1. Regulation of Body Processes

2. Responses to both internal and external stimuli must be regulated and coordinated
These responses are controlled by the body’s nervous and endocrine systems

3. Nervous System: Endocrine System:
sends electrochemical signals using neurons
Endocrine System:
sends chemical signals by using hormones secreted by glands.

4. Mechanisms of Nervous Regulation
Receptors:
sensory organs with specialized structures that are sensitive to changes or “stimuli”
When stimulated, receptors cause impulses to be carried both electrically and chemically between nerve cells.

5. Sensory Organs Include: Stimuli They Respond to:
eyes, nose, skin, taste buds, ears
Stimuli They Respond to:
Physical forces
Ex: heat, cold, pressure, light
Chemical changes
inside and outside organism

6. Effectors: specialized structures that respond to commands of nervous system
gland (increases or decreases secretion)
muscle (contracts)

7. Nerve Cells (Neurons)
Carry electrochemical messages or impulses from receptor to effector
Stimulus occurs
Receptor senses stimulus
Impulses sent along nerve pathway
Effector responds
Nerve = many neurons bundled together

8. Types of Neurons Sensory Neurons Motor Neurons Interneurons
Carry impulses from receptors to spinal cord and brain
Motor Neurons
Carry impulses from brain and spinal cord to effectors (muscles)
Interneurons
Relay impulses between neurons, (found in brain and spinal cord)

9. Basic Neuron Structure
Cell Body:
contains nucleus and cell organelles
Carries out metabolic activities and controls growth
Dendrites:
short highly branched fibers
receive impulses

10. Axon: Schwann Cells: long thin fiber that extends away from cell body
Carries impulses from dendrites to terminal branches
Schwann Cells:
Surround axons of many vertebrates
Produce myelin which forms an insulating covering around axon
Gaps between cells are called Nodes of Ranvier

11. Terminal Branches: Synapse: Branches at end of axon
End in “synaptic knobs” that contain neurotransmitters
They lie very close to dendrites of other neurons
Chemical communication of a nerve impulse happens between neurons here
Synapse:
small gap between synaptic knob of one neuron and dendrite of another

12. How does Signal Travel Along a Neuron?

13. Sending a Nerve Impulse
Electrical Signal Travels:
At rest: nerve membrane is “polarized”
Outside is +, inside is –
During Impulse:
Switch in polarity travels along the nerve cell

14. Myelination of axon helps to insulate the signal and it conducts faster
Signal can jump quickly between Nodes of Ranvier

16. Sending a Nerve Impulse
Chemical Communication Occurs Between Neurons:
Happens at the synapse
Tiny gap between synaptic knob of one neuron and dendrite of another
Electrical impulse triggers release of neurotransmitter molecules from vesicles into the synapse
Ex: acetylcholine, seratonin

18. That neuron will now “fire” and send signal along itself
These molecules bind to specific receptor proteins in the membrane of the adjoining neuron
That neuron will now “fire” and send signal along itself
Impulses travel in one direction across a synapse
Synapse and Neurotransmitters:

19. Note:
Each neurotransmitter will only bind to a specific receptor that it will “fit”
Certain drugs mimic the effects of neurotransmitters by binding to these receptor molecules

20. Stopping a Signal:
After a signal is sent enzymes at the synapse break down the neurotransmitters in the synapse or they are reabsorbed back into vesicles.

21. Electrical, Chemical, Electrical Chemical…
Neuron Firing Animation:

22. The Neuromuscular Junction
Synaptic point of contact between motor neurons and muscle cells
Motor neurons end in “motor end plates” that release the neurotransmitter acetylcholine
These molecules bind with receptors in membrane of muscle cells causing them to contract.

24. Drugs and the Synapse
Certain poisons and drugs can effect activity of neurotransmitters
Ex: nerve gas, botulin toxin (botox), insecticides, venom
Can cause muscular paralysis and even death

25. Stimulants: speed up nervous response
Caffeine, amphetamines, cocaine
Depressants: slow down nervous system
alcohol, marijuana, barbiturates
LSD: (hallucinogenic)
blocks enzyme that removes neurotransmitter serotonin from synapse.
It remains in gap and keeps neurons firing.

26. The Human Nervous System
Divided into the:
Central Nervous System:
Brain
Spinal Cord
Peripheral Nervous System
Somatic: controls skeletal muscles (voluntary)
Autonomic: controls smooth muscles (involuntary)

27. Central Nervous System
Brain and Spinal Cord
Receive impulses from sense receptors
Interprets information
Sends impulses for responses to muscles and glands

28. The Brain Large mass of neurons located in the cranial cavity.
Covered and protected by tough membranes called meninges.
Cerebrospinal fluid surrounds brain and cushions against shock
One of the most active organs of the body, major user of glucose!

29. Concussion: when brain is severely shaken
Meningitis: membranes that surround the brain and spinal cord get infected

30. Parts of the Brain Cerebrum Cerebellum Medulla
Center for voluntary activity
Interprets sensory impulses
Initiates some motor activities
Responsible for memory, thinking and reasoning
Cerebellum
Coordinates motor activities
Aids in maintaining balance
Medulla
Controls involuntary activities such as breathing, heartbeat, blood pressure and peristalsis (is part of the brain stem)
Most “primitive” part of brain

31. Know the Three Parts of the Brain and What They Do!

32. Hemispheres of the Brain
Each hemisphere controls the opposite side of the body.

33. Brain Size and Intelligence

34. Spinal Cord
Protected by vertebrae of spinal column and rings of cartilage
Surrounded by meninges and cerebrospinal fluid
Coordinates activities between the brain and peripheral nervous system
The center for reflex action

35. Getting a Spinal Tap

36. Peripheral Nervous System
All neurons and nerve fibers outside of brain and spinal cord.

37. Responsible for voluntary movement Under conscious control
Somatic System
Connects brain and spinal cord to skeletal muscles, skin and sensory organs
Responsible for voluntary movement
Under conscious control
Ex: moving arms, legs, watching TV, listening to music

38. Relays information to and from internal organs Involuntary movement
Autonomic System
Relays information to and from internal organs
Involuntary movement
Not under conscious control
Ex:
Rate of heart beat, breathing, peristalsis in digestive tract

39. Turning Responses On and Off
Sympathetic Nervous System
Generally speeds up autonomic processes
Responsible for “fight or flight” response
Ex: Urinary Muscles contract, pupils contract, saliva secreted
Parasympathetic Nervous System
Generally slows things down
Ex: Urinary Muscles relax, pupils dilate, saliva stopped

40. Somatic vs. Autonomic
Muscle
Organ

41. Reflexes Involuntary response to a stimulus Simple pathway:
Part of somatic nervous system
Simple pathway:
Receptor - spinal cord - effector
Many normal body functions controlled this way
Ex: Blinking, sneezing, coughing
Pupil size in response to light:

42. Why do doctors check reflexes?
If you do not have a response to a reflex, something is wrong with your nervous system.
Ex: Pupils “fixed and dilated”

43. Pathway nerve impulses travel in a reflex
Reflec Arc
Pathway nerve impulses travel in a reflex
Simplest have only one sensory neuron and one motor neuron
Ex: knee jerk response

44. Reflex Arc Most reflexes involve 3 or more neurons Sensory Neuron
hand pulling back from burn or pain (withdrawal reflex)
Sensory Neuron
Interneuron (in spinal cord)
Motor Neuron

46. Reflexes in Babies

47. Disorders of the Nervous System
Polio: viral infection that affects motor function and can cause paralysis
Stroke: a burst blood vessel in the brain, causing cerebral hemorrhage. Can cause brain damage, paralysis, death
Cerebral Palsy: birth disorder, causes problems with motor function
Multiple Sclerosis: myelin coating around neurons degenerates affecting motor function.
Meningitis: inflammation of membranes surrounding brain or spinal cord.

48. Adaptations for Nervous Regulation
Protists
No true nervous system
Can respond to certain stimuli
Can tell food from nonfood, strong light, harmful chemicals
Can respond to irritants in environment
Paramecium have neurofibrils that connect cilia on membrane and coordinate their beating

49. Hydra
Has a nerve net
Nerve cells form a network between two cells layers of body
Impulses travel in all directions
Coordinates movement of tentacles to bring in food
Whole body tend to respond to a stimulus at once
Time Lapse Video of Hydra Moving

50. Earthworm Central Nervous System: Peripheral Nervous System:
“brain” connected to pair of ventral nerve cords with ganglia in each segment
Peripheral Nervous System:
Sensory receptors in skin for light, vibrations, chemicals
Motor neurons from nerve cord to muscles and glands

51. Grasshopper Dorsal “Brain” made of fused ganglia
Ventral nerve cord with series of fused ganglia
Peripheral nerves branch from ganglia to muscles, sensory organs
Complex sensory organs include tympana, eyes, antennae

52. Crash Course: The Nervous System