Nervous System: From Cells to Body Organization

1. NervousSystem

2. You’ve Gotta Lotta Nerve!”

3. Body Organization • Cells  Tissues  Organs  Organ Systems  Body • Cardiac Cells  Cardiac Muscle  Heart  Circulatory System  Body • Four Tissue Types • Muscle – controls internal & external movement • Epithelial – Covers body surface, lines organs • Connective – Holds organs in place, connect body parts • Nervous – senses & responds to environment

5. Homeostasis • Maintaining a stable internal env. • Ex – body temperature, blood sugar levels, etc.

6. The Nervous System • Controls and coordinates functions throughout the body and responds to internaland externalstimuli

7. The Neuron • Cell that transmits nerve impulses

8. Three Types of Neurons • Sensory --body to brain 2. Interneuron– connect sensory and motor neurons in CNS 3. Motor neuron --brain to body

10. Largest part neuron is = cell body • Cell body contain nucleus and cytoplasm • Dendrites- branches extending out of the cell body that carry impulses from environmentto cell body • Axon– long fiber carries impulses away from cell body • Myelin sheath- membrane covering the axon

11. What if you had no brain or nerves? • You wouldn’t be able to see, hear, smell, or talk.

12. Nerve Impulses • Electrical signals that carry messages in the nervous system. • Begins when a neuron is stimulated by another neuron or by its environment. • Involves Na+ (sodium) and K+ (potassium)

13. Na+/K+ Pump

14. Action Potential • Occurs when a neuron is stimulated by another neuron • Minimum level of stimulus required to activate a neuron is a threshold.

15. Synapse • Space between axon terminal of one neuron and dendrites of next neuron • Neurotransmitters allow the impulse to “jump” across the synapse • Action potential causes vesicles in axon terminal to release NT into synapse

16. All or None Principle • Stimulus must pass a threshold to trigger an impulse • However, a strong stimulus does not create a strong impulse • The neuron is either on or off – all or none

17. The Nervous System

18. The Central Nervous System • Brain • Spinal Cord • Surrounded by meninges (membranes) and cushioned by cerebrospinal fluid

19. The Brain • Four lobes, two halves • Major regions: • Cerebrum– conscious activity/thought • Cerebellum– coordinates movement • Brain stem – connect brain and spinal cord, controls many involuntary fxns • Thalamus – receives sensory messages • Hypothalamus – controls primitive needs and emotions

20. The Brain

22. The Spinal Cord • 31 pairs of nerves branch off • Controls reflex arc

23. Peripheral Nervous System • All nerves outside of brain and spinal cord • Sensory – receives internal and external stumuli • Motor – controls muscles and glands

24. Peripheral Nervous System • Somatic NS – controls all voluntary activity • Autonomic NS – involuntary activity • Sympathetic – controls body during times of stress, • Ex - speeds up heart rate • Parasympathetic – controls body normally, returns body to normal state after stress • Ex – slows heart rate

26. The Five Senses “Come to your senses”

27. The Five Senses • Sense organs contain sensory receptors • Five types • Pain receptors • Thermoreceptors(temperature) • Mechanoreceptors(touch and sound) • Chemoreceptors(taste and smell) • Photoreceptors(rods and cones)

28. Touch: Do You Feel Like I Do • Sensory receptors skin pick up different messages & transmit to brain. • Different sensations: • Pain • Pressure • Hot • Cold • Some travel faster than others: Ex: cold & pressure travel faster than pain.

29. The Ear • Sound wave vibrations transmit through tympanic membrane to oval window to fluid filled cochlea • Tiny hairs in cochlea move in response to fluid vibration • Hairs produce nerve impulses to brain

30. Balance • Semicircular canals above cochlea • Filled with fluid • When you move, the fluid moves • Tiny hairs sense fluid movement and send impulse to brain

31. Sound waves funneled into inner ear. Sound waves make 3 tiny bones vibrate Vibration makes cochlea vibrate & convert waves to electrical impulses. Travel to brain by auditory nerve. Brain interprets the sounds Ear: Do You Hear What I Hear?

32. Cornea – clear covering on front of eye. Pupil – opening in eye that allows light in. Iris – muscles control the opening of pupil – different colors Eyes: Seeing the Light

33. Retina – in the back of the eye – specialized sensory cells that detect and convert the image to an electrical message that travels to the brain – interprets the image. Image is upside down. Rods – detect black, white, gray shades – dim light Cones – detect color, bright light. Eyes

36. Focuses light entering eye & projects it onto retina. Changes shape to adjust focus. Nearsightedness –image focused in front of retina Farsightedness image focused behind retina Lens

37. Your Nose Knows • Nose- olfactory cells – sensory receptor cells in nose that detect smell. • Taste – occurs when taste buds (receptor cells located on the tongue) are stimulated. • Brain interprets message • 4 Kinds: • Sweet • Sour • Salty • Bitter