1. Human Systems: Nervous System & Sense Organs

2. Nervous system

3. The nervous system Need for communication
Communication is required for coordination
Gather information
Process information
Respond accordingly

4. The nervous system
Nervous system has two parts (central and peripheral)
Central nervous system (CNS) – brain and spinal cord
Peripheral nervous system (PNS) – other parts of the nervous system
The CNS processes and responds to all messages coming from the peripheral nervous system
The PNS connects all parts of the body to the CNS
It uses specialized structures called nerves to carry information between body and CNS

5. The nervous system

6. Neurons
Nervous system is made up of cells known as nerve cells or neurons
Cell body, axon and dendrites
Nerve cells are connected to each other

7. Nerves
A nerve is a collection of axons bundled together with blood vessels and connective tissue
Nerves are found everywhere in the PNS
Most nerves have axons of both sensory neurons and motor neurons

8. Nerves

9. Peripheral nervous system
Sensory neurons – gather information
Special nerve endings called as receptors
Motor neurons – send impulses from brain and spinal cord to other parts of the body e.g. muscle, sweat glands etc.

10. Peripheral nervous system
PNS has two types of motor neurons – somatic and autonomic
Somatic - under conscious control (voluntary movements such as writing, talking, smiling, or jumping)
Autonomic - controls body functions that you do not think about, such as digestion and heart rate
Maintain body’s functions in balance
Depending on the situation, the autonomic nervous system can speed up or slow down these functions
The autonomic nervous system has two divisions: the sympathetic nervous system and the parasympathetic nervous system

11. Peripheral nervous system

12. Central nervous system
The central nervous system receives information from the sensory neurons
Then it responds by sending messages to the body through motor neurons in the PNS
Made up of brain and spinal cord

13. Brain Largest organ in the nervous system
Different parts perform different functions
Cerebrum
Largest part of the brain
Controls voluntary movements
It also allows to sense touch, light, sound, odors, taste, pain, heat etc.
The cerebrum is made up of two halves, called hemispheres.
The left hemisphere directs the right side of the body, and the right hemisphere directs the left side of the body

14. Brain

15. Brain
Cerebellum
The second largest part of your brain and lies beneath the back of the cerebrum
The cerebellum processes sensory information from the body, such as from skeletal muscles and joints
This allows the brain to keep track of the body’s position

16. Brain Medulla The medulla connects brain to the spinal cord
Controls involuntary processes such as involuntary breathing, the regulation of blood pressure and heart rate
Medulla constantly receives sensory impulses from receptors in blood vessels and uses this information to regulate blood pressure
The medulla also sends impulses to the heart to make the heart beat faster or slower

17. Brain

18. Spinal cord Spinal cord
It is made of neurons and bundles of axons that pass impulses to and from the brain
The spinal cord is surrounded by protective bones called vertebrae
The axons in spinal cord allow the brain to communicate with PNS
The axons of sensory neurons in skin and muscles carry impulses to the spinal cord
The spinal cord relays these impulses to the brain
The brain interprets these impulses as pain, temperature, or other sensations and responds to the situation

19. Spinal cord

20. Spinal cord Spinal cord injury
May block information flow to and from the brain
Paralysis

21. Sense organs

22. Sense of touch
Skin – integumentary system (which includes hair, skin, nails)
Protect body from damage
Glands and receptors
Reflex
Skin and feedback mechanism
(Body temperature)

23. Sense of sight Eyes detect light and brain forms visual images
Cornea and retina
Mechanism of vision

24. Sense of sight
Reacting to light – role if iris
Focusing light

25. Sense of hearing Sound and vibrations Ear – outer, middle and inner
Outer ear
Pinna and ear canal
Middle ear
Tympanic membrane or ear drum
Bones (hammer, anvil and stirrup)
Inner ear
Cochlea and auditory nerve
Fluid and balancing body

26. Sense of hearing

27. Sense of taste
Taste is the sense that detects chemicals and to distinguish flavors
The tongue is covered with tiny bumps called papillae which contain taste buds
Taste buds contain clusters of taste cells, the receptors for taste . They respond to dissolved-food molecules
Taste cells react to five basic tastes: sweetness (sugar), sourness (lemon), saltiness (salt), savoriness (meats and cheeses), and bitterness (some medicines)
When the brain combines information from all of the taste buds, you taste a “combination” flavor

28. Sense of taste

29. Sense of smell
The receptors for smell are located on olfactory cells in the upper part of your nasal cavity
An olfactory cell is a nerve cell that responds to chemical molecules in the air. You smell something when the receptors react to molecules that have been inhaled
The molecules dissolve in the moist lining of the nasal cavity and trigger an impulse
Olfactory cells send those impulses to the brain, which interprets the impulses as odors
Taste buds and olfactory cells both detect dissolved molecules
The brain combines information from both senses to give sensations of flavor.

30. Sense of smell