNS) to sensory organs (such as the eye and ear), other organs of the body, muscles, blood vessels and glands.
Has two components.

32. PNS
1. The somatic nervous system, or voluntary nervous system, enables humans to react consciously to environmental changes. This system controls movements of skeletal (voluntary) muscles.

33. Autonomic Nervous system
The autonomic nervous system or involuntary nervous system maintains homeostasis. This system works automatically and without voluntary input.
Its parts include receptors within viscera (internal organs), the afferent nerves that relay the information to the CNS, and the efferent nerves that relay the action back to the effectors.
The effectors in this system are smooth muscle, cardiac muscle and glands, all structures that function without conscious control.

34. ANS
The nerves that send information back to the organ are then divided into two systems.
Sympathetic system - Prepares your body for “flight or fright”
Parasympathetic system – Calms your body

35. The Reflex Arc
A predictable, automatic, and unlearned (innate) reaction.
Only reaches the CNS in the spinal cord, thus it is automatic.

36. Reflex Arc
1. A sensory neuron senses a stimulus and sends an impulse to the spinal cord
2. A interneuron in the spinal cord transfers the impulse to a motor neuron without involving the brain directly
3. A motor neuron carries the response impulse to a muscle and makes it contract. The brain will receive a delayed pain message if the response was done to protect the body.

37. Reflex Arc

38. Homework: - hand in
What two things does the mouth do to contribute to digestion?
What is the difference between Ingestion and Egestion?
Where is most absorption of nutrients done in the body?
What is the purpose of the Liver, gallbladder and pancreas?
Summarize the whole process from start to finish.
What is the purpose of the CNS?
What is the purpose of the PNS