1. Nervous System
AP Biology

2. Nervous System
In order to survive and reproduce an organism must respond rapidly and appropriately to environmental stimuli in order to send the “right” messages at the “right” time to the “right” places.
The nervous system provides a “speedy” communication system so the organism can quickly respond to internal and external stimuli.

3. The Neuron Neuron = Nerve cell Functional unit of the nervous system
Conveys outgoing message to other cells (neurons/muscles/glands)
Release neurotransmitters into the synapse (space between neuron and effector cell)
Insulating layer that helps propagate the signal
Receives incoming messages and sends it to the cell body
Plays role in summation and transmission of the signal
Neuron = Nerve cell
Functional unit of the nervous system

4. The Synapse
Connects presynaptic and postsynaptic cells

5. 3 overlapping functions of NS

6. Central and Peripheral NS
Sensory Input
PNS – sensory receptors detect stimuli
Integration
CNS (Brain and spinal cord) makes an interpretation and association with appropriate response
Motor output
PNS – motor receptors to effector cells (muscle cells or glands)

7. The Brain (integration) … cerebrum
The proportion of somatosensory or motor cortex devoted to a particular part of the body is correlated with the relative importance of sensory or motor information for that part of the body
Reasoning, Problem Solving
Sends commands to skeletal muscle
Receives and integrates signals from touch, pain, pressure, and temperature receptors

8. The Homunculus
This homunculus, or “little human”, is a visual representation that shows the connection between different body parts and brain devotion to those areas. The bigger the body parts in the picture or model, the more brainpower there is dedicated to detecting sensatory input received by the somatosensory cortex.

10. Reflex vs. Response

11. Glial Cells Astrocytes Oligodendrocytes Schwann cells
Structural and metabolic support
Tight junctions (blood brain barrier)
Oligodendrocytes
Form insulating myelin sheaths around axons in the CNS
Schwann cells
Form insulating myelin sheaths around axons in the PNS

12. Action Potential Review

13. Membrane Potential Arises from:
Difference in ion concentration on the inside and outside of the cell membrane
Selective permeability of the membrane

14. Excitable Cells
Cells that have the ability to generate large changes in their membrane potentials.
May result in an electrical impulse
Examples:
Neurons
Muscles

15. Action Potential
A change in the membrane potential caused by a received stimuli
Causes selective opening of sodium channels

16. Action Potential Nerve impulse
Strong enough stimulus causes depolarization to reach threshold

17. Responding to Stimulus
Hyperpolarization – becomes even more negative
Depolarization – becomes less negative
Threshold – charge required to create action potential

18. Resting Potential (-70 mV inside)

19. Activation Gate opens due to stimulus

20. Voltage gated channels open: more Sodium (Na+) gates open in response to less negative charge

21. Potassium (K+) channels open (voltage gated channel)
Inactivation gate (Na+) closes in response to voltage
Potassium (K+) channels open (voltage gated channel)

22. Undershoot = refractory (sodium channels are closed … no more action potentials)

23. Sodium-Potassium Pump

25. Note: Voltage sensitive calcium channels open at the axon terminals and cause the synaptic vesicles to release neurotransmitters.

26. Strong vs. Weak Stimulus
More Action Potentials in the same amount of time.

27. Definitions: presynaptic cell postsynaptic cell synaptic cleft
before synapse
postsynaptic cell
after synapse
synaptic cleft
separates pre/post
synaptic vesicle
contains neurotransmitters
neurotransmitter
chemical messenger released into synapse
presynaptic membrane
synaptic terminal that faces the cleft
postsynaptic membrane
cell body or dendrite on other side of synapse

28. Neurotranmitters Acetycholine Norepinephrine Dopamine Serotonin
Excitatory to skeletal muscle
Inhibitory to cardiac muscle
Norepinephrine
Excitatory or inhibitory
Dopamine
Excitatory
Serotonin
Inhibitory
Glutamate
Excitatory in rods (dark)
Endorphins
Inhibitory

30. Somatic and Autonomic NS
Carries signals to skeletal muscles
Responds to external stimuli
“Voluntary”
Regulates the internal environment
Controls smooth and cardiac muscle and organs of GI, CV, excretory, and endocrine systems
“Involuntary”

31. Calming
and
Self-main-
tenance
Arousal
and
Energy
generation

32. Forebrain and Brainstem

33. Forebrain Telencephalon = cerebrum Diencephalon
integration center / thought processes
personality, speech, reasoning, emotion
Diencephalon
thalamus = relay station to cerebral cortex
hypothalamus = maintains homeostasis by regulation of many body functions; heart rate, bp, digestion, sleep cycle, libido, hunger, and thirst.

34. Brainstem Midbrain Pons Medulla oblongata
inferior colliculi - auditory system
superior colliculi - visual system
reticular formation - regulates states of arousal (sensory filter)
Pons
links cortex with cerebellum; controls facial expression
Medulla oblongata
helps regulate visceral (autonomic) functions such as breathing, heart rate, blood vessel activity, sneezing, sleeping, digestion, swallowing, vomiting

35. Arousal vs. Sleep arousal - state of awareness of the external world
sleep - receive external stimuli, but not conscious of them
What controls arousal and sleep:
several centers in the cerebrum and brainstem
reticular formation extends from medulla to thalamus and serves as a sensory filter determining what information reaches the cortex
Pons and medulla have nuclei that cause sleep when stimulated
the neurotransmitter serotonin is thought to be involved
milk (can cause tiredness) has a large quantity of tryptophan, which is the amino acid from which serotonin is synthesized

36. Cerebellum
receives sensory information about position of joints, and length of muscles
receives visual and auditory information
receives motor input from the cerebrum
provides automatic coordination of movement and balance

37. Corpus Collosum
Thick band of fibers that connect the 2 cerebral hemispheres

38. 4 Lobes of the Brain
Frontal = frontal association area = personality; speech
Parietal = somatosensory association area = taste, speech, reading
Occipital = visual association area = vision
Temporal = auditory association area = smell, hearing

39. Cortical areas btwn frontal and parietal
somatosensory cortex
mosaic of regions corresponding to different parts of the body
increased surface for parts of increased importance
integrates signals from touch, pain, pressure, and temperature receptors
 motor cortex
sends commands to skeletal muscles signaling appropriate response to sensory stimuli

40. Severed CC, Key in left hand
Closed
They can use the key / know its function, but they can’t tell you what it is because the speech association center is in the left side of the brain and it is the right side of the brain that receives information about the key because it is in your left hand.
Sensory input and spoken response are dissociated.
 Open
You should be able to identify it and use it! You see it with both eyes, thus each side of the brain gets the information without communication with other half.

41. Roles of Brain Hemispheres
Left
Speech
Language
Calculation
b) Right
Creative ability
Spatial perception

42. Association Area Roles
Parietal Lobe - speech / reading centers obtain visual information, stores the information, and arranges the words into meaningful speech according to the rules of grammar
Frontal Lobe - relay system; receives input from the Parietal lobe and tells the motor cortex what to do
Motor cortex - Moves the tongue, lips and other speech muscles to articulate words

43. Memory
The ability to store and retrieve information related to previous experience
Short-term memory
immediate sensory perception of an object or idea before the image is stored
Long-term memory
can be recalled several weeks later
need repetition or some favorable emotional state or an association with new and previous data

44. Long-term potentiation
Enhanced response of postsynaptic cell to an action potential
Glutamate is the neurotransmitter involved
opens Ca++ channels
Ca++ goes into cell and causes it to depolarize
Positive feedback system?
postsynaptic cell causes presynaptic cell to release more glutamate
Pathway to a memory:
sensory signals form eye to visual centers in occipital lobe
sensory filter, reticular formation, to determine sense of importance
hypothalamus / limbic system - determines if emotion should be involved
forebrain (prefrontal cortex) - higher-level integration
back to the cortical vision centers where perception first occurred