1. Maintaining Dynamic Equilibrium
The Nervous System

2. Divisions of the Nervous System
Central Nervous System (CNS)
Brain
Spinal cord
Peripheral Nervous System (PNS)
Somatic
Autonomic

4. The Central Nervous System
The Brain
Spinal Cord
Neurons and supportive tissue
Spinal column

5. CNS Protection Skull-enclosing the brain Vertebrae- enclosing the spin
Meninges- 3 protective membranes that surrounds the brain and spinal cord.
Cerebrospinal fluid- Fluid that fills the spaces within the meninges to create a cushion.
Ventricles- cavities in the brain which are filled with cerebrospinal fluid.
                                 

7. Grey Matter- nerve tissue consisting of mainly cell bodies within the brain and spinal cord.
White Matter- nerve tissues of the brain and spinal cord, consisting of mostly myelinated neurons.

9. Peripheral Nervous System (PNS)

10. Peripheral Nervous System (PNS)
Input and output from the CNS.
2 types of nerves (numerous neurons held together)
Sensory nerves: From sensory receptors (skin, muscle, some internal organs)
Motor nerves: Carry orders to muscles,
glands & internal organs

12. Peripheral Nervous System-PNS
Somatic NS- Relays information to and form skin and skeletal muscles under your conscious control.
Autonomic NS- relays information to your internal organs not under your conscious control.
Sympathetic NS- controls organs in times of stress (fight or flight)
Parasympathetic NS- Controls organs when body is at rest.

13. Divisions of the PNS Divided into 2 parts:
Somatic nervous system (i.e. skeletal)
Voluntary actions
Autonomic nervous system
Non-voluntary actions
Regulation of Internal organs
Constriction of blood vessels
Regulates bladder, stomach and heart
Divided into 2 parts
Sympathetic
Fight or flight
Blushing, sweaty palms, heart racing
Parasympathetic
Relaxation
Slows things down to conserve energy

15. Neurons and Reflex Responses
Neurons are the structural and functional unit of the nervous system
Nerves are numerous neurons held together by connective tissues.

16. The Brain

17. The Cerebrum Divided into 2 hemispheres
Corpus callosum- is a bundle of nerve fibers connecting the left and right hemispheres

18. Cerebral Cortex The surface layer of grey tissue of the cerebrum
Folded to increase the surface area.
For Higher forms of thinking
Can be divided into 4 lobes.

19. The Four Lobes of the Cerebral Cortex
•Occipital lobe
Vision
•Parietal lobe
Somatosensory (the perception of sensory stimuli from the skin and internal organs)
Area associated with taste
•Temporal lobe
Auditory cortex/hearing
Wernicke’s area
(sensory speech, spoken language is understood)
•Frontal lobe
Strategic and effortful processing
Goal directed behaviours
Voluntary control
Motor cortex
Broca’s area (motor speech)

20. Cerebellum Motor and muscle coordination
Contains 50% of brains neurons but only takes up 10% of the space

21. Midbrain- a short segment of the brainstem
Involved in sight and hearing
Pons
contains bundles of axons traveling between the cerebellum and the rest of the CNS.
Medulla oblongata
Vital involuntary functions: heart rate, adjusting blood pressure, breathing, vomiting, hiccupping, swallowing.

22. Thalamus- Sensory relay station, governs the flow of information from all parts of the nervous system.
Hypothalamus- controls autonomic NS and endocrine hormone system, and reestablishes homeostasis.

23. The Neuron Neurons: the building blocks of the nervous system
Sensory neurons
send signals from the senses, skin, muscles, and internal organs to the CNS
Motor neurons
transmit commands from the CNS to the muscles, glands, and organs
Interneurons
Located between sensory and motor neurons
Most numerous type of neuron
Function: transmit signals from one part of the body to another

24. Reflex Responses

25. You drive a pin into your foot and immediately recoil from the shock and pain. Provide an explanation of what happens from the time the pin enters the skin to when you finally experience the pain. Your explanation should include any key components involved in the events and detail their role.
Reflect responses are carried out without assistance form the brain.

26. Neurons
Cell Body: has a large centrally located nucleolus. The cytoplasm contains mitochondria, lysosomes and Gogli complex.
Dendrites: are the primary site for receiving signals from other neurons. The number can range from one to thousands depending on the function.
Axon is a long cylindrical extension of the cell body. It transmits a pulse or wave of depolarization.
terminal branches (axon terminal) the end of the axon that branches off and comes in close contact with the dendrites of neighboring neurons

27. The Human Body: Nervous System

29. Schwann cells: insulating cells around the axons of some nerve cells in the PNS
Schwann cells make up a myelin sheath (fatty layer around the axon). Myelin speeds up nervous transmission
Node of Ranvier: the gap between Schwann cells around the axon of a nerve cell. The membrane of the axon is exposed and nerve impulses jump from one node of Ranvier to the next.

30. The All or None Response
if an axon is stimulated sufficiently (above the threshold), the axon will trigger an impulse down the length of the axon. If not, the impulse is not triggered.
It is analogous to firing a gun

31. Neurons

32. Spaces between neurons are synapses
Spaces between neurons are synapses. Axon terminals contain synaptic vesicles which hold neurotransmitters

34. Action Potentials in Neurons
At Rest (Polarization) → outside of neuron is positively charged compared to inside (sodium ions outside, chloride and potassium ions inside). At rest, the cell membrane is not permeable to sodium ions but very permeable to potassium ions so they diffuse out of the cells. However, a mechanism called the sodium/potassium pump (active transporter) pulls 3 sodium ions to the outside of the cell while pulling 2 potassium ions inside the cell

36. resting potential: the difference in charge from the inside to the outside of a cell at rest. It is approximately – 70 mV.

37. Depolarization→ when a neuron is stimulated enough, gates for potassium K+ ions channels (transporters) close and gates for sodium ion channels open. Na+ ions move in while K+ ions move out. More positive charges move in than out, and this neutralizes the negative charge inside the cell (actually makes the inside slightly positive). The resulting difference in charge during depolarization is called the action potential. Action potentials occur at cell bodies and dendrites as well.
depolarization at one point of the axon causes the neighboring Na+ channels to open, and the depolarization continues down the length of the axon

38. Repolarization→ after the Na+ channels open, K+ channels reopen to cause K+ to move out. At the same time, Na+ channels close.
the sodium/potassium pump restores the original concentrations of Na+ and K+ by pumping Na+ out and K+ in.

39. This entire process of depolarization and repolarization occurs very quickly. An axon can send many impulses along its length every second if it is sufficiently stimulated.

40. Refractory period: the brief time between the triggering of an impulse along an axon and the axon readiness for the next impulse. During that brief time, the axon cannot transmit an impulse. For many neurons, the refractory period is about s.

41. As mentioned earlier, myelinated neurons transmit impulses much quicker than unmyelinated ones. This is due to the fact that depolarization only occurs at the nodes of Ranvier. In a sense, the impulse jumps from node to node until it reaches the end of the neuron. Speeds of impulses on myelinated neurons can reach 120 m/s.

44. Action Potenital