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Ch 12-Nervous System 3% of your body weight. 2 divisions Central Nervous System (CNS)- Peripheral Nervous System (PNS)- Afferent- Efferent- 1. sensory.

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Presentation on theme: "Ch 12-Nervous System 3% of your body weight. 2 divisions Central Nervous System (CNS)- Peripheral Nervous System (PNS)- Afferent- Efferent- 1. sensory."— Presentation transcript:

1 Ch 12-Nervous System 3% of your body weight

2 2 divisions Central Nervous System (CNS)- Peripheral Nervous System (PNS)- Afferent- Efferent- 1. sensory receptors for senses, motor from skeletal 2. sensory for visceral, motor CNS to smooth & cardiac muscle & glands 1.Sympathethic- fight or flight 2.Parasympathetic- rest & digest

3 Nervous Tissue Neurons- react to physical & chemical changes send nerve impulses along nerve fibers Neuroglia-

4 Parts: Pg cell body- nucleus surrounded by cytoplasm, rough ER called Nissl bodies 2.dendrites- receiving portions of neurons, usually not myelinated 3.axon- moves nerve impulses toward another neuron, muscle fiber, or gland Others: -joins cell body at axon hillock -first part called initial segment -axoplasm- cytoplasm -axolemma- plasma membrane -axon collateral- branch & axon terminal- end -Trigger zone- initial segment meets axon hillock, where impulse arises

5 Synapse Presynaptic cell- Synaptic end bulb- tips of axon terminal contain synaptic vesicles that store neurotransmitters *Separated by synaptic cleft* Postsynaptic cell- If receiving cell is a: muscle = Gland =

6 Structural Classes of Neurons 1. Anaxonic- 2. Bipolar- Rare- in special sense organs for sight, smell, hearing small 3. Unipolar- Peripheral nervous system, long 4. Multipolar- Most common in CNS, control skeletal muscles, long

7 Functions 1.Sensory- -gather info if something changes & convert to impulses Interoceptors- systems (digestive, respiratory, cardiovascular) senses (deep pressure, pain) Exteroceptors- touch, temp, pressure, sight, smell, hearing Proprioceptors- 2. Integrate- - create sensation, memory, produce thoughts 3. Motor- effectors- response structures (muscles & glands) *SAME*

8 Myelination Myelin Sheath- -more myelin = -Neurolemma- -Internodes- -Nodes of Ranvier-

9 Conduction- how it travels 1.Continuous- 2.Saltatory-

10 Disorders of Myelin -all can lead to paralysis Chronic exposure to heavy-metals (lead, arsenic, mercury) leads to demyelination Diphtheria- from bacterial infection, toxin damages myelin, we have a vaccine Multiple Sclerosis- affects axons in the optic nerve, brain, & SC Loss of vision, problems with speech, balance, coordination Can be progressive, 30-40yrs of age, more in women Guillain-Barre Syndrome- autoimmune, demyelination of PNS Weakness & tingling > paralysis Triggered by virus Most fully recover Epilepsy- short, recurrent attacks of motor, sensory, or psychological malfunction MS- zxY TI

11 What’s the Matter? White Matter- Gray Matter- -cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia

12 Neuroglia- Nourishes neurons F(x):

13 Classification of Neuroglia of CNS 1.Astrocytes- 2. Oligodendrocytes- 3. Microglia- 4. Ependymal-

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15 Classification of Neuroglia of PNS 1.Schwann- 2.Satellite-

16 Neural Response to Injury Wallerian Degeneration- PNS 1. fragmentation of axon & myelin occurs in distal stump 2. Schwann cells form cord, grow into cut, & unite stumps Macrophages engulf debris 3. Axon sends buds into network of Schwann cells and then starts growing along cord of Schwann cells 4. Axon grows

17 CNS- more complicated More axons are likely involved Astrocytes produce scar tissue that can prevent growth Astrocytes release chemicals that block growth

18 How does a nerve impulse happen? Ion movements & electrical signals: All plasma membranes produce electrical signals by ion movement Transmembrane potential is particularly important to neurons Main membrane processes: 1.Resting Potential- Inside- Outside- 2.Graded potential- 3.Action potential- 4.Synaptic activity- 5.Information processing-

19 Electrochemical Gradients-

20 Membrane channels Passive/Leakage channels- Active/Gated channels- Chemically/Ligand gated- Ex: Ach receptors at neuromuscular junction Voltage gated- Mechanically gated-

21 Action potential when a nerve detects a change 1. Resting state- -Threshold- 2. Depolarizing phase- - makes more 3. Repolarizing phase- 4. Resting state *exception- can go from #1 to Hyperpolarized = more negative

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23 Refractory Period- All or None –

24 Neurotransmitters Excitatory- Inhibitory- 1.Acetylcholine (Ach)- skeletal muscles 2.Norepinephrine- consciousness & attention, body temp 3.Dopamine- emotions, addictions, pleasure, subconscious motor function 4.Serotonin- senses, temperature, mood (lack of=depression), appetite 5.Glutamate & Aspartate- memory, learning, excitatory 6.GABA- inhibitory, anti-anxiety

25 Neuromodulators Other chemicals released by synaptic terminals Similar in function to neurotransmitters Alter rate of neurotransmitter release or change post-synaptic cell’s response Opioids like endorphins-

26 Drugs & Addiction Drugs can release two to 10 times the amount of dopamine that natural rewards do, and they do it more quickly and more reliably brain responds by producing less dopamine naturally or eliminating dopamine receptors Alcohol: increases GABA & decreases glutamate=increase in dopamine Cocaine: inhibits removal of dopamine from synapses = “high” THC: stimulates release of dopamine = euphoria, drowsiness, appetite Ecstasy: targets serotonin receptors > mood

27 Parkinson’s Disease damage/degeneration of dopamine producing neurons Usually after 50, more in men, can be genetic Symptoms: Problems with balance and walking Rigid or stiff muscles Difficulty swallowing Drooling Slowed, quieter speech and monotone voice No expression in your face (like you are wearing a mask) Tremors


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