1. Organization of the Nervous System
Central Nervous System
The brain + the spinal cord
The center of integration and control
Peripheral Nervous System
The nervous system outside of the brain and spinal cord
Consists of:
31 Spinal nerves
12 Cranial nerves

2. Central Nervous System (CNS)
contains fluid-filled spaces which contain cerebrospinal fluid (CSF).
White matter is composed of bundles of myelinated axons
Gray matter consists of unmyelinated axons, nuclei, and dendrites.

3. Figure 48.16x Spinal cord
White Matter
Gray Matter

4. Figure 48.20 The main parts of the human brain

5. Corpus callosum Midbrain Thalamus Pons Hypothalamus Medulla oblongata
This is a slice right down the mid line, mid-saggital.
Cut his face off to ensure anonymity.
You can see the cerbral cortex on top and the top surface of those sulci and gyri as it dips down the middle, and the cerebellum
A striking feature is a big white wodge in the middle - it is white because you have cut right through the middle of a load of myelinated fibres that connect the two hemispheres = corpus callosum
Below that the septum pelucidum (but the ventricles are the important bit) - produce CSF
Then thalamus - last relay for sensory information before the cortex
Hypothalamus - controls the pituitary gland below it
Midbrain - start of connection to the spinal cord
Pons - lots of fibres connecting the two halves of the cerebellum
Brain stem = medulla oblongata - connects to spinal cord
In coronal section you see next to nothing in the real slices, so here is Pocock and Richards picture
Medulla
oblongata

6. Figure 48.28x1 Brain MRI

7. But here is a real one.

9. Mapping Language Areas of the Cerebral Cortex
Max
Min

10. Figure 48.27 The limbic system

11. Structure and Function
Brain stem--Consists of the medulla oblongata, pons, and midbrain.
Functions in homeostasis, coordination of movement, conduction of impulses to higher brain centers
Medulla Oblongata- Breathing, heart and blood vessel activity, swallowing, vomiting, digestion, and relays information to and from higher brain centers
Pons- involved in the regulation of visceral activities such as breathing and relays info. to higher brain

12. Midbrain-integration of sensory information, in the regulation of visual and auditory reflexes, and relays as well
Cerebellum
Functions to error-check and coordinate motor activities, and perceptual and cognitive factors. Relays sensory information about joints, muscles, sight, and sound to the cerebrum. Coordinates motor commands issued by the cerebrum; maintains posture

13. Diencephalon:
Thalamus- gateway for sensory impulses heading to cerebral cortex, receives all sensory impulses (except smell), and channels impulses to appropriate part of cerebral cortex for interpretation
Hypothalamus- Regulates autonomic activity involved in thermoregulation, hunger, thirst, sexual and mating behavior, etc… part of the limbic system (emotions)
The pituitary gland is attached to the hypothalamus

14. Cerebrum is the most highly evolved structure in the mammalian brain.
Functions: interpretation, initiating voluntary movements, storing memory, retrieving memory, reasoning, center for intelligence and personality
Corpus Callosum is the major connection between the two hemispheres.

15. Peripheral Nervous System
Responsible for communication btwn the CNS and the rest of the body.
Can be divided into:
Sensory Division
Afferent division
Conducts impulses from receptors to the CNS
Motor Division
Efferent division
Conducts impulses from CNS to effectors (muscles/glands)

16. Simple Nerve Path

17. Figure 48.3 The knee-jerk reflex

18. The nervous system of a vertebrate

19. Diversity in Nervous Systems

20. Figure 48.1 Overview of a vertebrate nervous system

22. Motor Efferent Division
Can be divided further:
Somatic Nervous System
VOLUNTARY (generally)
Somatic nerve fibers that conduct impulses from the CNS to skeletal muscles
Autonomic Nervous System
INVOLUNTARY (generally)
Conducts impulses from the CNS to smooth muscle, cardiac muscle, and glands.

23. Autonomic Nervous System

24. The main roles of the parasympathetic and sympathetic nerves in regulating internal body functions

25. Structure of a Vertebrate Neuron

26. Structural Diversity of Neurons

27. Neurons

28. Types of Neurons Sensory Neurons afferent; carry impulses to CNS
Interneurons link neurons in the CNS
Motor Neurons carry impulses away from CNS to effectors such as muscles and glands
SUPPORT CELLS Of Nervous System
Schwann Cells: peripheral nervous system—produce myelin sheath
Oligodendrocytes: CNS; myelinating cell
Astrocytes: CNS; form scar tissue, mop up excess ions, etc, induce synapse formation, connect neurons to blood vessels

29. Schwann Cells

30. Synaptic Transmission
An AP reaches the axon terminal of the presynaptic cell and causes V-gated Ca2+ channels to open.
Ca2+ rushes in, binds to regulatory proteins & initiates NT exocytosis.
NTs diffuse across the synaptic cleft and then bind to receptors on the postsynaptic membrane and initiate some sort of response on the postsynaptic cell.

32. A Chemical Synapse

33. The Major Known Neurotransmitters

35. Forces Behind Resting Potential
Selective Permeability- some molecules pass through membrane more freely than others; ion channels
Sodium-Potassium Pump transports 3 Na out of, 2 K into cell
Result:
Concentration Gradient
Electrical Gradient

36. The Basis of the Membrane Potential

38. Molecular Basis of Action Potential – transmission of a signal along an axon
Sodium channels open once threshold is reached, influx of sodium
Potassium channels open at AP peak; potassium flows out

39. Propagation of the Action Potential

44. Graded potentials and the action potential in a neuron

45. Generating an Impulse
polarized membrane: inside is negative relative to the outside under resting conditions due to distribution of ions controlled by Na+/K+ pump that require ATP
Nerve impulse starts when the membrane of the nerve depolarizes due to some stimulus, chemical, temp. changes, mechanical, etc….
Depolarization is caused by the influx of Na+ which causes the membrane to become more positive. This starts an action potential, or nerve impulse. They follow the all or none law!!!
The membrane will repolarize when K+ leaves the cell setting the membrane back to resting potential or polarized
This de and repolarization continues down the nerve until it reaches another nerve to pass on the impulse or until it reaches an effector.

46. The two hemispheres of the brain
are connected by the:
What was the substrate in yesterday’s lab? What was the product?

47. Last Review Questions for the Week:
What are the two components of the
CNS?
What type of response is processed
directly in the spinal cord with no
impulses traveling to the brain?

48. Which part of the neuron receives
impulses? carries them away?
What is the purpose of the myelin
sheath?

49. What is the minimum level of a stimulus required to activate a
neuron called?
What is meant by the term, “all-or-
none principle” with regards to the
conduction of nerve impulses?