1. CHAPTER 9: NERVOUS SYSTEM

2. 2 Main Divisions CNS - Central Nervous System  brain and spinal cord PNS - Peripheral Nervous System  all other nerves

3. Nerve Tissue 1. Neurons (nerve cell) - structural and functional cell of the nervous system - reacts to physical and chemical changes - neurons do not touch other neurons

4. cell body dendrites nucleus axon Schwann cell myelin Node of Ranvier

5. 2. Neuroglial cells 4 Types a) Astrocyte - connects neurons to blood vessels - provides support - remove cellular debris

6. b) Oligodendrocyte - arranged along nerve fibers - produces myelin c) Microglia - provide support - phagocytize bacteria d) Ependyma - covers part of the brain

7. astrocyte oligodendrocyte microglial cell ependymal cell

8. Types of Neurons and Nerves Classification 1. Multipolar neuron - only one axon, many dendrites - found only in brain and spinal cord dendrites axon

9. 2. Bipolar neuron - one dendrite, one axon - found in the eyes, nose, and ears dendrite axon 3. Unipolar neuron - 1 nerve fiber and then branches off axon dendrite - mass of these make up a ganglion - found outside the brain & spinal cord

10. Types of Nerves  A grouping of neurons 1. Sensory nerves - send impulses to the brain 2. Motor nerves - send impulses to muscles 3. Mixed nerves - contains both sensory & motor neurons

11. The Nerve Impulse  also called an Action Potential 1. Nerve cell gets excited 2. For a nerve impulse to get started, it must reach a threshold potential  minimal amt. of stimulus needed to start an impulse  summation - adding up of threshold stimuli

12. 3. Cell membrane permeability must be changed for a nerve impulse to travel down a neuron a) A cell is normally polarized - when a neuron is at rest - called it resting potential

13. b) A portion of the neuron becomes depolarized - Na + moves into the cell

14. c) Cell repolarization - K + moves out of the cell Nerve impulse - a nerve impulse is an all-or-none response - impulse will trigger or it won’t

15. Synapse - junction between 2 neurons - gap is called a synaptic cleft Synaptic Transmission - end of axon is synaptic knob which contains synaptic vesicles - these synaptic vesicles contain neurotransmitters

16. synaptic vesicle vesicle releasing neurotransmitter synaptic cleft synaptic knob Synaptic transmission

17. - After being released, neurotransmitters must be broken down to prevent continued stimulation - they are destroyed by: - cholinesterase - breaks down ACH - monoamine oxidase - breaks down monoamines

18. Types of Neurotransmitters 1. ACH - acetylcholine - used in skeletal muscle contractions 2. Monoamines - Norepinephrine – creates sense of “ feeling good”, too little - depression - Dopamine – creates a sense of “feeling good” – low amounts associated with Parkinson’s Disease - Serotonin – leads to sleepiness - Histamine – promotes alertness

19. 3. Neuropeptides - Substance P – pain perception - Endorphins – reduce pain

20. Nerve Pathways  the routes nerve impulses travel 1. Reflex arc sensory nerve impulse spinal cord interneuron motor nerve

21. Reflexes - automatic, unconscious responses to changes occurring within or outside the body - ex. knee jerk reflex - ex. withdrawl reflex

22. Coverings of the Central Nervous System - brain and spinal cord are protected by membranes called meninges 3 Layers a) dura mater - tough - attaches to the cranial cavity scalp skull dura mater

23. b) Arachnoid mater - subarachnoid space below contains cerebrospinal fluid arachnoid mater fluid c) pia mater - contains nerves and blood vessels pia mater

24. Spinal Cord Structure - 31 segments - each with a pair of spinal nerves - spinal nerve spinal nerve -

25. - central canal - central canal - contains CSF gray matter - - gray matter - mostly interneurons - white matter - white matter – comprised of the ascending and descending tracts

26. Functions - provides a 2-way communication system between brain and other body parts Ascending Tracts - carry sensory impulses to the brain Descending Tracts - carry motor impulses to muscle and glands

27. The Brain 3 Major Parts cerebrum cerebellum brain stem

29. Structure of the Cerebrum - 2 cerebral hemispheres - connected together by the corpus callosum - ridges are called convolutions or gyri - sulcus - shallow groove - fissure - deep groove

31. Lobes of the Cerebrum Insula - deep in brain Frontal Parietal Occipital Temporal

32. Functions of the Cerebrum Cerebral cortex - thin layer of gray matter that covers the cerebrum Areas of the Cortex 1. motor areas 2. sensory areas 3. association areas - memory, reasoning, judgment, & emotion - most people have a dominant hemisphere - left - more logical - right - more creative

33. The Diencephalon Thalamus - receives sensory impulses - sends them to appropriate areas of the brain Hypothalamus - important in homeostasis - secretes hormones

34. Limbic system - emotional experience or response Pineal gland - endocrine gland - involved in our daily biological clock

35. The Brain Stem  connects cerebrum to spinal cord 3 Parts 1. Midbrain - reflex center for the eyes and ears 2. Pons - place where the cranial nerves originate

36. 3. Medulla Oblongata - control center of various activities a. cardiac center b. vasomotor center c. respiratory center - contains the reticular formation - involved with activating the brain and waking up

37. The Cerebellum - consists of 2 hemispheres - divided by the vermis - cerebellar cortex is the outermost layer Functions 1. maintaining balance 2. coordinating motion

38. Peripheral Nervous System  everything but the brain & spinal cord Cranial Nerves - 12 pairs - originates in brain Spinal Nerves - 31 pairs - provide 2-way communication between spinal cord and parts of the body

39. The Autonomic Nervous System - part of the PNS - controls unconscious actions - heart beat - involuntary muscles - maintains homeostasis